拉—拉疲劳下15MnMoVN多裂纹扩展研究

为分析单裂纹或多裂纹在裂纹面承受疲劳拉伸载荷作用下尖端应力强度因子变化规律和裂纹形貌变化以及疲劳寿命情况,以含不同初始长深比的半椭圆单裂纹或双裂纹的薄片试样为研究对象,对试样在应力比R=0.1的疲劳拉伸载荷下单裂纹或双裂纹情况进行了仿真分析。建立含裂纹试样的有限元模型,仿真分析了裂纹在扩展过程中尖端应力强度因子的分布情况,并将单裂纹扩展结果与双裂纹相互作用影响下的结果进行了对比研究;进行含裂纹试样的疲劳实验,分析了含单裂纹或双裂纹的试样的断裂面的形成原因,并验证仿真结果正确性。结果表明,裂纹面之间的相互作用会逐渐影响裂纹的扩展方向、扩展速率以及在扩展过程中尖端应力强度因子的变化趋势;而且初始形貌为半椭圆形的双裂纹在相互作用影响下会逐渐过渡到半圆形。

Multi-crack propagation of 15MnMoVN steel under tensile fatigue

To analyze varying laws of crack tip stress intensity factor, crack morphology and fatigue life of single crack and multi-crack on 15MnMoVN steel specimens under fatigue tensile load exerted on crack surface, taking 15MnMoVN steel sheet samples containing semi-elliptic single crack or multi-crack with various initial length-to-depth ratios as study objects, simulation analyses were performed for crack propagation of these single crack and multi-crack on these sheet samples under fatigue tensile load with stress ratio R=0.1.The FE model for samples containing cracks was built, and tip stress intensity factor’s distribution was simulated in process of crack propagation.The propagation results of single-crack were compared with those under effects of double-crack interaction.The fatigue tests were done for samples containing cracks to analyze the forming reason of fracture plane on samples containing single crack or double-crack, and verify the correctness of simulation results.The results indicated that interaction between cracks can gradually affect crack propagation direction, propagation rates and varying trend of tip stress intensity factor in propagation process; an initial semi-elliptic double-crack can gradually transit to a semi-circle one under effects of interaction between two cracks.