Finite Deformation Elasto-Plasticity for Simulation of Strength Difference in Adhesive Materials with an Algorithm in Principal Directions

Author: Mahnken Rolf  

Publisher: Taylor & Francis Ltd

ISSN: 1537-6494

Source: Mechanics of Advanced Materials and Structures, Vol.15, Iss.6-7, 2008-08, pp. : 514-527

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Abstract

In view of growing interest in structural adhesives in industry, reliable and efficient numerical design methods are necessary for engineering assessment of the bonding parts. The experimental investigation of certain adhesive materials reveals effects of plasticity and additionally a pronounced strength difference between tension, torsion or combined loading. For simulation of these phenomena a yield function dependent on the first and second basic invariants of the related stress tensor is introduced. A mixed-variant formulation is used for the flow rule within a non-associated concept, which allows for a convenient transformation between different configurations. Thermodynamic consistency of the model equations is satisfied subject to some restrictions on the material parameters. The mixed-variant flow-rule is integrated by an exponential integration scheme, thus leading to a formulation in principal directions and allowing an algorithm developed previously for the geometrical linear case. In the numerical examples, firstly, we compare simulated and experimental results exhibiting the yield strength difference between tension and torsion for the adhesive material Betamate 1496. A second example investigates the deformation evolution of a compact tension specimen with an adhesive zone.