Study On Impact Mechanical Properties Of Lightweight Grid Structure

Lightweight grid structure has been widely used in aerospace, transportation,automotive industry, electromagnetic shielding and many other fields due to itsexcellent performances such as large energy absorption capacity, high bearingcapacity, high specific strength and high specific stiffness.At present, researches on static and quasi-static mechanical properties of the gridstructure have been well-conducted. However, limited researches on dynamicmechanical properties have bean carried out. How to establish the relationshipbetween cell micro-structure and its macro-kinetic response characteristics, and torealize multifunctional design of the grid structure has always been a frontier problem.This thesis simulates the impact mechanical properties of lightweight gridstructure by finite element analysis software ANSYS/LS-DYNA. The main contentsare as follows:The impact resistant performance of a typical grid cylindrical structure wasanalyzed by numerical method. The dynamic impact performance of cylindrical shellstructure consisting of the same cells with different arrangement was discussed. Thedynamic deformation modes, bearing capacity, energy absorption capacity of the gridstructure with different arrangements were derived. Besides, the affect of impactvelocity, relative density and relative thickness on dynamic properties of structurewere taken into account.The equivalent mechanical properties of the grid structure were investigated. Thegrid cylindrical structure is equivalent to a homogeneous shell with the samethickness through the derivation of elastic constitutive relation of the cell. The effectsof the different impact velocities, different relative densities and relative thickness onthe structural equivalent properties were discussed. Then, applicability and limitationsof the equivalent method were discussed.According to the analysis about equivalent performance of grid structure, thestiffened cylindrical shell structure could be equaled to the two-walled continuumstructure. The effects of shell thickness and cross-sectional shape of the ribs onequivalent properties were discussed. In addition, the bearing capacity of stiffenedcylindrical shell structure with the elliptic openings defects was also studied using the equivalent model.Impact resistance of combination grid structure was studied. Finite elementmodel of grid structure consisting of hybrid arrangements of different cells wereestablished. The dynamical deformation mode, energy absorption efficiency as well asstructural stability of the combination grid structure under the impact load wereinvestigated. Moreover, effect of the impact velocity on their resistance behavior todeformation was also taken into account. An optimal combination structure with highimpact resistance was suggested through a numerical comparison. The presentresearch can provide a reference for the design of combination structure.