This study is to analyze and test the extrusion process of a hollow spur gear and a solid helical product with magnesium alloy. In the hollow spur gear part, firstly, a design criterion to determine the forming parameters is proposed. Then, the Finite Element Analysis is used to simulate the flow pattern of the billet from separating channel, welding chamber to die bearing part. From a series of simulation results, the effect of separating channel length, mandrel entrance angle, welding chamber height, etc. on the radial filling ratio, welding pressure, extrusion load, etc. are found. By using the Taguchi Methods, we can find the most important parameters. Finally, a better die geometry is designed to obtain a sound product. In the helical product part, the Finite Element Analysis is used to get the understandings of radical filling ratio of magnesium alloy in the helical zone. Then, a better die geometry is designed from the results of analyses. Finally, hot extrusion experiments of a hollow spur gear and a solid helical product are conducted. The experimental values of the extrusion load and the product¡¦s dimension are compared with the analytic values to verify the validity of the analytic models.

ABSTRACT This thesis gathered the actual Burn-In (BI) data from one of the leading cooperation in the semiconductor industry, and analyzed the major factors¡¦ impact on BGA package solder ball deformation. The Taguchi Method was used for these analyses, and the commercial statistic software MiniTab14 was widely used on this thesis. The solder ball stress was analized by using the commercial FEM software Ansys 8.1. Some electrical characters (such as device power) can be only observed from Burn-In process, but not static acceleration tests. These effects were fully discussed in this thesis. The analyses got the result that the smaller solder ball pitch/solder ball diameter causes the more serious solder ball deformation under the specific socket vendor precondition. Burn-In time are also a significant factor for solder deformation. Basically the longer BI time cause the more serious solder deformation. The device power effect is not significant within the power sampling range of this thesis.

Automobiles have become an integral part of our daily life as more and more mopeds, motor cycles, cars, trucks, busses and trains are being used for transport. The main parts of an automotive engine are cylinder, piston assembly, connecting rod and crank shaft. The piston assembly consists of Piston, Piston rings and Piston Pin. Piston rings are important parts of a piston assembly. Any non-conformance in any quality characteristic of the piston ring leads to deterioration of engine performance. M/S Goetze (India) Limited a medium scale industry and a sister concern of engineering giant M/S Escorts Limited is manufacturing "GOETZE PISTON RINGS" and is producing about 800 varieties of piston rings ranging from 35.00 mm to 228.5 mm nominal diameter. The management was facing serious problem due to high scrap rate in certain types of their manufactured piston rings. Hence instead of trying to handle all of them at the same time, it seemed reasonable to tackle and find a suitable approach to solve the quality problem by taking the most notorious ring first, so that once the methodology is understood, documented and applied to the quality problem of this ring, the same can also be invoked for other rings to improve upon their quality, and thus reducing the scrap rate. One particular ring of 83.0 mm diameter which is delicate and costly, having an average scrap rate of 36.2% in past three years is selected for the study. No systematic effort was made in the past to identify the quality characteristics and the processes which were responsible for this high scrap rate and thus no immediate measure could be recommended. As a matter of fact at the beginning of the study it was not even clear which quality characteristics were mainly responsible for such high rejection. So in July' 1999 a pareto analysis was done for the first time to identify the culpability of each quality characteristic for the rejection of the ring. From the Pareto analysis it was observed that maximum proportion of rejection was due to nonconformity in axial thickness. The scrap rate due to nonconformity in axial thickness were collected for each month from Jul’ 999 to Jan'2000 which averaged at 8.7%. Since in every month the major malefactor for rejection was the nonconformity of axial thickness it was decided to first try to improve the quality of axial thickness, before trying to tackle other quality issues associated with this particular piston ring under study. Once the most problematic quality characteristic namely the axial thickness was identified, as a first step towards the goal of improving the quality of axial thickness, it was necessary to pay attention and isolate the manufacturing processes or operations affecting the axial thickness and study them in detail. So first, the entire manufacturing process flow diagram of the piston ring was studied. From the process flow diagram it appeared that there are 4 operations affecting axial thickness viz. Rough Grinding ,Medium Grinding, First Lapping and Finish Lapping. So each of these processes was critically observed to assess whether they were under statistical control or not. Studies were conducted at each of these 4 operations by collecting samples using the rational subgroup method and control charts were plotted. From the control charts, it was observed that the Rough Grinding and Medium Grinding operations were in statistical control with acceptable Cp, Cpk values. But First Lapping and Finish Lapping operations were not in statistical control. Thus we finally identified the two critical processes namely the First Lapping and Finish Lapping operations which were not in statistical control but were crucially affecting the quality of axial thickness. Since the First and Finish Lapping operations were identified as the major source of the quality problem, an in-depth study was undertaken to analyze these two processes. A brain storming session was conducted with all concerned personnel from production, maintenance, design, quality assurance and tool room to get all possible causes which might be affecting the axial thickness variation at these two processes. During the brain storming session the team suggested that the First Lapping process can be processed in medium grinding machine (DFS machine) instead of Lapping machine. The reasons behind this were two fold. First since the aim of the First Lapping is just to remove excess material which was deposited during chrome plating, the same operation can be performed in DFS machine. Since the required surface finish on axial surface was any way being aimed at the Finish Lapping operation, a similar precursory First Lapping'operation in a Lapping machine was really felt not necessary. Secondly since the performance of the DFS machine was found to be under control, albeit for the grinding operation, it was hoped that the Lapping operation in the same machine would also exhibit a similar performance. For this purpose a study was conducted on the First Lapping operation with the DFS machine. It was found that the process was well within the control limit with decent Cp and Cpk values. Thus this procedure of performing the First Lapping operation in a DFS machine took care of the first one of the two problematic processes affecting the quality of axial thickness. Next for tackling the problem with the other critical process, viz. the Finish Lapping operation, various causes were suggested by the team for axial thickness variation in the Finish Lapping operation. Based on these causes, an Ishikawa diagram (cause and effect diagram) was prepared. This Ishikawa diagram had thrown light into number of possible deficiencies in Man, Machine, Method and Material which were responsible for axial thickness variation at finish Lapping. The Ishikawa diagram was carefully analyzed. The causes were narrowed down to 6 factors. These are Grinding wheel rotating speed, Grinding Time, Grinding pressure, Holding plate, Holes (fixtures) within the holding plate and Positions within a ring. The 3 factors namely grinding wheel speed, time and pressure were identified as the control factors. Holding plate, Hole position within a plate and Checking position within a ring on the other hand were the noise factors whose different levels might exhibit a variability of axial thickness. Since there were only 3 control factors, it was decided to conduct a full factorial experiment with each control factor at 3 levels. Hence altogether there were 27 experiments at a fixed given combination of speed, time and pressure. There were 4 holding plates with each plate having 6 slotted holes leading to machining 24 rings at a time during the finish lapping operation. Next 3 measurements were taken for each one of these 24 rings. Thus altogether there were 72 observations for one of these experiments. Each experiment was replicated twice by taking measurements for 2 consecutive batches of rings. From the analysis of variance of the results of these experiments for both S/N ratio and mean it was observed that all the three main factors and their interactions were significant. The Normality assumption of standardized residuals for the S/N ratio and mean was validated by normal probability plot and Kolmonogorov-Smirnoff test. The homoscedasticity assumption was validated through Bartlett’s test and residual plots. It was found that the experiment no. 23 (Speed 84 RPM, Time 10 sees and Pressure 300 daN) yielded highest S/N ratio (η) with mean within the specification limit. That the mean and S/N ratio for the experiment no.23 were significantly different from others was established by means of Tukey's multiple comparison test. Next control charts for experiment no. 23 were plotted and was found to be well within control with acceptable Cp and Cpk values. Hence we concluded that the non-conformance in axial thickness can be substantially reduced by using the following optimal setting of factors i.e. grinding speed with 84 RPM, grinding pressure with 300 daN and grinding time with 10 seconds. Using this optimal setting the earlier average rejection rate of 8.7% due to non-conformance in axial thickness was reduced to 0.05%. Under this optimal setting, the process capability index (Cpk) of finish Lapping operation was estimated to be 2.5, which is well above acceptable standard. Due to this reduction in rejection rate in one quality characteristics of one particular ring out of 800 types, the net savings to the organization is approximately Rs. 10,44,000 per year.

Semi-solid manufacturing is a near net shape forming process that takes advantage of an alloy's thixotropic behaviour. However, in order to obtain the desired thixotropic properties from an alloy in the semi -solid state, the microstructure of the as-cast feedstock metal needs to display a fine grained, equiaxed primary phase prior to reheating for the forming operation. Various methods are currently in use to obtain the required microstructure of which the MagnetoHydroDynamic (MHD) process is predominant. Two fundamental factors, namely shear rate and cooling rate, influence the formation of the fine grained, equiaxed primary phase during the MHD process. The aim of this research was to produce semi solid billets and in so doing, determine how the influence of the combination of the two fundamental factors contribute towards the final formation of the primary phase and to determine an optimal level ofthese factors' settings to deliver the desired microstructure. An MHD apparatus was constructed and the Taguchi method was used to design an experiment to investigate the influence ofthe fundamental factors involved in casting semi solid feedstock of aluminium A356.2. The issues ofthe formation of a fine eutectic phase and solidification shrinkage were also investigated. An experimental method was designed to investigate the significance ofthe fundamental factors' influence towards the appearance of the primary phase; the latter was evaluated using an image analysis system. The shear rate was controlled by varying the line frequency and the base frequency supplied to the electromagnetic stirrer and the cooling rate was controlled by initiation of a fixed, fast cooling rate at a certain melt temperature (TJ Results showed that a fine grained, equiaxed primary phase, with an average grain size of 55 /lm, was achieved after casting, prior to reheating for forming. The contribution of the base frequency and the line frequency were 8 % and 3.5 % respectively and the contribution ofTi was 86.5 % towards the outcome ofthe result. The cooling rate changed from approximately 0.3 QC/sec to 4.5 QC/sec at Ti. A fine textured eutectic phase was achieved with the fast cooling rate. The solidification shrinkage was accounted for by incorporating a riser on the mould. The feedstock produced in this research was compared, on a microstructural basis, to commercially available Semi Solid Metal (SSM) feedstock from Pechiney and SAG. The research feedstock had a larger, average primary grain size, however, it was more discrete and round grained than the commercial alloys which were finer and more rosette grained. Upon reheating to the semi solid state, ready for forming, the final, evolved grain sizes and shapes were almost identical between the research and commercial feedstock, despite the initial differences in grain sizes and shapes. However, the commercial alloys showed primary grains with trapped eutectic whereas in the research alloy, the primary grains were largely free of trapped eutectic. / Thesis (M.Sc.Eng.)-University of Natal, Durban, 2000.

No description available.

Thesis (Ph. D.)--Missouri University of Science and Technology, 2008. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed March 2, 2009) Includes bibliographical references (p. 216-220).

Thesis (M.S.)--University of Texas at El Paso, 2009. / Title from title screen. Vita. CD-ROM. Includes bibliographical references. Also available online.

Thesis (M.S.)--University of Missouri--Rolla, 2007. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed October 24, 2007) Includes bibliographical references.

The effects of various catalyst synthesis parameters on the photocatalytic degradation kinetics of aqueous methyl orange dye are presented. The four factors investigated were: i) InVO4 concentration, ii) nickel concentration, iii) InVO4 calcination temperature, and iv) ballmilling time. Three levels were used for each factor. Due to the large number of possible experiments in a full factorial experiment, an orthogonal-array experimental design was used. UV-vis spectrophotometry was used to measure the dye concentration. The results show that nickel concentration was a significant parameter, with 90% confidence. The relative ranking of importance of the parameters was nickel concentration > InVO4 concentration > InVO4 calcination temperature > milling time. The results of the orthogonal array testing were used to make samples of theoretically slowest and fastest catalysts. Curiously, the predicted-slowest catalyst was the fastest overall, though both samples were faster than the previous set. The only difference between the slowest and fastest catalysts was the milling time, with the longer-milled catalyst being more reactive. From this result, we hypothesize that there is an interaction effect between nickel concentration and milling time. The slowest and fastest catalysts were characterized using energy-dispersive spectroscopy (EDS), scanning electron microscopy (SEM), x-ray powder diffractometry (XRD), BET surface area analysis, and diffuse-reflectance spectroscopy (DRS). The characterization results show that the fastest catalyst had a lower band gap than the slowest one, as well as a slightly greater pore volume and average pore diameter. The results indicate that fast kinetics are achieved with low amounts of nickel and a long ball milling time. Under the levels tested, InVO4 concentration and the calcination temperature of the InVO4 precursor were not significant.

A new optimization technique for SPICE modeling parameters has been developed in this dissertation to increase the accuracy of the circuit simulation. The importance of having accurate circuit simulation models is to prevent the very costly redesign of an Integrated Circuit (IC). This radically new optimization technique utilizes the Taguchi method to improve the fit between measured and simulated I-V curves for GaAs MESFETs. The Taguchi method consists of developing a Signal-to-Noise Ratio (SNR) equation that will find the optimum combination of controllable signal levels in a design or process to make it robust or as insensitive to noise as possible. In this dissertation, the control factors are considered the circuit model curve fitting parameters and the noise is considered the variation in the simulated I-V curves from the measured I-V curves. This is the first known application of the Taguchi method to the optimization of IC curve fitting model parameters. In addition, this method is not technology or device dependent and can be applied to silicon devices as well. Improvements in the accuracy of the simulated I-V curve fit reaching 80% has been achieved between DC test extracted parameters and the Taguchi optimized parameters. Moreover, the computer CPU execution time of the optimization process is 96% less than a commercial optimizer utilizing the Levenberg-Marquardt algorithm (optimizing 31 FETs). This technique does a least square fit on the data comparing measured currents versus simulated currents for various combinations of SPICE parameters. The mean and standard deviation of this least squares fit is incorporated in determining the SNR, providing the best combination of parameters within the evaluated range. Furthermore, the optimum values of the parameters are found without additional simulation by fitting the response curves to a quadratic equation and finding the local maximum. This technique can easily be implemented with any simulator that utilizes simulation modeling parameters extracted from measured DC test data. In addition, two methods are evaluated to obtain the worst case modeling parameters. One method lobks at the correlation coefficients between modeling parameters and the second looks at the actual device parameters that define the +/- 3σ limits of the process. Lastly, an example is given that describes the applicability of the Taguchi methodology in the design of a differential amplifier, that accounts for the effect of offset voltage. / Ph. D.