表面粗糙度对Glidcop和Q345低周疲劳寿命影响的试验研究

为考察表面粗糙度对弥散增强铜合金Glidcop和低合金钢Q345疲劳寿命的影响,对两种材料都加工了不同粗糙度等级的试样,在常温下进行了应力控制的低周疲劳试验,并对断后的试样进行了扫描电镜观察。结果表明,两种材料共有的现象是:粗糙表面削弱了低周疲劳性能,随着表面粗糙度的增大,低周疲劳寿命呈下降趋势;表面粗糙度对主裂纹的形成时间有影响。不同的现象是:低周疲劳寿命与表面粗糙度的关系Glidcop为线性,而Q345则为幂函数;Glidcop的断口有轻微颈缩,疲劳辉纹明显,Q345的主裂纹沿着试样的径向和周向同时扩展,大粗糙度下辉纹支离破碎。因此,表面粗糙度对疲劳寿命的影响既表现出共同的现象,又呈现为材料相关性。本文的结果将为这两种材料制成的承受低周疲劳构件的表面粗糙度选取提供参考。

Experimental Study of Surface Roughness Effect on Low Cycle Fatigue Life of Glidcop and Q345

In order to investigate the effect of surface roughness on fatigue life of diffusion enhanced copper alloy Glidcop and low alloy steel Q345, specimens with different levels of roughness for both materials were machined and stress-controlled low cycle fatigue experiments were carried out at room temperature. Then the fractured specimens were observed by scanning electron microscope. Experimental results show that there are some common phenomena for both materials: rough surface weakens low cycle fatigue performance; low cycle fatigue life presents a downward trend with the increase of surface roughness; surface roughness affects the formation time of main crack. However, there are also some different phenomena for above two materials: for Glidcop, relationship between the low cycle fatigue life and the surface roughness is linear, while for Q345, that is power function; slight necking is found and obvious fatigue striation are observed in Glidcop specimens' fracture; for Q345 specimens, the main crack synchronously propagates along both radial and circumferential directions and fatigue striation is fragmented in specimens with large roughness. So, the effect of surface roughness on fatigue life not only exhibits common phenomena, but also presents material dependence e. Above results may provide a reference for surface roughness selection of structural components made of above two materials and subjected to low cycle fatigue load.