Application of Taguchi Method on Biaxial Stretch Forming of Friction Stir Processed Mg AZ31B Alloy

The present study describes the effect of friction stir processing parameters on formability of Mg AZ31B sheet under biaxial stretching. The formability of friction stir processed sheet was studied by limiting dome height test in biaxial strain deformation mode. The experiments were carried out as per the Taguchi parametric design concepts and an L9 orthogonal array was used to study the influence of various combinations of process parameters. Statistical optimization technique, ANOVA was used to determine the optimum levels and to find the significance of each process parameter. The results indicate that the traverse speed is the most significant factor followed by the rotational speed and the tilt angle in deciding the formability of friction stir processed magnesium alloy. In addition, mathematical model was developed to establish relationship between the different process variables with formability by regression analysis.     

Electrokinetic flow in connected channels: a comparison of two circuit models

We apply the recently developed ‘ion current model’ (ICM) to investigate mixed pressure-driven/electro-osmotic flow in electrokinetic series circuits. Under the ICM, the local geometric mean ion concentration varies throughout a microfluidic circuit as a consequence of ion conservation. ICM predictions are used to assess the accuracy of the earlier ‘total current model’ (TCM), which is instead based upon the simplifying assumption that the geometric mean ion concentration is uniform in all channels within a circuit. The model comparison is performed over an experimentally relevant range of physical parameters and channel dimensions. When the ratio of total current to flow rate is small, or when the inlet concentration is very low or very high, the ICM and TCM give similar predictions of the total pressure and potential differences across simple three-channel contraction–expansion networks. Otherwise, the errors introduced using the TCM may be very large. Our results demonstrate that the common assumption that the electrolyte concentration throughout a device is equal to the concentration of fluid supplied to the device is not always valid, even if there is little or no electric double layer overlap.     

Friction Factor Evaluation Using Experimental and Finite Element Methods for Al-4%Cu Preforms

In this study, ring compression tests and finite element (FE) simulations have been utilized to evaluate the friction factor, m, under different lubricating conditions for powder metallurgical (P/M) Al-4%Cu preforms. A series of ring compression tests were carried out to obtain friction factor (m) for a number of lubricating conditions, including zinc stearate, graphite, molybdenum disulfide powder, and unlubricated condition. FE simulations were used to analyze materials deformation, densification, and geometric changes, and to derive the friction calibration curves. The friction factor has been determined for various initial relative densities and different lubricating conditions, and a proper lubricant for cold forging of P/M Al-4%Cu preforms is found. Studies show that the use of lubricants has reduced the friction. However, increase in the number of pores in the preforms leads to excessive friction. The FE simulation results demonstrate a shift in the neutral plane distance from the axis of ring specimen, which occurred due to variations in the frictional conditions and initial relative densities. The load requirement for deformation, effective stress, and effective strain induced, and bulging phenomena obtained by FE simulations have a good agreement with the experimental data.     

Organizational Patterns

When we study the literature and the evidence of recent innovation, we see a confusing array of different techniques. The confusion is deepened, because each of these new methods is presented to us as if the embodiment of industrialization itself—in an exclusivist sense. This confusion is hardly surprising, however; no more surprising, indeed, than the arrogance with which each example is promoted. For, while all governments are throwing a similar challenge at their respective building industries, the actual innovative responses occur when some practical and tangible portion of market can be hardened up and made available to any intending innovator. (This is because industrialization presupposes continuity and the risks involved are too great to be left to the market hazards typical of our industry today.)     

VOLUME-OF-FLUID CALCULATION OF HEAT OR MASS TRANSFER ACROSS DEFORMING INTERFACES IN TWO-FLUID FLOW

A new volume-of-fluid (VOF)-based numerical method for calculating heat transfer or mass transfer of a species within and between fluids with deforming interfaces is described. The algorithm is tested first against an analytical solution for diffusion from a sphere, and good agreement between theory and calculation is shown. The method is then demonstrated by predicting (a) heat transfer from a rising bubble when the bubble forms a toroidal shape, and (b) mass transfer from a rising drop when the drop phase controls diffusion. The method is shown to be a viable approach for complex interfacial heat/mass transfer.     

Shock tube studies of methyl butanoate pyrolysis with relevance to biodiesel

Methyl butanoate pyrolysis and decomposition pathways were studied in detail by measuring concentration time-histories of CO, CO₂, CH₃, and C₂H₄ using shock tube/laser absorption methods. Experiments were conducted behind reflected shock waves at temperatures of 1200–1800 K and pressures near 1.5 atm using mixtures of 0.1%, 0.5%, and 1% methyl butanoate in Argon. A novel laser diagnostic was developed to measure CO in the ν₁ fundamental vibrational band near 4.56 μm using a new generation of quantum-cascade lasers. Wavelength modulation spectroscopy with second-harmonic detection (WMS-2f) was used to measure CO₂ near 2752 nm. Methyl radical was measured using UV laser absorption near 216 nm, and ethylene was monitored using IR gas laser absorption near 10.53 μm. An accurate methyl butanoate model is critical in the development of mechanisms for larger methyl esters, and the measured time-histories provide kinetic targets and strong constraints for the refinement of the methyl butanoate reaction mechanism. Measured CO mole fractions reach plateau values that are the same as the initial fuel mole fraction at temperatures higher than 1500 K over the maximum measurement time of 2 ms or less. Two recent kinetic mechanisms are compared with the measured data and the possible reasons for this 1:1 ratio between MB and CO are discussed. Based on these discussions, it is expected that similar CO/fuel and CO₂/fuel ratios for biodiesel molecules, particularly saturated components of biodiesel, should occur.     

Spectroscopic sensor techniques applicable to real-time biodiesel determination

The term biodiesel refers to the Fatty Acid Alkyl Esters (FAAE) derived from vegetable, animal or waste oil feedstocks. This alternative fuel is increasingly becoming a significant part of the transport sector with over 10 million tonnes sold in the EU in 2007. Currently a small amount of biodiesel (presently 3.5% in the UK) is present in diesel fuel but this could rise to up to 30% in the medium term. As biodiesel is not one chemical compound but an amalgamation of different FAAE, the physical properties of the diesel fuel are not only dependent on the amount of biodiesel in the diesel fuel (blend level) but also on the fatty acid profile of the biodiesel. In this paper we report on an initial study to assess a range of current techniques which could be used in the future as a basis to determine blend level in unknown samples of diesel and gain further information on the fatty acid profile of the biodiesel in the blend. The three techniques applied were FT-IR spectroscopy, refractive index and UV-Vis spectroscopy.     

Simulating particle agglomeration in the flash smelting reaction shaft

A steady-state, axi-symmetric, numerical model was developed to investigate the agglomeration of molten particles of sulphide ore in the reaction shaft of a flash smelting process used for extracting copper. The turbulent, particle-laden, gas flow was simulated in conjunction with a population balance model to account for agglomeration. The agglomeration was found to depend primarily on the particle to gas mass loading ratio, and the particle size and turbulence intensity at the shaft inlet. Predictions compared well with the limited experimental data in the literature. Increasing the angle at which the flow enters the shaft from the burner was found to increase agglomeration up to a critical angle at which the flow behaviour changes. The results have implications for the control and reduction of dust levels in the waste gas stream.     

Organizational learning: conceptual challenges from a project perspective

Do-it-yourself (DIY) is a staple element of the spare time activities of many households, but little is known about the extent to which basic repair work is carried out through DIY and about the quality of this work. Through secondary analyses of UK government data (English House Condition Survey and Family Expenditure Survey), this paper examines the scale of DIY work by owner-occupiers, how work is organized, the interrelationship of DIY work, the use of unpaid help, and the use of contractors. It considers the types of work carried out, the characteristics of those who tackle DIY or use unpaid help, the dwelling types most likely to experience DIY work, and the motivations of and constraints on those home-owners who do it. The paper concludes with a discussion on the policy implications of these findings for government and the building industry. Although most DIY work is cosmetic and does not deal with basic repair and maintenance, the sheer scale of DIY ensures that it makes a contribution to improving housing conditions. The provision of more advice, information and education by government, local authorities and the private sector could ensure that more DIY work is of better quality and that home owners give priority to essential repairs whether or not they tackle these themselves.