Load-bearing Analysis Of High-speed Train Sandwich Composite Floor Based On Random Failure Model

As a lightweight composite material,laminated structure is widely used in aerospace,automobiles,ships,rail vehicles and other fields.The main forms of the most common sandwich laminates include: a soft core(central layer)and two outer surface layers(skin or panels),and the layers are bonded together by an adhesive.This type of laminated structure is affected by load-bearing conditions and processing technology,and the randomness of failure is strong.Studying its load-bearing characteristics and failure prediction has important theoretical significance and engineering value for guiding structural design and optimizing manufacturing processes.The thesis takes the aluminum alloy-PVC composite laminate for high-speed train body floor as the research object,and analyzes the load-bearing capacity,failure reason and form of the high-speed train composite laminate floor based on finite element numerical simulation technology.The main contents are as follows:(1)A three-dimensional finite element model of the aluminum alloy-PVC laminate is established based on the cohesive element and the calculation under the four-point bending load condition is realized.The simulation results are in good agreement with the experimental data.On this basis,the sub-model is selected from the complex laminated floor structure of the actual high-speed train,and the load-bearing capacity of the floor is simulated and analyzed under two actual working conditions.Numerical simulation results show that the maximum stress concentration of the high-speed train aluminumplastic laminated floor is located at the edge of the plate loaded area,and the maximum load-bearing capacity under the two working conditions is 575 k Pa and 50 k Pa,respectively.Comparing the shear stress and the fitting curve at each position of the floor PVC core axis under the two working conditions,it is believed that the floor has a higher load-bearing capacity under the occupant standing condition.(2)Define the PVC core material and adhesive layer of the laminated floor with the collapsible foam material model and the cohesive constitutive model,and establish the failure model of the high-speed train floor.The simulation calculation results show that the failure mode of the floor is interlayer cracking and core material damage.The adhesive layer has priority to the PVC core material to fail,and the failure position starts at the edge of the floor;the shear stress and deformation displacement at different positions of the edge of each layer are analyzed,It is believed that the reason for the failure is that the corresponding shear stress difference between the upper and lower surfaces of the adhesive layer element can reach 30 MPa,and the shearing force is significant;the vertical deformation difference between the PVC core layer and the aluminum alloy panel is up to 0.03 mm,and discordant deformation leads to interlayer cracking..(3)A stochastic model of the adhesive layer element with adhesive defects based on the standard normal distribution model was proposed and established,and it was applied to the finite element model of the high-speed train floor and the analysis of the delamination failure of the floor.7 different materials were established The parameters of the adhesive layer element,and the reliability of the random model was verified.The analysis results show that the established random model with bonding defects after the simulation calculation meets the normal distribution form,which confirms the validity of the model;and the floor is loaded to the compressive stress of 0.254 MPa when the original adhesive layer fails,the failure probability of the adhesive layer with bonding defects is 50%.(4)Simulation analysis and regular discussion of the factors affecting the loadbearing capacity of the high-speed train floor.Considering the number of floor support structures,the layout geometry position,the floor structure form and other influencing factors on the failure of the train floor,the simulation compared the changes of each influencing factor on the failure form of the floor and the initial failure location;Analyzing the floor with bonding defects under the influencing factors,when the loadbearing pressure of the floor reaches 1.675 MPa,the probability of failure of the adhesive layer is 75%.On this basis,by comprehensively comparing the overall stress distribution of the floor under the same load conditions,the maximum stress on each layer,the deformation of the center of the floor,the improvement of the load-bearing capacity obtained by simulation analysis,the lightweight of the structure,the cost of floor processing and the complexity of other factors Suggestions for the improvement of the floor structure,and provide simulation technology support and reference for the actual floor improvement.