| As an indispensable means of transportation in every city,the safety of city bus collision is closely related to the lives of passengers and drivers.Considering that frontal collision is the most common accident in all collision accidents,it is of great significance to improve the safety of city bus body in frontal collision to protect drivers and passengers.In this paper,a 12-meters long city bus is taken as the research object,and the simulation analysis and optimization of the car’s frontal collision are carried out to improve the safety of the city bus’ s frontal collision.Firstly,the finite element model of city bus body is established and the dynamic performance is analyzed.The three-dimensional model of city bus is established according to the drawings,and the finite element model of city bus body is built by Hypermesh software.The free mode analysis is carried out on the established finite element model,and the rationality of the model and the vibration characteristics of the body are investigated through the analysis results.Secondly,the collision model is built and simulated.Based on the finite element model,the collision model is obtained by adding load,boundary condition,contact,initial condition,Ls-Dyna software was used to simulate the collision of the model.The analysis results show that the calculation results of the whole collision process are reliable,the deformation is reasonable,the added speed value in the collision process is 100.072 g,and the body intrusion index value is 449.042 mm.The calculated values of each index can provide a reference for the subsequent optimization of the collision safety of city buses.Thirdly,according to the axial crushing theory of the thin-walled beam and the force transmission path of the bottom skeleton,the peak value of the longitudinal reaction force of the front-end beam is obtained.After referring to the remaining design space of the front,six square-section energy-absorbing structures are designed and installed in the front of the front-end beam.The simulation results show that the energy absorption structure absorbs 28.07 k J of energy and reduces the value of collision acceleration by 8.6%,which effectively improves the collision safety of city bus body.Fourthly,according to the energy absorption and deformation of each component after collision,7 optimization components are selected for optimization.The samples of the selected components were collected for the optimal Latin hypercube design.After the collected samples were calculated and counted,the response surface model was established according to each evaluation index and condition,and the accuracy of the response surface model was verified.Finally,the NSGA-II optimization algorithm is used to solve the problem under the constraint condition that the total mass of the optimized parts of city bus body does not increase and the evaluation index of acceleration and intrusion is the minimum as the objective function.The theoretical optimal solution is structured and then calculated again.The results show that the collision acceleration decreases by 10.6% and the invasion distance by 5.5% without the increase of mass.It can be seen that each evaluation index has been improved to varying degrees,effectively enhancing the safety of city bus body in frontal collision. |
