中文摘要：

该文研究了剪应力梯度对疲劳寿命的影响。首先,基于缺口件疲劳寿命研究中常用的应力场强法,针对纯扭载荷作用的圆管试件,推导出一种新的剪切疲劳损伤参量。该参量依据疲劳破坏区内各点的相对剪应力梯度,得到区域内的加权平均应力,从而全面描述材料在剪应力作用下的疲劳损伤水平。然后,使用30Cr Mn Si A合金钢进行了拉压、扭转疲劳试验。通过对比分析试验结果可以证明：当危险点应力水平相同时,剪应力梯度的存在可以使材料疲劳寿命增加;而该文提出的剪切损伤参量可以很好地描述这种影响。

英文摘要：

The shear stress gradient effect is studied in this paper. First, based on the stress field intensity approach, which is very commonly used for the fatigue life prediction of notched specimens, a novel shear stress parameter is proposed. In this parameter, a weighted average stress is calculated near the fatigue critical point according to the relative shear stress gradient. Then, a series of tension-compressional and torsional fatigue tests are conducted on 30CrMnSiA steel. Based on the test results, the existence of the shear stress gradient effect is verified. It is found that, compared with the tension-compressional loadings which have no stress gradient, the specimens have longer fatigue lives under torsional loadings at the same stress level. The proposed shear stress parameter is proved to have a good capability to describe the shear stress gradient effect.