铸造钛合金ZTC4不同应变比下的低周疲劳行为

Low cycle fatigue behavior of cast titanium alloy ZTC4 at different strain ratios

采用岛津液压伺服疲劳试验机研究了铸造钛合金ZTC4在不同应变比下(R=-1、0.06和0.5)的低周疲劳行为。对比分析了不同应变比下应力-应变迟滞回线、循环应力响应曲线以及疲劳寿命的差异,并采用SWT模型和Walker等效应变模型对不同应变比下的试验结果进行表征。结果表明:在200℃时,应变比为-1时,迟滞回线基本以原点对称,且随着应变水平的增大,迟滞回线包围的面积呈上升趋势;应变比为0.06和0.5时,滞后环沿坐标轴发生了平移,且随着应变水平的降低,迟滞回线沿拉应力的方向移动;不同应变比下合金的循环疲劳寿命相差甚微,SWT模型和Walker等效应变模型能很好的表征材料不同应变比下的疲劳试验结果,精度在±2倍的分散带内。

The low cycle fatigue(LCF) behavior of cast titanium alloy ZTC4 at different strain ratios(R=1, 0. 06 and 0. 5) was studied by using a EHF-EA10 fatigue testing system. The differences of stress-strain hysteresis loop, cyclic stress response curve and fatigue life under different strain ratios were compared and analyzed, and the test results under different strain ratios were characterized by SWT model and Walker equivalent variable model. The results show that when the strain ratio is-1 at 200 ℃, the stress-strain hysteresis loop curves are symmetric and the average stress is approximately equal to zero, and with the increase of strain level, the area surrounded by hysteresis loop tends to rise;when the strain ratio is 0.06 and 0.5, the hysteresis loop moves along the coordinate axis, and with the decrease of strain level, the hysteresis loop moves along the direction of tensile stress. There is little difference in cyclic fatigue life of the alloy under different strain ratios. SWT model and Walker model can well characterize the fatigue test results of the alloy under different strain ratios, and the accuracy is in the scatter band of ±2 times.