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<p>During high-speed train operation, brake disks are subjected to severe thermal cyclic loads, and surface scratch defects markedly alter their thermo-mechanical response and fatigue behavior. In this study, a 24CrNiMo cast-steel brake disk was selected as the research object, and a three-dimensional thermo-mechanical coupled finite element model containing scratch defects was established to investigate the evolution of temperature and stress fields during braking. The results demonstrated that scratch defects induced pronounced local stress concentration, resulting in significantly higher residual stress after braking compared with defect-free disks, with the maximum residual stress reaching up to 1.9&#xa0;times greater. Furthermore, the extended finite element method (XFEM) was employed to simulate crack initiation and propagation, while the Paris law was used to predict the residual service life. The findings revealed that under emergency braking at 300&#xa0;km/h, the crack growth rate of scratched disks was considerably higher than under conventional braking, and the rate increased with larger crack aspect ratios (<i>a/c</i>). Life prediction results indicated that the residual life of scratched disks under emergency braking was approximately 2.1 × 10<sup>4</sup>–2.9 × 10<sup>4</sup> cycles, substantially lower than the 4.6 × 10<sup>4</sup>–8.3 × 10<sup>4</sup> cycles observed under conventional braking. Once the crack length exceeded 30&#xa0;mm, the growth rate accelerated sharply, and the residual life decreased to less than 10% of the total life, which can be regarded as the critical damage size. These results elucidate the influence of scratch defects on the thermal fatigue behavior and residual life of high-speed train brake disks, providing a theoretical basis for damage-tolerance design, life prediction, and maintenance strategies.</p>

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Thermal Stress Field Analysis and Residual Life Prediction of High-Speed Train Brake Disks with Scratch Defects

  • 期刊论文

  • 发表日期：

    2026年4月27日

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  • Hui Zhao,
  • Mingkang Zhang

摘要

During high-speed train operation, brake disks are subjected to severe thermal cyclic loads, and surface scratch defects markedly alter their thermo-mechanical response and fatigue behavior. In this study, a 24CrNiMo cast-steel brake disk was selected as the research object, and a three-dimensional thermo-mechanical coupled finite element model containing scratch defects was established to investigate the evolution of temperature and stress fields during braking. The results demonstrated that scratch defects induced pronounced local stress concentration, resulting in significantly higher residual stress after braking compared with defect-free disks, with the maximum residual stress reaching up to 1.9 times greater. Furthermore, the extended finite element method (XFEM) was employed to simulate crack initiation and propagation, while the Paris law was used to predict the residual service life. The findings revealed that under emergency braking at 300 km/h, the crack growth rate of scratched disks was considerably higher than under conventional braking, and the rate increased with larger crack aspect ratios (a/c). Life prediction results indicated that the residual life of scratched disks under emergency braking was approximately 2.1 × 104–2.9 × 104 cycles, substantially lower than the 4.6 × 104–8.3 × 104 cycles observed under conventional braking. Once the crack length exceeded 30 mm, the growth rate accelerated sharply, and the residual life decreased to less than 10% of the total life, which can be regarded as the critical damage size. These results elucidate the influence of scratch defects on the thermal fatigue behavior and residual life of high-speed train brake disks, providing a theoretical basis for damage-tolerance design, life prediction, and maintenance strategies.