约束态薄壁圆柱壳固有频率的精确测试

Accurate Test of Natural Frequency of Constrained Thin Cylindrical Shell

采用传递矩阵法和有限元法对约束态圆柱壳固有特性进行计算以明确振动特点;详细分析了约束态圆柱壳固有频率测试的影响因素,并提出通过力矩扳手定量确定边界约束条件、合理选择激励信号类型、采用加窗和多次平均处理等解决措施.最后,搭建了4种不同激励形式(锤击、电磁激振器、压电陶瓷、振动台激振)的测试系统对其固有频率进行了试验研究,提出了约束态下薄壁圆柱壳固有频率的测试流程.研究表明:振动台基础激励方法对约束态薄壁圆柱壳没有任何附加质量和刚度的影响,测试状态即为圆柱壳真实的受力状态.使用该激励方法并配合激光测振仪进行固有频率测试的精度最高.

For better understanding its vibration behavior,inherent characteristics of constrained thin cylindrical shell w ere calculated by transfer matrix method and FE method,respectively.Factors affecting high-precision test of natural frequency and their solutions w ere analyzed.The methods of using the torque w rench to quantitatively determine the constraint boundary conditions and adopting reasonable excitation signal,additional w indow and average processing w ere chosen to improve the test accuracy.Furthermore,four types of excitation experimental systems including hammer,electromagnetic exciter,piezoelectric ceramic exciter and vibration shaker w ere set up to measure natural frequencies and key test steps w ere exhibited.The results show that base excitation produced by vibration shaker does not bring any additional mass and stiffness to thin cylindrical shell and is in good accord w ith its real stress-constraint state.Thus,the combination of vibration shaker for excitation source and laser Doppler vibrometer for response test has the highest test accuracy of natural frequencies.