In this paper, fabrication and characterization of Al-SiC nanocomposites is investigated. The Al matrix is reinforced with different amounts of SiC nano-particles using mechanical milling, cold pressing, and, hot extrusion techniques. To get the best quality of the samples, the extrusion process is optimized firstly. With this regard, hot extrusion parameters such as the rate of extrusion, temperature, the extrusion ratio, lubrication, and the die set dimensions are experimentally studied. Finally, the nanocomposites with relative density more than 99% could be successfully fabricated under extrusion ratio of 8.5:1. As-extruded billets were then used to prepare standard tensile test specimens based on ASTM-E8. Afterwards, relative density, tensile behaviour, and micro-hardness of the samples were determined. The results show about 50% improvement for both the tensile strength and micro-hardness and near 1% reduction of relative density as the content of SiC reinforcement increases to 3 vol%. Therefore, specimens with higher strength-to-weight ratio which is a key parameter in aerospace and automotive applications can be produced using current techniques. تفاصيل المقالة

Given the significance of energy absorption in various industries, light shock absorbers such as structures made of metal foam have been considered. In this study, analytical equation of plateau stress is presented for an open cell foam based on the Gibson-Ashby model, which follows elastic perfectly plastic behavior. For comparison of acquired analytical equations, the problem for a cell and then for three cells that make up an aluminum open cell foam is simulated in ABAQUS/CAE. Using the stress strain diagram, plateau stress and densification strain equations, the specific energy absorbed of the open cell metal foam is extracted. The capacity of absorb energy for an aluminum open cell foam with three cell is obtained once using analytical equations and again by using numerical simulation in ABAQUS/CAE. Numerical results retain an acceptable accordance with analytical equations with less than 3% occurred error for absorbed energy. To ensure the accuracy of numerical simulation, the results of simulating are compared with the results of the simulation of the same foam in a reference whose accuracy is verified by the experiment. Based on the results, the effective cross-sectional area of the foam with Gibson-Ashby cell does not follow the cross-sectional that is used for the calculation of plateau stress in adsorbent structures. Then tow equations are extracted to calculate the effective cross-sectional area and the transfer force. Applying sequential quadratic programming method (SQP) and genetic algorithm (GA), to design a graded metal foam with high specific Energy absorption. تفاصيل المقالة