平稳高斯激励下线性结构随机振动分析的辅助简谐激励广义法
AUXILIARY HARMONIC EXCITATION GENERALIZED METHOD FOR RANDOM VIBRATION ANALYSIS OF LINEAR STRUCTURES UNDER STATIONARY GAUSSIAN EXCITATION
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摘要: 相比于时域法, 频域法是更为高效、易行的随机振动分析方法, 但对于平稳激励下的随机振动分析, 现有频域方法常需振型截断或功率谱矩阵分解, 将会影响计算精度和效率. 为此, 本文在频域法的框架下, 针对平稳高斯激励下线性结构的随机振动分析提出了一种精确且高效的辅助简谐激励广义法. 首先, 引入广义脉冲响应函数和广义频响函数的概念, 推导了与响应功率谱计算的完全二次项组合法等价的广义分析方法. 其次, 通过辅助简谐激励的响应乘积代替广义频响函数的乘积, 在广义分析方法的基础上进一步提出了更易于实现的辅助简谐激励广义法. 再次, 根据辅助简谐激励下结构响应求解方式的不同, 提出了具有不同适用性的两种辅助简谐激励广义法实现方案, 即基于振型叠加的辅助简谐激励广义法和基于时程分析的辅助简谐激励广义法; 同时, 给出了上述两种实现方案的计算性能及其与已有方法的对比分析. 最后, 通过两个算例验证本文所提方法的计算精度和效率. 由算例结果可知, 本文提出的辅助简谐激励广义法在计算响应功率谱时与完全二次项组合法和虚拟激励法的计算精度保持一致, 而计算效率相对完全二次项组合法和虚拟激励法具有显著的优势.Abstract: Compared with the time-domain method, the frequency-domain method is a more efficient and easy-to- implement method for random vibration analysis. However, the existing frequency-domain methods often involve truncation for degree of mode or decomposition of the power spectrum in multi-correlation conditions, which may have impact on the computational accuracy and efficiency of the methods. To this end, an accurate and efficient auxiliary harmonic excitation generalized method is proposed for the analysis of random vibration of linear structures under stationary Gaussian excitation in the framework of the frequency domain method. First, the concepts of generalized impulse response function and generalized frequency response function are introduced, and a generalized analysis method, which is equivalent to the complete quadratic combination method of response power spectrum calculation, is derived. Secondly, replacing the product of generalized frequency response function by the product of response of auxiliary harmonic excitation, a more easily implemented auxiliary harmonic excitation generalized method is further proposed based on generalized analysis method. Third, according to the different calculation methods of response for structure under the auxiliary harmonic excitation, two generalized methods of auxiliary harmonic excitation generalized method with different applicability are proposed, namely, the auxiliary harmonic excitation generalized method based on the mode superposition and the auxiliary harmonic excitation generalized method based on the time analysis. Meanwhile, the computational performance of the above two methods and their comparative analysis with the existing methods are introduced. Finally, the computational accuracy and efficiency of the proposed method are verified by two examples. The results of the examples show that the auxiliary harmonic excitation generalized method has significant advantages of the calculation efficiency over the complete quadratic combination method and the pseudo-excitation method with the same calculation accuracy.