Protection Mechanism And Multidisciplinary Optimization Of Vehicle Body Structure Under Blast Shock

The design crashworthiness and blast resistance of special purpose vehicle,including military vehicles,police special vehicles and security vehicles,are becoming more important.It is always been the research focuses for improving the blast resistant performance of vehicle,meanwhile reducing the occupant injuries,by integrated vehicle blast simulation,blast test with multidisciplinary optimization.Focused on this key issue,the dynamic response,protection mechanism and multidisciplinary optimization for the design of blast-resistant vehicle body were mainly studied,which involve Finite Element,Mechanics of Explosion,Fluid Structure Interaction,Impact Dynamics,Biomechanics,and Multivariate Statistics.Furthermore,some key scientific problems such as vehicle body buckling instability and dynamical mechanical properties under blast shock,the data switching and computational complexity in the process of vehicle body multidisciplinary optimization need to be considered.In order to overcome these computational difficulties,the blast simulation algorithm based on ALE-FSI is studied to confirm the complex coupled boundary condition between blast shock wave and vehicle underbelly,and the responses of vehicle structure and occupant injuries under blast chock are validated by physical tests.Then,the protective mechanism of vehicle body,v-shaped kits and honeycomb multilayer sandwich kits are studied by employed parameter sensitivity analysis.Finally,the computational accuracy and efficiency by different multidisciplinary optimization methodology are discussed,and The Pareto sets of different vehicle model are calculated by the proposed methodology,which could get the design scheme of vehicle underbody.The main works and creative results can be drawn from this study:(1)Explosion source model,shock wave propagation model and fluid structure interaction model are studied to build the Arbitrary Lagrangian Eulerian-Fluid Structure Interaction(ALE-FSI)methodology which could predict the propagation of shock wave and stress wave in vehicle body precisely.The dynamic response of constrained square plate is studied by employed the proposed methodology,the strain rate range of the constrained plate and the sensitivity simulation parameter are revealed.(2)The CAE modeling method for modular vehicle body and its connection structure are studied,and the reliability of white vehicle body FE models is verified through modal experiment.Meanwhile,the Johnson-Cook material model for vehicle body,which makes the blast simulation more precise,is built by the quasi-tensile tests,Hopkinson bar tests,notch tension tests and various temperatures tensile tests.The simulation of vehicle response under blast shock presents the complex transmission path of shock wave among vehicle body,shock-mitigating seat and occupant.(3)Error Assessment of Response Time Histories is hired to validate the vehicle dynamic responses of simulation models,which are measured from physical tests.A framework program for automatic validating the blast simulation model is built,and in the framework program,Dynamic Time Warping is used to evaluate the amplitude error,cross-correlation function is used to evaluate the phase error,Slope Deviation is used to evaluate the shape error,and the sensitivity simulation parameters,including penalty factor for coupling,number of coupling points,time step and elment size,are regarded as design variables to minimize the error between simulation responses and physical tests.The effects of simulation deviation by simulation parameters have been revealed,and the leakage phenomenon is controlled and the accuracy of simulation models is increased significantly by using the framework program.The amplitude error is reduced by 15.8%,the phase error is reduced by 56.6%,and the shape error is reduced by 69.5%.(4)An evaluate methodology for the vehicle buckling stability is built,and the analytical hypotheses,restrict and boundary condition are defined clearly.The performance of blast resistance for vehicle stability is improved,the local instability phenomenon is avoided to ensure occupant safety.The buckling stability effect of vehicle body suspension position,the clearance and offset effect of v-shaped kits and face-sheet material,compression direction and shape effect of honeycomb multilayer sandwich kits are studied by using ALE-FSI methology,which could explain the protective mechanism and provide the theoretic support for the design of blast resistant vehicle.(5)The difficulty in the data switching and multi-object is solved by using approximation technique with non-layer structure strategy and Pareto Optimality theory.Similarly,multilevel structure is hired as the optimization strategy,Factor Analysis and approximation technique are used to build the dimension reduction based multidisciplinary optimization method.FAMO is applied to deal with the computational difficulties in the design process of blast-resistant vehicle.Finally,based on the conclusions above,the blast resistant performance of vehicle body is improving significate by using the design scheme,which offers a reference for design and develop of the special purpose vehicle.