Applied Mechanics and Materials Vols. 752-753

Abstract: SiC – reinforced aluminium composite - has been developed to improve the ballistic performance and mobility of the armour material. Critical to obtaining ballistic resistance is that the materials must be sufficiently hard and strong, especially at the surface where a projectile will first make impact. To achieve this resistance, aluminium alloys can be strengthened by adding Zn and Mg, and reinforced with silicon carbide. This research studied the ballistic properties of aluminium composites with varied Mg. The matrix used in this study was an Al-8Zn alloy with 3-5 wt. % Mg. Silicon carbide particulate of 15 % volume fraction was used as strengthening material, which was added to the liquid matrix by stirring at 5000 rpm. The liquid composite was then squeeze cast at a pressure of 72 MPa. Then the composites were heat-treated and coated to improve the ballistic performance. Ballistic testing was performed in accordance with ASTM F1233 by using 7.62 calibre projectiles. Microstructural observation was conducted in samples, performed with optical microscope. The results showed that the as-cast hardness of the composite increased with addition of Mg content of 3, 4 and 5 wt. %. The peak hardness after ageing at 200 °C also increased with Mg addition. However, the composites were not able to withstand the 7.62 mm calibre projectile.

Abstract: Experimental studies have been carried out on butt-welded specimens of aluminium alloy AA6061. Two tempers; T4 and T6 prior to welding were investigated and the subsequent effects of natural ageing (NA) and post weld heat treatment (PWHT) were assessed. Digital image correlation (DIC) technique was used to obtain full field strain measurement on the transversely loaded tensile specimens. The tensile properties of these specimens are presented in terms of response curves. In addition, hardness profiles were also obtained. Both initial tempers and heat treatments were shown to give a significant effect on the mechanical response of the welded specimens tested.

Abstract: Thin metal films on polymeric materials have been widely used in electronic devices. Their total mechanical performance is determined by the mechanical property of each material, the thickness and size of film and substrate, their interface properties in addition to the temperature change during production and use. In this paper, stress and strain distribution of gold thin film on polycarbonate substrate subjected to tension and cooling was analyzed using the finite element method. The effect of cracking in thin film on the stress and strain distribution was also discussed.

Abstract: Different heat source had been investigated for thermally enhanced machining on various engineering materials. Even so, temperature control from the heat source remained a challenged to the process effectiveness.This study used oxyacetylene combustion flame as a heat source in heat assisted machining. The study focuses on the relationships between process conditions; maximum temperature distribution and the surface integrity of 316L stainless steel during preheat machining as compared to dry hard part machining. Two levels of cutting speed 1000rev/min, 630rev/min and feed rates 160mm/min and 100mm/min were investigated while the depth of cutting was maintained constant at 1mm. While preheat machining for 60seconds along the span of the work piece material at cutting speed 1000 rev/min and feedrate 100mm/rev, the average surface finish have improved by 94% over dry hard part machining. This corresponds to flank wear VB = 0.0644mm during heat assisted machining and 0.1425mm for dry hard part machining respectively. Such improvement was accompanied with longer tool life and secured surface integrity which improves the material’s life cycle.

Abstract: The effect of physicochemical parameters on methylene blue (MB) adsorption by sulfuric acid treated spent grated coconut (SSGC) was investigated. The field emission scanning electron microscope (FESEM) images showed a change in surface morphology of spent grated coconut before and after acid treatment. Energy dispersive X-ray (EDX) spectrometer suggested the mechanism of ion-exchange occurred during MB adsorption onto SSGC. The pH_pzc value of SSGC was 5.40. The amount of MB adsorbed remained constant after pH 3. The optimum dosage of SSGC was observed at 0.03 g, while the stirring rate did not significantly affect the amount of MB adsorbed. This work suggested electrostatic attraction and ion-exchange as the main mechanisms involved in MB adsorption.

Abstract: Gold nanoparticles (Au NPs) supported on nanoporous anodic aluminium oxide (AAO) membrane has been successfully prepared by direct anionic exchange for further application in catalysis. The nanoporous AAO membrane is immersed in HAuCl₄ solution at different pH to achieve gold nanoparticles grafted on AAO (Au-AAO). It was found that the pH of the HAuCl₄ solution played an important role for controlling the size of Au NPs as well as the amount of Au depositing on the surface of AAO membrane. The prepared Au-AAO membranes were characterized by diffuse reflectance UV-Vis spectroscopy, high-resolution scanning electron microscopy (SEM) and energy dispersive x-ray (EDX) spectroscopy.

Abstract: A temperature-sensitive 2-hydroxy-3-allyloxy-propyl starch ehter (HAPS) was prepared by regulating the hydrophilic-lipophilic balance of etherified starch. Allyl glycidyl ether (AGE) was used as the hydrophobic reagent. ¹H-NMR was used to characterize the structure of products and determine the degree of substitution of etherified starch. UV-Vis and fluorescence spectroscopy methods were adopted to investigate the properties of HAPS aqueous solution. The results showed that the LCST of HAPS was reduced as the DS. When the cmc of HAPS decreases and DS increases, formation of micelles in an aqueous solution by self-assembly is possible.

Abstract: The chemical changes of cement structures exposed to aggressive environments are explored in this paper. In the predetermined time intervals the influence of the aggressive liquid, namely 5% wt. non-flowing sulphate solution, on mineralogical composition was tested. The chemical changes caused by corrosive sulphate environment on the testing specimens were determined in dependence on the different type of cement. From the results obtained follows that different kind of cement has impact on the sulphate resistance.

Abstract: Development of dyes with high fixation and salt-free dyeing process for cotton and silk is essential for the textile industry due to ecological and economical reasons. In this study, the synthesis of novel crosslinking polymeric dyes and its salt-free crosslinking dyeing method are described, and cotton and silk have been effectively dyed with the novel dyes. Excellent dye fixation of over 99% on silk and over 97% on cotton, were achieved in a padding process in the salt-free condition. The dyes showed excellent wet fastness values equal to those observed for the standard reactive dyeing.

Abstract: The exposure of cement to high concentration of sulphate anions for a prolonged time period can lead to the formation of secondary ettringite and thaumasite. The preparation of synthetic ettringite is described in this paper.