高圧縮平均応力下での疲労試験片設計

抄録

In recent years, high power output of marine diesel engine is being considered, because improving fuel consumption of a ship is required from the viewpoint of energy saving, CO₂ reduction, etc. Therefore, a crankshaft which is a main component of the engine is expected to be higher strength and fatigue strength than ever. Since bending and torsional stresses occur on a fillet of the crankshaft under operating condition, applying surface treatment to the fillet portion is effective to improve fatigue strength of the crankshaft. Fatigue tests under high compressive mean stresses are demanded to confirm fatigue strength of surface treated parts. However, it is difficult to carry out the fatigue test in compressive plastic domain because the test specimens are buckled. Therefore, to conduct the fatigue tests under high compressive mean stresses without buckling, we designed the specimens shape with a notch in the parallel portion using plastic buckling analysis. Finally fatigue tests under high compressive mean stresses could be carried out using the designed fatigue test pieces, and the validity of the design method about fatigue test piece with notch was confirmed.