Differential finishing of freeform surfaces (knee joint) using R-MRAFF process and negative replica of workpiece as a fixture

It is difficult and challenging to achieve uniform nanoscale surface finish in the contact zone, particularly on freeform (or sculptured) surfaces having different curvatures at different locations. Femoral (or, Knee joint component) is one of such biomedical freeform component which has complex profile along its curvature. Surface conditions of a femoral decide the life of the implant and they play a crucial role in its functionality. The variation in surface roughness of the femoral should be minimum in the contact zone. For this purpose, a special tooling is being proposed for rotational magnetorheological abrasive flow finishing (R-MRAFF) process. A negative replica of the workpiece (knee joint) as a tool (or a fixture) is used so that the medium flow velocity in the fluid flow channel is almost constant (or minimum possible variations) along the medium flow direction. It is able to do differential finishing also along the curvature. In addition, pulsating magnetic field has been used to generate vibrations in the medium in the finishing zone so that the possibility of fresh abrasive particles interacting with the surface of femoral is high. The surface finish has been achieved ranging from 26 nm to 62 nm using the proposed finishing technique and negative replica of the workpiece (femoral) as a fixture.     

Performance assessment of microwave treated WC insert while turning AISI 1040 steel

This study attributed to post treatment of tungsten carbide (WC) inserts using microwave irradiation. Tungsten carbide inserts were subjected to microwave radiation (2.45 GHz) to enhance its performance in terms of reduction in tool wear rate, cutting force surface roughness and improvement in tool life. Performance of tungsten carbide insert is very much affected by machine operating parameters i.e. speed, feed and depth of cut. An attempt has been made to investigate the effects of machining parameters on microwave treated tool inserts. This paper describes the comparative study of machining performance of untreated and microwave treated WC tool inserts used for turning of AISI 1040 steel. Machining performance has been evaluated in terms of flank wear, cutting force, surface roughness, tool wear mechanisms. Critical examinations of tool wear mechanisms and improvements in metallurgical properties such as microstructural change, phase activation of WC grains were identified using scanning electron microscope (SEM). Results obtained from the turning using the microwave treated tool inserts showed a significant reduction tool wear thereby enhancing the surface quality of workpiece.     

Atomization and combustion of canola methyl ester biofuel spray

The spray atomization and combustion characteristics of canola methyl ester (CME) biofuel are compared to those of petroleum based No. 2 diesel fuel in this paper. The spray flame was contained in an optically accessible combustor which was operated at atmospheric pressure with a co-flow of heated air. Fuel was delivered through a swirl-type air-blast atomizer with an injector orifice diameter of 300 μm. A two-component phase Doppler particle analyzer was used to measure the spray droplet size, axial velocity, and radial velocity distributions. Radial and axial distributions of NO, CO, CO₂ and O₂ concentrations were also obtained. Axial and radial distributions of flame temperature were recorded with a Pt–Pt/13%Rh (type R) thermocouple. The volumetric flow rates of fuel, atomization air and co-flow air were kept constant for both fuels. The droplet Sauter mean diameter (SMD) at the nozzle exit for CME biofuel spray was smaller than that of the No. 2 diesel fuel spray, implying faster vaporization rates for the former. The flame temperature decreased more rapidly for the CME biofuel spray flame than for the No. 2 diesel fuel spray flame in both axial and radial directions. CME biofuel spray flames produced lower in-flame NO and CO peak concentrations than No. 2 diesel fuel spray flames.     

Rotational abrasive flow finishing (R-AFF) process and its effects on finished surface topography

The present study focus on abrasive flow finishing (AFF), a process that finishes complex internal and external geometries with the help of viscoelastic abrasive medium, while keeping in mind its low finish and material removal rates (MRR). Researchers have often strived to improve finishing rate and MRR. As an attempt to overcome the said limitations, this paper discusses rotational abrasive flow finishing (R-AFF) process wherein complete tooling is externally rotated and the medium reciprocates with the help of hydraulic actuators. In this study, preliminary experiments are conducted on Al alloy and Al alloy/SiC metal matrix composites (MMCs) at different extrusion pressures, and medium compositions are employed for finding optimum conditions of the same for higher change in roughness (ΔR_a). The same optimum conditions are used to study the effect of workpiece rotational speed on (ΔR_a), material removal (MR), change in workpiece hardness and surface topology. It is noted that as the workpiece rotational speed increases from 2 to 10 RPM, the experimental helix angle decreases from 22° to 9° and the helical path length increases from 67 to 160 mm. Based on these findings the mechanism of material removal of matrix and reinforcement in MMC using R-AFF have been proposed. Here the matrix material is removed by micro-cutting and three methods of material removal mechanisms for reinforcement are also explained. The scientific logic behind finishing mechanism of matrix and reinforcement, cross hatch patterns, helical path directions, micro-scratch (μ-scratch) width and depth variation with size, orientation and support that active abrasive grain obtains from neighboring abrasives is derived from scanning electron microscopy micrographs. Finally this study establishes that R-AFF can produce 44% better ΔR_a and 81.8% more MR compared to the AFF process. Accordingly, R-AFF generates micro cross hatch pattern on the finished surface that can improve lubricant holding capabilities.     

Variability of mesopause temperature derived from two independent methods using meteor radar and its comparison with SABER and EOS MLS and a collocated multi-wavelength dayglow photometer over an equatorial station,Thumba (8.5° N, 76.5° E)

Two independent methods for deriving mesopause temperature using meteor radar installed at an equatorial station, Thumba (8.5° N, 76.5° E), are discussed in this article. This meteor radar-derived mesopause temperature is then compared with two different types of spaceborne measurement, namely (i) Sounding the Atmosphere using Broadband Emission Radiometry (SABER) and (ii) the Earth Observing System Microwave Limb Sounder (EOS MLS), and a collocated multi-wavelength dayglow photometer (DGPM). The meteor radar-derived temperature is in fairly good agreement with all the three measurement techniques, with an uncertainty of ±10°. This study focuses on a detailed evaluation and inter-comparison of mesopause temperature derived from different measurement techniques. An attempt is also made to compare the suitability of these observations to study planetary waves and other oscillation activities in the mesospheric region.     

Iterated fast local search algorithm for solving quadratic assignment problems

This paper concentrates on multi-row machine layout problems that can be accurately formulated as quadratic assignment problems (QAPs). A genetic algorithm-based local search approach is proposed for solving QAPs. In the proposed algorithm, three different mutation operators namely adjacent, pair-wise and insertion or sliding operators are separately combined with a local search method to form a mutation cycle. Effectiveness of introducing the mutation cycle in place of mutation is studied. Performance of the proposed iterated approach is analyzed and the solution qualities obtained are reported.     

Factors affecting the long-term stability of Cu/Al ball bonds subjected to standard and extended high temperature storage

This paper presents the findings of work performed on 20-μm diameter copper wire of five different wire types from three suppliers. Gold wire is the control. The test die was mounted on BT (B (Bismaleimide) and T (Triazine)) resin substrates. The bonding parameters were optimized for each wire used. Part of the optimization process involved monitoring the flatness of the bonded ball and the amount of aluminum remaining under the bond. The crystal structure of each type of interconnect was examined using composite imaging techniques. Visual data such as ball size, thickness, and shape were collected. First and second bonds were subjected to destructive testing, such as ball shear and wire pull, throughout the preparation process. The samples were then subjected to an industry-standard, high temperature stress test to determine the long-term stability of the interface of each wire type. Data for all read points are presented on all tests performed and provide useful information on the material and process set best suited for long term reliability.     

Hafnium or zirconium high-k fab cross-contamination issues

Hf and Zr contamination during immersion in process solutions is most likely to occur in neutral and caustic solutions. Both Hf and Zr contamination are introduced onto the wafer surface if they are present in an ammonium hydroxide peroxide mixture solution (which is caustic), but such contamination is removed using existing acid cleans. Large amounts of wafer-to-wafer cross contamination occurs in plasma etch tools. Particles can cause cross contamination in a thermal reactor during high-temperature anneals of high-k dielectric layers. Residual surface cross contamination does not diffuse into the wafers during thermal processing. If contamination remains on a wafer, gate oxide integrity degradation is only observed at high concentrations. Near surface minority carrier lifetime is also affected, but bulk lifetime is not.     

Plasma characterization of dry ��-EDM

An attempt was made to characterize the dry microelectric discharge machining (??-EDM) plasma systematically by using optical emission spectroscopy. In order to characterize the plasma and its parameters such as plasma temperature, electron density, Debye length, and gamma parameter, the optical spectra were recorded for different energies and with different diameters of tool electrode. From the recorded spectra, using line pair method and modified Saha equation, plasma temperature and electron density, respectively were calculated. From these two, Debye length and plasma parameter were also calculated. These studies indicate that the plasma produced in dry ??-EDM is ideal. In addition to this, we found that the dry ??-EDM region is below the conventional EDM region in log electron density and log temperature plot. Morphological analysis was carried out on crater produced by different energies on the workpiece using a scanning electron microscope. The crater shape may dependent on the geometry of the tool tip, number of discharges, and energy of discharge.