基于主应力法和修正的Crossland疲劳准则的动车组车轮疲劳强度评定方法

Assessment Method for Fatigue Strength of EMU Wheel Based on Principal Stress Method and Amendatory Crossland Method

以全尺寸车轮的弯曲疲劳极限表征疲劳强度极限状态,改变传统主应力法通过尺寸系数和表面加工系数修正小试样疲劳强度计算结果的做法,从而避免系数取值中主观因素对疲劳强度评定结果的影响;以全尺寸车轮的弯曲疲劳极限替代全尺寸车轮辐板的对称扭转疲劳极限作为判定依据,修正Crossland疲劳准则,并类比Sines疲劳准则,确定准则中应力张量第1应力不变量最大值的系数;以CRH系列动车组中的轴对称车轮和非轴对称车轮为评定对象,对给出的主应力法和修正的Crossland疲劳准则的适用性进行仿真分析,并与用最大剪应变准则和Brown-Miller准则评定的结果进行对比。结果表明:主应力法适用于轴对称车轮和非轴对称车轮2种车轮的疲劳强度评定,修正的Crossland疲劳准则仅适用于非轴对称车轮的疲劳强度评定;若非轴对称车轮的辐板孔边处疲劳强度安全系数区间为(1.0,1.1)时,如果用主应力法评定,还须采用修正的Crossland疲劳准则进行补充校核,以保证动车组车轮的运用安全。

The treatment that wheel＇s strength state is described by full-size wheel＇s bending fatigue limit changes the way of correction result of sample fatigue strength by using size factor and surface machining factor for traditional principal stress method,and the impact of subjectivity of determining such factors＇ value on the assessment result of fatigue strength can be avoided.Taking full-size wheel＇s bending fatigue limit instead of full-size wheel web＇s torsion fatigue limit as judgment criterion,an amendatory Crossland method is proposed.The coefficient of the maximum of the first stress invariable for Crossland method is obtained by comparing with Sines method.Taking CRH wheels,including axisymmetric wheels and nonaxisymmetric wheels as research objects,the applicability analysis of both the principal stress method and the amendatory Crossland method has been contrasted with maximum shear strain method and Brown-Miller method by using FEA simulation.The analysis result shows that the principal stress method is available for the fatigue strength assessment of both axisymmetric wheels and non-axisymmetric wheels,and the amendatory Crossland method is only available for non-axisymmetric wheels.For the assurance of operational safety of EMU wheels,if the safety factor of fatigue strength is from 1.0 to 1.1 for web holes of non-axisymmetric wheels by using the principal stress method,the amendatory Crossland method should be applied as a supplement.