中碳车轮钢复合型裂纹疲劳扩展行为
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摘要
为了准确评估含缺陷车轮轮辋的安全性,通过对I型裂纹、II型裂纹及不同加载条件下的I+II复合型裂纹的疲劳试验,对中碳车轮钢疲劳裂纹扩展方向及门槛值进行了研究,得到了车轮钢复合型裂纹疲劳扩展的门槛值,验证了适合中碳车轮钢材料的复合型裂纹疲劳扩展预测准则。结果表明,在I+II复合型裂纹疲劳扩展试验中,裂纹扩展方向与最大切向应力(MTS)裂纹扩展准则预测值基本吻合。不同加载状态下I+II复合型裂纹疲劳扩展等效门槛值ΔKth,equ(力值比R=0.5)为3.0～3.8 MPa·m1/2。II型裂纹疲劳扩展时,微裂纹主要在主裂纹尖端剪应力作用下形核,受到拉-剪应力的一侧裂纹持续扩展,而受到压-剪应力的一侧裂纹可以形成,但扩展几十微米后停止扩展。
In order to accurately assess the safety of wheel rim with defects,fatigue testes of type I crack,type II crack and type I+II mixed mode crack under different loading conditions were done. The threshold value of fatigue propagation of mixed mode crack of wheel steel was obtained,and a suitable prediction criterion of mixed mode crack fatigue expansion for wheel steel was verified. The results show that the crack propagation direction for the I + II mixed mode crack is basically consistent with the predicted value of the maximum tangential stress(MTS)criterion in test. The equivalent threshold value of fatigue crack propagation for I+II mixed mode crack is ΔKth,equ=3.0-3.8 MPa·m1/2(load ratio R=0.5). The microcracks were formed at the tip of prefatigued crack mainly by shear stress. The microcrack at the zone with tensile-shear stress is extended continuously,but microcrack at the zone with compression-shear stress can be formed but it stopped after a few tens of micrometers propagation.
In order to accurately assess the safety of wheel rim with defects,fatigue testes of type I crack,type II crack and type I+II mixed mode crack under different loading conditions were done. The threshold value of fatigue propagation of mixed mode crack of wheel steel was obtained,and a suitable prediction criterion of mixed mode crack fatigue expansion for wheel steel was verified. The results show that the crack propagation direction for the I + II mixed mode crack is basically consistent with the predicted value of the maximum tangential stress(MTS)criterion in test. The equivalent threshold value of fatigue crack propagation for I+II mixed mode crack is ΔKth,equ=3.0-3.8 MPa·m1/2(load ratio R=0.5). The microcracks were formed at the tip of prefatigued crack mainly by shear stress. The microcrack at the zone with tensile-shear stress is extended continuously,but microcrack at the zone with compression-shear stress can be formed but it stopped after a few tens of micrometers propagation.
引文
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[2]刘杰.钢轨表面疲劳裂纹扩展机制[J].钢铁,2017,52(4):67.(LIU Jie. Analysis of propagation mechanism of fatigue crack on rail surface[J]. Iron and Steel,2017,52(4):67.)
[3]何小林,张澎湃,陈新,等.货车车轮轮辋裂纹扩展特征分析[J].铁道车辆,2017,55(12):12.(HE Xiao-lin,ZHANG Pengpai,CHEN Xin,et al. Analysis of features of development of cracking in wheel rims for freight cars[J]. Rolling Stock,2017,55(12):12.)
[4] Liu Y,Stratman B,Mahadevan S. Fatigue crack initiation life prediction of railroad wheels[J]. International Journal of Fatigue,2006,28(7):747.
[5]马世骧,胡泓. CTS试件中复合型疲劳裂纹扩展[J].力学学报,2006,38(5):698.(MA Shi-xiang,HU Hong. The mixed mode propagation of fatigue crack in CTS specimen[J]. Chinese Journal of Theoretical and Applied Mechanics,2006,38(5):698.)
[6] Seifi R,Omidvar N. Fatigue crack growth under mixed mode I+III loading[J]. Marine Structures,2013,34:1.
[7]李新宇,杨卯生,周晓龙,等. 15Cr14Co12Mo5Ni2齿轮钢的扭转疲劳特性及裂纹扩展行为[J].钢铁,2017,52(9):84.(LI Xin-yu,YANG Mao-sheng,ZHOU Xiao-long,et al. Torsion fatigue characteristics and crackpropagation behavior of15Cr14Co12Mo5Ni2 gear steel[J]. Iron and Steel,2017,52(9):84.)
[8] Doquet V,Bertolino G. A material and environment-dependent criterion for the prediction of fatigue crack paths in metallic structures[J]. Engineering Fracture Mechanics,2008,75(11):3399.
[9] Matsunaga H,Makizaki M,Socie D F,et al. Acceleration of fatigue crack growth due to occasional mode II loading in 7075aluminum alloy[J]. Engineering Fracture Mechanics,2014,123:126.
[10] Erdogan F,Sih G C. On the crack extension in plates under plane loading and transverse shear[J]. Journal of Basic Engineering,1963,85(4):527.
[11] Sih G C. Strain-energy-density factor applied to mixed mode crack problems[J]. International Journal of Fracture,1974,10(3):305.
[12] Hayashi K,Nemat-Nasser S. Energy-release rate and crack kinking under combined loading[J]. Journal of Applied Mechanics,1981,48(3):520.
[13] Sander M,Richard H A. Experimental and numerical investigations on the influence of the loading direction on the fatigue crack growth[J]. International Journal of Fatigue,2006,28(5):583.
[14] Richard H A. Safety estimation for construction units with cracks under complex loading[J]. International Journal of Materials and Product Technology,1988,3(3):326.