随机振动疲劳试验的小裂纹扩展分析方法

针对某型液体火箭发动机管路接头的随机振动疲劳试验,基于断裂力学的小裂纹理论进行了裂纹扩展寿命分析.分别从小裂纹应力强度因子计算、疲劳应变/应力谱、裂纹扩展速率曲线以及裂纹扩展计算程序等方面进行了研究.使用FRANC3D(试用版)进行三维裂纹的有限元计算,得到了管路结构表面裂纹的应力强度因子变化规律;对应变实测数据进行了...

Study on analysis method of small crack growth in random vibration fatigue test

According to the random vibration fatigue test of the pipeline joint in a liquid rocket engine,the crack propagation analysis was carried out based on the small fatigue crack theory of fracture mechanics.The calculation of small crack stress intensity factor,fatigue strain/stress spectrum,crack growth rate curve and crack growth calculation program were studied,respectively.FRANC3D(trial version)was used to perform the finite element calculation of three-dimensional crack,and the variation law of stress intensity factor on the surface crack of pipeline structure was obtained.Rain-flow cycle counting method was used to count the measured strain date,and the stress cycle spectrum block for crack growth calculation was formed.Then,time-domain distribution characteristics of the cyclic strain peak and amplitude in fatigue test were studied.Newman crack closure theory was used to modify the NASGRO crack growth rate curve of long cracks,and the relevant parameters of the test sample material were given.Finally,an average loading method of fatigue stress spectrum block was used to quickly calculate the crack growth life.Compared with the experimental results,the calculation method is effective and reliable.