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Title: Springback Simulation of High Strength Steel Sheet using Local Interpolation for Tool Surfaces

Abstract

This paper presents the effect of tool modelling accuracy on the simulation accuracy of springback in high strength steels. Simulations of a two-dimensional draw-bending process are carried out by using a polyhedral tool model whose surface is approximated by a polyhedron, and a model whose surface is smoothed by quadratic parametric surfaces proposed by Nagata [Nagata, Comput. Aided Geom. D, 22(2005), 55-59] (Nagata patch model). It is found that not only the shape accuracy but also the normal vector accuracy of tool models are of importance for accurate springback predictions. The use of the Nagata patch model is an efficient approach not only to improve the simulation accuracy but also to make the simulation be hardly influenced by the tool mesh, even for simulations of a high strength steel in which large amount of springback is involved.

Authors:
; ;  [1];  [2];  [3];  [2]
  1. Department of Energy Science and Technology, Kyoto University, Yoshida-Honmachi, Sakyo-ku, Kyoto 606-8501 (Japan)
  2. Volume-CAD System Research Program, The Institute of Physical and Chemical Research, 2-1 Hirosawa, Wako-shi, Saitama 351-0198 (Japan)
  3. (France)
Publication Date:
OSTI Identifier:
21061760
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: 10.1063/1.2740909; (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; ACCURACY; BENDING; COMPUTERIZED SIMULATION; INTERPOLATION; MATHEMATICAL MODELS; SHAPE; SHEETS; STEELS; SURFACES; TOOLS; ULTIMATE STRENGTH

Citation Formats

Hama, Takayuki, Fujimoto, Hitoshi, Takuda, Hirohiko, Teodosiu, Cristian, LPMTM-CNRS, University Paris 13, 93430 Villetaneuse, and Makinouchi, Akitake. Springback Simulation of High Strength Steel Sheet using Local Interpolation for Tool Surfaces. United States: N. p., 2007. Web. doi:10.1063/1.2740909.
Hama, Takayuki, Fujimoto, Hitoshi, Takuda, Hirohiko, Teodosiu, Cristian, LPMTM-CNRS, University Paris 13, 93430 Villetaneuse, & Makinouchi, Akitake. Springback Simulation of High Strength Steel Sheet using Local Interpolation for Tool Surfaces. United States. doi:10.1063/1.2740909.
Hama, Takayuki, Fujimoto, Hitoshi, Takuda, Hirohiko, Teodosiu, Cristian, LPMTM-CNRS, University Paris 13, 93430 Villetaneuse, and Makinouchi, Akitake. Thu . "Springback Simulation of High Strength Steel Sheet using Local Interpolation for Tool Surfaces". United States. doi:10.1063/1.2740909.
@article{osti_21061760,
title = {Springback Simulation of High Strength Steel Sheet using Local Interpolation for Tool Surfaces},
author = {Hama, Takayuki and Fujimoto, Hitoshi and Takuda, Hirohiko and Teodosiu, Cristian and LPMTM-CNRS, University Paris 13, 93430 Villetaneuse and Makinouchi, Akitake},
abstractNote = {This paper presents the effect of tool modelling accuracy on the simulation accuracy of springback in high strength steels. Simulations of a two-dimensional draw-bending process are carried out by using a polyhedral tool model whose surface is approximated by a polyhedron, and a model whose surface is smoothed by quadratic parametric surfaces proposed by Nagata [Nagata, Comput. Aided Geom. D, 22(2005), 55-59] (Nagata patch model). It is found that not only the shape accuracy but also the normal vector accuracy of tool models are of importance for accurate springback predictions. The use of the Nagata patch model is an efficient approach not only to improve the simulation accuracy but also to make the simulation be hardly influenced by the tool mesh, even for simulations of a high strength steel in which large amount of springback is involved.},
doi = {10.1063/1.2740909},
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}
}
  • 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
  • In this paper the application of a crystal plasticity model for body-centered cubic crystals in the simulation of a sheet metal forming process is discussed. The material model parameters are identified by a combination of a texture approximation procedure and a conventional parameter identification scheme. In the application of a cup drawing process the model shows an improvement of the strain and earing prediction as well as the qualitative springback results in comparison with a conventional phenomenological model.
  • Prediction of formability for sheet metal pressings has advanced to a high state of confidence in recent years. The major challenge is now to predict springback and, moreover, to assist in the design of tooling to correctly compensate for springback. This is particularly the case for materials now being routinely considered for automotive production, such as aluminium and ultra high strength steels, which are prone to greater degrees of springback than traditional mild steels. This paper presents a case study based on the tool design for an ultra high strength steel side impact beam. The forming and springback simulations, carriedmore » out using eta/DYNAFORM (based on the LS-DYNA solver), are reported and compared to measurements from the prototype panels. The analysis parameters used in the simulation are presented, and the sensitivity of the results to variation in physical properties is also reviewed. The process of compensating the tools based on the analysis prediction is described; finally, an automated springback compensation method is also applied and the results compared with the final tool design.« less
  • The automotive industry has been pressed to satisfy more rigorous fuel efficiency requirements to promote energy conservation, safety features and cost containment. To satisfy this need, high strength steel has been developed and used for many different vehicle parts. The use of high strength steels, however, requires careful analysis and creativity in order to accommodate its relatively high springback behavior. An innovative method, called local warm forming with near infrared ray, has been developed to help promote the use of high strength steels in sheet metal forming. For this method, local regions of the work piece are heated using infraredmore » ray energy, thereby promoting the reduction of springback behavior. In this research, a V-bend test is conducted with DP980. After springback, the bend angles for specimens without local heating are compared to those with local heating. Numerical analysis has been performed using the commercial program, DEFORM-2D. This analysis is carried out with the purpose of understanding how changes to the local stress distribution will affect the springback during the unloading process. The results between experimental and computational approaches are evaluated to assure the accuracy of the simulation. Subsequent numerical simulation studies are performed to explore best practices with respect to thermal boundary conditions, timing, and applicability to the production environment.« less