用大质量法计算东风EQ140汽车前面罩的强迫运动响应

  目的  大质量法（LMM）可将设备机脚的激励加速度转化为力载荷，是结构振动响应与声辐射仿真分析的常用方法。为提高LMM在船体声振响应计算方面的应用精度，提出对LMM的修正。  方法  首先，分析LMM的适用原理，得出合理的大质量倍数区间; 然后，基于船舶的阻尼分析，引入瑞利阻尼质量比例系数对LMM加以修正; 最后，将修正前、后的LMM计算结果分别与某油船测试的数据进行对比，并基于修正大质量法（M-LMM）计算所得船体谐响应结果，进一步计算船舶水下辐射声功率与垂直声场指向。  结果  结果显示，在20~200 Hz分析频段内，应用2种LMM计算所得的振动响应频谱曲线趋势相近，但M-LMM的计算结果更接近于实测值，平均误差仅2.70%。  结论  M-LMM可提高船体响应仿真精度，能为船舶前期设计阶段提供更准确的设计依据。

Multiple-support seismic analysis of large structures

  Objectives  Large Mass Method (LMM) is capable to approximately convert excitation acceleration of equipments' seat into force loads, which is a common method for structural vibration response and acoustic radiation simulation analysis. In order to improve the accuracy of LMM applied in ship's noise & vibration response computation, a modified LMM(M-LMM)is presented.  Methods  Its application principles in hull structure response were analyzed, based on which the appropriate large mass ratio ensuring the application precision of LMM was obtained. Rayleigh damping was then taken into consideration, and LMM was modified with ratio coefficient. The experiment comparing results from original LMM as well as M-LMM with tested ones, together with the computations of underwater noise radiation power and vertical directivity pattern of sound field, were followed.  Results  For the frequency range of 20 Hz-200 Hz, the analysis results got from M-LMM were closer to measured values compared to that from LMM although their computed vibration response spectrums were roughly similar.  Conclusions  It is crystal clear that M-LMM can guarantee a simulation of main hull response with higher accuracy(average deviation 2.7%), providing the pre-design stage of vessels with more necessary information.