Stress Intensity Factors for Surface Cracks in Functionally Graded Materials under Mode I Thermomechanical Loading

M.C. Walters, Glaucio H. Paulino and R. H. Dodds, Jr

Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Newmark Laboraory, 205 North Mathews Avenue, IL 61801, U.S.A.

Abstract

This paper describes the development and application of a general domain integral method to obtain J-values along crack fronts in three-dimensional configurations of isotropic, functionally graded materials (FGMs). The present work considers mode-I, linear-elastic response of cracked specimens subjected to thermomechanical loading, although the domain integral formulation accommodates elastic–plastic behavior in FGMs. Finite element solutions and domain integral J-values for a two-dimensional edge crack show good agreement with available analytical solutions for both tension loading and temperature gradients. A displacement correlation technique provides pointwise stress-intensity values along semi-elliptical surface cracks in FGMs for comparison with values derived from the proposed domain integral. Numerical implementation and mesh refinement issues to maintain path independent J-values are explored. The paper concludes with a parametric study that provides a set of stress-intensity factors for semi-elliptical surface cracks covering a practical range of crack sizes, aspect ratios and material property gradations under tension, bending and spatially-varying temperature loads.

Key words:  Domain integral; Functionally graded material; J-integral; Mode-I stress-intensity factor; Semi-elliptical surface crack; Three dimensions

Back to Publication List