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随着我国铁路提速重载运输的发展,货车车轮踏面承受的热负荷作用越来越大,并由此产生较为严重的踏面热裂纹及剥离掉块等相关伤损。通过分析货车车轮踏面热裂纹产生机理,结合现场观察到的车轮踏面热裂纹位置和形态,建立了位于踏面中部的半椭圆形热裂纹模型。根据断裂力学知识,推导确定出裂纹形态a/c比值、裂纹面名义正应力σnom、疲劳门槛值σKth和断裂韧度KIC为影响车轮断裂的主要因素,并采用典型车轮应力估算了车轮踏面热裂纹的安全尺寸和容限尺寸。评估得到的车轮踏面热裂纹的安全尺寸约为0.08~0.16mm,容限尺寸约为10.0~27.0mm,二者均受车轮应力影响较大。但考虑车轮踏面在制动过程中的马氏体相变,可以认为车轮踏面基本不存在热裂纹安全尺寸。
With the development of China’s railway speeding heavy-haul transport, the heat load on the truck wheel tread is more and more affected, resulting in more serious hot cracking and peel-off of the tread. Based on the analysis of the mechanism of the hot cracks in the tread of the truck wheel and the location and shape of the hot cracks on the wheel tread observed in the field, a semi-elliptical hot crack model in the middle of the tread was established. According to the knowledge of fracture mechanics, the a / c ratio, the nominal normal stress σnom, the fatigue threshold σKth and the fracture toughness KIC are the main factors affecting the wheel rupture. The typical wheel stress is used to estimate the wheel tread thermal crack The safety size and tolerance size. The safety dimension of the hot wheel tread cracks evaluated is about 0.08-0.16mm and the tolerance size is about 10.0-27.0mm, both of which are greatly affected by wheel stress. However, considering the martensitic transformation of the wheel tread during braking, it can be considered that there is basically no safety dimension of the hot crack on the wheel tread.