Research Of Elastic-Plastic Deformation Mechanism And The Heat Transfer Characteristics Of Open-Cell Metallic Form

Porous metal materials, due to the exquisite pass topology, multi-scale size and infinite recombination, which endow them with both structure and functional attributes. Multi-functional features of favorable mechanical, excellent thermal physical, acoustic characteristics and other good performance have made cellular mental materials more and more valuable in engineering sectors of cushioning and vibration insulation, heat transfer enhancement, noise elimination, filtering separation and so forth. And have caused the tremendously attention of academic fields. However, as for the existing research and development of porous metal materials, there is a huge gap that exists between our country and international of the porous metal materials. And because the metal foam has a variety of micro-structure and cell morphology, a single deformation mechanism is unlikely to be applicable to all different types of foam even under the same load conditions. Therefore, it is necessary to conduct further study on the elastic-plastic deformation mechanism and heat transfer characteristics of metallic foams. The general finite element software ABAQUS is utilized to set up microstructure model of cellular foams, and the investigational works are as follows:(1) Based on the three-dimensional tetrakaidecahedron model, the dynamic compressive properties of the open-cell aluminum foam is investigated using the finite element (FE) method. The effects of the impact velocity and the relative density is analyzed qualitatively on the deformation modes, plateau stress, densification strain and energy absorption of the open-cell foam.(2) Based on the cubic model developed by Ashby, the effects of the topology structure of light metallic foam such as porosity and cell size on its effective thermal conductivities are investigated in this paper. Using the least thermal resistance method, the expression of effective thermal conductivities is derived, and the approximate analytic solution is obtained by employing the simplified integral method.(3) The distribution of heat flux across the open-cell metallic foam are simulated with the steady Fourier law by ABAQUS software in order to determine the influence of porosity and cell size on the thermal conductivities of the open-cell metallic foam materials.The results of numerical simulation and theoretical analysis are as follows:(1) It is found that the different impact velocity causes different failure modes and patterns:the foam follows the kind of bending-buckling deformation pattern under the low impact velocities while follow the kind of buckling-bending-buckling one under high impact velocities. (2) Two types of the deformation mechanism have been observed by the macroscopic stress-strain responses, and it transpires that the crushing deformation of metallic foams tend to the type Ⅰ response under the lower impact velocity;while it tends to the type Ⅱ response under the higher impact velocity.(3) The results also indicate that both the plateau stress and the densification strain energy aren’t dependent on crushing velocity for the low relative density, but loading-rate sensitivity for the high relative density foam. Moreover, both of them can be improved by increasing the foam relative density. The relative density has little effect on the densification strain, while the impact velocity has greater influence on the densification strain but with no simple monotonous change.(4) The theoretical study agrees well with the numerical data. The finding of this paper indicates that the approximate analytical solutions of the equivalent heat transfer coefficient using simplified integration method has better consistency with the corresponding simulation results, and it reduces13%error than the maximum value based on thermoelectricity analogy method. And the formula has higher precision in calculating the equivalent coefficient of thermal conductivity of high porosity foam material. The effective thermal conductivities of porous metallic foam almost linearly decrease with the increase of porosity, and have no change with the cell size when the porosity keeps constant. The research results are significant to the practical engineering application of metallic foams.