组合加载下碳素工具钢中疲劳小裂纹的门槛区行为特征

通过考察碳素工具钢的表面滑移、疲劳破坏及表面裂纹的扩展条件，以统一的局部应力讨论了光滑试样和裂纹试样的疲劳特征。分析和实验结果表明，在裂纹试样的名义应力小于光滑试样表面滑移门槛应力的范围内，线弹性断裂力学是有效的，对应裂纹扩展门槛值的裂尖性区为一常数。

SMALL CRACK PROPAGATION THRESHOLD OF CARBON TOOL STEEL UNDER COMBINED STRESSES

By investigating the criteria of slip initiation,fatigue fracture and surface crack propagation in a carbon tool steel under combined stresses, fatigue features of smooth and cracked specimens are discussed from the point of view of local stress. Results show that, for short cracks, linear elastic fracture mechanics is applicable provided that the nominal stress is smaller than the slip initiation threshold stress of the material, and the size of plastic zone around a crack tip is almost a constant regardless of the crack length and deformation mode under threshold condition.