| Honeycomb metal sandwich panel has been widely used in rail transit and other engineering fields because of its excellent characteristics of light weight,high specific energy absorption and specific strength,playing the role of lightweight and passive collision safety protection.Based on aluminium honeycomb sandwich panel and the train driver room aluminium honeycomb hood as the research object,from two aspects: material and structure,using the experiment combined means of simulation,the system was studied in 6008-T6 aluminum alloy for the honeycomb panel and the panel driver chamber hood under impactloading panel crushing,deformation instability and failure such as cracking phenomenon.Firstly,the Johnson-Cook dynamic constitutive model of aluminum alloy 6008-T6 was modified for strain rate strengthening effect and temperature rising softening effect under high strain rate.Meanwhile,GISSMO failure model parameters of aluminum alloy 6008-T6 were calibrated and obtained according to fracture strain information collected from quasi-static fracture test.Secondly,dynamic tensile fracture tests of materials at high strain rates were carried out to supplement the effects of strain rate effect and element size effect on fracture strain in GISSMO model.It was extended to a dynamic failure model.The results of numerical simulation were in good agreement with the target tests in the literature.The results show that the fracture strain decreases first and then increases with the increase of strain rate,and the softening effect of temperature rise at high strain rate is stronger than that of work hardening effect.With the increase of grid size,the grid dependence factor and damage weakening index show negative exponential power relationship.Then,the three-point bending test and quasi-static collapse test of honeycomb sandwich panel were carried out,and two different failure modes of honeycomb sandwich panel were discussed.By comparing the numerical simulation with the experimental results of the two groups,the accuracy of the modeling of the honeycomb panel finite element model and the reliability of the GISSMO failure model parameters are verified.On this basis,the influence of different parameters on the dynamic impact response of honeycomb sandwich panel was studied by numerical simulation system.The results show that the peak force decreases with the increase of impact times under three different impact times.The energy absorption rate of honeycomb panels with different thickness decreases with the increase of impact times.The maximum tangential peak force and the most serious damage of the upper panel exist near the impact Angle of 60°.The energy absorption rate of honeycomb panel increases with the increase of impact Angle.Finally,the numerical simulation of the dynamic impact response of the falling ball was carried out around the honeycomb hood of the driver’s cab of a city car,and the structural optimization and improvement were made to solve the impact failure problem of the hood top.The results show that for curved honeycomb sandwich structure,appropriately increasing the thickness of the lower concave panel can effectively improve the impact resistance of the driver’s cab structure.The damage of the driver’s cab can be effectively reduced by adding reinforcing bars at the bottom of the lower panel and supporting beams on the door frame of the driver’s cab.The above work improves the dynamic constitutive model and fracture failure model of aluminum alloy 6008-T6 commonly used in rail transit,and improves the applicability and engineering application value of the model.At the same time,it provides reference for the failure simulation and optimization design of aluminum honeycomb hood structure. |
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