bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of data filtering and noise on the calibration of constitutive models using machine learning techniques
Authors: PRATES P.A.
Published: April 2024

Abstract. This work focuses on predicting material parameters that describe the plastic behaviour of metallic sheets using the XGBoost machine learning algorithm, with a dual focus on the influence of data filtering and data noise. A dataset was populated with finite element simulation results of cruciform tensile tests, including strain field data during the test. Different noise levels were added to the strain-related features of the dataset; additionally, a feature importance study was carried out to identify and select the most relevant features of the dataset. A systematic analysis shows how feature noise and selection individually and simultaneously influence the predictive performance of machine learning models. The results show that feature selection will greatly accelerate model training, without losing its predictive performance. Also, adding noise to the features does not have significant impact on model performance, highlighting the robustness of the models.
Constitutive model validity evaluation for MT 2.0 applications
Authors: PESHAVE Amar
Published: April 2024

Abstract. This paper demonstrates a methodology to discriminate between the performances of different material models within the framework of Material Testing 2.0, which consists in coupling heterogeneous test configurations, full-field measurements using for instance Digital Image Correlation (DIC) and inverse identification like the Virtual Fields Method (VFM). The methodology relies on using a set of different virtual fields for parameter identification with a selected model, and to evaluate the performance of the model. The paper illustrates this methodology on anisotropic metal plasticity.
Machinability of PLA obtained by injection molding under a dry milling process
Authors: CLOËZ Liam
Published: April 2024

Abstract. This paper is part of a study focusing on the elaboration of accurate component with complex geometries using bio-sourced as an alternative to petrochemical polymer. The bio-sourced and biodegradable in this study is composed of a Poly Lactic Acid (PLA) matrix and hemp fibers. The final component is obtained by injection followed by a machining operation. the final component is obtained by injection followed by a machining finishing operation. Injection molding will be carried out to be compared with 3D printing on economic, environmental, production and workpiece quality criteria. This paper focuses only on the combination of two processes, injection molding followed by machining on poly (L-lactic acid) or PLLA which is biobased and biodegradable. After injecting the workpiece, thermo-physical characterization tests are realized on PLLA polymer. Rheology, thermal and mechanical tests are carried out in order to study thermomechanical behavior and to understand material flow phenomena at different temperatures and shear rates. The objective of this paper is to overcome the technical challenges of milling this material without any lubricant. In an upcoming project, various machining operations will be carried out such as turning to study continuous cutting, or milling to study discontinuous cutting on workpieces reinforced with bio-sourced fibers as hemp.
Impact of machining strategy on OFE copper for SRF applications
Authors: BELKHIR F.
Published: April 2024

Abstract. The study evaluates the impact of various milling strategies - on the surface and subsurface quality of an Oxygen-Free Electronic (OFE) copper substrate, and subsequently on the niobium (Nb) coating performance- for Superconducting Radio Frequency (SRF) cavities. Several cutting tools, cutting conditions and machining paths are compared, given their paramount influence in the final ‘SRF’ quality of the machined surfaces. The near surface region is evaluated by different means: surface roughness and shape accuracy are measured using a profilometer and Coordinate Measuring Machine (CMM) respectively; the thickness of the layer affected by machining on the OFE copper substrate is estimated by Focused Ion Beam Scanning Electron Microscopy (FIB - SEM). The dislocation density in the near surface layer is assessed by Grazing Incidence X-Ray Diffraction (GI-XRD) in both the OFE copper substrate and afterwards in the niobium coating. Main investigation results are discussed, and conclusions drawn for new guidelines on machining strategy and for future research developments.
Estimation of the residual stress field of laminated aeronautical parts to prevent distortion after machining
Authors: CHAABANI Khayel
Published: April 2024

Abstract. The estimation of post-machining distortion of monolithic aeronautical parts induced by the redistribution of the bulk residual stresses (RS) during machining is one of the major challenges of aeronautical parts manufacturing. Since it is the main cause of thick parts post-machining distortion, it is essential to know the state of the initial RS so that the machining strategy can be modified to minimize distortion of each part. The problem is even more complex because the RS field is not identical from one part to another. Considering an average stress field provides satisfactory results only for parts with simple geometries and a highly repeatable manufacturing process, which is rarely the case in an industrial setting. By simulating the steps of the production of the laminated blank, the variability of RS field will be established. This variability can be used to determine the distribution of the RS field of each part during machining.
Numerical simulation of milling operations on flexible composite parts
Authors: NUTTE Matthias
Published: April 2024

Abstract. Fiber-reinforced polymers (FRPs) are a widely used and growing material in industry, thanks to their excellent mechanical properties. Manufactured FRPs parts usually have thin walls. These parts also require finishing operations such as edge trimming. Problems like those encountered when machining thin metal parts are also encountered with FRPs: form error, chatter vibrations and poor surface finish. However, the study and numerical modelling of thin FRP parts are not well developed up to now. The aim of this paper is to demonstrate the feasibility of adapting a numerical model for metals to FRPs. The modelling of the shape error during the thinning of a CFRP (Carbon Fiber Reinforced Polymers) part is studied in this paper using a quasi-static analysis. Compared to metals, two adaptations are introduced here for the FRPs. First, the material properties are adapted from isotropic to orthotropic. Secondly, a mechanical model was applied to calculate cutting forces for FRPs. The results of the study show the feasibility of this adaptation and examination of form error in the case of FRPs.
Enhancing interfacial bonding strength in fiber metal laminates through metal surface treatments
Authors: Liu Z.
Published: April 2024

Abstract In recent decades, the aircraft industry has experienced a growing need for high-performance, lightweight structures, leading to a significant focus on developing fiber-metal laminates (FMLs). These composites possess various benefits in terms of stiffness, yield stress, fatigue, and high-velocity impact properties due to their hybrid composition. However, certain challenges related to the fabrication, surface treatment, and mechanical properties of these structures require further attention. This paper reviews FML manufacturing with a focus on enhancing the interfacial bonding strength between metal and fiber-reinforced polymer (FRP) sheets by conducting different kinds of surface treatment on metal layers to further enhance the FML mechanical properties.
Applying images processing methods for automation measurement of tool-chip contact length in orthogonal cutting
Authors: FAVIER Camille
Published: April 2024

Abstract. The simulation of machining process is an essential tool in the digitalization of the entire production chain. Currently, these simulations are not sufficiently precise to avoid the use of experimental tests in order to optimize machining operations and guarantee the quality of the machined parts. Some parameters, such as tool-chip contact length, are still underestimated, although they are critical for controlling heat transfer into the tool and implicitly its wear. In order to validate a numerical cutting simulation model, the tool-chip contact length experimentally measured should be used as a comparative quantity, in the same way as the cutting forces and the morphology of the chips is currently used. The objective of this paper is to propose an automation of tool-chip contact length measurements using image processing algorithms. The proposed algorithm was able to identify and measure the tool-chip contact length on more that 75% of images. The algorithm accuracy is evaluated by comparing computed and manually measured tool-chip contact length, for different cutting conditions. It was found that it overestimates the contact length, especially in the case where the image quality is lower.
A numerical approach to investigate the influence of cutting fluid on tool wear in machining AISI 1045 steel
Authors: METHON Grégory
Published: April 2024

Abstract. The proposed work presents the development of a numerical model to take into account cutting fluids when turning of an AISI 1045 steel with a TiN coated tool. At this stage, the study considered the impact of a cutting fluid only based on its thermal properties and ability to reduce friction. Three heat exchange scenarios were explored: dry machining (h = 20 W.m-2.K-1), use of a straight oil lubrication with low pressure (h = 200 W.m-2.K-1) and cooling with an emulsion based lubrication (h = 1000 W.m-2.K-1). Regarding friction, three levels of static friction (µs = 0.3, 0.5 and 0.7) have been considered. Following an analysis of thermomechanical loads (stress, sliding speed, and temperature) exerted on the tool, a Usui wear law was employed for each case to simulate cutting tool wear. Results indicate that friction exerts a significant impact compared to the convection coefficient.
Fatigue resistance of deep drawn parts: A scale bridging simulative study using representative volume elements and crystal plasticity simulations
Authors: FEHLEMANN Niklas
Published: April 2024

Abstract. The mechanical properties of formed components are determined by the interaction between the microstructure and the load path of the forming process. To investigate and understand these effects, micromechanical simulation concepts can be used, such as statistically Representative Volume Elements (sRVE) coupled with crystal plasticity simulations. This study presents a concept that uses sRVE simulations to quantify the influence of three different deep drawing load paths on the fatigue resistance of DP800 steel. The first step is a scale-bridging simulation approach that employs macroscopic simulations of the deep drawing process to extract the boundary conditions for the sRVE simulations with Damask. Subsequent cyclic loading is then simulated. 50 sRVE are computed for each load path to estimate fatigue resistance based on a Fatigue Indicator Parameter. The results indicate that fatigue resistance increases with increasing deformation-induced strain hardening. Additionally, a positive correlation between the martensitic ligament structures and fatigue resistance was observed.
Influence of manufacturing defaults on the behavior of 3D printed lattice structures with a multiscale data-driven approach
Authors: COURT Clément
Published: April 2024

Abstract. The inherent multiscale (MS) complexity of lattice materials necessitates specialized modeling techniques to predict their mechanical behavior accurately and efficiently. A combination of the multiscale finite element method (e.g. FE²), with a Data-Driven paradigm, leads to Multi Scale Data-Driven (MSDD) modeling procedure to simulate the behavior of these materials. On top of the inherent complexity of these materials, limitations of the Laser Powder Bed Fusion (LPBF) manufacturing process result in geometrical imperfections of the manufactured materials giving rise to so called as-manufactured configuration. Furthermore, theses imperfections have significant influence on the mechanical behavior and introduce biases and variance from expected behavior based on the modeling with initially designed lattice material, so called as-designed configuration. The proposed research is the first step in the reduction of the cost of MSDD approach by aligning the model's accuracy with the manufacturing capabilities. The aim is to exploit the inherent variance in as-manufactured lattice material and to minimizing the material database to the essential material state points. To that end, in this work, using X-ray tomography, we create digital twins of various as-manufactured aluminum lattice unit cells and perform a number of simulations. The goal is to get further understanding of the variance in mechanical behavior resulting from geometrical variations and defects. These results will be further used to enhance the efficiency of the MSDD approach with no compromise on predictive capabilities.
Methodology for the automated spatial mapping of heterogeneous elastoplastic properties of welded joints
Authors: HAMILL Robert
Published: April 2024

Abstract. A methodology to map the heterogeneous elastoplastic mechanical properties of welded joints is presented. The approach and results of the proposed methodology are demonstrated using numerical data representing an off-axis butt-weld. This work extends the Virtual Fields Method (VFM) by introducing automated spatial parameterisation of the constitutive parameters. This extension enables the novel characterisation of welds with more complex geometries, loading conditions and dissimilar materials.
Numerical modeling of the compressive behavior of 316L body-centered cubic lattice structures
Authors: RÍOS Ignacio
Published: April 2024

Abstract. With additive manufacturing, innovative porous structures emerge for generating lightweight components with high mechanical responses. Body-centered cubic lattice structures are the focus of this study, with customizable lattice density depending on the strut diameter. To predict the properties of lattice structures and thus reduce the number of tests in experimental campaigns, several numerical and analytical models have been developed. In this work, the elastoplastic response was determined. Buckling phenomena of vertical struts depend on the different boundary conditions applied in Finite Element simulations. As shown the number of cells within the model affects the results. This size effect was quantified for different lattice density cases. The numerical results obtained for lattice structures with different relative density were also compared with the well-known Gibson-Ashby model.
Mesh sensitivity study in the random cellular automata finite element model of dynamic recrystallization
Authors: SITKO M.
Published: April 2024

Abstract. Predicting microstructure morphology evolution under hot forming conditions and determining final material properties are essential for optimizing metal-forming processes. Cellular Automata (CA) is a widely employed full-field method for modeling microstructure morphology changes during various metal-forming processes. However, at higher temperatures and under conditions of substantial microstructure evolution, the CA method encounters limitations related to computational domain geometry changes. The use of random cellular automata (RCA) offers a more realistic representation of this phenomenon, although it requires additional effort in algorithm optimization for acceptable execution times. This paper contributes to an overarching research effort focused on developing a discontinuous dynamic recrystallization model (DRX) by directly incorporating RCA into the finite element (FE) framework. Different mesh sizes and their impact on the quality of the results are analyzed, and the minimum number of elements that do not degrade the results in the CA model are selected. The investigation aims to enhance the practicality of the proposed model, striking a balance between realistic microstructure representation and computational efficiency.
Eigenstrain method in simulations of laser peen forming of curved surfaces
Authors: POLTL Dominik
Published: April 2024

Abstract. The eigenstrain ansatz allows for the efficient simulation of large-scale applications of Laser Peen Forming (LPF) while being subject to geometric constraints. A setup to investigate the viability of the method for non-uniform curvature is proposed. A small-scale laser processing is simulated on cylinder shells of given curvature. Eigenstrains are determined in representative cells and mapped onto a second cylinder shell with different curvature to simulate a large-scale processing operation. The eigenstrains result in changes in local curvature. This is repeated for four curvatures. The resulting data is used to investigate the dependence of the induced curvature change on the origin geometry of the eigenstrains. A determined regression relation provides insight into the feasibility of the eigenstrain ansatz beyond its constrains.
Novel approach for reducing thinning during forming of foil metal
Authors: MEERKAMP Max
Published: April 2024

Abstract. The mobility sector is one of the largest contributors to greenhouse gas emissions in the European Union. One approach to reduce these emissions and thereby reach the climate goals set by the European union is the use of alternative drive concepts, such as the hydrogen fuel cell. The economic feasibility of the hydrogen fuel cell depends on its performance which is mostly determined by the volumetric flows of reactants conveyed within the cell. In this context, the key component is the bipolar plate, as its channel depth defines the volumetric flows of reactants. The channel depth is, however, limited by the formability of the material being used and the occurring sheet thinning during forming. This paper presents a novel approach of segmental forming, meaning the forming of individual channels in a defined sequence. The aim is to reduce local stress concentration in the component and to homogenize the spatial thinning within the component in order to avoid a pronounced local sheet thinning. Therefore, five channels are formed by conventional forming in a single step and by segmental forming. The results are then analyzed in terms of the thinning of the sheet thickness that occurs and conclusions are drawn in terms of the stress states that occur.
Recycling of thermoset fiberglass by direct molding of ground powders
Authors: BELLISARIO D.
Published: April 2024

Abstract. Fiberglass production in western Europe exceeds one million tons per year, and data of the European Commission inform that at their end-of-life, 25% of waste fiberglass is sent to landfill. Being a thermosetting material, it polymerizes during its production, when a molecular network is generated into the matrix. This network is responsible for its optimal properties, but it prevents the material ﬂow under heating and thus reprocessing. A new recycling process for fiberglass waste has been proposed by the authors without any use of virgin materials or additives. This technology consists of a direct molding (i.e., compression molding) of pulverized fiberglass. The material agglomeration depends on the combination of several mechanisms, from residual reactivity, to powder re-activation and incipient degradation during molding. Residual fiberglass powder has been recovered from a factory that specializes in technical laminates, where a grinding process is used to provide the expected tolerance to the products. The recovered powder has been direct molded to manufacture small samples for mechanical testing. Such powder shows thermal activation in the DSC (differential scanning calorimetry) at low temperature (about 80°C). This study shows the feasibility of recycling waste fiberglass without using any virgin material; these new findings are related to the use of industrial powders, their testing under 4-point bending and the obtaining a good, molded surface.
Process analysis using adapted Rogowski coil for non-conventional processes
Authors: DARAWISH Haytham
Published: April 2024

Abstract. The process analysis of non-conventional processes is very complex because many critical subprocesses can occur. These subprocesses can be determined among other things, by their positive and negative current increases. A process adapted Rogowski coil is particularly suitable for analyzing the current increases. Using the example of plasma electrolytic polishing, it will be shown how pulse typical effects can be distinguished from process typical effects. The boundary condition for this development was that the size of the measuring sensor had to be adapted to the system conditions of the plasma electrolytic polishing process. It was not necessary to calculate the real current, but rather to recognize the process situation very quickly. For this purpose, a higher signal amplification must be carried out during the polishing process and the initialization phase must be hidden. The example of experimental test setup shows, which analyzes can be carried out. The influence of the process disruption on the result can also be determined through comparisons with the processed final results.
Manufacturing of shape memory foams in hypergravity and simulated microgravity
Authors: SANTO L.
Published: April 2024

Abstract. Shape memory polymer (SMP) foams have the potential to be used in space application for self-deployable structures and actuators. For this reason, shape recovery tests have been performed in microgravity, but these foams have been never manufactured in space, because of experimentation costs and flight opportunities. Some foams have been manufactured on-Earth in a random positioning machine (RPM) and a large diameter centrifuge (LDC) under different conditions with the aim of understating if the gravity can play a role during foaming. Foams have been characterized by 3D micro-Computed Tomography (micro-CT) and the effect of the foaming condition on the foam structure is discussed in this study. For the first time, it has been observed that SMP epoxy foams produced by solid state foaming present open porosity with a negligible contribution of closed pores. Moreover, it is confirmed that SSF foams is minimally affected by the gravity conditions apart the contribution of the gravity vector on the heat transfer conditions during foaming.
Analysis of thermal behavior in 3D printing of continuous fiber reinforced polymer composites
Authors: LI Shixian
Published: April 2024

Abstract. Fused filament fabrication (FFF) as an additive manufacturing process, is a thermal driven method used to produce continuous fiber reinforced composites for engineering applications. Interlayer delamination is a significant concern for composites manufactured by FFF process. To address the problem of interlayer delamination and enhance the macro-mechanical properties of FFF fiber composites, it is necessary to study the thermal behavior of continuous fiber filled composites during the deposition process. A thermal simulation model with the consideration of continuous fiber was proposed. The numerical simulations reproduce the trends of experimental temperature evolution. When the continuous fiber phase is omitted from the heat transfer model, the predicted reheating temperature at the interface is lower compared to the temperature measured via IR monitoring. This result highlights the critical necessity of developing a numerical model that takes the continuous fiber phase into account in order to accurately predict the reheating temperature at the interface. Such a model is essential for deeper exploration into the adhesion mechanisms between adjacent layers and adjacent filaments.
Experimental and numerical investigation of the light scattering of the 3D printed parts
Authors: NGUYEN Thi-Ha-Xuyen
Published: April 2024

Abstract. Anisoprint is a forefront technology in the realm of 3D printing and has ushered in a transformative era in composite material fabrication. The synergistic fusion of Anisoprint's 3D printing technology with laser transmission welding has enabled the creation of complex structures featuring carbon fiber reinforcements along all three spatial axes. This innovative amalgamation empowers the production of components distinguished by their unparalleled strength and precision. In the pursuit of this objective, the integration of transparent thermoplastic windows within 3D-printed components has been employed as conduits for laser beams during the welding process. Nevertheless, the interaction between laser beams and these transparent windows introduces a phenomenon characterized by beam diffusion, primarily attributed to the intrinsic porosity inherent in the 3D printing process. Within the scope of this study, an in-depth examination of laser beam diffusion within 3D-printed carbon fiber components is undertaken. This endeavor encompasses the application of micro-tomography to meticulously construct a comprehensive mesh representing the microstructural intricacies of the transparent section. Leveraging this mesh, ray tracing simulations are conducted to elucidate laser beam behavior. Subsequently, a comparative analysis is conducted between these numerical outcomes and experimental observations, involving the scrutiny of laser beam photographs as they traverse the printed component. This research aspires to enhance our comprehension of the intricate dynamics governing laser beam interactions within Anisoprinted structures. Ultimately, this will contribute to the refinement of laser welding processes and foster the advancement of more efficient and dependable manufacturing methodologies for composite materials.
Evaluation of thermal properties of PEEK samples made by MEX
Authors: Spina R.
Published: April 2024

Abstract. The work studies the Polyether ether ketone (PEEK) specimens realized with the material extrusion (MEX) process, evaluating thermal material properties for potential application for polymer heat exchangers. The research investigates the influence of infill density on the thermal properties of PEEK components. A specific instrument measured PEEK specimens' thermal conductivity, thermal diffusivity, and specific heat. The procedure initially required a two-point calibration with references in the investigated ranges, followed by measurement with variable-filled specimens from sparse (20% infill) to full (100% infill). The results indicate that a decrease in the infill value causes a positive reduction in the thermal conductivity and specific heat. In contrast, the diffusivity remains stable with the infill variation.
Preliminary investigation of the energy consumption in friction stir welding of aluminum alloys
Authors: COZZOLINO E.
Published: April 2024

Abstract. Manufacturing is responsible for significant emissions and energy consumption. However, several manufacturing processes, especially the non-conventional ones, are still poorly investigated from a sustainable perspective. Friction Stir Welding (FSW) is a non-conventional solid-state welding process developed in the last decade which can produce joints with higher mechanical and metallurgical properties. Very few studies exist in the literature on the FSW from a sustainable perspective, so this paper aims to fill this gap of knowledge. Following the in-depth approach of CO2PE! procedure, the power profile of the machine overall the process has been investigated to carry out time and energy studies. The main factors affecting electrical energy demand in the FSW process are highlighted and guidelines for decision-making from an energy-saving perspective are released.
Finite element analysis and life cycle assessment for CFRP laminates in marine applications
Authors: GENTILI S.
Published: April 2024

Abstract. The present study focuses on structural analysis of a moth structure realized in carbon fiber reinforced polymers (CFRPs) prepreg laminates. A finite element method analysis was performed to investigate the flexural strength of different laminations and to identify the optimal layering. Moreover, a Life Cycle Assessment (LCA) analysis was conducted to evaluate the environmental impacts of the moth structure obtained using innovative processes and to compare them with those resulted by the same structure realized with manual composite processes. The results demonstrated the higher sustainability of the innovative process than the traditional one (335.75 eq. vs 228.22 kg CO₂ eq.). This research is part of the project NAUTILUS, in which Università Politecnica delle Marche and Cetma Composites are involved, that aims to develop, test and validate new processes for composite materials in nautical applications, with respect to environmental sustainability.
Improvement of the surface quality of titanium-based design objects produced through WAAM technology using chemical machining: A preliminary study
Authors: PERNA A.S.
Published: April 2024

Abstract. The quality of the surface is one of the most important factors in the fabrication of a component via additive manufacturing (AM). In particular, when considering the manufacture of workpieces in titanium and its alloys the successful use of surface treatments is essential. In fact, many fracture-related events, in particular fatigue cracks, start near the surface of the component. Numerous techniques based on machining, shot peening, or laser polishing have been proposed to enhance the surface quality. The limitations of these treatments stem from the challenges posed by focusing on complex form components. One of the most promising approaches for achieving homogenous smoothing of intricate objects with internal channels and lattice structure continues to be chemical-based surface treatments. It is a pivotal method to remove material that has been polluted by oxygen during processing. In this instance, the resistance to crack initiation and fracture is fundamentally improved by the removal of a hard, brittle top layer. In this work, HF/HNO3-based treatment tailored for 3D printed design products is presented.
Real-time in-situ thermal monitoring system and defect detection using deep learning applied to additive manufacturing
Authors: RHIM Safouene
Published: April 2024

Abstract. Fused deposition modeling, a widely employed additive manufacturing method, has witnessed a significant trend towards printing advanced materials such as PEEK and PAEK in recent years. Research studies have demonstrated the significance of process thermal dynamics in influencing the mechanical and geometric properties of printed components. This paper introduces a real-time thermal monitoring system that comprehensively tracks the thermal history of the printed component. Additionally, a deep learning model is presented, capable of detecting defects during the printing process. The integration of this monitoring system in a closed-loop mode offers the advantage of real-time adjustments, facilitating an immediate enhancement in the quality of the printed parts based on the continuously measured thermal data and the identified defects. Beyond real-time improvements, the data output from the monitoring system holds immense potential for broader applications. It can be seamlessly integrated into simulation software, providing a valuable dataset that can be leveraged to predict the physical properties and the adhesion quality of the printed parts.
Improving precision in the cavity thickness measurement for fabric compaction
Authors: SOUSA Pedro
Published: April 2024

Abstract. As seen in the first international compressibility benchmark, inaccuracies in the fabric stack thickness measurement, the approach to compliance correction and the non-parallelism between compaction plates resulted in highly inaccurate compression curves. The factors influencing the accuracy of thickness measurements in compaction tests were studied to provide a comprehensive guidance and measurement recommendations to improve upon the current procedures and enhance the accuracy of thickness measurements. These include the variability in the direct thickness measurements due to accuracy of the laser sensors measurements and the variability in the machine compliance measurements. In conclusion, while both thickness measurement methods yielded comparable results, it is noteworthy that the direct method exhibited greater variability in thickness measurements compared to the indirect method, which rely on the machine displacement. Minor changes in the rig's displacement or in the orientations between compaction plates due to differences in the pressure distribution during compaction, combined with other sources of variability such as external interferences or vibrations from the compaction plate led to variations in measurement´s accuracy throughout the tests.
Forming of thermoplastic polymer and magnesium alloy-based fiber metal laminates at elevated temperatures
Authors: Liu Z.
Published: April 2024

Abstract. This paper illustrates the thermoforming process carried out on thermoplastic polymer and magnesium-based fiber metal laminates (FMLs). Flat laminates were formed at elevated temperatures into a hat-shape part. The forming force was acquired and, after forming, the thickness of each constituent of the FMLs in different zones was measured. A non-uniform thickness distribution was found in the formed parts, with a significant reduction of the prepreg thickness at the part bottom radii. Moreover, it was observed that the higher the blank-holder force the higher the forming force and the more significant the prepreg thickness variation.
Polymer-metal interactions and their effect on tool-ply friction of C/PEKK in melt
Authors: GROUVE W.J.B.
Published: April 2024

Abstract. Excessive friction or adhesion between tool and surface ply can lead to processing defects during thermoplastic composite manufacturing. A previous study identified a notable increase in friction or adhesion between a mild steel tool surface and C/PEKK with prolonged dwell time at elevated temperature, a phenomenon that could not be explained by our current understanding. This work presents additional friction and differential scanning calorimetry experiments to demonstrate that the increased adhesion results from polymer-metal interactions that lead to polymer degradation and metal-polymer bonding. These findings underline the importance of tool material selection in both processing and characterization of tool-ply friction.
Effects of UD and twill reinforcements in hybrid sheet molding compound laminates
Authors: RAIMONDI Luca
Published: April 2024

Abstract. This work proposes a novel manufacturing solution to locally reinforce a Sheet Molding Compound (SMC) with continuous fiber prepreg in a single-step compression molding operation. An adapted SMC process allowing for the manufacturing of continuous carbon fiber-reinforced SMC was successfully implemented, and a layer of fabric was added to mitigate the waviness induced during processing. Plates with different stacking sequences were manufactured and used for mechanical characterization to understand the effect of hybridization over tensile and flexural properties. It emerges that hybridization led to a 137% increase in tensile strength and up to 147% rise in flexural modulus compared to the standard SMC baseline. Additionally, the hybridization process helped reduce the variability in elastic and strength properties.
Recent advances in development, characterization and joining of new sustainable materials
Authors: DOINA BANEA Mariana
Published: April 2024

Abstract. Nowadays, in order to increase the transport efficiency and reduce fuel consumption and emissions of contaminants, a reduction in weight associated with improved safety performance of the materials in use must be achieved. On the other hand, environmental concern has generated interest in research about new materials aligned with the principles of sustainability. Thus, this need for better performing and ecological structures has resulted in the development of a new variety of materials. Among these materials, currently, are the composites produced from resources of renewable sources. Natural fiber composites have recently attracted a great deal of attention by the industry due to their many attractive benefits (e.g., high strength-to-weight ratio, sustainable characteristics and low cost). Welding is highly impractical to use in these situations (i.e., thermoset polymer composites) and rivets or screws exhibit stress concentrations and offer a low fatigue resistance. Adhesive bonding is usually the preferred method since it allows for greater flexibility in design and is more efficient in mechanical and energy aspects. In this work, recent advances in development, characterization and joining of new sustainable materials, critical challenges and future perspectives are presented. The application of sustainable green composites may further increase in many structural and non-structural applications if their joining behavior is well-known and established.
Automatic planning strategy for robotic lay-up of prepregs on a complex-shaped mold
Authors: GAMBARDELLA A.
Published: April 2024

Abstract. The evolution of composite component production has been driven by a constant quest for improvements in process efficiency, precision, and repeatability. The eventual transition from traditional hand layup to robotic layup represents a significant step in this evolution. The implementation of robotic layup systems has become increasingly prevalent in the manufacturing industry, particularly in the aerospace and automotive sectors, where lightweight, strength, and precision are mandatory requirements. Ideally, the goal is the development of processes where a highly precise robotic arm could automate the deposition of composite materials onto the mold, providing a certain reduction of human errors, and minimizing material waste and associated costs. In this context, this paper proposes a computational tool that is able to provide automatic layup planning for the robotic layup process. The implemented algorithm incorporates the knowledge of a professional laminator: it can automatically analyze a generic mold surface of complex shape, work out the correct strategies for lamination, and generate instructions for robot movements.
Transverse squeeze flow of fibre reinforced thermoplastic composites
Authors: BIELEMAN Gerben
Published: April 2024

Abstract. Transverse squeeze flow is one of the deformation mechanisms that govern the forming of molten fiber reinforced thermoplastic composites. It is typically described by a transverse bulk viscosity, dictating the resistance against the flow of the combined constituents. In this work, the squeeze flow method was used to characterize the transverse viscosity of carbon fiber reinforced low-melting PAEK at three different compression rates. The experiments were recorded with a camera and the video images were analyzed to obtain the flow fields. A power law fluid model was fitted to the logged data, but found to be unable to describe the material behavior at all compression rates. Moreover, the video analyses indicated discrepancies between the observed specimen deformations and those predicted by the model. Future studies need to focus on the description of the squeeze flow behavior of UD C/LM-PAEK by different models (viscous, viscoelastic), using video-captured deformations for numerical fitting of the models.
Investigating TP-AFP process parameters through a mechanical testing approach
Authors: IANNONE Vincenzo
Published: April 2024

Abstract. The present work investigates a non-standard approach for tuning TP-AFP process parameters, employing an in-house-designed setup for CF/PEEK ring coupons production and mechanical testing to assess interlaminar shear strength (ILSS). The TP-AFP setup features a laying head based on hot gas torch heating source, controlled pressure on a compaction roller, IR thermal monitoring, all operated by a six-degrees-of-freedom (DOF) robotic anthropomorphic arm. Through a non-standard split-disk setup, ILSS is thus evaluated, with its relation with key process parameters such as laydown speed, pressure, and temperature investigated. Although there is a high scatter level of the mechanical characterization parameters of the specimens, the analysis highlights how there is a direct dependence between the AFP process parameters - especially the temperature - and the ILSS values calculated through the split-disk testing carried out.
Modeling time-dependent anisotropy in MEX component-scale process simulation
Authors: DI NARDO Mario Emanuele
Published: April 2024

Abstract. In this paper, a numerical method is proposed to consider the transient anisotropic orientation state of a material extruded (MEX) part during a macroscale process simulation. To enhance computational efficiency, multiple filament strands are considered within single finite elements. The model is constructed around the utilization of 4th order orientation tensors, obtained by combining the information of the nozzle toolpath and the mesh elements in accordance with the process time. This provides a dynamic mapping of the anisotropic material orientation state within each element, in real-time to the process trajectory. Through the integration of time-dependent orientation tensors, this research provides deeper insights into filaments alignment evolution during the MEX process. This advancement not only enhances predictive capabilities in process simulation but also streamlines computational demands.
Surrogate model to describe temperature field in real-time for hot forging
Authors: MIDAOUI Aya
Published: April 2024

Abstract. In the context of certain metallic alloys, the conformity of the product depends on its metallurgical structure. Addressing this, the implementation of a real-time monitoring system to control the evolution of the metallurgical structure and the geometry of the cogging part is proposed. Focusing on the microstructure's dependence on temperature, this article outlines the requested steps for developing data-driven reduced models for describing the temperature field in the billet. These models use temperature data collected from predictive numerical simulations conducted using FORGE® software. Applying the Proper Orthogonal Decomposition (POD) technique, the images illustrating the temperature field are reconstructed through a 2D matrix-based framework. This matrix, derived from non-discretized elements issued from FORGE®, underwent discretization through an objective method, resulting in a size of 100*100. The utilization of the POD technique in this approach provides a parametric vector description, facilitating rapid image reconstruction through manipulation of vector system parameters. With just two vectors, we can effectively reconstruct the image representing the temperature field.
Effects of Co ratio on fatigue life of WC-Co die inserts used in cold forming operations
Authors: HIZLI Burak
Published: April 2024

Abstract. Production of fasteners via cold forming requires high forming forces, which induce significant stresses in dies. Therefore, die performance becomes a critical parameter of the fastener production process. Estimation of die life with high accuracy allows to enhance production efficiency and reduce die-related expenditures. Generally, WC-Co hardmetals consisting of 4-30% Co content as a binder are highly preferred in cold forming operations. WC-Co metal-ceramic composite materials offer high wear resistance against frictional forces, high compressive strength, and lower elastic deformation to resist excessive contact pressures, which are primary requirements for cold-forming dies. In this study, experimental investigations were conducted for the determination and comparison of fatigue performance at three different stress amplitudes, utilizing three-point bending fatigue testing with two different grades of WC-Co hardmetals. After the experiments, Goodman-Haigh diagrams were obtained from the experimental results to be utilized in predictive die-life calculations.
Influences of die shape and calibration strokes on surface near residual stresses of rotary swaged steel tubes
Authors: LANGSTÄDTLER Lasse
Published: April 2024

Abstract. Forming processes offer a great potential to make production more sustainable by including both the shaping of the geometry and the improvement of the material properties. Through a better understanding of the decisive influencing factors on the resulting material properties of the part, this potential can be particularly exploited and leads to the chance of shortening process chains by e.g. saving heat treatment steps. The part properties during rotary swaging can be improved by strain-induced residual stresses. Thereby, compressive residual stresses can increase the resistance to fatigue fracture, to crack propagation and to corrosion. However, rotary swaging of tubes can lead to undesirable residual tensile stresses at the surface with high fluctuations. Therefore, a better understanding of the rotary swaging process and the actual material flow is necessary. The aim is to realize compressive residual stresses with low fluctuations. Thereby, it is of interest to be able to set residual stresses independently of the desired workpiece geometry. In this paper, rotary swaging of E355 steel tubes (Ø20 mm x 3 mm) was carried out with two different process adaptions. These two adaptions are the number of calibration strokes and the die geometry. They show different influences on surface near residual stresses.
Diversity and Potential Analysis of Liquid Biopesticide Bacteria for Fusarium sp. Control of Shallot -Basal Rot
Authors: Aini Nur , Suharjono Suharjono
Published: April 2024

Shallot base rot disease (Allium cepa L.) caused by the fungus Fusarium causes many crop losses, thus control efforts are required. Microbial biopesticides are used as an alternative to control pests and plant pathogens that are environmentally friendly and target-specific. This study aims to evaluate the diversity of liquid biopesticide bacteria and their potential to control the Fusarium sp. pathogen of shallots. This study includes shallot sampling, isolation and purification of liquid biopesticide bacteria, liquid biopesticide antifungal test, double culture antagonistic test of bacterial isolates against Fusarium sp., and identification of potential bacterial isolates based on 16S rDNA sequence similarity. The results showed that 2 bacterial isolates B7 and B2 had the highest Importance Value Index of 94.21% and 90.59% respectively, with a bacterial diversity index of 1.44. Liquid biopesticide microbial biomass has a high inhibition zone in the antifungal test against Fusarium sp. with an average inhibition zone of 6.45 mm. Bacterial isolate B2 has the highest potential inhibition of 71.3% against Fusarium sp. and was identified as Genus Serratia with a similarity value of 96.79%.
Negative polarity environments in the spontaneous speech of Dutch individuals with aphasia
Authors: Jonkers Roel
Published: April 2024

In the current study, I will investigate the production of negative polarity items and especially the context in which they occur in a group of 10 non-fluent speakers with Broca’s aphasia and compare these with those of a group of 10 fluent speakers (diagnosed with either anomic aphasia or Wernicke’s aphasia) and 10 control speakers in spontaneous speech. Although especially non-fluent speakers do have problems in producing grammatical sentences, it has been shown that negation seems to be spared in these speakers. In contrast however to the large number of negations produced by the aphasic speakers, the number of negative polarity environments was strikingly low as compared to the control speakers in this study. Although not all individual control speakers used such environments, this clearly contrasted the number of cases of such environments in the group of control speakers.