Does Mode 1 Fatigue Test Alone Warrant Reliability?

摘要

For structure that is required long-term reliability, the fatigue is the key property of the materials. Therefore, webelieved that the fatigue properties of the structural materials for the reactor had been fully inspected. Most of fatiguedata were evaluated by the rotary bending test or the axial cyclic loading test. In the both test methods, normal stressamplitude is predominately affected on the fatigue behavior and the resultant cracks propagate in the open mode, Mode 1.In other words, the Mode 1 fatigue properties of the reactor structural materials were only warranted. Does Mode 1fatigue test alone warrant the reliability?In this report the S-N curves and the fatigue crack propagation behavior of 316 stainless steel, a low carbon steel(JIS SS400) and 2195T3 A1-Li alloy in all modes loading excluding Mode 1 were investigated. Two types of fatiguetest method have been used, i.e., the bar torsion test and a cracked ring compression test. To limit the maximum shearlocation to the observation window, an eccentric torsion fatigue test specimen had been developed. Cracked ringspecimen is a various uses fracture mechanics specimen developed by one of the authors. This specimen does also preferfor Mode 1 and mixed mode fatigue crack propagation test. To investigate the 3 dimensions torsion crack behavior, a 3Dwire frame model computer program was developed.