火箭推进

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雨流计数,获得了用于裂纹扩展计算的应力循环谱块,研究了疲劳试验的应变循环峰值、幅值等时域分布特征; 采用Newman闭合理论对长裂纹的NASGRO裂纹扩展速率曲线进行修正,给出了试验件材料的相关参数; 最后,使用一种疲劳应力谱块平均施加方法进行了裂纹扩展寿命的快速计算。通过与试验结果对比,验证了计算方法有效、可靠。

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.

引言
1 试验简介
2 裂纹扩展分析
3 结论

图1 试验件结构形式<br/>Fig.1 Geometric structure of test specimen

图1 试验件结构形式
Fig.1 Geometric structure of test specimen

图2 疲劳试验考核部位<br/>Fig.2 Assessment site in fatigue test

图2 疲劳试验考核部位
Fig.2 Assessment site in fatigue test

图3 试验件典型开裂模式<br/>Fig.3 Typical cracking mode of test specimen

图3 试验件典型开裂模式
Fig.3 Typical cracking mode of test specimen

表1 试验结果
Tab.1 Test results

图4 裂纹几何模型<br/>Fig.4 Geometric model of crack

图4 裂纹几何模型
Fig.4 Geometric model of crack

图5 有限元模型
Fig.5 Finite element model

图6 表面裂纹前缘的应力强度因子<br/>Fig.6 Stress intensity factor at the front edge of surface crack

图6 表面裂纹前缘的应力强度因子
Fig.6 Stress intensity factor at the front edge of surface crack

图7 应力强度因子随裂纹长度的变化曲线<br/>Fig.7 Stress intensity factor with crack length

图7 应力强度因子随裂纹长度的变化曲线
Fig.7 Stress intensity factor with crack length

图8 应变循环均值与幅值分布图<br/>Fig.8 Mean value and amplitude distribution of strain cycle

图8 应变循环均值与幅值分布图
Fig.8 Mean value and amplitude distribution of strain cycle

图9 应变循环峰值发生频次<br/>Fig.9 Occurrence number of strain cycle peak

图9 应变循环峰值发生频次
Fig.9 Occurrence number of strain cycle peak

图10 应变循环幅值发生频次<br/>Fig.10 Occurrence number of strain cycle amplitude

图10 应变循环幅值发生频次
Fig.10 Occurrence number of strain cycle amplitude

图11 小裂纹及长裂纹扩展行为[19]<br/>Fig.11 Growth behavior of small crack and long crack[19]

图11 小裂纹及长裂纹扩展行为[19]
Fig.11 Growth behavior of small crack and long crack[19]

表2 裂纹扩展速率参数<br/>Tab.2 Parameters of NASGRO crack growth rate

表2 裂纹扩展速率参数
Tab.2 Parameters of NASGRO crack growth rate

图12 裂纹扩展计算流程<br/>Fig.12 Calculation process of crack growth

图12 裂纹扩展计算流程
Fig.12 Calculation process of crack growth

表3 裂纹扩展寿命计算结果<br/>Tab.3 Calculation results of crack growth

表3 裂纹扩展寿命计算结果
Tab.3 Calculation results of crack growth

图13 裂纹扩展长度随时间的变化<br/>Fig.13 Crack growth length with time

图13 裂纹扩展长度随时间的变化
Fig.13 Crack growth length with time

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备注

引言

1 试验简介

2 裂纹扩展分析

3 结论

期刊信息