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Improvement of Anticorrosion Properties of Epoxy Primer Coating on Aluminum Alloy 2024-T3 by Thiosemicarbazone Derivatives
No full textThe effect of adding thiosemicarbazone derivatives on the anticorrosion properties of epoxy primer coatings on aluminum alloy 2024-T3 was investigated. (E)-2-(2,4-dihydroxybenzylidene)hydrazinecarbothioamide (2,4-DHC), (E)-2-(3,4-dihydroxybenzylidene)hydrazinecarbothioamide (3,4-DHC), and (E)-2-(2,3,4-dihydroxybenzylidene)hydrazinecarbothioamide (2,3,4-THC) were supplemented to epoxy primer that is generally used in aircraft paint systems; and its anticorrosion property was examined by electrochemical impedance spectroscopy and salt spray test. Field emission scanning electron microscopy and energy dispersive x-ray analysis were used to study the surface topology of the coating system. 2,4-DHC and 3,4-DHC doped primer coating exhibits good barrier properties, while 2,3,4-THC doped primer coating exhibits good barrier properties along with active corrosion protection
Experimental and Numerical Investigation of Effusion Cooling Performance Over Combustor Liner Flat Plate Model
No full textThis article presents a study of cooling performance of combustor liner of a gas turbine, using a flat plate model. The combustion process in gas turbine engines liberates very high temperature gases, which impacts the properties of the combustor liner. Hence, cooling of liner is important and is carried out by effusion cooling method. Experiments are carried out over a flat plate with staggered effusion holes. The hot mainstream air flows at a Reynolds number of 2.325 × 105, which indicates a turbulent flow. The coolant to mainstream density ratios of 1.3 and 1.5 is maintained by varying the blowing ratios ranging from 0.5 to 2.5. Test plate surface temperature measurements are recorded by an infrared camera and the overall cooling effectiveness in the flow direction is calculated. Numerical validation for conjugate heat transfer analysis is performed using ANSYS workbench and the temperature contours obtained are compared with infrared camera images. MATLAB program is used to obtain the effectiveness contours for experimental and computational fluid dynamics results. The effectiveness contours are found to be similar, showing the increase in effectiveness with the increase in blowing ratios. Density ratios comparison shows that with the increase in density ratio, the overall cooling effectiveness marginally decreases
A comparative study of the behavior of CFRP and GFRP laminates in a plate specimen using modified virtual crack closure technique (MVCCT)
No full textThe applications of polymer composites in aircraft industry have exponentially increased in the recent years due to their high strength to weight ratio. Presence of delaminations in composites is inevitable which affects the structural stability due to reduction in structural stiffness and strength. The degradation of a structural component depends on the geometric characteristics of delamination, nature of loading and material characteristics. Damage tolerance study is thus essential to determine the extent of degradation of the structure due to the presence of delamination. The present paper brings about a comparision between the behaviour of a standard plate specimen made up of Carbon Fibre Reinforced Polymer (CFRP) and Glass Fibre Reinforced Polymer (GFRP) laminates with circular delaminations of varying diameters and subject to compressive load. A constant compressive load in terms of initial displacements was applied on a quasi-isotropic square plate specimen of dimensions 200 mm x 200 mm with a thickness of 2.88 mm of both CFRP and GFRP configurations. A circular delamination was introduced at the centre of the plate and its diameter and position along the thickness direction were varied and studied. Using ABAQUS codes of practice, Strain Energy Release Rate (SERR) was computed. The principles of
Modified Virtual Crack Closure Technique (MVCCT) was used to compute SERR. Delamination propagates when the computed mixed mode energy release rate exceeds the critical value, GC. Depending on the external loading and material properties, Total strain energy release rate, GT (GT=GI+GII+GIII) was used to predict growth of delamination. The onset of delamination growth was determined by plotting the values of (GT/GC) across various delamination sizes along the thickness of the plate and reported
Fine-tuning resource allocation of apache spark distributed multinode cluster for faster processing of network-trace data
No full textIn the field of network security, the task of processing and analyzing huge amount of Packet CAPture (PCAP) data is of utmost importance for developing and monitoring the behavior of networks, having an intrusion detection and prevention system, firewall etc. In recent times, Apache Spark in combination with Hadoop Yet-Another-Resource-Negotiator (YARN) is evolving as a generic Big Data processing platform. While processing raw network packets, timely inference of network security is a primitive requirement. However, to the best of our knowledge, no prior work has focused on systematic study on fine-tuning the resources, scalability and performance of distributed Apache Spark cluster (while processing PCAP data). For obtaining best performance, various cluster parameters like number of cluster nodes, number of cores utilized from each node, total number of executors run in the cluster, amount of main-memory used from each node, executor memory overhead allotted for each node to handle garbage collection issue, etc., have been finetuned, which is the focus of the proposed work. Through the proposed strategy, we could analyze 85GB of data (provided by CSIR Fourth Paradigm Institute) in just 78 seconds, using 32 node (256 cores) Spark cluster. This would otherwise take around 30 minutes in traditional processing systems
Estimating pilots' cognitive load from ocular parameters through simulation and in-flight studies
No full textEye tracking is the process of measuring either the point of gaze (where one is looking) or the motion of an eye relative to the head. This paper investigated use of eye gaze trackers in military aviation environment to automatically estimate pilot's cognitive load from ocular parameters. In the first study, we used a fixed base variable stability flight simulator with longitudinal tracking task and collected data from 14 military pilots. In a second study, we undertook four test flights with BAES Hawk Trainer and Jaguar aircrafts doing air to ground attack training missions and constant G level turn maneuvers up to +5G. Our study found that ocular parameters like rate of fixation is significantly different in different flying conditions. It also significantly correlated with rate of descent during air to ground dive training task, normal load factor (G) of the aircraft during constant G level turn maneuvers and pilot's control inceptor and tracking error in simulation tasks. Results from our studies can be used for real time estimation of pilots' cognitive load, providing suitable warnings and alerts to the pilot in cockpit and training of military pilots on cognitive load management during operational missions
Structure, dielectric and ferroelectric properties of modified KNN perovskite ceramics
No full textInfluence of overstoichiometric KCl additives on structure parameters, microstructure, dielectric, and ferroelectric properties of (K0.5Na0.5)NbO3–LiNbO3 ceramics have been studied. Changes in temperatures of phase transitions, improvements of dielectric and ferroelectric parameters were revealed depending on composition of the samples
Dual band polarization insensitive frequency selective surface absorber
No full textThis work presents dual band, polarization insensitive and angular stable radar absorber structure. Here, proposed absorber unit cell has two resonator structures M and N. Each resonator provides absorption at distinct frequencies in X and Ku band. Simulation results in different cases show that the structure is polarization insensitive and angular stable up to 60 0 . Calculated effective impedance plot and surface current distribution at the top and bottom surface supports the absorption mechanism at the resonance frequencies. To verify the simulations, a prototype of absorber is fabricated on FR-4 substrate and tested in an anechoic environment
Wet spinning of low cost carbon fiber precursor-lignin incorporated polyacrylonitrile co-polymer fiber
No full textLow cost carbon fiber from lignin is a promising biobased feedstock since lignin is by product in many industries. In the present work spinning of concentrated solution of lignin blended with polyacrylonitrile copolymer have been investigated. The wet spinning experiments of PAN/Lignin blend solution to obtain the precursor fiber in continuous form have been successfully demonstrated. Rheological measurements are carried out to optimize the wet spinning process parameters such as to ascertain the dissolution and extrusion temperature. The gel formation temperature of PAN/Lignin blend solutions are determined by the plot of tan δ Vs temperature plot. The FTIR analysis confirms that there is no discernible chemical reaction or crosslinking between PAN and lignin. The resulting precursor fiber from PAN/Lignin blend solution displayed a tensile strength and modulus of 2.36 gpd and 76 gpd respectively.
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Vibration Analysis of Heterogeneous Gearbox Faults using EMD Features and SVM Classifier
No full textIOP Conference Series: Materials Science and Engineering
PAPER • THE FOLLOWING ARTICLE ISOPEN ACCESS
Vibration Analysis of Heterogeneous Gearbox Faults using EMD Features and SVM Classifier
Setti Suresh1 and VPS Naidu2
Published under licence by IOP Publishing Ltd
IOP Conference Series: Materials Science and Engineering, Volume 624, 1st International Conference on Mechanical Power Transmission 11–13 July 2019, Chennai, India
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Abstract
Gearbox is one of the important mechanical power transmission device most commonly used in automobiles and industries to get the desired change in speed and torque. The gearbox fault diagnosis has given utmost importance for its significance in preventing halts of a mechanical system and guaranteeing an advantage of sufficient maintenance. This paper presents the vibration analysis of heterogeneous gearbox faults using EMD features and SVM classifier. The vibration signal is converted into intrinsic mode functions (IMF) with decreasing order of frequencies using empirical mode decomposition (EMD) method. Feature vector consisting of information theoretic features have been computed for each IMF and concatenated to form a feature set. By using random permutations, the feature set has been divided into training and testing sets. The support vector machine (SVM) algorithm has been used as a classification technique to diagnose the gearbox faults, which consists of five-class classification. The accuracy of the developed algorithm has been validated using 100 Monte Carlo runs. A comparative study has been carried between computed features and varying IMF components. The observations made were - clear discrimination of the gearbox faults and improved classification accuracy, which contain - chipped tooth, missing tooth, root fault, surface fault and healthy working state of the gear
Design and Development of a Hybrid Broadband Radar Absorber Using Metamaterial and Graphene
No full textStealth airborne systems are low observable platforms, which bring together technologies in the field of aerodynamics, electromagnetics, and material science. Radar absorbing materials/structures play a key role in the design of such stealth airborne platforms. In this paper, a radar absorber has been fabricated based on the design of a nonperiodic metallic patch coated with graphene. The simulation results of the novel design over an ultrawideband (1-60 GHz) yield good absorption (99.93%). With the constraint of fabrication facility, a small unit cell of the structure has been fabricated and measured. The measurement results show a good agreement with the simulation results. The absorption bandwidths, thickness, and weight of the structure are some of the key elements that were considered in the design model. It has been observed that the design allows the electric potential tuning by changing the Fermi energy of the graphene layer. The significant absorption of the proposed design in ultrawideband shows that it has potential applications in the RF stealth technology