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Title: Towards Efficient Modelling Of Macro And Micro Tool Deformations In Sheet Metal Forming

Abstract

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 in 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,more » 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

Authors:
 [1];  [2];  [3]
  1. Netherlands Institute for Metals Research, Mekelweg 2 P.O. Box 5008 2600GA Delft (Netherlands)
  2. (Germany)
  3. University of Twente, Postbus 217 7500 AE Enschede (Netherlands)
Publication Date:
OSTI Identifier:
21061748
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: 10.1063/1.2740896; (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; ALGORITHMS; ALLOYS; APPROXIMATIONS; COMPUTERIZED SIMULATION; DEFORMATION; DRAWING; ELASTICITY; FINITE ELEMENT METHOD; FLEXIBILITY; METALS; PLATES; PRESSING; SHEETS

Citation Formats

Lingbeek, R. A., INPRO Innovationsgesellschaft fuer fortgeschrittene Produktionssysteme in der Fahrzeugindustrie mbH Hallerstrasse 1, D-10587 Berlin, and Meinders, T. Towards Efficient Modelling Of Macro And Micro Tool Deformations In Sheet Metal Forming. United States: N. p., 2007. Web. doi:10.1063/1.2740896.
Lingbeek, R. A., INPRO Innovationsgesellschaft fuer fortgeschrittene Produktionssysteme in der Fahrzeugindustrie mbH Hallerstrasse 1, D-10587 Berlin, & Meinders, T. Towards Efficient Modelling Of Macro And Micro Tool Deformations In Sheet Metal Forming. United States. doi:10.1063/1.2740896.
Lingbeek, R. A., INPRO Innovationsgesellschaft fuer fortgeschrittene Produktionssysteme in der Fahrzeugindustrie mbH Hallerstrasse 1, D-10587 Berlin, and Meinders, T. Thu . "Towards Efficient Modelling Of Macro And Micro Tool Deformations In Sheet Metal Forming". United States. doi:10.1063/1.2740896.
@article{osti_21061748,
title = {Towards Efficient Modelling Of Macro And Micro Tool Deformations In Sheet Metal Forming},
author = {Lingbeek, R. A. and INPRO Innovationsgesellschaft fuer fortgeschrittene Produktionssysteme in der Fahrzeugindustrie mbH Hallerstrasse 1, D-10587 Berlin and Meinders, T.},
abstractNote = {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 in 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.},
doi = {10.1063/1.2740896},
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
  • 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.
  • Treatment of contact between a sheet and tools is one of the most difficult problems to deal with in finite-element simulations of sheet forming processes. In order to obtain more accurate tool models without increasing the number of elements, this paper describes a new formulation for contact problems using interpolation proposed by Nagata for tool surfaces. A contact search algorithm between sheet nodes and the interpolated tool surfaces was developed and was introduced into the static-explicit elastoplastic finite-element method code STAMP3D. Simulations of a square cup deep drawing process with a very coarsely discretized punch model were carried out. Themore » simulated results showed that the proposed algorithm gave the proper drawn shape, demonstrating the validity of the proposed algorithm.« less
  • Springback is an unquenchable forming defect in the sheet metal forming process. How to calculate springback accurately is a big challenge for a lot of FEA software. Springback compensation makes the stamped final part accordant with the designed part shape by modifying tool surface, which depends on the accurate springback amount. How ever, the meshing data based on numerical simulation is expressed by nodes and elements, such data can not be supplied directly to tool surface CAD data. In this paper, a tool surface compensation algorithm based on numerical simulation technique of springback process is proposed in which the independentlymore » developed dynamic explicit springback algorithm (DESA) is used to simulate springback amount. When doing the tool surface compensation, the springback amount of the projected point can be obtained by interpolation of the springback amount of the projected element nodes. So the modified values of tool surface can be calculated reversely. After repeating the springback and compensation calculations for 1{approx}3 times, the reasonable tool surface mesh is gained. Finally, the FEM data on the compensated tool surface is fitted into the surface by CAD modeling software. The examination of a real industrial part shows the validity of the present method.« less
  • Titanium and its alloys are difficult to form at room temperature due to their high flow stress. Super plastic deformation of Ti alloys involves low strain rate forming at very high temperatures which need special tooling which can withstand high temperatures. It was observed that when high current density electric pulse is applied during deformation it reduces the flow stress through electron-dislocation interaction. This phenomenon is known as electro-plasticity. In the present work, importance of tool configuration to enhance the formability without much resistive heating is demonstrated for Incremental Sheet Metal Forming (ISMF). Tool configuration is selected to minimize themore » current carrying zone in DC pulse aided incremental forming to enhance the formability due to electro plasticity and the same is demonstrated by forming two pyramid shaped components of 30° and 45° wall angles using a Titanium alloy sheet of 0.6 mm thickness. Load measurement indicated that a critical current density is essential for the electro-plasticity to be effective and the same is realized with the load and temperature measurements.« less