Boundary elements analysis of viscoelastic fracture B. Sensale, G.J. Creus CEMA COM/CfGEC/f^OMEC, Federof University of Rio Grande do Sul, 90210 Porto Alegre, RS, Brazil ABSTRACT A numerical procedure based on the Boundary Elements Method and Schapery's formulation is proposed to determine cracks critical condition in viscoelastic structures. INTRODUCTION The increasing use of polymeric materials (plain or reinforced with fibers as in composite materials) as structural elements justifies the desire for a better understanding of their mechanical behavior, including fracture properties. Polymers are usually modeled as linear viscoelastic materials (Creus [ 1 ],Schapery [2]). This approximation is usually valid for the analysis of mechanical behavior under working stresses. In stress concentration areas as notches or cracks, the behavior seems to be highly nonlinear, but not well established models exist for these situations. When linear viscoelasticity theory is applied to the analysis of the traction boundary value problem for a cracked body, the correspondence principle, (Creus [1]) indicates that stresses remain constant in time. Thus, when a K-type stress intensity criterion for crack growth is applied, no deferred effect appears to be possible. On the other hand, experiential results,(Kanninen [3]) indicate that cracks in viscoelastic materials do grow under constant loads well beneath the elastic fracture load level. The reason for this apparent paradox lies in the existence of a process zone or failure zone around the crack tip, where the material shows a highly nonlinear behavior. Several authors have studied this problem. In this paper we shall follow the approach of Schapery [2], that allows an approximate treatment without the need of a precise modeling of the nonlinear behavior Transactions on Modelling and Simulation vol 2, © 1993 WIT Press, www.witpress.com, ISSN 1743-355X
Boundary elements analysis of viscoelastic fracture
May 22, 2023
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