3-DIMENSIONAL EVALUATION OF THE T-STRESS IN-CENTER CRACKED PLATES

Thick three-dimensional (3-D) finite element models of centre cracked plates are used to study the variation in the biaxiality factor beta w ith the crack aspect ratio a/w. The use of two widely accepted methods to evaluate the T-stress in two-dimensions, namely the boundary layer method and the displacement field method, to calculate the T-stress i n three-dimensions is studied. It is shown that the boundary layer met hod gives results that compare rather well with the two-dimensional pl ane strain values (maximum difference of 6 percent), while the displac ement field method results are about 15 percent lower. Two parameters are shown to affect the three-dimensional evaluation of the biaxiality factor, namely the material's Poisson's ratio nu and the specimen's t hickness t. The biaxiality factor is directly proportional to nu and i nversely proportional to t. Three-dimensional analysis is required to assess correctly the effect of nu and t on beta.