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Improving efficiency and robustness of enhanced assumed strain elements for nonlinear problems

Pfefferkorn, Robin; Bieber, Simon; Oesterle, Bastian; Bischoff, Manfred; Betsch, Peter

The enhanced assumed strain (EAS) method is one of the most frequently used methods to avoid locking in solid and structural finite elements. One issue of EAS elements in the context of geometrically nonlinear analyses is their lack of robustness in the Newton–Raphson scheme, which is characterized by the necessity of small load increments and large number of iterations. In the present work we extend the recently proposed mixed integration point (MIP) method to EAS elements in order to overcome this drawback in numerous applications. Furthermore, the MIP method is generalized to generic material models, which makes this simple method easily applicable for a broad class of problems. In the numerical simulations in this work, we compare standard strain‐based EAS elements and their MIP improved versions to elements based on the assumed stress method in order to explain when and why the MIP method allows to improve robustness. A further novelty in the present work is an inverse stress‐strain relation for a Neo‐Hookean material model.

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Verlagsausgabe §
DOI: 10.5445/IR/1000129864
Veröffentlicht am 05.03.2021
Cover der Publikation
Zugehörige Institution(en) am KIT Institut für Mechanik (IFM)
Publikationstyp Zeitschriftenaufsatz
Publikationsjahr 2020
Sprache Englisch
Identifikator ISSN: 0029-5981, 1097-0207
KITopen-ID: 1000129864
Erschienen in International journal for numerical methods in engineering
Verlag Wiley
Schlagwörter enhanced assumed strain; inverse stress–strain relation; mixed finite elements; mixed integration point method; Newton–Raphson scheme; robustness
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