Multi-Objective Parametric Optimization of Weld Strength of Metal Inert Gas (MIG) Welding by using Analysis of Variance, Taguchi, and VIKOR Techniques

Welding is an enormously essential manufacturing technique which allows the users to create permanent joints efficiently, due to its durability this process is extensively used in various industries like automotive, construction as well as in the aviation industry. The present study focuses on the optimization of the Metal Arc Welding using VIKOR method. Four input variables Current, Voltage, Wire Feed Rate and Gas Flow Rate are considered to study their effect on three responses tensile, bending and hardness on the weldments of AISI 1008 low carbon steel material. Experiments were planned as per Taguchi‘s L9 OA. As traditional Taguchi method is not adequate to solve multi responses problem, to overcome this limitation MCDM approach VIKOR analysis has been carried out for obtaining optimal parameters setting for multi-response optimization. Three specimens (for tensile, bending, and hardness) for each experimental run are fabricated for the measurement of respective strength and hardness. Investigation is done by following the steps of VIKOR method, and optimal parameter setting for multi quality response is obtained corresponding to the lower VIKOR index value. Keywords: Metal Inert Gas (MIG) Welding, VIKOR, S/N ratio, ANOVA

Fast and reliable transient simulation and continuous optimization of large-scale gas networks

We are concerned with the simulation and optimization of large-scale gas pipeline systems in an error-controlled environment. The gas flow dynamics is locally approximated by sufficiently accurate physical models taken from a hierarchy of decreasing complexity and varying over time. Feasible work regions of compressor stations consisting of several turbo compressors are included by semiconvex approximations of aggregated characteristic fields. A discrete adjoint approach within a first-discretize-then-optimize strategy is proposed and a sequential quadratic programming with an active set strategy is applied to solve the nonlinear constrained optimization problems resulting from a validation of nominations. The method proposed here accelerates the computation of near-term forecasts of sudden changes in the gas management and allows for an economic control of intra-day gas flow schedules in large networks. Case studies for real gas pipeline systems show the remarkable performance of the new method.

Numerical Analysis of Effects of Specularity Coefficient and Restitution Coefficient on the Hydrodynamics of Particles in a Rotating Drum

Various simulations have been conducted to understand the macroscopic behavior of particles in the solid-gas flow in rotating drums in the past. In these studies, the no-slip wall boundary condition and fixed restitution coefficient between particles were usually adopted. The paper presents a numerical study of the gas-solid flow in a rotating drum to understand the effect of the specularity coefficient and restitution coefficient on the hydrodynamic behavior of particles in the segregation process. The volume fraction, granular pressure, granular temperature and their relationships are examined in detail. The boundary conditions of the no-slip and specularity coefficient of 1 are compared. In the simulations, two different sizes of particles with the same density are considered and the Eulerian–Eulerian multiphase model and the kinetic theory of granular flow (KTGF) are used. The results reveal that the hydrodynamical behavior of the particles in the rotating drum is affected by the boundary condition and restitution coefficient. In particular, the increase of specularity coefficient can increase the active region depth, angle repose, granular pressure for both small and large particles and granular temperature for large particles. With increasing restitution coefficient, the angle of repose decreases and granular pressure and temperature increase at the same volume fraction for both small and large particles.

Experimental Research of Gaseous Emissions Impact on the Performance of New-Design Cylindrical Multi-Channel Cyclone with Adjustable Half-Rings

Cyclones are widely used for separating particles from gas in energy production objects. The efficiency of conventional centrifugal air cleaning devices ranges from 85 to 90%, but the weakness of many cyclones is the low collection efficiency of particles less than 10 μm in diameter. The novelty of this work is the research of the channel-type treatment device, with few levels adapted for precipitation of fine particulate matter, acting by a centrifugal and filtration principle. Many factors have an impact on cyclone efficiency—humidity, temperature, gas (air) composition, airflow velocity and etc. Many scientists evaluated only the effect of origin and size of PM on cyclone efficiency. The effect of gas (air) composition and temperature, and humidity on the multi-channel cyclone-separator efficiency still demands contributions. Complex theoretical and experimental research on air flow parameters and the efficiency of a cylindrical eight-channel system with adjustable half-rings for removing fine-dispersive particles (<20 μm) was carried out. The impact of air humidity and temperature on air flow, and gaseous smoke components on the removal of wood ashes was analyzed. The dusty gas flow was regulated. During the experiment, the average velocity of the cyclone was 16 m/s, and the temperature was 20–50 °C. The current paper presents experimental research results of wood ash removal in an eight-channel cyclone and theoretical methodology for the calculation of airflow parameters and cyclone effectiveness.

Effect of reactive gas condition on nonpolar AlN film growth on MnS/Si (100) by reactive DC sputtering

The effects of reactive gas flow conditions on nonpolar AlN film growth on MnS/Si (100) substrates using reactive DC magnetron sputtering were investigated. During AlN deposition at a substrate temperature of 750 °C, the MnS surface can be unintentionally nitrided, resulting in a decrease in the crystallinity of the AlN. Low temperature growth of the AlN layer at 300 °C prevents this nitridation and results in the crystallization of nonpolar AlN. A N2 flow equal to 30% of the Ar sputtering gas flow was found to improve the crystallinity of the nonpolar AlN and to reduce nitrogen defects, which play an important role in interfacial reactions. Nitrogen defects promote the formation of alloys such as AlMn and MnSi that degrade the interface and can significantly decompose the MnS. A higher proportion of N2 improves the nonpolar AlN crystallinity, reduces the concentration of defects and suppresses reactions at the AlN/MnS interface.

Synthesis of porous γ-Fe2O3 from scorodite synthesized using ultrasound irradiation and evaluation of its battery performance

The effect of 200 kHz ultrasound on scorodite synthesis at 70 °C and 3 h reaction conditions was investigated using sulfuric acidic solutions of various pH (3.0, 2.0, 1.5, 1.0, and 0.0). In contrast to the case of only O2 gas flow without ultrasound irradiation, oxidizing radicals generated by ultrasound irradiation promote Fe(II) oxidation in solution and precursor, allowing scorodite to synthesize with high crystallinity (>99%), which relates to low solubility, even in strong acid solution at pH 1.0. During synthesis, particle shape was changed to polyhedral or spindle type depending on the pH of 0.0 to 3.0. The spindle-shaped scorodite was probably formed by the decrease of precursor amount produced in initial stage of the synthesis. Furthermore, porous maghemite obtained by alkali treatment of scorodite showed initial discharge capacities of 146 mAh/g (polyhedron) and 167 mAh/g (spindle), indicating that its potential use as a cathode material for lithium-ion batteries.