Fatigue strength and fracture mechanisms in severely drawn eutectoid steel wires

严重拉拔共析钢丝的疲劳强度和断裂机制

基本信息

批准号：
09650086
负责人：
KATAGIRI Kazumune
金额：
$ 2.11万
依托单位：
Iwate University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1997
资助国家：
日本
起止时间：
1997 至 1998
项目状态：
已结题

项目摘要

Following results clarifying the effects of various factors on the fatigue strength of eutectoid steel wires were obtained through the experiments.1. Within the drawing strain range of epsilon 0 to 3.8, fatigue strength increased monotonically up to 800MPa with increase in epsilon , as in the case of ferritc steel in which the degree of increase is low. In some cases, however it had a peak value at epsilon=2.5 depending on the fabrication condition. It increased with decrease in the wire diameter and did not depend on the lamellar spacing (0.01-0.02 mu m).2. Associated with high density dislocations and the narrow lamellar spacing observed in TEM, the hardness and tensile residual stress in the surface layer increased with increase in epsilon up to Hv=520 and 1000 MPa.3. While the tensile residual stress monotonically decreased with increase in bluing temperature and diminished at 500ﾟC, the hardness increased to a peak value of Hv=650 by bluing at 300ﾟC The fatigue limit increased to a peak of 900MPa by bluing at 400ﾟC due to combined effects of strain aging, recovery and relaxation of residual stress. By shot peeing, the residual stress decreased from 1000 to -300 MPa and the highest fatigue limit of 1200 MPa was obtained4. Fatigue crack initiated from inclusions or the ferrite layer in the surface region and changed its direction at the boundary of pearlite colony. The ratio of the duration for fatigue crack initiation in the fatigue life-time increased with increase in epsilon5. With increase in epsilon , the *K_<th> decreased through decrease in the roughness induced crack closure level due to decrease in the pearlite colony size. The fatigue crack resistance in Paris' region also increased and the "m-value" decreased.

以下结果阐明了各种因素对共性钢丝疲劳强度的影响，通过实验1。在Epsilon 0至3.8的图形应变范围内，疲劳强度会随着Epsilon的增加而单调增加到800MPa，如Ferritc钢的增加，在该钢的情况下，增加程度较低。在某些情况下，但是根据制造条件，它的峰值在epsilon = 2.5。它随着电线直径的降低而增加，不依赖于层间距（0.01-0.02 mu m）。2。与高密度位错和在TEM中观察到的狭窄层状间距有关，表面层中的硬度和拉伸残留应力随着Epsilon的增加而增加，直至HV = 520和1000 MPA.3。虽然拉伸残留应力随着蓝色温度的升高而单调降低，并在500℃下降低，但由于在300°C时蓝色在300°C时，硬度增加到HV = 650的峰值，疲劳极限增加到900MPa的峰值为900MPa，这是由于蓝色在400°C时的峰值，这是由于应变衰减，恢复和残留残基压力的综合作用而在400°C下增加。通过射击，残留应力从1000 mPa降低到-300 MPa，获得了1200 MPa的最高疲劳极限4。疲劳裂纹是从夹杂物或表面区域的铁氧体层引发的，并在珠光体菌落边界上改变了其方向。疲劳寿命中疲劳裂纹开始的持续时间比Epsilon5的增加。随着Epsilon的增加，由于珠光体菌落大小的降低， *K_ <th>通过粗糙度诱导的裂纹闭合水平下降而减小。巴黎地区的疲劳裂纹阻力也增加，“ M值”减少。