• CN:11-2187/TH
  • ISSN:0577-6686

机械工程学报 ›› 2015, Vol. 51 ›› Issue (6): 45-50.doi: 10.3901/JME.2015.06.045

• 压力容器专栏 • 上一篇    下一篇


李煜佳 轩福贞 涂善东   

  1. 华东理工大学承压系统与安全教育部重点实验室 上海 200237
  • 出版日期:2015-03-20 发布日期:2015-03-20
  • 基金资助:

Influence of Stress Ratios and Residual Stress on the Fracture Pattern of Ti-6Al-4V Alloy in High Cycle Regime

LI Yujia XUAN Fuzhen TU Shantung   

  1. Key Laboratory of Pressure Systems and Safety, Ministry of Education, East China University of Science and Technology, Shanghai 200237
  • Online:2015-03-20 Published:2015-03-20

摘要: 对钛合金Ti-6Al-4V进行室温空气环境下的高周疲劳试验,研究消应力和未消应力试样在多个应力比下的疲劳强度,分析和检测表面残余应力在不同应力比和载荷水平下随循环次数而松弛情况,探讨表面残余应力随循环次数而松弛的规律以及残余应力和应力比对Ti-6Al-4V疲劳强度影响的机理。结果表明,随着应力比的提高,残余压应力对Ti-6Al-4V疲劳强度的提升影响逐步减小并消失;与消除残余应力后疲劳破坏源于表面相比,表面残余压应力使得低应力比下疲劳源于内部;当应力比R=1.0时,疲劳循环导致表面残余压应力松弛且保持稳定,其产生的表面裂纹闭合是疲劳强度提高的主要机制;当R=0.6~0.1时,未见疲劳循环导致表面残余应力松弛,由于表面层的平均应力减小使得疲劳破坏主要为内部缺陷和局部应力集中控制。

关键词: Ti-6Al-4V, 残余应力, 高周疲劳, 应力比

Abstract: Experiments are conducted on the high cycle fatigue behavior of Ti-6Al-4V in air at room temperature. Fatigue strengths are determined at various stress ratios for specimens prepared by hard turning plus polishing and residual stress relieved in vacuum after polishing. For various stress ratios and stress amplitudes investigated, the relaxation of residual stresses is measured during the interrupted fatigue test. The relationship of residual stresses relaxation with the cycles and the effects of residual stress as long as stress ratios on fatigue strength are analyzed. Results indicate that the improvement of residual compressive stress on fatigue strength decreases and vanishes finally with the increase of stress ratio. Compared to fatigue crack originating from surface for annealed specimens, the fatigue crack initiation sites are located in the interior of the specimen due to the effect of residual stress at lower stress ratios. At R=1.0, the residual stresses are relaxed after several cycles and then maintained stable. The improvement of fatigue strength is attributed to surface crack closure induced by compressive residual stress. For R=0.6-0.1, in contrast, the relaxation of residual stress is insignificant and fatigue failure is dominated mainly by the internal defect and local stress concentration.

Key words: high cycle fatigue, residual stress, stress ratio, Ti-6Al-4V