bluuebunny/crossref_metadata_2025 huggingface dataset:
ESAFORM 2021 cup drawing benchmark of an Al alloy: Critical follow up analysis of its potentials
Authors: OLIVEIRA M.C.
Published: April 2023

Abstract. The 1st ESAFORM Benchmark, called EXACT [1], enabled an in-depth study of the factors that contribute to the accuracy of predictions and efficiency of finite element (FE) simulations of deep drawing of a cup from AA 6016-T4 sheet through the joint work of 11 teams. FE analyses were conducted with elasto-plastic models or crystal plasticity approaches using commercial or academic FE codes. This paper reminds the content of EXACT benchmark and gives new results that highlight the importance of the tool stiffness and various contact conditions to predict the ironing forces and the thickness distribution along the cup wall. The use of the Benchmark experimental data and virtual tests performed with DAMASK crystal plasticity code to identify and validate a two-surface kinematic hardening model based on Yoshida and Uemori approach is also discussed.
Finite element model for micro-stamping titanium bipolar plate
Authors: KHADEMI M.
Published: April 2023

Abstract. Bipolar plates are the essential components of a Proton Exchange Membrane Fuel Cell. Lightweight bipolar plates can be micro-stamped from an ultrathin metallic foil. A major concern is the manufacturability of the foil in the micro-stamping process. The typical stamped micro-channels have end cavities or corners where the deformation mode can be different from the two-dimensional plane strain conditions that occur at the straight sections of the micro-channels. The thin foil has a large ratio of length (or width) to thickness, and shell elements were often used for three-dimensional models. Currently, it is unknown if the shell elements available in commercial software packages are able to predict the ultrathin material behaviour correctly. In addition, the deformation behaviour and forming limits of titanium foil in the micro-stamping process are not well understood. The current study uses a micro-stamping tool to produce straight micro-channels from commercially pure titanium foil. The experimental data are used to validate a two-dimensional and a three-dimensional finite element model of the process. It is shown that there are deviations between the experimental and the numerical thinning results. Material thinning is different between the straight and the cavity end sections suggesting that three-dimensional process models are required to accurately analyze forming.
Evaluation of data transfer influence in coupled Monte Carlo finite element model on microstructure evolution predictions
Authors: WERMIŃSKI M.
Published: April 2023

Abstract. The processes of microstructure evolution under thermal loading occurring during welding or additive manufacturing are highly complex and challenging to observe experimentally. Therefore, in this work, to support experimental investigation, a hybrid numerical model based on the combination of the Monte Carlo (MC) and Finite Element (FE) method was developed to simulate both temperature profiles and corresponding grain growth phenomena at a micro scale explicitly. The welding simulation was selected as a case study. The discrete MC microstructure evolution model is based on the temperature distribution provided by the FE simulation with the Goldak heat source model. The temperature data are transferred from 3D FE space to cubic MC Pott's domain in each time step. Direct coupling between the MC cells and FE cubic elements provides accurate results but significantly increases the simulation time. Therefore, coarser FE meshes are used in the research, but this requires applying reliable data interpolation techniques between the two methods. As a result, the temperature field stored in a coarse FE cloud of points is interpolated into regular high-resolution MC cell space in each time step. Evaluation of the influence of various interpolation methods, along with their parameters on the final microstructure morphology after welding, is presented within this work.
Digital twin for the determination of process input variables for electrochemical precision machining according to DIN SPEC 91399
Authors: THIELECKE A.
Published: April 2023

Abstract. The ablation results with electrochemical precision machining (PECM) are essentially influenced by the material to be processed and by the current density distribution in the working gap. Therefore, ablation experiments according to DIN SPEC 91399 are essential to determine the material-specific removal characteristics and to derive process input variables for the process design. A main limitation of these experiments is the lack of accessibility at crucial surfaces on the workpiece and on the device, which means that relevant information such as the local current density distribution or the local temperature field cannot be measured. To face the mentioned limitation, the aim of this work was to develop a digital twin for an experiment for PECM according to DIN SPEC 91399. The digital twin is based on a commercial multiphysics simulation software with the main property that the calculation time of the model is less than the real time for the experiment to allow a simultaneous processing of experiment and simulation. Via suitable interfaces, experiment and simulation can be interconnected in future. Based on this, the digital twin can be applied to evaluate parameters, monitor the process in real time and adapt it accordingly. The design and the properties of the digital twin will be shown exemplary for an experiment with the workpiece material steel 1.4301.
Influence of material properties on near dry-EDM process: The discussion of research for titanium grade 2 and Inconel 625 alloy
Authors: ŻYRA A.
Published: April 2023

Abstract. Dry EDM machining with external workpiece cooling is one of the possible modifications of dry EDM process, which enables to reduce the negative impact of EDM machining on the environment and on the machine tool operator. At the same time, it is possible to obtain relatively good machining accuracy and surface quality. Due to the problems with the effective heat dissipation from the machining gap, the application of dry-EDM is still limited to micromachining. In this paper the comparison and discussion of dry-EDM technological factors for two hard to machine materials: Inconel 625 and Titanium Grade 2 have been presented. The tests were carried out in carbon dioxide as a dielectric supplied to the machining gap through the channel in the workpiece electrode. To improve the process effectivity additional workpiece cooling were also applied, however the presence of fluid in machining area makes the process near dry-EDM. The input machining parameters were pulse time, machining voltage, current amplitude and inlet gas pressure. The main aim of this work was to show the significance of the type of machined material on the material removal rate, and surface layer (i.e. roughness, morphology and microhardness). The results analysis will be discussed considering differences in physical properties of machined materials.
The sound insulation capacity of some panels made of polymeric materials manufactured by 3D printing
Authors: HRIȚUC A.
Published: April 2023

Abstract. The soundproofing of certain spaces is necessary primarily to combat noise pollution generated by high-intensity noise sources. One of the ways to reduce the unwanted propagation of high-intensity sound waves is based on the use of panels made of polymeric materials. The expansion in recent decades of the manufacturing processes of parts by 3D printing has led, among other things, to the identification of ways to change the properties of the materials included in the parts manufactured by 3D printing and to modify, in this way, including the sound insulation properties of such materials. For the development of experimental research aimed at allowing the study of the sound insulation capacity of small panels made by 3D printing from polymeric materials, a relatively simple equipment was designed. Equipment includes an enclosure in which the sound source, the small panel, and the sensor of a device used to evaluate the characteristics of sounds. Experimental tests were carried out on panels made of polylactic acid. The experimental results were mathematically processed with the help of specialized software. An empirical mathematical power function model was determined. This empirical mathematical model highlights the intensity of the influence exerted by the thickness of the panel by the speed and volume of the sounds on the acoustic pressure level. It was found that the strongest influence is exerted by the volume of the sound wave.
Process characteristics of constrained friction processing of AM50 magnesium alloy
Authors: DE CASTRO C.C.
Published: April 2023

Abstract. Constrained Friction Processing (CFP) is a novel solid-state technique suitable to produce rods especially from lightweight materials. The technology is particularly interesting to overcome the processing challenges associated with Mg due to its hexagonal close-packed (hcp) structure. The process is a variation of the refill friction stir spot welding (refill FSSW) technique, and is performed by plunging the rotating shoulder into the base material, which causes the material to be extruded into the cavity crated by the retraction of the rotating probe and, at the same time, being constrained by it. The complex shear and the heat generated during the process causes metallurgical transformations in the material, such as dynamic recrystallization, allowing for substantial grain refinement to micro- or even submicro- scale. In this study, real time data – torque, axial force and temperature – acquired from the process are analyzed in order to present, for the first time, a description of the CFP technique. Furthermore, the resultant features of the microstructure of a refined rod is explored.
Influences in deep hole sinking (EDM, ECM) that make it difficult to analyze the process status
Authors: SCHULZE H-.P.
Published: April 2023

Abstract. A particular problem of deep hole sinking is the correct process analysis during the sinking process. It is important to know the primary technological objectives and to design the process regulation accordingly. Due to the objectives high removal rate, minimum roughness of the inner surface, high dimensional accuracy, etc., the analysis criteria are clearly changed and must be made available to process regulation. Another influencing parameter is the structure of the process energy source (PES).
Polymer-tool friction coefficient in temperature for thermoforming numerical simulation
Authors: CAUBET B.
Published: April 2023

Abstract. In this work, friction coefficient between Polycarbonate and Aluminum was measured over the entire thermoforming temperature range by using a rotational rheometer with a specific geometry, following the B. Hegemann et al. [1] method. The effects of velocity, pressure and surface roughness were investigated. Then, numerical simulation were performed using a finite element code package for thermoforming (T-SIM®) with K-BKZ viscoelastic model. The objective of this work is to find which friction coefficient use in T-SIM simulation to be as close as possible to reality. For this, numerical simulation results for different friction coefficient were compared with experimental values to evaluate the predictive capacity. It was shown that friction coefficient is temperature dependent and rapidly increase above glass transition of polycarbonate. At room temperature, friction coefficient increases with an increase in roughness, but after glass transition, trend is reversed. Simulations with measured friction coefficients shows good agreement with experiment data.
A local power law versus a well-identified viscosity curve over a large shear rate range in thermorheology of polymers
Authors: LIN Q.
Published: April 2023

Abstract. There are always debates on the use of power law to model flows having a local zero shear rate. This paper uses an original method to define a functional shear rate range with respect to the flow condition and identify an equivalent power law from a Cross-law fluid. The numerical and experimental results are compared to show the ability of the power law to model a flow having a low-shear region.
Technological and sustainability implications of wet and dry turning of Ti6Al4V EBM parts
Authors: COZZOLINO E.
Published: April 2023

Abstract. Sustainability is a crucial topic nowadays and Additive Manufacturing (AM) processes are becoming more and more widely used today also because, among its advantages, is claimed to be green technology. However, AM parts usually require postprocessing to improve their surface finishing and result assemblable. In this study, a Ti6Al4V cylindrical sample has been manufactured by Electron Beam Melting (EBM) and then post-processed by turning. Both dry and wet turning has been performed by using the same process parameters. Surface roughness has been measured both before and after each turning pass along the parallel and perpendicular direction to the cylindrical axis and energy consumption has been recorded during each turning pass. Results showed that both dry and wet turning led to a lower roughness along the perpendicular direction to the cylindrical axis than that along the parallel direction, as a result of the technological signature of the turning process. Also, they depict that the first turning pass results in higher cutting forces and, then, the highest values of energy consumption among all the turning passes, both in wet and dry turning. The Specific Energy Consumption (SEC) index has been investigated to evaluate the energy required to remove a unit volume of material; it reflects lower cutting efficiency in the material removal process.
2D FE modeling of the thermal history of the heat affected zone in AlSi10Mg LPBF
Authors: DELAHAYE J.
Published: April 2023

Abstract. As an easily processable Al alloy, AlSi10Mg manufactured by Laser Powder Bed Fusion (LPBF) has received a lot of attention so far. However, it is well known that microstructural heterogeneities at the scale of the melt pool – in particular the weaker Heat Affected Zone whose microstructure evolves during the deposition of the next layer – exert a strong detrimental effect on the ductility of AlSi10Mg LPBF. In this work, a 2D Finite Element (FE) model is developed in order to tackle this issue and help in guiding the optimisation of LPBF process parameters. The model is calibrated using experimental measurements of the melt pool height. Furthermore, to allow for the efficient simulation of 5 successive layers, a remeshing procedure is implemented. No heat accumulation is observed during the deposition of these 5 layers. The thermal history of the HAZ can thus be studied with a thermal model for one layer.
Analysis of temperature effect on strength and microstructure in friction induced recycling process (FIRP)
Authors: Borgert T.
Published: April 2023

Abstract. In order to reduce global energy consumption in production and industry along with the associated CO2 emissions, existing resources must be used more efficiently. This includes the energy-efficient and comprehensive recycling of a wide range of metals. Especially for the production of aluminium, there is a large potential for saving energy using efficient recycling processes. With regard to the recycling of aluminium studies have shown that solid-state recycling processes are significantly more efficient considering the used energy and resources compared to the conventional, smelting-metallurgical recycling process. In this paper, the direct and energy-efficient friction-induced recycling process (FIRP) based on the conform process is further described and analysed in terms of the temperature-property relationships. For this purpose, the influence of the processing temperature on the microstructure and properties of the recycled semi-finished products is investigated using the toll system that enables an ECAP forming. Specific sections of the (in theory) infinite, recycled semi-finished product are taken and analysed at different process temperatures of the solid state recycling process. Based on these sections, the properties in terms of mechanical hardness, strength, ductility and grain size are analysed and a degressive relationship between process temperature and mechanical hardness up to a temperature of 270 °C can be shown. Applying the Hall-Petch relationship, it is analysed whether there is a correlation between the strength and the microstructure in the form of the grain size.
Characterization of friction stir consolidated recycled billet by uniaxial compression tests with miniaturized cylindrical specimen
Authors: Latif A.
Published: April 2023

Abstract. Friction stir consolidation (FSC) is a solid-state recycling method that directly converts machining scraps into semifinished billets. This process has been proven to be a more energy efficient and environmentally friendly technique compared to remelting based conventional recycling methods. During FSC, machining chips are transformed into a solid billet by the stirring action and friction heat of the rotating tool. Due to process mechanics, especially temperature gradient and strain rate, billets have shown different hardness values and grain size distribution across their sections. Therefore, in this research, miniaturized upsetting samples are extracted from the FSC billet. The purpose of minimizing the sample size is to get the local properties of a particular position. The intensive characterization was performed with future goals to find a more accurate numerical modelling and ultimately assign FSC billet to a potential industrial application.
Cryogenic reverse flow forming of AISI 304L
Authors: ARIAN B.
Published: April 2023

Abstract. Workpiece property-control permits the application-oriented and time-efficient production of components. In reverse flow forming, for example, a control of the microstructure profile is not yet part of the state of the art, in contrast to the geometry control. This is, due to several reasons, particularly challenging when forming seamless tubes made of metastable austenitic stainless AISI 304L steel. Inducing mechanical and/or thermal energy can cause a phase transformation from austenite to martensite within this steel. The resulting α’-martensite has different mechanical and micromagnetic properties, which can be advantageous depending on the application. For purposes of local property control, the resulting α’-martensite content should be measured and controlled online during the forming process. This paper presents results from the usage of a custom developed cryo-system and different application strategies to use liquid nitrogen as a coolant for local enhancement of the forming-temperature depending α’-martensite content.
Semi-finished powder of aluminum matrix composite for a direct energy deposition additive manufacturing
Authors: JEDYNAK A.
Published: April 2023

Abstract. Aluminum-Matrix Composites (AMCs) are particle-reinforced aluminum matrix composites that are well-established in high-performance lightweight components in the automotive and aerospace industries. So far, the use of AMC materials has been limited to components manufactured using casting technology (e.g. brake discs). The adaption of AMC materials in Additive Manufacturing (AM) processes, such as powder feedstock for Direct Energy Deposition (DED), is dependent on the availability of the corresponding semi-finished product. An approach for the production of such a semi-finished product is presented in the current work. This study presents, how powder as semi-finished product for the DED processes, is produced from cast ingots manufactured by Direct-Vacuum-Casting (DVC). The novel DVC process allows a SiCP particle content of up to 35%, whereas conventional AMC casting processes can only achieve a fully embedded SiCP particle content of up to 20%. Particular attention is paid to ensuring that the SiCP particles remain completely embedded in the aluminum matrix after the semi-finished product has been produced. However, there is currently not an extensive literature existing on semi-finished products from AMC materials in AM processes. Therefore, in these investigations, ultrasonic atomization technology was used to produce of AMC powder with an average size of 80 µm as a feedstock material. The microstructure analysis of this powder demonstrated the presence of primary SiCP particles with non-optimal distribution. Nevertheless, the AMC powder was used in the subsequent DED process studies. It was possible to develop the fundamentals for the deposition processing of AMC powder. As demonstrated by microscope techniques, secondary SiCP particles were precipitated in an aluminum matrix with complete embedding during deposition, pointing the way forward to develop AMC powders as semi-finished products in AM processes.
Proposing a virtual simulation method to predict the shape-fidelity of 3D-knitted-textiles using knit-meshes and geometric invariants
Authors: DIETRICH F.
Published: April 2023

Abstract. Though the level of machine digitization in flatbed-knitting (FBK) today is high, the design and development of knittable data sets are still currently very time-consuming, digital simulations methods are calculation expensive and insufficient in terms of accuracy of fit and technical properties. Knitting process retrofitting activities are executed mostly manually by an operator on the basis of the operator´s experience. This circumstance makes it more difficult to use the diverse potential for flexibility and on-demand purposes in future-networked-production for lightweight constructions for Automotive, Aerospace and aviation or Medical-Products. New easy-to-learn, intuitive, calculation inexpensive digital augmented workflows for the planning of knitted objects with complex 3D-shapes are needed. With regard to the requirements of composite forming, the aspects of wrinkling, slip and permeability are of particular importance. However, flatbed-knitted fabrics are subject to different requirements in some cases, which implies different questions from those posed by research in the area woven textile composites. In order to address a few of the questions raised by previous research on textile composites, this paper covers some of the current research topics in the field of 3D-knitted flatbed-knitting fabrics and shows references as well as potentials to already researched problem fields of textile reinforced composites. In doing so, the author strongly refers to the topics of the summarizing publication "Advances in composite forming through 25 years of ESAFORM" by P. Boisse et al. [1].
Feasibility study of compression molding for large reinforcement structures in the commercial vehicle sector
Authors: LÜCKENKÖTTER J.
Published: April 2023

Abstract. Due to an increasing volume of shipments, there is a significant need for more delivery vehicles. One approach to reduce the associated increase in carbon dioxide (CO2) emissions is a new light weight design approach involving the substitution of conventional materials with glass fiber mat-reinforced thermoplastics (GMT) based on polypropylene (PP). The application of GMT by compression molding is a widely used process in the automotive industry. However, application in the commercial vehicle sector requires much larger dimensions, making it necessary to clarify whether the manufacturing process and material are suitable for semi-structural applications on this scale. To find this out, two replacement geometries are abstracted in this study and manufactured by varying the main manufacturing parameters. The feasibility can be demonstrated by recording and analyzing the resulting process variables and measuring the formed fiber distribution. At the end of the paper, recommendations are given for the production of GMT structures on the scale of commercial vehicles.
Compaction behaviour of magnesium alloy-based fibre metal laminates at varying forming parameters
Authors: Liu Z.
Published: April 2023

Abstract. This research presents a methodology for the compaction characterization of thermoplastic prepregs with a twill weaving style under a range of parameters typical of the thermoforming process applied to magnesium alloy-based fibre metal laminates (FMLs). The compaction tests were conducted making use of a plate-to-plate mode testing setup. The through-thickness and transverse width of the prepregs were evaluated on the FML specimen cross-section at varying compaction force and temperature. Significant deformations were observed at the lowest compaction force above the prepreg polymer melting point, whereas a further increase in the compaction force led to gradually smaller through-thickness and in-plane deformations. Additionally, a higher decrease in thickness and increase in width of the prepregs were detected at higher temperatures.
XCT-based microscale analysis of structure and deformability of abdominal wall meshes
Authors: SOETE J.
Published: April 2023

Abstract. Abdominal wall hernia repair mostly involves the implantation of a synthetic mesh material. The link between the mesh microstructure, mechanical behaviour and clinical outcome is still not fully understood, complicating the selection of a suitable patient-specific mesh. Here, we created a parametric 3D model of a synthetic mesh based on X-ray microfocus computed tomography (XCT) images. The model was implemented in a TexMind Warp Knitting Editor software and then exported for finite element model (FEM) analysis. This model allows better understanding of the mechanical behaviour of the mesh and identifying the influence of single structural parameters that are essential for the design of the mesh. We also used the XCT-based filament paths to directly build a FEM, representing all 3D structural details of the as-produced product. Whilst the mechanical analysis of the mesh is feasible, important difficulties are identified, related to the initial relaxed mesh contacts configuration and necessity of the mesh pretension in experiments and calculations.
A unit-cell mesoscale modelling of biaxial non-crimp-fabric based on a hyperelastic approach
Authors: ZHENG R.
Published: April 2023

Abstract. Understanding the mechanical properties of carbon fiber reinforcements is necessary for the simulation of forming processes. A unit-cell mesoscopic model provides a tool to implement virtual material characterizations which can be served as an input for macroscopic modelling, avoiding complex experimental tests and significantly reducing calculation time. Meanwhile, the occurrence of some local defects during the forming process, such as the gapping, would be easier to be detected through a mesoscopic approach. In this research, a novel mesoscale model for biaxial non-crimp fabric is developed based on the geometry measured from the results of X-ray tomography. A hyperelastic constitutive law is applied to the fiber yarns which are considered as a continuous medium. One type of unit-cell model is chosen and validated through a comparison with experimental tests and its in-plane shear behavior is studied.
Manufacturing of hybrid thermoplastic-thermoset fiber reinforced composite and metallization by cold spray technique
Authors: PARMAR H.
Published: April 2023

Abstract. Polymer and polymer matrix composites (PMCs) have found applications in aerospace sector. Thermosets (TS) possess higher corrosion resistance, shape retention and durability. Thermoplastics (TP) are easier for remolding in comparison to the former. Surface metallization is one of the recently applied trends for electrical and thermal properties improvement. In different metallization methods, primary restrain is the thermoset surface degradation, whereas thermoplastics have been found to be favorable for metallization. The presented article is part of continuous study aiming the cocuring of thermoset-thermoplastic resin with fibrous reinforcement. The composite manufacturing stage consisted of resin infusion (RI) process route for realizing the composite. Main objective of this stage was the through thickness and linear direction impregnation of thermoset to ensure the sound composite comprising contact between thermoplastic layer as well as fiber reinforcement. Fiber reinforcement combined with the resin infusion auxiliary materials were placed over the thermoplastic material prior to the vacuum bagging stage. Catalyzed thermoset resin impregnation in the vacuum bagged preform was conducted under the cocuring cycle. The composite panel was subsequently metallized via low-pressure cold spraying technique. The coating formation was analyzed with process parameters variation. Qualitatively, coating formation on such hybrid composite substrate was observed. However, the substrate manufacturing was found to have influence on the coating quality. Adhesion pull-off test displayed detachment zone directly in the coating substrate interphase. Presence of voids and less thermoset resin was noticed in the case of coating attempts varying process parameters such as traverse speed and standoff distance. Higher adhesion was noted with lowest selected 1 mm/s traverse speed and 10 mm standoff distance.
Forming of textile fabrics with additively assembled protective elements on the human body
Authors: KYOSEV Y.
Published: April 2023

Abstract. Stab protective clothing is used in a wide range of applications, including military and police applications, but is also becoming increasingly important for civilian users. A relatively new way of manufacturing personal protective equipment is additive manufacturing. This makes it possible to produce new types of stab protection geometries by applying polymer layers to textiles. Such composite structures represent a mechanical system of rigid bodies with constraints, especially with large continuous protective surfaces. As a result, the wearing comfort is limited. This paper presents two methods for numerically simulating the forming of reinforced textiles with solid polymer elements over the body as part of the development and optimization process of such garments.
Process and structural simulation for the development of a pressure vessel through filament winding technology
Authors: BIANCHI I.
Published: April 2023

Abstract. Recently, Università Politecnica delle Marche and COMEC Innovative srl are involved in the research project “Smart Tow Winding” funded by MIUR (Ministry of Education, University and Research), concerning the development of an innovative process for the realization of a pressure vessel through Filament Winding (FW) technology. In this context, a design procedure for type IV composite pressure vessel is proposed. To design the component, the dedicated simulation software CADWIND was used to virtually generate the pressure vessel through the definition of the desired geometry, the type of prepreg, the number of layers and the bandwidth. The generated file was imported in the FEM simulation software Siemens NX with the aim of evaluating the structural resistance under an internal pressure of 70 MPa. Different external configurations of mandrels and stratification were tested in order to optimize the geometry of the vessel and the resistance to weight ratio. A high performance and low weight vessel configuration was finally identified.
Experimental study of woven fabrics forming defects
Authors: SHANWAN A.
Published: April 2023

Abstract. The manufacturing of composite materials can be ensured by several industrial processes, like Liquid Composite Molding (LCM). This technology is used to produce composite parts with complex geometries because it provides a very good compromise in terms of repeatability, production rates and cost. During the forming phase of an LCM process, a fabric can be formed by highly double curved punch geometries where it could be submitted to several deformations and mechanical stresses that lead to the appearance of different types of defects: buckles, gapping, in-plane pull-out, etc. In order to understand their phenomenology, different types of defects were generated inside samples of glass and carbon fabrics so as to understand their mechanisms of appearance. This work focuses on the phenomenology of appearance of forming defects and the definition of experimental parameters allowing the generation of calibrated defects, such as buckles and gapping, inside samples of glass and carbon woven fabrics. The definition of these parameters allows the manufacturing of composite parts with calibrated defects, which in turn helps to define the influence of these defects on the mechanical behavior of composites materials.
Crush core forming: An innovative technology to manufacture structural sandwich parts with variable thickness
Authors: SORRENTINO L.
Published: April 2023

Abstract. Sandwich structures, constituted in honeycomb core and skin in composite material, are usually employed to produce parts having a constant thickness or simple shape. Indeed, sandwich components with complex shapes, curvature or varying thickness are costly to manufacture due to the preliminary machining operations required on the core prior the molding process. A novel approach to manufacture complex sandwich structures, knows as Crush Core Forming (CCF) process, consisting in press-forming simultaneously the core material and the skins into the shape is under study. Such a method is potentially able to increase the production rate and lowering the overall costs. The present work aims to develop an experimental route to produce sandwich panels by means of CCF process and build a FE model of the forming process and validate it against the experimental studies. Experimental study was conducted to derive the fundamental parameters and properties for core and skins to be added in the FEM model of the CCF process. After, the numerical model was implemented to simulate the forming of the core and skins. Finally, a laboratory scale sandwich part was produced to validate the model outputs and assessing the reliability of the proposed approach.
Development and processability of AISI S2 tool steel by laser powder bed fusion
Authors: SAGGIONETTO E.
Published: April 2023

Abstract. Nowadays, the advantages of Laser Powder Bed Fusion (LPBF) technology attract both industry and researchers. Indeed, it is possible to build up complex geometrical parts with higher mechanical properties than those obtained by conventional methods. However, LPBF involves complex phenomena due to the high heating and cooling rates that lead to out-of-equilibrium conditions. For this reason, few metal alloys are easily processable up to now. Nevertheless, research on new steels by LPBF has been growing in recent years, in particular, regarding the development of tool steels. This work thus focuses on the development of the tool steel AISI S2 by LPBF. The process map has been investigated by varying the laser power from 100 to 250 W and the scan speed from 400 to 2000 mm/s. By combining surface analysis by means of profilometer observations, density measurements by pycnometry, defects characterization and quantification and investigations on the melt pool morphology, the best process window is selected to have fully dense, defect-free parts. Furthermore, this study allows to have comprehensive insights on the effect of the parameters on the type of defects generated during the manufacturing.
Investigation on the topological optimization of cooling channels for extrusion dies
Authors: PELACCIA R.
Published: April 2023

Abstract. During the extrusion process, high temperatures are generated, due to friction and deformation works, potentially leading to profile and die defects. Among the suggested solutions aimed at controlling the thermal field of the process, the most accredited one involves the manufacturing of cooling channels at the mating face between the die and a third plate. Despite the proven efficiency of well-designed channels, the main drawback lies in the managing of the many variables involved that strongly affect the cooling efficiency and balancing. In this frame, aim of the work is to investigate the applicability of the topological optimization tool, proposed by COMSOL Multiphysics software, for the design of cooling channels in extrusion dies. To validate the tool, an industrial case study has been selected and results compared between not optimized and optimized cooling solutions.
Hot die forging with nitrided and thermally stabilized DLC coated tools
Authors: SIEGMUND M.
Published: April 2023

Abstract. Hot forging dies are subjected to high loads, which can lead to early tool failures. Abrasive wear, plastic deformation and thermal softening of the surface layer can be counteracted in particular by a high surface hardness. Thermochemical diffusion treatments and coatings are established as wear protection measures. DLC coatings, which feature excellent frictional properties and high hardness, are commonly applied on cold forging tools. However, the low coating adhesion to steel and the thermal stability of the diamond bond limit the current range of application. In this study, DLC coatings are applied in metallic treatment atmospheres with the aim of increasing the diamond bond’s temperature resistance. Furthermore, the influence of weak and intense nitriding to coating adhesion is investigated to reduce coating delamination. A pre-selection of modified DLC coatings for hot forging dies was carried out on the basis of hardness and scratch tests. The most promising tungsten DLC coating was tested in serial forging tests. Based on tool contour comparisons before and after forging, the potential as a wear protection measure for hot forging dies was determined. Tool wear was reduced by up to 29 % after 100 forging cycles with the tungsten DLC coating compared to the nitrided reference.
Beneficial effect of stress superposition on damage reduction in trimming processes
Authors: WEIß A.
Published: April 2023

Abstract. Trimming processes are frequently used for the manufacturing of fastener heads and similar parts with high precision requirements for specific regions of the part. Compared to conventional cold forging processes, the desired geometry can be achieved with significantly lower forces. However, trimming of sharp-edged geometries often leads to a highly inhomogeneous material flow and stress state in the workpiece, resulting in crack formation at such edges. To address this shortcoming, superposition of compressive stresses can be used to reduce the damage in the trimming process significantly. In this paper, the beneficial effect of stress superposition on damage reduction in a trimming process of a splined part is presented. By means of a numerical investigation using the FE-software DEFORM 3D, the impact of compressive stress superposition on the damage respectively crack formation at the edges of a splined part was investigated. Afterwards, trimming dies were manufactured and experimental investigations with three different trimming die geometries and different preform geometries were conducted to manufacture the splined parts. The edges of the splined parts were then characterized with a digital microscope and compared to the numerical results.
Determination of recrystallisation phenomenon in type 316 stainless steel VIM-VAR ingots during cogging operations
Authors: PAQUETTE A.
Published: April 2023

Abstract. This study is focused on understanding the effects of key process parameters on the onset of recrystallisation of coarse, elongated, and dendritic grains of the as-cast microstructure during ingot-to-billet conversion, consisting of successive cogging, upsetting, and reheating operations, in type 316 austenitic stainless steel. The microstructural characteristics of the initial as-cast ingot (e.g., size, orientation and morphology of grains), and the complex thermo-mechanical path have significant impact on recrystallisation behaviours, which make the existing material models inefficient of precise microstructure prediction. These investigations aim at exploring the recrystallisation mechanisms and their dependency on the forging process parameters. Cogging trails were conducted on VIM-VAR stainless steel ingots and microstructural observations were made to identify the recrystallisation mechanisms. Finite element simulations coupled with constitutive material models were developed in parallel, to enable microstructurally informed prediction of the cogging process. Thus, static and discontinuous dynamic recrystallisations occur in succession after reaching a threshold level of deformation during cogging. Grain growth occurred in the statically recrystallised grains during reheating. The importance of the reheating and the associated static recrystallisation on the efficiency of the billet conversion process in terms of grain refinement is thus highlighted.
Parametric identification on a dynamic behavior model for a forging machine
Authors: DURAND C.
Published: April 2023

Abstract. Dynamic models using masses, dampers and springs have been developed to represent the behavior of energy piloted machines. These models were proven to estimate more accurately the required amount of energy to forge a part. But how to identify the parameters of the model to accurately represent the behavior of a specific machine? In this study, the case of a strike without billet on a screw press is investigated, different target functions are tested to identify the model parameters and a sensitivity study of the optimization is performed. Results are encouraging.
An analytical approach for modelling incremental disk rolling process
Authors: ACAR S.S.
Published: April 2023

Abstract. In the context of the current study, an analytical method is developed to determine the deformation field of the workpiece under the forming roller for an unconventional incremental radial disk rolling (IRDR) process. As the industrial forming machine is in the development phase, the machine and process design requires a preliminary assessment tool that is sensitive to process parameters and roller geometry. Establishing a parametric relationship between process parameters and induced deformation field enables designers to determine the parameters needed to obtain the target geometry and microstructure as well as the forming machine requirements. Instantaneous roller-workpiece interface, i.e. contact zone, and cross-sections that plastic flow occurs in between are calculated. The contact zone is spatially discretized to two-dimensional surface elements. The principle of volume conservation during plastic deformation is utilized to obtain velocity fields in three dimensions. Strain rate distributions are calculated by taking the gradient of the velocity fields in respective directions. Average values of strain at each cross-section are the accumulated plastic strain that is created by the multiple circumferential passes of the roller and computed numerically, accounting for different strain rates and contact times at each pass. Obtained contact zone geometries, deformation fields, and the effect of different process parameters are discussed. Results show that deformation occurs mainly in the circumferential direction and the tangential velocity of the roller in the circumferential direction has a more pronounced effect on the deformation than the radial advance of the roller per revolution.
Heat assisted V-bending characteristics of high strength S700MC steel
Authors: GÖRTAN M.O.
Published: April 2023

Abstract. Increasingly stringent regulations force automotive manufacturers to reduce their product weights without compromising passenger safety. To overcome this problem, high strength steels are used that enable a higher payload capacity whilst reducing the plate thickness and overall weight. However, high strength steels are generally associated with lower formability and significantly greater springback compared to mild steels. In the current study, bendability characteristics of high strength S700MC steel in mild temperatures are investigated using V-bending tests. A temperature range between 25°C and 650°C is analysed. Springback characteristics as well as hardness distribution along the thickness direction in the bent area is investigated for several bent samples.
Nonlinear stress path experiment using mild steel sheet for validation of material model
Authors: TAKADA Y.
Published: April 2023

Abstract. A linear stress path (LSP) experiment was performed using uniaxial and biaxial tensile tests with a cold-rolled mild steel sheet (SPCD; nominal thickness: 0.8 mm) as the test material. In the LSP experiment, nine LSPs were applied to the specimens to measure the contours of plastic work and the directions of the plastic strain rates, β, for a plastic strain range of 0.002 ≤〖 ε〗_0^p ≤ 0.234. Then, the Yld2000-2d yield function (Barlat et al., 2003) was used to identify a material model that accurately reproduces the experimental data observed in the LSP experiment. Furthermore, a nonlinear stress path (NLSP) experiment was performed. The NLSP consists of two linear stress paths with σ_x:σ_y = 4:1 and 1:1, and a curved stress path connecting the LSPs. The measured work hardening behavior and β values were compared with those calculated using the Yld2000-2d yield function identified from the LSP experiment. It was found that the deformation behavior of the test sample predicted by the material model determined from the LSP experiment clearly shows some deviation from that observed for the NLSP experiment.
Hybrid SPD process of aluminium 6060 for microforming
Authors: PRESZ W.
Published: April 2023

Abstract. The increasing share and expansion of miniature devices requires the mastery of miniature parts production, including metal parts. In metal microforming, due to the conditions of mechanical similarity, the aim is to use materials with the smallest grain. Ultra-fine-grained metals (UFG) fulfill this requirement. These metals can be obtained, inter alia, in SPD processes such as ECAP. The work uses the extension of the SPD based on ECAP with additional metal forming operations necessary to obtain blanks for microforming in the form of a 0.2 mm foil. Three variants of the technological process were performed. This foil was then subjected to a micro-drawing operation aimed at determining the influence of the foil preparation process on the sheet metal microforming process flow.
Determination of the forming limit curve of locally annealed aluminum blanks
Authors: Piccininni A.
Published: April 2023

Abstract. The research of innovative manufacturing routes to improve the complexity of structural Aluminum (Al) components and reduce the vehicles’ weight remains an open question. The adoption of short-term heat treatments to obtain an optimized distribution of properties has shown great potential in enhancing the formability of Al alloys at room temperature. Such a complex approach needs the implementation of methodologies based on numerical simulations able to correctly simulate the forming process. Accordingly, the definition of a proper identification procedure to provide reliable constitutive parameters, possibly employing a limited number of tests, becomes crucial. In this work, we introduce a novel methodology for the evaluation of the Forming Limit Curve (FLC) of laser annealed AA5752-H32 sheet based on the material information from different heterogeneous tests carried out in specific tribological condition, i.e. in absence of friction. Therefore, we investigate an experimental procedure to simultaneously generate an equi-biaxial mechanical state over a wide range of annealing conditions by means of hydraulic bulge test. The results are integrated with full-field data from uniaxial tensile and plane strain tests to provide a testing protocol for the characterization of the failure behavior accounting for the different temperature/time conditions of the sheet metal.