ICEAF VII - Book of Abstracts

200 Typical decision tree used for the pre-posterior analysis and SHM information-based strategy optimisation

201 157 Damage of a post-tensioned concrete bridge – unwanted cracks of the bridge girders Sobczyk B1 , Miśkiewicz M1 , Pyrzowski Ł1 1Gdańsk University Of Technology, Faculty of Civil and Environmental Engineering The aim of this paper is to find causes of concrete cracks that have been spotted on the external surfaces of post-tensioned bridge girders. The analyzed bridge is an 8-span structure, located in southern Poland. It is mainly built of double T-beam post-tensioned girders with the longest spans additionally supported by an arch. The bridge spans lengths range from 20 to 45 meters. The T-beam superstructure has been erected with aid of the incremental launching method. The post-tensioning consist of both centric and eccentric tendons. A part of the bridge is shown in figure 1. The damage on the external surfaces of the T-beam girders was noticed at the interface of two assembly sections in the form of longitudinal cracks. It had been spotted before concrete protective coating was applied, namely when the bridge was almost finished. The moment of failure initiation and the reason for cracking was unknown. Thus, it became important for the bridge owner to find the cause of damage and to check whether the bridge state is safe. Therefore, advanced and comprehensive numerical simulations of the bridge response are performed for this purpose, which, what is important, have been preceded by detailed inspection and non-destructive testing of the girders. Static calculations are done, with aid of the Finite Element Method (FEM). At first global linear static analysis is performe using the Sofistik software. A FEM model built of beam and shell elements is created in order to check the amount of longitudinal normal stress in the girders during all the construction stages of the bridge and after it is opened to traffic. Zones with excessive tensile stresses have not been observed in the simulations. The global model has been validated using the data collected during the final acceptance and inspection. Consequently, a local, high-precision computational domain is defined in the Abaqus environment, which allows for detailed description of the stress of state in the girders in different construction stages. A part of the bridge in the vicinity of the interface, where the cracking was observed, is modelled. The computational domain includes all the important bridge elements as the concrete T-beam girders with cable ducts, elements of the anchorage system and all the reinforcement. Thus, solid, shell and truss finite elements are utilized. The cracking propagation process during the calculations is described using the Concrete Damage Plasticity law (CDP). The damage of the girders is initiated when the centric prestressing is applied. The predicted cracking patterns (figure 2) are similar to the ones observed at the site. Further analysis on the local model does not indicate that the cracks will propagate when traffic loads are applied. The bridge cracked during the erections phase. The damage, possibly was either not noticed or ignored by the contractor and site supervisors. The cracks do not compromise safety of the bridge, but should be repaired, for example using the injection grouting technique, in order to maintain durability of the bridge.

202 A view on the analyzed bridge. Quilt contours of the concrete damage in tension (DAMAGET): a) isometric view of the girder model; b) elements where the DAMAGET is greater than 0.

203 158 Numerical and experimental approach in the prevention of construction failure of remotely controlled demolition robots Derlukiewicz D1 , Andruszko J1 1Wrocław University of Science And Technology The paper presents a new numerical and experimental approach at developing a system that helps to prevent accidents involving the structure of remotely controlled demolition robot. These kind of machines are exposed to work in heavy conditions, but in some cases caused by the unexperienced operators, these machines work in not efficient operation. These situations leads to high loading of the robot`s structure that cases the cracking and failure of the structure of the machine, especially of the working boom or undercarriage. In order to avoid operation of the machine under adverse conditions of structural strains, a strength analysis using the finite element method can be conducted to estimate the most efforted areas of the robot structure. Then the experimental verification of numerical model, by application of the sensors (strain gauges and accelerometers) can be used to determine the stress or vibration level in order to avoid the exceed of the maximum values for that structure during operation in a real time. The information gathered from the sensors and processed through developed algorithms is presented to the operator by a sort of Human Machine Interfaces. This helps operator to prevent from incorrect operation of the machine that can led to structure failure. The elaborated method is based on a study of user needs and was developed in accordance with the Design Thinking methodology. An in-depth study of user needs combined with an analysis of the operational system, as well as with experimental tests on a remote control demolition robot, inspired the development of an operator-controlled HMI system. Combined numerical and experimental research helped to determine what data is necessary to develop an HMI system that continuously uses information from sensors installed on the machine. This paper emphasizes the correlation of FEM numerical analyses with the experimental data taken from the sensors to overcome the lack of direct information flow in the case of mechanical operation. The approach for the method starts form creation of the 3D numerical model of the demolition robot carrying structure, with use of finite elements, then on the basis of a discrete model, computational models with appropriate boundary conditions corresponding to measurements on a real object were prepared. Then the finite element strength analyses is performed to determine the most efforted areas in order to select the mounting points of strain gauges in real time experimental testing. The elaborated system of gathering information from the sensors in real time allows to inform the operator of the structure strength state, or unwanted working situations (heavy vibrations of the structure). The robot operator is constantly informed about the stress level of specific structure areas as well as the level of vibration frequencies which may lead the arm to work in resonant frequency. The presented result of investigations applied in the elaborated method that consist the data algorithms allows the system to increase man workplace safety and efficiency as well as increase of the structure lifetime by reducing the possibility of failures and working in extremely heavy states.

204 Experimental testing of ARE remote-controlled demolition robots in a real-life application Numerical model of the roboth as well as the example of the results of numerical simulations for selected area of the structure

205 159 Evaluation of the historic wooden structures condition based on the results of non-destructive tests Mackiewicz M1 , Zimiński K1 , Pawłowicz J2 , Knyziak P3 1Bialystok University Of Technology, 2University of Warmia and Mazury, 3Warsaw University of Technology The purpose of the research is to confirm that it is possible to properly assess the technical condition of the structure using non-destructive methods, what is also confirmed by the compliance of the actual deformations of the structure with the performed calculations. The tests that confirm the formulated assumption was carried out on the historic roof truss of the church built in the years 1579-1601, and then rebuilt in the years 1901-1902. During reconstruction, a new roof truss with a wooden truss structure was made, constructed in such a way that the ceiling above the main nave was made as raised 2 meters up. From the bottom side, the ceiling was covered with a wooden ceiling in the Venetian style (Fig. 1). During many years of use, the side parts of the ceiling have moved significantly (up to 132mm), and some of the wooden structural elements and joints have been damaged as a result of biological corrosion. A number of non-destructive testing methods were used to assess the condition of the historic roof truss: - measurement of displacements and deflections of the roof truss using an electronic theodolite, - inventory of the roof truss using a 3D laser scanner to determine the geometric deformations of the roof truss elements, - determination of wood strength using a woodtester device for testing wood hardness and a moisture meter, - calculations carried out using computer programs intended for the calculations of wooden structures. The source of significant data of the roof truss geometry and its condition was the in-situ testing with a 3D laser scanner. Terrestrial laser scanning allowed to obtain a cloud of points, reflecting the actual condition of the ceiling. Thorough inventory using a 3D scanner provided a complete view of the roof truss structure with the deformations of its individual elements. It was possible to determine the values of displacements for this structure (Fig. 2). The analysis of the deformed geometry, including differences in the deflection values of individual trusses, allowed to identify places suspected of a higher level of wood degradation in structural elements and joints. Non-destructive tests carried out on various samples of pine wood using a woodtester and a moisture meter, as well as verification destructive tests of wood, allowed to initially determine the strength and density of the wood. The numerical computational analysis of the roof truss carried out in two different programs showed that for the proper calculations of displacements and internal forces of the roof truss, it is necessary to take into consideration the real static scheme, the modulus of elasticity of wood, taking into account its creep, humidity, and slippage at joints.

206 Fig. 1. View of the analyzed structure: a) bottom side with a wooden ceiling in the Venetian style, b) roof truss above the ceiling. View of the analyzed models: a) cross-section through the ceiling obtained from 3D laser scanning with visible deformation, b) computational model.

207 160 Reverse engineering as a non-invasive examining method of the water tower brick structure condition Pawłowicz J1 , Skotnicka-Siepsiak A1 , Krentowski J2 , Knyziak P3 , Serrat C4 1University Of Warmia And Mazury In Olsztyn, 2Bialystok University of Technology, 3Warsaw University of Technology, 4Universitat Politècnica de Catalunya-BarcelonaTECH, EPSEB Reverse engineering is a method of obtaining information about the geometry of an existing object, using devices such as 3D laser scanning. The result of the measurements is a cloud of points (Fig. 1). Thanks to the cloud, it is possible to determine the deformations of structural elements, e.g., beams or ceilings. Over a long period of time, the recording of changes in the crack state allows for drawing conclusions regarding the stabilization or progress of the occurring damages. Knowing the changes in loads (e.g., as a result of applying a test load), it is possible to measure the values of structure deflections. The basic factor increasing the usefulness of a cloud of points for various measurements is its density, which depends on the accuracy of the scan. Thanks to the detailed cloud of points, a digital 3D model that will reflect the shape of an existing object can be created. The recorded accurate information about the location, number and course of cracks can be the basis for concluding the causes of their formation and the destructing processes occurring in the structure. The main advantages of the method are speed, comprehensiveness, automatic measurement and high detail of the mapping of the structure geometry along with its damages. The described reverse engineering method was used to analyze and assess the condition of the historic water tower. The paper presents the thesis that laser scanning and reverse engineering are good methods supporting the assessment of the existing buildings’ current state. The authors measured the bottom ordinate of beams and floors and compared the existing deflection with standard limits. Geodetic and geological measurements in situ were also carried out. The cloud of points was used to indirectly examine the vertical deviation of the tower and the results were compared with the data from the geodetic and geotechnical study. The accurate value (129 mm) of vertical deviation of the entire building was obtained during the data analysis. A model of the structure of the object reflecting the real, deformed geometry, including vertical deviation (Fig. 2) was created. The applied method allowed to perform structural calculations in engineering software in order to examine the current stresses state, compare them with the designed ones and determine that the existing structure did not meet the requirements in the standards. Without a cloud of points, it would only be possible to create an approximate model of the structure’s geometry based on the measured basic dimensions of the elements.

208 Fig. 1. Water tower: point cloud with overlaid photos Fig. 2 Water tower: digital model of the building

209 161 Research and numerical assessment of design and construction errors in the swimming pool facility structure Pawłowicz J1 , Skotnicka-Siepsiak A1 , Szeląg R2 , Krentowski J2 , Serrat C3 1University Of Warmia And Mazury In Olsztyn, 2Bialystok University of Technology, 3Universitat Politècnica de CatalunyaBarcelonaTECH, EPSEB The proper performance of swimming pool halls depends on many factors. An extremely important one, due to an aggressive environment with high humidity, is the ventilation system. It is supposed to provide, among other things, the prevention from high temperatures, excessive moisture, chlorine vapors, and problems resulting from the impact of these factors on the structural elements and entire building. Proper design of the ventilation system of the pool hall is a demanding task, which has a key impact on the correct operation of the facility, the thermal comfort of users, energy efficiency and economy, and, above all, the safety of the construction. In the presented article, the condition of the object in operation was analyzed. Using a computational program based on the assumptions of computational fluid dynamics (CFD), an analysis of the distribution of air velocity (Fig. 1), temperature, and thermal comfort parameters was carried out, which made it possible to conclude the correctness of the proposed ventilation solutions. The obtained results made it possible to indicate the necessary changes. The authors considered the modernization of air supply solutions for the glazed northern elevation or changing the air supply system in the skylight shaft zone. The originally designed location of the fan, duct, and nozzle systems was supposed to provide uniform distribution of temperature and air velocity on the glass of the skylights. Numerical studies were compared with the results of the measurements of the actual functioning facility. Measurements of velocity distribution, temperature, pressure, and smoke tests were performed (Fig. 2). The obtained results indicated errors in the functioning of the actual ventilation system of the facility, which in most cases were due to the failure to carry out the original design. They were also partly the result of negligence during the execution of the ventilation system and operation of the system. Ensuring the correctness of temperature distribution in the pool hall often requires the improvement of the thermal insulation of the building envelope. The choice of systems will affect the structural condition of the facility. It is important to ensure the correct thermal insulation of roofs and walls, as well as to fulfill the conditions of limit states of bearing capacity and serviceability of the object. The solutions used in such conditions are not always the most economical, and in the phase of the implementation process itself may be modified by contractors. The ineffectiveness of the ventilation system adversely affected the structure of the examined facility, especially the roofing steel elements, causing damage to the protective coatings and acceleration of corrosion processes. An increase in humidity above the standard limit values resulted in dampening of insulating materials, which caused an increase in the loads transferred to structural elements. The correct identification of the existing defects allowed to eliminate the threat and repair the damaged elements.

210 Fig. 1. Air velocity distribution in the occupied zone, at a height of about 1.00 m from the floor Fig. 2. Smoke test

211 162 Research on the 18th-century buildings in terms of static schemes changes Mackiewicz M1 , Krentowski J1 , Zimiński K1 1Bialystok University Of Technology Condition assessment of building is carried out in order to confirm whether the building structure is safe for people, as well as to determine proper method of building structure repair or strengthening. Increasingly, non-destructive methods and numerical analyzes are used in the process of building structures assessment. It also concerns historic buildings, which are often used for several hundred years. The methods used to identify defects and damages are unreliable and risky in such cases. Historic buildings that are under official conservation protection, even in very poor technical conditions, are usually assessed in terms of their further renovation. Most of the buildings erected in the 18th century have not survived with their original layouts of structural elements. The lack of proper maintenance of such buildings over many years and frequent reconstructions related to the building adaptations for purposes other than originally assumed caused the changes in the work characteristic of structural systems and the way of loads transferring. An additional problem is the fact that renovation and repair works were usually carried out with the use of poor quality materials, based only on the engineers’ experience. The deterioration of the technical condition of buildings is related to the changes of the static system of the main structural elements and their connections. As a result of time passing and the impact of environmental conditions, the static schemes of structural systems change, and thus the redistribution of internal forces differs from the designed state. The process of structure degradation resulting in the static scheme change can be presented on the example of a building with a brick wall structure covered with a wooden roof truss, erected in the years 1753-1755, which is the part of historic back-up facility of palace complex. The intensive degradation process began with damage to the roof covering, which resulted in complete dampness of the roof truss structure as well as the ceilings and walls of the lower floors. Biological and chemical corrosion developed in the wooden elements of the roof truss and in the masonry walls. As a result of the weakening of the support zones, the ceilings collapsed (Fig. 1). This caused the roof truss to lose its proper support. Therefore, there is a problem of assessing the impact of the static scheme change on the load-bearing capacity of the roof structure, and especially on the possibility of carrying out the repair works. The process of the technical condition assessment of a historic buildings is a demanding task for every engineer and the same it is an important stage in the development of professional experience. Identification of defects and damages is not enough. It is important to indicate the causes of the damage and to determine the actual material parameters of the structure. The analysis taking into account the computational model (Fig. 2) of the current static scheme can be especially significant at the moment when the method of building revitalization is specified.

212 View of the roof truss structural elements: a) visible leaks and dampness of the roof structure and walls, b) partially destroyed ceilings. View of the computational model of roof structure: a) geometry, b) exemplary results.

213 Manufacturing, Joining Technologies, and Surface Engineering (Abstracts 163-209)

214 163 Comparison of the bending properties of a radially and rectangularly distributed lattice structure made of ABS material Monkova K1,2, Monka P1,2 , Zaludek M2 , Korol M1 , Kocisko M1 , Baron P1 , Skyvara M2 1TU Kosice, FMT with a seat in Presov, , 2TBU in Zlin, Faculty of Technology The current situation in industrial production requires components to be manufactured quickly and flexibly, not only in terms of production efficiency but also in terms of business competitiveness. In line with this trend, the production potential of sophisticated components, including components with a lightweight porous structure, is increasing. The weight of such components is significantly lower compared to a solid body due to the presence of cavities in the structure of matter, thus opening up possibilities for their use in a wide range of industries ranging from automotive, aerospace and biomedicine. It is therefore very important to know the properties of such lightweight materials and their behavior under different types of loading. The article deals with the comparison of the bending behavior of two lattice porous structures produced by Fused Deposition Modeling (FDM) from ABS material. Five pieces of samples from both types of Rhomboid and Starlit structures with three volume ratios of material were produced and experimentally tested. The bending test procedure was performed at ambient temperature using a servo-hydraulic testing machine. The dependences of force on strain were recorded and stress-strain curves were plotted after calculation. The results showed that with the same volume ratio, the Starlit structure is able to handle almost twice the bending load compared to the Rhomboid.

215 164 Dissimilar joining by 3D printing: Study of the joint design Morgado T1,2,3,4, Leitão C5 , Leal R6 , Galvão I2,5 1CEMMPRE – Centre for Mechanical Engineering, Materials and Processes, Department of Mechanical Engineering, University of Coimbra, 2 LIDA-ESAD.CR - Polytechnic Institute of Leiria, 3 LASI - Intelligent Systems Associate Laboratory, 4CINAV - Navy Research Center, Portugal, 5CEMMPRE – Centre for Mechanical Engineering, Materials and Processes, Department of Mechanical Engineering, University of Coimbra, 6 LIDA-ESAD.CR – Centre for Mechanical Engineerig, Materials and Processes, Polytechnic Institute of Leiria The joining of metals and polymer-based materials has a very high interest for the transportation industry, as it allows the production of lighter components, which is one of the main targets of this sector. However, the joining of these materials by the conventional techniques has many limitations. On the other hand, the joining by welding is in a very embryonic stage, and the quality of the joints is quite far from being the required for service. This way, the development of new techniques for joining metals and polymer-based materials is very relevant for industry. The additive manufacturing technologies may be used for producing these joints though the controlled deposition of the polymer-based materials over the metal substrate. However, the research in this field practically does not exist and there are a huge number of aspects that must be addressed in preliminary studies. One of the aspects most determining the success of the 3Dprinted joints is the joint design, as it will have a strong influence on the joint strength. The present work is aimed to study two different joint designs (simple and pin-reinforced designs) for the 3D-printed joints by comparing their mechanical behaviour under tensile testing. To reduce the number of variables involved in this analysis, the samples were produced using a widely-used 3D-printing filament of polylactic acid (PLA). The tested samples were found to present a very good mechanical behaviour, with the failure occurring outside the joining region for similar values of mechanical strength. These results indicate that these joint designs are able to be tested for the production of metal/polymer-based material dissimilar joints.

216 165 Investigation of bio-based and recycled materials for Additive Manufacturing using Fused Layer Modelling Junk S1 , Vögele P1 1Offenburg University Additive manufacturing (AM) processes are becoming increasingly important alongside conventional processes. As a result, the consumption of materials is also increasing. The most widespread process is Fused Layer Modelling (FLM), which is often used by private and industrial manufacturers as well as in university education. Today, the FLM process often uses synthetically produced materials based on petrochemical processes, such as ABS and PA. Due to the ever-increasing demand and relevance of ecological production, it is becoming more and more important to reduce the ecological footprint in manufacturing with the help of new materials or new methods. In additive manufacturing, the use of bio-based and recycled materials could significantly improve the ecological footprint. So far, there is limited knowledge about which materials are suitable for sustainable production and which are available at all. The aim of this paper is to carry out investigations of the selected materials, which are already commercially available, from a technical point of view and to gain insights into their suitability as materials for AM. In addition, there are the areas of economy and ecology, which together with the technical analysis result in an evaluation. A selection of eight materials is made for the investigation. These materials are divided into four categories: Thermoplastics, recycled thermoplastics, bio-based thermoplastics and fibre-reinforced thermoplastics. Also, mixed forms, e.g. bio-based and fibre-reinforced thermoplastics, are examined. The evaluation model consists of a point system in which the materials are evaluated according to various weighted criteria. For the technical evaluation, the tensile strength, the surface of the fractures from the tensile test and the dimensional accuracy of the specimen are examined. Thus, especially the examination of the fractures under the scanning electron microscope, provide additional information about the results in the tensile test. For the economic evaluation, the materials are assessed using criteria such as the required manufacturing time, the purchase costs of the materials and the wear of the nozzles. The evaluation of the ecology is carried out with the help of considerations of the CO₂ footprint of the production, biodegradability and reusability. Based on the evaluations, three two-dimensional strength diagrams were developed, from which the results of the materials, on two of the areas in each case, can be read. These results are combined in a three-dimensional diagram. This representation offers the possibility to carry out a precise selection of biobased or recycled materials for AM on the basis of the three evaluations carried out.

217 166 Numerical investigation of 3-D auxetic meta-material for highperformance concrete Sharma N1 , Kumar Yadav K1 1 Indian Institute Of Technology (bhu), Varanasi, India Advancement in additive manufacturing has triggered research in artificially engineered material that possesses unique behavior. 3D Auxetic meta-materials are emerged as a promising lightweight material with high energy observation, shear stiffness, fracture toughness, and fatigue life. In particular, negative Poisson’s ratio behavior is the key behind all these extreme properties which are not found in materials naturally. The novel architectural geometry enables materials to possess theses unique behaviour. The present study investigates the potential of auxetic meta-material in concrete structure for the confinement of concrete. This study proposes a novel approach for the next-generation confinement of concrete structures using 3D auxetic meta-materials. Selected auxetic architectures are numerically optimized for the different range of re-entrant angles. The strut diameter and size of the lattice structure are kept such that the relative density of the lattice structure in the mortar matrix does not exceed 5%. The behavior of IPC (interpenetrating phase composite) that made by 3D auxetic meta-materials and plan concrete) is compared with plan mortar matrix. The result of this study is very promising. It shows IPC has significantly high strength compared to a plain mortar. Further, high ductile behavior is also observed in the IPC with increased in residual strength. These findings demonstrate the high potential of the auxetic lattice structure to induce high ductility and strength in concrete. Auxetic unit-cell consists of three sets of struts with a diameter 1 meter. Unit-cell is auxetic in Y and X-axis when unidirectionally compressed along Z-axis.

218 167 Innovative Additive Manufacturing of Biomimetic 3D Constructs for Enhanced Impact Energy Dissipation Michailidis N1 , Maliaris G2 , Argyros A1 , Smyrnaios E1 1Aristotle University Of Thessaloniki, 2 International Hellenic University The study aims to explore the potential of additive manufacturing, particularly selective laser sintering (SLS) with polyamide material, to fabricate complex and biomimetic 3D constructs using Voronoi tessellation algorithms. Voronoi tessellation is a mathematical method of dividing space into regions, often used in computational geometry and computer graphics. The resulting 3D constructs have a high level of porosity and unique geometric patterns, resembling natural structures found in bones, shells, and other biological materials. To evaluate the impact absorption capabilities of these constructs, the researchers conducted impact tests and used finite element method (FEM) modeling. The FEM modeling provided valuable insights into the fracture behavior and material responses of the 3D constructs, particularly their dependence on strain rates. The results showed that the constructs with 80% porosity and a strut radius of 0.5 mm demonstrated significant impact energy dissipation. This resulted in a reduced peak force transmission and a smooth deceleration process, indicating that the constructs are capable of absorbing impact energy effectively. The findings highlight the potential of additive manufacturing to create complex and biomimetic 3D constructs with unique properties that can be tailored for specific applications, such as impact absorption in the automotive and aerospace industries. (a) FE model developed to simulate the response of material at high strain rate impact and (b) the accelerated impact test apparatus employed in the investigations.

219 The measured (a) Force - Time and Displacement - Time histories, as well as the derived (b) Force - Displacement history for specimen 1 .

220 168 Investigation of the damping capacity of stochastic lattice structures Sarafis E1 , Stamkos A2 , Maliaris G1 , Kavafaki S1 , Mitridis V1 1Greece International University, 2 INTERMEK S.A. This paper presents the design and experimental verification of 3D printed stochastic lattice structures to enhance the mechanical vibration isolation properties of a robotic milling support. Stochastic lattice structures can be found in living beings such as butterflies, beetles and other insects as biologically optimized surfaces for different focuses. Stochastic lattice structures can be optimized not only for geometric but also mechanical requirements by tuning parameters. The structures are investigated by focusing on the combination of material, geometry and strut thickness with the highest production potential. Structures have been studied in a wide and feasible range depending on the change of parameters directly affecting modal behavior such as mass and stiffness. The current work investigates the possibility of designing stochastic 3D structures employing the Voronoi tessellation technique, which can easily be incorporated in the design of critical components that require vibration damping in a lightweight design. A generative algorithm has been developed, using the add-on Grasshopper of the CAD software Rhinoceros. The results showed enhanced damping characteristics related to the structure geometry and the used materials. Based on these results, lightweight vibrations damping structures can be incorporated into the mechanical fixtures of robotic milling. Work financially supported by project No ΑΜΘΡ7-0074871 within the frames of "Funding of Innovation Plans" at East Macedonia and Thrace Prefecture

221 169 Capturing additively manufactured composites behavior by digital image correlation technique Franulovic M1 , Markovic K, Gljuscic M 1University of Rijeka, Faculty Of Engineering INTRODUCTION Materials used in additive manufacturing technology possess a diverse range of mechanical characteristics and thus have a vast range of applications. Hence, it is justifiable to investigate the behavior of the most commonly used materials in current product development trends, which can be based on similar principles of modeling, testing, and simulation for validating their performance. Despite this, low-quality parts and inadequate mechanical properties compared to conventional production methods restrict the application of additively produced polymers in engineering practices. Defects such as voids and poor interlayer bonding, are direct outcomes of the production process, leading to the overall degradation of mechanical properties. However, the influence of these defects can be reduced by incorporating fibers into the polymer matrix, thereby resulting in significantly stronger and more robust composite structures. Considering various possibilities in reinforcing these materials, it is important to assess methods and techniques applied to testing the produced specimens in order to justifiably use them for mechanical properties determination. METHODOLOGY Digital image correlation is a widely-used non-contact technique for measuring the full-field deformation and strain of materials under load. In the field of behavior modeling for additively manufactured continuous fiber reinforced thermoplastic composites, it provides valuable information on stress-strain relationship and consequently for characterizing its mechanical properties. Measuring the deformation of the material under different loads enables the development of appropriate constitutive models that can be incorporated into finite element simulations to predict the material's behavior in real-life applications. RESULTS Experimental results have been acquired on additively manufactured specimens, using the digital image correlation technique. The specimens underwent static testing to assess the feasibility and reliability of the employed data acquisition method. Tests were performed on standard specimens with different fiber orientations. Material behavior was recorded and evaluated during the loading and unloading stage. CONCLUSION As the use of additively manufactured composite materials becomes increasingly prevalent due to their customizable properties, there remains a significant amount of unknowns and uncertainties in the field. These uncertainties pertain to both testing methodologies and data collection techniques. This study explores the use of the digital image correlation technique in tensile testing on additively manufactured specimens, demonstrating its viability and effectiveness through the obtained results. This work has been supported by Croatian Science Foundation under the project number IP-2014-09-3607 and by University of Rijeka under project number uniri-tehnic-18-34.

222 170 Peening based surface treatments for post-processing of additive manufactured AlSi10Mg alloy Bagherifard S1 , Maleki E1 , Heydari Astaraee A1 , Guagliano M1 1Politecnico Di Milano Additively manufactured materials using laser powder bed fusion (LPBF) technology primarily suffer from a rough and defective surface, and peening treatments are found to be a helpful post-processing technique to reduce their surface roughness. Recently, a novel process called gradient severe shot peening (GSSP) was introduced as a novel version of the severe shot peening (SSP) process that enables further enhancement in fatigue strength while reducing the risk of over peening. In this study, experimental and numerical finite element model are developed to investigate the effects of GSSP process applied to the as-built AlSi10Mg alloy processed by LPBF. Two variants of the process with ascending (ASSP) and ascending-descending (ADSSP) peening Almen intensity were considered. The numerical results in terms of the induced residual stresses and the surface roughness were compared successfully to the experimental data, confirming the validity of the proposed numerical approach. The model is believed to be an efficient tool in designing postprocessing GSSP treatments aimed at addressing the shortcomings of additive manufacturing techniques regarding surface quality.

223 171 Cold spray depositions of Multi-Principal Element Alloys – Sprayability and Characterization Kumaravel M1 , Ardeshiri Lordejani A1 , Bagherifard S1 , Guagliano M1 1Politecnico Di Milano Multi-Principal Element Alloys (MPEA)/Complex Concentrated Alloys (CCA) are manufactured with high concentrations of different principal elements (three or more elements at 5 to 35% of molar concentrations of each element). These alloys are reported to possess better thermos-mechanical properties such as high specific strength, high hardness, high wear resistance and oxidation resistance at high temperatures., which makes them a favorable candidate for a wide range of applications. Thermal spray (TS) techniques, such as High velocity Oxy-Fuel or Atmospheric Plasma Spraying are generally considered suitable to deposit these alloys. However, incase of such high temperature methods, the feedstock is melted, leading to the recrystallization of particles. This results in changes in the properties and behavior of the deposits. Recent studies have proposed Cold Gas Dynamic Spray (CGDS) as a viable method for depositing MPEAs. Cold Spray can also be considered as a technique to additively manufacture these complex alloys, without degrading the feedstock properties. in Cold Spray, particles are not heated significantly, hence avoiding melting, inflight oxidation, and any temperature-dependent phase transformations. Many elemental combinations and aspects of CS depositions of MPEAs are yet to be investigated. This research is focused on employing CS for the deposition of MPEAs (specifically high and medium entropy alloys). For each of the two investigated MPEA, a series of wipe tests and full depositions (covering the entire substrate) were carried out. The wipe test specimens were inspected to investigate the effect of the hardness of the particle and substrate and the deformation of the particle and substrate to understand the particle-substrate interface bonding. Full depositions were done to assess the sprayability, the optimum spraying parameters, and to estimate the deposition efficiency of CS for each MPEA. Optical observations and metallographic analyses were performed on the deposits to examine the morphology and to investigate the thickness, porosity and interparticle bonding. The results indicate the potential of CS to deposit MPEA, avoiding the limitations posed by other TS techniques. CS parameters along with the tailor-made MPEA feedstock composition and properties can help us attain deposit properties, similar to the feedstock.

224 172 FATIGUE TESTING OF A LIGHTWEIGHT COMPONENT MADE OF ADDITIVELY MANUFACTURED ALUMINUM ALLOY Nicoletto G1 , Uriati F2 , Fortese G1 , Riva E1 1University Of Parma, 2BEAM-IT Near-net-shape components of complex geometry that achieve outstanding lightweight targets can be produced by additive manufacturing (AM). However, a key issue in the widespread industrial acceptability of AM is the structural integrity of lightweight components when subjected to dynamic loading conditions. Therefore, in-depth knowledge of the fatigue behavior of the metal part obtained typically by the laser powder bed fusion (L-PBF) process under the combined effect of stress gradients, residual stresses, surface roughness and process-induced internal defects is required. Recently an integrated workflow for the development of lightweight metal AM part was presented in [1]. The initial phase included the DfAM approach in part selection, i.e. a lower suspension arm, followed by topological optimization of the original geometry and AM process simulation. The AlSi10Mg alloy, which is characterized by high strength-to-weight ratio, good fatigue resistance and proven L-PBF processability, was the selected metal. Fig. 1 shows the lightweight part geometry characterized by intricate surfaces with notches and reentrant corners that affect the structural response. After the initial design phase, the additive manufacturing phase consisted in processing gas atomized AlSi10Mg powder in a L-PBF SLM 500 system (SLM Solution GmbH - Germany) using qualified process parameters defined by the AM service company Beam-It, (Beam-It SpA, Fornovo Taro, Italy). Noteworthy among them were layer thickness of 50μm, build plate temperature of 150°C and the energy density of 32.62 J/mm3. Fig. 2 shows multiple parts built with their long axis nearly vertical (i.e. parallel to the build direction to minimize supporting lattices. A direct aging treatment (i.e. 200°C for 4 hrs) was applied to the parts still on the build platform to optimize strength vs. ductility and to partial release of residual stresses due to fabrication. After removal from platform, the parts were sand-blasted and the three circular holes visible of Fig. 1 were ground for precise coupling with the testing rig. The last phase of the workflow, that is the experimental qualification of this structural part by fatigue testing, is detailed in this contribution, the aim being the generation of a documented data set that links a known complex part geometry and well-defined boundary conditions to crack initiation location of a part and the corresponding number of cycles. The high cost and limited number of aluminum components available motivated the development of three test configurations for each component. This resulted into about twenty high cycle data for three different loading conditions of the optimized part. In all cases cracks originated at points of stress concentration on the sand blasted surface. These data are used as reference for the discussion of fatigue assessment procedures applicable to L-PBF AlSi10Mg parts. Acknowledgement Project funded under the National Recovery and Resilience Plan (NRRP), Mission 04 Component 2 Investment 1.5 – NextGenerationEU, Call for tender n. 3277 dated 30/12/2021, Award Number: 0001052 dated 23/06/2022.

225 Selected references [1] Nicoletto G., Riva E., Uriati F., “Lightweight Design and Additive Manufacturing of a Fatigue-Critical Automotive Component,” SAE Technical Paper 2022-37-0026, 2022, doi:10.4271/2022-37-0026 Fig. 1 Lightweight part geometry (length approx. 200 mm) Fig. 2 L-PBF AlSi10Mg parts on build platform

226 173 On the Effect of Load Ratio on the Fatigue Behaviour of C45 Steel Foti P1 , Milone A2 , Filippo S3 , Landolfo R2 , Berto F4 1Department of Mechanical and Industrial Engineering, Norwegian University Of Science And Technology, 2Department of Structures for Engineering and Architecture (DiST), University of Naples “Federico II”, 3Manufacturing Systems Development (MSD srl), 4Department of Chemical, Material and Environmental Engineering (DICMA), Sapienza University of Rome Steel mechanical components are often subjected to repeated cyclic loadings in presence of significant mean stresses owing to their peculiar destination of use, e.g., in case of mechanically fastened joints. Moreover, the typical complexity of both components (e.g., due to threading) and applied load histories makes it crucial to find reliable fatigue assessment techniques for such parts. Within this framework, in the present paper, the influence of load ratio on the fatigue behaviour of both smooth and notched mild steel (C45 grade) components is preliminarily investigated by means of experimental tests, refined numerical analyses and further data drawn from literature, i.e., considering variable load ratios (up to R = 0.9) and multiple specimen geometries. Fatigue data are initially interpreted through established literature models to account for mean-stress effect. Finally, an attempt to uniquely explain experimental outcomes is performed through a numerical application of the Strain Energy Density (SED) method.

227 174 Wear and Friction Behaviour of Additive Manufactured PEEK under Nonconformal Contact Z. M. Shukur 1 , Lin G2 , Chen Y2 , Kukureka S3 , Dearn K1 1The University of Birmingham, School of Engineering , 2University Of Hertfordshire, School Of Physics, Engineering And Computer Science, 3The University of Birmingham, School of Metallurgy & Materials This investigation aimed to study the wear and friction failure mechanism of laser sintered polyether- etherketone 3D printing (EOS PEEK HP3). The main objectives included to conduct wear and friction tests under non-conformal contact, to monitor surface temperature, to carry out surface characterization with microscopy and SEM. A rolling-sliding test rig was employed. Tests were carried out on an EOS PEEK HP3 specimen running against a steel disc unlubricated, with various slip-ratios under a contact pressure of 56 MPa, 48 MPa and 39 MPa respectively. Both wear and friction were measured. The results have shown that both friction and wear were increased with an increase of either slip-ratios or the contact pressures, exacerbated by high surface temperatures. It has also been observed that both friction and wear failures were associated with the degradation of the non-conformal contact surfaces due to crystallinity changes that correlated well with working conditions. Using microscopy it was found that such failures as pitting, fatigue and surface cracking were affected by the surfaces in contact, including the degree of melting of the surface. The failure mechanisms of EOS PEEK were observed on the contact surfaces, included surface melting and contact fatigue failures particularly with the more severe high slipratios, and the high contact pressures conditions. The findings of this investigation have the potential to help to design & develop additive manufacturing EOS PEEK HP3 products. Typically, these results can be used in conjunction with the design process and can aid in the development of more effective, the highly contacts at a polymeric gear system.

228 175 Atomic-scale grain boundary engineering for crack-free additively manufactured superalloys Antonov S4 , Després A2 , Vad O1 , Mayer C3 , Martin G2 , Kontis P1 1Norwegian University Of Science And Technology Ntnu, 2University Grenoble Alpes, CNRS, Grenoble INP, 3Aubert et Duval, 4Max-Planck-Institut für Eisenforschung GmbH Additive manufacturing (AM) has a great potential in the production of novel engineering components for aerospace and power generation applications, where nickel-based superalloys are predominantly used. However, grain boundary strengthening solutes, such as carbon, boron and zirconium, are a double edge sword. On one hand their presence in the bulk chemistry is of utmost importance for achieving the required mechanical performance at elevated temperatures, while on the other hand they promote hot cracking at grain boundaries during additive manufacturing processes. Thus, a better understanding of the segregation behavior of these elements during AM is needed in order to produce crack-free AM superalloys. In this study, the role of carbon, boron and zirconium on the hot cracking susceptibility of a polycrystalline superalloy produced by laser powder bed fusion is investigated. In particular, the compositional evolution of the grain boundaries from the as-built to the fully heat treated condition was studied. For this purpose, transmission electron microscopy (TEM) and atom probe tomography (APT) was used. Although initially the grain boundary solutes segregate at the grain boundaries in the as-built state, after heat treatment zirconium was found to partition instead at the main strengthening precipitates. The absence of zirconium at the grain boundaries had no impact at the creep properties. Boron and carbon were also found to partition at dislocations in the as-built material, which may impose changes in the partitioning of solutes at solidification cells and may potentially play a role on minimizing hot cracking by trapping boron at dislocations. These observations allow us to suggest design guidelines for crack-free and creep resistant superalloys produced by additive manufacturing, which will be presented and discussed.

229 176 Crystal plasticity modeling of lamellar deformation in bimodal Ti-6Al-4V under mechanical fatigue Tang K1 , Zhao Y1 , Ferro P2 , Berto F3 1 School of Aerospace Engineering and Applied Mechanics, Tongji University, 2Department of Engineering and Management, University of Padova, 3Department of Chemical Engineering Materials Environment, Sapienza University of Rome Fatigue failure of titanium alloys has long been an important issue of focus in material design and engineering practice. Particularly, the fatigue performance of dual-phase titanium alloy with the characteristic of lamellar is strongly correlated with microstructural details, as well as inevitably existing micro-defects. This work aims to focus on the effect of lamellar microstructure on the mechancial fatigue performance of bimodal Ti-6Al-4V alloy, highlighting the microstructural feature of grain size distribution. A crystal plasticity finite element modelling (CPFEM) approach has been adopted to analyze fatigue beahviours in bimodal Ti-6Al-4V with distinctive lamellar features, addressing the respective effects of microdefect, material anisotropy and crystal orientation. Based on an improved Voronoi tessellation (VT) diagram method, we are able to mathematically establish microstructurally robust representative volume element (RVE) models with a normal/Gaussian distribution of grain size. A strategy of tuning the lamellar grain orientation is further proposed to investigate the mechanical response/deformation of RVE model with prefabricated elliptical micro-defects. Numerical results indicate that variation of lamellar grain orientation significantly affects the fatigue performance of the bimodal titanium alloy of Ti-6Al-4V. Parameter of θ is defined as the angle between the lamellar grain orientation and loading direction. It is found out that the most pronounced fatigue accumulation strain occurs at θ=30° in single lamellar grain for all varieties of grain size distributions. However, severe plastic deformation is appreciably distributed at an angle of 20° in aggregated lamellar grains. Results further demonstrate that more plastic deformation occurs within the range of 20° to 45° for all the cases, reflecting the microstructure anisotropy in dual-phase Ti-6Al-4V. Moreover, the parameter of aspect ratio turns out to be effective in demonstrating the size effect of elliptical micro-defects on fatigue performance. The aforementioned findings are consistent with experimental observations in published literatures, efficiently overcoming the challenge of quantitative characterization of microstructural lamellar that experiments are short of. Our proposed modelling strategy is demonstrated to be effectively describing the microstructural details in bimodal titanium alloys, potentially offering reference for the design of alloy materials with similar microstructures. Keywords: lamellar microstructure, Gaussian distribution, grain size, fatigue, bimodal Ti-6Al-4V

230 177 High-cycle fatigue performance of hierarchically porous titanium scaffolds produced by additive manufacturing and its possible improvement by gas nitriding Slámečka K1,2, Kashimbetova A1 , Tkachenko S1 , Gejdoš P1 , Pokluda J 1,2,3, Montufar E1 , Čelko L1 1Brno University of Technology, Central European Institute of Technology, 2Brno University of Technology, Faculty of Mechanical Engineering, 3Alexander Dubcek University of Trenčín, Faculty of Special Technology The present contribution discusses recent experimental findings that metallic scaffolds with porous strands produced by additive manufacturing can provide the benefits of improved high-cycle fatigue resistance. In particular, in pure titanium scaffolds with continuous internal strand porosity fabricated by direct ink writing (Fig. 1a – porous, green pore), the fatigue crack growth across the strands is significantly slowed down due to crack branching and meandering. With the additional benefit of smaller grains, which reduced the crack growth rate of short cracks, the hierarchically porous scaffolds endured much longer than scaffolds with compact strands (Fig. 1b) [1]. Furthermore, the preliminary results on additional improvements in fatigue performance of hierarchically porous titanium scaffolds by gas nitriding are introduced. This thermochemical treatment produces a hard surface layer consisting of a very thin and brittle compound layer and an extensive subsurface diffusion zone (Fig. 1c), which harbours the residual compressive stresses expected to extend the crack initiation period. References [1] Slámečka, K. et al. Fatigue behaviour of titanium scaffolds with hierarchical porosity produced by material extrusion additive manufacturing. Mater. Des. 2023, 225, 111453. Acknowledgments This work was supported by the Czech Science Foundation under project number 23-07879S. (a) Intrastrand pores shown in different colours. (b) Fatigue behaviour in compression. (c) Nitriding (1100 °C, 2 h) produced the case with a thickness of 1/10 of the diameter.

231 178 Fatigue threshold estimation of as-built surfaces of Ti6Al4V alloy specimens based on equivalent crack models Meneghetti G1 , Rigon D1 , Coppola F1 1Department Of Industrial Engineering - University Of Padova Introduction The fatigue behaviour of metallic parts produced by AM basically suffers from two main process-inherent factors. The first is the presence of defects, while the second is the rather poor as-built surface finish. One of the challenges associated with the fatigue characterization of metals produced by Additive Manufacturing (AM) techniques is to find the relationship between the standard surface parameters that characterize their as-built surfaces and the resulting fatigue strength. Methods The fatigue thresholds can be estimated by means of fracture mechanics approaches using, for instance, the Atzori Lazzarin Meneghetti (ALM) model, which requires to identify a properly defined equivalent crack model capable of representing the fatigue behaviour of the as-built AM surface. Recent findings show that the best fatigue-related parameter must capture the deepest valley of the rough surface, which in turn can be more easily detected using non-contact 2D-areal measurements (returning the Sv parameter) than using 1D-profile methods (returning the Rv parameter). Results and Conclusion This investigation compares the estimations of the largest pit depth of an as-built surface obtained by applying the Extreme Value Statistics (EVS) to the measurements of the Rv and Sv parameters. Both measurement methods were used to calculate an equivalent crack size to be used with the ALM model to estimate the constant amplitude fatigue thresholds of additively manufactured Ti6Al4V alloy specimens subjected to push-pull fatigue test with as-built surface. Different hypotheses were adopted to define the equivalent crack size. Both Rv and Sv measurements provided a comparable estimate of the maximum pit depth by using EVS and eventually a good agreement between the experimental and theoretical fatigue thresholds was obtained.

232 179 MICROSTRUCTURE AND FATIGUE BEHAVIOR OF A HIGH STRENGTH ADDITIVELY MANUFACTURED AL-CU ALLOY Nicoletto G1 , Fortese G1 , Varmus T2 , Konecna R2 1University Of Parma, 2University of Zilina Aluminum alloys are of particular interest for the insertion of AM in sectors such as automotive and aerospace because they are characterized by high strength-to-weight ratio and good fatigue resistance. Al-Si alloys, such as AlSi10Mg and AlSi7Mg are already widely used in critical applications, [1]. However, high strength Al-Cu alloys, such as the well-known A2024, show a tendency to hot tearing during solidification and poor mechanical properties when additively manufactured from gas atomized powder,. Recently, Elementum 3D introduced the Reactive Additive Manufacturing (RAM) patented technology that made A2024 alloy with the addition of 2 % by weight of nucleation ceramic nanoparticles compatible with laser powder bed fusion (L-PBF). The resulting fine equiaxed grain structure generated upon solidification is associated to mechanical properties comparable to traditionally wrought alloy. Although the latest 2022 Formula 1 Technical Regulations, FIA (2021), specifically includes the A2024-RAM2 alloy for the fabrication of structural parts for the motorsport sector, there are no published fatigue data besides the company data sheet. Therefore this contribution reports an investigation of the fatigue behavior of Al2024-RAM2 produced according to L-PBF process recently qualified for serial production. The preliminary material characterization and the fatigue test program was carried out on specimens manufactured along different building directions using patented Elementum 3D powder in a SLM 280 HL Twin system (SLM Solutions GmbH, Germany) qualified for serial production by Beam-It (Beam-It, Fornovo Taro, Italy). After printing using a nominal layer thickness of 60 µm, the material underwent a solution-plus-aging heat treatment (T6) to achieve optimized mechanical properties (i.e. rupture strength Rm = 497 MPa; yield strength Re = 384 MPa and elongation to rupture E = 10 %) while greatly reducing residual stresses. The microstructure was characterized by optical microscopy after metallographic preparation. The roughness of as-built surfaces oriented in the different directions was determined with a profilometer. Various sets of miniature specimens were subjected to cyclic plane bending under a load ratio R = 0 to reveal the directional fatigue behavior of Al2024-RAM2. The miniature specimen geometry was proposed in [2] with the goal of reducing the amount of material and overall production and testing costs. The as-built directional fatigue behavior is rather isotropic, differently from previous observations in directly-aged L-PBF AlSi10Mg for the same specimen orientations. A significant improved fatigue behavior after with surface polishing was also determined and compared to company datasheet data. Acknowledgement

233 Project funded under the National Recovery and Resilience Plan (NRRP), Mission 04 Component 2 Investment 1.5 – NextGenerationEU, Call for tender n. 3277 dated 30/12/2021, Award Number: 0001052 dated 23/06/2022. Selected references [1] Gu, T., Chen, B., Tan, C. and Feng, J., 2019, Microstructure evolution and mechanical properties of laser additive manufacturing of high strength Al-Cu-Mg alloy, Optics & Laser Technology, Vol. 112, pp. 140-150. [2] Nicoletto, G., 2017., Anisotropic high cycle fatigue behavior of Ti–6Al–4V obtained by powder bed laser fusion, International Journal of Fatigue 30

234 180 A review of the use of the Theory of Critical Distances to perform the uniaxial/multiaxial fatigue assessment of notched 3D-printed metals Susmel L1 1University Of Sheffield - Dept of Civil & Structural Engineering The Theory of Critical Distances (TCD) is the name which has been given to a group of design methodologies that all make use of a material length scale parameter to post-process the local linear-elastic stress fields in the vicinity of the crack initiation locations. The aim of the present investigation is to review the accuracy and reliability of the simple linear-elastic TCD in predicting fatigue strength of notched components made of 3D-printed metals. The accuracy and reliability of the TCD in estimating the fatigue strength of additively manufactured (AM) is assessed against a large number of experimental results generated by testing, under both uniaxial and bi-axial cyclic loading, AM notched specimens containing different geometrical features. Based on this systematic reanalysis, the TCD is seen to be highly accurate, its usage resulting in estimates falling mainly within the parent material calibration scatter bands. This result is certainly very relevant since it demonstrates that the linear-elastic TCD can be used successfully to design against fatigue loading notched components of AM metals by directly post-processing the results from simple linear-elastic Finite Element (FE) models.

235 181 Probabilistic defect-notch interaction assessment of AM materials under size effect Niu X1,2, Berto F2 , He J1 , Zhu S1 1University Of Electronic Science And Technology Of China, 2 Sapienza University of Rome Basic fatigue properties captured by fatigue tests of small specimens are often applied to safety design of actual components due to costly and time-consuming full-scale fatigue tests. Nevertheless, their fatigue performances are significantly different due to size effect attributing a fault to statistical defect and the stress concentration induced by complex geometry such as a notch. In order to achieve the fatigue property transferring from laboratory small testing to actual components, in this study, firstly, extreme value statistics is applicable to deal with size effect and fatigue scatter from statistical perspective. Then, the stress state of notched specimen is simulated by finite element analysis, together with the K-T diagram, the allowable defect size of critical region is presented. Finally, a defect-tolerance interface model is proposed and the quantile of the derived largest defect is implemented to estimate failure possibility of notched sample. Especially, the final failure site location for a complex AM structure can be predicted based on the probabilistic defect-notch interaction, which enable the systematic evaluation and design standardization of AM metallic materials. Keywords: Extremum value statistics; size effect; defect-notch interaction; AM materials; defect tolerant

236 182 Fatigue Behavior of Miniaturized Ti6Al4V Lattice Structures: Investigating the Influence of Building Orientation and Stress Ratio for Improved Design and Manufacturing of Biomedical Devices Murchio S1,2, Maniglio D1,2, Rigatti A1 , De Nart L1 , Luchin V3 , Benedetti M1 1Department of Industrial Engineering (DII), University of Trento, 2Biotech Research Center, University of Trento, 3 Lincotek Medical Metal additive manufacturing (MAM), specifically Laser-Powder Bed Fusion (L-PBF), has opened up new possibilities for the design and production of complex architected-cellular structures that were previously unattainable with traditional subtractive techniques. This has led to the creation of a new generation of components with customized shapes and tailored functionalities, particularly in the biomedical field, where L-PBF of Ti-6Al-4V has shown significant potential for next-generation prosthetic devices. However, despite these major advantages, the widespread adoption of MAM techniques on a large market scale is still hindered by concerns about the structural integrity and fatigue strength of the components. This is mainly due to the complexity of the fatigue phenomenon, and its full understanding in combination with highly irregular and defect-sensitive printed specimens. Therefore, in this study, we aimed to expand knowledge on the fatigue behavior of lattice structures at the component microscale by investigating the behavior of miniaturized specimens that resemble the strut subunit elements under different stress ratios and building orientations. Specifically, we investigated the fatigue strength of four differently oriented specimens, which were printed at 90°, 45°, 15°, and 0° with respect to the building platform, under four different stress ratios (R=0.1, R=1, R=-4, and R=10). We built the Haigh diagram and evaluated different predictive mean stress models, which revealed the strong influence of the mean stress effect on all four inspected batches. Interestingly, we noticed different building orientation trends according to each evaluated stress ratio. The failure analysis of the specimens provided insight into these trends, emphasizing the role of superficial and internal defects on the fatigue failure mechanisms, depending on the stress ratio and building orientation. Additionally, we assessed and evaluated the role of buckling instabilities and the onset prediction in the fatigue life of struts under a compression-compression (R=10) fatigue regime. The results of this work provide valuable information for predicting the fatigue life of Ti6Al4V lattice structures at the miniaturized scale of the struts, considering the manufacturing process and stress ratio. This information is particularly useful for lattice-based prosthetic devices, where the struts may be subjected to either tension or compression, despite the predominance of compressive loads in the overall application. Overall, this study offers important insights into the fatigue behavior of Ti6Al4V lattice structures, which could serve as useful tools for more aware design and manufacturing of future lattice-based devices.

237 183 MULTI-SCALE ASSESSMENT OF MECHANICAL PROPERTIES AND FATIGUE PERFORMANCE OF ADDITIVELY MANUFACTURED NICKEL-BASE SUPERALLOYS Yuan H1 , Zhang T1 , Jin S1 1Tsinghua University In the present work, the microstructures and mechanical properties of additively manufactured IN718 alloy were studied and the dendritic columnar microstructures elongated along the building direction are related to macroscopic mechanical properties. Detailed experiments under both proportional and non-proportional multi-axial loading conditions indicate that the influence of the building orientation from manufacturing on mechanical property and fatigue performance is negligible. Fractography analysis reveals that fatigue crack initiates from carbide and oxygen phases. The shear energy-based models reasonably predict the fatigue life and shear failure is the dominant failure mode for the laser melting material. The SLM specimens exhibit orientation dependence in mechanical properties under uniaxial tension conditions, which is mainly due to the difference of the columnar grain structure in different orientations and the preferential texture with respect to the loading direction. SLM processing of the IN718 alloy results in the formation of a dendrite/columnar microstructure and <001> main texture with grains elongated along the building direction. Fractography analysis reveals that the fracture toughness of SLM material is much lower than that of the forged material, and the carbide and oxide phases are the dominant crack initiation sites. The carbide phase should result from the lack of fusion during the SLM process or insufficient dissolution into the matrix during heat treatment. While the oxide phases should be produced by the SLM process since the tests are performed at room temperature. Surface defects can act as crack initiation sites as well. The fatigue performance of the material shows, however, negligible dependence on the fabrication orientation. Therefore, in uniaxial tensile-compression and torsion fatigue tests, the orientation hardly influences the parameters of the Manson-Coffin model. Fatigue lives under non-proportional loading conditions are significantly lower than those under proportional loading conditions, that is, the fatigue performance of SLM IN718 is sensitive to the loading non-proportionality. The shear strain energy models can precisely predict the multi-axial fatigue lives under complex loading conditions and the deviations are limited within the scatter band with a factor of 3. Therefore, shear failure should be the dominant failure mode of SLM IN718. However, although Liu's tensile virtual strain energy

238 model extremely overestimates the fatigue lives of torsion tests, it is still able to reasonably predict fatigue lives under non-proportional loading conditions. According to the present experimental results, the effects of anisotropic microstructure and nonproportional loading can be described by conventional models without additional modifications. This may be related to the ductility of the nickel-base superalloy. This feature simplified the applications of the SLM material for engineering, but more detailed investigations are necessary to confirm the validation of the purposed fatigue life models and structural integrity design.

239 184 Magnetic High Entropy Alloys for Renewable Electricity Applications: A Comparative Study of Two Fabrication Methods Poulia A1 , Azar A2 , Bazioti C1 , Larsen A1 , Graff J3 , Belle B3 , Carvalho P3 , Janotova I4 , Mikheenko P1 , Gunnæs A1 , Diplas S3 1University Of Oslo, 2Effee Induction AS, 3 SINTEF Industry, 4Centre for Advanced Materials Application SAS (CEMEA) Advanced soft magnetic materials are crucial for renewable electric energy generation towards reducing CO2 emissions. Since, current soft magnetic materials are approaching their performance limit, the field requires the introduction of new materials and novel methodologies. Therefore, under the frame of Magnificent project, we aim to develop soft magnets based on High Entropy Alloy (HEA) materials. During their last years of exploration, HEAs presented a broad range of structures and properties, and found use in multiple structural, magnetic, high-temperature, and oxidation-resistant applications. Due to their unique properties, they also have attracted considerable attention both from academics and technologists. In this work, we report on the fabrication of a FeCoNiAlMn HEA system utilizing two methods; laser metal deposition, an additive manufacturing technique and melt spinning, a rapid solidification process. FeCoNiAlMn was selected as it is a promising candidate for a soft magnet, important for applications in electrical systems, such as power generation and electromagnets. We mostly emphasize on the structural characterization of the produced alloys and their correlation with the magnetic properties. Micro and nanoscale investigation was performed utilizing Scanning Electron Microscopy combined with Energy-Dispersive X-ray spectroscopy and Transmission Electron Microscopy, while the magnetic properties were measured via Vibration Sample Magnetometry. For imaging the magnetic domains, Magnetic Force Microscopy was selected, while a combinatorial method of Electron Backscatter Diffraction and Magnetic Force Microscopy imaging for studying magnetic domain structure in grains of different crystallographic orientations was performed in both fabrication conditions.

240 185 Phase-separated properties based on the multi-technique nanomechanical characterisation methodologies of ferrite and austenite in 2205 duplex and 2507 super duplex stainless steel produced via Laser Powder Bed Fusion Additive Manufacturing Gargalis L1 , Karavias L1 , Koumoulos E2 , Graff J3 , Diplas S3 , Karaxi E1 1Conify, 2 IRES - Innovation in Research and Engineering Solutins, 3 SINTEF - Material Physics - Dept. Sustainable Energy Technology The main objective of this study is to provide insights on the nanomechanical performance of ferrite and austenite phases in Duplex (2205) and Super Duplex (2507) stainless steel processed via Laser Powder Bed Fusion Additive Manufacturing for which limited data exist in literature. Nanoindentation measurements were conducted on three types of samples, 1) as-built samples, 2) stress-relieved and 3) solution-annealed followed by quenching. Light Optical Microscopy (LOM), Scanning Electron microscopy (SEM) and Electron Backscatter Diffraction (EBSD) were employed to identify and quantify the phases present in the duplex microstructure. In order to attain reliable values, nanoindentation datasets combined with statistical analysis are used as a methodology for assessing nanomechanical response, evaluate the mechanical properties of separate constituent phases and provide information about their content and distribution within the system. From the load-displacement indentation curves, a methodology is developed to assess and attribute the variation of nanomechanical properties (e.g., hardness and elastic modulus) to austenite phase and ferrite phase, by comparing our findings with similar reported work of literature. After post-heat treatment operations, the mechanical response of the system is compared with that in the as-built condition. Hardness, elastic modulus values and load-unload curve alterations are correlated with manufacturing aspects, e.g., resulting residual stresses, crystal orientation and lattice rotation effects revealed during nanoindentation testing.

241 186 Coupling of processing parameters to the columnar to equiaxed transition (CET) using a computationally low-cost model for process mapping and high-throughput screening of new alloys in additive manufacturing Reiersen M1 , M'hamdi M1 , Wilberg Hovig E1 , Li Y2 , Du Q1 , Zhang K1 1 SINTEF Industry, 2Norwegian University of Science and Technology (NTNU) Metal additive manufacturing (AM) is becoming a key part of industrial manufacturing, with significant advantages over conventional casting methods especially when it comes to complex geometries. Aluminium alloys are of major interest due to its high strength to weight ratio. Conventional aluminium alloys are designed for processes with significantly lower solidification rate, such as casting and forging. Changes to chemical composition is often required to make the alloys suitable for the challenging processing conditions present in AM. The material selection is limited and the process of developing new materials is slow. This work presents a modelling framework that investigates the relationship between chemical composition, processing parameters and microstructure. Emphasis is put on utilizing computationally low-cost models for the purpose of high-throughput screening. The first part of the framework introduces a continuous moving heat source to melt the material, simulating a moving laser. Information about the temperature gradients and solidification rate is obtained at the two extremes of solidification, the trailing edge at the surface of the melt pool and at the deepest point of the melt. The melt pool characteristics for an alloy is dependent on the processing conditions through initial the substrate temperature, laser power and velocity. Different melt pool geometries can result in solidification defects such as lack of fusion or keyhole pores, which is why this aspect is crucial. The second part of the modelling framework is to couple the melt pool characteristics, temperature gradients and solidification rate for different processing parameters to the columnar to equiaxed transition. Microstructure refinement from equiaxed grain growth is known to improve mechanical properties and weldability, and the transition point for columnar to equiaxed growth can therefore be used as a threshold to separate “good” from “bad” processing parameters. The columnar to equiaxed transition is highly dependent on material composition, and the impact of material alterations can be investigated at varying processing parameters. Understanding the relationship between processing parameters and melt pool characteristics to the material composition and the impact on the resulting microstructure is essential when evaluating the ability to process a potential new alloy. The framework is demonstrated for laser beam powder bed fusion of an aluminium alloy in two distinct cases; i) keeping the chemical composition constant to find a selection of processing parameters that promote an equiaxed microstructure; and ii) by keeping processing parameters constant to find the chemical compositions that expand the window of suitable processing parameters. The models developed in this work investigates the coupled effect of processing parameters and material composition, resulting in a processing map for an alloy with the possibility to investigate the impact of changes in the materials chemical composition.

242 Illustration of the coupled effect of processing parameters and Columnar to Equiaxed transition calculations to create a process map for alloy development

243 187 Optimization approach of DED process to fulfil the requirements on material properties and component performance of water jet impeller Saai A1 , Arbo S2 , Sørli S3 , Dybdahl C2 , Nedreberg M4 1 SINTEF Industry, 2 SINTEF Manufacturing, 3Nordic Additive Manufacturing AS, 4Kongsberg Maritime AS Directed energy deposition (DED) processes have a great potential for ship building industry to reduce the lead time of ship parts. However, ship parts such as propellers and impellers have critical requirements on material's properties and component's performance. To expand the capabilities of DED for critical parts, an optimization approach of DED manufacturing process was developed and demonstrated on duplex-stainlesssteel water jet impeller. The developed approach established relations between DED process and heat treatment, material microstructure, and material integrity, all optimized within the requirements on the component. Manufacturing and qualification testing plans were defined based on the requirements in accordance with the current standard guidelines. The assessments by standard tests, including tensile tests, Charpy impact tests, and bending tests demonstrates that the material and component produced by DED fulfil all the requirements. Corrosion and cavitation tests were also performed and demonstrates the high resistances of DED material to corrosion and cavitation.

244 188 Small fatigue crack growth properties of 316L SS fabricated with Laserbased Powder Bed Fusion process Psihoyos H1 , Lampeas G1 , Polatidis E1 , Sofras C 1 Laboratory of Technology and Strength of Materials, Department of Mechanical Engineering and Aeronautics, University of Patras, 26500 Rion, Greece Laser-based Powder Bed Fusion (L-PBF) Additive Manufacturing is the most used layer-by-layer fabrication method which offers great design and manufacturing freedom. As such, L-PBF is often used for fabricating structural parts with complex geometries which are otherwise challenging to be produced with conventional subtractive manufacturing methods [1-2]. The design freedom that L-PBF offers, for the fabrication of advanced parts that combine high strength with low weight, is attractive for the aerospace, automotive and medical industrial sectors [1]. Despite their advantages, L-PBF processed parts usually exhibit considerable variabilities in their strength or even inferior properties compared to the conventional counterparts, during cyclic loading conditions. The most common cause of this behavior are the process-induced defects. The fatigue properties of L-PBF processed materials are highly affected by the process-induced defects, such as Lack-of-Fusion (LOF). LOF pores have irregular shape and act as crack initiators that propagate until failure [3]. Therefore, the presence of these defects must be controlled in the phase of process design and manufacturing. Damage tolerant design methodologies have been widely used to estimate the fatigue life in a wide range of engineering materials. These methodologies focus mainly on the stable crack propagation of the examined materials. However, due to the small size of defects in the L-PBF processed materials, the small fatigue crack growth behavior is more important, as it can better describe the effect of the microcracks that are most commonly found in L-PBF processed materials [4]. In the present study, both long and small crack behavior of L-PBF 316L SS are experimentally investigated. The long fatigue crack growth experimental testing aims at determining the stable and unstable crack growth regimes. The goal of small fatigue crack growth is to examine the near-threshold region and to determine the crack threshold values of small crack fatigue initiation and propagation. The determined crack growth properties are then used an input for verifying our analytical tools that can predict the presence of defect as well as the fatigue life of L-PBF processed 316L SS. References: [1] Blakey-Milner, B., Gradl, P., Snedden, G., Brooks, M., Pitot, J., Lopez, E., Leary, M., Berto, F., & du Plessis, A. (2021). Metal additive manufacturing in aerospace: A review. Materials & Design 209, 110008. https://doi.org/10.1016/J.MATDES.2021.110008 [2] Du Plessis, A., Razavi, S. M. J., Benedetti, M., Murchio, S., Leary, M., Watson, M., Bhate, D., & Berto, F. (2022). Properties and applications of additively manufactured metallic cellular materials: A review. Progress in Materials Science 125, 100918. https://doi.org/10.1016/J.PMATSCI.2021.100918

245 [3] Sanaei, N., & Fatemi, A. (2020). Defects in Additive Manufactured Metals and Their Effect on Fatigue Performance: A State-of-the-Art Review. Progress in Materials Science, 100724. https://doi.org/10.1016/j.pmatsci.2020.100724 [4] Waddell, M., Walker, K., Bandyopadhyay, et al. (2020). Small fatigue crack growth behavior of Ti-6Al-4V produced via selective laser melting: In situ characterization of a 3D crack tip interactions with defects. International Journal of Fatigue 137, 105638. https://doi.org/10.1016/J.IJFATIGUE.2020.105638

246 189 Exploring the Stress Concentration Factor in Additively Manufactured Materials: A Machine Learning Perspective on Surface Notches and Subsurface Defects S. Azar A1 1Effee Induction AS, Head of additive manufacturing This investigation aims to establish a comprehensive computational methodology for analyzing the effects of notch geometry, subsurface porosity, and their interaction on the structural integrity of metallic components. Utilizing a machine learning algorithm, the study examines the stress concentrators and their statistical significance in determining structural integrity. Previous studies have examined various facets of this methodology, yet this investigation employs a systematic approach to examine all pertinent factors. Results reveal that the notch opening angle does not significantly influence stress concentration, and crack mouth opening displacement is heavily affected by the notch depth, which can limit its usage for studying the growing cracks, especially in the presence of subsurface pores. This study contributes to the understanding of acceptance thresholds and the economic viability of maintenance operations suggested in various governing standards. Stress distribution map under loading of a structure that contains surface notch and sub-surface porosity

247 190 Experimental and statistical investigation on flexural properties of vertically oriented FDM fabricated PLA specimens Fountas N, Papantoniou I, Kechagias J, Manolakos D, Vaxevanidis N 1 School Of Pedagogical And Technological Education (ASPETE) During the last decade, fused deposition modeling (FDM) has emerged as a widely applied additive manufacturing technology for numerous engineering applications. However, the properties of FDM products exhibit strong dependence on process parameters, which may be improved by setting suitable levels during processing. In the present work, the flexural strength of vertically oriented, FDM fabricated specimens made of pure polylactic acid (PLA) is examined in relation to FDM printing parameters i.e., layer height, printing temperature and flow rate. An experimental design was selected to obtain the results for flexural strength and further investigate the effect of each control parameter on the response by studying the results using statistical analysis and response surface methodology. The experiments were conducted according to the ASTM D790 standard. The different failure modes observed during testing correlated with the tested specimens' different printing parameters. The regression model generated for flexural strength adequately explains the variation of FDM operating parameters on flexural strength. Thus, it can be implemented to find optimal parameter settings using artificial intelligence techniques. In addition, the results of the present series of experiments contribute towards the study of the bonding quality between the successive layers of the FDM fabricated parts.

248 191 Improving the mechanical properties of Glass Reinforced Plastics by slight mechanical compression Iakovidis I1 , Dimitrellou S1 , Orfanos G1 , Vlachogiannis M1 1Department of Naval Architecture, School of Engineering, University of West Attica Glass reinforced plastics (GRPs) are composite materials that have been used widely for the past 50 years in engineering constructions and the marine industry. The simplest method of manufacturing GRP composites involves the hand layup process. This is a low cost, easily applied method for built up, maintenance and repair purposes. However, the quality of the outcome often depends on the experience and skills of the technicians involved [1]. Although the core process of the method has remained practically unchanged over time, improvements can be introduced, aiming to reduce variation in the quality of the manufactured product caused by human intervention. The use of other contact molding methods for GRP manufacturing, such as spray layup, injection and pultrusion, is limited due to higher cost and the necessity of specialized equipment [2]. Mechanical properties of the fabricated GRP products depend on the type and arrangement of reinforcement, the type of the plastic as well as the reinforcement to plastic ratio. Some of these factors are interdepended in determining the quality of the final product. In the present work, the influence of applying mechanically a slight pressure on the properties of GRP specimens, fabricated by hand layup methods, was investigated. Specimens with dimensions of 5 cm by 45 cm were constructed by hand layup application of pre-accelerated orthophthalic polyester resin over several layers of chopped strand mat or woven roving E-Glass reinforcement. Each specimen was further processed either by a vacuum bag compression or a mechanically applied pressure of approximately 6 bar. The properties of the produced composite specimens were then determined experimentally. The resin/glass ratio in the fabricated composite specimens was found to vary according to the method of construction. The resin/glass mass ratio of 1.19 in the chopped strand mat reinforced composite fabricated by the hand layup technique was increased to 1.44 when pressure was mechanically applied, while in the woven roving it was increased from 2.42 to 2.90. On the other hand, the resin/glass volume ratio was decreased from 2.44 to 1.53 in the former case and from 0.92 to 0.73 in the latter. The application of mechanical compression enables the production of glass-reinforced composite specimens with double side refined surfaces and was found to improve their properties. The effect of the compression was evident as a 5–10% reduction of the specimens’ internal void volume compared to the non-compressed ones. Consequently, an increase in the density by 9–12% and a reduction in the thickness of the specimens by 15–20% were obtained. Additionally, the tensile and flexural strength of the GRP composite specimens were increased by more than 15% and 5% respectively when pressure was applied mechanically, reflecting an improvement of their mechanical behaviour. References 1. Elkington M., Bloom D., Ward C., Chatzimichali A., and Potter K.; "Hand layup: understanding the manual process", Adv. Manuf.: Polym. Compos. Sci., 2015, 1, 128-141.

249 2. Gascons M., Blanco N., and Matthys K.; "Evolution of manufacturing processes for fiber-reinforced thermoset tanks, vessels, and silos: A review", IIE Transactions, 2012, 44(6), 476-489. Density (a) and Void volume (b) of the fabricated GRP composites. Tensile strength (a) and Flexural strength (b) of the fabricated GRP composites.