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Title: Finite Element Technology In Forming Simulations - Theoretical Aspects And Practical Applications Of A New Solid-Shell Element

Abstract

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.

Authors:
;  [1]
  1. Institute of Solid Mechanics, Braunschweig University of Technology (Germany)
Publication Date:
OSTI Identifier:
21057376
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 908; Journal Issue: 1; Conference: NUMIFORM '07: 9. international conference on numerical methods in industrial forming processes, Porto (Portugal), 17-21 Jun 2007; Other Information: DOI: 10.1063/1.2741023; (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; DRAWING; FINITE ELEMENT METHOD; NONLINEAR PROBLEMS; SHEETS; SOLIDS; STRAINS

Citation Formats

Schwarze, M., and Reese, S. Finite Element Technology In Forming Simulations - Theoretical Aspects And Practical Applications Of A New Solid-Shell Element. United States: N. p., 2007. Web. doi:10.1063/1.2741023.
Schwarze, M., & Reese, S. Finite Element Technology In Forming Simulations - Theoretical Aspects And Practical Applications Of A New Solid-Shell Element. United States. doi:10.1063/1.2741023.
Schwarze, M., and Reese, S. Thu . "Finite Element Technology In Forming Simulations - Theoretical Aspects And Practical Applications Of A New Solid-Shell Element". United States. doi:10.1063/1.2741023.
@article{osti_21057376,
title = {Finite Element Technology In Forming Simulations - Theoretical Aspects And Practical Applications Of A New Solid-Shell Element},
author = {Schwarze, M. and Reese, S.},
abstractNote = {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.},
doi = {10.1063/1.2741023},
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}
}
  • 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-linearmore » 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.« less
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  • Purpose: To design a new compact S-band linac waveguide capable of producing a 10 MV x-ray beam, while maintaining the length (27.5 cm) of current 6 MV waveguides. This will allow higher x-ray energies to be used in our linac-MRI systems with the same footprint. Methods: Finite element software COMSOL Multiphysics was used to design an accelerator cavity matching one published in an experiment breakdown study, to ensure that our modeled cavities do not exceed the threshold electric fields published. This cavity was used as the basis for designing an accelerator waveguide, where each cavity of the full waveguide wasmore » tuned to resonate at 2.997 GHz by adjusting the cavity diameter. The RF field solution within the waveguide was calculated, and together with an electron-gun phase space generated using Opera3D/SCALA, were input into electron tracking software PARMELA to compute the electron phase space striking the x-ray target. This target phase space was then used in BEAM Monte Carlo simulations to generate percent depth doses curves for this new linac, which were then used to re-optimize the waveguide geometry. Results: The shunt impedance, Q-factor, and peak-to-mean electric field ratio were matched to those published for the breakdown study to within 0.1% error. After tuning the full waveguide, the peak surface fields are calculated to be 207 MV/m, 13% below the breakdown threshold, and a d-max depth of 2.42 cm, a D10/20 value of 1.59, compared to 2.45 cm and 1.59, respectively, for the simulated Varian 10 MV linac and brehmsstrahlung production efficiency 20% lower than a simulated Varian 10 MV linac. Conclusion: This work demonstrates the design of a functional 27.5 cm waveguide producing 10 MV photons with characteristics similar to a Varian 10 MV linac.« less