Q345高周疲劳失效机理及固有耗散能研究
发布时间：2018-12-20 07:31
【摘要】：双相钢Q345多用于建筑或机械结构的承力构件,循环载荷的长期作用使得构件在低于其静强度的载荷条件下发生疲劳断裂,经济可靠的强度设计需要对材料的疲劳失效进行研究。作者利用电磁谐振高频疲劳试验机,在载荷频率140 Hz、应力比为 1条件下,得到不同失效概率时材料高周疲劳(104周次疲劳寿命107周次)应力 寿命(S-N)曲线。利用扫描电子显微镜观察材料受到循环载荷作用后的显微结构的变化和疲劳失效后试样的断面微观形貌,研究材料疲劳裂纹的萌生和扩展。同时,利用红外热像仪记录Q345试样表面的温度场随循环载荷作用周次的变化,研究材料在高频循环载荷作用下的固有耗散能。双相钢Q345在高频循环载荷作用下的疲劳失效主要是由于铁素体 珠光体双相结构在循环载荷作用下的微观强度差异使得微观裂纹首先萌生于相对薄弱的铁素体晶粒,且随循环载荷周次的增加而裂纹逐渐扩展。珠光体晶粒对疲劳裂纹的扩展起阻碍作用,使得疲劳裂纹沿铁素体或铁素体与珠光体之间的晶界向前扩展。当载荷幅值低于其高周疲劳极限时,试样表面温升不明显;有限寿命的载荷条件下,试样表面温度场的变化受到材料微观变形的影响,基于试样表面温度场的变化,能快速确定材料的高周疲劳强度极限。高频循环载荷作用下,单位体积材料的固有耗散能与载荷之间呈非线性关系,在热力学框架内建立了材料的固有耗散能表征模型。
[Abstract]:Dual-phase steel Q345 is mostly used in load-bearing members of building or mechanical structures. The long-time cyclic load causes the fatigue fracture of the members under the loading condition below its static strength. The economic and reliable strength design needs to study the fatigue failure of materials. The high cycle fatigue (S-N) curves of materials with different failure probability were obtained by using electromagnetic resonance high frequency fatigue testing machine under the loading frequency of 140 Hz, stress ratio of 1. The microstructure changes of materials subjected to cyclic loading and the microstructure of specimens after fatigue failure were observed by scanning electron microscope (SEM) to study the initiation and propagation of fatigue cracks. At the same time, the temperature field on the surface of Q345 sample was recorded by infrared thermal imager with the cycle of cyclic load, and the inherent dissipation energy of the material under high frequency cyclic load was studied. The fatigue failure of dual phase steel Q345 under high frequency cyclic loading is mainly due to the difference in micro strength of ferrite pearlite dual phase structure under cyclic loading, which results in the initiation of microcracks at first in relatively weak ferrite grains. And the crack grows gradually with the increase of cyclic load cycle. The pearlite grain hinders the growth of fatigue crack, which makes the fatigue crack propagate along the grain boundary between ferrite or ferrite and pearlite. When the load amplitude is lower than its high cycle fatigue limit, the surface temperature rise is not obvious. The change of surface temperature field is affected by the micro-deformation of the material under the loading condition of finite life. Based on the change of the surface temperature field of the specimen, the high cycle fatigue strength limit of the material can be determined quickly. Under high frequency cyclic loading, the intrinsic dissipation energy of unit volume material is nonlinear to the load. A characterization model of inherent dissipation energy of the material is established within the framework of thermodynamics.
【作者单位】： 四川大学空天科学与工程学院;四川大学建筑与环境学院;
【基金】：国家自然科学基金资助项目(11327801;11372201) 长江学者和创新团队发展计划资助项目(IRT14R37)
【分类号】：TG142.1
[Abstract]:Dual-phase steel Q345 is mostly used in load-bearing members of building or mechanical structures. The long-time cyclic load causes the fatigue fracture of the members under the loading condition below its static strength. The economic and reliable strength design needs to study the fatigue failure of materials. The high cycle fatigue (S-N) curves of materials with different failure probability were obtained by using electromagnetic resonance high frequency fatigue testing machine under the loading frequency of 140 Hz, stress ratio of 1. The microstructure changes of materials subjected to cyclic loading and the microstructure of specimens after fatigue failure were observed by scanning electron microscope (SEM) to study the initiation and propagation of fatigue cracks. At the same time, the temperature field on the surface of Q345 sample was recorded by infrared thermal imager with the cycle of cyclic load, and the inherent dissipation energy of the material under high frequency cyclic load was studied. The fatigue failure of dual phase steel Q345 under high frequency cyclic loading is mainly due to the difference in micro strength of ferrite pearlite dual phase structure under cyclic loading, which results in the initiation of microcracks at first in relatively weak ferrite grains. And the crack grows gradually with the increase of cyclic load cycle. The pearlite grain hinders the growth of fatigue crack, which makes the fatigue crack propagate along the grain boundary between ferrite or ferrite and pearlite. When the load amplitude is lower than its high cycle fatigue limit, the surface temperature rise is not obvious. The change of surface temperature field is affected by the micro-deformation of the material under the loading condition of finite life. Based on the change of the surface temperature field of the specimen, the high cycle fatigue strength limit of the material can be determined quickly. Under high frequency cyclic loading, the intrinsic dissipation energy of unit volume material is nonlinear to the load. A characterization model of inherent dissipation energy of the material is established within the framework of thermodynamics.
【作者单位】： 四川大学空天科学与工程学院;四川大学建筑与环境学院;
【基金】：国家自然科学基金资助项目(11327801;11372201) 长江学者和创新团队发展计划资助项目(IRT14R37)
【分类号】：TG142.1
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