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试验平台采用德国Polytec激光测振仪及电动振动台搭建,试验样品共有一件,外形为长方体,长×宽×高=310 mm×82 mm×180 mm,重约7.1 kg,底部3个M8螺栓固定,见图3。通过铝合金材料制作的过渡板固定在电动振动台上。利用振动台进行激振,结合模态仿真结果确定激振方向为样品的侧向,即图中标示(红色箭头)方向。测点布置共194个测点,测试过程中激光器处于关机状态。
此次试验分析带宽为2 kHz,谱线数为6400,频率分辨率为0.31 Hz。过滤低频噪声影响,试验的有效分析带宽为100~2 000 Hz。试验测试过程见图4,激光测振仪的某测点测试结果如图5所示。
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试验测得各点频域振动速度信号,由PSV软件计算得到各测点相对于参考点的传递函数,并导出传递函数数据。利用LMS模态分析软件PolyMAX方法识别固有频率和振型。频响函数曲线及稳定图如图6所示,可见有4阶固有频率,振型的模态置信因子矩阵如图7所示,表明各振型相互正交,通过固有频率与振型拟合出理想的频响函数,与实测频响函数对比进一步验证结果。
此次试验测得2 000 Hz以内样品的四阶振型、固有频率与2.2小节中的仿真结果进行对比,见表1,可以看出,试验与仿真计算振型描述一致,固有频率误差较小(8%以内),从而验证了仿真模型的正确性,为进一步开展谐响应仿真分析奠定了基础,图8给出了试验与仿真分析的第一阶振型对比云图。
Order Natural frequency/Hz(Simulation) Natural frequency/Hz(Test) Mode description(Simulation,Test) 1 178.236 166.142 Top core area asymmetric side swing 2 567.278 480.670 Top core area side twist 3 932.786 873.262 Front second-order asymmetric side swing 4 1504.8 1473.912 Front heat dissipation area side swing Table 1. Natural frequency and vibration mode
Vibration reliability of mid-infrared solid laser
doi: 10.3788/IRLA20200242
- Received Date: 2020-11-17
- Rev Recd Date: 2020-12-23
- Available Online: 2021-05-12
- Publish Date: 2021-04-30
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Key words:
- vibration reliability /
- mid-infrared solid laser /
- non-contact vibration measurement technique /
- optical crystal assembly /
- simulation
Abstract: Based on ANSYS, finite element simulation calculation model of mid-infrared solid laser was established, and modal parameters, such as natural frequency and vibration mode were gained through modal analysis. Combined with non-contact vibration measurement technology, the vibration modal test platform was set up, and the reliability of the modal simulation model was verified by the comparison with the test. Then, on the basis of modal simulation, the vibration characteristics of laser optical crystal assembly was studied emphasisly under condition of sinusoidal frequency sweeping vibration of vehicle through response analysis, and equivalent stress, total mechanical strain, relation between displacement and excitation frequency can also be obtained. Last, the key positions that affecting the vibration reliability of laser were analyzed and the results provide useful reference for improving design. The results indicate that there are four natural frequencies and modes in middle infrared solid laser using bottom fixed constraint, within 2 000 Hz and the experimental results of the modal agree with simulation results, and the natural frequency error is less than 8%. The maximum total mechanical strain and equivalent stress appeared at the edge of the input mirror under the condition of vehicle frequency sweeping vibration. The axial displacement along the optical crystal assembly is the largest and its value is about 0.14 mm.