Applied Mechanics and Materials Vols. 465-466

Abstract: Interfacial stress due to thermal mismatch in layered structure has been considered as one of the major causes of mechanical failure in electronic packaging. The mismatch due to the differences in coefficient of thermal expansion (CTE) of the materials in multi-layered structure may induce severe stress concentration to the electronic composites namely interfacial delamination and die cracking. Therefore, the studies and evaluation of interfacial stress in electronic packaging become significantly important for optimum design and failure prediction of the electronic devices. The thermal mismatch shear stress for bi-layered assembly can be analyzed by using the mathematical models based on beam theory. In this study, Finite Element Method (FEM) simulation was performed to an electronic package by using ANSYS. The shear stress growth behavior at the interface of the bonded section was studied with the considerations of continuous and partial bond layers in the interfaces. Based on the analysis, it can be observed that the partial bond layer with small center distances can be simplified as a continuous bond layer for bi-layered shearing stress model analysis.

Abstract: Selection of the most suitable Rapid Prototyping (RP) and manufacturing process for a specific part creation is a difficult task due to the development of RP processes and materials. Most current RP processes can build with more than one type of material. The paper presents the evaluation on Acrylonitrile Butadiene Styrene (ABS) and Polylactic acid (PLA) part produced from Fused Deposition Modeling (FDM) as a master pattern for Investment Casting (IC) process. The main purpose of this research is to evaluate the dimensional accuracy and surface roughness for hollow and solid part of FDM pattern for IC process with different layer thickness. The value were taken for both before and after the casting process. Results show that model fabricated with hollow internal pattern structure (ABS material) that produced by low layer thickness is better than other models in terms of its dimensional accuracy (-0.19666mm) and surface roughness (1.41μm). Even though the ABS built part performed better as the model, the PLA build part produces better overall casting result. Final part fabricated with solid pattern (PLA material) that produced by high layer thickness is better than other final parts which its dimensional accuracy (-0.12777mm) and surface roughness (3.07μm).

Abstract: In milling operation, Computer Numerical Control (CNC) milling machine has been recognized as one of effective solutions for high productivity, efficiency, and precision. However, the existing CNC milling machine has contributed to ergonomics-related problems such as awkward working posture. The aim of this study is to redesign the existing CNC milling machine by considering working posture of the machinist. This study performed questionnaire survey to determine ergonomics feature requirements from the machinist. The requirements of the machinist are then translated using Quality Function Deployment (QFD) to obtain technical specifications of new design CNC milling machine. The working posture of machinist during operating the existing CNC milling machine and the redesigned CNC milling machine was assessed using Rapid Upper Limb Assessment (RULA). Based on the analysis, the redesigned CNC milling machine has improved the working posture as shown by low score of RULA. This study concluded that by considering the ergonomics feature requirements to the design of CNC milling machine enabled the machinists to perform milling operation in safe working posture. This study suggests that environmental factors should be considered in the future research works.

Abstract: Various research programmes have been conducted examining cermet coatings regarding wear, corrosion and the combination of both (erosion-corrosion and abrasion-corrosion). Several methods have been used to deposit cermet coatings, the most common being thermal spraying or hard facing (weld overlaying). In the current work, the micro-scale abrasion of coatings deposited using both high velocity oxy-fuel (HVOF) thermal spraying and weld overlay techniques are compared. The weld-overlayed WC-nickel alloy systems have the carbide particles are typically two orders of magnitude larger than in the sprayed coatings. Micro-scale abrasion tests were performed using silicon carbide, alumina and silica particle slurries with abrasive particle sizes in the range of 2-10 μm in all cases. Wear rates were determined and the wear scars were examined using SEM to elucidate the dominant wear mechanisms. The wear rate is generally observed to decrease with decreasing abrasive hardness from silicon carbide, followed by alumina and silica.

Abstract: In the modern world with an extensive improvement of science and technologies, alumina (Al₂O₃) ceramics have been identified as one of the usable materials in production of electronic components. This project attempts to investigate the magnesite (MgCO₃) effect to Al₂O₃ sintering for heat sink application. The effect of MgO percentage varying from 0% to 50% has been in investigated, emphasizing on the flexural strength test, thermal conductivity test, elastic modulus test, shrinkage percentage and density measurement. The result revealed that the MgO give an effect to the final thermal conductivity and mechanical properties of Al₂O₃ material at high sintering temperature (i.e. at temperature of 1600°C). Throughout an X-ray diffraction (XRD) analysis of Al₂O₃ and MgO compositions, it was revealed that spinel, periclase and corundum phases exist for all sintered temperature which contributes to strengthen grain boundaries and improved mechanical properties.

Abstract: Aluminium alloys is widely applied in heat sink but its application of heat absorption is still unsatisfied. While, Aluminum Nitride (AIN) was discovered as another option for heat sink application because of its great thermal conductivity and it also has high electrical conductivity at high temperature. Thus, the mechanical and chemical properties of a sintered mixed powder of Alumina and AIN are investigated experimentally. There are five different compositions of mixed powder of Alumina-AIN and sintered at three different sintering temperatures which are 1400°C, 1500°C and 1600°C. As applying a high sintering temperature on samples inducted great flexural strength and increase it modulus of rupture. High sintering temperature (1600°C) also affected the materials microstructure as the particle was arranged closely between each other and reduces the amount of porosity. The application of high temperature in the mixture of AIN with Alumina reduces the occurrence of flaws like cracking and accordingly improves the strength. These combination of Alumina-AIN brought acceptable result in thermal conductivity value analysis and as well enhancing the thermal conductivity.

Abstract: This research is carried out to study the feasibility of the gravity effects on curing position of the laminated composite structures to enhance the curing space needed. Vertical cured laminate having almost similar properties with common horizontal cured laminate able to save much space in composite industry especially for developing Small and Medium Industry (SMI). Horizontal cured laminates filled up spaces in which SMI lack of. Polyesters and E-glass fibers were used as the raw material in this research. Vacuum bagging technique was used to suck out the excess resin during lay-up to avoid any voids and air inside laminate and cured at different angle position in room temperature for 24 hours. Seven samples of laminated composite were fabricated and cut into specific dimension in accordance to ASTM standard. The aim of the research was to investigate the density property of the thermosetting laminated composite by curing the laminate at different angle using vacuum bagging technique. From the testing, SN6 had the same density value with control sample, SN1 that had value of 1.46 g/cm³.

Abstract: Moisture absorption is a very important factor in polymers and composite materials used for hull manufacture and stability in marine environment. High water absorption of the material will affects the mechanical properties and stability in composite. This research is carried out to study the feasibility of the gravity effects on curing position of the laminated composite structures to enhance the curing space needed. Vertical cured laminate having almost similar properties with common horizontal cured laminate able to save much space in composite industry. Horizontal cured laminates filled up spaces in which SMI lack of. Polyesters and E-glass fibers were used as the raw material in this research. Vacuum bagging technique was used to suck out the excess resin during lay-up to avoid any voids and air inside laminate and cured at different angle position in room temperature for 24 hours. Seven samples of laminated composite were fabricated and cut into specific dimension in accordance to ASTM standard. This paper will discuss about the investigation on the water absorption and thickness swelling of the thermosetting laminated composite by curing the laminate at different angle using vacuum bagging technique. From the testing, SN6 and SN7 shows to have good water resistant in physical properties.

Abstract: Manufacturing of beverage cans is porcessed by using multi-stage ironing following deep drawing from the sheet material of aluminum and steel. An earing profiles are develops during deep drawing of cylindrical cup due to the planar anisotropic properties of sheet. Therefore, the analysis of earing is important to evaluate and control the development of earing. This paper describes a simulation of the cold ironing process in the forming cylinder cap. The ironing process in this study was focused on the prediction of height increasing, earing and thinning. Two different materials of aluminum AA5042 and AKDQ steel were selected for comparison. The results show that the increasing of cup height was in the same trend.

Abstract: The purpose of this research is to study the accuracy of RP FDM Process. This research involves varying two parameters in building up the prototype which is the buildup angle and the sparse for each layer (volume of parts). The varying parameters were used in the FDM process for three types of specimen (profiles) which is the Cube, Cylinder and Pyramid. The varying parameters are the build up angle of 30⁰, 65⁰ and 90⁰ and for the types of sparse, there are three types of sparse used which is Low Density (LD), High Density (HD) and Solid Type. The results of the dimensional accuracy are analyzed by calculating the percentage of difference of the dimensional measurement for the specimen and the actual dimension of it. The lesser difference, the better the dimensional accuracy. The conclusion of this study is the less complicated specimen shape for the FDM process, the more accurate of the dimensional accuracy with the optimum build up angle of 30⁰ or less and the optimum type of sparse of Low Density Type (LD).