Applied Mechanics and Materials Vol. 315

Abstract: This paper presents a review of recent developments of nonlinear constitutive material models for the applications in high speed ballistic impact of projectile into several types of targets. The objective is to comprehend some numerical approaches that have been proposed and used in the technical literatures especially regarding bullet-target interaction. Attention is given on the application of several types of computational constitutive models and simulations used to represent the projectile characteristic, ballistic penetration, failure modes in target and deformation pattern. This paper serves as a concise source to identify future direction in the area of computational mechanics of high speed collisions and provides brief literatures for those interested in conducting research into the topic.

Abstract: Carbon fiber reinforced plastic (CFRP) composites are often used in combination with other materials, requiring it to be machined during fabrication of a structure. Drilling as the most common machining process of CFRP is complex often results in delamination of the composites. The complexity is contributed by CFRP composites fiber orientation which can be of unidirectional or quasi-isotropic type depending on the applications. This study reviews the machinability of CFRP composites by considering fiber orientation and machining conditions used during drilling. Their relation with machining thrust force which leads to delamination is the central theme. An insight in obtaining delamination-free holes is also discussed.

Abstract: Accuracy of machined component is one of the challenging tasks for manufacturer. In the aerospace industry, machining process is widely used for fabrication of unitized-monolithic component that contains a thin-walled structure. During machining, the cutting forces cause deflection to the thin-wall section, leading to dimensional form errors that cause the finished part to be out of specification or failure. Most of the existing research for machining thin-wall component only concentrated on the process planning and the effects of cutter geometric feature is often neglected. Tool geometric feature has a direct influence on the cutting performance and should not be neglected in the machining consideration. This paper reports on the effect of helix angle on the magnitude of wall deflection. The established effects will be used for the development of high performance cutting tool for specifically machining thin-wall component.

Abstract: Carbon fiber reinforced plastics (CFRP) composites as high performance material in aerospace industry. The application of laser technology to cut the CFRP shows promising advantages. The present study focuses the effect of focal point distance on the kerf width, HAZ, taper angle and morphology surfaces when cutting CFRP using laser process. Experiments have been conducted on CFRP and microstructure of the cross-section of the HAZ during cutting was analyzed. The results showed that focal position gave a significant effect on the cutting characteristic.

Abstract: This research is related to thermal efficient water heating system, specifically to improve the water heating system that exists nowadays. The goal of this research is to improve the current water heating system by using solar heat as the energy source to heat the water. The focus is to improve the thermal efficiency by adding different thermal boxes as the absorber bed. By implementing the black body and radiation concept, the air trapped in the box is heated. The trapped air then increases the collisions between the molecules and directly increases the temperature inside the box, higher than the outside environment. Based on a daytime experimental result revealed steel thermal box is better to be used for tropical weather like Malaysia.

Abstract: This research is related to thermal efficient water heating system, specifically to improve the water heating system that exists nowadays. The goal of this research is to improve the current water heating system by using solar heat as the energy source to heat the water. The focus is to improve the thermal efficiency by adding different thermal boxes as the absorber bed. By implementing the black body and radiation concept, the air trapped in the box is heated. The trapped air then increases the collisions between the molecules and directly increases the temperature inside the box, higher than the outside environment. Based on night experimental results revealed steel thermal box is better to be used for tropical weather like Malaysia.

Abstract: The combustion characteristics of compressed natural gas (CNG) in a direct microchannel-injection engine under various operating conditions were investigated. In this study, a novel idea for direct CNG microchannel injection was realized with spark plug fuel injector (SPFI). It is a device developed to convert engine to CNG direct injection (DI) operation with minimal cost and technical simplicity. It was installed and tested on a Ricardo E6 single cylinder engine with compression ratio of 10.5:1 without modification on the original engine structure. The engine test was carried out under various operation conditions at 1100 rpm. Burning rates of CNG were measured using normalized combustion pressure method by which the normalized pressure rise due to combustion is equivalent to the mass fraction burned (MFB) at the specific crank angle. The results showed that the MFB of CNG direct injection is substantially faster but initially slower than the ones of port injection. The optimal fuel injection and ignition timings are 190 °CA ATDC and 25 °CA BTDC respectively. The optimal injection pressure was 6 MPa. Combustion durations were not changed with different injection pressures but ignition delay was affected. There was no direct correlation between injection pressure and ignition delay which is most probably due to the effect of charge flow difference. Changing mixture stoichiometry affects the magnitude of ignition delay. Combustion duration, on the other hand increases with leaner mixture.

Abstract: ntegrating sustainable product design into the design process has been acknowledged nowadays by many companies for producing sustainable products. The integration should be implemented during the early stage of product development process so that the sustainability of the product can be evaluated before manufacturing the product. Although a number of studies have been conducted on the integration in many aspects along with many approaches, evaluation of the sustainability of the product during its total life-cycle while it is being designed has not been comprehensively investigated. In this paper, Analytic Hierarchy Process (AHP) is used to evaluate product design element concept during conceptual design stage by providing a weightage of sustainability metrics throughout the total life-cycle of product and finalize the preferred product design configuration by selecting the highest sustainability index of the design element concept. The approach is useful for product designers to design many concepts of product design elements and then to select the most likely sustainable design element to configure in one complete product. An example of an armed chair is used to demonstrate this approach.

Abstract: In hydrodynamic lubrication, the pressure condition of the fluid is critical to ensure good performance of the lubricated machine elements such as journal bearings. In the present study, an experimental work was conducted to determine the effect of oil supply pressure on pressure profile around the circumference of a journal bearing. A journal diameter of 100mm with a ½ length-to-diameter ratio was used. The oil supply pressure was set at three different values (0.3, 0.5, 0.7 Mpa) and the circumferential pressure results for 400, 600 and 800 RPM at different radial loads were obtained. It was observed that the maximum pressure values were affected by changes in oil supply pressure.

Abstract: For many years, researcher have focused on developing a medical part of human body from polymer as to replace metal. This report described the mechanical characteristic of biodegradable Polycaprolactone (PCL) blend with nanoMontmorillonite (MMT) and Hydroxyapatite (HA). The amount of nanoMMT is varies from 2 to 4 by weight % meanwhile the amount of HA is fixed to 10 by weight percentage (wt %). The addition of nanoMMT and HA filler is to tune and indirectly improve the mechanical properties of PCL. These are proven by carrying out the tensile, and also flexural test for samples which is injected from injection molding machine. Both the tensile and flexural test are conducted using Shimadzu AG-I Unversal Testing Machine with 10kN capacity. From the analysis it is found that overall PCL/MMT/HA composites gives better result in both tensile and flexural analysis compare to PCL/MMT composite. PCL/MMT/HA composite with 2 wt% of MMT and 10 wt% of HA have indicated the highest tensile modulus, meanwhile PCL/MMT/HA composite with 4 wt% MMT and 10 wt% HA have plotted the highest flexural strength and modulus value.