Aluminium honeycomb sandwich panels have potential applications as a protective mechanism that can be used to prevent failure of an important structure subjected to impact loading. Therefore it is important to fully understand the resistance of the sandwich panels subjected to impact loading conditions. The main objective of this work was to study the resistance of sandwich panels with different aluminium honeycomb cores, air sandwich panels (no core between the two face sheets) and monolithic plates of equivalent mass subjected to impact from foam projectiles. The deformation and the elastic spring-back of the honeycomb sandwich panels and the monolithic plates have been compared and discussed. The resistance of the panels and plates has been quantified by their back-face deflection with respect to the projectile impulse. Five different types of aluminium honeycombs have been used as the core material. The front-face sheet and the back-face sheet of the honeycomb sandwich panels are made of aluminium plate with 1 mm thickness. Cylindrical ALPORAS
This paper presents an investigation on the effect and optimization of machining parameters on the kerf (cutting width) and material removal rate (MRR) of titanium alloy (TI-6AL-4V) using wire electrical discharge machining WEDM with a brass wire diameter of 0.5mm. The experimental studies were conducted under varyingpulse-off time, peak current, wire feed and wire tension. The settings of machining parameters were determined by using Taguchi experimental design method. The multiple performance characteristics based on the statisticalbased analysis of variance (ANOVA) and grey relational analysis (GRA) was attempted. Analysis of variance was used to study the significance of process parameters on grey relational grade (GRG) which showed the most significant factor. The GRG obtained from the GRA was used to optimize the WEDM process. The optimum process parameters are determined by the GRG as the overall performance index. To validate the findings, confirmation experiment had been carried out at the optimal set of parameters, and the predicted results were found to be in good agreements with experimental findings. Improved machining performance in the WEDM process has been achieved by using this approach.
Cellular material such as aluminium foam has been considered as a potential material for energy absorption upon impact and blast loadings. One of the most important properties that contribute to this feature is the densification strain. At high impact velocity, prediction of the densification strain from quasi-static engineering stress-strain curve has been found inadequate. Furthermore, theoretical prediction using the equation proposed by Reid et al. always over-predicts the dynamic crushing stress. Formation of the shock wave at high impact velocity is believed to further increase the densification level of the foam. However, this effect is disregarded when determining the densification strain quasi-statically. The present study aims to address this issue by determining the densification strain experimentally from impact tests. Forty cylindrical aluminium foams with three different lengths were used as projectiles and were fired towards a rigid load cell by using a gas gun. The peak forces generated from the impact were recorded and analysed. The experimental densification strains were determined physically by measuring the deformation of the foam projectiles after the tests. It is concluded that, at high impact velocity, the densification strain varies with the initial impact velocity. Therefore an appropriate value of densification strain needs to be used in the equation of dynamic crushing stress for a better approximation.
This paper presents an investigation on influences and multiple optimizations of wire-electrical discharge (WEDM) machining performances such as cutting rate, material removal, surface roughness and kerf width processed on titanium alloy material. The experimental studies were conducted under varying machining parameters namely pulse-off time, peak current, wire tension and wire feed. The experimental works were designed base on Taguchi design of experiment. The optimum multi-objective performance characteristics was determined using analysis of variance (ANOVA) coupled with grey relational analysis (GRA). ANOVA was used to study the significance of process parameters on grey relational grade which showed the most significant factor. The grey relational grade obtained from GRA was used to optimize the wire-electrical discharge machining process. To validate the findings, confirmation experiment had been carried out using the optimal parameters and the predicted results were found in good agreements with experimental finding. Improved machining performance in the wire electrical machining process has been achieved by using this approach.
Most uncemented total hip replacements (THR) rely on press-fit for the initial stability and thus lead to the secondary fixation which is biological fixation. Choosing the accurate interference fit may have a great effect on implant stability and implant loosening prevention. Implant loosening is the most reported problem where it leads the increasing of micromotion at the bone-implant interface due to insufficient primary fixation. By having sufficient stability or fixation after surgery, minimal relative motion between the prosthesis and bone interfaces allows osseointegration to occur. Therefore, it will provide a strong prosthesis-to-bone biological attachment. The aim of this study was to evaluate the effect of bone-implant interface for uncemented hip implant. In this study, a three-dimensional model of hip implant was designed and analysed by using commercial Finite Element Software namely, ANSYS WORKBENCH V15 software in order to investigate the bone-implant interface effect using the chosen implant design. The value of interference fit (δ= 0.01, 0.05, 0.10 and 0.50 mm) and coefficient of friction (δ= 0.15, 0.40 and 1.00) were used to simulate the bone-implant interface. It was found that the interference fit of 0.50 mm was sufficient to achieve the primary fixation and also the best fitting; thus, the implant loosening can be minimized. The interference fit of 0.50 mm was the minimal value to achieve fixation, while the coefficient of friction did not affect the bone-implant interface.
Wire electrical discharge machining is a material removal process of electrically conductive materials by the thermo-electric source of energy. This kind of machining extensively used in machining of materials with highly precision productivity. This work presents the machining of titanium alloy (TI-6AL-4V) using wire electro-discharge machining with brass wire diameter 0.5mm.The objective of this work is to study the influence of three machining parameters namely peak current, pulse off time and wire tension to cutting rate, material removal rate, surface roughness and kerf width followed by suggesting the best operating parameters towards good machining characteristics. A full factorial experimental design was used with variation of peak current, feed rate and wire tension, with results evaluated using analysis of variance techniques. Parameter levels were chosen based on best practice and results from preliminary testing. Main effects plots and percentage contribution ratios are included for the main factors and their interactions.
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