最新色国产精品精品视频,中文字幕日韩一区二区不卡,亚洲有码转帖,夜夜躁日日躁狠狠久久av,中国凸偷窥xxxx自由视频

The thermal fatigue properties of multicomponent Al-7Si-0.3Mg aluminum alloys in three different treatment states at different temperatures were studied. The integral method and secant method were proposed to calculate the thermal fatigue crack propagation life, and the thermal fatigue crack growth behavior of the alloys was analyzed. The results indicate that the temperature change has a direct effect on the thermal fatigue crack propagation rate of the multicomponent Al-7Si-0.3Mg aluminum alloys. The thermal fatigue properties of the multicomponent Al-7Si-0.3Mg alloys with addition of Cu, Mn, Ti, and other elements after refinement and direct refinement are superior to those of the as-cast Al-7Si-0.3Mg alloys. The growth behavior of thermal fatigue cracks mainly includes the initiation and propagation of thermal cracks. The initiation of thermal fatigue crack requires a certain incubation period and the crack is generated at the V-notch. When the alternating thermal stress exceeds the yield strength σ_s of alloys, different types of thermal fatigue cracks appear at the stress concentration parts or at defects of the V-notch but with only one main crack. When the angle between the crack tip propagation path and the major axis direction of the second phase particle is less than 45°, the crack propagation extends further along the edge of the second phase particles; when the angle between the crack tip propagation path and the minor axis direction of the second phase particle is less than 45°, the crack passes through the second phase particle and extends forward.