L形工装常用来转接被试结构以实现不同方向的冲击试验。首先通过模态试验获取L形工装固定于振动台状态下的模态频率、模态振型及模态阻尼比,然后建立、修正L形工装有限元动力学模型。在此基础上,采用模态法对L形工装进行冲击响应谱试验的仿真模拟,并根据仿真结果与试验数据的差异对模态阻尼比作进一步的调整。从调整后模型冲击环境下的加速度响应计算值与试验值的对比结果来看:修正后的L形工装动力学模型可以正确预示冲击响应谱试验的响应。最后,通过对在不同位置安装有被试结构的L形工装进行冲击仿真分析,得到结论如下:为避免过试验或欠试验,保证被试结构所承受的冲击响应谱与试验条件一致,建议把控制点移到被试结构安装处。
L-shaped fixture is used to connect the structure under test to achieve different direction impact and vibration test. The modal frequency, modal shape and modal damping ratio of L-shaped fixture fixed to a vibrostand are obtained by a modal test, and then the finite element dynamic model of L-shaped fixture is established and corrected. On this basis, the shock response spectrum(SRS)test of the L-shaped fixture is simulated by modal method, and the further adjustment of the modal damping ratio is made according to the difference between the simulation result and the experimental data. It is found, by means of the comparison between the calculated values of accelerated response and the experimental values of the SRS test in the modified model impact environment, that the modified model can predict the response of the SRS test accurately. According to the impact simulation analysis of the L-shaped fixture installed in different positions, the conclusions were achieved as follows: it is recommended to move the control point to the subjects structure installation position to avoid over-test and under-test, ensure that the impact response spectrum of the subject structure is consistent with the test condition.
