三点弯曲标定试验中双向主应变之间的关系

Relationship between the two principle strains in the three-point bending calibration experiment

用压痕应变法或盲孔法测量残余应力时,均需事先进行应力应变曲线的标定。为了方便获得试板表面单向拉伸或压缩应力状态,在试验标定时常常采用三点弯曲加载方法。由于三点弯曲过程中产生的非纯单向应力特性,使得两个主应变之间的关系偏离了虎克定律。结合试验分析,采用有限元模拟计算方法分析三点弯曲加载过程中两个主应变间的变化规律,同时分析不同规格的试板中应力分布的特点,试验结果对提高压痕应变法或盲孔法的系数标定精度具有指导意义。

The experimental calibration is often needed when the residual stresses are measured with indentation-strain method or blind-hole drilling method. In order to make easily uniaxial stress on a test plate surface, three-point bending is commonly used. Because the stress field in three-point bending is not exactly same as the uniaxial stress field, the relationship between the two principal strains departures from Hooke＇s law. In this paper, finite element method was employed to analyze the change rule between the two principal strains, and the result was compared with experimental one. The distributions of stress in different dimensions of plates were also discussed. All the analysis will be beneficial to improve the calibration precision with indentation-strain method or blind-hole drilling method.