预应变对中碳钢扭转疲劳特性的影响

应用扭转疲劳试验机对退火后的非预应变45#钢及其3种预应变材料进行 实验. 实验结果表明：预应变量小于5%时，与非预应变材料相比疲劳极限降低10\%； 预应变量大于5{%}时，随着预应变量的增加，其疲劳极限有恢复的趋势，当预应变量达到 8%时，预应变材料与非预应变材料的疲劳极限几乎相等；当循环应力达到1*10^7$时，各种试件表面都有明显的停留裂纹存在.

EFFECT OF PRE-STRAIN ON TORSIONAL FATIGUE PROPERTIES OF MIDDLE CARBON STEEL

Fatigue test was performed to investigate the reversed torsional fatigue properties of non-pre-strained carbon steel and three kinds of pre-strained carbon steel. Main results summarized in this study are as follows: In the case of pre-strain rate lower than 5{\%}, the fatigue limit is 10{\%} lower than the non-pre-strained specimen. In the case of pre-strain rate higher than 5{\%}, the fatigue limit increases with increasing pre-strain rate. For the pre-strain rate of 8{\%}, the fatigue limit is equal to the fatigue limit of non-pre-strained specimen. The non-propagatinig cracks are observed in all specimens' surfaces after 1$\times $10$^{7}$ cycles under the stress amplitude of fatigue limit.