New crack stop hole shape using structural optimizing technique

In the present study, the stop-hole method was investigated with creating a noncircular hole. The aim of the present work was to obtain an optimum stop hole shape that gives maximum fatigue crack initiation life by using finite element program. It was found that the fatigue life obtained by using the optimum hole shape ranges from 2 to 9 times the fatigue life obtained by using the circular holes. It was found that the optimum hole shape increased the initial fatigue life for all specimens used. Opposite to the traditional stress concentration factor minimization problem where the nominal area remains constant during optimization, here it is allowed to vary nominal area using design variables resulting in decreasing of the nominal stress in addition to decreasing of the stress concentration factor. This leads to higher fatigue life compared to previous studies.