初始尺寸对超声疲劳试样的影响及铝合金6063疲劳试验验证

狗骨形试样具有中间等截面段试验有效区。采用悬链线代替圆弧线的轮廓方程,获得了狗骨形试样的解析计算方法。分析结果表明,试样初始尺寸在一定范围内取值时轮廓方程代替所引起的误差控制在3%以内。可通过增大变截面段长度或粗、细端的半径比来缩短试样长度,但增大变截面长度会降低试样位移应力系数。尽管狗骨形试样的位移应力系数不如沙漏形试样,但狗骨形比沙漏形更节省试验材料,而且其位移应力系数也足够满足试验要求。铝合金6063的超声疲劳试验表明,狗骨形试样的设计等式是可行的。铝合金6063的S-N曲线呈现持续下降的趋势,其疲劳裂纹扩展以剪切方式进行,并且呈现裂纹表面萌生机制。疲劳源区与裂纹扩展区之间存在明显的台阶。

Effect of initial size on ultrasonic fatigue specimen and the ultrasonic fatigue behavior of aluminum alloy 6063

The middle equal section is the effective area of dog-bone-shaped specimen for ultrasonic fatigue test.Design of specimen could be completed by using catenary equation instead of circle equation.The re-sult show that error had been less than 3% when the initial sizes of specimen are in definite range.The spec-imen length could be reduced by enhancing the length of variational section or the ratio of radius.Enhancing the length of variational section would reduce the displacement-stress coefficient.Comparatively,the dog-bone-shaped specimen could save more materials,and sandglass specimen could obtain more high stress magnification level.The design of dog-bone-shaped specimen was testified by the The ultrasonic fatigue test of aluminum alloy 6063.The results show that the S-N curve of aluminum alloy 6063 is a continuum descend curve.Its fatigue crack is expanded by shear and subsurface crack initiation.Obvious sidestep could be found between crack initiation area and expanding area.