Reliability Analysis Of Local Surface Nanocrystallization Energy-absorbing Thin-walled Square Tube

With the rapid development of infrastructure construction and rail transit industry in China,vehicle collision accidents occur frequently.Therefore,there is great demand to improve the safety of vehicles.Due to effectively improving the energy absorption capacity of vehicle structure is one of the measures to improve safety performance,many scholars have been devoted to the research of energy-absorbing structures and devices.The surface nanocrystallization thin-walled square tube can greatly improve its mechanical properties and achieve better energy absorption effect.However,because there are some uncertain factors in the process of surface nanocrystalline,so it is crucial to study their energy-absorbing reliability.In this paper,the surface nanocrystallization thin-walled square tube is taken as the research object.By analyzing the main factors affecting the energy absorption effect,reliability analysis is carried out on the energy absorption characteristics of the structure by using reliability theory.Parametric modeling method is used to optimize the design of energy absorption structure,and the quantitative reliability and optimal design of energy absorption structure in energy absorption performance are obtained,which provides an effective prediction method for practical engineering application.The main research contents are as follows:First,a simulation model of the impact test of the localized surface nanometer thin-walled square tube under axial compression is established,and to simulate it numerically by finite element software.The influence of different positions,shapes,sizes and nanocrystalline degrees of local nanocrystalline regions on the deformation mode and energy absorption performance of thin-walled square tubes under impact load was analyzed,and the key factors affecting the energy-absorbing properties of thin-walled square tubes were studied.By analyzing the uncertain factors that affect the energy absorption of the structure,the energy absorption failure criterion between the input variables and the local surface nanometer thinwalled structure is established,and the reliability analysis of the specific energy absorption of the local surface nanometer thin-walled square tube is carried out.By constructing an approximate surrogate model to obtain the explicit expression between the functional functions and the variable,the reliability result can be obtained by using the optimization algorithm.Finally,based on the surrogate model,the deterministic optimization design and reliabilitybased deterministic optimization design of the local surface nanometer thin-walled square tube are carried out.The analysis shows that the number of nanocrystalline strips and the twin spacing are the main factors affecting the energy absorption performance of localized surface nanosized thinwalled square tubes,which are regarded as uncertain input variables.The model equations between uncertain input variables and functional functions are obtained by using multiple nonlinearity,support vector machine and BP neural network.By comparing the fitting degree of predicted values and experimental values under different proxy models,it is found that the fitting effect of support vector machine model is relatively best.The energy absorption reliability of the local surface nanometer thin-walled square tube based on the support vector machine model is obtained by calculation.Finally,the support vector machine agent model was embedded into the optimization algorithm to carry out the lightweight design of the local surface nano-walled square tube,to obtain the deterministic optimization results and the optimization results based on reliability.Using the above method,the deterministic optimization design scheme and the reliabilitybased optimization design scheme for maximizing the specific energy absorption of the localized surface nano-thin-walled square tube are obtained.The results show that the deterministic optimized design scheme can obviously improve the energy absorption performance and enhance the crash-resistance of local surface nano-sized thin-walled square tube.Moreover,the reliability probability constraint based optimization scheme not only enhances the energy absorption effect of the local surface nano-walled square tube,but also improves the stability of its energy absorption,providing a design idea for the lightweight design of vehicles.