No abstract

The stop-hole method is investigated previously with creating a non-circular hole. That hole defines as an optimum stop hole shape that gives maximum initial fatigue life. Optimum stop hole shape decreases stress concentration without increasing the nominal stress, by using optimization technique. The effect of this optimum hole shape on crack reinitiating life for different model geometries is studied. The aim of this work is to introduce a software program to make it easy for everybody to determine optimum shape of stop hole suitable for user's geometry. This program is called OHS (Optimum Hole Shape). The input of that program will be only the specimen width, length, and crack length in addition to applied load. Then OHS outputs global optimum hole shape parameters. The optimum hole shape for different models are saved as database for OHS program. OHS can be linked directly with EDM machines to create optimum hole with one click.

Optimal shape is supposed to remove the damaged material and minimize stresses. In order to validate that, two identical models are created. The first models has a non repaired crack, and the other has a repaired crack with the optimum hole shape Plastic zone size is of crucial importance in this study as it is hypothesized that the hole should be drilled to remove most of this zone. This will leave the rest of the material in virgin state and eliminate any predefined slip planes dislocation.