Vellore Institute of Technology (VIT) is a private university located in&nbsp;Tamil Nadu, India. Founded in 1984, as Vellore Engineering College, the institution offers 20 undergraduate, 34 postgraduate, four integrated and four research programs. It has campuses in Vellore, Amravati, Bhopal and Chennai.

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VIT University

Mechanical

Interaction of polydisperse droplets in a turbulent air flow features prominently in a wide range of phenomena, such as warm rain initiation as an example. In the current study, we present an experimental investigation on the effects of initial droplet field characteristics on the maximum droplet size growth. By performing experiments in a vertically oriented air flow facility, the air flow turbulence was able to be controlled through the mean flow velocity and an active turbulence generator. The initial droplet field characteristics (droplet diameter range of 0-120 m) were varied using spray nozzles of different flow numbers. Based on quantitative measurements of the droplet size distribution at various spatial locations using phase Doppler interferometry (PDI), we estimated the droplet size growth rate as a function of turbulence intensity, initial droplet number density and initial mean droplet size. For each (,), we observed the occurrence of an optimum turbulence intensity, with the corresponding maximum droplet size growth rate being. Two different trends were observed. When and were simultaneously increased and decreased, respectively, their competing influences resulted in small variations in. In contrast, when was held constant with a corresponding Stokes number smaller than unity, there existed a threshold above which increased rapidly with. These trends were then understood through long-distance microscopy (LDM) measurements. Beyond the aforementioned threshold, the fraction of uncorrelated small-sized <![CDATA[(St droplet pairs was found to rapidly increase with. Further detailed analysis of droplet tracking in the LDM images identified that the velocity fluctuations in the small-sized droplet pairs being induced by close encounters with inertial droplets was the underlying mechanism for the rapid increase of with. This mechanism potentially explains how droplet collisions can be enhanced in small droplets if the droplet field is sufficiently polydisperse. ©

School of Mechanical Engineering

Chennai Campus

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Journal of Fluid Mechanics

Experimental study of the effects of droplet number density on turbulence-driven polydisperse droplet size growth

The effect of uniform temperature on dynamic characteristics of a sandwich plate with functionally graded (FG) core is analyzed by finite element methods. The top and bottom of the sandwich plate are considered as metal and ceramic, and the core is considered as functionally graded. Aluminum and alumina materials are used as top and bottom face sheets, and the same materials are graded through thickness for FGM core. The material properties of FG core vary throughout the thickness direction according to the power law index. The effective material properties are calculated using the Voigt technique. The Buckling temperature of sandwich plate is analyzed for different boundary conditions and used as criteria to study the effect of temperature on natural frequencies and mode shapes. © 2021, Springer Nature Singapore Pte Ltd.

Lecture Notes in Mechanical Engineering

Studies on Dynamic Characteristics of Sandwich Functionally Graded Plate Subjected to Uniform Temperature Field

Automatic speech recognition (ASR) has gained a lot of popularity in the mobile robotics, where the commands could be provided to the robot wirelessly to maneuver. A navigation system combined with ASR is a complex system to carry out, because the system has difficulty in recognizing the voice commands when the environment involved already has disturbances like road noise, air conditioner, music, and passengers. The objective of this research is to operate a mobile robot with a single-arm manipulator, where the robot can perceive the speech and it can react to the individual speech commands provided by the operator swiftly and precisely. In order to recognize the speech, mel-frequency cepstral coefficient (MFCC) speech recognition algorithm is chosen and implemented in MATLAB. Various training and testing have been done in MFCC algorithm where it has to carry out the real-time processing of speech data and respond to it. Based on both the training and testing the voice commands collected from the five test subjects both male and female, the speech recognition system achieved 89% efficiency for the test database. © 2021, Springer Nature Singapore Pte Ltd.

Speech Recognition Using Neural Network for Mobile Robot Navigation

Friction stir welding (FSW) technique was preliminary developed to join various low strength and high strength alloys by considering different inputs and known to surpass the flaws which occur in conventional welding processes. The present study is focused on the FSWed interlock lap joint of AA7475-T7 using three-level three factor (33) full factorial design methodology to study the correlation among process parameters with the lap shear strength and hardness. To compare the strength and hardness of interlock lap joint, a typical lap joint has been made with an optimized input parameter obtained from the FSW interlock lap joint. Microstructure analysis, hardness and tensile strength of FSWed interlock lap joints and typical lap joints were done to analyze the robustness of the welds made. Results proved that the strength of FSWed interlock lap joints is high compared to typical lap weld with a ultimate tensile strength of 172.88 N and hardness of 200 HV when the process parameter level is at tool rotation speed of 1400 r/min, welding speed 30 mm/s plunge speed rate 0.06 mm/s. At the tool rotation speed of 1400 r/min dynamic recrystallization of the material occurs which thereby leads to the formation of fine grains in the SZ of the weld metal. © IMechE 2021.

Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science

Microstructure and mechanical properties of interlock friction stir weld lap joint AA7475-T7 using fractional factorial design

The objective of this study is to prepare a bio-based and light-weight electromagnetic interference (EMI) shielding material in the range of 8–12 GHz. Organic castor oil-based polyurethane (PU) foam was synthesized by the mechanical stirrer mixing process, whereas absorption and hydrothermal reduction processes have been used to reinforce the multi-walled carbon nanotube (MWCNT), cupric oxide (CuO) and bamboo charcoal (BC) nanoparticles in the organic PU foam. The EMI shielding properties of the PU foam composite were tested using a vector analyzer test setup. Identification of the structural property of the nanocomposite was analyzed using field-emission scanning electron microscopy images. The density of the organic PU foam composite reinforced with nanoparticles was calculated with the help of mass and volume. Response surface methodology has been used to systematically design and analyze the experiments of EMI shielding effectiveness (EMI SE) and the physical properties of the reinforced foam. Using the EMI SE experimental results, mathematical models were developed to forecast the results and validate them with error estimation. An optimization study has revealed that 0.75 wt.% of MWCNT, 1.5 wt.% of CuO, and 1.5 wt.% of BC are the optimum parameters with 0.063750 g/cm3 density for obtaining the maximum EMI SE. © 2021, The Minerals, Metals & Materials Society.

Journal of Electronic Materials

An Investigation of EMI Shielding Effectiveness of Organic Polyurethane Composite Reinforced with MWCNT-CuO-Bamboo Charcoal Nanoparticles

The concept of reuse and recycle plays a very important role in using waste materials effectively. Fabrication of green composites, which adopts the reinforcement of natural and biodegradable fibres in place of synthetic fibres, is a constructive way to achieve reusability and recyclability. Hence, the sugarcane fibre, fly ash, and carbon nano tube are selected as reinforcement/filler materials for fabricating epoxy polymer matrix composite. This work is intended to investigate the flexural behaviour of the fabricated epoxy polymer composite by varying the wt. % of CNT/sugarcane fibre/fly ash. Central composite design of response surface methodology, one of the concepts of design of experiments, is used to make the experimental specimens. Further, analysis of variance is used to accomplish the influence of CNT/sugarcane fibre/fly ash on the flexural behaviour of composite. Optimized parameters are obtained to achieve the improved flexural behaviour, and the same is confirmed by the confirmation experiment. Copyright © 2021, IGI Global.

International Journal of Surface Engineering and Interdisciplinary Materials Science

Flexural analysis of epoxy polymer composite reinforced with sugarcane fibre/fly ash/carbon-nanotube

This study presents the finite element analysis of the weld joints used in the off-highway vehicles. A coupled field thermal and static analysis is performed to find the residual stresses in weld and its effect on the fatigue life of the double plate full penetration weld joint. The Design of Experiments approach, via Response Surface Methodology (RSM), is used considering the influence of the parameters like Plate Thickness, Load and Prep angle on the fatigue life. The central composite design, a model in RSM is used to minimize the number of simulations. The Analysis of Variance (ANOVA) is carried out to find the influences of Plate Thickness, Load and Prep angle on the fatigue life. The Regression Equation, obtained through ANOVA, helps to understand the influences of parameters on fatigue life. Later the regression equation is validated with finite element results. The Optimization study is carried out to find optimized parameters for maximum fatigue life. Confirmation simulation using finite element analysis reveals the integrity of optimization study. © 2021, Politechnica University of Bucharest. All rights reserved.

UPB Scientific Bulletin, Series D: Mechanical Engineering

Prediction of fatigue life of full penetration weld joint using thermal elasto plastic properties incorporating residual stress effect

Increase in production capacity of industries in every field results into generation of huge amount of waste materials. These wastes can be utilized in an effective manner; one of those ways is fabricating a green composite which uses natural fibres and biodegradable materials in place of synthetic fibres as reinforcements. This is the main drive behind selecting sugarcane fibre and fly ash as our reinforcement materials for making epoxy polymer matrix composite. For further improvement in mechanical properties, carbon nano tube (CNT) is also used as reinforcement material in the composite. It is intended to investigate tensile behaviour of the composite by varying the wt. % of CNT / sugarcane fibre / fly ash in epoxy polymer matrix. Experimental specimens are made using Central Composite Design (CCD) of Response Surface Methodology (RSM), one of the Design of Experiments (DOE) approaches. Determining the influence of CNT / sugarcane fibre / fly ash reinforcements on the tensile behaviour of epoxy composite is achieved by using ANOVA. Results reveal the positive effect of sugarcane on yield strength and Young’s modulus of the composite and that of fly ash and CNT on ultimate tensile strength. Optimized parameters are obtained to achieve improved tensile behaviour and the same is confirmed by confirmation experiment. © 2021, Politechnica University of Bucharest. All rights reserved.

Tensile behaviour of sugarcane fibre / fly ash / carbon nano tubes reinforced epoxy composites

Friction stir welding is a solid-state joining process to join similar or dissimilar metals, which uses the friction developed between the metals to join them. Friction stir welding is an efficient way to join the metals but the welding defects are a little difficult to find through naked eyes. Hence, there is a chance of it being unnoticed even in final inspection in industries. So the welded joints are inspected by machine vision, using camera and an intelligent system. After obtaining the images of the welded joints and processing them using MATLAB, they are differentiated according to the various defects in them, using machine learning technique. For this, the statistical features of the image are extracted and they are classified into different defects using classifiers like Decision Trees, Discriminant Analysis, Support Vector Machine and Nearest Neighbour. © 2021 Institute of Physics Publishing. All rights reserved.

Fulltext

Journal of Physics: Conference Series

Welding defect identification with machine vision system using machine learning

An analytical investigation carried out on free vibration characteristics of functionally graded graphene reinforced nanocomposite (FG-GRC) plate under different non-uniform edge loads is presented. Graphene nano-platelets (GPLs) are homogeneously dispersed and graded by varying weight fraction through the thickness. An analytical method based on strain energy approach is adopted to estimate the buckling load. Natural frequencies of the FG-GRC plate are attained using analytical solutions derived based on Reddy's third-order shear deformation theorem (TDST). Results revealed that buckling and free vibration behavior of the plate is influenced by the GPLs dispersion pattern and weight fraction under non-uniform edge loads. It is also observed that buckling mode and the fundamental vibration mode of the plate under combined tensile-compression load is entirely different from the other non-uniform edge load cases. © 2020 Elsevier Ltd