Applied Mechanics and Materials Vols. 465-466

Abstract: Rice Husk Ash (RHA) is a by-product of the agricultural industry which contains high amount of silica. Active silica from RHA has been used progressively to substitute quartz in a porcelain composition and the effect this substitution in relation to temperature on physical and mechanical properties has been investigated. It was found that progressive substitution of RHA in a porcelain composition resulted in early vitrification of the mixture. The compressive strength was highest and the porosity was the least at a temperature of 1200°C on 20wt% substitution of RHA. The improvement in the properties could be attributed to sharp changes in the microstructural features as a result of increase in mullite and glassy phase simultaneously. Hence the extension of study on microstructure and morphology has influence on the physical and mechanical properties.

Abstract: To ensure the structural integrity of composite materials, honeycomb sandwich panels must be inspected for defects with through-transmission ultrasonic testing. This study focused on the root causes analysis of disbonds and unidentifiable ultrasonic indications on composite materials. Disbonds is a condition that lack of adhesion between ply and core. Unidentifiable ultrasonic indications define as an unknown defect which can only identified after remove the peel ply. In this study, Minitab 16 and SPSS 16 are used in analyzing the potential causes that influences the disbonds and unidentifiable ultrasonic indications. The root causes of disbonds are core crush and core crack. Core crush and core crack may caused by high localized loads or high compaction pressure. For unidentifiable ultrasonic indications, the root cause is adhesive flood at core. Imperfect compaction pressure leads to the uneven flow of adhesive. For the area have lower pressure, probability for adhesive to accumulate is higher. Pleated or dog ear method can be implemented in bagging process to ensure better compaction mechanism. Operators must be trained and educated for better performance.

Abstract: The present study is aimed to determine the effect of friction stir welding pin; square and diamond shape on mechanical properties of butt joint AA6061 weldment. Welding was carried out at different plunge depths of 0.0, 0.2, 0.3 and 0.4 mm together with rotation and transverse speeds of 500 rpm and 40 mm/min, respectively. Material flow, tensile strength and hardness of the weldment were evaluated. The results indicated that joint properties were significantly affected by tool design. It was found that material flow was higher for diamond pin tool compared to that of square pin resulting in considerable increased in tensile strength of the joint. In addition, the highest tensile strength was obtained on the samples welded with square shape pin at 0.4 mm plunge depth whilst the lowest was by diamond shape at the plunge depth of 0.0 mm. Regardless of pin shape and plunge depth; asymmetrical hardness distribution was observed for all weldments. The highest hardness was found to be close to the weld line produced by the diamond shaped pin at 0.0 mm plunge depth.

Abstract: Food and feeding become a major challenge in aquaculture development. The way adjustment of food delivery to pond is an important role to get the maximum return or profit to aquaculture entrepreneurs. This project presents an investigation about the fish feeding system, a system device to feed fish at predetermined amounts of food and time. Moreover, the system is designed with a computer monitored system in order to manage and control the system with simulation. This project is a simulation investigation into the development of PID controller using Matlab/Simulink software. The simulation development of the PID controller with the mathematical model of fish feeder system is done using trial and error method. The PID parameter is to be tested with a DC motor. As a result, the best value of PID controller is achieved when K_p = 100, K_i = 0.05 and K_d = 25.

Abstract: This study is intended to predict the stress behavior of thick hard coating at the interface with the changes of coating stiffness and thickness to the substrate of Ti-6Al-4V and SCMV. The elastic mismatch between the coating and the substrate is presented in the value of Dundurs parameter α. The prediction is done using simple geometry of a cylinder-on-flat model in 2D analysis subjected to normal and tangential loading. Tangential stress distribution along the coating-substrate interface is then obtained from the FE modelling after a finite sliding of the cylinder. It is predicted that the maximum tangential stress value predicted at the interface which relates to coating fracture failure is increasing as stiffer coating is used on compliant substrate (i.e. increasing α values). The location of the maximum tangential stress predicted also changes from the trailing edge to the center of contact with increasing α values. Effect of changes of coating thickness on the predicted maximum tangential stress value is more significant for high positive α values. Risk of coating fracture at the interface is therefore predicted to increase with the increase of coating thickness and stiffness.

Abstract: This research focuses on the study of oblique impact on kenaf reinforced composite plate. This study summarizes modeling analysis of targets subjected to certain angle of collisions which ranging from 0o-45o. Due to the low density, natural fiber such as kenaf fiber provides relatively good mechanical properties than glass fiber. Thus, natural fibers have high potential for better reinforcement in light weight structures such as aircraft, automobile. In this research, the velocity impact analysis is conducted by using the commercial finite element analysis software, ANSYS. A few finite element models of the nonwoven composite panel and a rigid impactor is developed using ANSYS software. Experimental investigations in determining mechanical properties and validating purposes are conducted in earlier study by using Universal Testing Machine and High Speed Impact Puncher. Total force, total energy, deformation, and energy absorption of kenaf reinforced composite for oblique impact are analyzed and discussed. The rise of oblique angle will increase the energy absorption of the composite.

Abstract: Micro-electro discharge machining (micro-EDM) technique, an advanced noncontact machining process, is used for structuring of nonconductive ZrO₂ ceramic. In this study copper foil as a conductive layer is adhered on the workpiece surface to initiate the sparks and kerosene is used as dielectric for creation of continuous conductive pyrolytic carbon layer on the machined surface. Voltage (V) and capacitance (C) are considered as the parameters to investigate the process capability of machining parameters in continuous micro-EDM of ZrO₂. Different voltage pulses are studied to examine the causes of lower material removal rate (MRR) in micro-EDM of nonconductive ceramics. The results showed that in micro-EDM of ZrO₂ MRR increases with the increase of voltage and capacitance initially, but decreases at higher values and no significant materials are removed at capacitances higher than 1nF.

Abstract: In the event of an impact with an automobile, pedestrians suffer multiple impacts with the bumper, hood and the windscreen. The characteristics of a vehicles front end and structural stiffness have a significant influence on the kinematics and injury risk of the pedestrians body regions, in a vehicle-to-pedestrian collision. In this present study, the injury risk of the pedestrian is investigated in an impact with a deformable vehicle front end model for the purpose of validating the developed model. A simplified vehicle front end model consisting of a multi body windscreen and a finite element cowl, hood and bumper is developed. The MADYMO human pedestrian multi body dummy model is impacted by the vehicle front end model at the speed of 40 km/h. The injuryto the various body segments namely the head, neck, sternum, lumbar, femur and tibia is obtained. The simulation values are compared to the experimental values for verification of the vehicle front end model.

Abstract: Tests have been performed on a riser model with low mass ratio subjected to uniform flows in a towing tank at subcritical Reynolds numbers. Qualisys video motion capture system was used to measure VIV and Spring bars are used instead of commonly used parallel linkage mechanism for this kind of test. The circular cylinder of 100 mm in diameter and 1.5 m in length was towed vertically at constant speeds through the towing tank to simulate uniform current condition. Some key VIV parameters such as amplitude over diameter, lift and drag coefficients are presented against a non dimensional parameter known as reduced velocity to understand the effects of VIV on two degree of freedom system.The relative magnitude of the super-upper response branch vibration amplitudes are emphasised in this particular study. Results of this paper can be used as validation materials for CFD analysis that is very important to design riser system for oil and gas industry, also mentioned experiment procedure can be treated as a guide for future endeavour to perform similar kind of tests.

Abstract: This study is an approach to investigate the transformations curve of gearing safety. Two types of failure can occur on a gear namely the bending stress and the surface pitting failure. There are many standards for gearing in used worldwide such as AGMA, JGMA, ISO, DIN, etc. but the focus of this study will be on AGMA standard. The main data for this study is the torque value applied which can be distinguished into causing bending strength or surface pitting failure. The Autodesk Inventor spur gear component accelerator was used as a tool for data acquisition based on the AGMA standard of calculations. Two gear materials with high value of allowable contact stress compared to its allowable bending stress was chosen for the study as they are predicted to have a transformation curve from surface durability to bending strength when its torque values are plotted against number of teeth. This is then repeated on various gear modules for both materials to obtain a series of combination curves useful in determining the maximum torque that can be applied on the spur gear before failures occur either by bending stress or surface pitting depending on the curve.