钛合金室温与低温疲劳裂纹扩展速率试验研究

Research on fatigue crack growth rate of titanium alloy at room temperature and low temperature

为了明确极地破冰船关键部位钛合金的疲劳裂纹扩展行为,本文以89 mm厚钛合金为试验对象,完成室温以及低温下的疲劳裂纹扩展速率试验。从钛合金的a-N曲线表明随着温度的降低,钛合金的寿命增加;对a-N曲线进行数据处理得到疲劳裂纹扩展速率的双对数曲线。结果表明:在一定应力强度因子内,随着温度的降低,疲劳裂纹扩展速率降低;在-60℃时,断裂韧性降低,在一定应力强度因子以外,裂纹扩展速率提高;在极地正常温度内,可以确定钛合金满足极地低温疲劳裂纹扩展速率要求,但是在-60℃以下的一些极端极地气温下,防止脆性破坏成为疲劳设计的重点;试验数据能为极地破冰船进一步抵抗低温疲劳和冷脆断裂设计提供参考;采用采用所提出的预报公式对钛合金疲劳裂纹扩展速率的中速率区和高速率区进行预报,预报结果显示该预报公式能较好的预报该钛合金的低温疲劳裂纹扩展速率的2个区域。

In order to clarify the fatigue crack growth behavior of the titanium alloy in the key parts of the polar icebreaker,a 89 mm thick titaniumn allay was used as the experimental abject to complete the fatigue crack growth rate experiment at room temperature and low temperature.The a-N curve of the tianium alloy shows that the life of the titanium alloy increases with the decrease of temperature;the data processing of the a-N curve results in a double logarithmic curve of the fatigue crack growth rate.The results show that within a certain stress intensity factor,the fatigue crack growth rate decreases with the decrease of temperature;at-60℃,the fracture toughness decreases,and the crack growth rate increases beyond a certain stress intensity factor;in the polar normal temperature,It can be determined that the titanium alloy meets the requirements of the ulra-low temperature fatigue crack growth rate,but at some extreme polar temperatures below-60℃,preventing brittle failure becomes the focus of fatigue design;the test data can further resist low temperature fatigue and cold brittle fracture for polar icebreakers.Design provides a reference.The fatigue crack growth rate of titanium alloy was predicted by using the prediction formula,The prediction results show that the formula can predict the crack propagation rate well.