ICEAF VII - Book of Abstracts

100 79 Integrating sustainability into conceptual design of an aircraft structure for and beyond an eco-design approach Filippatos A1,2, Markatos D1 , Abhyankar K2 , Tzortzinis G2 , Gude M2 , Pantelakis S1 1Department of Mechanical Engineering and Aeronautics, University of Patras, 2 Institute of Lightweight Engineering and Polymer Technology, Technische Universitaet Dresden Sustainability reflects our current societal challenges, especially those related to climate change and resource scarcity, as a new disruptive driver during the design phase of components and structures. However, insufficient attention has been paid on the development of conceptual and basic design methods that consider sustainability aspects at the early stages of product development, with most of them focusing on the assessment and comparison of the ecological impact of design alternatives, e.g., the eco-design approach. In the present work, a novel design process is developed, addressing design-for-sustainability requirements, in which sustainability is understood as a quantifiable, multi-dimensional aggregated metric, associated with technological, economic, and ecological aspects/criteria, with the latter including also circularity aspects, linked to the whole lifecycle of the component. To this end, sustainability is considered as a function to be integrated into the early conceptual design phase, imposing new multidisciplinary optimization requirements and trade-offs between potentially contradicting decision criteria. To demonstrate the proposed approach, the impact of material selection on the sustainability of a typical aircraft component, demonstrating specific functional requirements is investigated. Virgin and recycled materials both metals as well as composites are provided as candidate materials while the spiral design approach is implemented in order to derive the design alternatives. The current model is coupled with a multi-criteria decision making (MCDM) -based methodology allowing for trade-offs between the decision criteria and consequently support decision-making in product design. The proposed approach shows a sound and practical cross-sectoral design engineering approach to integrating multi-criteria decision making to numerical modelling, by addressing design-for-sustainability requirements, aiming for and beyond eco-design. The decision-making capabilities of this approach are demonstrated and its capacity for providing early decision information to engineers during the conceptual and basic design phase is highlighted. Keywords Sustainable design; sustainability; design-for-sustainability; conceptual design; multi-criteria decision making (MCDM); eco-design

101 80 Modelling the shredding process of multi-material structures for recyclingoriented design Heibeck M1 , Richter J2 , Mütze T1 , Filippatos A3,2 1Helmholtz Institute Freiberg For Resource Technology, Helmholtz-Zentrum Dresden-Rossendorf, 2 Institute of Lightweight Engineering and Polymer Technology, TU Dresden, 3Department of Mechanical Engineering and Aeronautics, University of Patras A sustainable future requires a responsible handling of our material and energy resources. However, our modern products are becoming increasingly complex with respect to the material combinations and their linkages. While we engineer multi-material structures against failure for the use phase, we also need them to be dismantled in the end-of-life phase during recycling. This describes a main functional contradiction of the structure under the scope of a circular economy and sustainability. To achieve good material-specific recovery rates, materials locked in joints have to be liberated, which is typically achieved by breaking materials and joints in mechanical shredding processes. Unfortunately, no adequate models exist currently to describe these processes, which constitutes a missing link for a recyclingoriented design. The presented approach models the shredding of multi-material structures with adhesion joint through numerical simulations using the finite element method (FEM). For shredding, a rotary shear is employed as usual first process stage in recycling. A rotary shear consists of two counter-rotating shafts with discs and Vshaped teeth turning at a fixed speed (circumferential velocity at teeth <0.5 m/s) and exerting tensile stresses in conjunction with bending and torsion (tearing stresses) on specimens. An A-frame dummy specimen for lightweight automotive applications was used consisting of a sheet steel top-hat profile with a glass fibre-reinforced polyamide composite layer and polyamide rib structure glued to it. LS-DYNA software was used for explicit FE analysis as well as material models that consider the plasticity and failure of different materials and their interfaces. Furthermore, simulations were performed for different load cases, representing different orientations of the test specimen relative to the rotary shear as observed in experiments. A model evaluation workflow was developed in Python and R to quantify the shredding performance in terms of the metrics liberation degree, particle sizes and energy consumption. Simulation results show high qualitative and quantitative agreement regarding deformation, fracture and liberation phenomena observed in previous experiments, e.g., brittle breakage of polymers into many fragments, partial to full detachment of adhesion joint, as well as high degree of plastic deformation of steel that sometimes even clamped-in polymer material thus forming new form-locking joints. One highlight is the realistic estimation of the mechanical energy consumption required for shredding. However, mass losses occur due to element deletion at failure, which are observed with increasing element size of the mesh. In addition, the model underestimates the number of generated fragments especially in the small size range (< 5 mm). Better results are expected by incorporating strain-rate dependent material behaviour in the future. The developed simulation process could be integrated into a new design assistance tool for the conceptual design phase of multi-material structures with two main outcomes. First, to provide quantitative metrics linking the design and the failure behaviour during shredding of such structures, and consequently, to estimate the impact of design decisions on the recycling phase of a product enabling a recycling-oriented design. Keywords: Recycling; shredding; finite element simulation; multi-material design

102 81 Inspection and evaluation of corroded steel bridges with high resolution 3D laser scanning and convolutional neural networks (CNN) Tzortzinis G1,2, Filippatos A3 , Wittig J2 , Gude M2 , Ai C4 , Gerasimidis S4 1Dresden Center for Intelligent Materials (DCIM), Technische Universität Dresden, 2 Institute of Lightweight Engineering and Polymer Technology, Technische Universität Dresden, 3Machine Design Laboratory, Department of Mechanical Engineering & Aeronautics, University of Patras, 4Department of Civil and Environmental Engineering, University of Massachusetts Amherst Engineers face severe deterioration of existing transportation infrastructure, and they are called to evaluate the structural integrity of structures built several decades ago with minimal maintenance. For steel bridges, corrosion has historically been the main cause of deterioration, which most commonly appears accumulatively at the ends of beams eventually having a deleterious effect on the remaining lifetime of bridges. To assess the structural condition of corroded steel bridges, associated agencies require the identification and documentation of the phenomenon and the quantification of its effect to the structural integrity of the bridge. Conventional inspection techniques lack accurate measurements, and they report limited or insufficient data without which it is impossible to perform accurate load capacity estimations. Hence, it is common for engineers to fall back to being over-conservative, when it comes to bridge ratings, with the result of repeated lane or bridge closures, traffic delays, costly repairs and an immense economic impact. In this paper, we introduce a novel inspection and evaluation framework for steel bridge girders with corroded ends. In detail, a three-step procedure is proposed: I. In terms of inspection, laser scanning is used to capture the geometry of corroded steel girders using point clouds. II. For documentation, two-dimensional thickness contours are generated by post processing the obtained point clouds, capturing the uneven section loss and providing an overall description of the examined area. III. For capacity evaluation, a tool based on CNN classifiers is proposed. The training dataset consists of approximately 1400 artificially generated thickness contour maps and their associated bearing capacities. The corrosion scenarios are generated by parameterizing real point cloud data, while failure loads are calculated with finite element models which are validated by full-scale experimental testing of a beam with natural corrosion. The proposed framework addresses the measurement shortcoming and provides informative contour maps easily processed from inspectors and engineers. The CNN classifiers achieve up to 98% accuracy providing credibility to the developed methodology. Keywords Corrosion, bridges, inspection, evaluation, convolutional neural networks, 3D laser scanning

103 82 Ice detection on composite blades using artificial neural networks under different icing conditions based on their vibration behavior Wittig J1 , Tzortzinis G1,2, Filippatos A3,1 1 Institute of Lightweight Engineering and Polymer Technology, Technische Universität Dresden, 2Dresden Center for Intelligent Materials (DCIM), Technische Universität Dresden, 3Machine Design Laboratory, Department of Mechanical Engineering & Aeronautics, University of Patras With a share of 90% [1], wind and solar are the most widely used renewable energy sources nowadays. Wind farms are located all over the world, including in cold climate regions, where they are subjected to harsh environments with low temperatures and icing. Icing has a significant impact on both the performance and structural integrity of wind turbines. Ice accumulation on the blades reduces their aerodynamic performance and can also cause vibrations with a high risk of damaging vital components, e.g., the blades, gearbox and bearings. Consequently, operators may be forced to shut down wind turbines in an attempt to mitigate the dangerous effects of ice build-up. The need for an accurate ice detection and monitoring system becomes prominent to prevent potential damage and associated costs. Previous studies have examined various techniques for detecting ice on blades. However, for both onshore and offshore installations, most of them fail to accurately predict the ice distribution along the blades to assess the icing state. The present study aims to create a tool for accurate ice predictions and quantifications on blades, combining artificial neural networks and small-scale experiments. In the experimental phase, manufactured glass fiber-reinforced plastic blades are equipped with macro fiber composite actuators for inducing vibrations and accelerometers for measuring the resulting response. Different ice configurations are generated by controlling the operation of three nozzles within a test rig housed in a controlled climate chamber. The icing experiments are carried out with different icing distributions at temperatures ranging from −10 ◦C to −20 ◦C. For each prediction target of ice thickness along the blade, ice volume and ice mass, one artificial neural network is trained. By conducting optimizations for the artificial neural networks, optimal sets of hyperparameters are obtained to enhance the prediction performances. Based on the blade’s frequency response as input data, the artificial neural networks are able to predict the targets with high performance, enabling an accurate prediction of the icing state on the wind turbine blade. In conclusion, the application of predictions with artificial neural networks of ice accumulation based on the frequency response is successfully demonstrated with high performance, which can be deployed to monitor icing on blades and prevent potential ice-induced damage. References [1] Darwish, Abdul Salam and Al-Dabbagh, Riadh. “Wind energy state of the art: present and future technology advancements”. In: Renew. Energy Environ. Sustain. 5 (2020)

104 83 Experimental Study of Composite Driveshafts for Marine Applications Bilalis E1 , Tzortzinis G, Tsouvalis N, Filippatos A 1National Technical University Of Athens Composite materials driveshafts are increasingly becoming the engineers’ choice for a large number of high performance and heavy duty power transmission applications, due to their light weight and high strength. Especially for the marine sector, apart from their high strength and light weight, composite driveshafts offer the advantages of high fatigue and corrosion resistance. Glass Fiber Reinforced Polymer (GFRP) and Carbon Fiber Reinforced Polymer (CFRP) composite driveshafts have the potential to be 25-80% lighter than the conventional steel shafts of similar specifications. A composite driveshaft also suppresses the transmission of noise from machinery and propellers, due to the intrinsic damping properties of composite materials. Being non-magnetic, composite shafts will also reduce the magnetic signature of a vessel, which is important in naval warfare applications. Additionally, composite shafts offer the advantages of low bearing loads, or even elimination of bearings, due to their light weight, and of greater flexibility and improved lifecycle cost. In the context of the present work, three CFRP driveshafts are manufactured with the filament winding technique and are then subjected to Non-Destructive Tests (NDTs) for the assessment of their manufacturing quality and the unveiling of any manufacturing imperfections. This is achieved through stereoscopic scans for the assessment of the geometric quality and Computer Tomography (CT) scans at mid-length and at the area of the connection of the steel flanges, for the assessment of the through thickness quality of the composite, as well as the quality of the bond between the composite shaft and the steel flanges. Furthermore, experimental modal analysis is conducted for the estimation of the eigenfrequencies and mode shapes of the driveshafts. The experimental campaign concludes with static torsional testing of the driveshafts, in order to assess their torsional stiffness, failure load and failure mode. The torsional stiffness is assessed through the measurement of the applied torque and the angle of rotation of the free end of the shaft, measured both by the goniometer of the torsion machine and the applied Digital Image Correlation (DIC) system. On the other hand, the failure mode is investigated through the combined assessment of the torque-angle curve and the measurement of strains on the shaft utilizing DIC, as well as strain gages placed on several selected positions on the outer surface of the shaft. The experimental results show good repeatability and indicate the high manufacturing quality and precision of the driveshafts. Thus, the capabilities of the filament winding manufacturing technique and the high-level production standards of the manufacturer are highlighted. The combination of the experimental results and the applied measuring and monitoring systems with highfidelity finite element models constitutes the basis of the development of a simulation driven physical model-based Structural Digital Twin of composite materials driveshafts for marine applications.

105 Torque - Angle of Rotation diagram of the three driveshafts tested. Keywords: Composite Materials Driveshafts, Mechanical Testing, Experimental Modal Analysis, Carbon Fiber Reinforced Polymer (CFRP), Marine

106 Fracture of materials and structures, and failure analysis (Abstracts 84-162)

107 84 Hydrocode numerical modeling of projectile impact on moving aluminum targets Kalfountzos C1 , Bikakis G1 , Theotokoglou E1 1Department of Mechanics, Laboratory of Testing and Materials, School of Applied Mathematical and Physical Sciences, National Technical University of Athens The study of impact properties is critical for aerospace structures, since they are often subjected to impact damage. Ballistic impact experiments with stationary targets are generally expensive and time-consuming. The motion of the target increases the complexity of the experimental arrangement and makes the experimental investigation even more expensive and difficult. Furthermore, although the scientific research of impact performance of aerospace materials with stationary target specimens is extensive, the theoretical research of impact on moving targets is rather limited and relevant published experimental research is rare. These facts indicate the necessity and increase the value of carrying out a theoretical study concerning projectile impact on moving targets. This paper deals with high velocity normal impacts of a rigid projectile on moving aluminum plates supported with mixed boundary conditions which permit their rigid body motion in the plane perpendicular to the striker’s trajectory with a predetermined initial velocity. A 3D numerical modeling procedure based on the finite difference method is implemented for this problem with the ANSYS-AUTODYN hydrocode [1]. The plate and the projectile are discretized with Lagrangian grids consisting of hexahedral eight-noded volume elements (cells). The convergence of the numerical results is always verified by increasing the grid density. It is also verified that the numerical results satisfy the momentum and energy conservation laws. Low hourglass energy is achieved for each numerical solution. The numerical modeling procedure is validated through suitable comparisons with experimental data concerning stationary targets [2]. The principal results presented in this study are the energy time-histories of the striker-target system, the projectile trajectories and velocity contours of the system (Figure 1). It is found that for relatively higher values of projectile velocity its trajectory remains approximately normal after the perforation of the plate, whereas for lower projectile velocities the moving plate changes the projectile trajectory. The hole of the plate due to projectile perforation is approximately elliptical and its area increases as the velocity of the plate is increased. It is found that the impact energy absorbed by the plate can be substantially affected by its velocity. The internal energy of the plate depends mainly on the plastic work. As the plate’s velocity increases the distance between the curves of plastic work and internal energy time-histories is reduced. The two curves practically coincide for high plate velocities.

108 Absolute velocity contours of an aluminum plate impacted by a projectile before (a) and during (b) impact. Initially, the plate and projectile have only X- and Z-component of velocity, respectively References 1. ANSYS Documentation, AUTODYN User’s Manual, ANSYS Inc. 2015. 2. Fatt MSH, Lin C, et al. Ballistic impact of GLARETM fiber-metal laminates. Composite Structures 2003; 61; 73-88.

109 85 The anisotropy behavior of metallic foams under Charpy impact tests Galatanu S1 , Linul E1 , Kováčik J2 , Marsavina L1,3 1Universitatea Politehnica Timisoara, 2 Institute of Materials and Machine Mechanics, Slovak Academy of Sciences, 3Romanian Academy, Timisoara Branch Currently, the automotive industry is looking for their new products to have a density as low as possible so that CO2 emissions decrease. Metallic foams have attracted a great deal of interest in this industry because of their multiple advantages. They can be produced at a relatively low cost and have advantageous properties, especially due to their stiffness and absorbed energy. In the framework of this study, 42 specimens were tested to determine the impact energy and Charpy impact strength according to the cutting orientation. The specimens were waterjet cut at different orientations (0, 15, 30, 45, 60, 75, and 90 degrees) from a metal foam plate based on aluminum alloy. They were subsequently rectified to bring them to their final dimensions. Before being notched according to the ISO 148 standard, their specific mass was determined. The Instron CEAST 9050 Charpy test machine was used to determine the impact behavior of the metallic foam specimens. The recorded force signal measurements by the machine were forwarded to the equipment computer software through a data acquisition system connected to the hammer. The pendulum is raised to a defined height and released to fall. The difference between the initial and final heights of the pendulum is directly proportional to the amount of energy lost as a result of the fracturing of the specimen. The impact strength was determined according to the cutting orientation, and the results obtained by the mass density groups were compared. Using an electronic microscope Leica DM6M, the topology of the fracture area of the specimens was investigated. It could be observed that the cutting orientation of the specimens does not have a clear influence on the impact strength; this is due to the irregular shape of the open cells, however, the grouping of the specimens on specific density samples have influenced in the impact strength.

110 86 Understanding the crack initiation mechanism under thermal-mechanical fatigue in polycrystalline superalloys Collins D2 , Segersäll M3 , Moverare J3 , Wilkinson A4 , Gault B5 , Kontis P1,5 1Norwegian University Of Science And Technology, Department of Materials Science and Engineering, 2 School of Metallurgy and Materials, University of Birmingham, 3Engineering Materials, Department of Management and Engineering, Linköping University, 4Department of Materials, University of Oxford, 5Max-Planck-Institut für Eisenforschung Carbon is traditionally added in polycrystalline nickel-based superalloys used for high-temperature applications, such as in aero-engines or land-based turbines. This minor solute, along others such as boron and zirconium, can have a tremendous effect on improving the mechanical performance of these alloys, in particular creep performance. The presence of carbon in the bulk chemistry of superalloys often leads to the formation of inter- and intragranular carbides in the microstructure. Although carbides are often believed to be beneficial to high temperature mechanical performance, our study shows that oxidation of carbides, such as MC carbides, can lead to crack initiation during thermal-mechanical fatigue (TMF) conditions at 750 and 850 °C. Microstructural observations on the fracture surface of TMF tested superalloys are compared with those from bulk samples exposed isothermally at 750 and 850 °C, in the absence of any external load. Scanning electron microscopy (SEM) and strain mapping from electron backscatter diffraction shows local deformation and recrystallization in the vicinity of the oxidized carbides. Electron channeling contrast imaging (ECCI) further confirms the local deformation by revealing a high dislocation density around oxidized carbides. Finally, atom probe tomography (APT) provides 3D compositional information down at the atomic scale. In particular, segregation of solutes at dislocations is shown that allows the rationalization of the recrystallization mechanism. Besides, chemical inhomogeneities related to the dislocation density are measured by APT and they are correlated to the oxidation of the carbides. These findings together provide new insights into the fracture mechanism under TMF conditions from oxidized carbides in polycrystalline superalloys.

111 87 Wear Behavior of SBR/BR Compounds Including Different ZnO Types Börüban Biṅ göl C 1 , Polat Ş2 , Atapek Ş2 1Brisa Bridgestone Turkey, 2Kocaeli University Zinc complexes have considerable impact on human health and environment especially on aquatic wildlife. One of the main sources of zinc release to the environment is worn rubber particles from tires. Environmental footprint of zinc oxide during production, ecological and economical concerns have prompted the researchers to reduce its use in rubber formulations. The wear behavior of SBR/BR compounds including different ZnO types (white seal ZnO, active ZnO and composite ZnO materials having ZnO:CaCO3 ratio as 40:60, 60:40 and 90:10) is studied at room temperature using Ueshima Lambourn AB-2010 instrument according to ISO23337:2007 method. Following the tests, the mass losses in the compounds are measured and linear wear rates are calculated. The findings have revealed that (i) composite ZnO materials having lower wear rates exhibit better wear resistance compared to white seal ZnO and active ZnO, (ii) as ZnO level increases in composite materials, wear resistance is enhanced.

112 88 Experimental and Computational study of Microhardness Evolution in the HAZ for Al-Cu-Li alloys Maritsa S1 , Zervaki A1 1 Shipbuilding Technology Laboratory, School of Naval Architecture and Marine Engineering, National Technical University of Athens Laser Beam Welding (LBW) of aluminum alloys has attracted significant interest from industrial sectors including the shipbuilding, automotive and aeronautics industry, as it expects to contribute to significant costs reduction associated with the production of high-quality welds. To comprehend the behavior of welded structures in regards to their damage tolerance, the application of fracture mechanics serves as the instrumental tool. However, the methods employed overlook the changes in the microstructure within the Heat-Affected Zone (HAZ), which lead to degradation of the mechanical properties of the material. The purpose of this study is to simulate microhardness evolution in the Heat Affected Zone (HAZ) of AA2198- T351 LBW. The material represents the latest generation of Al-Cu-Li alloys, which exhibit improved mechanical properties, enhanced damage tolerance behavior, lower density and better corrosion and fatigue crack growth resistance when compared to conventional Al-Cu alloys. In this work, the microhardness profile of LBW AA2198 was measured and subsequently, through isothermal heat treatments on samples the microhardness values of the HAZ were replicated. The conditions of the heat treatments (T, t) were selected in line with the thermal cycles that each area of the HAZ experienced during welding. ThermoCalc and DICTRA were employed in order to identify the strengthening precipitates and their evolution (dissolution and coarsening) during the weld thermal cycle. The microstructure of the heat-treated samples was studied by using OM, SEM and TEM, and the strengthening precipitates and their characteristics (volume fraction and size) were defined and correlated to the calculations and the experimental conditions employed during welding. The main conclusion of this study is that it is feasible to imitate the microstructure evolution within the HAZ through the implementation of isothermal heat treatments. This implies that it is possible to fabricate samples for fatigue crack growth tests, enabling the experimental examination of the damage tolerance behavior in welded structures.

113 89 Pressure equipment in refineries: Correlation of process conditions with life span under the existence of welding defects Fotiadis A1 , Oikonomou D1 , Zervaki A2 , Haidemenopoulos G3 1Hellenic Petroleum SA, 2NTUA, 3University of Thessaly Welding failures in pressurized equipment is the most common reason for equipment’s and associated production's unit sudden shut down. In this context the root cause analysis of the relevant failure incidence is essential as it provides important information regarding the failure mechanism and indicates proper mitigation measures. In the current work, three different failure cases are analyzed, while the life span of each pressure equipment is correlated to existing welding defects and process conditions. The shell of a heat exchanger, made of CS Grade SA 516 Gr. 70, failed due to the formation of a crack at one of its longitudinal welds. The crack initiated at the boundary of the Heat Affected Zone(HAZ) and the Base Metal (BM). Process conditions along with residual stresses from the weld process, accelerated the crack propagation. Linear defects were detected at the mid thickness of the welds of a pressure vessel which failed in service. The formation of these defects were associated to improper weld procedure during vessel fabrication. During the repair work, it was found that the linear defects were slag lines formed because of the improper welding procedure during vessel’s construction phase. A 10΄΄ stainless steel pipe, made of stainless steel 321, failed due to the formation of a crack, which originated at the outer surface and propagated through thickness towards the inner surface. It was revealed that the origin of the crack was due to manufacturing defects which were not observed during the construction of the pipeline even though they were visible. All cases indicate that welding defects along with process conditions significantly contribute to the reduction of the expected lifespan of pressure equipment in refineries.

114 90 Contribution of texture analysis on the formability examination of 6061 Al alloy for the automotive industry Aslanis P1 , Symeonidis G2 , Papadopoulou S1 , Rikos A1 , Stachouli E, Vazdirvanidis A1 1ELKEME SA, 2ETEM-GESTSAMP The role of texture analysis in the investigation of formability related projects has significantly increased in the last years. In the current research a 6061 Al alloy extruded profile is examined by Electron Backscatter Diffraction (EBSD) for determination of the texture across thickness as this plays a significant role in cracking initiation during three-point bend testing. Taylor factor maps are constructed for revealing sensitized regions due to different grains rotation during the application of tensile stresses. Correlation of grain boundary misorientation by categorization to high angle grain boundaries (HAGBs), low angle grain boundaries (LAGBs) and sub-grain boundaries (SGBs) with Mg2Si precipitation behavior is also highlighted. Results showed that examination of texture is beneficial for the optimization of crashworthiness and manufacturing of robust automotive part.

115 91 Microstructural characterization of dissimilar welding and repair welding between super-austenitic and austenitic stainless steels, using different filler materials Varouti E1 , Zervas A1 , Iakovidis I2 , Chionopoulos S2 1PPC Innovation Hub, Metallography laboratory, 2Department of Naval Architecture, School of Engineering, University of West Attica Dissimilar fusion welding of metallic alloys is always a challenge. Different materials with different mechanical and physical properties are joined together, while an extra consideration on the choice of the right filler material is involved. Repair procedures for these welds, additionally, increase the requirements, regarding their metallurgical characteristics, associated with different failure or corrosion mechanisms. The present work focuses on the microstructural characterization of dissimilar welds and repair welds between, a super-austenitic, type 254 SMO®, and an austenitic, type 316L stainless steel, using two different filler materials. Plates of 5 mm thickness were arc welded using Tungsten Inert Gas (TIG) technique. Filler materials applied were nickel-based, of type ERNiCrMo-3 (NiCr22Mo9Nb), and stainless steel, of type ER316L. In all welds, the joint design was single-V, the welding was performed on both sides and the heat input was kept under 1,5 kJ/mm. In the completed welds, a groove 2,5 mm depth to 3,5 mm width was opened, by mechanical means, simulating the removal of material during a repair welding procedure. The groove filled with the two filler materials, creating different sets of repair welding procedures. Fully metallographic analysis on all different welds was performed, including stereoscopic observation of the geometry of the weld beads, Vickers microhardness tests, as well as, microstructural characterization, using optical microscopy, supported with image analysis software and Scanning Electron Microscopy (SEM), coupled with Energy Dispersive Spectroscopy (EDS). The study revealed the influence of the different processes (dissimilar welding and dissimilar repair welding) and of the different filler materials, on the microstructure of the welding areas (both weld metal and heataffected zone), concerning the development of the different phases, sizes, and type of growth of the grains and the microhardness. Nickel-based filler material gave better microstructural characteristics in all cases. Repair welding procedures significantly affected grain morphology and the tendency to develop microstructure susceptible to different failure or corrosion mechanisms. Keywords: 254 SMO® Super austenitic stainless steel, AISI 316L austenitic stainless steel, dissimilar welding, TIG welding, repair welding, microstructure. References

116 [1] Roshith P., Arivarasu M., Arivazhagan N., Srinivasan A., Phani Prabhakar K. V., Journal of Manufacturing Processes 44 (2019) 81–90 [2] Köse C., Vacuum 205 (2022) 111440 [3] Köse C., Topal C., Journal of Manufacturing Processes 73 (2022) 861–894 [4] Ramkumar Varma D. K., J. L. N., Choudhary G. C., A., Arivazhagan N., Narayanan S., Materials Science & Engineering A 636 (2015) 1–9

117 92 3D Crack Propagation Study of a Railway Component using XFEM Method Morgado T1,2,3,4, Dias R1 , Pereira M5 1UNIDEMI - Research & Development Unit in Mechanical and Industrial Engineering, Department of Mechanical and Industrial Engineering, FCT NOVA - Faculty of Science and Technology, Universidade Nova de Lisboa,, 2 ISEL - Lisbon School of Engineering of Polytechnic Institute of Lisbon, Portugal, 3 Intelligent Systems Associate Laboratory, 4CINAV - Navy Research Center, 5CERENA/CEPGIST - IST - Centro de Recursos Naturais e Ambiente, DECivil, Instituto Superior Técnico, University of Lisbon Evaluating the structural integrity and durability of mechanical components is fundamental in the railway industry. Parameters such as service loads, material properties, stress ratio, hardness, intrinsic manufacturing defects, manufacturing process, heat treatment of the material and piece geometry must be considered at the design stage to define the component lifetime. This work develops a methodology to study the crack propagation of a railway component through ABAQUS simulation. This simulation study uses the service condition of the mechanical component (service loads, frontier conditions, material and geometric dimensions). It is also considered the complex geometry of a manufacturing defect obtained by microtomography. It was concluded that the XFEM method is an essential tool in predicting possible crack propagation of a railway component. Furthermore, the type of criteria used in the XFEM method allowed the analysis of the propensity of the manufacturing defect to initiate crack propagation. The C3D4 elements played an essential role in realising the crack propagation simulation, considering a manufacturing defect. Having the pore's complex geometry was crucial to developing the methodology presented in this study. The static analysis results indicated that the maximum stress concentration value in the pore is located in a zone that can be identified as a hot spot. In addition, the pore showed a higher concentration of Von-Mises stresses than in the static simulation performed without a pore and of the material's ultimate strength. In conclusion, the methodology presented in this work shows that developing a more realistic simulation study is possible. For a complete structural integrity study, the mechanical design simulation studies must include some complex geometries of intrinsic manufacturing defects.

118 93 The role of intermetallic particles and grain boundaries at various mechanical orientations in AA 7075 aluminum alloy Prospathopoulos A1 , Argyros A1 , Gakias C1 , Savvaidis G1, Michailidis N1,2 1 Physical Metallurgy Laboratory, Dept. of Mechanical Engineering, School of Engineering, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece 2 Centre for Research & Development of Advanced Materials (CERDAM), Center for Interdisciplinary Research and Innovation, Balkan Centre, Building B’, 10th km Thessaloniki-Thermi Road, 57001, Thessaloniki, Greece 3 Machine Elements and Mechanical Design Laboratory (ESMMS), School of Engineering, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece The aluminum alloys of the 7XXX series have zing, magnesium and copper as main elements. Due to the exceptional properties like high tensile strength, long fatigue life etc. are being used as structural parts in transportation and aircraft industries. All the mechanical stresses or vibrations generated during the flight of an airplane give rise to the material fatigue leading to the nucleation of cracks mainly at inclusions, constituent particles or even at precipitates and thus one or more cracks, propagate until material fracture. Therefore, it is of utmost importance to understand the fatigue behavior of these alloys. The role of microstructural features like the grain size, grain orientation and precipitates, etc. in the fatigue life of high-strength cold-rolled aluminum alloy AA7075-T6 was investigated. Three-point bending tests have been performed (R=0), followed by statistical data processing and S-N curves that were extracted to point out which orientation relative to the cross-section presents better fatigue performance. Stereo, optical and scanning electron microscopy analyses were performed to reveal that crack initiation was caused by either voids, intermetallics, or dispersoid particles, even though the same particles play in other cases the role of crack growth inhibitors. All samples were cut and surface ground to avoid unwanted crack initiations that start from notches and geometrical irregularities that are created by the rolling process. Moreover, analytical model has been developed to verify and evaluate and explain the fatigue behavior in different orientations. The theoretical fatigue behavior was compared to the experimental results showing good convergence. Keywords: ΑΑ7075-T6 Aluminum alloy, Fatigue behavior, S-N curves, rolling direction.

119 94 Properties of the crack resistance of layered composite and simulation of a crack quasi-static growth Pavelko V1 1Riga Technical University The outcomes of standard test of a carbon/epoxy layered composite using DCB specimen for measuring of the I-mode interlaminar fracture toughness were analyzed. It is known that at loading with control of displacement, the process of delamination growth theoretically should be stable. However, for given material the jump-type growing of delamination is observed: each stage of stable crack growth alternates with follow stage of fast unstable increase of its size. Such behavior is considered here as caused by the statistical non-homogeneity of interlaminar crack resistance of material. There are obtained statistical estimates of the maximum crack resistance and of the crack arrest. The improved model of the crack quasi-static growth (CQSG) is used for the analysis of properties of interlaminar crack resistance of tested composite [1]. Some regularities of unstable stage of crack growth are investigated. The statistical estimates of mean rate of unstable crack propagation are obtained and the close correlation between this rate and difference of maximum interlaminar fracture toughness and its value at crack arrest is shown. The CQSG model is applied also for search of alternative versions of description of interlaminar crack resistance. In contrast to the saw-type description of variable interlaminar fracture toughness here the piece-constant version of this characteristics is analysed, and some advantages of this description are showed. The corresponding crack resistance function (R-curve) also is simulated. References [1] Pavelko, V. Analysis of the Crack Resistance of Layered Composite Using the Model of Quasi-Static Crack Growth (in print). AIP Conference Proceedings 2022

120 95 Quasi-static and fatigue crack growth simulation in co-consolidated thermoplastic joints containing crack arrest features Sioutis I1 , Tserpes K1 , Papanikos P2 1 Laboratory of Technology and Strength of Materials, Department of Mechanical Engineering & Aeronautics, University of Patras, 2Department of Product and Systems Design Engineering, University of the Aegean In the present article, quasi-static and fatigue crack growth simulation in co-consolidated thermoplastic crack lap shear specimens containing two different crack arrest features (CAF) has been simulated. The substrates were made from the unidirectional T700 carbon fiber reinforced Low-Melt PAEK thermoplastic material. The studied CAF are the Friction Stir Spot Welds (RFSSW) and the Induction Low Stir Friction Rivets (ILSFSR). Simulation has been performed by means of a mixed-mode fatigue crack growth model developed previously by the authors. Implementation was made in the LS-Dyna software. Both static and fatigue crack growth models have been successfully validated against results from respective mechanical tests. Both CAF have been proven capable of delaying the crack growth, especially for the fatigue loading. An evaluation of various installation parameters of the two features, such as the diameter, the distance to the crack-tip and the installation depth, has been performed for the quasi-static loading cases. All parameters have been found to affect the crack stopping efficiency, but the most important effect comes from the diameter of the CAF. The developed models can be used for the design of CAF pattern in larger thermoplastic parts such as thermoplastic stiffened panels with co-consolidated stringers.

121 96 A structural-thermal coupled modeling approach on the formation of adiabatic shear bands in steel sheet blanking process Karantza K1 , Vaxevanidis N2 , Manolakos D1 1National Technical University Of Athens (NTUA), 2 School of Pedagogical and Technological Education (ASPETE) The continuous need of improving the productivity and the efficiency of material processing technology has focused the research interest on studying the causes which lead to material defects. In many occasions, plastic deformation instabilities have been determined as the main responsible mechanisms resulting often in material failure and affecting so both geometry and mechanical properties of the final product. In specific, adiabatic shear banding is a widely met failure mechanism reflecting from intense shear localization along narrow bands and is observed in high strain rates representing adiabatic loading conditions under which the dissipated plastic deformation energy is transformed into internal heat leading to thermal softening. For this reason, adiabatic shear bands (ASBs) constitute a catastrophic shear instability mechanism which result in material failure through rapid crack propagation. This study presents a numerical investigation on the genesis of shear bands in adiabatic blanking process of steel sheets aiming to highlight the macroscopic phenomena which lead to ASBs’ formation, cracking initiation and propagation. A structural-thermal coupled finite element (FE) model is developed in LS-DYNA in order to simulate the blanking process of AISI 4340 steel sheet of 4 mm thickness. A variable density Lagrangian FE meshing is generated until 60 μm sizing in the ASB expected region in order to capture sufficiently the formation of narrow shear zones, while material structural modeling utilizes Johnson-Cook formula which provides a thermo-viscoplastic material behavior through plastic deformation implementing further a damage model for cracking initiation and propagation. In order to account for thermal softening effect which facilitates micro-voiding formation and cracking growth along ASB, a structural-thermal coupling is implemented through FE modeling assuming an isotropic thermal behavior for steel sheet and a 0.9 Taylor-Quinney coefficient for the fraction of deformation energy which is transformed to internal heat due to adiabatic loading. The simulation results indicated an intense initial shear localization around punch and die corners which led to the formation of a 138 μm wide S-shaped ASB along sheet thickness and punch-die clearance (0.25 mm) as Figure 1 depicts. The ASB region was reflected from severe shear strain (Figure 2a) and thus deformation energy concentration which resulted in a high temperature narrow zone (Figure 2b) reaching 723 K around punch-die corners and overcoming so dynamic recrystallization (DRX) temperature. At next, micro-voiding was occurred inside high temperature regions of ASB reflecting cracking initiation at punch penetration around 43% of sheet thickness where the blanking force started to drop due to deformation instability. As the punch penetration was increased the effect of thermal softening expanded along ASB causing cracking propagation from punch-die corners to internal ASB region revealing a sharper force decrease. Final fracture was observed at punch displacement around 68% of sheet thickness showing a 0.3 mm rollover length, 1.7 mm shear-zone length and about 2 mm fractured zone in the blanked surface.

122 Shear strain (a) and temperature (b) fields for different punch displacements Effective plastic strain (a) and temperature (b) distribution with transverse distance from ASB at cracking initiation timing

123 97 Eliciting stable nanoscale fracture in single-crystal silicon DelRio F1 , Grutzik S1 , Mook W1 , Dickens S1 , Kotula P1 , Hintsala E2 , Stauffer D2 , Warren O2 , Boyce B1 1 Sandia National Laboratories, 2Bruker Corporation As the density of interconnects, bumps, pads, and vias increases, and the wafer thickness decreases, fracture at the microscale becomes increasingly more important. There have been several studies that allow for crack introduction and propagation and arrest, but few have been able to provide stable crack growth with arrests for a single sharp crack. Here we demonstrate that stable fracture can be performed in singlecrystal silicon using an in-situ wedge-loaded double cantilever beam specimen. A KIC value can be calculated by using the force and displacement measured by the in-situ micromechanical system (Bruker’s PI 89) and corrections for frictional forces performed by FEA. Multiple specimens were tested, with KIC values of 0.72±0.07 MPa√m measured for cracks propagating on the {111}. Cracks arrested after approximately 500nm of propagation. The use of an in-situ tool that allows for precise placement of the wedge, along with force and displacement measurement, and inherent displacement actuation, allows for observation of fracture processes in a methodology that is both novel and repeatable. SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525. DCB specimen with aligned wedge. Each crack propagation is accompanied by a load drop, then an arrest. Measurable crack growth in brittle specimens is the goal.

124 98 Construction of prior models used within Bayesian schemes for fatigue crack growth SHM in marine structures Silionis N1 , Makris P1 , Anyfantis K1 1NTUA, National Technical University of Athens Objective: It is highly probable that any new or existing ship hull will encounter a considerable amount of fatigue cracks during its lifetime. Although there is a positive statistical correlation between the vessel’s age and the number of identified cracks, there have been cases reported where cracks are observed within the first year after commissioning. Current survey and repair plans, that are based on preventive maintenance, do not guarantee the identification of cracks which appear at the early life of the ship or between surveys (older ships), having hence a significant impact on the total life-cycle cost. The field of Structural Health Monitoring (SHM) provides a viable solution that promises the optimization of the survey and repair plan tailored to the actual state of the individual ship. SHM is founded on diagnostics and prognostics. Fatigue crack growth is a stochastic process as there is a significant amount of uncertainty associated with the involved basic variables and therefore probabilistic methods must be employed. Transformation of sensor readings received at a certain time, τ, to the current state of a crack length, α, (diagnostics) and estimation of the remaining useful life, Τ, (prognostics) may be both framed in an inverse Bayesian setting. Uncertainty quantification within the construction process of prior probabilistic models is of major importance in Bayesian inferential statistics. The objective of this work is to investigate the effect of the probabilistic description of the basic random variables (RV) that control the fatigue crack growth process to the construction of the prior distributions. Methods: Selecting a uniform distribution for the probabilistic model of the parameters that are of inferential interest would suggest a non-informative prior selection which adds epistemic uncertainty to the problem at hand. Paris-Erdogan crack growth predictive model may well be used within the construction process of informative priors that would support a further variance reduction of the posterior distribution. In this direction, we consider as RVs the Paris-Erdogan law material parameters (C,m), the average cycles and the stress range encountered by a commercial ship (Navg, Δσ) and the initial crack length (α0) that are collected in random vector θ. We identify from the literature already proposed probabilistic models and suggest new knowledge-based descriptions for these RVs. Uncertainty is propagated in a forward setting through the crude Monte Carlo Simulation method and as such the statistical structure of a|θ,τ and T|θ,τ RVs is estimated. Results: A proper statistical analysis is performed and presented, that includes sample statistics, histograms and subsequent fitted models for both a|θ and T|θ and compared on the basis of the different probabilistic model definitions for the basic RVs. An indicative obtained probabilistic description of the Paris-Erdogan law is presented in Figure 1. Conclusion The performed sensitivity analysis of the RV models to the quantities of interest has shown that the distribution type and corresponding parameters, in particular for the (Navg, Δσ) need to be defined with caution as they have been found to significantly control the statistical structure of the priors.

125 Probabilistic description of the Paris-Erdogan crack growth predictive model.

126 99 Durability and fractography of aluminum alloy 6060 after fatigue tests under bending and torsion loading Małecka J1 , Skrobacz S1 , Chudy R1 , Derda S1 , Kuś J1 , Lagoda T1 1Opole University Of Technology The paper presents the results of fatigue tests of the 6060 aluminum alloy subjected to cyclic fatigue tests. Samples made in two states of heat treatment, T6 and T64, were tested. This material has different applications depending on the treatment used. In the case of T64 machining, the alloy is characterized by increased strength and is suitable for bending. In the case of T6 treatment, high-strength elements are obtained. However, in this case, the elements are not suitable for plastic forming and bending. Profiles made of this material are used for the production of windows and doors installed in rail vehicles. Fatigue tests were performed with cyclic bending and cyclic torsion. In addition, fatigue tests were performed with two combinations of proportional cyclic bending and torsion. All studies were performed with a zero mean value (R = -1). Based on biaxial stress fatigue tests, various multiaxial fatigue criteria were applied for reduction to an equivalent stress state. After the fatigue tests were performed, the surface of the resulting fatigue fractures was analyzed. The analysis was carried out for two samples, at low and high loads for four combinations of fatigue tests. This gives a total of 8 carefully analyzed samples. Fatigue fracture analysis was performed on the Tescan Vega 4 scanning electron microscope. The evaluation of the surface condition of the prepared samples and the analysis of the geometric structure of the fracture surface after fatigue tests was performed on the Sensofar S-neox optical profilometer. As a result of research and analysis, the effect of machining on both the fatigue life and the obtained surface of the fatigue scrap was demonstrated.

127 100 Influence of geometry on the failure behaviour of force-locking and formlocking shaft-hub connections on the example of the inner knurled pressfit connection Hentschel T1 , Hasse A1 1TU Chemnitz In the field of drive technology, the demand for backlash-free transmission of high power is increasingly met by the use of combined force-locking and form-locking hub-shaft connections. Being able to transmit high power densities under static and cyclic loads, these specific couplings additionally allow both functional integration and an outstanding potential for lightweight design. A representative of these hub shaft connections is the knurled press-fit connection, whose design as an inner knurled press-fit is the focus of this scientific paper. Focussing on functionality, an internally knurled hard hub is pushed into an oversized soft shaft, creating a frictional and form-locked contact zone of the shaft-hub connection. For evaluating failure behaviour under practice-oriented loads, it is necessary to identify material-independent failure mechanisms and to consider suitable failure criteria in the environment of consolidated structures under residual compressive stresses. The scientific activities include experimental investigations of the joining and release force progression as well as torsion tests controlled by the angle of rotation up to the total failure (shearing, slipping) of the connection. In detail, the transmission and failure behaviour of the inner knurled interference fit is investigated by combining thick- and thin-walled hardened hubs (16MnCr5) with solid shafts (42CrMo4+QT) carrying variable geometric overlaps. The resulting force and moment diagrams provide information about the transmission potential and are supplemented by microscopic observations of the failed contact zone. Finally, the results of the evaluation are used to calibrate a numerical process model, which is applied to characterise non-measurable variables such as strain hardening distribution and residual stresses in the contact zone. Regarding the experimental results, qualitative differences in the height of the failure limits as well as in the characteristics of the corresponding failure patterns in the contact zone can be identified. Thereby, oversized, thin-walled joints require a reduced joining force and fail at smaller torsional loads than their thick-walled equivalents. Knurled Press-fit joints with low hub wall thickness or with the presence of small geometric interferences also tend to have a damage pattern that is primarily caused by slipping movements on the tooth flanks of the softer shaft. In contrast, the contact zone of joints with thick-walled hubs or high interference is affected by local shearing at the tooth root and the tooth flanks of the shaft implying a mixed form of slipping and shearing failure mechanisms. Including numerical observations, thick-walled connections are additionally exposed to higher rates of deformation at the tooth root and the tooth flanks due to the joining process covered by the residual compressive stresses of the interference fit. Based on the results, the dominant failure mechanism in the contact zone is geometry-dependent and is influenced by the amount of existing radial stiffness (wall thickness) as well as by the design of the mating profile (interference). The tooth structures strengthened by the forming of the contact zone and the presence of high compressive residual stresses encourage a mixed form of slippage and only local shearing.

128 Keywords: inner knurled press-fit, form-fit, press-fit, shearing, slipping, failure mechanism Design of the inner knurled press-fit Experimental and numerical torsion studies up to total failure of the shaft-hub connection

129 101 Towards Automated Fatigue Striation Counting von Bestenbostel W1 , Schertler K1 1Airbus The counting of fatigue striations on the fracture surface is the only possibility to comprehend the crack growth behavior of a fatigue crack. This kind of “Quantitative Fractography” is therefore a major tool of failure analysis as it gives evidence for crack initiation times and helps defining inspection intervals of aircrafts. The process of striation counting is very time consuming as the location of each measurement point has to be related to the distance to the cracks start and the individual striation spacing. Additionally, the results is to a certain degree dependent on the interpretation and operation method of the lab specialist. In a first step, a round robin test of all failure analysis laboratories within Airbus was carried out to review the reproducibility of the measurement procedures and the different evaluation methods. Based on the results a unified internal test standard (AITM) was defined. Within the project Failure Analysis Towards Automation (FANTOM), a new partly automated striation counting method, the “Sandhopper” tool, was developed as a demonstrator. The tool simplifies the striation counting process by a fully automated recording of the geometry data. An algorithm for an operator controlled, automated determination of the striation spacing is patent pending. On basis of the AITM, the data are automatically evaluated and the crack growth curves are generated. To review the Sandhopper tool, standardized picture sets of fatigue fracture surfaces were evaluated by the manual method and the automated method. The results show that the Sandhopper generates well reproducible results which are nearly independent from the operator. Overall, the Sandhopper tool demonstrates the way forward to reproducible, operator independent evaluation of striation counting. With the dedicated aim for the fracture analysis of aluminum fracture surfaces with constant amplitude loading, it covers most of the fuselage damages. Nevertheless, the graphical user interface and the underlying algorithms allow the counting of other types of fracture surfaces with their respective limitations.

130 102 Very High Cycle Bending Fatigue response of Ni-Al Bronze Chantziara K1 , Sadek M1 , Chabbah A1 , Grehk M1 1Karlstad University Introduction The properties of Nickel-Aluminum Bronze (NAB) alloys have a unique combination of high strength, lightweight, wear, galling, corrosion, and cavitation resistance, as well as high damping capacity¹. These properties make the alloy particular suited for maritime and in particular propeller applications. For propeller the most relevant fatigue load cases are torsion and bending fatigue, and this work focuses on the latter. The samples were cut out from a larger structure that was manufactured by sand molded casting, followed by a heat treatment step to obtain the final microstructure. During the last decades, Very High Cycle Fatigue (VHCF) research has developed into an active and prioritised research area since the number of cycles up to 10⁷-10¹⁰ can be reached within a reasonably short amount of time by the development of 20 kHz ultrasonic fatigue testing equipment. The advantage of the aforementioned method is that can provide information about critical defects in a large sample volume. The defects e.g. intermetallic inclusion, can be very difficult to detect using conventional imaging techniques that are constrained by small inspection volumes. In the present effort, the VHCF properties in bending fatigue of a NAB alloy from a particular production route is investigated in by three point bending in the HCF and VHCF regimes. The result from the fractography and its implication on the SN curve is discussed. Methods Testing in the VHCF regime was carried out using the 20 kHz ultrasonic fatigue testing system (UFTS). All experiments were carried out in a three point bending set up (Fig.1). Fatigue strength at 10⁸ load cycles was evaluated using the staircase test method, while detailed fractography was performed by SEM. Results Figure 2 illustrates the initiation points for three different stress levels at different life cycles. Conclusion VHCF samples were tested to the final failure or to the maximum life of 10⁹ cycles. According to the staircase method, the fatigue strength at 10⁸ cycles was calculated. The detailed fractography revealed that the critical defects are strongly correlated to the manufacturing process, and their size have a determinant role. For low number of cycles/higher stresses, defects exactly below the surface were the initiation points for the fatigue crack, while for long lives internal defects of big size led to the fracture.

131 References 1. E. A. Culpan, and G. Rose, Corrosion Behaviour of Cast Nickel Aluminium Bronze in Sea Water, Br. Corros. J., 14, 160 (1979). Schematic presentation of the three-point bending test at 20 kHz using the UFTS. Initiation points of NAB alloy at different fatigue life ranges.

132 103 New temptations in hot structural fabrication of aero engine components Andersson J1 1University West Superalloys are materials with unique characteristics, not least regarding their superb temperature capability and strength in relation to ordinary materials such as stainless steel. The superalloys are readily used in aero-engines and specifically the hot section which serves as the most challenging application. It is therefore of high importance that the welds used in the design are of suitable quality to account for the demanding environment. Cracking and specifically hot cracking as well as strain age cracking (SAC) is of concern during the welding and additive manufacturing (AM) of these components. Despite these challenges, fabrication in which welding is commonly utilized is being more and more employed to tailor structural fabrications in an improved manner to reduce weight as well as to increase performance. Two new superalloys, G27 and VDM Alloy 780, have been developed with matching and improved properties to the well-known Alloy 718 and Waspaloy. These new superalloy candidates are intended to be used in the hot structural parts of jet engines with an improved service temperature of up to 750°C that has been preferably fabricated by welding small pieces of superalloys instead of casting single large parts. This presentation will provide advice and information on welding and weldability aspects of Ni- and Ni-Fe-based superalloys in general and G27 as well as VDM Alloy 780 in specific.

133 104 Tensile properties of 3D printed INCONEL 718 cellular specimens Monkova K1,2, Pantazopoulos G3 , Monka P1,2, Toulfatzis A3 , Lengyelova K4 , Papadopoulou S3 1TU Kosice, FMT with a seat in Presov, 2TBU in Zlin, Faculty of Technology, 3ELKEME Hellenic Research Centre for Metals S.A., 4TU Kosice, Presov, Faculty of Mechanical Engineering Additive technologies are currently becoming more and more in demand for the production of components intended for a wide range of industries and the economy. Their primary advantage - the possibility to produce bodies of complex shapes, which cannot be produced by conventional technologies, is complemented by a number of other benefits. One of them is the possibility of manufacturing lightweight components, the core of which is replaced by porous structures. Since there are many different types of structures, it is important to know their behavior and properties under different storage and loading methods. The aim of the presented research by the authors was to compare the behavior of 4 types of cellular structures under quasi-static tensile stress, while two samples were formed by monostructures Gyroid 10% and Diamond 10%, and the other two types were bi-structures, which were created by combining two structures (Gyroid 5% + Gyroid 5%) and (Gyroid 5% + Diamond 5%). The comparison criterion was a constant 10% total volume fraction of material in all 4 types of samples. The comparison criterion was the same 10 % total volume fraction of material in all 4 types of samples. The samples were made of Inconel 718 by Direct Metal Laser Sintering technology on an EOS EOSINT M270 machine with a sintered layer thickness of 0.04 mm in one production cycle as a set. All samples were heat treated according to *AMS 5664 procedure with inert gas before being removed from the platform. Stereomicroscopic observation of the fracture surfaces was performed with a Nikon SMZ 1500 stereo-microscope. The surface of the samples was finely sandblasted, while the surface roughness showed a Ra value of 12.5 μm. Tensile tests were performed on an Instron 8802 servo-hydraulic testing machine with a maximum capacity of 250 kN at ambient temperature. The results showed that the maximum load corresponded to the diamond (D) cellular structure (approximately 48 kN), while the minimum load was observed for the gyroidgyroid (GG) structure. From a macroscopic point of view, the fracture modes highlighted the deformation character of the cellular components showing plasticity behavior and necking of the adjacent walls.

134 105 Microstructure of White Etching Area around Subsurface Cracks in Bearings Banis A1 , Nikolic K1 , Malet L2 , Petrov R1 1Ghent University, 2Ecole Polytechnique de Bruxelles, Rolling Contact Fatigue (RCF) is a very high-cycle fatigue process, leading to the formation of so-called white etching areas (WEA) around cracks (WEC). Very often, but not always at the first stage of damage formation, butterfly cracks around non-metallic inclusions are developed, and later they grow and merge. The current work aims to describe the crack initiation and microstructural changes inside the WEA around butterfly cracks in the hardened and tempered bearing steel with artificially introduced Al₂O₃ inclusions and on real bearings. The results from investigations were acquired via a combination of optical microscopy, scanning electron microscopy (SEM) combined with energy dispersive X-ray analysis (EDS), Electron Backscattered Diffraction (EBSD), Transmission Kikuchi Diffraction (TKD) and Transmission electron microscopy (TEM) in combination with automatic crystallographic orientation mapping in TEM (ACOMTEM). EBSD measurements showed a high level of local grain misorientation at Al₂O₃/steel matrix interface, suggesting possible microcracks initiation locations. The TEM samples containing the cracks were selected from specific locations using a precise FIB preparation process, allowing the TEM analyses of the significant microstructural changes between the butterfly crack (formation of ultra-fine nano-crystalline ferrite) and the steel matrix (tempered martensite). It was found that the butterfly crack growth and microstructural changes (formation of nano-crystalline ferrite) are simultaneous processes due to low-temperature recrystallization. Additionally, the M₃C-type carbides were completely dissolved in the WEA (cf.Fig.1). Fig.1: (a), (b) and (c)- EBSD maps; (d) TKD scan with HAGBs >15°; (e) BF-TEM image: 1-carbide, 2-undemaged matrix; 3, 4-deformed zones.; (f) TEM from WEA; (g) results EDS analyses.

135 106 Failure analysis on premature fracture of valve rod of circulating pump gate valve in a nuclear power plant Yang Z1 1 Fudan University The failure incident addressed in this study is about premature fracture of the valve rod, which was used to control water flow during maintenance and emergency stop of the circulating water pump in a nuclear power plant. Although the valve rod design lifetime of the rod was three years, it suffered a premature fractur after being in service for only fourteen months. In order to find out root cause of its premature failure, the multiple characterization methods were used, including optical microscopy, tensile test, impact test, scanning electron microscopy, energy dispersive spectroscopy, etc. Based on experimental results and characterization analysis, it was found the microcrack of the ruptured rod was initiated near its surface, then progressively propagated, and finally led to fracture. So the abnormal fracture of the rod should be primarily ascribed to material defects，including strip-like inclusions and delamination near the rod surface. Finally，the associated failure mechanism and cause were discussed in detail and the pertinent countermeasures were proposed as well. Keywords Failure analysis, Nuclear power plant, Seawater, Stainless steel, Valve rod

136 107 The influence of over-aging on the multiaxial fatigue behavior of the cast AlSi7Cu0.5Mg0.3 alloy LE V1 , OSMOND P2 , BELLETT D1 , MOREL F1 1Arts et Métiers Institute of Technology, 2 Stellantis Cast aluminum-silicon alloys are widely used to manufacture automotive components, often subjected to cyclic loads. Hence, the optimization and understanding of the fatigue behavior of these materials is of vital importance. This paper focuses on the effect of over-aging on the high cycle fatigue strength of the precipitation hardened, die-cast AlSi7Cu05Mg03 aluminum alloy, when subjected to multiaxial loads. The high cycle fatigue behavior of Al-Si cast alloys has been extensively studied in the scientific literature. In particular, the effects of microstructural heterogeneities have been well documented (i.e. effects of: microshrinkage porosity, precipitates, oxide films and different DAS or SDAS). This is generally for alloys with a standard heat treatment, often the T7 treatment. However, it is well known that the aging treatment has a significant influence on the mechanical properties of these alloys. The effect of over-aging on the monotonic tensile strength and the cyclic hardening behavior has been investigated in numerous studies; however, its influence on the multiaxial fatigue behavior is much less clear. The objective of this work is to understand the effect of over-aging on the high cycle fatigue strength under both tensile and torsional loads. The die-cast AlSi7Cu05Mg03 alloy in three different over-aging conditions has been investigated. A significant difference in the properties of the aluminum matrix, especially its hardness, was observed as a function of the over-aging condition. However, over-aging did not influence the DAS/SDAS or the pore size distribution. This made it possible to decouple the influence of the properties of the aluminum matrix on the fatigue strength under multiaxial loads. It was shown that while the effect of over-aging on the uniaxial tensile fatigue strength was relatively limited, the effect is more pronounced for the torsional loading mode. A fractographic analysis showed that fatigue crack growth from pores, with a limited initiation phase, is the main damage mechanism for the specimens tested in tension. For torsional loads, fatigue cracks initiate in the aluminum matrix on planes of maximum shear stress. These observations can explain why over-aging has a greater influence on the torsional fatigue strength when compared to the uniaxial tensile case.

137 108 Evaluation of the susceptibility of Refractory Multicomponent alloys to Thermal Shock towards the improvement of their manufacturability Salvarado R1 , Stavroulakis P1,2, Pantazopoulos G2 , Goodall R1 1The University of Sheffield, 2ELKEME S. A. Introduction BCC Refractory Multicomponent alloys (RMCAs) are a novel class of materials known for their impressive mechanical properties and high strength, surpassing that of FCC MCAs. However, they are characterized by low ductility during deformation under ambient conditions [1]. This has been attributed to the formation of the B2 phase encountered in these alloys through an order-disorder (B2-BCC) transformation mechanism at lower temperatures. One such RMCA is the equiatomic AlTiVCr alloy which we have demonstrated to outperform even the more advanced high-modulus steels in terms of its elastic properties [2]. Nevertheless, it suffered from the same lack of room temperature ductility as it was also characterized by a single B2 phase after manufacturing through vacuum arc melting (VAM). Subjecting this alloy to a high temperature heat treatment followed by water quenching (WQ), the order-disorder transformation can be partially suppressed leading to the manifestation of a dualphase BCC-B2 microstructure. Furthermore, by tuning the amount of Al present in the alloy, the complete suppression of the BCC-B2 transformation can be achieved, resulting in the formation of a singlephase BCC and dualphase BCC-B2 in the WQ and FC conditions respectively. This study evaluates the effects of these processing and compositional modifications on the ductility of these novel compositions. Methods The alloys were manufactured through VAM and were heat treated at 1200oC – 8h in a flowing Ar furnace. Optical (OM) and Scanning Electron Microscopy (SEM) alongside X-ray Diffraction (XRD) and Differential Scanning Calorimetry (DSC) was used to evaluate the microstructural features and fracture surfaces of the alloys while the thermal properties were measured through thermal conductivity measurements and dilatometry. Results Interestingly, no improvements in ductility were observed between the WQ and FC condition during compression testing under ambient conditions in any compositions. In the case of the equiatomic AlTiVCr alloy, the ductility of the WQ dualphase BCC-B2 alloy was inferior to the singlephase furnace cooled (FC) B2. Post heat treatment, WQ samples contained more cracks compared to the FC ones. An investigation of the thermal properties of the alloys uncovered extremely low thermal conductivities. This may have caused the inhomogeneous distribution of temperature along the volume of the samples during exposure to rapid thermal cycles, the development of notable stresses between different specimen regions, the formation of cracks and their eventual in-manufacturing failure. Conclusion The findings of this work highlight the importance of utilizing a controlled manufacturing process to produce this range of alloys and the criticality of preventing the exposure of RHEAs to thermal shocks. Apart from

138 documenting this phenomenon, this study also sheds some light into the failure mechanisms encountered in these alloys as a function of their chemical composition. References 1. Liu, F., Liaw, P. K., & Zhang, Y. (2022). Recent Progress with BCC-Structured High-Entropy Alloys. Metals, 12(3). https://doi.org/10.3390/met12030501 2. Stavroulakis, P., Freeman, C. L., Patel, D., Utton, C., & Goodall, R. (2022). Successful prediction of the elastic properties of multiphase high entropy alloys in the AlTiVCr-Si system through a novel computational approach. Materialia, 21, 101365. https://doi.org/https://doi.org/10.1016/j.mtla.2022.101365

139 109 Investigation of artificial aging response to pre-deformation by microstructural examination, microhardness testing and differential scanning calorimetry of Al 6063 extruded profile. Stachouli E1 , Lamnatos G2 , Papadopoulou S1 , Rikos A1 , Aslanis P1 , Vazdirvanidis A1 1ELKEME Hellenic Research Centre For Metals S.A., 2 School Of Mining and Metallurgical Engineering, NTUA An investigation has been conducted on the influence of different pre-deformation conditions to the artificial aging response of extruded 6063 Al alloy automotive profile. The aim of this project was to provide further understanding in the optimization of the thermal treatments of automotive bumpers for attaining improved crashworthiness as this is determined by a structure which exhibits similar mechanical properties in all regions. Samples were solution heat treated, quenched, pre-deformed by 2%, 5% and 10% through tensile testing. They were subsequently artificially aged at three different temperatures (150 ⁰C, 180 ⁰C, 210 ⁰C) for 10, 100 and 600 minutes for simulating the deformation and metallurgical condition of different areas of the actual bumper. The main target was the determination of the specific combination of deformation and aging conditions that could lead to high overall strength and simultaneously low differences in strength among aged samples with different amount of deformation. The analytical techniques that were selected for the current project were metallographic examination for investigation of the amount of inter and intragranular Mg₂Si precipitation as well as the presence of precipitation free zones (PFZ), microhardness testing and Differential Scanning Calorimetry (DSC). Examination revealed that aging at 180 ⁰C for 600 minutes led to the maximum hardness (81 HV1.0) and at the same time, the deviation of the hardness values of the samples with different pre-deformation degrees was very small (0% deformation exhibited 70 HV1.0, 2% deformation exhibited 78 HV1.0, 5% exhibited 80 HV1.0). Acknowledgments: The authors would like to express their gratitude towards the ELKEME SA management as well as Dr. Vasilios Kostas for his contribution to Differential Scanning Calorimetry (DSC) examination.

140 110 Fracture analysis of a cold working die used in the aluminum packaging tubes production Papageorgiou D1,2, Mastoridou N3 , Medrea C2 1 Laboratory of Manufacturing Technology, School of Mechanical Engineering, National Technical University of Athens, 2Department of Mechanical Engineering, School of Engineering, University of West Attica, 3N. Bazigos S.A., Design and manufacturing of molds Abstract Aluminum tubes represent a versatile packaging solution for a wide range of applications. It is one of the most common choices in the packaging of pharmaceutical, cosmetic, and personal care products. The local pharmaceutical companies package several products in aluminum tubes. In this specific application, the tubes require the highest quality of material used as well high precision in forming during manufacturing. The pieces were manufactured via cold work progressive stages. A circular disc (a slug), of the size of a coin, is deformed by a set of tools in an extrusion press, in order to acquire the final tube form. Then, it is thin walls are ironed to end form to the predicted length on both top and bottom ends. Finally, a thread is made in the socket of the tube, that allows the cap to be screwed on. If required, the inner surface of the tube is insulated by spraying of suitable substances. Internally coated or not, the external surface of the tube is coated, colored, offset printed and finally decorated accordingly to the customer’s specifications. A local company produces aluminum tubes for the packaging of medicinal ointment. A plug and a sleeve is used For the forming of the neck of the tube, (Fig.1). These components repeatedly fail, diminishing production reliability. Historical data was collected and macroscopic examination was performed. A photographic archive was created to underline the most significant features. Hardness measurements were carried out on particular surfaces of the parts. The tool steel selected for the manufacturing of the parts was identified by chemical analysis. Samples were selected, cut and prepared for optical microscopy. The study involved a detailed examination of the microstructure and fracture morphologies of the specimens derived from the failed parts. Conclusions related to the fracture mechanism and the type of fractures are presented. The main causes of the fracture were evaluated, and recommendations were provided in order the process reliability of the subassembly to be improved. Relatively wide range in dimensional tolerances of the forming tools led to a lack of concentricity between the plug and the sleeve; provoking malfunction of the forming process and consequently brittle fracture of the die occurred. Furthermore, the frequency of the sleeve failure should have been a sign of the material selection insufficiency. References [1] Aluminium Tubes (2023), Technical Fact, Favia Aluminium Tubes, Verona, Italy, https://www.favia.it/en/applications/, [Accessed 25Mars. 2023].

141 Fig.1 General aspect of the failed components

142 111 Protecting Spacecraft against Hyper-Velocity Impact: Problems and Solutions. Tompros D1 , Mouzakis D1 1Hellenic Army Academy Protecting Spacecraft against Hyper-Velocity Impact: Problems and Solutions. Dr. Dionysios Tompros, Dr-Ing. D.E. Mouzakis ABSTRACT Objective: Earth-orbiting as well as solar system probes and spacecrafts are susceptible to impacts by micrometeoroids and pieces of orbital debris. These impacts occur at extremely high speeds (>15,000 km/h) and can damage flight-critical systems, which can in turn lead to catastrophic spacecraft failure. This shall probably plague also the future manned missions to Mars and other celestial bodies of our solar system. The new state-of-the art James Webb Telescope has already been hit twice at its L2 orbital point. Methods, Conclusion: With the advent of many new high-strength composite materials and their proliferation in aircraft applications, it is necessary to evaluate their potential for use in long-duration space and aerospace structural systems. Several experimental investigations in which several different composite materials were tested for their ability to prevent the perforation of the walls in multi-wall systems subjected to hypervelocity projectile impact. Damage to multi-wall systems that employ composite materials is comparable to damage in traditional all-aluminum multi-wall structures of similar geometry and weight under similar impact conditions. The advantages and disadvantages of using composite materials in perforation-resistant multi-wall structures are presented and discussed. The effectiveness of multi-wall systems with composite materials varies significantly depending upon the location within the multi-wall system of the composite materials. Hybrid systems with alternating metal and composite plates seem to provide for the moment the best protection.

143 112 Temperature dependent fiber/matrix interfacial debonding in CFRPs Zaverdinos G, Dragatogiannis D 1DELTA-MPIS, DELTA-MPIS, Technological Park of Lefkippos The study showcases the importance of thermal effects in the fiber/matrix interface degradation in a carbon fiber reinforced polymer, which ultimately affects composite failure in several applications. Interfacial failure is one of the most common sources for micromechanical failure in composite parts, which develops into macro-mechanical failure for the total part. The objective of the present work is to effectively investigate the impact of elevated interface temperature on the degradation of unidirectional fiber-matrix interface. The methodology is established on the numerical simulation of a pullout experiment with the Finite Element Method. Appropriate elasticity theories and fracture relations are adopted and applied in 3D single fiber and multifiber finite element Virtual Crack Closure Technique (VCCT) models. The phenomenon is divided into a crack initiation phase, approached with the quadratic failure criterion, and a crack propagation phase – approached with the Benzeggagh Kennane criterion. The target quantities include stress and strain contours for the progression of the crack, as well as Energy Release Rates (ERRs), work required to achieve separation and interfacial strength. The simulation evaluates and quantifies the effect of temperature in the failure mechanism of fiber reinforced materials. Multiple material combinations are used in the study, to account for the effect of different polymeric matrices and fiber filaments. Furthermore, the effect of the development of an additional crack is studied quantitatively, along with the impact of the presence of neighboring fibers and different volumetric fractions. The study results indicate that additional cracks developed during the pullout process, favor quicker and less energy demanding separation and that the presence of neighboring fibers in the model increases energy and time requirements.

144 113 Armor plates made from household and “off-the-shelf” materials for use by citizens in life threatening conditions Nasikas N1 , Emmanouil P1 , Markoulakis A1 , Mouzakis D1 1Hellenic Army Academy Introduction As war conflicts evolve over the years, we are seeing a definite shift in the areas where actual battles take place. World War I and II were fought mostly on open fields in central Europe and the Pacific, whereas conflicts like Afghanistan, Syria and now Ukraine are being fought mostly in urban areas [1]. This means that civilians and unarmed populations are now more vulnerable to life threatening situations. Safety material such as armor vests and equipment like breast plates and bullet-proof helmets are not easy nor cheap to acquire and of course are not common to have in every household. Scope of the Study Instead, in every household one can find a variety of materials that can be used to make armor plates or increase the ballistic performance of ordinary plastic safety helmets. Even in ancient Asia, layers of paper were used as armor plates [2]. So, the basic idea of this work was to use all kinds of available off-the-shelf or household utensils and materials in order to construct effective but affordable and easy to make antiballistic equipment [3]. Materials & Methods In this work we combined layers from Denim and cotton fabric from army fatigue uniform, which are extremely common and exist pretty much in every wardrobe, along with usual ceramic tiles and glass epoxy resin in order to construct armor plates that have the ability to work as anti-ballistic breast plates. The constructed breast plates were tested in an open firing field and their antiballistic behavior was found to be very promising. Work is ongoing with other off-the-shelf materials in order to find the optimal combination for civilian ballistic safety applications.

145 114 Determination of stresses in the combination of proportional cyclic bending and torsion of RG7 bronze according to different plasticity models Paduchowicz M2 , Głowacka K1 , Małecka J1 , Lagoda T1 1Opole University Of Technology, 2Wrocław University of Science and Technology The work analyzes the fatigue behavior of samples made of RG7 bronze. The tests presented in paper [1] concerned fatigue tests under conditions of pure cyclic torsion, cyclic torsion and two combinations of proportional cyclic bending and torsion. This bronze is characterized by relatively high plasticity. Therefore, the adoption of a perfectly elastic body model in this case results in a significant overestimation of the stress amplitudes. This paper presents calculations of stresses and strains according to the model of an elastic-plastic body using the finite element method. The calculations were made for the fatigue life in the middle part of the Basquin fatigue characteristic, i.e. for 105 cycles. These results were compared with the results of calculations in accordance with the previously proposed analytical and numerical model proposed in [1]. As a result of the comparison, a very high convergence of these two models was shown. The average error of the determined stress amplitudes is 3% for the elastic-brittle model, and 9% for the elastic-plastic model, respectively. Therefore, it was shown that the proposed analytical and numerical model can be successfully used to assess fatigue life under cyclic bending with torsion. [1] Małecka Joanna, Łagoda Tadeusz: Fatigue and fractures of RG7 bronze after cyclic torsion and bending, International Journal of Fatigue, Elsevier Ltd, vol. 168, 2023, pp. 1-12, DOI:10.1016/j.ijfatigue.2022.107475

146 115 Bird strike analysis of new composite inlet for tilt rotor aircraft Doubrava R1 , Vlach J1 , Oberthor M1 , Bělský P1 1Výzkumný a zkušební letecký ústav, a.s. Bird strikes are important phenomena that must be considered when designing aircraft. Most major bird strike incidents are a result of engine damage. Because an engine is the sole thrust-providing system of an aircraft, the effect of bird strikes on engine inlets and systems must be investigated and mitigated to the maximum extent. Especially in the case of convertible aircraft, such as an aircraft with tilting rotors, this effect is critical from the point of view of the operation, from the point of view of flight mechanics and the overall control of the aircraft. International certification regulations require that all forward-facing aircraft components be proven to withstand bird strikes to a certain level before they can be used in an aircraft. A bird or hailstone impact test provides a direct method for determining bird strike resistance; however, the design of aircraft structures typically involves numerous iterations, from design to manufacturing to testing and back, requiring that many bird impact tests be conducted. This is not only time-consuming but also costly. Furthermore, the experimental data from these tests are frequently narrowly focused, acting as a barrier to their direct use in refining structural designs. Owing to these shortcomings, several numerical methods have been developed to simulate bird or hailstone strikes to reduce the number of intermediate tests required and subsequently shorten the duration of the component design phase. The aim of the contribution is the design of the proof of resistance of a new composite air inlet for new tilting rotor aircraft using verified numerical simulations on flat and simple curved test panels. The new technique for material model calibration was used for numerical simulation and impact damage analysis. Building block diagram for bird strike resistance analysis of composite inlet

147 116 Fatigue and fracture of the aeronautical Al-Cu-Li 2198 alloy for different ageing tempers Ioannis Goulas1 , Alexis Kermanidis1*, Christina Charalampidou2 , Stavros Kourkoulis3 , and Nikolaos Alexopoulos2 1 Department of Mechanical Engineering, University of Thessaly, Athens Avenue, 38334 Volos, Greece. 2Research Unit of Advanced Materials, Department of Financial Engineering, School of Engineering, University of the Aegean, 41 Kountourioti str, 82132 Chios, Greece. 3 Laboratoty of Testing and Materials, Department of Mechanics, National Technical University of Athens, 9 Heroes Polytechniou Str., 15773 Athens, Greece. During the last decade, third generation Al-Cu-Li alloys are widely used in aircraft and aerospace applications owing to their high specific strength, lightweight, good corrosion resistance, and enhanced damage tolerance capabilities (fatigue crack growth and fracture toughness). As the light-weight structures are often subjected to cyclic mechanical loads during the aircraft service life, outstanding fatigue damage tolerance and resistance is required. The long-term usage of the materials may lead to the degradation of the alloy’s damage tolerance and mechanical performance during its service life. Degradation of the mechanical properties, such as ultimate tensile strength, fracture toughness, as well as elongation at fracture (ductility) may be brought on by several mechanisms, including natural ageing of the alloy, intergranular corrosion, and hydrogen embrittlement, as well as their combined effects. Hence, the fatigue performance of these alloys as well as the degradation mechanisms should be investigated. In the present work, the fatigue behaviour and fatigue crack growth characteristics of 3rd generation Al-Cu-Li alloy 2198 is investigated and for four (4) different artificially aged tempers, simulating natural aging of the alloy and their effect on the respective mechanical behaviour of the alloy. The material used was a wrought aluminum alloy 2198-T3 which was received in sheet form of 3.2 mm nominal thickness. Tensile, fatigue and fracture toughness C(T) specimens were machined from the sheets according to ASTM E8, E466 and E561 specifications, respectively. Afterwards, the specimens were exposed to artificial ageing heat-treatment for different ageing times in order to simulate the different ageing tempers named as under-ageing (UA), peak-ageing (PA) and over-ageing (OA). Tensile, fatigue and crack growth resistance tests were performed to evaluate the residual mechanical properties. It was shown that the different ageing conditions alter the fatigue endurance limit of the alloy, as well as the high cycle fatigue regime. Likewise, the stage II fatigue crack propagation rate is essentially changed for the different investigated tempers. Acknowledgements. The work has been financed by the Hellenic Foundation for Research and Innovation H.F.R.I.-Project ID 03385 Acronym CorLi “Corrosion susceptibility, degradation and protection of advanced AlLi aluminium alloys”.

148 117 A damage parameter for a critical plane approach for fatigue strength assessment within the FKM-Guideline for non-proportional loading Fällgren C1 , Vormwald M1 , Beier T1 1Technische Universität Darmstadt In general, a fatigue strength assessment for multi-channel non-proportional loading is possible within the scope of the FKM Guideline "Analytical Strength Assessment". However, according to the current state of the guideline, unsatisfactorily conservative calculation results are to be expected when using the existing algorithms. To overcome this problem, a damage parameter is investigated for use with the critical plane method. The damage parameter is adapted for use within the scope of the guideline. Emphasis is placed on the accuracy and compatibility with the guideline. Within this work, the parameter is introduced and used for comparative calculations with experimental results found in the literature.

149 118 FKM-Guideline “Analytical Strength Assessment” – Overview and actual developments Rennert R1 , Vormwald M2 , Esderts A3 1 IMA Materialforschung und Anwendungstechnik GmbH, 2Materials Mechanics Group, Technical University Darmstadt, 3 Institute of Plant Engineering and Fatigue Analysis, Clausthal University of Technology For engineers concerned with design and calculation in mechanical engineering and in related fields of industry, the FKM-Guideline for analytical strength assessment has been available since 1994. Now, the current 7th edition of the guideline has been published in 2020. It was elaborated by the expert group "Strength of Components" in the Research Committee Mechanical Engineering (FKM). Based on former and current standards and research work, the guideline has been elaborated and further developed to meet the present state of knowledge. The FKM-Guideline “Analytical Strength Assessment” • is applicable to mechanical engineering and related fields of industry, • allows the analytical strength assessment for rod-shaped (with nominal stresses) and free-shaped (with local elastic stresses) components, taking into consideration all relevant influences, • describes the assessment of the static strength and of the fatigue strength, the latter in the form of an assessment of the fatigue limit, the fatigue strength for finite life or the variable amplitude fatigue strength, depending on the service stress conditions, • is valid for steel, cast iron and aluminium materials • at normal or elevated component temperatures, • is applicable to components produced with or without machining, or by welding. A uniformly structured calculation procedure applies to all these cases of application. Most of the calculation procedure is predetermined. The user is required to provide only the clearly defined input values as the design stress values, the material designation, the temperature, some component properties, and the safety requirements. The static strength assessment against the extremal stresses starts with the normative static strength values, considers technological size and temperature of the component, allows plastic deformation of the component, defines safety factors and results in the static degree of utilisation. The assessment of structural durability starts with the material fatigue strength, considers all relevant influences of the component on the fatigue strength, continues with the mean stress assessment and the damage accumulation, defines safety factors and results in the cyclic degree of utilisation. The FKM-Guideline is open for the consideration of current technical developments to represent the state of the art. This contribution will also give an overview of current research and developments, which have potential for the future improvement of the FKM-Guideline “Analytical Strength Assessment”: • Additional to the FKM-Guideline “Analytical Strength Assessment”, which is based on linear elastic stresses, there also exists the FKM-Guideline “Analytical Strength Assessment under explicit consideration of non-linear Material Behaviour”. Among others, this Guideline contains an improved description of the critical strain in the static strength assessment, which could bring benefit also for the linear-elastic FKMGuideline. • The treatment of multiaxial stress states in the fatigue strength assessment is still a topic of research. A current FKM research project indicates an improved calculation method for the processing of multiaxial stress time histories, which has potential for significant improvement of the existing FKM-Guideline. • Always a wish of the Guideline users is the inclusion of further materials or joint types into the FKMGuideline. The requirements for such extensions of the FKM-Guideline are explained.