Abstract: In this paper the effect of thermal fatigue on mechanical behaviour of the heat affected zone on ferritic side of bimetallic weld was investigated. The bimetallic weld coupons between ferritic steel SA516 Grade 70 and stainless steel 304L were fabricated using TIG (Tungsten Inert Gas) welding process. In this investigation, an experimental test rig was developed and used to simulate the thermal fatigue conditions at laboratory scale. The thermal fatigue factors selected were heating time, notch radius and number of cycles.
Abstract: The effect of low doses of gamma and electron irradiation on mechanical strength of Bi2Sr2CaCu2O8 (Bi-2212) superconductor ceramics was studied by exposing the superconductor to gamma irradiation dose of up to 50 kGy, and electron irradiation dose of up to 80 kGy. All the samples were prepared using the conventional solid-state reaction method. For samples to be irradiated with electron particles, 5% weight percentage of nanosized MgO was added to absorb certain amount of the energy from electrons and thus reducing the formation of complicated defects structure in the Bi-2212 superconductor. The SEM micrographs of the Bi-2212 superconductor showed the existence of platelet-type grains of Bi-2212 phase in both non-irradiated and irradiated samples. The XRD patterns for the non-irradiated and irradiated samples showed well-defined peaks of which could be indexed on the basis of a Bi-2212 phase structure. The phase purity, lattice parameter, surface morphology and degree of crystallinity for the non-irradiated and irradiated samples were also compared and analyzed and it was found that both the gamma and electron irradiation have considerable effect on the mechanical properties of Bi-2212 superconductor. When subjected to gamma and electron irradiation, the microstructure of the samples was found to be more textured and consequently enhanced the strength of the samples.
Abstract: In this study, the effect of process parameters on microstructure and mechanical properties of friction stir welded aluminium matrix composites (AMC) have been explored. The results indicated that the recrystallized grain size at the bottom of the weld region is smaller than that at the top region due to difference in the heat transfer at the weld region. The joint strength of AMCs depends on proper selection of process parameters like tool rotational speed and welding speed. If process parameter values are beyond the optimal value, the joint strength decreases due to formation of defects. Maximum tensile strength is obtained for rotational speed of 1000 rpm and welding speed of 80mm/min.
Abstract: Weld Overlay Cladding (WOC) shares the same scientific principals as conventional welding where there are multiple governing factors that control the process and outcome. The present work employs a Design of Experiment (DoE) approach to optimising process parameters for cladding a nickel superalloy onto low alloy steel with the aim to improve productivity and quality. The arc current, the clad metal heating current were identified as the key process variables for this stage of experimentation. A full-factorial 4-by-2 test was carried out to identify the optimal levels. Results showed that there is a mild positive trend between the height of individual strings of beads and both variables. However no relationship was established with the depth of penetration, nor with the height of single or double layer stacks. The optimal level of the variables was therefore chosen to be the one that has the highest productivity rate as there were no significant differences. Further experimentation has been planned and described in this paper.
Abstract: In the present work improvement in mechanical properties due to the presence of silicon oxide (SiO2) reinforced particles with an average size of 50μm and various weight percentage of (3, 6 and 9) on the hardness and fracture behaviour of Al6061-SiO2 composite is investigated. The influence of artificial aging with different aging temperatures on the mechanical properties was also assessed. Macro hardness and mechanism of fracture behaviour during tensile test have been discussed. Failure mode of fracture surface is studied to determine the parameters which influence the crack growth characteristics. Addition of SiO2 particles and artificially aging at 100°C for Al6061-SiO2 composite shows improvement in hardness by 140% and tensile strength by 60% due to the precipitation of finer secondary intermetallic phases of alloying elements. Fracture surface analysis for composite shows particle interface fracture and void nucleation growth failure.
Abstract: Processing of Langkawi black sand for the recovery of metals had been carried out in this study. The samples were characterized after sieve analysis. Magnetic separator is used to separate between magnetic and non-magnetic portion of blank sand. XRF and FTIR were used to know the metal content in black sand. Before magnetic separation black sand contain about 43.2 wt% SiO2, Al2O3 with 21.1 wt% and Fe2O3 with 17.2 wt% and 12.0% TiO2.
Abstract: Biobased shape memory polyurethane filled with carbon nanotubes (CNT) were prepared using two step polymerization process. The bio based shape memory polyurethane (SMPU) were composed of polycaprolactonediol, polyol based on palm oil, 4, 4’-diphenylmethane diisocyanate and 1, 4-butanediol. In this paper, CNTs has been used as fillers to introduce the electrical conductivity in the SMPU. The bio-based shape memory polyurethane shows electrical conductivity with addition of 7 wt% CNT.
Abstract: This paper presents composite of oxo-biodegradable high density polyethylene (oxo-HDPE) and ground coffee waste (GCW). The blends were evaluated at the proportion of 94.5 to 5.5 polymer-filler ratio with different particle sizes, extraction and mercerisation treatments. Compression moulding has been employed to fabricate the composite. Microstructure of the ground coffee waste was characterised using SEM. SEM showed the surface of the treated fibres were coarser as impurities were removed. Chemical modificated GCW showed better adhesion with the matrix. Both untreated and treated GCW/oxo-HDPE composite improved in tensile modulus.
Abstract: This paper is motivated by the lack of studies in the technical literature concerning to the three dimensional vibration analysis of thick laminated rectangular plates with continuously graded carbon nanotube-reinforced (CGCNTR) sheets. The formulations are based on the three-dimensional elasticity theory. The proposed rectangular plates have two opposite edges simply supported, while all possible combinations of free, simply supported and clamped boundary conditions are applied to the other two edges. The structure is supported by an elastic foundation with Winkler’s (normal) and Pasternak’s (shear) coefficients. The material properties of the functionally graded carbon nanotube reinforced composites are graded along the thickness and estimated through Mori-Tanaka method.
Abstract: This report presents a comparative assessment of the suitability of two existing physical models for predicting yield strength of artificially aged AA6063 Al-alloy. One model is based on the modified Orowan mechanism of dislocation by-pass for non-shearable rod shaped precipitates rejuvenated by Zhu and Stark, and the other model is based on classical dislocation-particle interaction that incorporates both cutting and by-pass mechanisms for spherical shaped precipitates developed by Deschamps and Brechet. Using these models, simulation of yield strength values have been performed considering nucleation-growth as well as nucleation-growth-coarsening of precipitates during the entire period of ageing. Comparison of experimental and simulated results reveals that the model by Deschamps and Brechet predicts yield strength more accurately when nucleation-growth-coarsening of precipitates are incorporated.