Optimization of frame structure coach 29/34 seats in static durability state

The stress and deformation of the body frame and chassis frame of a coach subjected to bending, torsion, emergency braking and returning must be considered during the design and manufacture of passenger vehicles. The model of 29/34-seat coach in this investigation is a newly designed vehicle based on the old 29/34-seat coach; the most significant change has been to the chassis. It is vital to ensure it remains safe and durable when the vehicle operates on the road in the 4 cases mentioned above. Therefore, the purpose of this study is to optimise and maintain in a stable state the chassis structure of the 29/34-seat coach by using the Taguchi method based on grey relational analysis. This study has as design variables changes to the number of crossbars on the roof and the thickness of those bars, as the goal is to reduce vehicle weight while ensuring chassis durability. The finite element analysis applied the OptiStruct module of HyperMesh to analyse deformation and stress of the coach chassis. The optimal outcomes indicated that the error between predictive value and the optimal value of the grey relational grade of the proposed optimisation method and the regression analysis are 6% and 1.05%, respectively. The finite element analysis results indicated that when the design variables changed, the deformation and stress of the chassis changed significantly. The proposed optimisation method greatly reduced the deformation and stress of the vehicle. The optimal values of deformation and stress are also recorded in 4 cases: for the bending process 9.675 mm and 153.61 MPa were recorded; for the torsion process, 11.849 mm and 168.61 MPa; for the braking process, 10.569 mm and 161.66 MPa; for the rotation process, 16.162 mm and 200.5 MPa. The Taguchi method based on grey relational analysis helped to reduce vehicle weight by 11.5%. These results are comparable to previous publications.