动态Nadal脱轨评判准则的推导与应用

The Derivation and Application of a Dynamic Nadal Derailment Criterion

当轮轨接触状态处于小冲角或负冲角时,若基于经典Nadal公式评判车辆运行安全,可能出现将非脱轨误判为脱轨的现象。针对该问题,从机理分析的角度出发,深度探讨经典Nadal脱轨评判的局限性;通过轮轨蠕滑特性分析,引入实时的有效摩擦系数上限值,推导一个能够考虑冲角影响的改进型脱轨限度,形成新的动态Nadal脱轨评判准则;最后,通过应用算例验证改进型脱轨限度的有效性。结果表明,改进后的动态Nadal脱轨评判准则考虑了轮轨接触冲角的影响,与经典Nadal脱轨评判相比具有较小的保守性,能够科学有效地降低脱轨评判的误判率。目前,该限度仅从理论层面予以验证,在实际应用中建议考虑安全系数裕量进行评判,以确保列车运行安全。

When the wheel-rail contact is at a small or negative angle of attack,application of the classical Nadal derailment evaluation criterion may lead to a misjudgment of non-derailment in the process of evaluating the running safety of vehicles.In view of this problem,this paper first discuss deeply the limitations of the Nadal formula from the perspective of mechanism analysis;then,through the analysis of wheel-rail creep characteristics,an improved derailment limit in which the impact of angle of attack can be considered was derived by introducing the upper limit of a real-time effective friction coefficient,so as to obtain a new dynamic method of Nadal derailment evaluation;finally,the effectiveness of the improved derailment limit is verified by application examples.The comparison results show that the improved dynamic Nadal limit with the influence of the angle of attack of wheel-rail contact taken into account has less conservatism than the classical Nadal limit,hence scientifically and effectively reduce the misjudgment rate of derailment evaluation.At present,this limit is only verified from the theoretical level.In practical application,it is recommended to consider the safety factor margin for evaluation to ensure the safe operation of trains.