Host: The Japan Society of Mechanical Engineers
Name : [in Japanese]
Date : October 07, 2017 - October 09, 2017
Plane bending fatigue tests and fatigue crack propagation tests were conducted at room temperature in a laboratory atmosphere to examine the effect of stress ratios on the fatigue crack initiation and propagation behavior of magnesium alloy (AZ31). Plane bending fatigue tests were performed using computer-controlled electro-dynamic fatigue testing machine under stress ratios of -1, -0.1, 0.1 and 0.5. Result of fatigue tests, fatigue strength at 107 cycles of magnesium alloy tended to decrease as stress ratio increased. In addition, the specimen surface were observed by optical microscopy, and the specimen surface near crack initiation site were analyzed using the electro backscattered diffraction (EBSD) to discuss the small fatigue crack initiation mechanism. On the basis of EBSD analysis, the crack initiation and propagation mechanism was not influenced by twinning. Furthermore, a near-threshold fatigue crack propagation tests were conducted using the compact-tension C(T) specimens under several stress ratios. Threshold stress intensity range, ΔKth, decreased and the crack propagation rate, da/dN, became high as stress ratio increased.
