Mechanical behavior of A356 matrix nanocomposites fabricated using two step mixing via stir casting technique
In this work an investigation of compressive strength and forgeability behavior have been made to explore the effect of SiC nano particles on A356 alloy matrix for the development of A356/SiC nanocomposites using two step mixing through stir casting technique. A356 alloy ingot was selected as a matrix and AFP+SiCn (99.9% pure aluminium fine powder+nano size SiC mechanically forged by using ball mill at 100 rpm for duration of 10 hours) as a reinforcement. Argon gas was used to protect from oxidation during ball milling process. SiC nano particles were varied from 1% to 5% in a step of 1% by weight. In stir casting technique, stirring process was performed at 500±50 rpm for mixing AFP+SiCn in the melt matrix for total stirring period of 10 minutes in two steps. Composites were poured at 680±20° C into the permanent mould. Compressive strength and forgeability tests of fabricated nanocomposites were evaluated by using hydraulic pellet press machine. To analyze the fractured mechanism SEM microstructure was examined. The presence of SiC nano particles were confirmed by EDX spectrum. It was revealed from the results that compressive strength increases with increment of SiC nano particles and found as 603 MPa at 5% SiC nano particles. Whereas forgeability of the nanocomposites were decreased with the increment of SiC nano particles. SEM micrographs showed the ductile fractured mechanism was dominant over the brittle fracture. The main constituents present in the nanocomposites were verified by EDX spectrum.
Forgeability and Machinability of Stir Cast Aluminum Alloy Metal Matrix Composites
In the present paper, the aluminum alloy i.e. LM6 based composites reinforced with different weight fraction of SiC particles was produced by stir cast technique and the effect of reinforced ratios on the forgeability and the machinability was examined. The test results show that the increment in weight fraction of reinforcement particles in the matrix metal produced better mechanical property like hardness but the forgeability of the cast MMCs decreases. The forgeability of the as cast MMCs were also varied with the change in thickness of the casting. The results show that the forgeability of cast metal matrix composites at the mid section of the casting is minimum compared to both end section of a three-step casting. The effect of machining parameters, e.g. cutting speed and depth of cut on the surface roughness and cutting forces at constant feed rate was investigated during experimentation. The results show that higher weight percentage of SiCp reinforcement produced a higher surface roughness and needs higher cutting forces during machining operation. It has also observed that the depth of cut and the cutting speed at constant feed rate affected the surface roughness and the cutting forces. This practical research analysis and test results on the forgeability and machinability of Al/SiC-MMC will provide useful guidelines to the present day manufacturing engineers.
A model for predicting heat transfer through gypsum‐board/wood‐stud walls exposed to fire
To facilitate the development of cost-effective and flexible design options there is a need to develop models to predict the fire resistance of wood-frame building assemblies. Such assemblies often derive much of their fire resistance from a protective membrane composed of gypsum board. A simple two-dimensional computer model is presented to predict heat transfer through gypsum-board/wood-stud walls exposed to fire. Input data for the thermophysical properties of gypsum board were measured exploying standard bench-scale tests. Input data for wood were selected from the literature. Small-and full-scale fire resistance tests were conducted on gypsum-board/wood-stud wall assemblies to provide data for the validation of the model. The model is shown to predict heat transfer through these walls rather well.