bluuebunny/crossref_metadata_2025_split huggingface dataset:
Implicitization of the Vegter Yield Criterion
Authors: Sheng J , Yang S-Y , Tong W 
Published: May 2022

Abstract
An advanced yield criterion plays a central role in rate-independent plasticity modeling of sheet metals in automotive and other industrial applications. Different from many non-quadratic yield criteria based on implicit polynomials, Vegter yield criterion is piecewise and quadratic as it is originally constructed by interpolation of several biaxial stress states using multiple second-order Bézier curves. Additional efforts in recent years have made Vetger yield criterion more user-friendly, flexible and robust for sheet metal forming applications. Nevertheless, Vetger yield criterion has only been presented in its parametric formulation in the literature. This work describes a method of reformulating the existing Vetger Lite yield criterion into the implicit form that is more commonly used in the conventional sheet metal plasticity modeling. The potential benefits of using both the original parametric and the new implicit forms of Vegter yield criterion for material parameter calibration, convexity certification, and computational simulations are discussed.
Upset bulging as a preforming operation for hot metal gas forming of 22MnB5 tubes
Authors: Alimov A , Haase R , Sviridov A 
Published: May 2022

Abstract
Hot Metal Gas Forming (HMGF) is a coupled process of gas forming and quenching of tubes. This process allows to obtain complex and accurate geometry due to the elimination of springback and high mechanical properties due to the formation of martensite, as a result, the weight of the parts can be reduced. HMGF is widely used in the aerospace and automotive industries to make critical parts from high hardenability steels such as 22MnB5. A typical hot stamped component has 1000 MPa yield stress and 1500 MPa ultimate tensile strength. The main challenge of HMGF process is a significant material thinning and cracking due to the biaxial tension stress state. The paper proposes a preforming method for increasing the forming limits of HMGF by the cold upset bulging of tubes by means of the additional volume of material in the deformation zone. This method allows to obtain one or several waves in the cross section of the tube, which helps to increase the minimum workpiece wall thickness after the forming process by more than 40% and to reduce a probability of the crack formation.
Experiments on forming behaviour of the aluminium alloy AA6016
Authors: Norz R. , Valencia F.R. , Gerke S. , Brünig M. , Volk W. 
Published: May 2022

Abstract
Investigation of the sheet metal formability is an important issue in the design of components. During metal forming different deformation histories occur which may cause various damage and failure mechanisms on the micro-level affecting the quality of products. Therefore, description of the material characteristics by means of a linear limit change curve is not sufficient because the remaining formability and the fracture processes also depend on deformation history. For this purpose the aluminium alloy AA6016 is systematically investigated in order to obtain their forming capability as well as the damage and fracture behaviour after complex deformation paths. Different uniaxial tests with various initially unloaded and preloaded specimens have been performed to identify the effect of the forming history, the loading direction and the stress state on the formability and the mechanical parameters of the investigated material. The results can be used to propose a critical ratio between the pre-strain and the change in loading direction from which on shear failure occurs instead of necking behaviour leading to the loss of formability.
Determination of temperature dependence in Modified-Mohr-Coulomb failure model for process simulation of shear cutting
Authors: Behrens B-A , Brunotte K , Wester H , Kock C , Kildonaviciute D 
Published: May 2022

Abstract
Shear cutting is a proven process for chip-less separation of metals and used as a cost-effective production method. The process design of shear cutting is usually based on time and cost intensive experimental tests. Therefore, numerical depiction of the process offers great potential to reduce these practical tests. An important aspect hereby is the representation of temperature dependency of the material. However, the classical Modified-Mohr-Coulomb (MMC) failure model does not depict this effect directly. Therefore, the objective of this paper is to investigate the temperature dependency of MMC failure model for simulating shear cutting. The required data is obtained from tensile tests on miniaturised specimens under variation of temperature on dual-phase steel DP1000, using an additional optical measurement system. To determine stress triaxiality, Lode angle parameter and plastic strain at failure, the experimental tests are simulated using the Finite-Element simulation program ABAQUS. The MMC failure surfaces are fitted using the least squares method in Matlab. With this approach, temperature dependent MMC failure model was built to be used for shear cutting simulation of DP1000 steel.
An approach to describe edge ductility
Authors: Kesti V , Folmerz M , Vierelä R , Rautio P , Ruoppa R , Plosila P , Kaijalainen A 
Published: May 2022

Abstract
One of the challenges of utilizing advanced high-strength steels is their limited ability to withstand the forming of cut edges. Large production quantities of parts often lead to mechanical punching/shearing processes in blank preparation, providing a challenging starting point for forming processes. The most commonly used edge ductility test is the ISO 16630 hole-expansion test to describe stretch-flangeability properties. However, this method has been widely criticized for its large-scatter, unreliable results and the fact that it covers only a certain stress-strain state of cut edge forming. In addition, it does not provide enough data to be reliably used in forming simulations to predict edge failures. This paper presents an approach to create a more comprehensive way of describing overall edge ductility. Multiple edge forming test methods coupled with digital image correlation (DIC) were selected in order to investigate different edge loading scenarios in both open and closed trim line forming situations. Data regarding limiting local strain before cracking was collected for several steel grades, and results are gathered in 2D and 3D “Edge FLC”-figures. Attempts to utilize these results for simulation purposes are also presented. Results indicate that this approach can be useful to evaluate overall edge forming limits.
Optimum blanking clearance choice method by an approach coupling experimental trials and simulations
Authors: Schreiber P , Rizk J , Rachik M , Maillard A 
Published: May 2022

Abstract
Blanking process of sheet metal is accomplished by a shearing action on a thin plate placed between two sharp cutting edges, known as “punch” and “die”. The main problem of this sheet metal cutting technology, that causes major shutdowns of the press machine, is the punch wear. Among all blanking parameters, the clearance set between the punch and the die has the major influence on tool wear. In this context, our study focuses on identifying the optimum blanking clearance that guarantees a maximum abrasion and chipping wear reduction for different sheet metal materials and different blanking operations. The developed approach combines experimental blanking tests and numerical simulation of blanking processes. Based on assumptions made in this paper, links are established between the stripping force and the abrasive wear behaviour of punching tools and also between the maximum pressure on the face of the punch and the risk of chipping. Using these links, criteria have been developed allowing to propose an optimum blanking clearance for all the configurations tested in this paper. A next step of this study consists on applying the optimum punch-die clearances in a variable way along a complex blanking shape and realizing experimental tests to compare the results (tool life and edge quality) with a constant blanking clearance.
Development of a high-temperature double-layer bulge test for failure prediction in gas-based hot forming of a high-strength aluminium alloy
Authors: Teeuwen T , Baru N K , Tilly K J , Bailly D , Hirt G 
Published: May 2022

Abstract
In order to meet the continuously increasing environmental concerns, automotive lightweight concepts of replacing steels with high strength aluminium alloys are one promising solution. Therefore, complex automotive structural components manufactured with new processes like rapid gas-based hot sheet metal forming can become a key factor from a forming technology point of view. A product and process development phase, which is mainly assisted by numerical simulations, mandates knowledge of the material forming limits under the process conditions. The aim of this work is to determine the FLD of a 6xxx precipitation-hardening aluminium alloy within the solution heat treatment temperature range under gas-based hot forming process conditions. For this purpose, a hydraulic double-layered bulge test, as introduced by Banabic, is used as the basis and a high-temperature test setup as well as a characterization methodology are established. FE simulations are utilized to optimize the specimen geometries aiming at specific strain paths. Experiments are conducted with the optimized specimen geometries and the high-temperature FLD is extracted. The FLD is further used in simulations for process parameter identification for failure-free gas-based hot forming of a laboratory scale benchmark component. Experimental validations showed the reliability of the methodology and the determined FLD for failure prediction in the novel forming process.
Accurate plane strain compression test validation
Authors: Neag Adriana , Hu Qifan , Balan Tudor 
Published: May 2022

Abstract
Large strain characterization of sheet metals has become increasingly important with the generalization of advanced high strength steels, for which the tensile test provides data over a very reduced strain range. Among the numerous alternative characterization tests, the plane strain compression test (PSCT) requires a small amount of material and classical testing machine and acquisition. PSCT was mainly used for hot forming characterization, but recently it has been proved sufficiently accurate for application in cold metal forming. This work provides an in-depth validation of the PSCT by means of the finite element method. When converting the PSCT force-displacement curve into a stress-strain curve (flow curve), several analytical corrections are applied. Several sets of such corrections terms were proposed in the literature, some of which are consistently used by all authors, while others being only used in some papers. The FE simulation of the test was used in order to validate these correction terms and their hypotheses. The originality of the approach is the design of a sequence of test configurations which allow for the individual validation of each and every one of the correction terms concerning the effect of several test parameters. The FE simulations showed that the analytical exploitation of the PSCT provides a very good accuracy. They helped identifying the most suitable correction terms to consider.
Influence of criteria on the determination of forming limits in thickness reduced cruciform specimens
Authors: Wang Z , Guines D , Leotoing L 
Published: May 2022

Abstract
Biaxial tensile test methods using cruciform specimens have been drawing attention as an effective approach to characterize sheet metal formability. The cruciform specimens usually adopt a thickness reduction at the central area to achieve a relatively large strain gradient for localized necking and fracture investigation. For conventional tests, many criteria have been proposed to determine the forming limits at necking, however, none has been widely accepted and applied to the cruciform specimens with non-uniformed thickness reduction. Therefore, in this work, different existing necking criteria are applied and discussed for numerical procedure in order to define an appropriate necking criterion for the thickness reduced cruciform specimens. AA6061-T4 sheet with a thickness of 2mm is used as a target material. The predicted forming limit curves are compared for different criteria, and the feasibility of each criterion is discussed in detail. Thanks to two dedicated specimens proposed by the authors, forming limits are determined for a wide range of strain states.
Investigation on tool properties for the production of components with micro textured surfaces
Authors: Reck M , Merklein M 
Published: May 2022

Abstract
Defined surface micrcotextures offer potential for the friction reduction in elastohydrodynamic contacts and can thus increase the energy efficiency of technical systems. The production of prostheses, where microtextured surfaces can provide anti-bacterial effects is another application area. To manufacture these components economically in large quantities, forming processes are to be aimed at. Since lightweight parts are crucial in most application areas, the forming of sheet metal is the subject of current research. A major aspect of the presented investigation is the behavior of tool materials for the production of such microtextured sheet metal parts. Applying microtextures of varying geometries to the tools is a key challenge. Limitations in the accuracy of electrical discharge machining processes for the fabrication of micro cylinders, prisms and cuboids are therefore analyzed on the high-speed steels 1.3343 and 1.3244. In addition, the tool surfaces are characterized regarding their friction properties with case hardening steel as a contact partner. In this paper, the tool friction is analyzed for the steel 1.7131 (16MnCr5) with an initial sheet thickness of t0 = 2.4 mm, which is often utilized for high-wear applications due to its high strength and toughness. In this context, the friction behavior of the wax-containing lubricant Beruforge 150 DL made for bulk forming processes is compared with zinc-free high-performance lubricants Raziol CLF 65-400 of varying viscosity.
TriboForm® software evaluation for ArcelorMittal Steel Products
Authors: Bouzid A , Bour H 
Published: May 2022

Abstract
In numerical simulations, input data should be correctly defined to enable reliable numerical predictions, close to experimental observations. The purpose of this study is to better take into account the tribological behaviour of ArcelorMittal steel products during the stamping process. TriboForm® is an important additional software solution for the simulation of tribology, friction, and lubrication in sheet metal forming process and enables the generation of multiple friction models. A comparison between experimental observations and numerical predictions was investigated for three ArcelorMittal steel grades (CR4-GI, CR180BH-GI+NIT and CR440Y780T-DH-GI) on several stamping parts. This study illustrates the interest of TriboForm® friction law compared to a standard and constant predefined friction coefficient.
Towards a real-time tool state detection in sheet metal forming processes validated by wear classification during blanking
Authors: Kubik C , Molitor D A , Rojahn M , Groche P 
Published: May 2022

Abstract
The potential of data for inline detection of changes in the physical state of sheet metal forming processes has been proven over the last decade. However, with production rates exceeding 300 parts per minute the time available for a workpiece-related processing of sensor data is reduced. Therefore, the analysis of large data sets is outsourced to the cloud taking advantage of the high computing power provided there. But within this cloud-based computing paradigm, the speed of data transmission hinders real-time analysis of data and causes latency between fault detection and its occurrence. To overcome this bottleneck, this study aims to evaluate a data-based monitoring (DBM) approach for estimating process states in high speed sheet metal forming in terms of their suitability for a decentralized analysis at the edge. Thereby, the DBM is evaluated according to the model accuracy and the absolute computing time. In order to quantify these key performance parameters and the applicability of the DBM on edge devices, a classification of 16 wear states during blanking is considered. Based on the key performance parameters, an optimal DBM approach for decentralized analysis is proposed and an empirical formulation is provided to estimate the absolute computing time depending on the computational resources used for data processing.
On the reliability of yield functions in deep drawing simulations
Authors: Ghiabakloo H , Manopulo N , Mora J , Carleer B , Van Bael A 
Published: May 2022

Abstract
In sheet metal forming simulations, the yield functions are usually calibrated based on experimental data, and validated by comparing the modelled and measured r-values and (in more advanced models) yield stresses along various in-plane directions. The fitted yield function should ideally reproduce (or interpolate) all the experimental values used for the fitting. However, this requirement does not guarantee accurate results in a forming process simulation, and it can even lead to unexpected results. The performance of a yield function, in addition to the fitting procedure, depends on the active loading modes which the material experiences during the simulation. The active loading modes are in turn determined by the die geometry as well as the process parameters like blank holder force and lubrication. As a consequence, the performance of a yield function, which is fitted to simple experimental data, is not identical for different forming conditions. Therefore, the application of each model is usually limited to a range of materials and processes, and this applicability is often evaluated based on experience. In the present study, we examine three phenomenological yield functions and a new crystal plasticity based material model for cup drawing process simulation with an AA6016-T4 aluminium alloy. These functions are different in their input data types used for the calibration. The results surprisingly shows that the models with more experimental data (in particular, yield stresses in different directions) in their formulation not only predict unexpectedly wrong results, but also show strong sensitivity to some of those additional input data and even to modelling parameters like the friction coefficient.
Influence of the forming process on springback
Authors: Durmaz U , Heibel S , Schweiker T , Prabhakar A. , Merklein M 
Published: May 2022

Abstract
The use of advanced high-strength steels (AHSS) is associated with increased springback and represents a great challenge for today’s press shops with regard to the dimensional accuracy of cold-formed sheet metal parts. Springback, its appearance and characteristics are mainly dependent on the stress state introduced by the forming process and part geometry before opening the tools. With the aim of determining the influence of the forming process on springback, sheet metal forming simulation is used in this contribution to analyze a hat profile from a high-strength dual-phase steel (DH1000) by three different forming processes: crash forming, bending and drawing. For this purpose, the stresses generated by these processes and resulting springback are examined considering the respective forming history. The results show the strong influence of the material flow controlled by the process and tool geometry on the stress state before springback, which leads to significant differences in the springback of the hat profile among the forming processes: springback increases from crash forming to bending and drawing.
Assembly simulation development and validation project with industrial applications
Authors: Tinti Fabrizio , Fontana Marco , Scintilla Leonardo Daniela , Mirabile Annalisa , Carleer Bart 
Published: May 2022

Abstract
Full digitalization has been applied more intensively in the automotive industry. The virtual engineering of single part is established since many years. Currently, the digital process chain is expanding to the assembly process. The assembly engineering teams should be effectively supported to define the assembly process; the assembly process should make products that fulfil the required quality requirements. A detailed simulation representing the future assembly process has to be setup. In an early phase based on CAD data, in the course of the engineering process the model can be enriched with forming simulation data and even real measurement data. Based on the assembly definition, critical issues can be identified and fixed already in the virtual world. Detailed evaluation of the geometrical deviation of the assembly can be made. This methodology is validated on an industrial automotive component.
Evaluating the influence of the deformation of the forming tools in the thickness distribution along the wall of a cylindrical cup
Authors: Oliveira M C , Neto D M , Pereira A.F.G. , Alves J L , Menezes LF 
Published: May 2022

AbstractThe Swift cup drawing test has been adopted for evaluating sheet metal deformation properties, namely the material formability assessed through the limiting drawing ratio. Since the strain path of the points located on the flange is between uniaxial compression and pure shear, this region is subjected to thickening. If the thickness of the drawn flange is larger than the gap between the punch and the die, cup wall ironing will occur. Therefore, the ironing forces can lead to significant elastic deformation of the forming tools (punch and die). The main objective of this study is to evaluate numerically the deformation of the forming tools during the deep drawing-ironing process of a cylindrical cup. Then, the effect of that deformation on both the earing profile and the evolution of thickness along the circumferential direction, at different heights, is analysed. The material studied is the AA 6016-T4. Since both the thickness strain and the earing profile are strongly influenced by the adopted yield criterion, the study considers the classical quadratic one proposed by Hill and a non-quadratic proposed by Cazacu and Barlat. The process conditions considered are the ones from EXACT, the ESAFORM Benchmark 2021, enabling the comparison with experimental results.
Advanced part design method for springback minimization of stamped sheet metal car body components
Authors: Birkert A , Hartmann B , Nowack M , Petker A , Scholle M , Zimmermann P , Kraft T. 
Published: May 2022

Abstract
The requirements for high-strength and low-weight car body structures prove challenging for the stamping process and cause growing problems with the elastic springback. Compensation approaches such as the geometrical adjustment of the stamping dies by the amount of and in opposite direction to the springback can be an effective solution in many cases. However, this approach can only lead to satisfactory results if the scatter of the springback is considered, controlled and in the best case reduced. The reduction of the scatter can be provoked by adaption of the part design. Therefore, different methods such as the topology optimization method, the so-called line-of-force method and shape optimization can be applied. In the present work an advanced topology optimization method is suggested. Based on the decomposition of the springback deformation into membrane and bending components, the most efficient optimization of the part design is found relying on unconventional topology optimization. For the proposed adapted topology optimization approach the excellent results are also confirmed when applied to the industry-relevant case of a truck rear panel.