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首页> 外文会议>2002 ASME International Mechanical Engineering Congress and Exposition , Nov 17-22, 2002, New Orleans, Louisiana >Fundamental Evaluation of Thermal Crack Resistance for Wheel Fracture Prevention
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Fundamental Evaluation of Thermal Crack Resistance for Wheel Fracture Prevention

机译：防止车轮断裂的抗热裂性的基本评估

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This paper presents a method for the thermal crack evaluation of railroad wheel materials and the results. The research investigated the basic thermal crack resistance as a low cycle fatigue behavior in terms of Δ ε_t-N_i and da/dN-ΔK. In order to be able to evaluate such material characteristics in service by experimentation, reproducible conditions such as similar stress-strain, temperature rise, and damage morphology are required. The methods proposed in the past for high temperature low cycle fatigue or thermal shock such as Coffin's and Manson's methods do not provide the above conditions at the same time for thermal cracks in railroad wheels. The material design to avoid such thermal damages has not yet been established. Therefore, a simple brake tester with a special device for measuring radial deflection converted into strain was designed and manufactured. The relations of Δ ε_t-N_i and da/dN-ΔK, which have not been clarified for thermal crack behavior in railroad wheels, were obtained for wheel materials by experiment using this new device. To predict the life of a wheel, one must know the real service conditions from field measurements. Once the histogram of the initial brake speed, intensity of brake application, and number of brakings from the initial speed is obtained, the histogram can be converted into the relation of strain range and number of cycles. The calculation of cycles for crack origination and propagation is possible based on the experimental results on Δ ε_t-N_i and da/dN-ΔK. From the material data of fracture toughness and possible residual stress value in the field, the critical crack length for wheel fracture can be then estimated, and the life from the cycles to the critical length is estimated. This method will provide the appropriate maintenance schedule to prevent wheel fracture.
机译：本文提出了一种评估车轮材料热裂纹的方法及其结果。该研究以Δε_t-N_i和da /dN-ΔK的形式研究了作为低循环疲劳行为的基本抗热裂性。为了能够通过实验评估使用中的这种材料特性，需要可重复的条件，例如类似的应力应变，温度升高和损坏形态。过去提出的用于高温低循环疲劳或热冲击的方法，例如科芬（Coffin）和曼森（Manson）的方法，不能同时提供上述条件来解决车轮的热裂纹。尚未建立避免这种热损伤的材料设计。因此，设计并制造了一种简单的制动测试仪，该制动测试仪带有用于测量转换为应变的径向挠度的专用装置。通过使用这种新装置的实验，获得了车轮材料的Δε_t-N_i和da /dN-ΔK的关系，这些关系尚未明确说明车轮的热裂纹行为。要预测车轮的使用寿命，必须从现场测量中了解实际的使用条件。一旦获得了初始制动速度，制动强度以及从初始速度开始的制动次数的直方图，就可以将直方图转换为应变范围与循环次数的关系。基于Δε_t-N_i和da /dN-ΔK的实验结果，可以计算裂纹产生和扩展的周期。根据断裂韧度的材料数据和现场可能的残余应力值，可以估算出车轮断裂的临界裂纹长度，并估算出从循环到临界长度的寿命。此方法将提供适当的维护计划，以防止车轮破裂。

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