Characteristics of three-dimensional stress fields in cracked plates under general loadings

Three-dimensional finite element analyses were performed on plates with a through-the-thickness crack. The global-local finite element technique with sub-modeling was used to achieve the refinement required to obtain an accurate stress field. A model was proposed to explain the behavior of stresses in the boundary layer. This model is able to account for the competing interaction between the inverse square root singular term and vertex singular term. The strain energy release rate was calculated using the modified crack closure method and energy balance. A simple technique without 3-D calculation was suggested for evaluating an approximate 3-D stress intensity factor at the mid-plane.;Three-dimensional stress fields for the orthotropic cracked plate were investigated. The stress intensity profiles along the thickness direction were obtained using both the stress method and the modified crack closure method. The equation for the relation between three-dimensional stress intensity factor and its two-dimensional counterpart was derived for orthotropic materials.;The cracked plates subjected to out-of-plane tearing loads were investigated. Three-dimensional finite element analyses were performed and compared to results from analyses with shell elements based on Reissner's plate theory. New relations between the strain energy release rate and the stress intensity factor were derived from 3-D results. Also, out-of-plane tearing tests were conducted and some experimental observation on the 3-D crack front was carried out.