Department of Mechanical Engineering

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This article deals with the development of shielded metal arc welding electrodes for P22/P91 welds. A comparison has also been drawn with commercially available electrodes. P22 low alloy steel matching electrodes developed in the laboratory using a mixture design approach was employed to fabricate the dissimilar weld. Experimentations were performed to evaluate the microstructure and mechanical properties of microhardness, tensile strength, and impact energy of the welds. The impact strength was found to improve by 19% for a laboratory developed electrode made welds as compared to the commercial electrodes. The weld chemistry investigations indicate that the weld fabricated with laboratory-developed electrodes have a higher amount of chromium and molybdenum. These elements are known to enhance the corrosion resistance of joint, thereby imparting enhanced structural integrity in high temperature operating conditions. The electrodes designed and developed in this work are found to enhance the properties of P22/P91 joint much better as compared to that with the commercial electrodes. © IMechE 2020.

World University root node

Proceedings of the Institution of Mechanical Engineers, Part L: Journal of Materials: Design and Applications

Experimental investigations on P22/P91 dissimilar shielded metal arc welds for power plant applications

This paper investigates the thermophysical, physicochemical, and surface properties of mineral waste red ochre, assessing suitability for application in welding consumable development. Red ochre is an anhydrous iron oxide derived from tailings of iron ore haematite. High iron and silica concentration makes it suitable for various engineering applications. Iron in the electrode coatings is known to increase arc stability, bead smoothness, and also it enhances slag detachability along with smoothening bead profile. The red ochre has been characterized for the properties of weight loss, density, specific heat, enthalpy, thermal conductivity, and diffusivity. Structural analysis of red ochre powder has been done using Fourier transformed infrared spectroscopy and X-ray diffraction. BET (Brunauer, Emmett, and Teller) surface area analysis has been done to estimate the surface properties, which include pore radius and specific surface area. The shielded metal arc welding electrodes have been developed by adding red ochre in a fixed proportion, and produced welds have been examined for visual defects, microstructure, and microhardness. © IMechE 2020.

Experimental investigations on red ochre for application in welding consumable development

This paper aims at utilizing mineral waste red ochre in the design and development of welding electrodes for offshore welds. Red ochre has been characterized to ascertain its suitability for acting as electrode coating constituent. Thermo Gravimetric Analysis was done to observe its behavior upon heating to high temperature and red ochre was found to be 97.8% stable upon exposure to 900 °C. Thermal Conductivity measurement done using hot disk gives value of thermal conductivity, diffusivity and specific heat. Red ochre has an enthalpy of 15454.0782 J/g, conductivity 0.2961 W/mK, diffusivity of 0.2130 mm2/s and specific heat 1.39 J/kgK. The electrodes were manufactured by adding red ochre to coating mixture containing minerals: silica, calcite, rutile, and fluorspar. Multi pass beads were made and characterized to estimate the performance of developed electrodes. Bead appearance, arc stability, reduced blow, slag detachability and micro hardness measurement supports the use of red ochre in developing welding consumables. © 2020 Elsevier Ltd. All rights reserved.

Materials Today: Proceedings

Utilization of red ochre in developing welding electrodes for offshore welds

This paper investigates the high-temperature wettability property of the mineral waste red ochre added CaO–CaF2–SiO2 and CaO–TiO2–SiO2-based electrode coating mixture for offshore welding. The extreme vertices design method was applied to formulate 21 coating compositions. The pellets made from developed electrode coating compositions were exposed to a high temperature of 1250℃ on the substrate of super duplex stainless steel of 2507 grade. The molten flux has been characterized for contact angle, surface tension, adhesion energy and spreadability. The regression analysis has been used to estimate the effect of individual components and their interactions on the wettability property parameters. The developed regression models have been optimized using multiresponse optimization to achieve optimum flux composition. Structural analysis of flux mixture has been done using X-ray diffraction and Fourier transformation spectroscopy. © IMechE 2020.

High-temperature wettability study of mineral waste added CaO–CaF2–SiO2 and CaO–TiO2–SiO2-based electrode coating for offshore welds

Physicochemical and thermo-physical behaviour were studied for the agglomerated submerged arc fluxes for CaO–SiO2–CaF2 and CaO–SiO2–Al2O3 flux system. Mixture design approach was used to develop twenty-one fluxes. Thermogravimetric (TGA), differential-scanning calorimetric (DSC), hot-disk technique and XRD techniques were utilized to analyse the fluxes. Structural behaviour of fluxes was analyzed using Fourier transform infrared spectrometer. Thermal behaviour of fluxes was observed in the temperature range of 25 °C to 900 °C. Thermo-physical behaviour such as specific heat, thermal diffusivity and thermal conductivity of each flux were evaluated by hot disc technique. Multi objective optimization was performed to derive the optimized flux formulations. This type of flux formulation helps us to evaluate the physical-chemical and thermo-physical behaviour of different mineral constituents used during submerged arc welding process. © 2019 Elsevier Ltd and Techna Group S.r.l.

Ceramics International

Design &amp; development of SAW fluxes using CaO–SiO2–CaF2 and CaO–SiO2–Al2O3 flux systems

This article presents the dynamic modeling and nonlinear analysis of two-link flexible manipulator with generic payload whose center of gravity is different than the point of attachment with the link. The manipulator is driven by harmonic joint motions and subjected to a constraint force at the terminal end due to its interaction with working environment. Hamilton’s approach is adopted to dynamically model the multi-link manipulator for longitudinal and transverse vibrations incorporating the nonlinearities associated with axial stretching. The resulting set of eigenfrequency equations are solved numerically with subsequent generation of eigenspectrums. Further, this paper investigates the resonant behavior of manipulator links for the subharmonic and primary resonance conditions due to end follower force and revolute joint motions, respectively. The resonant responses show the jump phenomenon and existence of multi-valued solutions at pitchfork and saddle-node bifurcation points. The numerical and graphical results thus obtained, clearly indicate the significant influence of variation of system configurations and generic payload on eigencharacteristics and nonlinear responses, and hence must be given consideration during dynamic modeling of a manipulator in order to attenuate undesirable vibrations. © 2020, © 2020 Taylor & Francis Group, LLC.

Mechanics Based Design of Structures and Machines

Influences of generic payload and constraint force on modal analysis and dynamic responses of flexible manipulator

The investigation of the end-point trajectory and the nonlinear oscillation of elastic manipulator with offset payload mounted on moving base has been carried out by demonstrating the modal parameters and dynamic responses of a bi-directionally deflected rotating flexible link manipulator. A large deflection model of a flexible rotating manipulator considering both transverse and axial deformation, dynamics of rotating hub, generic payload, and rigid motion of platform has been derived. Initially, modal analysis has been studied to graphically illustrate the eigenfrequencies and corresponding eigenspectrums, while it has been noted that the system possesses distinct and different vibration characteristics as compared to that of a system without offset payload. A smooth sinusoidal input torque has been imparted to the joint to assess the time dependency factors and parameters, which describe its position inaccuracy over time. Finally, the investigation of influence of essential system attributes on the nonlinear behavior and system instabilities under resonance conditions by analyzing the steady-state solutions has been accomplished. The effect of payload parameters such as mass, inertia, and offset, along with the inertia and stiffness of actuator on the frequency response curves has been demonstrated graphically. This work exhibits that the system’s dynamics diversely evolve with a change of offset parameters while system loses its stability due to saddle-node bifurcations. The present result offers specific guidelines towards the design and control aspects of flexible manipulators based on the selection of offset parameters. © IMechE 2020.

Proceedings of the Institution of Mechanical Engineers, Part K: Journal of Multi-body Dynamics

Position analysis and nonlinear phenomena of flexible manipulator with generic payload mounted on a moving base

The present numerical study deals with a mathematical model representing mass transfer in blood flow under stenotic condition. Streaming blood is considered as a non-Newtonian fluid characterized by Carreau fluid model and the vessel wall is taken to be flexible. The nonlinear pulsatile flow phenomenon is governed by the Navier-Stokes equations together with the continuity equation while that of mass transfer is governed by the convection-diffusion equation coupled with the velocity field. A finite difference scheme is developed to solve these equations accompanied bysuitable initial and boundary conditions. Results obtained are examined for numerical stability up to wanted degree of correctness. Various significant hemodynamic parameters are examined for additional qualitative insight of the flow-field and concentration-field over the entire arterial segment with the help of the obtained numerical results. Comparisons are made with the available results in open literature and good agreement has been achieved between these two results. Comparisons have been made to understand the effects of viscosity models for Newtonian and non-Newtonian fluids and also for rigid and flexible arteries. © 2020. All Rights Reserved.

Fulltext

Journal of Applied Fluid Mechanics

Numerical Simulation of Mass Transfer in Pulsatile Flow of Blood Characterized by Carreau Model under Stenotic Condition

Cold compressive strength (CCS) and apparent porosity (AP) of pellets are essential properties regarding the burden of blast furnaces. The optimal required values for industries are 2.5 KN CCS and 21% AP. Blaine fineness and firing temperature are the decisive parameters analyzed here. During firing, microstructure phases such as silicate, hematite, and pore are formed. The phase’s grain density during induration influences the pellet’s CCS and AP. The influence of the factors over the response is evaluated by I-optimal (response surface methodology) design. Blaine fineness, firing temperature, pore phase grain density (PPGD), silicate phase grain density (SPGD), and hematite phase grain density (HPGD) affect the CCS and AP of pellets. The RSM-I-optimal predicted responses with a coefficient of determination (R2) of 0.89 for CCS and 0.91 for AP of iron ore pellets. Optimal conditions were Blaine no. = 1668 cm2/g, 1250 °C firing temperature, PPGD value 90 no/mm2, SPGD value 250 no/mm2, and HPGD value 490 no/mm2, with 4.5 KN CCS 27%. The induration processes were investigated through statistical design of experiments for process optimization. Statistical analysis indicated the direct and interactive influence over CCS and AP. In this study, RSM-I-optimal modeling is used for iron ore pellets processing. The I-optimal prediction could be applied to make the process economical because information is obtained through fewer experiments. © 2020, Society for Mining, Metallurgy & Exploration Inc.

Mining, Metallurgy and Exploration

Analysis of the Influence of Blaine Numbers and Firing Temperature on Iron Ore Pellets Properties Using RSM-I-Optimal Design: An Approach Toward Suitability

The present study focuses on the mitigation of shock wave using novel geometric passages in the flow field. The strategy is to produce multiple shock reflections and diffractions in the passage with minimum flow obstruction, which in turn is expected to reduce the shock wave strength at the target location. In the present study the interaction of a plane shock front (generated from a shock tube) with various geometric designs such as, 1) zig-zag geometric passage, 2) staggered cylindrical obstructions and 3) zig-zag passage with cylindrical obstructions have been investigated using computational technique. It is seen from the numerical simulation that, among the various designs, the maximum shock attenuation is produced by the zig-zag passage with cylindrical obstructions which is then followed by zig-zag passage and staggered cylindrical obstructions. A comprehensive investigation on the shock wave reflection and diffraction phenomena happening in the proposed complex passages have also been carried out. In the new zig-zag design, the initial shock wave undergoes shock wave reflection and diffraction process which swaps alternatively as the shock front moves from one turn to the other turn. This cyclic shock reflection and diffraction process helps in diffusing the shock wave energy with practically no obstruction to the flow field. It is found that by combining the shock attenuation ability of zig-zag passage (using shock reflection and diffraction) with the shock attenuation ability of cylindrical blocks (by flow obstruction), a drastic attenuation in shock strength can be achieved with moderate level of flow blocking. © 2020 The Authors