Proportional extrapolation techniques for determining stress intensity factors

Abstract Proportional extrapolation techniques were proposed to compute simply and accurately stress intensity factors using the numerical computation method. They are based on procedures in which the effects of element division near the crack tip on stresses and displacements are corrected by comparison with a standard problem. Corrected results are only accurate in the limit as r → 0 ( r = distance from crack tip). A few crack problems were analysed by the boundary element method, and the proportional extrapolation techniques were applied to determine the crack tip stress intensity factors. A special strain gauge pattern was developed for applying the proportional extrapolation technique. The stress intensity factors of two-dimensional crack problems were analysed experimentally using the strain gauge.