基于数值方法的超声疲劳应力计算方法修正及应用

Modification and application of ultrasonic fatigue stress calculation methods based on numerical methods

采用有限元方法在考虑放大器影响的情况下(简称整体法)对6082-T6铝合金母材及其接头的超声疲劳试样进行了尺寸设计,并与采用传统解析法设计的超声疲劳试样尺寸进行了对比.结果表明,采用整体法得到的试样的共振频率与试验频率更接近,且几乎不受预紧力和外加载荷影响,但应力位移系数与传统解析法有较大差别.同时采用两种方法对6082-T6铝合金搅拌摩擦焊接头在应力比R=-1和R=0.1下的超声疲劳试验数据进行对比分析,发现当R=-1时采用整体法得到的疲劳强度偏高,而当R=0.1时两种方法几乎无差别.

Finite element method was used to design the dimensions of ultrasonic fatigue specimens of 6082-T6 aluminium alloy base material and its joints, where taking into account the effect of amplifiers(here called the holistic method). A comparison made with the dimensions of ultrasonic fatigue specimens designed by the conventional analytical method,shows that the resonant frequencies of the specimens obtained by the holistic method are closer to the test frequencies, and were almost independent of the preload and applied loads.Howerver, the stress-displacement coefficients differed significantly from those of the conventional analytical method. The ultrasonic fatigue test data of friction stir welding joints of 6082-T6 aluminium alloy at stress ratios of R =-1 and R = 0.1 were also compared and analysed by two methods. It is found that the fatigue strength obtained by the holistic method is high when R =-1, but there is almost no difference between the two methods when R = 0.1.