Dynamic Performance Of Cellular Metal Materials And Their Micro-structural Design

ABSTRACT:Due to the potential advantages of multi-functional integrated design, cellular materials have been widely used in different fields. How to establish the relations between cell micro-topology structure and macro-dynamic responses, and realize the self-design of micro-structure of cellular materials is always the frontier. Considering the micro-topology parameters, in this dissertation, a series of researches have been carried out to study the dynamic crushing performance of 2D and 3D cellular materials. The main works includes:1) The influence of the cell micro-topology structure on the in-plane dynamic performance of honeycombs is investigated;The dynamic properties of the honeycombs filled by cells with different shapes (equilateral triangular or quadratic cells), arrangement (regular or staggered arrangement) or combination (Kagome honeycomb) patterns are analyzed. The dynamic evolution of the micro-structures during the crushing is discussed. By introducing the edge connectivity factors ZT (or ZQ), the empirical formulae for honeycombs filled with equilateral triangular or quadratic cells are established, respectively. Based on the results for triangular and hexagonal honeycombs, the deformation mechanism and energy absorption properties of supercell Kagome honeycombs are given. (Chapter 3)2) The effects of defects and their inhomogeneous distribution on the in-plane dynamic crushing of honeycombs are studied;Based on the deformation characteristics of perfect (equilateral hexagonal, triangular or quadratic) honeycombs, the influences of the defect (cell wall missing) location, the defect ratio and the impact velocity on the in-plane deformation modes and plateau stresses of honeycombs are discussed. By introducing a defect correction factorβm, an empirical formula is established to evaluate the plateau stress of defective honeycombs with different defect ratio and location under different impact velocities. (Chapter 4)3) Based on the concept of functionally graded materials, the density graded cellular material is proposed, and the effects of density gradients on the dynamic crushing performances of cellular materials are investigated.By changing the radius (or wall thickness) of cells, the density-graded circular honeycomb and 2D metal hollow sphere arrays are established. The influnece of the impact velocity, packing pattern and density gradient on the dynamic performance of 2D cellular materials (circular honeycomb or 2D sphere array) is explored in detail. The relation between the dynamic responses of 2D cellular materials and the impact velocity and density gradient is established. Based on the results of 2D hollow sphere arrays, the dynamic responses of 3D metal hollow sphere arrays with different lattice structures are also investigated. The effects of lattice structures (simple cubic, body-centered cubic, and face-centered cubic) and connection between spheres (discrete or connected) on the dynamic deformation modes and energy absorption ability of 3D hollow sphere arrays are studied. (Chapter 5 and Chapter 6)...