الفهرس 
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Abstract
This work presents the stop-hole method with creating a non circular hole. Optimum hole shape is obtained by using ANSYS optimization toolbox. Forty six groups of optimization programs are created to validate the implementation of optimum hole for different specimen geometries. 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 crack initiation life by using finite element program without decreasing nominal area of specimen. Define global optimum hole shape for all specimen geometries .By observing the results 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. Optimum hole shape is suitable to be applied for all specimens geometries.