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CivilComp Proceedings
ISSN 17593433 CCP: 93
PROCEEDINGS OF THE TENTH INTERNATIONAL CONFERENCE ON COMPUTATIONAL STRUCTURES TECHNOLOGY Edited by: B.H.V. Topping, J.M. Adam, F.J. Pallarés, R. Bru and M.L. Romero
Paper 365
Software Supported Implementation of Efficient SolidShell Finite Elements S. Mattern and K. Schweizerhof
Institute of Mechanics, Karlsruhe Institute of Technology, Germany S. Mattern, K. Schweizerhof, "Software Supported Implementation of Efficient SolidShell Finite Elements", in B.H.V. Topping, J.M. Adam, F.J. Pallarés, R. Bru, M.L. Romero, (Editors), "Proceedings of the Tenth International Conference on Computational Structures Technology", CivilComp Press, Stirlingshire, UK, Paper 365, 2010. doi:10.4203/ccp.93.365
Keywords: solidshell elements, explicit time integration, efficient implementation, symbolic programming.
Summary
For the implementation of element routines designed for explicit time integration algorithms
efficient programming regarding the number of operations performed on the element level is of particular
importance. The limitation of the time step size and the absence of global equation solving compared
to implicit algorithms leads to a domination of element operations for example in a central difference scheme.
The paper presents an implementation concept for element routines based on the application of the symbolic programming tool AceGen [1], a plugin for the computer algebra software Mathematica. The operations necessary for the computation of the internal nodal force vector, which is the most timeconsuming part of an explicit analysis, are implemented symbolically. This means that vector and matrix operations and differentiations do not have to be computed in advance in order to realize a conversion into a programming language. Consequently, programming errors can be avoided almost completely and less time is required for the implementation. Program code in Fortran is generated and simultaneously optimized automatically, which leads to very efficient routines compared to a manually implemented code. The implementation concept is presented for volumetric shell elements with only displacement degrees of freedom, the socalled solidshell elements [2,3], using linear/quadratic interpolation of geometry and displacements in the inplane direction together with a linear interpolation in thickness direction. Besides the pure displacement formulation with standard (full) numerical integration, the implementation of different approaches in order to reduce the socalled locking phenomena are discussed: the method of assumed natural strains (ANS) [4], and the enhanced assumed strain (EAS) method [5]. Both ANS and EAS, as well as a 'Mortar'type contact formulation with analytical description of the contact surface are implemented into the inhouse finite element code FEAPMeKa [6] using AceGen. The specifics of the implementation concept are discussed and the efficiency and functionality of the element formulations are presented on numerical examples. References
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