载荷波形对新型钛合金疲劳裂纹扩展行为影响研究

Research on the effect of load waveform on dwell-fatigue crack growth behavior of a new type of titanium alloy

深海载人潜水器作业过程中,耐压壳结构承受下潜(载荷增加)、巡航(上峰值保载)、上浮(载荷降低)、休整阶段(下峰值保载)和再次下潜的循环载荷作用。因此,针对潜水器用钛合金材料开展了疲劳、上峰值保载-疲劳(巡航)和上-下峰值保载-疲劳(巡航-休整)裂纹扩展速率试验研究。试验结果表明,钛合金上峰值保载-疲劳裂纹扩展速率高于疲劳裂纹扩展速率,并随着上峰保载时间的增加,上峰值保载-疲劳裂纹扩展速率越高;随着下峰值保载时间的引入,使得上-下峰值保载-疲劳裂纹扩展速率明显高于上峰值保载-疲劳裂纹扩展速率,并且裂纹扩展速率随着下峰值保载时间的增加而不断加快。

During the service of deep-ocean manned submersible,the pressure shell in each operation bears loads as follows:diving stage(load increase),cruising state(upper peak load holding),floating stage(load decrease),rest stage(lower peak load holding).Therefore,this paper carried out the experimental study on the influence of upper peak load holding(cruising state)and upper-lower peak load holding(cruise-rest state)on the fatigue crack growth tests of new titanium alloy.The results show that the dwell-fatigue crack growth life under upper peak load holding is faster than the fatigue crack growth life,and the dwell-fatigue crack growth life of under upper-lower peak load holding is faster than the dwell-fatigue crack growth life under upper peak load holding.With the increase of the lower peak load holding time,the dwell-fatigue crack growth rate also increases.