关于帕里斯法则中m值变化条件的研究

Variation Condition of Index m in Paris Formula

帕里斯疲劳裂纹扩展法则中的指数m值一般为2～4,且在裂纹稳定扩展的第二区域内一般为常数。而对载荷频率与塑性区域尺寸之间关系仅有定性描述。基于ASTME647-1991进行的试验,指出了m会变化,对载荷频率与塑性区域尺寸之间的关系进行了定量研究,导出了m值变化点的发生条件式。随着频率的增高,塑性区域尺寸变小。频率一定时,应力比R值大时的塑性区域的尺寸比R值小时的大。频率越高,变化点处的ΔKt也越大。

In general, the index m in Paris law is a constant. And the relation between plastic zone size and load frequency is only qualitatively analyzed up to now. But, the variation phenomena of the index m were found in the experiments on the brass CT specimens under different load frequencies and stress ratios. Based on the experimental results, the quantitative relation betweenand plastic zone size and load frequency, and variation conditions were reported. According to the condition formula, the plastic zone size gets smaller with larger load frequency. With a constant load frequency, ΔK at change point gets larger with larger stress ration. Stress intensity factor range, ΔK, at change point becomes larger with increased load frequenyc.