基于单轴缺口试样的一种低周疲劳测试方法与应用

Low cycle fatigue test method based on uniaxial test strain of notch specimens and its application

对于漏斗式小曲率半径的缺口圆棒与缺口薄片试样提出了一种采用轴向测量应变的低周疲劳测试方法。通过有限元分析建立小曲率半径的漏斗式缺口圆棒或薄片试样的轴向测试应变到缺口根部Tresca等效应变的应变转换模型,并由疲劳损伤等效假设建立基于缺口试样疲劳实验数据的材料低周疲劳寿命估算模型;完成了大曲率半径漏斗光滑试样和小曲率半径缺口试样的Ti-4Al-2V合金低周疲劳试验,基于缺口试样的疲劳试验所建立的材料低周疲劳寿命估算模型与基于大曲率半径漏斗试样的低周疲劳寿命估算模型有良好的符合度。新方法也方便应用于N18锆合金缺口薄片试样的材料高温单轴低周疲劳行为试验研究,可推荐于材料低周疲劳测试规范修订采用。文中获得的Ti-4Al-2V合金和N18锆合金的不同温度下单轴低周疲劳行为试验数据与寿命估算模型有宜于工程应用。

A low cycle fatigue test method was presented for small curvature radius funnel-like notched specimens using axial strain as control strain. Through finite element analysis, the strain conversion model for small curvature radius funnel-like notched specimens and thin specimens from uniaxial testing strain to Tresca equivalent strain at the root of notch was established. Based on the assumption of fatigue damage equivalent and fatigue test data of notched specimen, the model for low cyclic life estimation was proposed, a series of low cycle fatigue tests for Ti--4Al-2V alloy using large curvature radius smooth notched specimens and small curvature radius notched specimens were completed, respectively. The low cyclic life estimating model on small curvature radius notched specimens was close to the estimating models based on smooth specimens. The new method can also be used for low cyclic fatigue test on N18 alloy thin sheet specimens at elevated temperature, so it can be recommended for the test standard of low cycle fatigue. In this paper, the experimental data for Ti-4Al-2V and N18 zirconium alloys at different temperatures and the proposed low cyclic life estimating modes are beneficial to the engineering application.