Finite Element Analysis on the Unloading Elastic Modulus of Aluminum Foams by Unit-cell Model
This paper presents finite element analyses (FEA) on the unloading elastic moduli of aluminum foams under uniaxial loading and bending conditions. The unit-cell model of Gibson and Ashby was utilized in the FEA with elasto-perfectly plastic material. Compression, tension, and bending tests simulations were carried out using Abaqus software. The non-linearity effect caused by structural imperfection/buckling of unit-cell was incorporated. From the compressive test simulation, it was confirmed that the results showed good agreement with the referred experimental data. This means that the developed FE model can be regarded as an RVE model of aluminum foams. Then, the deformation characteristic and elastic modulus obtained from all simulations were compared and examined. As the results, the elastic modulus obtained from bending test demonstrated higher value than that of under uniaxial loads. This discrepancy increases gradually as the relative density decreases. The mechanism responsible for generating the discrepancy in stiffness was discussed. Furthermore, this work points out the necessity of measuring both Young’s and flexural moduli for designing an engineering structure using foam materials especially when accuracy and precision are demanded.
Elastic Bending Behavior of Aluminum Alloy Foam
Aluminum alloy foam has been an attractive material to be used in many engineering applications due to its novel properties and behaviors in combination with the light-weight structure. Many researches had been conducted to enable and explore more widespread engineering applications of this material; however, its mechanical responses are yet to be fully understood. The work presented in this paper is aimed at studying the elastic bending behavior of aluminum alloy foam by experimental investigations and theoretical analysis. From the experiments, the measured flexural moduli are found to be significantly larger than the corresponding Young's moduli. Moreover, the foam's stiffness equation introduced by Ashby et al. for the design-guide is found to be not suitable for estimation of the flexural moduli. The theoretical analysis was carried out to identify the mechanism responsible for generating the discrepancy. We found that the different in cell local-deformation under uniaxial loading and bending condition plays a prominent role in the discrepancy, where in particular, the effect of cell-face stretching was found to be dominant in bending condition.
Experimental Study on Acoustic Agglomeration of Fine Particles from Coal Combustion
The removal of fine particles in coal-fired fumes was experimentally studied based on acoustic agglomeration. An experiment facility was designed and set up. In this facility, a fluidized bed coal combustor was used as fume generator, and an Electrical Low Pressure Impact or (ELPI) was used to measure the fine particle concentration and size distribution in the fumes. The results show that under the effect of high intensity sound waves, there is good performance to remove fine particles in coal-fired fumes, which with a number mean diameter of 0.07μm. Especially, under the conditions of the frequency of 1 000Hz and the sound intensity of 161.5dB, the number concentration of 0.0233~9.314μm particles decreased by 85.2%, and their mass concentration decreased by 92.5%.