Influence of Surface Rolling Time on Short Fatigue Crack Behavior of LZ50 Axle Steel
Based on the mean fatigue life of LZ50 axle steel specimens which were unrolled before testing,five surface rolling times were determined according to the fatigue life fraction,i.e.,f=0.0,0.3,0.5,0.6,and 0.7.Five groups of smooth hourglass shaped specimens which were turned and rolled at above surface rolling times were tested by a replication technique.Results show that with a given dominant short crack size,crack growth rate after surface rolling occurs much slower than that before rolling.However,the more prolonged the surface treatment is performed,the greater the growth rate occurs at the transition point between the micro-structural short crack (MSC) stage and the physical short crack (PSC) stage.Furthermore,influenced by the change of surface hardness and residual compressive stress,the effective short crack density in all the specimens,which is the average number of short cracks per unit area,decreases significantly after rolling than before.Focusing on the density after surface rolling,it is evident that the highest effective short crack density for the five studied groups of specimens increases from 662 mm-2 to 941 mm-2 with postponed rolling time.On the other hand,the average fatigue life for each group of specimens decreases with postponed surface treatment time.The average life of the initial rolled specimens was 882,562 cycles,while that of specimens turned and rolled at a 0.7 fatigue life fraction is 618,640 cycles.Therefore,the surface rolling procedure can improve the fatigue performance characteristics of the material.The choice of rolling time may affect the short fatigue crack behavior greatly.The earlier the surface treatment is performed,the better the collective effect of short cracks can be restrained as well as the longer the fatigue life of the material will be.
Fatigue short crack surface rolling time LZ50 axle steel
Bing Yang YongXiang Zhao
State Key Laboratory of Traction Power,Southwest Jiaotong University,610031,China
国际会议
北京
英文
1-8
2013-06-16（万方平台首次上网日期，不代表论文的发表时间）