Compressive deformation and energy absorbing characteristic of foamed aluminum
- PDF / 803,932 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 68 Downloads / 185 Views
I.
INTRODUCTION
IN many engineering fields, cellular materials are needed in packaging to protect the packaged object from failure when it is subjected to impact. They absorb the impact energy while keeping the stress acting on the object lower than its damage limit. Various polymer foams are most widely used for this aim.[1,2] Nevertheless, the energy absorption capacity of polymer foam is relatively low because of its low compressive strength. Under the condition of a much higher impact load, an absorber made of polymer foam should, therefore, be voluminous enough to absorb the energy. Moreover, polymers are usually not resistant to heat and corrosion and are easily degraded. All these unfavorable features limit their use in some special circumstances. Fortunately, foamed metals (for instance foamed aluminum (FA)) make it possible to overcome these disadvantages. Foamed aluminum can be made with very high porosity (most commonly in the range of 0.60 to 0.85) and therefore has quite low specific gravity, combined with a higher specific modulus, a higher strength, and a better corrosion resistance.[3–6] It has been shown that FA has many potential engineering applications including energy absorption. One of the common features of energy absorption materials is that there is a discernible plateau in their compressive stress-strain curves. This feature means that the materials can absorb energy by deformation but keep the stress almost constant. Foamed aluminum has this feature also, and since it has a high strength and a high plateau, it will have a higher energy absorption capacity than polymer foams. However, there is little reported research on the characteristics and related mechanisms of FA. Much information remains to be found for engineering design. The objective of the present study is to provide an insight into the deformation and energy absorption performance of FA through examining its compressive stress-strain curves with various structures. FUSHENG HAN and ZHENGANG ZHU, Professors, and JUNCHANG GAO, Assistant Engineer, are with the Laboratory of Internal Friction and Defects in Solids, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230 031, P.R. China. Manuscript submitted January 6, 1998. METALLURGICAL AND MATERIALS TRANSACTIONS A
II.
EXPERIMENTAL PROCEDURES
A. Preparation of FA Specimens Foamed aluminum blocks were manufactured by a melting foaming process using commercially pure aluminum and aluminum-10 pct magnesium alloy (AlMg10).[7] The whole process is comprised of five steps: (1) melting metal ingot at 700 7C; (2) adding MnO2 powder (mean particle size of 20 mm) into the melt and stirring it at a speed of 800 rpm to make it become a viscous fluid; (3) introducing TiH2 powder (mean particle size of 40 mm) into the modified melt and stirring at an increased speed of 2300 rpm to distribute the powder uniformly in the melt; (4) keeping the mixture at 625 7C for 120 seconds, allowing TiH2 to decompose and release hydrogen gas and allowing bubbles to evolve; and (5) removing
Data Loading...
