Stamping Process And Compression Performance Of Aluminum Alloy Folded Core Sandwich Structure

Aerospace craft, aircraft and high-speed vehicle such as high-speed train are very sensitive to the quality of structure. Weight loss can significantly improve the load capacity and dynamic performance of the aircraft and reduce fuel consumption. So sandwich structures are widely used because their high specific strength and high specific rigidity. Folded core sandwich structure has open units which can overcome the disadvantages of honeycomb sandwich structure that it is not easy to discharge after absorption of moisture. But folded core is complex and it’s difficult to form, especially for lightweight metal sheet which is relative thick. Therefore exploring the forming process of folded core structure with lightweight metal sheet has important significance.This paper explores the stamping process and compression properties of 5052 aluminum alloy folded core structure. To better analyze the forming performance under different stamping process parameters and optimize of the process parameter, tensile tests under different temperatures and strain rate were carried out to determine the material properties firstly. The experiment found that the deformation resistance of 5052 aluminum alloy decreases with the increase of temperature and the strain and strain rate hardening effect is obvious. With the stress-strain curves under different and strain rate by experiment, constitutive model of 5052 aluminum alloy under hot tension was obtained based on Fields-Backofen equation. It provides the material parameters for optimizing stamping process parameters and the corresponding numerical simulation.The effect of stamping speed, sheet thickness, sheet size and initial temperature on the forming quality of folded core structure is explored through both cold and hot stamping. In cold stamping process,0.3mm and 0.5mm thick sheets show good forming quality among the four thicknesses used. The minimum thinning rate obtained at 1mm/min among the four stamping speed used. To form as more unites as possible at one time in actual production, it is suggested to extend the forming size in wide-direction in priority. While in hot stamping process, increasing the initial temperature of aluminum sheet can obviously improve the forming quality and the proper forming temperature is 400℃-500℃. The stamping speed is not benefit to forming folded core both too fast and too slow during hot stamping. Then the forming processes of both cold and hot stamping are simulated with the finite element software Dynaform. The thickness distribution, stress state and temperature field of the sheet during forming process is analyzed. The effect of different geometric parameters on the stamping process is evaluated. Simulation results show that in hot stamping process, the temperature decreases quickly in area which cracks are more prone to happen in cold stamping. So the deformation resistance increases, the deformation area transfer and the sheet deforms more uniformly.The compression performance of folded core structure is studied through quasi-static compression test of the sample. The experiment results show that folded core structure formed by stamping is an effect energy absorption structure. The compression process has experienced three stages:a) elastic deformation stage with the compression force rising rapidly; b) crushing stage after buckling which has stable plastic deformation; c) densification stage with the compression force rising rapidly again. The failure mode of the structure is mainly buckling and the formation of plastic hinge. At last, the effect of different geometric parameters on the compression performance of folded core structure is studied through numerical simulation with software Abaqus. The average crush strength of structure decreases with the unite side length, half open angle, and lateral angle increases.