Some tests to assess the effect of crack stoppers on the fatigue life of centre-notched sheetspecimens

Several simple crack stopping methods were evaluated In fatigue crack propagation tests on 2024-T3 Alclad sheet specimens. After precracklng until a crack of 40 mm was obtained crack stoppers were Installed and the fatigue test was continued. Crack stoppers Installed In stop holes were: a blind rivet, a hard driven rivet, a heavily tightened bolt, some types of self tapping screws and tapered pins. Results obtained were explained in terms of stress field around stopholes and crack bridging. Most tests were carried out under constantamplitude loadings in some tests flight-simulation loading (TWIST) was used.