Department of Mechanical Engineering

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This paper investigates the physicochemical and thermo-physical properties of CaO–CaF2–SiO2 and CaO–TiO2–SiO2 based electrode coating for welding offshore structures. Twenty-one electrode coating compositions have been formulated using extreme vertices design method. The coating was crushed to powder form. The powder was characterized for weight loss, density, specific heat, enthalpy, thermal conductivity, diffusivity, and specific heat. Coating's structural analysis was done using X-Ray Diffraction and Fourier transformation. X-Ray Fluorescence, Thermogravimetric Analyzer, and Hot disc have been used to characterize the coating mixture. The regression analysis has been used to study the effect of individual constituents and their binary, tertiary interactions on the properties. The obtained output of properties has been optimized using multi-response optimization. © 2019 Elsevier Ltd and Techna Group S.r.l.

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Ceramics International

Physicochemical and thermo physical characterization of CaO–CaF2–SiO2 and CaO–TiO2–SiO2 based electrode coating for offshore welds

This article is an attempt to develop Ni-based shielded metal arc welding electrodes to join SS304L austenitic stainless steel to P91 martensitic steel used in power plant applications. Nickel-based electrodes were prepared using a mixture design approach. Dissimilar welds of SS304L/P91 were fabricated using Nickel-based laboratory-developed electrodes and commercially available electrode (ENiCrFe-3). A comparison was drawn between the weld characteristics of commercial and laboratory-developed electrodes. Experimentation was performed to evaluate the microstructural changes and mechanical characterization which includes hardness profile, tensile strength, the impact strength of the base materials, as well as dissimilar welds. Welds fabricated with a laboratory-developed electrode possesses better weld quality and mechanical characteristics. A higher amount of Ni and Cr was observed in the laboratory developed electrodes as compared to the commercial electrode. © 2020, © 2020 Taylor & Francis.

Materials and Manufacturing Processes

Investigations on dissimilar welding of P91/SS304L using Nickel-based electrodes

This article is an attempt to investigate the effect of the shot peening on hot corrosion behaviour of alloy P9 when exposed to a molten salt mixture of 40%Na2SO4+ 60%V2O5. The specimens were operated at 750°C. The shot peening process creates short diffusion paths, which helps to enhance the rapid fusion of the elements. It helps in the formation of protective oxides, which leads to better corrosion resistance against molten salt attack. Thermogravimetric analysis was carried out to observe the impact of molten salts on the corrosion rate of the different specimens. The shot-peened specimens possess better corrosion resistance properties as compared to the non-shot peened specimens. © 2020 Elsevier Ltd. All rights reserved.

Materials Today: Proceedings

Effect of shot peening on the high temperature molten salt corrosion resistance of P91 boiler steel

This present work has made a noteworthy attempt to demonstrate brief modeling of N-link manipulator and subsequent modal characterization along with the determination of static deflection of a two-link flexible manipulator with a payload. In addition, investigation of nonlinear phenomena of dynamic responses under 3:1 internal resonance has also been accomplished considering geometric nonlinearities. An appropriate and realistic dynamic modeling of the two-link manipulator taking into account of inertia coupling and geometry compatibility between equations of motion and boundary conditions has been derived using the extended Hamilton’s principle. The effect of parametric variation on system eigenfrequencies is well tabulated, and the corresponding eigenspectrums are illustrated graphically. Further, the nonlinear phenomena of dynamic solutions have been demonstrated by using MMS of second order for its statutory effect onto the system instability for the existence of S-N bifurcations. The effect of nonlinearities and various design parameters on the dynamic responses and subsequent bifurcations for 3:1 internal resonance has also been demonstrated. The outcome of the present work enables new understanding into the design criterion and performance limitation of multi-link flexible robots. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature.

Archive of Applied Mechanics

Modal characterization with nonlinear behaviors of a two-link flexible manipulator

An autogenous gas tungsten arc welded P92 weld joint was subjected to two different post weld heat treatment (PWHT). One PWHT involved tempering of the as-welded sample at 760 °C for 2 h (referred to as PWDT) followed by natural air cooling. The other PWHT involved normalizing (re-austenitizing) the as-welded sample at 1040 °C for 40 min followed by PWDT (referred as PWNT). The cross-section of the as-welded sample exhibited a higher degree of microstructural heterogeneity. Both the PWDT and PWNT heat treatment procedures reduced the heterogeneity gradient along the weld cross section. The heat affected zone (HAZ) of the as-welded and PWDT samples showed Charpy toughness values of 3 ± 4 J and 64 ± 6 J, respectively, which were lower than that of the base metal (72 ± 5 J). The PWNT treated sample exhibited a HAZ Charpy toughness value of 83 ± 4 J which was higher than that of the base metal. The brittle mode of the fracture with river patterns was observed for the as-welded and PWDT treated sample while a ductile mode of fracture with fine and shallow dimples was observed for the PWNT condition. The PWNT treatment resulted in dissolution of the ferrite patches and formation of a uniform microstructure along the weld cross section. The PWNT treated samples exhibited the lowest yield strength to tensile strength ratio supporting the enhanced ductility as a result of this re-austenizing heat treatment. The as-welded and PWDT treated weld joints showed the presence of detrimental δ ferrite phase in the weld fusion zone and the coarse grained heat affected zone. The PWNT completely removed the δ ferrite patches from the microstructure whereas the PWDT treatment merely reduced the range of the hardness of the δ ferrite from 179 to 301 HV (as welded) to 204–228 HV. © 2018 Elsevier B.V.

Journal of Materials Processing Technology

Role of evolving microstructure on the mechanical behaviour of P92 steel welded joint in as-welded and post weld heat treated state

The tungsten inert gas welded P91 steel welded joints were subjected to the two different type of heat treatments including the postweld direct tempering (PWDT) and re-austenitizing based tempering (PWNT) treatment. The microstructure of weld fusion and heat affected zone (HAZ) were characterized in different heat treatment conditions using optical microscope and scanning electron microscope. For as-welded joint, a great heterogeneity was observed in microstructure and mechanical properties across the weldments. The Charpy toughness of the as-welded joint was measured much lower than the minimum recommended value of 47 J and it was measured 8 ± 5 J. The PWHTs have found a beneficial effect in decreasing the microstructure heterogeneity across the welded joint and improving the mechanical properties. The PWDT resulted in a drastic improvement in the Charpy impact toughness of the welded joint and it was measured 59 ± 5 J which was higher than the minimum required value of 47 J but still inferior than the base metal. The δ ferrite still remained in overlap zone of the weld fusion zone. The PWNT treatment resulted in homogeneous microstructure and hardness variation across the welded joint in transverse direction and Charpy impact toughness (149 ± 6 J) exceeded than that achieved in base metal. © 2018 Politechnika Wrocławska

Archives of Civil and Mechanical Engineering

Softening mechanism of P91 steel weldments using heat treatments

Journal of Aircraft

Time-domain system identification of helicopters using nonlinear acceleration and jerk prediction model

This study reports a novel approach for growing multilayer thin films consisting of alternate layers of carbon nanotubes (CNT) and nickel on Si (1 0 0) substrates and justifies their use in thin film temperature sensors. A low pressure chemical vapor deposition system was employed for synthesizing CNT films, while Ni films were deposited by electrodeposition. Porous-Si was used as substrate to increase adhesion between the layers of the multilayer structure. The structure of the multilayer films and the quality of the CNT grown were analyzed using several characterization methods, including scanning electron microscopy, x-ray photoelectron spectroscopy, x-ray auger electron spectroscopy and Raman spectroscopy. The electrical characteristics were investigated using a van der Pauw setup and the effect of the increasing number of CNT layers in the multilayer structure was studied. The sensitivity of the multilayer film was found to increase with increasing number of CNT layers, despite the decrease of the temperature coefficient of resistance. On the other hand, the initial resistance was found to increase. Results indicated that these multilayer structures are appropriate for fabricating highly sensitive thin film gauges that can detect lower heat fluxes with more accuracy. © 2019 IOP Publishing Ltd.

Journal of Physics D: Applied Physics

Layer by layer deposition of alternate carbon nanotubes and Ni films for efficient multilayer thin film temperature gauges

Software plays a major role in analysis and simulation of solar stills. These simulation techniques are very much cheaper and time saving compared to the experimental analysis of a system. This chapter explains the different software used for the design and testing of various models of solar still. It also gives an overall idea of what type of software being used and its feasibility. Software like MATLAB, ANSYS and FLUENT have been taken into account here for modelling and development of various solar stills. Moreover, software such as SPSS is often used for statistical data analysis. All recent software have been selected and reviewed and the benefits explained. © Springer Nature Singapore Pte Ltd. 2019.