Energy Absorption And Dynamic Characteristics Of SMA Lattice Structures

Shape Memory Alloy(SMA)has superior damping characteristics,super elasticity,and a bicameral lattice structure.Due to its unique structural characteristics,SMA bicameral lattice sandwich plates have the characteristics of light weight,high strength,high heat resistance,sound absorption,energy absorption and shape memory,and can be used as vibration absorption and energy absorption of structures.In this paper,the main research work of SMA bicameral lattice sandwich plate is as follows:Firstly,an out of plane compression test was carried out for SMA lattice sandwich plates with different lattice core forms,numbers and sizes.It was found that the main failure mode of SMA pyramid lattice is the buckling of core,while the main failure mode of two-pyramid lattice structure is the bending of core.The pyramid cell reaches the elastic limit load is 145N.The bipyramidal cell reaches its elastic limit load at 209N.The load corresponding to the elastic limit of 2mm two-pyramid lattice is 620N,that of 3x3 two-pyramid lattice is 1700N,and that of 4x4 two-pyramid lattice is 3200N.There is an approximate linear relationship between the elastic limit load and the number of bipyramidal cells.With each additional cell,the carrying capacity of lattice sandwich plate increases by 200N.By studying the effects of loading rate,strain amplitude and cycle number on the mechanical properties of the core,it is found that when the loading speed increases by 2mm/min,the energy decreases by 2.44%,the loading times increase by ten times,and the energy change rate decreases by about 2.5%.Every 100N increase in load strength,the energy increases by 20 N·mm.With the increase of loading times and loading rate,the energy absorption capacity of lattice decreases and stabilizes.Secondly,through sinusoidal scanning experiments on the boundary conditions of SMA bicond-pyramid lattice sandwich plates with four sides fixed,opposite side fixed,one side simply supported to the side fixed,four sides simply supported and opposite side simply supported,vibration magnitude and core size,it is found that the third order natural frequency is the maximum under four sides fixed,and the first third order natural frequency is the minimum under one side simply supported to the side fixed boundary.The amplitude of acceleration response at the center position of the panel is the smallest under the condition of simple support on four sides,and the amplitude of acceleration response is the largest under the condition of fixed support on four sides.With the increase of vibration magnitude,the amplitude of acceleration response of SMA lattice sandwich plate increases and the resonance frequency decreases.The increase of core size has little effect on the natural frequency,but the acceleration response amplitude decreases with the increase of core size.The simulation results show that the change of boundary conditions has a great influence on the modes of each order.The first three natural frequencies of the structure under the condition of four-sided fixed support are130.31%,150.32%and 88.76%higher than that under the condition of one-sided fixed support boundary,respectively.With the increase of constraint degree,the first three natural frequencies are decreasing.And the gap between the second and third order natural frequencies is decreasing.Then,the root-mean-square acceleration response and vibration damping efficiency of lattice structure under 0.01g~2/Hz、0.05g~2/Hz、0.1g~2/Hz acceleration magnitude are studied by random vibration simulation method.It is found that the root-mean-square acceleration response and vibration damping efficiency both show an increasing trend with the increase of vibration magnitude.Finally,through the numerical simulation method,the influence of different core missing position,form and degree,different opening position and number of panel,different disbonding position,form and degree on the modal shape and natural frequency of sandwich plate structure is studied.It is found that the core missing position will cause the modal shape deformation near the missing position to move to this position.The mode shapes caused by different missing positions,forms and degrees are different.The second and third order natural frequency of the defect form with four cores missing from the corners of sandwich plate is the highest,and the first order natural frequency of the defect form with four cores missing from the center of sandwich plate is the highest.With the increase of defect degree,the natural frequency of structure decreases.The second order natural frequency of the four corner cores is the highest,and the third order natural frequency of the two cores of a group of opposite sides is the highest.The increase of the degree of desviscosification will lead to the decrease of the natural frequency.