Applied Mechanics and Materials Vol. 315

Abstract: The influence of hydrogen on the fracture morphology and mechanical properties of ASTM A106 Grade A pipeline steel has been studied by tension, bend test and hydrogen charging with combination of variation current density and charging time. The appearance of surface damage and fracture morphology were revealed by using field emission scanning electron microscopy. Under the hydrogen charged, the reduction of strength and ductility of the steel revealed from the ultimate tensile strength value and percent of elongation were observed as the current density increased. While, in bend test, the effect of hydrogen is manifested as a decrease in ultimate strength (maximum load in bend test) and bend ductility (bend angle).

Abstract: Acoustics environmental analyses were conducted in the unoccupied examination hall at Universiti Tun Hussein Onn Malaysia (UTHM), in order to determine the acoustical environment which reflects to sound comfort during sitting exam. The acoustic parameters that measured are background noise level, sound pressure level and reverberation time. The analysis result of untreated wall condition (without absorbent material) was revealed poor while treated wall condition (with absorbent material) revealed the improvement result. Installation of absorbent material on the wall and speakers rearrangement had reduced the highest background noise level of examination hall average reverberation times. A minor alteration at examination hall had contributed to better acoustic performance.

Abstract: This work presents the load carrying capacity of partially textured journal bearing with trapezoidal recess. The partial texture geometry is composed of a number of successive cells of trapezoidal recess and land configurations. The non-dimensional pressure expressions for the partially textured journal bearing with trapezoidal recess are derived. Results of nondimensional load capacity are provided taking into consideration of texture geometry with trapezoidal recess and extent of partial texture.

Abstract: Downdraft evaporative cooling systems can be used for the thermal management of inside spaces in hot dry environments. There may be scope for improvement of such systems. The work described here is a study aimed at validating the Computational Fluids Dynamics (CFD) method using experimental data available from a prototype multi-stage system which existed at Ben-Gurion University. A detailed model of the prototype device has been developed. Initial CFD work has focused on establishing the relationship between ambient wind speed and the downdraft flow rate and comparing the result with the existing experimental data. Initial results are consistent and encouraging. Detailed flow features not evident from the experiments are revealed. Further CFD work to model the prototype performance with water spray evaporation is described briefly.

Abstract: This research is an approach to investigate the effect of cutting condition on surface roughness in dry and flood cutting of AISI 1030. The objectives of this project are to compare the plastic injection mould quality between dry and flood cutting condition, as well as to determine the best cutting condition. The parameters used were depth of cut (0.25mm, 0.5mm, and 1.0mm), feed rate (50mm/rev, 100mm/rev and 150mm/rev) and cutting speed (700m/min, 1400m/min and 2100m/min). Surface roughness value was used to determine to quality characteristic of the machined mould. The experiments were done using Mazak CNC milling machine and the material selected was AISI 1030, which is a medium tensile and low hardenability carbon steel. Twenty-seven runs were done in both dry and flood cutting, adapting Taguchi Method - Orthogonal Array. After each machining, the surface roughness was measured using Mitutoyo Surface Roughness Tester. The data obtained was then analyzed through Signal to Noise Ratio calculation. This analysis produced the best combination of parameters which gives the lowest surface roughness. The best combinations for dry cutting are 2100m/min for cutting speed, 50mm/rev for feed rate and 0.25mmfor depth of cut. As for flood cutting, the best combinations are 2100m/min for cutting speed, 50mm/rev for feed rate and 1.0mm for depth of cut. The surface roughness obtained using this parameter in dry cutting is 0.27Ám and 0.40Ám in flood cutting. From the comparison, it is proved that dry cutting produced lower surface roughness compared to flood cutting.

Abstract: In this paper an attempt has been made to investigate the performance of an electrode made through powder metallurgy (PM) of copper tungsten during electrical discharge machining (EDM). Experimental results are presented on electrical discharge machining of AISI D2 hardened steel in kerosene with a copper tungsten (Cu35% - W65%) tool electrode made through PM method with a constant duty factor of 80%. In terms of high performance EDM process, higher peak current (>20A) and pulse duration (>400µs) with a high machining efficiency were applied. Experimental results have shown that machining at a peak current of 40A and pulse duration of 400µs yields the highest material removal rate (MRR) whereas machining at a peak current of 20A and pulse duration of 400µs yields the lowest tool wear rate (TWR). The surface characteristics of workpiece machined surface become more severe when shorter pulse duration be used at the constant duty factor. The optimum machining performance can be performed by the combination of pulse duration and peak current at 400µs and 40A respectively since the effect of TWR is so small at the varied parameters even at the highest MRR.

Abstract: This paper evaluate previous experimental studies on sub-freezing start up of proton exchange membrane (PEM) fuel cell system, and identify issues for further investigation. In a successful cold start, product water from electrochemical reaction in the cathode must be removed from the cell before it turns into ice and causing voltage drop and shutdown also leads to permanent damage to fuel cell components. Successful single PEM fuel cell start up was achieved from temperature as low as-30°C. Some researchers found that cold start of a 30 W stack from-20°C was possible only with aid of external energy. Successful self-start up a 2 kW stack from temperature-5°C was reported but the time taken was unacceptably long and attempts to start up the stack at lower temperatures were failed. Based on the current state of research, further research is necessary to fully understand the operation and mechanism of PEM fuel cell cold start.

Abstract: In the present paper an experimental investigation on green sand casting of Al-Si cast alloy (LM6) has been conducted. The main objectives of the research were the effect of pouring temperature on microstructure property of green sand casting Al-Si LM6 Alloy. The high quality of The LM6 alloy was investigated by controlling the pouring temperature. The pattern was flat like and pouring was done with four different temperatures 630, 660, 690 and 720Cº. The obtained results showed that the pouring temperature has a significant influence on the quality of green sand casting of LM6 Al-Si alloy. The lower pouring temperature provides finer microstructure with fewer defects such as porosity.

Abstract: In the present work polyurethane foams containing various content loadings of kenaf fiber and recycled tire rubber particulates were prepared and studied, with the objective of developing alternative composite rigid foams. The influence of the filler content on the foam microstructure and its physical and mechanical behavior has been studied for three different polyurethane resin densities. Microstructural observation on fracture surface of composites was carried out using scanning electron microscopy. It has shown closed spherical cells with reduced size when the fillers are added. Nevertheless, the incorporation of kenaf fiber and recycled tire rubber particulates that refined at 80 mesh led to higher mechanical properties than that unfilled polyurethane foam. A 6% filler content loading exhibited the optimum compression stress and compression modulus, while further increase of filler content loading resulted in decline in mechanical behavior. The presence of larger filler content deteriorated the polyurethane system cellular structure and lead to poor composites strength. Overall, the use of kenaf fiber and recycled tire rubber particulates gives composite foams with comparable mechanical behavior for the studied filler reinforcement level.

Abstract: In this paper, creep analysis for a thick-walled cylinder made of functionally graded materials (FGMs) subjected to thermal and internal pressure is carried out. The structure is replaced by a system of discrete rectangular cross-section ring elements interconnected along circumferential nodal circles. The property of FGM is assumed to be continuous function of volume fraction of material composition. The creep behavior of the structures is obtained by the use of an incremental approach. The obtained results show that the property of FGM significantly influences the stress distribution along the radial direction of the thick-walled cylinder as a function of time.