BITS Faculty Publications

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Author: search.filters.author.Mishra, Radha RamanSubject: search.filters.subject.Mechanical Engineering

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Now showing 1 - 10 of 35
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    Investigation on Microwave Joining of Mild Steel Plates at 2.45 GHz and Joint Characterization
    (Springer, 2021-02) Mishra, Radha Raman
    Microwave joining of materials is a recently developed advanced joining process in which electromagnetic energy at 2.45 GHz is used to develop butt joint between different metallic plates. Rapid selective hybrid heating of the targeted area depends upon the location of the metallic samples inside the applicator cavity during microwave exposure. A high electric field intensity location for rapid hybrid heating of samples was identified inside the resonating cavity with the help of the COMSOL Multiphysics 5.2. Accordingly, experimentation was done to develop joints of mild steel (MS) samples using microwave energy at 2.45 GHz and input power of 900 W. The nickel powder was used as an interface material between metallic plates. The fabricated mild steel butt joints were characterized to analyse the microstructures and the micro indentation hardness of the joints. The microstructural characterization of the joints revealed complete melting of nickel powder and its fusion with base mild steel plates. The presence of iron in the joint zone indicated a metallurgical fusion of the interface layer with the base metal; however, oxides and carbides presence in the joint indicated interaction with atmospheric oxygen and carbon in the susceptor. The hardness of the developed joint zone was 405 ± 12 Hv which is higher as compared to the base metals (211 ± 12 Hv).
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    Analysis of Density of Laser Powder Bed Fusion Fabricated Part Using Decision Tree Algorithm
    (Springer, 2023-05) Mishra, Radha Raman
    Additive manufacturing (AM) enabled manufacturing industries to fabricate metallic components with complex shapes. However, the properties of additively manufactured parts need further improvements to compete with the performance of traditionally manufactured parts. Machine learning (ML) models provide an alternative to study the correlation between the process parameters–properties of the fabricated parts. In the present work, the ML approach has been applied to understand the effect of AM process parameters on the density of additively built parts. The decision tree model was developed for the laser powder bed fusion-processed parts based on the input parameters such as laser power, scan speed, hatching space, energy density, and build rate. The model was trained and tested with experimental data obtained from the relevant literature. The process parameters were optimized to achieve the desired density of the part. A good agreement was indicated between the predicted and experimental data. The study revealed the applicability and potential of the model to determine and predict the density of the additively manufactured parts.
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    Microwave Processing of Materials Fundamentals and Applications
    (Taylor & Francis, 2022) Mishra, Radha Raman
    The use of microwave energy in material processing is increasing gradually due to numerous benefits over conventional energy sources. Volumetric heating characteristic of microwave energy while processing engineering materials has been explored in various manufacturing processes such as sintering, casting, joining, drilling and cladding. However, the fundamentals associated with microwave heating of materials are less explored. The present chapter summarizes most of the significant fundamentals of microwave-material interaction and heating phenomena that occur during microwave energy absorption in materials. Various microwave energy-based applications are discussed.
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    Processing of Composite Materials Using Microwave Energy
    (CRC Press, 2022) Mishra, Radha Raman
    Composite materials are being popularly used in the fabrication of various industrial components. Most of the manufacturing techniques used for developing parts involve the interaction of heat with the constituent materials through heat transfer. Such processing methods result in non-uniform heating of materials; subsequently, various defects are incurred in the developed products. The use of microwave energy while developing composite materials may overcome these challenges as it offers volumetric and rapid heating and significant saving of time and energy. The present chapter summarizes various fundamentals of microwave-material interaction and heating of different composite materials during microwave processing. Heating mechanisms involved in processing composites such as metal matrix composites, ceramic matrix composites, and polymer matrix composites have been discussed. Challenges in the processing of composite materials have been highlighted, and further research directions have been outlined.
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    Microwave joining of SS-316 plates: A multi-physics simulation study
    (Elsevier, 2023-07) Mishra, Radha Raman
    Microwave hybrid heating has emerged as a new technique for joining metallic materials. The presence of a multi-material system (bulk and powder) and the selection of suitable interface powder in microwave joining offer challenges. The present work addresses these issues for microwave joining of SS-316L plates using different interface powders nickel-based (EWAC 1004 EN) and SS-316L interface powders. A multi-physics model of the microwave joining setup was developed to theoretically study the joining characteristics of SS-316L joints using both powders at 2.45 GHz and 900 W. The SS-316L joints were developed experimentally in 720 s and 680 s while using interface powders EWAC and SS-316L, respectively. The model was validated with experimental results and simulation was performed to analyse the electric field distribution, resistive losses, temperature distribution, thermal stress distributions, and energy utilization. The simulation results showed that the electric field intensity was 4.96 % higher in EWAC-based joint as compared to SS-316L-based joint; consequently, the EWAC-based joint attained a temperature of 1450 °C at the central plane. The resistive loss was found maximum between the susceptor and joint interlayer in both joints. Thermal stress was 62 % higher in EWAC-based joint than SS-316L-based joint. Microstructural investigation of the joints revealed that EWAC-based joints contained columnar and dendritic grain structures; while equiaxed grains were present in SS-316L-based joints. Porosity and grain size were higher by 34 % and 53 %, respectively in EWAC-based joint than SS-316L-based joint.
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    Role of Crystal Orientation, Temperature, and Strain Rate on the Mechanical Characterization of Nickel: An Atomistic-scale investigation
    (Sage, 2023-09) Mishra, Radha Raman
    In this article, the influence of crystallographic orientation on the mechanical properties of pristine nickel (Ni) during uniaxial tensile deformation was explored by utilizing molecular dynamics simulations. To study the influence of [0 01] and [11 8 5] crystal orientations on the mechanical properties and microstructural evolution of pristine Ni, simulations were performed at different temperatures ranging from 100 K to 900 K and at strain rates ranging from 107 to 1010 s–1. The results revealed that Ni with [11 8 5] orientation showed a higher elastic modulus than Ni with [0 0 1] orientation, whereas the yield strength of [0 0 1] orientation was higher than [11 8 5] orientation for a combination of temperatures and strain rates. Also, in comparison to [11 8 5] crystal orientation, the system with [0 0 1] orientation showed a high amount of dislocation density at the yield strain point for lower strain rates. At higher strain rates, the face-centered cubic to body-centered cubic transition was more prominent in the Ni system with [0 0 1] orientation, and it tends to decrease with the increase in temperature. Our present work may help materials scientists design materials with different crystal orientations that can perform according to the applied strain rates and temperatures. It is also proposed that tailoring of mechanical properties is achievable by exposing Ni with different crystal orientations to various environmental conditions (cryogenic, ambient, and elevated temperatures with different applied strain rates).
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    Thermal analysis of in-situ microwave casting for efficient processing
    (Elsevier, 2018) Mishra, Radha Raman
    In the present work, in-situ microwave casting was analyzed for higher efficiency while aluminum casting at 2.45 GHz and 1400 W. Models of setup with different insulation arrangements were generated using a software tool. Simulation was carried out to find the optimum casting conditions. Results revealed that complete insulation of mold assembly enhances energy saving and reduces melting time; however, higher mold preheating results in longer solidification time and coarse grains in the cast. Mold assembly without insulation showed poor efficiency. Optimum results were obtained in a mold assembly consisting insulated pouring basin and charge with bare mold and sprue
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    Characterization of SiC-Reinforced AZ91 Magnesium Alloy Composites Produced Using In situ Microwave Casting
    (Springer, 2021-02) Mishra, Radha Raman
    Magnesium-alloys-based metal matrix composites (MMCs) are one of the most researched materials for producing industrial components due to their high specific strength. In recent years, microwave energy has been used for processing of various materials including polymers, ceramics, metals, and composites owing to significant saving of energy and time as compared to the conventional processes. In the present work, microwave energy at 2.45 GHz was used to fabricate AZ91 magnesium-alloy-based MMCs. The AZ91 magnesium alloy (bulk) pieces were hybrid heated inside a microwave applicator at 1400 W. The melt was processed with silicon carbide (SiC) and allowed to pour into a graphite mold. The produced composites were characterized to study their microstructural properties. The microstructural characterization of the composites revealed that distribution of SiC particles is uniform. Finer grains were achieved in the composite as compared to as-received alloy. The presence of SiC, Mg2Si, Mg2C, Mg2C3, Mg17(Al, Zn)12, and α-Mg phases was confirmed in the composite through energy-dispersive X-ray spectroscopy analysis. The micro-indentation hardness of the composite was found as 206 ± 28 HV which is higher than as received alloy.
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    On microstructural and mechanical properties of 21-4-N nitronic steel joint developed using microwave energy
    (Sage, 2021-07) Mishra, Radha Raman
    In the current experimental work, an effort has been made to explore the feasibility of fusion joints of 21-4-N nitronic steel employing microwave heating. These fusion joints were developed inside a domestic microwave applicator operating at 900 W. Microwave energy was used to fabricate the joints in hybrid heating mode by converting electromagnetic energy into heat at 2.45 GHz. Charcoal and SiC plates were used as susceptor and separator, respectively, and nickel powder was used as the interface material. The developed joints were characterized for their microstructural and mechanical properties. The microstructures indicate a complete fusion of nickel interfacing powder with the faying surfaces. XRD results show the formation of metallic nitrides and carbide phases (Cr2N, Fe3N, and Fe2C) and the FeNi phase at the weld zone. Furthermore, the observed average tensile strength of the fusion joints was approximately 61% of base metal. The reduction in the stress and elongation compared to the base metal were 38.67% and 12.68%, respectively. The average microhardness of the microwave joints was monitored as 407 ± 69.27 HV. The results indicate the feasibility of fusion joints of nitronic steel using microwave energy.
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    Challenges in Microwave Processing of Bulk Metallic Materials and Recent Developments
    (Association for Microwave Power in Europe for Research and Education, 2018-07) Mishra, Radha Raman
    In the recent years, microwave energy has been exploited for processing of metallic materials through different heating based processes such as sintering, joining, cladding, casting and drilling. Metallic powders are primarily processed through microwave sintering; whereas, other processes are used to heat/melt/ablate desired portion of the bulk metallic materials. Microwave sintering is the most mature process in terms of the literature and its presence in the industry among these processes. The feasibilities of casting, joining and cladding processes are well documented, though they are yet to become popular in industrial applications as alternatives to the conventional processes. Microwave drilling of non-metals have been demonstrated; however, drilling of the bulk metals using microwave energy is in the investigation stage and needs exhaustive experimentation to get established as an advanced metal machining process. This letter provides an overview of microwave energy based techniques used for processing of bulk metallic materials. The challenges in processing these materials have been identified; processing strategies have been briefly discussed. Future research opportunities in microwave processing of the bulk metallic materials have been outlined.