多目标拓扑优化的低响度正时罩设计

Design of low loudness timing cover based on multi-objective topology optimization

为了改善正时罩的声品质性能,建立正时罩的有限元模型.提取连接螺栓处在整机多体动力学计算中的振动位移,并作为正时罩频率响应的激励施加于正时罩螺栓孔.对比正时罩测点的振动加速度级的仿真值与测试值,发现两者在趋势及幅值上较吻合,验证了频率响应的准确性.建立正时罩边界元模型,并将频率响应计算结果作为声学边界元的边界条件预测辐射噪声.采用表面振动速度测试值计算辐射噪声声功率,并验证声学预测的准确性.依据Moore响度模型编写响度计算程序,并计算出正时罩辐射噪声响度.确定响度贡献较大的几阶约束模态,通过多目标拓扑优化布置加强筋,以提高刚度使模态频率与激励峰值频率分离,最终降低正时罩辐射噪声响度.仿真结果表明:正时罩辐射噪声响度由49.8sone降到46.5sone,降幅达6.7%,人主观可以感受到噪声舒适性得到改善;辐射噪声声功率级总值由84.7dB降低到83.8dB,降低0.9dB.

The finite element model was established,in order to improve sound quality performance of timing cover.The vibration displacement got from multi-body dynamics simulation of the connecting bolts were loaded on bolt holes to calculate the frequency response of timing cover.Simulation values and test values of vibration acceleration level of test node on timing cover were compared,which agreed in trend and amplitude,thus the accuracy of the frequency response analysis was verified.The boundary element model of timing cover was established,and the results from the frequency response analysis were regarded as boundary conditions to predict the radiation noise.The radiated noise power was calculated with the method of surface vibration velocity,and the accuracy of acoustic prediction was verified.The loudness simulation program was written based on the Moore loudness model,and the radiated noise loudness of timing cover was calculated.A few orders of constraint modes which made main contribution to loudness were identified,then stiffeners were placed by multi-objective topology optimization method,in order to enhance the stiffness to separate modal frequencies with excitation peak frequencies.The results reveal that radiated noise loudness of timing cover decreases by 6.7% from 49.8sone to 46.5sone,therefore,the comfort of radiation noise is improved obviously.The sound power level of radiated noise decreases by 0.9dB from 84.7dB to 83.8dB.