利用阻尼材料改善驾驶室声学特性的研究

Research on Improvement of Cab Acoustic Characteristics Using Damping Material

为改善某款商用车驾驶室声学特性,建立该驾驶室的声固耦合有限元模型,通过频率响应分析,得到车内的声学响应。对81 Hz处声压峰值进行声学结构模态参与因子分析和板件贡献分析。对贡献最大的板件进行自由阻尼处理。为减少阻尼材料使用量,将阻尼材料体积作为约束条件,阻尼材料单元相对密度作为设计变量,以贡献最大的结构模态所对应的模态阻尼比最大化为优化目标,基于优化准则算法用MSC.Nastran的直接矩阵提取程序(Direct matrix abstraction program,DMAP)语言编制拓扑优化程序,对阻尼材料在驾驶室上的分布进行优化。优化后阻尼材料的体积减小40%,目标模态的模态阻尼比降低5.2%。根据优化结果粘贴阻尼材料,使驾驶员右耳处声压和乘员右耳处声压在81 Hz附近分别降低11.2 dBA和10.7 dBA,其他峰值处声压变化不大。

In order to improve cab acoustic characteristics, the structure-acoustic coupling finite element model of the cab is established at first. Frequency response analysis is then performed to get the interior acoustic response. The acoustic structural modal participation factors and panel acoustic contributions for peak sound pressure at 81 Hz are computed to find structural modals and panels that have most influence on the acoustic response of vehicle, Those panels are treated with damping material. In order to find the optimum distribution of damping material and reduce its consumption, the topology optimization program based on optimization criteria algorithm is written using direct matrix abstraction program（DMAP） language, with maximum modal damping ratio of cab as goal, damping material volume as restriction and densities of damping cell as design variables. After optimization, the volume of damping material is down to 60%, while the modal damping ratio is lowered to 94.8%. According to the optimization result, damping material is added to the cab. The pressure near driver＇s right ear and passenger＇s right ear at 81 Hz is reduced 11.2 dBA and 10.7 dBA. Other peak sound pressure changes little.