Mats Sigvant

Bio: Mats Sigvant is an academic researcher from Volvo Cars. The author has contributed to research in topics: Sheet metal & Necking. The author has an hindex of 10, co-authored 40 publications receiving 338 citations. Previous affiliations of Mats Sigvant include Blekinge Institute of Technology & Technical University of Cluj-Napoca.

A viscous pressure bulge test for the determination of a plastic hardening curve and equibiaxial material data

Abstract: The importance of an accurate material modeling for the accuracy and reliability of sheet forming simulations has become increasingly evident during the last years. More advanced material models have, however, to be supported by novel methods for material characterization. The recent eight parameter yield functions Yld2000-2d and BBC2003 demand, besides data from the ordinary uniaxial tensile tests, also equibiaxial data. In the present paper a Viscous Pressure Bulge (VPB) test is described. The test yields the equibiaxial stress point and r-value, as well as a plastic hardening curve for large values of plastic strain. The test setup is based on an ARGUSS™ optical measuring system, and provides the desired result data in a very smooth and easy way. In order to verify the results from the current test, comparisons have been made with compression tests performed at Corus RD&T and hydraulic bulging tests performed at RWTH in Aachen. A discussion on how to determine the equibiaxial yield stress and how to transform the biaxial stress-strain curve to an effective stress-strain curve is included in the paper.

Influence of constitutive equations on the accuracy of prediction in sheet metal forming simulation

Abstract: During the last three decades, numerical simulation has gradually extended its applicability in the field of sheet metal forming. Constitutive modelling is one of the domains closely related to the development of numerical simulation tools. The paper is focused on the development of new phenomenological yield criteria developed in the CERTETA research centre able to describe the anisotropic response of sheet metals. The numerical tests presented in the paper prove the capability of the equivalent stresses to model the inelastic response of a large variety of materials (steel and aluminium alloys). The last section of the paper is devoted to a comprehensive testing of the new yield criterion as implemented in the finite-element code AUTOFORM 4.1. With this aim in view, the authors have chosen the bulging and cross deep drawing benchmarks. The test proves the capability of the yield criterion to describe the effects of the plastic anisotropy of the sheet metals subjected to industrial forming processes.

Nonlinear Finite Elements For Continua And Structures

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Advances in anisotropy and formability

Abstract: This paper presents synthetically the most recent models for description of the anisotropic plastic behavior. The first section gives an overview of the classical models. Further, the discussion is focused on the anisotropic formulations developed on the basis of the theories of linear transformations and tensor representations, respectively. Those models are applied to different types of materials: body centered, faced centered and hexagonal-close packed metals. A brief review of the experimental methods used for characterizing and modeling the anisotropic plastic behavior of metallic sheets and tubes under biaxial loading is presented together with the models and methods developed for predicting and establishing the limit strains. The capabilities of some commercial programs specially designed for the computation of forming limit curves (FLC) are also analyzed.

Testing and modelling of material behaviour and formability in sheet metal forming

Abstract: The paper deals with the testing and modelling of metals response when subjected to sheet forming operations. The focus is both on the modelling of hardening behaviour and yield criteria and on the description of the sheet metal formability limits. Within this scope, the paper provides a critical review of the models available today for predicting the material behaviour at both industrial and scientific level, and the tests needed to identify the models’ material parameters. The most recent advances in the field are also presented and discussed with particular emphasis on the challenges the sheet metal forming community is now facing.