bluuebunny/crossref_metadata_2025 huggingface dataset:
Impact of self-heating during hot deformation in the post-dynamic recrystallization and grain growth of an Fe-based superalloy
Authors: POTENCIANO Antonio
Published: April 2024

Abstract. During hot working, strain rate, strain level and the temperature of deformation, and hence the Zener-Hollomon parameter, become the regulatory thermomechanical parameters of the resultant stored energy value and distribution. An accurate estimation of the aforementioned parameters is thus required to control microstructural homogeneity in the post-dynamic state, since stored energy value and distribution directly affects post-dynamic recrystallization and grain growth mechanisms. In order to do so, the self-heating phenomena that becomes significant at high strain rate hot deformation must be taken into consideration. In this work, several cylindrical samples of the A-286 alloy are submitted to hot compression tests performed in a Gleeble 3500 machine. The microstructure in the deformed-state is analyzed at the center, and the effect of the thermomechanical parameters of hot deformation on the resulting microstructure is discussed. In addition to this, the local thermomechanical testing conditions are estimated considering self-heating and local strain level and strain rate fields. Hence, the relationship between these newly estimated parameters and the microstructure can be assessed.
Modelling ductile damage of a textured aluminum alloy based on a non-quadratic yield function
Authors: BRITO João P.
Published: April 2024

Abstract. The development of more sophisticated constitutive models is essential for improving the reliability of metal forming process simulations. The main objective of this work is to employ a Gurson-type [1] porous criterion to assess the ductile damage distribution of a strongly textured AA5042-H2 sheet during a single-stage cup-drawing process. The anisotropy of the dense phase is described with the non-quadratic form of the CPB06ex2 [2] criterion using two linear transformations. In line with Gurson’s homogenization theory, the plastic behavior of the porous solid is described by an approximate macroscopic strain-rate potential (SRP) using the classical Rice and Tracey trial fields. The particularity of this implementation is that the macroscopic potentials are not evaluated via analytical functions, but by numerical integration of the local fields [3]. It is shown that such approach is viable from the computational standpoint and opens the door for materials with intricate plastic behavior to be modeled within the framework of porous media.
Effect of micro-plasto-hydrodynamic lubrication on strip surface in steel cold rolling
Authors: ELHAJJ Cynthia
Published: April 2024

Abstract. This study employs numerical calculations based on the micro-plasto-hydrodynamic lubrication (MPHDL) theory to analyze the evolution of oil pits during the stainless-steel cold rolling process. The model is enhanced by incorporating lubricant temperature variations caused by its contact with the heated roll and strip, as well as variations in pit slope. The findings show the significant impact and relevance of considering these additional parameters in assessing the performance of the MPHDL mechanism. Notably, the model demonstrates good agreement with experimental measurements conducted on a Stainless-Steel grade undergoing multiple passes.
In-process tool pose measurement in incremental sheet forming
Authors: TERLAU Marina
Published: April 2024

Abstract. Robotic incremental sheet forming is flexible, but involves significant forming path deviations, demanding an in-process tool pose measuring system. To achieve a 50 µm positional and 0.05° orientational measuring uncertainty, a triangulation system using multiple shadow imaging sensors is proposed. LEDs with different wavelengths are attached to the tool holder and cast a shadow of the sensor’s mask though a color filter on the camera chip behind it. The LED position is obtained by processing the shadow images of at least two sensors. Conducted experiments demonstrate that the filters effectively separate the shadows, ensuring cross-sensitivities as low as the random error of measuring a single LED position. The unpredictable scatter in the systematic error dominates the LED position measurement uncertainty. However, a Monte Carlo simulation shows the feasibility of achieving the required uncertainty for tool pose measurement.
Experimental and finite element investigation on the effect of process parameters in incremental forming of polymeric materials
Authors: RAGAI Ihab
Published: April 2024

Abstract. The purpose of this paper is to conduct finite element simulations of the incremental forming process of polycarbonate material. The process was simulated using the commercial software LS-Dyna. An explicit loading-implicit unloading approach for springback was set up, reproducing the experimental conditions. The shell element type and the number of integration points along the thickness were defined through a preliminary numerical approach. A spiral 3D surface was generated and measurements of cone geometry were conducted. The model was validated by comparing experimental and numerical thickness in a cross section, and finally used to investigate the effect of step size on the process mechanics. It was found that a decrease in step size would yield to a more uniform thinning along the profile cross section and produces larger thickness reduction.
Processing of sheets made of long fibers reinforced plastics by SPIF
Authors: Ambrogio G.
Published: April 2024

Abstract. The flexibility of the Single Point Incremental Forming (SPIF) has been exploited in processing of sheets made by fiber reinforced polymers. Indeed, polymer-based sheets are always more employed in product planning, meeting the increasing demand of lightweight structures. However, considering the SPIF features, especially the need to totally clamp the formed sheet along its edges, processing of long-fiber reinforced sheets is critical owing to the brittleness of the fibers, whose length must be preserved. The SPIF dynamics of a customized process solution to be used for long fibers reinforced thermoplastics (LFRTPs) were already proposed and analyzed by FE simulations. Herein, the design of the equipment that allows the process to be executed was proposed detailing it in each part. In particular, the idea was based on assembling a working room that was designed to be able to control both: a) the desired process temperature maintaining it constant during the whole forming step looking at the glass and melting point of the polymeric matrix; b) a hydrostatic pressure on the bottom side of the sheet to guarantee its proper shaping. Moreover, numerical simulations were also executed to locally analyze the forming behavior of the sheet at changing of some specific properties.
Formability analysis of incrementally hole-flanged parts using different tool sizes
Authors: BORREGO-PUCHE Marcos
Published: April 2024

Abstract. This contribution analyses the formability of incrementally hole flanged parts using different tool radii (10, 20 and 47.9 mm). The smallest radius (10 mm) can induce full incremental benefits in the hole-flanged specimen, whereas the biggest one generates a formability behaviour closer to a conventional press forming. In the first case, the necking process is clearly delayed, being the development of a fracture in the middle of the wall flange the mechanism that controls the failure of the specimen. In contrast, in the second case, failure is governed by the appearance and development of a neck at the edge of the flange, which ends in material fracture. The intermediate tool radius (20 mm) shows midway features between a conventional and a fully incrementally formed specimen. The location and fracture mode of the flanged parts with different tool sizes are experimentally analysed and discussed within the Forming Limit Diagram (FLD) using the optical strain measurement system ARGUS®.
Heat-assisted single point incremental forming of Mg-Zn-Zr alloy
Authors: OZDEN Ecem
Published: April 2024

Abstract. Magnesium-zinc-zirconium (Mg-Zn-Zr) alloys, with their biocompatibility and biodegradability, exhibit great potential for biomedical applications. However, forming complex geometries poses a challenge due to the low formability of magnesium. Single Point Incremental Forming (SPIF) has emerged as a promising rapid manufacturing technique capable of producing complex-shaped, high-quality products. This preliminary study aims to investigate the feasibility of heat-assisted SPIF for Mg-Zn-Zr alloys, addressing formability at elevated temperatures, and the outcomes in terms of geometrical accuracy and material properties. Systematic parameter variations revealed that elevated temperatures and multistage toolpath strategies significantly improved formability, surpassing a 60° maximum wall angle. Nevertheless, this enhancement led to increased surface defects and reduced strength during forming at elevated temperatures. The key finding highlights the need for a balanced combination of elevated temperature and maximum wall angle to optimize surface quality and strength in complex geometries.
Form-based manufacturing of aluminium and steel auxiliary joining elements as the basis for an efficient joining operation
Authors: Borgert T.
Published: April 2024

Abstract. Reducing the weight of vehicles can significantly lower the energy or fuel consumed and thus the emissions during operation. One possibility to assess this is the use of a property adapted multi-material systems containing high strength steel, light metals like aluminium or magnesium and fibre reinforced plastics. While expanding the number of materials used new challenges arise for the production and furthermore the joining technology to manufacture the vehicle made of the multi-material systems. One approach to overcome these challenges is to use innovative and adaptable joining techniques which allows the manufacturing of joints of different material combinations. Extensive research activities on the two stage thermo-mechanical joining process with adaptable joining elements was able to demonstrate the great potentials in terms of joining dissimilar materials with good strength. The previously kinematic and path-based fabrication of auxiliary joining elements is modified in this publication to a form-based approach with a perspective of establishing an efficient process chain using easily and cheaply available rods. Based on the new approach to produce the auxiliary joining elements, it can be demonstrated that a reproducible production of the geometry is possible for the investigated steel as well as aluminium material.
Assessments of staked hybrid joints made by studs 3D printed at different manufacturing conditions
Authors: CONTE R.
Published: April 2024

Abstract. The integration of polymers and metals in engineering applications has led to the development of hybrid joints that combine the distinct advantages of both materials. The staking process is a manufacturing technique, which involves the joining or the securing components through the controlled deformation of materials. It involves forming a permanent and strong connection by reshaping or displacing material, often using force or pressure without the need of additional fasteners, like screws or adhesives. This study presents a comprehensive experimental analysis of a specific hybrid joint performed by staking and by using a polymeric 3D printed partner and a steel plate. The influence of the printer machine and the related printing speed on the joint strength is discussed and the findings demonstrate a strong correlation between this variable and the mechanical properties of the hybrid joints.
An experimental investigation into tribological behaviour of additively manufactured biocompatible Ti-6Al-4V alloy
Authors: MADEJ Marcin
Published: April 2024

Abstract. Additive manufacturing techniques are increasingly being utilized in industrial-level applications due to their flexibility and ability to produce customized parts, such as various types of biomedical implants. However, the conditions during additive manufacturing fabrication and the nature of these processes can lead to implications on the properties of the produced parts, potentially requiring appropriate post-processing before real applications. The tribological behavior of printed parts not only affects their performance but also their service life, making it crucial to investigate their wear rate and friction coefficient under different lubricant environments. In this study, an experimental investigation was conducted on as-printed Ti-6Al-4V specimens to determine the effect of various lubricant environments on wear rate and friction coefficient. The results demonstrated that the reduction in wear rate in liquid environments can be significantly hindered by the accumulation of debris from the worn specimen. However, the development of a thin film of an appropriate lubricant was shown to be favorable regarding the friction behavior of printed parts.
Heterogeneity of strain and texture inside roll-bonded multilaminates
Authors: HANON Guillaume
Published: April 2024

Abstract. This study demonstrates the usefulness of crystal plasticity modeling and crystallographic texture analysis when aiming to understand through-thickness strain heterogeneity after roll bonding of dissimilar materials. FE modeling was used at two length scales to study the deformation and texture heterogeneities inside a 9-layer multilaminate made of aluminum and steel, produced by roll-bonding. Microstructure and crystallographic texture were probed using EBSD. Numerical predictions indicated that plane strain compression was accompanied by significant shear parallel to the rolling plane and inclined shear banding in aluminum. Predictions of the Texture development were more accurate in the bcc phase than the fcc phase.
Identifiability analysis of material identification using nonlinear VFM
Authors: STARMAN B.
Published: April 2024

Abstract. The success of inverse material model identification depends on the interaction between the adopted material model, the design of the heterogeneous specimens, the quality of the full-field measurements and the employed inverse identification method. Although inverse identification with full fields usually uses either FEMU or nonlinear VFM algorithms, a range of specimen designs and heterogeneity indicators have been proposed to assess the quality of the measured field and specimen design. While many studies investigate the effects of strain field heterogeneity on material model identification, few of them address the comprehensive interaction of all the above features and investigate their interactions during inverse identification through identifiability analysis. In this study, we analyze the identifiability of the parameters of the YLD2000-2d model used to describe the plastic anisotropy of steel sheet DC04 using a perforated biaxial specimen with the nonlinear VFM method. For this purpose, we performed a virtual DIC experiment with known material parameters by simulating the test in ABAQUS/Standard, generating synthetic images and reconstructing the strains via stereo DIC. Before inverse identification with a nonlinear sensitivity-based VFM, we analyzed the sensitivity of the virtual work to parameter changes and performed an identifiability analysis.
Numerical and experimental studies of molten pool phenomena influence on dissimilar materials coatings by L-PBF
Authors: JACQUOT Amaury
Published: April 2024

Abstract. Over the past few years, Laser Powder Bed Fusion (L-PBF) has become increasingly popular, as this method enables energy and material savings during the manufacturing process. 3D L-PBF parts, based on computer-designed geometries, are generated layer by layer using laser energy. Since the beginning of these studies several decades ago, significant progress has been made in the understanding of additive manufacturing, particularly with regard to properties, structure and in situ monitoring. However, the scientific manufacturing community has yet to achieve optimal operational reliability. Presently, numerous defects remain a major problem for parts produced by L-PBF. These defects are mainly caused by the movement of the molten material and its rate of solidification within the melt, which is also influenced by the thermal phenomena of the process. In the L-PBF manufacturing process, the main challenge is to control the complex interdependence of these phenomena [1]. The aim of this work is therefore to study the various physical aspects during a Laser Powder Bed Fusion (L-PBF) process. For this purpose, it is necessary to provide a numerical model with specific works on experimental characterizations of materials at high temperature (up to 1000 °C) as a model’s input parameters, such as the thermal or optical properties of cobalt based powder (CoCrMo) used in our study. In addition to material characterization, theoretical model studies have been used to determine the thermal properties of L-PBF powder [2], in particular thermal diffusivity. This model is also validated by specific experimental characterizations, involving the dilution of iron substrates in a CoCrMo alloy deposit and temperature measurements during the manufacturing process. Furthermore, the amount of iron transferred from the substrate to the coating can be used as an indicator of the molten metal movement in the melt and, ultimately, of the operating parameters used to apply the coating. Too much iron on the surface impairs the mechanical strength of the substrate-coating assembly, thus indicates poor control of the parameters used for this purpose [1].
Green machining of Ti6Al4V/Polymers composite made by pellets additive manufacturing
Authors: BOSSU Julien
Published: April 2024

Abstract. The poor surface finish (arithmetic roughness Ra around 40 µm) of additive manufactured parts leads to the development of hybrid machines to increase the quality of the final part in a lower production time. Hybrid machine already exists for DED (Directed Energy Deposition) and SLS (Selective Laser Sintering) but due to the hardness and the abrasiveness of the sintered material, important tool wear or surface defects on the workpiece can be observed. Therefore, reduced cutting parameters and dedicated cutting tool must then be used which increase the cost of machining operation and the time to produce a part. Green machining can limit these problems: the machining step is performed before sintering when the part does not have its final properties. This kind of material has a pseudo-plastic behavior so machining can be performed with high productivity thanks to lower cutting forces and reduced tool wear. An innovative use of the tool-material couple standard AFNOR Norm NF E66-520 (1999) dedicated to metals is proposed to determine the cutting parameters of a composite based on titanium alloys Ti6Al4V and polymers by measuring surface roughness and cutting forces. A tool dedicated to thermoplastic polymers was tested. Cutting forces and surface roughness (arithmetic surface roughness Ra and total surface roughness Rt) were evaluated for each test. Twelve sets of parameters considering the cutting speed vc, the axial depth of cut ap, the radial depth of cut ae and the feed per tooth fz as variables were tested. For the range of parameters selected, it is possible to achieve a satisfactory surface finish with low cutting forces (Ra remains close to 3.2 μm and cutting forces < 5 N) and stable results.
Influence of the depth of cut on the AM nitinol properties in flood and cryogenic machining
Authors: GUARISE Alessandra
Published: April 2024

Abstract. Nickel-titanium alloys, commonly called Nitinol, are known for two fundamental properties, namely the shape memory effect (SME) and the superelasticity effect (SE), which make Nitinol a material of great interest for applications in various fields, such as biomedical, aerospace, automotive, and electronics. Most of the published research studies discuss the Nitinol properties after just one step of fabrication, e.g. forming, casting, additive manufacturing (AM), or machining. On the contrary, this work focuses on a process chain including AM followed by heat treatment and both flood and cryogenic machining. In particular, the depth of cut during the last machining step was varied (0.1, 0.25, and 0.4 mm), to investigate its effects on the AM and heat-treated Nitinol in terms of machined surface finish and transformation temperatures. It was found that when cutting with a depth of cut of 0.25 mm, the workpiece shows the worst roughness, regardless of the material microstructure and machining condition. However, for other depths of cut, there is a clear improvement in terms of surface finish. Machining increases the Nitinol transformation temperatures, but changing the depth of cut does not have a significant effect. Cryogenic machining induces a worse surface finish, but has less effect on the transformation temperatures than flood machining.
Fatigue strength of Ti6Al4V titanium alloy machined under flood and cryogenic conditions
Authors: STRAMARE Andrea
Published: April 2024

Abstract. Ti6Al4V titanium alloy wrought round bars characterized by a fine equiaxed microstructure were machined using two different lubrication strategies, namely traditional water-based cutting fluid and liquid nitrogen. Surface integrity after machining was assessed in terms of (i) sub-surface severe plastic deformation layer, (ii) surface topography, and (iii) residual axial stresses as a function of the distance from the machined surface. Finally, the machined specimens were subjected to fatigue tests on a four-point rotating bending machine. For the two sets of specimens, the Wöhler curves were derived to determine their fatigue strength using the modified staircase method. No remarkable difference in terms of surface topography was found between the flood and cryogenic machined specimens, but the latter were characterized by higher and deeper compressive residual stresses and higher severe plastic deformation layer beneath the machined surface. Despite that, it is shown that the fatigue limit of the flood and cryogenic machined specimens is very similar, as well as crack initiation sites have the same location. An explanation of that can be found in the very fine microstructure of the as-received material, which prevails over the other characteristics induced by any machining strategy.
Study of cutting force in milling of aluminum-lithium alloy
Authors: TAMURA Shoichi
Published: April 2024

Abstract. Aluminum-lithium alloy has been applied to aircraft parts for reduction of the fuel consumption with its high specific strength. Cutting tests are performed to characterize the cutting force of aluminum-lithium alloy (Constellium, 2098-T8) and conventional extra-super duralumin (JIS A7075-T6) in slot milling at different spindle speeds. When the cutting speed increases, the tangential and radial components in cutting force of the aluminum-lithium alloy considerably decrease up to 300 m/min; while those of A7075 decrease monotonically. Then, the cutting process of aluminum-lithium alloy is discussed in an energy-minimum cutting force model. The shear angle and the friction angle increase with the cutting velocity, and the shear stress on the shear plane decreases with the increase of cutting velocity. According to the cutting model in milling of aluminum-lithium alloy, the cutting velocity should be taken higher than 300 m/min to not only reduce the cutting force but also control the surface finish.
Comparison of artificial intelligence techniques for cutting tool condition monitoring
Authors: COLANTONIO L.
Published: April 2024

Abstract. In manufacturing, tool wear monitoring is crucial as it directly influences production quality and operating costs. Inaccurate replacement strategies can result in increased costs and substandard parts. Various Artificial Intelligence (AI) methods have been proposed to monitor tool wear using cutting signals, but a comprehensive performance comparison is lacking. This paper evaluates three distinct AI approaches: Artificial Neural Networks (ANN), Support Vector Machines (SVM), and K-Nearest Neighbours (K-NN). The selection of these approach is based on their learning mechanisms. Each method is optimized using a GridSearch algorithm and their real-time wear monitoring capabilities are compared. The results shows that all AI techniques monitored tool wear with similar precision, making it challenging to draw a definitive conclusion in this regard. The choice of the most appropriate AI method is heavily dependent on the manufacturing environment. For large-scale manufacturing under similar cutting conditions, K-NN and SVM are a good choice. The ANN is better suited to all scenarios, but particularly where there are substantial fluctuations in cutting conditions or, in general, larger databases.
Milling of nickel-based superalloys using throttle cryogenic cooling and micro-lubrication
Authors: IQBAL Asif
Published: April 2024

Abstract. Nickel-based alloys are known to mount intense heat around the cutting edges of the cutting tool owing to their high yield strength, comparatively low thermal conductivity, and a significant seizure of the chip at the rake face even at low cutting speeds. Their sustainable machining demands a highly effective heat dissipation system. Due to its rich cooling potential, the compressed CO2-based throttle cryogenic cooling system is a prime contender. The presented work seeks a sustainable milling solution for the cutting of the following three nickel-rich allows using the combination of throttle cryogenic cooling and minimum quantity of lubrication: Inconel 718, Incoloy 825, and Waspaloy. The experimental study quantifies the effects of the lubri-cooling approach and cutting speed on tool wear, cutting forces, and workpiece surface roughness. The novelty of the work lies in the mutual comparison of the machinability of the three alloys of nickel and the application of the cryogenic coolant in the form of pulses in addition to the conventional mode of continuous stream. The analyses of the experimental results suggest that the pulsed mode of the coolant, especially in combination with the lubricant, outperforms the continuous mode of the coolant’s supply regarding cutting forces and work surface roughness. Additionally, the study has yielded mixed results regarding tool wear for different combinations of workpiece material and cutting speed. Nonetheless, dry milling of the three alloys proved to be absolutely unsustainable in comparison to either of the two modes of throttle cryogenic cooling, with or without the application of micro-lubrication.
A robust identification protocol of flow curve adjusting parameters using uniaxial tensile curve
Authors: LEMOINE Xavier
Published: April 2024

Abstract. ArcelorMittal is constantly developing new steel grades to enable the automotive industry to offer safer, lighter, and more environmentally friendly vehicles. These new grades include advanced high-strength steels (AHSS) and Ultra High Strength steels (UHSS) having for some of them lower uniform elongation (UE) than conventional drawing steels. This particularity needs to be considered for an accurate formability prediction in sheet forming numerical simulations. One of these difficulties is the effect of the relatively low uniform elongation on the identification of the parameters of the isotropic hardening model. Various experimental tests can be used to reach the large plastic deformation (hydraulic bulge test, stack compression test, shear test, torsion test or plane strain compression test). The identification protocol of ArcelorMittal for hardening models is based solely on stress-strain curves determined in uniaxial tension. The Exp_S hardening law (TU experimental values before UE%, Swift extension above) was validated by comparison with the stress-strain curves obtained from measurements of experimental tests reaching large strains.
Full field Continuous dynamic recrystallization simulations considering precipitates evolutions with DIGIMU®
Authors: DE MICHELI Pascal
Published: April 2024

Abstract. Full field simulations have proven to be an efficient tool for grain size prediction in industrial processes, with wider ranges of validity and more comprehensive results than other approaches. DIGIMU® is a level-set based solution able to simulate grain growth, Smith-Zener pinning, discontinuous dynamic, post-dynamic, and static recrystallization, and very recently Continuous Dynamic Recrystallization (CDRX). The goal of this work is to explore the capabilities of DIGIMU® to CDRX with evolving second phase particles. First, a new formalism has been implemented to describe particles boundaries with a level-set function. It is then possible to apply growth or dissolution velocities to the boundaries, and to make new particles appear. Secondly, the orientation has been defined in each grain, and the grain boundary energy can then be computed from the intergranular disorientation with Read-Shockley model. A boundary migration solver which considers heterogeneous grain boundary energy is used, which enables the simulation of structure and substructure evolutions. The Gourdet-Montheillet CDRX model is adapted from a mean field to a full field framework, and the corresponding parameters for Zircaloy-4 are identified. Thanks to all those developments, DIGIMU® can simulate full field CDRX in high stacking fault energy materials, coupled with precipitates evolution. Several examples will be presented, some of them compared to experimental results.
Corrective capabilities of different rescanning strategies to restore microstructure and density of initially porous 316L laser powder bed fusion
Authors: LE SAINT Théo
Published: April 2024

Abstract. Mechanical properties of Laser Power Bed Fusion (LPBF) parts, and particularly fatigue properties, are heavily affected by defects including surface roughness or porosity. To mitigate the occurrence of these defects, in-situ and on-line corrective measures can be implemented to the fabrication process, among them, rescanning, which consists in remelting an already solidified layer. Initially porous LPBF samples were created and then rescanned using different scanning parameters and strategies. Results show that it is possible to regain part’s health, compared to a standardly processed one, in terms of density, hardness and even improved roughness. This remelting process is known to refine microstructure of fabricated materials as well as reduce surface roughness and porosity without requiring further post-processing steps. Therefore, employing rescanning as a corrective technique appears to be a promising approach for rectifying detected defects during the fabrication process. The objective of this study is to assess the corrective capabilities of different rescanning strategies to restore the microstructure of an initially porous 316L LPBF simulating a defected part. This study shows that various rescanning strategies allow for densification of initially porous material from 98.83 ± 0.20 % to 99.75 ± 0.09 %, as well as lateral surface roughness reduction from Ra 20.2 ± 5.2 µm to Ra 12.7 ± 0.1 µm and microhardness increase from 243 ± 5 HV0.5 to 253 ± 3 HV0.5.
Applicability of productivity enhanced sinking-EDM of cemented carbide forming tools for bipolar plates
Authors: PETERSEN Timm
Published: April 2024

Abstract. The present research uses a previously published method to reduce the duration to machine cemented carbide forming tools by SEDM. Because of the forming setup a relatively thick sheet metal was used, which is why a forming simulation was conducted beforehand to achieve a valuable design, derived from bipolarplates, to observe wear in the forming experiments.
Optimizing powder compaction for enhanced relative density: Insights from multi-particle finite element simulations and genetic algorithm
Authors: GHORBANI-MENGHARI Hossein
Published: April 2024

Abstract. In this study, multi-particle finite element simulations in powder compaction were performed to analyze the effects of the size of the representative volume element (RVE), the number of elements per particle, and particle size distribution. Simulation parameters were calibrated to accurately predict the relative density of compacts derived from two types of powders. The influence of RVE size across four mixtures was examined to obtain its relationship with relative density. The impacts of particle size distribution and element number per particle were studied. The results indicate a decline in relative density with increased element size. Moreover, a genetic algorithm is employed to determine the optimum mixture composition yielding the highest relative density at 1400 MPa.
Characterization of recycled polyethylene terephthalate (rPET) – impact of proportion of virgin and recycled PET on mechanical strength
Authors: NGUYEN Thanh Tung
Published: April 2024

Abstract. Polyethylene terephthalate (PET) is a standard plastic with the highest consumption in the food packaging industry. The large amount of bottles produced makes imperative the search for the recycled PET (rPET). However, the recycling procedure generates the modifications of the mechanical, thermal and optical properties from virgin PET to recycled one. In this study, Digital Image Correlation method associated to numerical simulation is used to identify the mechanical properties of the bottles. The effects of various recycled PET ratios on the mechanical properties of bottles are discussed.
Analysis of the effect of draft angle and surface roughness on ejection forces in micro injection molding
Authors: MACIARIELLO Francesco
Published: April 2024

Abstract. Minimizing ejection forces is a crucial challenge in micro injection molding to prevent component damage during demolding. This research investigates the effects and interactions of draft angle, surface roughness, mold temperature, and holding pressure on the ejection force in a small, box-shaped component made from polypropylene (PP) and cyclic olefin copolymer (COC). A piezoelectric force sensor, integrated into the ejection tray of the mold, was used to measure the peak ejection force. The results indicate a significant influence of polymer type on ejection force, with PP exhibiting a 26% lower peak ejection force than COC. The draft angle consistently reduced demolding forces. Strong interactions were observed between mold temperature, surface roughness, and polymer type. Specifically, an increase in mold temperature led to an 88% increase in ejection force for COC, while resulting in a 63% decrease for PP. For PP, the optimal ejection force was measured at a surface roughness (Sa) of 0.095 µm, while for COC, a continuous decrease in ejection force was measured with decreasing surface roughness.
Multi-material topology optimization of additively manufactured thermoplastic molds for heat transfer enhancement
Authors: STORTI Bruno A.
Published: April 2024

Abstract. For low-volume scale manufacturing of plastic parts, thermoplastic molds made of polymers and printed by additive manufacturing (AM) technology have proved to be a viable alternative to replace expensive and time-consuming steel molds. Nevertheless, due to the relatively low thermal conductivity of the polymers employed for their manufacture, not only the cycle times are increased, but also the surface temperature homogeneity is affected during the cooling of the part, potentially impacting its final quality. On the other hand, the latest advances in AM technology allow the 3D printing of parts with two polymers of different thermophysical properties, opening the possibility for heat flux manipulation within the thermoplastic mold. This work is devoted to the numerical implementation of a topology optimization (TO) methodology to enhance the temperature homogeneity of an injected part during the cooling phase. The proposed scheme relies on the usage of the gradient-free particle swarm optimizer (PSO) in conjunction with filtering techniques to obtain a feasible-to-manufacture multi-material thermoplastic mold. The TO strategy is thoroughly validated against gradient-based techniques found in the related literature conceived for heat flux manipulation in the transient regime. The results show outstanding improvements in the temperature homogeneity of the part when strategically placing the low-conductivity polymer in easy-to-cool regions and the high-conductivity polymer in regions that cool down slower. We further report in this work the possibility of achieving standard deviation values like those obtained by a steel counterpart.
Design optimization of filament wound cylinder by considering process induced residual stresses
Authors: PALMIERI B.
Published: April 2024

Abstract. The manufacturing process has a significant influence on the product quality of filament wound composite parts. During the filament winding process, a large tensile load to the fibre was applied and maintained during resin curing, resulting in residual stress. This residual stress gradually relaxes due to the fibres’ slippage, the matrix’s crosslinking, and different coefficients of thermal expansion between composite parts and mandrels. As a result, increasing the number of layers becomes more problematic. In this work, a multiphysics analysis has been carried out to study the effect of the viscoelastic behaviour of the material on the rise of residual stress on thick cylinders. The multiphysics model was developed in COMSOL to predict the temperature distribution and the degree of polymerization during the consolidation process. The optimal cure profile was identified as a function of process parameters to minimize the thermal gradient within the composite element.
Wear monitoring of metal sheet stamping process driven by acoustic emission data
Authors: TIANJIAO Bi
Published: April 2024

Abstract. The study addresses limitations related to mold wear during the stamping process, which impairs part quality due to the low predictability of wear, leading to increased production scrap and unreliable production schedules. To tackle these issues, a tool condition monitoring strategy driven by Acoustic Emission (AE) data is proposed for assessing the wear state of stamping molds. An integrated model for decomposing AE signals, employing the rolling decomposition method, is developed. This model eliminates the reliance on future data to avoid information leakage and is capable of monitoring critical wear indicators in stamping molds. The experimental phase, conducted in an industrial-grade stamping process setting, involved collecting degradation signals from healthy to fatigued states to verify the effectiveness of the proposed method. The outcomes indicate that the data-driven approach, utilizing AE signals, is efficient in monitoring stamping mold wear.
An efficient steady-state thermal model for predicting the lack-of-fusion porosity during laser powder bed fusion process
Authors: JIA Yabo
Published: April 2024

Abstract. The lack-of-fusion porosity due to the incomplete melting of the powder should be avoided during laser powder bed fusion (LPBF) process. The porosity will reduce the performance of mechanical properties. In certain manufacturing processes, the thermal and metallurgical quasi-steady-state can be reached quickly. In this article, a steady-state model, incorporating new dedicated boundary conditions, is proposed and applied in the multi-track simulation of LPBF to control porosity. Various processing parameters, such as hatching space and cooling time inter-pass can be investigated. The transient step-by-step simulation is also employed as the numerical reference. Numerical comparisons demonstrate that the proposed steady-state model achieves a relative good agreement with the numerical reference while significantly reducing computing time (2-3 minutes).
Inverse identification of heat source model parameters for laser-powder directed energy deposition of AISI H13 deposit on AISI H11 substrate
Authors: BERTRAND Johanna
Published: April 2024

Abstract. Numerical modeling and simulation are very useful tools for assessing the impact of process parameters and predicting optimized conditions in Laser Directed Energy Deposition (L-DED) processes. Heat source parameters have a great influence on the accuracy of numerical modeling for predicting temperature fields and residual stresses. This paper presents a coupled experimental-numerical procedure to determine the Goldak’s heat source model parameters. Graded single-clad tracks were printed with the laser beam power increased continuously at a constant powder feeding rate and scanning speed. Bead widths, heights, and penetration depths were measured at different locations along the deposited track and then used as experimental data for an inverse identification process using the FEA code ABAQUS and the optimizer iSIGHT. The obtained results show that the accuracy of the numerical model is increased with optimized parameters.
Differential thermal analysis to assist the design of corrosion-resistant high entropy alloys for laser powder bed fusion
Authors: SEIDOU Abdul Herrim
Published: April 2024

Abstract. In this study, Al, Cr, Fe, Mn, and Ni are selected and pure elemental powders were used to prepare several medium entropy alloys (MEAs) and high entropy alloys (HEAs). Differential Thermal Analysis (DTA) is used as a tool for pre-screening of the compositions suitable to design corrosion-resistant alloys for Laser Powder Bed Fusion (LPBF). The advantage of DTA lies in the precise temperature control and in the small quantity of powder necessary to perform the test in near-equilibrium conditions. The powder mixtures were heated up to 1550°C, fully melted, and then cooled down to room temperature at 5°C/min. The results of DTA are used as reference to understand the complex microstructures obtained using LPBF. Microstructure analysis of DTA samples by combining Optical Microscopy (OM) and Scanning Electron Microscopy (SEM) helped to confirm the phase prediction theories. Most of the samples showed a heterogeneous structure with Ni-Al rich B2 phase, Fe-Cr rich BCC and FCC phases. The spinodal decomposition of the BCC phase was also observed in the equimolar AlCrFeMnNi sample. The Valence Electron Concentration (VEC) theory was verified and the partitioning of the elements between the phases was investigated.
Rheological characterisation and modelling of a glass mat reinforced thermoplastic for the simulation of compression moulding
Authors: Althaus P.
Published: April 2024

Abstract. The use of hybrid components in the automotive industry is steadily increasing due to their lightweight potential. By combining fibre-reinforced plastics with metallic materials, high-strength components with lower weight than monolithic metal parts can be realised. The overall aim of the project “HyFiVe” is to exploit this potential for electric vehicles by developing a scaled battery housing structure made of a glass mat reinforced thermoplastic (GMT) paired with unidirectional reinforced (UD) tapes and a metallic reinforcement frame. The GMT is formed by compression moulding and serves as the base of the battery housing structure. Numerical simulation is an efficient tool for process design that can determine a suitable process window and reduce experimental trial-and-error tests. Particularly, realistic modelling of the GMT flow behaviour is essential for reliable simulation results. In this contribution, the rheological properties of a GMT consisting of a polyamide 6 (PA6) matrix with 30% glass fibre reinforcement were determined. Isothermal compression tests were carried out with a parallel plate rheometer at different temperatures and varying squeeze rates. The squeeze force and punch displacement were evaluated to determine the rheological data of the GMT. Two methods for the modeling of the flow behaviour were considered. At first, pure shear flow was assumed and the viscosity was modelled as a function of the shear rate by means of a power-law. Secondly, a pure biaxial extension was assumed and the true stress was modelled in dependence of true strain and strain rate. Subsequently, for a verification of the material models, the compression tests were simulated in ABAQUS using the Coupled Eulerian-Lagrange (CEL) approach and the results were compared to the experiments.
Considering the viscoelastic material behavior in a solid-shell element for thermoforming simulation
Authors: MITSCH Johannes
Published: April 2024

Abstract. To predict manufacturing effects in the thermoforming process for fiber reinforced plastics the Finite Element Method is widely used. Most macroscopic simulation methods are based on conventional two-dimensional shell elements which are not capable of modeling the material behavior in thickness direction using constitutive equations. At the same time, standard three-dimensional element formulations are not suitable for the forming simulation of thin textiles due to numerical locking phenomena and the lack of a possible membrane-bending-decoupling. Previous studies focused on a specialized solid-shell element formulation which provides anisotropic but purely elastic material modeling. Since purely elastic approaches cannot accurately describe the deformation behavior in the thermoforming process, the provided element formulation is enhanced to rate-dependent viscoelastic material modeling. Numerical studies are carried out that reveal that the membrane-bending-decoupling is preserved for the viscoelastic material model. Virtual coupon tests demonstrate the rate-dependent material behavior in the solid-shell element. The obtained results show that the general approach of the viscoelastic material behavior within the solid-shell element is suitable to address out-of-plane phenomena in thermoforming simulations.
Analysis of mechanical properties of stainless steel small diameter cold drawn wires
Authors: VAISSETTE Julien
Published: April 2024

Abstract. Wire suppliers commonly only commit to the chemical composition and minimum mechanical resistance of their wires in their material certificates. Unfortunately, the cold drawing process induces residual stresses that potentially have a strong impact on the overall behavior of the wire. An explanation of the difference between the industrial ‘tensile modulus’ and ‘flexural modulus’ whereas the material has a unique ‘Young Modulus’ is proposed by mean of FEA and experimental tests. Moreover, in order to better estimate the complex material state of small wires (with a diameter smaller than one millimeter) a novel experimental approach has been developed to estimate the residual stress.
Thermal multi-sensor instrumentation for the enhancement of a directed energy deposition process
Authors: DE PEINDRAY D’AMBELLE Lilou
Published: April 2024

Abstract. Directed energy deposition (DED) is an additive manufacturing process with growing industrial interests. Nonetheless, its industrialization will not be possible until it is fully mature. Such maturity lies in the upstream research to optimize and control it. In DED, process parameters, physical quantities and parts properties are interrelated which makes it a complex process. To have a better understanding of these relations, the experimental approach of instrumentation has been chosen. Multi-sensor method has been implemented for its more extensive possibilities in comparison to single-sensor methods. A bichromatic pyrometer was coupled to an IR camera to measure the temperature distributions in real time. Post-process characterizations of the aspects and geometries of the parts were related to the sensors’ measurements and consequently, to the process parameters. Twelves sets of parameters were tested to conclude that the energy input impacts the size of the melting pool and the temperature distribution. High energies lead to defects such as edge defects and layer thickening but can mitigate surface roughness. Both the pyrometer and camera proved to have a relevance in this study for the enhancement of the DED process.