bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of blank-holder force on springback of ultra-thin copper sheets
Authors: Ayachi’ N , Guermazi N , Manach PY 
Published: June 2021

Abstract
After forming by plastic deformation, it’s rare that the part produced retains its shape perfectly after removing the tools, the shape and dimensions that the tools imposed on it. This change in shape is mainly due to springback. This study focuses on the springback of U-shaped channels made of thin sheets of beryllium copper alloy 0.1 mm thick. The intensity of springback depends on several factors of part geometry and process parameters. Among the parameters of the process, we investigated the clamping force, which is an essential factor influencing the final shape of the part. It is shown that the springback is inversly proportional to the clamping force. As a consequence, there is no significant change of the geometry of the final part. Indeed, uneder high clamping force, the internal stresses (already existing in the material) become very important, which makes it possible to attenuate significantly the local moment effect in bending. The result is an uniform distribution of residual stresses in the thickness of the sheet which is studied in this paper.
Adapted part design methods for springback minimization of stamped sheet metal car body components
Authors: Birkert A , Dreiseitel F , Hartmann B , Held T , Hetterle O , Markin M , Scholle M 
Published: June 2021

Abstract
In sheet metal forming, both the dimensional accuracy of the manufactured parts and the robustness of the forming process are significantly compromised by elastic springback effects. In contrast to traditional compensation methods mostly relying on modifications of the tool geometry, a part geometry-based approach reduces the amount of springback by appropriately manipulating the part stiffness through slight modifications of the part geometry. To date, part-geometric measures are mostly based on practical experience and trial-and-error processes resulting in a need for simple and effective simulation-based approaches. In the present work three novel simulation-based approaches for a suitable modification of structural component design are suggested relying on unconventional topology optimization, the so-called line-of-force method and shape optimization. First tests with a classical hat profile reveal that the optimized geometries, compared to the nominal one, lead to significant reductions of the springback after stamping and simultaneously to a notable decrease of the process variation when parameters of the forming process are varied slightly. For the adapted topology optimization approach the excellent results are also confirmed when applied to the industry-relevant case of a truck rear panel.
Experimental and numerical study of springback effect of advanced high strength steel in a V-shape bending
Authors: Julsri W , Sanrutsadakorn A , Uthaisangsuk V 
Published: June 2021

Abstract
Advanced high strength (AHS) steel sheets are increasingly used for the production of various automotive structural parts. The components of new lightweight vehicles have very complex Shapes, for which more precise forming procedures are required in order to achieve a desired geometry. Hereby, springback occurrences of such AHS parts are often the most critical concern. In this work, it aimed to investigate springback effects of the AHS steel grade 980 in a V-shape bending process. Experimental bending test and its corresponding FE simulations were conducted. The Hill’48 and Barlat89 yield criteria, and the Yoshida-Uemori (Y-U) kinematic hardening model were applied. The yield function parameters were obtained from the tensile tests of samples in various orientations. The Y-U model parameters were determined from a cyclic tension-compression test and were afterwards calibrated with the 1-element simulation. The resulted bend angles measured from the experiment and predicted by FE simulations using the different models were compared and evaluated. For the bending in this work, the Hill’48 and Barlat89 models showed the predictive errors of springback angle 1% and 2% higher than the Y-U model, respectively. The accuracy of springback prediction could be improved by the Y-U model using C1 and C2
parameters around 1%. In addition, effects of sheet thickness and punch radius on the springback were afterwards studied and discussed by using the Y-U model.
The Effects of Piercing Methods on Burring Formability under Practical Hole Diameter
Authors: Urushibata R , Ito Y 
Published: June 2021

Abstract
Advanced High Strength Steels (AHSS) sheets are used for automobile bodies to comply with the demands for weight reduction and collision performance. However, as the tensile strength is increasing, the ductility of steel sheets is decreasing. Therefore the forming defects such as fractures may occur. In case of chassis components, it is needed to prevent stretch flange fractures from burring edge. There are following methods to improve burring formability. 1) Double Punching Method (DPM): punching blank coaxially with a pre-punched hole. 2) Humped bottom Punch Method (HPM): punching blank under tension using a punch with a humped part. However, there isn’t much previous evidence evaluating the burring formability of DPM and HPM under practical punching diameter for chassis components. In this study, the burring formability using DPM and HPM has been evaluated under 30mm punching diameters, through experiments and FEM analysis. The results showed that: 1) DPM: deforming mainly occurred in scrap side and equivalent plastic strain was reduced on the punched edge surface. 2) HPM: the burring formability requires both increasing stress triaxiality in blank and reducing equivalent plastic strain applied by the preceding bumped part. Under identical conditions, the same improvement effect of DPM was obtained with HPM.
Influence of pass reduction in cold rolling on damage evolution in deep drawing of rotationally symmetric cups
Authors: Nick M , Liebsch C , Müller M , Weiser IF , Hirt G , Bergs T 
Published: June 2021

Abstract
Improvement of component performance by controlling the damage state after metal forming enables a reduction in sheet thickness and, consequently, in component weight and material cost. To establish methods for controlling damage in finished parts, the entire process chain from steelmaking and casting through hot and cold rolling to deep drawing must be considered. Previous research has shown that in hot rolling of an S355 steel, the influence of pass reduction on damage in the hot strip disappears when the accumulated pass reduction becomes large. However, the influence of cold rolling parameters on damage and specifically on its evolution in subsequent forming processes has not yet been systematically investigated. In the present work, specimens of the the mentioned S355 steel are cold rolled with two different pass reductions and heat treated to obtain a DP800 dual phase steel. These specimens are deep drawn into rotationally symmetric cups with variation of the drawing die radius. Sheet specimens and deep drawn cups are investigated using scanning electron microscopy to determine the respective void area fractions. While no influence of height reduction on the void area fraction after cold rolling is found, the void area fraction after deep drawing differs with variation of the pass reduction. This effect is connected to the formation of a larger number of small voids in the material rolled with a larger pass reduction.
On the mechanics of edge cracking and the reliable determination of edge formability limits
Authors: Manopulo N , Chezan A R , Atzema E , Picas Anfruns I , Carleer B , Pilthammar J , Sigvant M 
Published: June 2021

Abstract
Blanked edge surfaces are rough and hardened. They therefore lead to inhomogeneous deformation on the edge, which can trigger localization within the shear affected zone (up to few mm from the edge). The size and extent of these phenomena are primarily a function of the shearing process and are only marginally coupled to the global/homogeneous deformation behavior of the blank. A direct numerical simulation of such local deformation effects would require a prohibitively high resolution to capture the microgeometry of the edge and thus remains unfeasible in the current industrial practice. A predictive model can therefore only be achieved by determining limit strains on the edge, which are compatible with the homogeneous numerical framework used. The present contribution aims discussing the basic mechanics of edge cracking based on tensile tests with edges blanked with different die clearances. The local and global strain evolutions in the vicinity of the edge are analysed and a new evaluation procedure is proposed for the reliable determination of limit strains. The application of this method in industrial context is also discussed.
Potentials for material card validation using an innovative tool
Authors: Eder M , Gruber M , Manopulo N , Volk W 
Published: June 2021

Abstract
For the numerical description of the material behavior of sheet metals, there is a large diversity of models. These models vary strongly in terms of complexity and calibration effort. Before using a material model for numerical analyses, it is essential to validate it. The paper presents an innovative tool that allows generating a well-founded database for a comprehensive validation of the yield locus description with few and simple tests: the MUC-Test (Material Under Control). The special geometry of the punch and die generates complex strain distributions in sheet metal samples during forming. The experiment covers the strain range between uniaxial and equibiaxial tension. The contribution shows the potential of this innovative tool by using the test results of three different material classes. Using numerical analyses, sensitivities of different material model parameters were investigated. Thereby, the focus lies on the curvature of the yield locus in the area between uniaxial and equibiaxial stress state.
Constitutive modelling of Usibor® 1500 sheets after intercritical quenching
Authors: Dastgiri M. S. , Thakkar R. , Shi J. , Sarraf I.S. , Green D. E. 
Published: June 2021

Abstract
In this study, 0.9 and 1.8 mm thick Usibor® 1500 sheets were subjected to intercritical quenching by heating to 760-930°C and quenching at a controlled rate. The tensile behavior of as-quenched Usibor® 1500 was experimentally obtained using uniaxial tension tests at strain rates ranging from 0.001 to 0.25 s−1. The constants in the hardening models, including Johnson-Cook, were optimized using a Genetic algorithm and linear regression for each condition at each strain rate. Then, these models were numerically modified to account for heat treatment dependency. Uniaxial tensile tests were simulated using the fitted models and compared to experimental flow curves and strain distribution maps to determine the accuracy of the prediction of each model. Optical microscopy was used to determine the volume fraction of each phase using image processing tools and these characteristics were used to explain the behavior of Usibor® 1500 after intercritical quenching. It was found that intercritical quenching process parameters determine the distribution and morphology of each phase and consequently the range of mechanical properties. This model can be used to simulate the deformation of hot-stamped components with tailored properties produced under controlled austenitization.
Lightweight design of an automotive lower control arm using topology optimization for forming process
Authors: Sookchanchai K , Olarnrithinun S , Uthaisangsuk V 
Published: June 2021

Abstract
The global environmental regulations have become very strict nowadays, thus most car manufacturers aim to fulfil such restrictions by different strategies including lightweight technologies that contain design, advanced materials and manufacturing. Hereby, optimally designed geometries of structural components needs to be conformed to their functional requirements and manufacturing process. In this work, a topology optimization (TO) was performed for weight reduction and performance improvement of a lower control arm (LCA) of vehicle suspension. First, FE simulations of the recently used LCA were performed under different load cases according to the actual application. The resulted stress distribution and overall stiffness were gathered as the baseline reference. Then, TO procedure was carried out and critical regions for load carrying were classified. In addition, the member-size constraint was applied to enable a LCA layout, which can be likely produced by metal forming process. The introduced optimization method serves as a guidance in practice for the lightweight design of other automotive stamping parts.
On the use of fixed point translations as input variable for digital twins in deep drawing compared to current methods
Authors: Ryser Matthias , Hora Pavel , Bambach Markus 
Published: June 2021

Abstract
Recent work aims at the inverse parameter estimation in deep drawing using pretrained surrogate models for the detection of the current process, material or tool parameters. The use of the methodology requires the definition of state variables to describe the current process state. Whereas our recent work makes use of draw-ins and local blankholder forces, other approaches from the literature also use skid-lines measured after the deep drawing process. For the future, the solution with even higher information content would be to detect the global strain distribution on the final part and use it as a state variable for process detection, which has not been documented in the literature to the best knowledge of the authors.
In this work, we present a first step into this direction by comparing the surrogate model based parameter estimation by using draw-ins and by using the movement of material fixed points on the blank over the deep drawing process. The result shows that the mathematical methods used for parameter prediction based on draw-ins can directly be used for the prediction with fixed point translations as reference. For the investigations, a cup drawing process is used.
Simulation of Dynamic Effects in Progressive Die Operation and Control
Authors: Budnick D. , Steinlehner F. , Weinschenk A. , Volk W. , Melek W. , Worswick M. , Huhn S. 
Published: June 2021

Abstract
The demand from the automotive industry for increasingly complex sheet metal components and higher throughput in progressive die operations has led to the increased integration of sensors and control-systems in the sheet metal forming process. However, current control-systems used in sheet metal forming are often limited to measuring the state of the tooling during the forming process, neglecting the dynamic effects of the strip during its transfer between tooling operations. Developing a control strategy that accounts for the strip dynamics requires knowledge of how various process parameters influence the strip behaviour during both the transfer and forming stages. FE element models can accurately model the behaviour of sheet metal, but by themselves cannot identify a robust control strategy. Machine learning can solve this issue by constructing a probabilistic representation for the data generated from FE simulations to be used to identify a control strategy for sheet metal forming. The goal of this work is to conduct a parametric study on a progressive die FE model and evaluate the influence of various input parameters. The data collected from this FEM study will be used to construct a neural network model that will inform a control strategy for a progressive die.
Robustness analysis with LS-OPT® and LS-DYNA® for sheet metal forming simulations
Authors: Merten M , Liebold K , Haufe A 
Published: June 2021

Abstract
This contribution shows the application of the optimization and probabilistic analysis program LS-OPT on the drawing step of a generic fender geometry simulated with LS-DYNA to judge on the robustness and reliability of the model. Input variables of a typical sheet forming simulation that are subject to uncertainties are alternated automatically within the framework of LS-OPT based on an inherent Monte Carlo approach. Using metamodel approximations as well as classifiers to evaluate statistical results is discussed. The influence of the variation of the input variables on typical sheet forming results is investigated, e.g. thickness reduction and the Formability Index. Alternated parameters were material properties like yield and tensile strength.
Process Linearization for Closed-Loop Control of Incremental Sheet Forming
Authors: Havinga Jos , Sikkelbein Dylan , Boogaard Ton van den 
Published: June 2021

Abstract
Incremental sheet forming has, despite its great flexibility, not yet been widely adopted by the forming industry, due to its limited geometric accuracy. One of the approaches to overcome this problem is the development of closed-loop control systems. Such control systems are mostly based on linearization with respect to a nominal toolpath. In this work, different approaches to create such linearized process models are reviewed. By implementing the models in a numerical simulation of a model predictive control system for incremental sheet forming, it is investigated how manufacturing accuracy is affected by the chosen linearization. Based on these results, the validity of the most commonly used linearization method is critically discussed. Furthermore, it is shown that the geometric accuracy can be improved by extending the process model with a time-varying component that contains historical information about past control actions.
Predicting springback variation and process-reliable tolerance limits of outer car-body panels by stochastic sheet metal forming simulation
Authors: Brix P. , Liewald M. , Eckstein J. 
Published: June 2021

Abstract
Modern car-body design entails increasing requirements for the dimensional accuracy of outer car-body panels. However, tolerance limits to be met in this regard are based on specifications from component engineering aimed at ensuring dimensional accuracy of the product, less on real structural springback behaviour of outer car-body panels. Process-reliable tolerance limits for outer car-body panels can be characterized by a bandwidth in springback variation caused by fluctuations in material characteristics and process parameters during production. Differences between assumptions from component engineering and real structural springback behaviour of outer car-body panels thus leads to avoidable iterative corrections in die manufacturing and following processes. Therefore, the goal of this research work presented in this paper is to predict springback variation potentially occurring during production already in the virtual design stage of a car-body and hence set process-reliable tolerance limits. Stochastic sheet metal forming simulation is used for prediction of springback variation. Here, deterministic multi-stage springback simulation of a sidewall panel is extended by stochastic variation of material properties and process parameters. Simulation results are validated by measurement reports from series production. Results presented show strong fit in characteristics of springback variation between stochastic simulation and series measurement reports. In future, stochastic simulation results can be fed back into component engineering, making die manufacturing and following joining and assembly processes more effective.
Thalamocortical Mechanisms Regulating the Relationship between Transient Beta Events and Human Tactile Perception
Authors: Law Robert G , Pugliese Sarah , Shin Hyeyoung , Sliva Danielle D , Lee Shane , Neymotin Samuel , Moore Christopher , Jones Stephanie R 
Published: June 2021

Abstract
Transient neocortical events with high spectral power in the 15–29 Hz beta band are among the most reliable predictors of sensory perception. Prestimulus beta event rates in primary somatosensory cortex correlate with sensory suppression, most effectively 100–300 ms before stimulus onset. However, the neural mechanisms underlying this perceptual association are unknown. We combined human magnetoencephalography (MEG) measurements with biophysical neural modeling to test potential cellular and circuit mechanisms that underlie observed correlations between prestimulus beta events and tactile detection. Extending prior studies, we found that simulated bursts from higher-order, nonlemniscal thalamus were sufficient to drive beta event generation and to recruit slow supragranular inhibition acting on a 300 ms timescale to suppress sensory information. Further analysis showed that the same beta-generating mechanism can lead to facilitated perception for a brief period when beta events occur simultaneously with tactile stimulation before inhibition is recruited. These findings were supported by close agreement between model-derived predictions and empirical MEG data. The postevent suppressive mechanism explains an array of studies that associate beta with decreased processing, whereas the during-event facilitatory mechanism may demand a reinterpretation of the role of beta events in the context of coincident timing.
Evaluation of Chiral Liquid Chromatographic Method for Separation and Quantification of Isomers of Brivaracetam
Authors: Choppari Thirupathi , Gunnam Srinivasu , Chennuru Lakshmi Narayana , Cherla Parameswara Murthy , Talluri M V N Kumar 
Published: June 2021

Abstract
A selective, sensitive and robust chiral analytical method was developed for the quantification of Brivaracetam (BRV) and its three isomers. Systematic chiral chromatographic elution process was executed in different modes on chiral columns of polysaccharide based to attain the finest condition. The analytical method was developed by utilizing immobilized polysaccharide chiral column (CHIRALPAK IG-U) with reversed phase under isocratic condition containing acetonitrile and 10 mM ammonium bicarbonate in the proportion of 40:60 (v/v). The mobile phase flow rate and column temperature were monitored at 0.3 mLmin−1 and 25°C with a resolution of more than 2.0. The eluted components from the column were processed at 212 nm UV detection. The limit of detection and limit of quantification values of BRV, 2R, 4S-Isomer, 2R, 4R-Isomer and 2S, 4S-Isomers were found to be 0.0066/0.02, 0.0035/0.0107, 0.0036/0.0109 and 0.005/0.0152 µgml−1 respectively. Precision, linearity, accuracy and robustness were conducted according to ICH guidelines and the findings were within the acceptable limits. The proposed analytical method was found to be precise, accurate and specific for the quantification of enantiomer and its diastereomers for drug product and drug substance of BRV.