Modal Analysis And Topology Optimization For The Cab Of Heavy Duty Commercial Vehicle

With the rapid development of China's economy, commercial vehicles have won increasingly wider range of applications. As heavy commercial vehicles travel for a long time, it is more prone to make the drivers fatigue on driving. And the much external excitation source easily led to the cab structure resonance on the travelling process, causing severe noise and vibration. So how to avoid the cab resonance with the excitation source and improve the cab's comfort is especially important.Using modal analysis techniques obtain the parameters of the dynamic characteristics of cab structure, we can evaluate that cab structure is reasonable whether or not from modal parameters. According to the problems of structure, it has great significances in engineering to improve the dynamic performance of the cab using the appropriate optimization method in time.Using topology optimization with manufacturing constraints under multiple loading cases research the conceptual model of heavy duty cab, we can not only find the optimized framework of the cab in a variety of dangerous driving conditions, but also allows to optimize the results of good manufacturing processes. Through research, we can accumulate of experiences for the development of similar model.Firstly , this paper introduced the basic theory of modal analysis, topology optimization and shape correlation. Those include normal mode theory, parameter identification theory, Topology optimization commonly used methods and mathematical. All of these provide a theoretical basis for the follow-up study.Secondly, we predigested the geometric model based on the principle of predigested finite element model, and established the finite element model of a cab with HyperMesh software. Through OptiStruct solver obtained the low order modal parameters, especially the modal frequency and modal shape in the frequency band of 0~50Hz. After calculation and analysis, the first torsion frequency of the cab was just 19.63 Hz, which was a little low compared to other cab. So it needed to adjust structure to enhance the first torsion frequency.Then, this paper dissertated the general steps of experimental modal analysis and components of test system, the support way of test target, vibrator and the choice of excitation signal, the layout of incentive points and response point, as well as the test of attention. Those prepared for experimental modal analysis. By the software LMS,test lab obtained modal parameters of actual Cab in the frequency band of 0~50 Hz ,and found the first torsion frequency of the cab was 20.67 Hz. Through analysis of numerical and experimental modal, frequencies and mode shape correlation, found the finite element model of the cab had a higher credibility of the conclusions that can be used for follow-up analysis. At last, we analyzed the possible reasons for errors.Based on the first torsion frequency of the cab slightly low, this study developed a double-layer shell element model. Through topology optimization methods, we identified the finite element model of the cab's specific region where needed thickening and thinning. It was proposed using high strength steel and aluminum alloy material to replace the original model, respectively, the need for thinning and thickening of the region.Finally this paper has established the topology optimization mathematical which based on the SIMP density-stiffness interpolation with multiple loading conditions and manufacturing constrains model. Five typical dangerous conditions in normal running were summarized, then conceptual model of the cab as technical vector, researched the topology optimization with manufacturing constraints under multiple loading cases. By comparing car-like model and optimize the results, the study has been verified the effectiveness of the method.According to the research of this paper, we can not only get the low orders modal parameters of the cab of heavy commercial vehicle, obtain the high-precision finite element mode which can be used for follow-up studying. But also accumulates experience of modal analysis and topology optimization for the cab of heavy commercial vehicle, this approach is also applicable for similar models.