加载频率对中温环境下疲劳裂纹扩展的影响

由于材料或环境的因素，加载频率对疲劳裂纹扩展速率将产生很大的影响，以工业Ｔｉ为对象，研究了中等温度环境下疲劳裂纹扩展性能及加载频率的影响，并用弹、粘塑性理论对其进行了理论上的探讨，基于该理论导出的本构关系和利用有限元方法，对裂纹尖端的应力应变进行了分析，结果表明，粘塑性应变范围和Ｊ积分范围可作为裂纹扩展的控制参数，能很好地反映加载频率对裂纹扩展的影响。

LOAD FREQUENCY EFFECT ON FATIGUE CRACK PROPAGATION IN TITANIUM AT ELEVATED TEMPERATURE

At elevated temperature, both cycle-dependeds and time-dependent aspects in fatigue crack propagation may be important. The present paper examines the influence of load frequency on crack growth rate in titanium at elevated temperature and attempts to analyze this effect theoretically. An elasto/visco-plastic theory is utilized to establish the constitutive equation of the material first. By using the finite element approach incorporating with the constitutive equation proposed, the viscoplastic strain and the J-illtegral are then evaluated and used to correlate crack growth rate under different load frequencies. It is found that these two parameters can account for the load frequency dependence very well in all the cases investigated.