比例与非比例加载下30CrMnSiA钢多轴高周疲劳失效分析

为了分析比例与非比例加载下,30CrMnSiA钢的多轴高周疲劳的失效规律。通过对30CrMnSiA钢材料开展比例与非比例(δ=90°)加载下的多轴高周疲劳试验,研究了应力幅比和相位差对疲劳寿命、断口特征及裂纹起裂角度的影响。试验结果表明,对于比例与非比例加载,随着应力幅比的增大,多轴疲劳寿命逐渐增加。对疲劳断口分析发现,裂纹萌生于试件表面,断口有明显的疲劳源区、扩展区和瞬断区,不同加载路径下的试件断口形式有明显差异。通过对起裂角度的分析发现,应力幅比大于0.25时表面裂纹有明显的第Ⅰ阶段向第Ⅱ阶段的转变,且第Ⅰ阶段沿着接近最大剪应力幅值平面方向扩展,第Ⅱ阶段沿着接近最大正应力平面方向扩展。此外,对典型试件的疲劳断口及表面扩展路径进行了分析,研究表明多轴疲劳试验试件裂纹的特征比值在0.3~0.5之间,且裂纹沿深度方向扩展至300 μm时占总寿命的85%以上。 

Analysis on multiaxial high-cycle fatigue failure of 30CrMnSiA steel under proportional and non-proportional loading

To analyze the failure law of high cycle multiaxial fatigue of 30CrMnSiA steel under proportional and non-proportional loading, multiaxial fatigue tests were carried out using 30CrMnSiA steel specimens under proportional and non-proportional (δ=90°) loading. The effects of stress amplitude ratio and phase angle on the fatigue life, fracture characteristics and crack initiation angle were analyzed. The results showed that the multiaxial fatigue life increased with the growing stress amplitude ratio for both proportional and non-proportional loadings. The fatigue source region, propagation region and final fracture region can be clearly observed. The transition of crack from stage Ⅰ to stage Ⅱ was observed when stress amplitude ratio was greater than 0.25 through analysis of crack initiation angles. And the stage Ⅰ propagation of the main crack was approximately along the maximum shear stress amplitude plane. Stage Ⅱ propagation of the main crack was approximately along the maximum normal stress plane. In addition, the crack aspect ratios of multiaxial fatigue test specimen were between 0.3 and 0.5, and the fatigue life corresponding to a 300 μm depth occupied more than 85% of the total fatigue life through analysis of fracture and surface crack path.