45碳钢低周疲劳与应力循环棘轮失效的实验研究

对调质处理的45碳素结构钢进行了应变循环低周疲劳实验以及应力控制棘轮失效实验．对于前者进行了带平均应变和不带平均应变的实验，以研究平均应变对低周疲劳特性的影响；对于后者研究了平均应力和应力幅值对棘轮失效的影响．应变循环实验表明：平均应变对循环饱和行为以及低周疲劳循环失效圈数并没有明显的影响，但对材料的循环初期循环塑性行为有影响．棘轮失效实验结果表明：当应力幅值较大而平均应力较小时，材料的棘轮失效主要归于较大塑性应变幅值引起的低周疲劳破坏；当平均应力较大而应力幅值相对较小时，材料的棘轮失效主要归于较大的棘轮应变引起的材料韧性破坏，其失效准则可以用最大单调极限应变来表征．

AN EXPERIMENTAL STUDY OF LOW CYCLE FATIGUE AND CYCLIC STRESS RATCHETING FAILURE OF 45 CARBON STEEL

The cyclic strain low cycle fatigue and cyclic stress ratcheting failure of 45 carbon steel treated by quenching and tempering were experimentally investigated. The tests for cyclic straining low cycle fatigue with or without mean strains were carried out to investigate the effect of mean strain on low cycle fatigue property. The effects of mean stress and stress amplitude on the ratcheting failure were experimentally studied under stress controlled cycling tests. The strain cycling tests show that the effect of mean strain is very little on the cyclic saturated deformation behavior and the number of cycles to failure of low cycle fatigue, but very significant on the initial cyclic deformation behavior of the material. The stress cycling tests indicate that the ratcheting failure of the material is mainly controlled by the low cycle fatigue failure due to the large plastic strain amplitude for the cyclic stressing under large stress amplitude and small mean stress, and under the opposite condition, is mainly controlled by the ductile failure of the material due to the large ratcheting strain, whose failure criterion can be characterized by the maximum monotonie limit strain.