Penentuan Kehilangan Kekangan dalam Medan Tiga-dimensi Hujung-retak Tiada-pengerasan

Abstract

Analysis of crack tip stress field is important in determining of the integrity of structures under the influence of cracks and defects. Current techniques to analyze crack tip stress fields are based on two-dimensional approach and very conservative. Efforts to develop three-dimensional crack tip stress analysis methods have been inconclusive with various drawbacks. In this paper, the structure of three-dimensional crack tip fields has been examined under non-hardening condition which will allow a detail examination of crack tip stresses in the absence of strain hardening effects. Three-dimensional crack tip analysis is based on three-dimensional bend and tension cracked models. The fields along the crack front were examined as a function of load level, J, and thickness, x3/t. The results showed that at the crack tip (r = 0), a group of asymptotic fields develop which feature a constant stress sector directly ahead of the crack tip. Within this sector the fields differ hydrostatically while being similar in respect of the maximum stress deviator. From the behavior of the crack tip stresses, explicit expression of crack tip constraints are given for constraint loss in terms of maximum stresses due to out-of plane effects at θ=0° and along the crack front 0  x3/t  0.5. Significantly, the results showed that constraint based fracture mechanics can be extended to fully three dimensional crack tip fields.