Department of Mechanical Engineering

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IIT Jodhpur

Solar energy-based technologies have seen remarkable development in the last decades. This is observed all across the world. The concerns related to cost and availability of fossil fuels, effects of climate change due to use of fossil fuels are the primary drivers behind the usages of these technologies. With such motivation, several research groups around the world are working in the field of solar energy. Since this field is quite diverse, it includes academicians of diverse background such as physics, chemistry, materials science, mechanical engineering, electrical engineering etc. This monograph is an effort to present the collection of such effort with an aim to present the developments at the system-level as well as the challenges and opportunities that are present at the technical level. It includes chapters covering the following themes—overview of energy usage in developing countries, solar thermal systems (heating and cooling), energy storage, and solar cells. © 2020, Springer Nature Singapore Pte Ltd.

World University root node

Energy, Environment, and Sustainability

Introduction to Solar Energy: Systems, Challenges, and Opportunities

The static deflections of cutting tool and thin-walled components during end milling operation contribute significantly towards deviation of a machined surface from the desired level resulting in violation of tolerances. The designer specifies tolerances as per Geometric Dimensioning and Tolerancing (GD&T) standard (ASME Y14.5-2009 or ISO 1101) to transfer designer intent to the manufacturer. The machined surface deviation for straight components translates into flatness error, defined as the normal distance between the two parallel planes encompassing distorted points. This paper investigates the relative contributions of tool and workpiece deflections on the flatness error during end milling of thin-walled components. It is attempted by developing computational models to estimate cutting forces, tool-workpiece deflections and flatness error with associated parameters. A set of end milling experiments are conducted on thin-walled components to substantiate the results.It has been observed that the contribution of tool and workpiece deflections on flatness error has significant dependence on the cutting widths. The outcomes of the present study provides meaningful insights to the manufacturing process planners in determining optimal cutting conditions and strategies to control flatness error during machining of thin-walled components. © 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the scientific committee of the 53rd CIRP Conference on Manufacturing Systems

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Procedia CIRP

Tool and workpiece deflection induced flatness errors in milling of thin-walled components

The aim of this study is to investigate the high-temperature corrosion behavior of 304L stainless steel in the environment of various molten salt mixtures in the temperature range of 550–850°C. Weight change measurement has been done and characterization of corroded specimen was carried out using XRD, SEM/EDS techniques. Findings indicate that high chloride concentration salts affect the corrosion resistance adversely. The protective behavior of Cr2O3 layer deteriorated and its passivation is hindered at higher temperature owing to the chlorination-oxidation process. Fe2O3 and (Fe, Cr)xOy were found to be the major phases in the corrosion product. The salts were found to significantly affect the corrosion of 304L stainless steel in the following order: K2SO4 + 60% NaCl &gt; Na2SO4 + 50% NaCl &gt; 40% K2SO4 + 40% Na2SO4 + 10% KCl + 10% NaCl &gt; Na2SO4 + 60% V2O5 &gt; Air. © 2020, Indian Academy of Sciences.

Sadhana - Academy Proceedings in Engineering Sciences

Elevated temperature molten salt corrosion study of SS304L austenitic boiler steel

Polyetheretherketone (PEEK) is a semi-crystalline, high temperature resistant, FDA approved polymer, attracted many engineering and medical research practitioners due to its excellent mechanical and biological properties. PEEK has comparable mechanical properties to natural bone and its polymeric constituent. PEEK has been identified as one of the high temperature(Tm= 373oC) polymers with excellent thermal, chemical and radiological inertness. High temperature resistance, good Young's modulus and biological inertness of PEEK attract it to be a prominent bone implant material. Metallic bone implants have been surpassed slowly by PEEK composites. However, PEEK is found to be inferior in rigidity to natural bone due to its limited Young's modulus. Hydroxyapatite (Ca10(PO4)6(OH)2), a bone inductive and ceramic reinforcement is extracted from egg shells by thermal processing to strengthen PEEK matrix of the proposed bone composite. Upon several delimiting studies, ceramic constituent is limited to 40% by weight. The combination of constituents being newer, an exhaustive study on thermal stability of the composite has been carried out at ARCI, IICT and KELVN Hyderabad. Thermal gravimetric analysis (TGA), Derivative thermo gravimetric analysis (DTG) and Differential Scanning Calorimetry (DSC) were the sources of analysis. TGA, DTG and DSC have been used to evaluate percentage of weight loss, peak degradation temperature and melting temperature respectively. Degradation of the composite was found to increase with the percentage of PEEK in the composite. The study has been conducted beyond the melting temperature of the PEEK and up to 600oC. Degradation of the composite has been showing an inverse relation with rate of heating. Maximum percentage of mass degradation 28.7% of the total weight was recorded in structurally superior PEEK/HA 80/20 composite at a rate of heating 10C/ min as against 33.9% in pure PEEK. © 2020 American Institute of Physics Inc.. All rights reserved.

AIP Conference Proceedings

Thermal degradation study for manufacturability of polyetheretherketone/hydroxyapatite bone implant composite

The present work aims to investigate the microstructure and mechanical behavior of the dissimilar welded joint (DWJ) of martensitic A 335-grade P91 steel and high alloy ferritic austenitic A 182 F69 steel produced by the gas tungsten arc welding (GTAW) process. The microstructural studies showed the variety of the microstructure across the DWJ, which formed mainly due to the solidification and solid-state phase transformation as a result of the weld thermal cycle. The microstructural studies were performed in as-welded as well as post-weld heat treatment (PWHT) conditions. PWHT has been conducted to improve the mechanical properties of the P91 heat-affected zone (HAZ) at 760 °C (PW 1) and 810 °C (PW 2) for 2 h. For the mechanical properties of the DWJ, tensile tests, and microhardness tests were conducted. The fractured tensile specimen has been characterized using the scanning electron microscope (SEM) equipped with energy dispersive spectroscopy (EDS). The centre region of the weld metal showed the equiaxed dendrites while the interface near the boat fusion line, on both the P91 and F69 sides, showed the cellular and columnar dendrites. PWHT has observed a negligible effect on the microstructure and hardness of WFZ and F69 HAZ, while a significant change was observed for P91 HAZ. The tensile strength of the DWJ was measured maximum (735 MPa) for as-welded condition and reduced after the PWHT and for PW 2, it was measured lower than that of P91 and F69 base metal. The failure of the tensile specimen was also noticed in the soft inter-critical HAZ (ICHAZ) region for PW 2 condition. © 2020 Elsevier Ltd

International Journal of Pressure Vessels and Piping

Characterization of structure-property relationship of martensitic P91 and high alloy ferritic austenitic F69 steel

This paper investigates the metallurgical behavior and mechanical properties of the P91 steel welds joint. The joint of heat-resistant P91 steel has been welded by the gas tungsten arc welding (GTAW) process using the dissimilar Inconel grade 617 filler. The P91 welds joints have been subjected to varying heat treatment regimes in the temperature range of 650–810 °C for 2 h. The normalizing-based tempering was also performed for the welded joint. The weld fusion zone (WFZ) with austenitic structure and heat-affected zones (HAZs) with martensitic structure was characterized using the optical microscope and scanning electron microscope (SEM). The detailed characterization of the weld metal and HAZ interface has also been performed for as-welded and post-weld heat treatment (PWHT) conditions. For mechanical properties of the welds joint, tensile testing and hardness testing were performed. The relationship between mechanical behavior and microstructure of the welded joint has been evaluated for as-welded and heat treatment conditions. The microstructure studies revealed the formation of an unmixed zone (UZ) close to the fusion line, and it was characterized as peninsula and island. The WFZ showed the complete austenitic mode of the solidification and revealed the austenitic structure with cellular and equiaxed grains in the center of the weld metal. The columnar and cellular dendrites were seen near the boat fusion line, i.e., interface of the weld metal and HAZ. The soft δ ferrite patches were observed near the fusion line in the area of HAZ and remain undissolved up to tempering temperature of 810 °C (PW 3). The dissolution of the ferrite patches was noticed for PW 4. The maximum and minimum tensile strength of the welds joint was measured 731 MPa and 502 MPa for PW 3 and PW 2, respectively. A uniform hardness variation in the transverse direction of the welded joint was observed for PW 3 and PW 4 conditions. The optimum combination of strength and ductility was obtained for the PW 3 condition. © 2020, Wroclaw University of Science and Technology.

Archives of Civil and Mechanical Engineering

Role of dissimilar IN617 nickel alloy consumable on microstructural and mechanical behavior of P91 welds joint

In this review article, microstructure and mechanical behavior of the dissimilar welded joint (DWJ) between ferritic-martensitic steel and austenitic grade steel along with its application have been summarized in Ultra Super Critical (USC) power plant. Creep-strength enhanced ferritic-martensitic (CSEF/M) P91 steel was developed to sustain at extreme operating conditions of ultra-supercritical (USC) power plants, and later, P92 was developed to achieve better mechanical properties, higher creep-rupture strength and high operating temperature with the reduction in wall thickness as compared to P91 steel. The most common application of P91/P92 material in power plants includes high pressure and high-temperature steam piping, headers, super-heater tubing, and water-wall tubing. The other most commonly used material in the power plants is austenitic stainless steel, i.e., SS 304 L. The austenitic grade stainless steel offers high resistance to corrosion due to the high wt. % chromium and nickel content (18–20 and 8–12, respectively). Due to the low carbon content, the SS 304 L is less sensitive to the sensitization problem and offers excellent weldability. The joining of these dissimilar materials is frequently required in the power generation industry. The current review focuses on the main difficulty associated with dissimilar welding of martensitic P91/P92 and austenitic grade stainless steel. The different chemical composition, mechanical, physical and metallurgical properties of the martensitic P91/P92 and austenitic grade stainless steel leads to the problems such as hot cracking and carbon migration. The other weldability issues are the formation of a brittle intermetallic compound, the formation of soft transaction heat affected zone along with martensitic steel, δ ferrite formation in fusion zone, diffusion related problem, and residual stresses, which necessitates thorough study and qualification of welds. The effect of coarsening of various precipitates such as M23C6 carbides, MX carbonitrides, and effect of laves phase, z-phase, and sigma phase on mechanical property, and creep-rupture strength of DWJ are also discussed in detail. Based on the literature reviewed, it has been found that some of the above-stated problems can be solved by using nickel-based filler wire due to its intermediate physical and mechanical properties. The selection of the proper filler metal is another vital issue in dissimilar welds joint that is also covered in this review article. The reason behind the formation of the unmixed zone, filler deficient region, peninsula, island, beach, migrated grain boundaries, solidified grain boundaries, and solidified subgrain boundaries during DWJ of martensitic P91/P92 and austenitic grade stainless steel is also discussed. The heat treatment is required to eliminate the heterogeneous microstructure during the dissimilar welding. The effect of post-weld heat treatment (PWHT) on the microstructure and mechanical behavior of the DWJ also reviewed. The residual stress developed during the DWJ may cause the premature failure of the components under service, has also been discussed in detail. The effect associated with the residual stress deformation has been reviewed in the different conditions of the DWJ. © 2020 The Society of Manufacturing Engineers

Journal of Manufacturing Processes

A critical review on dissimilar welds joint between martensitic and austenitic steel for power plant application

This paper investigates the microstructural features and mechanical behavior of the dissimilar welded joint (DWJ) of lean duplex A 182 F 69 steel and 2.25Cr-1Mo (P22) steel. The multi-pass DWJ has been prepared using the Gas Tungsten Arc Welding (GTAW) process employing the Inconel 617 filler material. The DWJ has been subjected to post-weld heat treatment (PWHT) in a temperature range of 760 °C (PW 1)-810 °C (PW 2). The tensile testing and metallographic testing sample have been cross-sectioned from the DWJ for different heat treatment conditions of the welded joint. Each zone of the DWJ was characterized using the optical and scanning electron microscope (SEM). Cellular and columnar dendrites have been observed near the interface of weld fusion zone (WFZ) and heat-affected zone (HAZ) while equiaxed structure in center of the WFZ. The WFZ showed the austenitic structure with dendritic core and inter-dendritic boundaries. The inter-dendritic boundaries showed the presence of secondary phase particles, mainly enriched with Cr, Mo and Ti. Unmixed zone and compositional variation across the WFZ and HAZ interface have been observed on both the sides of DWJ. For as-welded condition, tensile fracture surface revealed the mixed mode of the fracture with tensile strength higher than that of the base P22 and F69 steel. The fracture location was in the center of the WFZ. For PW 1 condition, the crack initiation zone showed the mixed-mode while the final fracture showed the brittle fracture with cleavage facets. In PW 1, the fracture has been observed in HAZ of P22 side with strength lower than that of the base metal of F69. In PW 2 condition, complete brittle mode of the fracture has been observed and fracture surface showed the cleavage facets with river marking. © 2020 Elsevier B.V.

Fusion Engineering and Design

Role of heat-treatment and filler on structure-property relationship of dissimilar welded joint of P22 and F69 steel

This paper presents a robust motion control of a sitting-type lower limb rehabilitation robot (LLRR) in its operational-space. The mathematical background of the proposed robot is discussed and its motion control design in the task-space based on a double-loop control approach is derived herein along with its closed-loop system stability analysis. The motion tracking performance analysis of the proposed scheme is demonstrated using computer based numerical simulations. For numerical simulations and to validate the effectiveness of the motion control strategy, the clinically obtained test gait data is used for the desired motion trajectory of the lower limb rehabilitation robot. © 2020, The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG.

Advances in Intelligent Systems and Computing

Robust Operational-Space Motion Control of a Sitting-Type Lower Limb Rehabilitation Robot

We report surface hardening or crust formation, like caking, during evaporation when a porous medium was heated from above using IR radiation. These crusts had higher strength than their closest counterparts such as sandcastles and mud-peels which essentially are clusters of a partially wet porous medium. Observed higher strength of the crusts was mostly due to surface tension between the solid particles, which are connected by liquid bridges (connate water). Qualitative (FTIR) and quantitative (TGA) measurements confirmed the presence of trapped water within the crust. Based on the weight measurements, the amount of water trapped in the crusts was ~1.5%; trapped water was also seen as liquid bridges in the SEM images. Further, in the fixed particle sizes case, the crust thickness varied slightly (only 10–20 particle diameters for cases with external heating) while with the natural sand whole porous column was crusted; surprisingly, the crust was also found with the hydrophobic glass beads. Fluorescein dye visualization technique was used to determine the crust thickness. We give a power-law relation between the crust thickness and the incident heat flux for various particle sizes. The strength of the crust decreased drastically with increasing hydrophilic spheres diameter while it increased with higher surface temperature. Copyright: © 2020 Kumar et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.