Faculty Publications

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Subject: search.filters.subject.Acoustic emissions

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    Development of noise spectrum based maintenance guideline for reduction of heavy earth moving machinery noise
    (2006) Vardhan, H.; Adhikari, G.R.
    Heavy earth moving machinery (HEMM) is one of the most important sources of noise in open-pit mines. Several studies carried out earlier indicate that noise produced by HEMM can be reduced by proper maintenance. To reduce the overall noise produced by HEMM it is important to identify the components contributing most to the noise. Maintenance of those components can then be carried out rigorously to reduce the noise. This paper presents the development of a maintenance guideline for reduction of HEMM noise based on sound level emissions and noise spectrum studies. The sound level emission and noise spectrum based maintenance guidelines were obtained through noise measurement of HEMM like dumpers, dozers and front-end-loaders over a period of time and under various test conditions. These guidelines can help the maintenance crew for the reduction of noise from HEMM. © 2006 Institute of Noise Control Engineering.
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    Effects of transformer-oil temperature on amplitude and peak frequency of partial discharge acoustic signals
    (Institute of Electrical and Electronics Engineers Inc., 2018) Shanker, T.B.; Nagamani, H.N.; Antony, D.; Punekar, G.S.
    The behavior of partial discharge (PD) acoustic emission (AE) signals in the transformer oil for a temperature range of 30-75 °C is studied via laboratory experiments. The AE signals are analyzed using the fast Fourier transform (FFT) to obtain the peak frequency and the AE amplitude. A peculiar behavior of reduction in the peak frequency and the AE amplitude observed above 65 °C is reported. An attempt is made to explain the reduction in the AE amplitude after a certain temperature by correlating it with the properties of the transformer oil such as the viscosity and the breakdown voltage. This AE signal analysis is perhaps an important advancement in the PD diagnosis and the PD spectrum analysis at different temperatures in the transformer oil. © 1986-2012 IEEE.
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    Role of longitudinal reinforcement on the behavior of under reinforced concrete beams subjected to fatigue loading
    (Elsevier Ltd, 2019) Prashanth, M.H.; Singh, P.; Chandra Kishen, J.M.C.
    In this work, the role of steel reinforcement in under reinforced concrete beams when subjected to flexural fatigue loading is studied using the acoustic emission (AE) technique. Three-point bend notched beams of three different sizes and with varying reinforcement ratios are subjected to step-wise increasing variable amplitude fatigue loading. The crack mouth opening displacement (CMOD) and AE parameters are analyzed to study the evolution of damage, load carrying and failure mechanisms in under reinforced concrete beams. It is concluded that the presence of reinforcement substantially increases the fatigue life. Further, the CMOD could be used as a criterion for failure in reinforced concrete beams under fatigue loading. © 2019 Elsevier Ltd
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    Statistical analysis of acoustic emissions generated during unconfined uniaxial compression of cementitious materials
    (Elsevier Ltd, 2019) Vidya Sagar, R.; Singh, M.; Deepak, S.; Desai, P.R.
    The article reports a study on the ‘goodness of fit’ of Weibull and Normal (Gaussian) distributions on the compressive strength and the corresponding Acoustic Emissions (AE) of cementitious materials. An attempt has been made to understand the variation of the parameters of the Weibull distribution and the Gaussian distribution carried out on the uniaxial compressive strength data and the corresponding recorded AE parameters. The statistical analysis of ‘Damage Parameter’ based on the peak amplitude of AE signals was also carried out. It was observed that the Weibull distribution was a better fit than Gaussian distribution for compressive strength and damage parameter. But in the case of AE parameters, Gaussian distribution was a better fit. The results obtained from this statistical study may be an addition to the existing knowledge on the statistical approach of AE associated with cementitious materials. A statistical approach may be suitable in predicting the data values without conducting further experiments. The results may be useful to understand the variation of physical properties such as homogeneity and ductility with the variation of compressive strength of cementitious materials and its corresponding AE parameters. © 2019
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    An Investigation on the Influence of Thermal Damage on the Physical, Mechanical and Acoustic Behavior of Indian Gondwana Shale
    (Springer, 2020) Srinivasan, V.; Tripathy, A.; Gupta, T.; Singh, T.N.
    In the present study, the effect of thermal treatment on the physical, mechanical and fracturing behavior of Gondwana shale samples from India was investigated. Acoustic Emission signals were used to identify the changes brought in by temperature variations on the crack damage zones and failure attributes in shale. The results suggested that mechanical parameters such as uniaxial compressive strength, tensile strength (?t), elastic modulus, mode-I fracture toughness (KIC), cohesion, and brittleness index (B1) exhibited a strong negative correlation with thermal damage (Dt). But, the internal angle of friction and brittleness index (B2) showed a reasonable positive relation with thermal treatment. The deformation of the shale was dominated by its clay mineral enrichment, the characteristics of which changed with heating. The intensity of fracturing as observed from acoustic signals was chiefly controlled by the orientation of bedding planes and the degree of thermal treatment. The initiation and propagation of macro-crack were found to be greatly influenced by the degree of thermal damage. Under compression, thermally damaged samples showed similar deformation pattern, while under Brazilian tensile load, the deformation path became inconsistent with increasing temperatures. It was observed that thermal damage in tested shale decreased the layer compaction, which eased the fracturing intensity, thereby reducing the overall strength of the samples. The present investigation concludes that even a slight change of the thermal conditions can substantially alter shale fracturing behavior and failure attributes posing serious safety concerns of deep geo-engineering structures. © 2020, Springer-Verlag GmbH Austria, part of Springer Nature.
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    Implementation of tubercles on Vertical Axis Wind Turbines (VAWTs): An Aerodynamic Perspective
    (Elsevier Ltd, 2022) Sridhar, S.; Joseph, J.; Radhakrishnan, J.
    In recent days, enhancement of Vertical Axis Wind Turbines (VAWTs) by mitigating flow deteriorating effects like dynamic stalling, unsteady wake is given great importance. The following article focuses on implementing four different tubercles on the blades’ leading edge and studying its performance and flow characteristics using CFD techniques. Results indicate that the addition of tubercles generated counter-rotating vortices and delayed flow separation and helped control dynamic stalling. Between azimuth angles 70°–160°, the flow was seen to separate only along the trough regions of the blade and remained attached along the peak regions, thus providing more torque and power. In addition to the enhancements in the flow characteristics, a 28% increase in power coefficient was observed for the optimal configuration at the optimal tip speed ratio. Additionally, a 14% increase in maximum lift generated by the blade was observed. Preliminary aeroacoustics analysis revealed a 12% and 20% decrease in the noise emissions along the blade tip and mid-plane of the turbine, respectively. Hence, it can be shown that tubercles effectively control dynamic stall, reduce noise emissions, and increase the power output of VAWTs. © 2022 Elsevier Ltd
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    Vibro-acoustics analysis of auxetic core quadrilateral sandwich panel
    (Springer Science and Business Media Deutschland GmbH, 2025) Prajapati, V.K.; Pitchaimani, J.
    Vibro-acoustic response characteristics of re-entrant auxetic core quadrilateral sandwich plate are presented. The face sheets and the core of the sandwich panel are made of aluminum material. Mindlin plate kinematics is used to model the plate as a layered structure. Numerical simulation study is performed by using differential quadrature method and Rayleigh integral. Detailed investigation to analyze the effect of geometric parameters of the quadrilateral plate, unit cell parameters, Poisson’s ratio (positive, negative, and zero) of the core and excitation location on the vibro-acoustic performance is presented first time. Results revealed that vibro-acoustic performance of the plate is significantly affected by the geometric properties of the panel and the location of the excitation force. The sound radiation is observed to be high for cores with negative Poisson’s ratio, while sound transmission loss of the panel is not sensitive to the Poisson’s ratio cores. There is no change in response characteristics for a panel with same core density but having different Poisson’s ratio of the core. This work provides new insights into design of lightweight sandwich structures for noise control applications. © The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering 2024.