残余应力对GH3230层板焊缝热疲劳寿命影响规律研究

Study on Influence Rules of Residual Stress on Thermal Fatigue Life of GH3230 Laminate Welds

为了探究残余应力对层板冷却结构焊缝服役寿命的影响规律,首先对GH3230层板在常规条件下的激光焊接过程进行有限元模拟与实验验证,然后在此基础上对预拉伸、温差拉伸等焊接残余应力调控方法开展模拟。基于焊后残余应力模拟结果研究了层板服役过程的温度及等效应力变化规律,并将多个模型之间不同残余应力下服役状态进行对比分析,最后利用Morrow修正的Coffin-Manson方程对焊缝后续服役寿命进行评估。研究结果表明,焊接残余应力的存在大幅降低了层板结构焊缝区域热疲劳寿命,通过残余应力调控技术可有效改善焊缝区域服役过程中的应力幅或平均应力,使其分别下降70%与25%,焊接残余应力调控对提高层板结构热疲劳寿命具有重要意义。

In order to investigate the influences of residual stress on the service life of weld seams of laminate cooling structures,first of all,finite element simulation and experimental verification were carried out on the laser welding processes of GH3230 laminate under conventional conditions.Then corresponding regulated approaches including pre-stretching and thermotensile et al.were simulated and analyzed.Afterwards,the evolutions of temperature and equivalent stress during service periods with and without residual stress were studied respectively.The service life was later evaluated using Coffin-Manson model modified by Morrow.The results demonstrate the thermal fatigue life caused by residual stress is significantly decreased.Furthermore,the stress amplitude and the mean stress while servicing,which decreasing 70%and 25%respectively,are effectively improved using regulating approaches mentioned above.Regulating welding residual stress is of vital importance for improving the thermal fatigue life of laminate structures.