Structural Safety Analysis And Optimization Of A Semi-integral School Bus

For school bus body skeleton structure statics insufficient strength, stiffness and low structural strength of the upper body structure security issues, according to China’s "special school bus safety and technical conditions", using the finite element method to analyze static characteristics, vibration characteristics and crash safety of school bus body skeleton. And based on static mechanical properties and crash safety to research on school bus body skeleton structure optimization method.First, taking a medium-sized semi-integral school bus as object, the basic static strength, stiffness and the free modal vibration mode was studied, as well as the relationship between these characteristics.Then, the 3D model of the semi-integral body bus frame was designed. Based on which, the shell unit finite model was established by the help of the software Hypermesh. In order to verify the finite element model, the statics strength experiment system was designed based on mechanical electrical measuring technology. And the established school bus body skeleton finite element model was verified the correctly and reliably by analyzing the experimental data. Based on this, bending stiffness and torsional stiffness of the semi-integral school bus body skeleton under symmetrical vertical load and antisymmetric vertical load was discussed. Also the Mises stress and strain distribution was analyzed under five classic conditions such as full loaded uniform linear driving condition and full loaded single round obstacle condition et al. Secondly, based on the school bus crash safety the LS-DYNA explicit nonlinear finite element algorithm was studied. Then, finite element simulations were designed to simulate the structural strength of the school board and the top portion of the bus frame. And based on "special school bus safety and technical conditions", the school bus crash safety was evaluated.At last, for its statics problem of insufficient strength, bending stiffness and low torsional stiffness values, as well as the strength of the upper structure does not meet the regulatory requirements, optimization design method based on semi-integral school bus body skeleton statics and crash safety features was researched. Which taken the maximization of the bus frame’s stiffness as the objective function, and the maximization of tress as the constraint, optimized the carling and crossgirder of the chassis frame. Using the Optistruct optimization algorithm of mathematical programming method to calculate the optimization problem. In the end, comparative analysis of the optimization of the bending and torsional stiffness, the strength in full uniform linear driving conditions and full loaded single round obstacle conditions, and further analysis of the rollover collision process were processed.