skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: A new solid-shell finite element technology incorporating plastic anisotropy in forming simulations

Abstract

In the recent years shell finite element formulations which include only displacement degrees-of-freedom, the so-called solid-shells, have been successfully applied in sheet metal forming. A very efficient strategy to deal with the problem of locking which occurs in bending-dominated problems and in the limit of incompressibility is the method of reduced integration with hourglass stabilization. Further advantages of these finite element technologies are their robustness with respect to severe mesh distortion and the low computational cost. A disadvantage is, however, the necessity to develop a suitable hourglass stabilization which adapts to both, the changing geometry and the usually highly non-linear material behaviour. Most earlier finite element technologies are based on the assumption that the material behaviour is initially isotropic. In the present contribution we develop an approach to include initial and deformation-induced anisotropy. Prerequisite for that is the development of a suitable material law. In contrast to many other current papers we aim at a purely continuum mechanical modelling to arrive at optimal numerical efficiency.

Authors:
; ;  [1]
  1. Institute of Solid Mechanics, Braunschweig University of Technology, Schleinitzstr. 20, D-38106 Braunschweig (Germany)
Publication Date:
OSTI Identifier:
21061753
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 908; Journal Issue: 1; Conference: NUMIFORM 2007: 9. international conference on numerical methods in industrial forming processes, Porto (Portugal), 17-21 Jun 2007; Other Information: DOI: 10.1063/1.2740901; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; ALLOYS; ANISOTROPY; BENDING; COMPUTERIZED SIMULATION; DEGREES OF FREEDOM; FINITE ELEMENT METHOD; MATERIALS WORKING; METALS; NONLINEAR PROBLEMS; PLASTICITY; SHEETS; SOLIDS; STABILIZATION

Citation Formats

Reese, Stefanie, Vladimirov, Ivaylo N., and Schwarze, Marco. A new solid-shell finite element technology incorporating plastic anisotropy in forming simulations. United States: N. p., 2007. Web. doi:10.1063/1.2740901.
Reese, Stefanie, Vladimirov, Ivaylo N., & Schwarze, Marco. A new solid-shell finite element technology incorporating plastic anisotropy in forming simulations. United States. doi:10.1063/1.2740901.
Reese, Stefanie, Vladimirov, Ivaylo N., and Schwarze, Marco. Thu . "A new solid-shell finite element technology incorporating plastic anisotropy in forming simulations". United States. doi:10.1063/1.2740901.
@article{osti_21061753,
title = {A new solid-shell finite element technology incorporating plastic anisotropy in forming simulations},
author = {Reese, Stefanie and Vladimirov, Ivaylo N. and Schwarze, Marco},
abstractNote = {In the recent years shell finite element formulations which include only displacement degrees-of-freedom, the so-called solid-shells, have been successfully applied in sheet metal forming. A very efficient strategy to deal with the problem of locking which occurs in bending-dominated problems and in the limit of incompressibility is the method of reduced integration with hourglass stabilization. Further advantages of these finite element technologies are their robustness with respect to severe mesh distortion and the low computational cost. A disadvantage is, however, the necessity to develop a suitable hourglass stabilization which adapts to both, the changing geometry and the usually highly non-linear material behaviour. Most earlier finite element technologies are based on the assumption that the material behaviour is initially isotropic. In the present contribution we develop an approach to include initial and deformation-induced anisotropy. Prerequisite for that is the development of a suitable material law. In contrast to many other current papers we aim at a purely continuum mechanical modelling to arrive at optimal numerical efficiency.},
doi = {10.1063/1.2740901},
journal = {AIP Conference Proceedings},
number = 1,
volume = 908,
place = {United States},
year = {Thu May 17 00:00:00 EDT 2007},
month = {Thu May 17 00:00:00 EDT 2007}
}
  • Finite element simulations of sheet metal forming processes are highly non-linear problems. The non-linearity arises not only from the kinematical relations and the material formulation, furthermore the contact between workpiece and the forming tools leads to an increased number of iterations within the Newton-Raphson scheme. This fact puts high demands on the robustness of finite element formulations. For this reason we study the enhanced assumed strain (EAS) concept as proposed in [1]. The goal is to improve the robustness of the solid-shell formulation in deep drawing simulations.
  • In this communication sheet metal forming problems are analyzed with the Finite Element Method and a fully-integrated solid-shell element, based on the Enhanced Assumed Strain (EAS) method. Among the solid-shell element's distinguish features, it should be mentioned the solely use of the EAS approach in dealing with either transverse and volumetric-based locking pathologies, thus avoiding the inclusion of other mixed methods into the formulation. The adopted methodology is then able to successfully deal with small thickness shell problems within the incompressible range, aspects commonly appearing in sheet metal forming modeling with solid elements.Simulations of this type of forming processes aremore » mainly solved resorting to membrane and shell-type finite elements, included in explicit commercial programs. Nevertheless, the presented solid-shell formulation, within a fully implicit approach, provides reliable solutions when compared to experimental results. It is also worth mentioning that the present solid-shell formulation encompasses a minimum set of enhancing strain variables, if compared to other fully integrated hexahedral finite elements in the literature.In order to assess the performance of the presented formulation, the S-Rail Forming problem of an aluminum alloy is described and analyzed, with the results being compared to experimental and numerical simulation data.« less
  • In this work, an implicit, backward Euler time integration scheme is developed for an anisotropic, elastic-plastic model based on strain-rate potentials. The constitutive algorithm includes a sub-stepping procedure to deal with the strong nonlinearity of the plastic potentials when applied to FCC materials. The algorithm is implemented in the static implicit version of the Abaqus finite element code. Several recent plastic potentials have been implemented in this framework. The most accurate potentials require the identification of about twenty material parameters. Both mechanical tests and micromechanical simulations have been used for their identification, for a number of BCC and FCC materials.more » The impact of the identification procedure on the prediction of ears in cup drawing is investigated.« less
  • The molar volume difference between the matrix and the precipitate phases in the case of solid state phase transformations results in the creation of stain energy in the system due to the misfit strains. A finite element model based on the initial strain approach is proposed to evaluate elasto-plastic accommodation energies during solid state transformation. The three-dimensional axisymmetric model has been used to evaluate energies as a function of transformation for {alpha}-{beta} hydrogen transformations in the Nb-H system. The transformation has been analyzed for the cases of transformation progressing both from the center to surface and from the surface tomore » center of the system. The effect of plastic deformation has been introduced to make the model realistic, specifically to the Nb-NbH phase transformation which involves a 4% linear misfit strain. It has been observed that plastic deformation reduces the strain energies compared to the linear elastic analysis.« less
  • A copper sample made of a single layer of grains is plastically deformed by uniaxial tension at room temperature and low strain rate. The deformation field is measured by means of grids deposited on the polished surface of the undeformed specimen and local orientations are recorded using electron back scattering diagrams in a scanning electron microscope. These measures are compared with simulations made by a finite element code using a physically based model for the deformation and hardening of face centered cubic crystals. A good agreement is found between measured and computed values. The simulations give access to much moremore » detail about the history of glide in each grain and help establish which systems are active at a local level. They also provide the evolution of internal variables such as dislocation densities. A new insight into intergranular accommodation as well as intragranular heterogeneities is provided.« less