Application of a Kerf to Extend Fatigue Cycle of a Plate under Three-Points Bending Loading

摘要

There are few methods available to arrest crack propagation or fatigue life of a structure. One of the crack arresting methods is by using kerf fabrication parallel to the edge crack. Recent study has proved that the introduction of the kerf parallel to an edge crack for a case of tension loading has reduced the stress intensity factor of the crack tip and thus will be able to arrest crack propagation or as long as the applied load is not significantly increased. However the study of kerf for the case of bending loading is still not available. Therefore this study aims to extend the study of kerf fabrication for a case of bending loading to conclude whether the kerf also can be applied as a crack arrestor for a structure under bending loading. This research focuses on total fatigue life cycle of a specimen that contains an edge crack and an edge kerf under fatigue three-point bending loading. The total fatigue cycles to failure using fatigue test for various specimens with different crack and kerf geometries were observed and compared with specimen without any kerf fabrication. Result shows the fatigue cycles can be further extended with maximum 39% extension. This can be achieved when kerf length to crack length ratio, k/a = 0.8 and distance to width ratio, d/w = 0.25. It can be concluded that the highest fatigue cycles' extension can be achieved when the kerf and distance between kerf and crack are the longest.