D. Sujan

Effect of Bond Layer on Bimaterial Assembly Subjected to Uniform Temperature Change

When two thin plates or layers are bonded together, an extremely thin bond layer of third material exists between the two layers. This research work examines the effect of bond layer on the interfacial shearing and peeling stresses in a bimaterial model. Earlier papers on this topic are based on several mutually contradictory expressions for the shear compliance of the bond layer. This paper is aimed at resolving this ambiguity and presents derivation of shear compliance on a rational basis. A numerical example is carried out for a silicon-copper system with a gold-tin solder bond layer. The results obtained are likely to be useful in interfacial stress evaluation and physical design of bimaterial assemblies used in microelectronics and photonics applications.

Performance of Solder Bond on Thermal Mismatch Stresses in Electronic Packaging Assembly

Thermo-mechanical stresses have been considered one of the major concerns in electronic Packaging assembly structural failure. The interfacial stresses are often caused by the thermal mismatch stresses induced by the coefficient of thermal expansion (CTE) difference between materials, typically during the high temperature change in the bonding process. This research work examined the effect of bond layer on thermal mismatch interfacial stresses in a bi-layered assembly. The paper verified the existing thermal mismatch solder bonded bi-layered analytical model using finite element method (FEM) simulation. The parametric studies were carried out on the effect of change of bond layer properties in order to provide useful references for interfacial stress evaluation and the electronic packaging assembly design. These parameters included CTE, temperature, thickness, and stiffness (compliant and stiff bond) of the bond layer. The recent development on lead free bonding material was being reviewed and found to have enormous potential and key role to address the future electronic packaging assembly reliability.

Surface Roughness Model when Machining Aluminum Nitride Ceramic with Two Flute Square End Micro Grain Solid Carbide End Mill

This research presents the performance of Aluminum Nitride ceramic in end milling using two flute square end micro grain solid carbide end mill under dry cutting. Surface finish is one of the important requirements in the machining process. This paper describes mathematically the effect of cutting parameters on surface roughness in end milling process. The quadratic model for the surface roughness has been developed in terms of cutting speed, feed rate, and axial depth of cut using the response surface methodology (RSM). Design of experiments approach was employed in developing the surface roughness model in relation to cutting parameters. The predicted results are in good agreement with the experimental results within the specified range of cutting conditions. Experimental results showed surface roughness increases with increase in the cutting speed, feed rate, and the axial depth of cut.

The study of coated carbide ball end milling tools on inconel 718 using numerical simulation analysis to attain cutting force and temperature predictive models at the cutting zone

The unique properties of Inconel 718 make it a challenging material to machine especially in ball end milling operations due to high cutting force and temperature concentrated at the cutting zone. These essentially lead to accelerated tool wear and failure resulting in high costs and loss of production. In this research, finite element numerical simulation was performed using AdvantEdge to simulate ball end milling using an 8mm TiAlN coated carbide tool. Response Surface Methodology (RSM) is applied by using a 3 level 3 factorial Box-Behnken design of experiment with different combinations of cutting speed, feed rate, and depth of cut parameters with a selected range of parameters to simulate finishing operations. Temperature contour from finite element analysis showed that the highest temperature occurs near the depth of cut line just before the chip separates from the workpiece. Using multiple linear regression, a quadratic polynomial model is developed for maximum cutting force and a linear polynomial model peak tool temperature response respectively. Analysis of Variance (ANOVA) showed that feed rate had the most significance for cutting force followed by depth of cut. Also, cutting speed was found to have little influence. For peak tool temperature, cutting speed was the most significant cutting parameter followed by feed rate and depth of cut.

Hybrid Composite Using Natural Filler and Multi-Walled Carbon Nanotubes (MWCNTs)

This paper presents an experimental study on the development of hybrid composites comprising of multi-walled carbon nanotubes (MWCNTs) and natural filler (oil palm shell (OPS) powder) within unsaturated polyester (UP) matrix. The results revealed that the dispersion of pristine MWCNTs in the polymer matrix was strongly enhanced through use of the solvent mixing method assisted by ultrasonication. Four different solvents were investigated, namely, ethanol, methanol, styrene and acetone. The best compatibility with minimum side effects on the curing of the polyester resin was exhibited by the styrene solvent and this produced the maximum tensile and flexural properties of the resulting nanocomposites. A relatively small amount of pristine MWCNTs well dispersed within the natural filler polyester composite was found to be capable of improving mechanical properties of hybrid composite. However, increasing the MWCNT amount resulted in increased void content within the matrix due to an associated rapid increase in viscosity of the mixture during processing. Due to this phenomenon, the maximum tensile and flexural strengths of the hybrid composites were achieved at MWCNT contents of 0.2 to 0.4 phr and then declined for higher MWCNT amounts. The flexural modulus also experienced its peak at 0.4 phr MWCNT content whereas the tensile modulus exhibited a general decrease with increasing MWCNT content. Thermal stability analysis using TGA under an oxidative atmosphere showed that adding MWCNTs shifted the endset degradation temperature of the hybrid composite to a higher temperature.

Machinability of Aluminum Nitride Ceramic Using TiAlN and TiN Coated Carbide Tool Insert

This research presents the performance of Aluminum nitride ceramic in end milling using using TiAlN and TiN coated carbide tool insert under dry machining. The surface roughness of the work piece and tool wear was analyzed in this. The design of experiments (DOE) approach using Response surface methodology was implemented to optimize the cutting parameters of a computer numerical control (CNC) end milling machine. The analysis of variance (ANOVA) was adapted to identify the most influential factors on the CNC end milling process. The mathematical predictive model developed for surface roughness and tool wear in terms of cutting speed, feed rate, and depth of cut. The cutting speed is found to be the most significant factor affecting the surface roughness of work piece and tool wear in end milling process.

Topology Optimization of Beam Structures with Various End and Loading Conditions

Topology optimization deals with optimum material (mass) distribution within a design domain to find optimal lay-out of a structure subjected to certain boundary and loading conditions. Topology optimization can be used to address conflicting requirements, such as light weight and high-strength/stiffness design. In this paper, a simulation program to analyze topology optimization of beam structures with seven different end conditions and three types of loads (single point load, two point loads and uniformly distributed load) is developed using MATLAB code adapted from Sigmunds 99 line topology optimization code. Furthermore, the program has been enhanced with a graphical user interface for ease of use. Using the developed system, it is possible to analyze the effect of different parameters.

Thermo-Mechanical Stress Analysis in Electronic Packaging with Continuous and Partial Bond Layer

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.

Wear Properties of Oil Palm Cellulose Fibre Reinforced Polymer Composites

This paper attempts to explain the motion behaviour of the marine riser coupled to a drill string when the vortex induced vibration (VIV) is involved. Vibrations have been reported to have a major effect on the drilling performance, affecting the rate of penetration (ROP), causing severe damages to the drilling tools and also reduces the efficiency of the drilling process. There are two major components of drilling tools that are subjected to vibration, namely the marine riser and the drilling string. Analysis of vibration in the marine riser and drill string are two topical areas that have individually received considerable attention by researchers in the past. Though these two subjects are interrelated, borne by the fact that the marine riser encapsulates and protects the drill pipe, there have been few attempts to investigate them together as a unity. Due to the complexities of the models, simplified assumptions were made in order to undertake the investigation by using staggered approach. The results were compared with the experimental and simulation data from the open literature. It was found that the maximum displacement with negative damping occurs at low frequency and rotation speed.

Modeling and Simulation of a Heat Recovery Steam Generator Using Partially Known Design Point Data

In a cogeneration or combined heat and power plant, a heat recovery steam generator (HRSG) helps achieve overall thermal efficiency as high as 80%. The purpose of this study is to model and simulate the HRSG given partial design point data. The pinch and approach temperatures are optimized within generally accepted range. In order to satisfy the energy conservation equation, tuning parameters are used for the overall heat transfer coefficients corresponding to the evaporator and economizer. For the off-design simulation, the values of pinch and approach temperatures are adjusted until the modeling error is within a set limit. The effect of mass flow rate on the heat transfer coefficient is accounted for & by employing empirical relations. A 12 Ton/hr natural circulation HRSG was considered as a case study. The validation test on inlet temperatures of the exhaust gas and feed water to the economizer demonstrated relative percentage errors of 0.4246% and 1.8776%, respectively. The model can be used for fault detection and diagnostic system design, performance optimization, and environmental load assessment.