应力比和残余应力对Ti-6Al-4V高周疲劳断裂模式的影响

发布时间：2018-08-03 08:02

【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。
[Abstract]:The high cycle fatigue tests of titanium alloy Ti-6Al-4V were carried out at room temperature and air conditions. The fatigue strength of stress dissipation and unstress relief specimens at multiple stress ratios was studied. The relaxation of surface residual stress with the number of cycles under different stress ratios and load levels is analyzed and measured. The relaxation of surface residual stress with the number of cycles and the mechanism of the influence of residual stress and stress ratio on fatigue strength of Ti-6Al-4V are discussed. The results show that the effect of residual compressive stress on the fatigue strength of Ti-6Al-4V decreases and disappears with the increase of stress ratio, and the fatigue failure originates from the surface when the residual stress is eliminated. Surface residual compressive stress causes fatigue to originate from inside at low stress ratio, fatigue cycle results in relaxation and stability of surface residual compressive stress when stress ratio is R ~ (-1.0), and surface crack closure is the main mechanism to increase fatigue strength. No fatigue cycle resulted in surface residual stress relaxation, and the fatigue failure was mainly controlled by internal defects and local stress concentration due to the decrease of the average stress of the surface layer.
【作者单位】：华东理工大学承压系统与安全教育部重点实验室;
【基金】：国家自然科学基金资助项目(51325504)
【分类号】：TG146.23

【共引文献】