Research On The Optimization Design Of The Light Truck Cab Structure And Noise Performance

This paper mainly uses the finite element analysis method and structural optimization method to study the static,dynamic and acoustic characteristics of the cab's body-in white(BIW).On the one hand,the combination of topology optimization and size optimization improves the modal characteristics,bending and torsional stiffness of the cab.On the other hand,the addition of damping material reduces the noise in the cab,and the damping material is optimized for layout,saving material.First,the finite element model of BIW was established,and the accuracy of the model was verified through experiments.In the Optistruct software,the free modal,bending and torsional stiffness of the cab were analyzed,and the conclusion was drawn that the first-order modal frequency of the cab was low,the bending and torsional stiffness were insufficient.In order to improve the static and dynamic characteristics of the BIW,the topological optimization method was used to find the weak area of the cab structure,and the rigidity was improved by adding stiffeners.The optimization results verified the rationality of this scheme.The size of the newly added stiffener is then optimized so that the static and dynamic performance of the cab meets the requirements while the quality of the newly added stiffener is minimal.After topology optimization and size optimization,the first-order modal frequency of the cab was increased by 12.03%,bending stiffness was increased by 9.8%,torsional stiffness was increased by 17.4%,and the mass only increased by 1.7%.The structure-acoustic coupling finite model of the cab was established in Hypermesh software.The acoustic frequency response of the driver's right ear was analyzed before and after the structure optimization.The results showed that the previous structural optimization improved the static and dynamic performance of the BIW and also have a certain degree of noise reduction effect on the internal noise of the cab.By calculating the acoustic frequency response curve around the driver's ears,the main peak frequency is determined as the subsequent optimization target.The contribution of the panel,the modal contribution,and the grid contribution at the peak frequency point are calculated.These acoustic diagnosis methods are comprehensively used to determine the panels and local areas to be optimized.Damping material was used to improve the cab's acoustic performance.Firstly,the de-noising effect of free damping material and constrained damping material is analyzed.Then,using the damping material on the roof as an example,topology optimization of the free damping layer effectively reduces the sound pressure at a specific frequency,while the results show that the part of the retention of the damping material after topology optimization is basically the same as that of the larger contribution of the gride.Two methods were used to optimize the arrangement of damping materials.The method of the panel contribution combined with the modal strain energy has higher computational efficiency,but has limited effect on peak noise reduction.The method of gride contribution combined with topological optimization has obvious noise reduction on the cab's peak noise,and has a good noise reduction effect on the entire frequency,and the use of damping materials is less than the previous method,but the calculation efficiency is relatively slow..In short,the two damping methods have certain improvements in the acoustic performance of the cab and achieve the expected noise reduction effect,which has certain engineering significance.