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

Title: Integrated Modelling of Damage and Fracture in Sheet Metal Forming

Abstract

A framework for finite element simulations of ductile damage development and ductile fracture during metal forming is presented. The damage evolution is described by a phenomenological continuum damage model. Crack growth and fracture are treated as the ultimate consequences of the damage process. Computationally, the initiation and growth of cracks is traced by an adaptive remeshing strategy, thereby allowing for opening crack faces. The application of the method to the fabrication of food-can lids demonstrates its capabilities, but also some of its limitations.

Authors:
;  [1];  [1];  [2]
  1. Department of Mechanical Engineering, Eindhoven University of Technology, Eindhoven (Netherlands)
  2. (Netherlands)
Publication Date:
OSTI Identifier:
21061750
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: 10.1063/1.2740898; (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; COMPUTERIZED SIMULATION; CRACK PROPAGATION; CRACKS; DAMAGE; DUCTILITY; FABRICATION; FINITE ELEMENT METHOD; FRACTURES; METALS; SHEETS

Citation Formats

Peerlings, R. H. J., Geers, M. G. D., Mediavilla, J., and Netherlands Institute for Metals Research, Delft. Integrated Modelling of Damage and Fracture in Sheet Metal Forming. United States: N. p., 2007. Web. doi:10.1063/1.2740898.
Peerlings, R. H. J., Geers, M. G. D., Mediavilla, J., & Netherlands Institute for Metals Research, Delft. Integrated Modelling of Damage and Fracture in Sheet Metal Forming. United States. doi:10.1063/1.2740898.
Peerlings, R. H. J., Geers, M. G. D., Mediavilla, J., and Netherlands Institute for Metals Research, Delft. Thu . "Integrated Modelling of Damage and Fracture in Sheet Metal Forming". United States. doi:10.1063/1.2740898.
@article{osti_21061750,
title = {Integrated Modelling of Damage and Fracture in Sheet Metal Forming},
author = {Peerlings, R. H. J. and Geers, M. G. D. and Mediavilla, J. and Netherlands Institute for Metals Research, Delft},
abstractNote = {A framework for finite element simulations of ductile damage development and ductile fracture during metal forming is presented. The damage evolution is described by a phenomenological continuum damage model. Crack growth and fracture are treated as the ultimate consequences of the damage process. Computationally, the initiation and growth of cracks is traced by an adaptive remeshing strategy, thereby allowing for opening crack faces. The application of the method to the fabrication of food-can lids demonstrates its capabilities, but also some of its limitations.},
doi = {10.1063/1.2740898},
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}
}
  • Strain recovery after removal of forming loads, commonly defined as springback, is of great concern in sheet metal forming, in particular with regard to proper prediction of the final shape of the part. To control the problem a lot of work has been done, either by minimizing the springback on the material side or by increasing the estimation precision in corresponding process simulations. Unfortunately, by currently available software springback still cannot be adequately predicted, because most analyses of springback are using linear, isotropic and constant Young's modulus and Poisson's ratio. But, as it was measured and reported, none of itmore » is true. The aim of this work is to propose an upgraded mechanical model which takes evolution of damage and related orthotropic stiffness degradation into account. Damage is considered by inclusion of ellipsoidal cavities, and their influence on the stiffness degradation is taken in accordance with the Mori-Tanaka theory, adopting the GTN model for plastic flow. With regard to the case in which damage in material is neglected it is shown in the article how the springback of a formed part differs, when we take orthotropic damage evolution into consideration.« less
  • During forming, the deep drawing press and tools undergo large loads, and even though they are extremely sturdy structures, deformations occur. This causes changes in the geometry of the tool surface and the gap width between the tools. The deep drawing process can be very sensitive to these deformations. Tool and press deformations can be split into two categories. The deflection of the press bed-plate or slide and global deformation in the deep drawing tools are referred to as macro press deformation. Micro-deformation occurs directly at the surfaces of the forming tools and is one or two orders lower inmore » magnitude.The goal is to include tool deformation in a FE forming simulation. This is not principally problematic, however, the FE meshes become very large, causing an extremely large increase in numerical effort. In this paper, various methods are discussed to include tool elasticity phenomena with acceptable cost. For macro deformation, modal methods or 'deformable rigid bodies' provide interesting possibilities. Static condensation is also a well known method to reduce the number of DOFs, however the increasing bandwidth of the stiffness matrix limits this method severely, and decreased calculation times are not expected. At the moment, modeling Micro-deformation remains unfeasible. Theoretically, it can be taken into account, but the results may not be reliable due to the limited size of the tool meshes and due to approximations in the contact algorithms.« less
  • 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
  • It is well established that ductile fracture occurs by nucleation, growth and coalescence of voids generally associated with particles. However, volume damage is present in the material at the first stage of the plastic deformation and, therefore, has an influence on the plastic behavior of the material. Metallographical observations and relative density change measurements show that there exist two main damage mechanisms: either decohesion at the particle-matrix interface or failure of the particles. In both cases, an analysis of the evolution of damage is performed and a model is proposed. A general law of void growth according to the strainmore » and strain path is then established for both damage mechanisms.« less
  • Sheet cold drawing is limited by the appearance of localized necking. An influential parameter is volume damage associated with second phase particles. The framework of the calculation hypothesis being defined (rheology of the material, forming limit definition, damage parameters, plasticity theories) the forming limit of a material can be calculated through a two-slice sample assuming that: internal defects are equivalent to thickness defects. It is then possible to account for the forming limit diagrams, and for the influence of the damage mechanism and of the initial thickness of the sheet.