Faculty Publications

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    Effects of error in time-delay on AEPD source localization using Newton's method: Numerical experimentation
    (Institute of Electrical and Electronics Engineers Inc., 2017) Antony, D.; Punekar, G.S.; Kishore, N.K.
    Newton's method is one of the commonly used methods for acoustic emission partial discharge (AEPD) source localization in power transformers. The major problem in the AEPD source localization is the difficulty in accurately measuring the signal arrival time from the source to the multiple sensors. The exact instant at which the partial discharge (PD) occurs is not known. Therefore, instead of the absolute time, the time-delay in signal reception of each sensor with respect to the sensor nearest to the PD source is estimated. In the present study the effect of time-delay error on the accuracy of the PD source localization is analyzed through numerical experimentations. The solution of the Newtons's method in turn depends on the choice of the initial guess. Hence, different initial guesses are selected for Newton's method randomly. For a fixed set of coordinates for the four sensors and the PD source positions, the time-delays are theoretically calculated. The error is systematically increased in the calculated time-delay to form different groups of time-delays. The PD source is localized using each initial guess for all the groups of time-delays to analyze the effect of error in time-delay on accuracy of PD source localization. The error in time-delay greatly affects the AEPD source localization. Moreover, if Newton's method with a bad initial guess is used then the errors in AEPD source localizations are not systematic. © 2017 IEEE.
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    Implementation of Acoustic Emission Testing to Study the Type of Cracking in Reinforced Concrete Beams
    (Springer Science and Business Media Deutschland GmbH, 2021) Ghosh, S.; Agrawal, R.; Vidya Sagar, R.
    In this experimental study, crack classification in reinforced concrete (RC) beams was carried out using acoustic emission (AE) testing. Two types of under reinforced RC beams were tested in laboratory subjected to four-point bending, and monotonically increased load was applied. The first type of RC beam had shear reinforcement (steel stirrups), and the second type of RC beam had no shear reinforcement. The generated AE during the fracture process in the tested RC beams were used for the crack classification analysis. Gaussian mixture modeling (GMM) of acoustic emission signals was performed. It was observed that the RC beam without shear reinforcement failed suddenly (brittle nature). However, the RC beam with shear reinforcement failed gradually thereby exhibiting ductile nature. In both the RC beams, considerable AE related to shear cracking appeared at a 20–30% peak load. In the case of the RC beam with shear reinforcement, initially, tensile cracks were developed at the bottom of the beam and slowly started widening upward. Diagonal shear cracks started forming near to the supports when the test specimen reaching to collapse. In the case of the RC beam with no shear stirrups, tensile cracks originated at the bottom of the beam. But in this case, the influence of shear cracks developed near to the supports was more pronounced as it propagated rapidly. By comparing the different AE parameters, a steady increase in the number of hits till failure was observed in the case of the RC beam with shear reinforcement. But on the other hand, an abrupt increase in the number of hits was observed after 50% of peak load in the case of the RC beam with no shear reinforcement. The results are useful to study the sensitivity of AE to the shear reinforcement present in the RC beams. © 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
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    Effect of Heating and Fluid Saturation on Certain Physico-Mechanical and Fracturing Behaviour of Concrete
    (Springer Science and Business Media Deutschland GmbH, 2024) Gafur, I.A.; Anilkumar, A.; Parappalli, A.N.; Srinivasan, V.
    Understanding the fracturing characteristics of construction materials under varying environmental conditions is very important in considering the safety of infrastructural facilities for sustainable civil structures. Concrete has been extensively used in construction, and with recent advancements in offshore structures, its strength in adverse conditions is pivotal and hence requires significant attention. This study investigates the variation in the mechanical properties and fracturing behaviour of M25 concrete cubes under different environmental conditions. The cubes were subjected to five different conditions: heating, saturation, and a combination of heating and saturation. Saturation was carried out separately using water and brine solutions. Three cubes were cast for each condition. The physical properties included density and Ultrasonic pulse velocity, followed by mechanical testing for strength. Acoustic emission monitoring was carried out simultaneously along the mechanical testing. Acoustic emission techniques are used to visualize fracturing behaviour of concrete cubes. Fracture thresholds are established to find crack closure and elastic region, and regions of stable crack propagation and unstable crack propagation. The results show that the combination of heating and fluid saturation significantly impacts the physico-mechanical properties of concrete, reducing its compressive strength and increasing its susceptibility to fracture. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.