Advanced Materials Research Vols. 488-489

Abstract: Measurement of mechanical properties is very important in material science research area. Shear mechanical properties can be obtained from ultrasound vibromery method. Generally, ultrasound vibrometry is based on Voigt model which cannot describe some viscoelastic material accurately. Our method is based on Zener model, and more precise description of mechanical behavior can be measured. In our work, finite element method and experiment are conducted to validate our approach. Shear wave velocities at harmonics in finite element simulation are very close to the theoretical value and the fitting results from experiment demonstrate that our method has better ability to characterize some materials.

Abstract: The Chemical mechanical planarization (CMP) process has become a primary planarization technique required for the manufacture of advanced integrated circuit (IC) devices. As the feature size of IC chips shrinks down to 65 nm and below, the role of CMP as a robust planarization process becomes increasingly important. In this work, we evaluated surface roughness of CMP pad to correlate the roughness with CMP performance such as material removal rate (MRR) and pad lifetime. Pad surface was analyzed by 3-dimensional profiler and scanning electron microscope (SEM). We found that MRR could be varied with the pad life time and roughness. We also found that suitable roughness range is exist to get stable CMP performance. Finally, we introduced ‘pre-conditioning’ method to manage the roughness of CMP pad to get stable CMP performance at the initial pad life time.

Abstract: Inclined surfaces are commonly used in the aerospace and die/mold industries. For machining this kind of surfaces, many aspects have to be considered as machinability considerations including milling strategies, machining parameters and etc. In machining, achieving better quality is challenging task. Various tool-path strategies during milling operation leads to variable surface roughness on machined samples. The objective of this study is to analyze different machining strategies in 3-axis milling of a typical curved geometry part. The machining parameters used in this study, are cutting speed, feedrate and stepover. This paper also presents an approach to develop a mathematical model for measuring Scallop height size and distribution for different machining strategies to show that Scallop height size has direct relation with Surface roughness measurements in each strategy. Finally the optimized strategy based on the results was determined.

Abstract: Sample and oven factors are important in determining the magnitude and uniformity of power absorption. The effects of these parameters on water and food materials have been studied. However, interaction of microwave with minerals is poorly understood. In this research, the effect of sample and oven parameters such as sample volume and placement of sample on microwave heating of water and an iron ore material were studied and obtained data were compared. The results showed that for water heating, with increasing in sample volume from 200 to 1000cm3 the microwave energy absorbed by water was increased from 71.27 to 100%, also with increasing in sample surface area from 50.24 to 78.50 cm2 the microwave, energy absorbed by water was increased from 76.36 to 89.09%. In iron ore heating, the surface area is effective parameters only. When iron ore sample volume was increased without increasing in surface area, the microwave absorption was constant while with increasing in sample surface area from 50.24 to 126.6 cm2, the microwave energy absorbed by iron ore was increased from 36.6 to 61.82%. The maximum temperature for iron ore material was occurred at 5.7 cm distance from the center while the maximum temperature for water sample was occurred at 5cm distance from the center

Abstract: The purpose of this research was to investigate the effects of main factors on the surface roughness in face milling process palmyra palm wood and coconut wood by computer numerical controlled milling machine and using shell end mill cutting tools 6 edges. The main factors including speed, feed rate, depth of cut and angle of cut were investigated for the optimum surface roughness. The result of preliminary trial showed that the depth of cut and the angle of the cut had no effect on surface roughness. It was found from the experiment that the factors affecting surface roughness were feed and speed, with tendency for reduction of roughness value at a lower feed rate and greater cutting speed. Therefore, in the facing process for palmyra palm wood it was possible to determine a face milling condition by means of the equation R_a = 0.954 + 20.4 Feed + 0.00126 Speed. This equation was employed at a limited speed of 800-1200 rpm, and the feed rate of 0.03-0.05 mm/tooth. The result from the experiment of the mean absolute percentage error of the equation of surface roughness is 6.10% which is less than the margin of error, and is acceptable. For coconut wood it was found from the experiment that the factor affecting surface roughness was feed rate and cutting speed, with tendency for reduction of roughness value at lower feed rate and greater cutting speed. Therefore, in the face milling coconut wood it was possible determine a facing condition by means of the equation R_a = 4.72 - 0.000864 Speed + 0.00443 Feed. Leading this equation goes to use is in limitation cutting speed 1000-2000 rpm at feed rate 100-300 mm/min. The result from the experiment of mean absolute percentage error of the equation of surface roughness is 4.64% which is less than the margin of error, and is acceptable. As a result, the selection of optimal machining parameters can be greatly benefited to the Coconut wood furniture manufacturing industry in terms of productivity improvement.

Abstract: The newly engineered metal matrix composite (MMC) of aluminium 7075 reinforced with 10 wt% of Al2O3 particles were prepared by stir casting method. Electrical discharge machining (EDM) was employed to machine MMC with copper electrode. The experiment plan adopts face centered central composite design of response surface methodology. Analysis of variance was applied to investigate the influence of process parameters and their interactions viz., pulse current, gap voltage, pulse on time and pulse off time on material removal rate (MRR), electrode wear ratio (EWR) and surface roughness (SR). The objective was to identify the significant process parameters that affect the output characteristics. Further a mathematical model has been formulated by applying response surface method in order to estimate the machining characteristics such as MRR, EWR and SR.

Abstract: Bulk metallic glasses have interesting mechanical properties, such as high strength up to 5 GPa, high elastic strain and many other additional desirable properties. However, BMGs beyond the elastic region fail catastrophically on one dominant shear band and show little macroscopic plasticity in an apparently brittle manner. Nano-crystallized BMGs have been found to possess better ductility comparing with brittle parent BMGs. Annealing treatment of glassy alloys is a useful method to prepare bulk nano-crystalline alloys. In the present study, the crystallization trend of the FeCoCrMoCBY alloy which is claimed to have the best glass forming ability was studied in various times in temperature ranges of a) between Tg (glassy temp.) and Tx1 (first crystallization temp.), and b) between Tx1 and Tx2 (second crystallization temp.). The influences of different annealing time and temperatures on the microstructure and microhardness of Fe₄₁Co₇Cr₁₅Mo₁₄Y₂C₁₅B₆ BMG are reported in this paper.

Abstract: Quality is the collection of features and characteristics of a product that contribute to its ability to meet given requirements. The quality of a weld joint is directly influenced by the welding parameters during the welding process. Often, a common problem that has been faced by the manufacturer is the control of the process parameters to obtain a good welded joint. Quality level is denoted as the probability of conformance and is a function of system variables and system specification. The present work is aimed to improve the quality of the weldment in SAW using Weighted Principal Component based Taguchi method. Three process parameters such as voltage, carriage speed and stand of distance are identified to carry out the study. Mechanical properties such as tensile strength and hardness are considered to be the response parameters in the present study.

Abstract: Copper based metal matrix composite reinforced with Boron Carbide is a newly developed Electrical Discharge Machining (EDM) electrode showing better performance than the conventional copper based electrode. Right selection of machining parameters such as current, pulse on time and pulse off time is one of the most important aspects in EDM. In this paper an attempt has been made to develop mathematical models for relating the Material Removal Rate (MRR), Tool Removal Rate (TRR) and Surface roughness (Ra) to machining parameters (current, pulse-on time and pulse-off time). Furthermore, a study was carried out to analyze the effects of machining parameters on various performance parameters such as, MRR, TRR and Ra. The results of Analysis of Variance (ANOVA) indicate that the proposed mathematical models, can adequately describe the performance within the limits of the factors being studied. Response surface modeling is used to develop surface and contour graphs to analyze the effects of EDM input parameters on outer parameters.

Abstract: The effect of process parameters namely peak current, pulse on time and flushing pressure on electrical discharge machining (EDM) of titanium alloy (Ti–6Al–4V) were investigated by using three different tool electrode materials namely copper, brass, and aluminium. Kerosene is used as dielectric. The process parameters for machining Ti6Al4V are varied at three levels by using Taguchi's orthogonal array table. The responses such as Metal Removal Rate (MRR), Tool Wear Rate (TWR), and Surface Roughness (SR) are measured and the most significant parameter was confirmed by ANOVA (Analysis Of Variance). The test result shows that copper electrode material possesses higher MRR, less TWR as compared to brass and aluminium. Brass and copper tools has good surface finish as compared with aluminium. The finest electrode material for machining of Ti6Al4V alpha beta alloy in EDM process was in the order of copper, brass and aluminium.