Browsing by Author "Prasad, V. V. S."

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    Assessing underwater noise levels during various port activities at the Visakhapatnam channel
    (Indian Maritime University, Visakhapatnam, 2019) Pavan Kumar, G. V. V.; Prasanna Kumar, A.; Prasad, V. V. S.
    Transport infrastructure is one of the most important factors for country’s progress or economic growth. Ports serve as important transportation hubs that facilitate goods movement. Visakhapatnam Port is the second largest port by volume of cargo handled located in the east coast of India. Under the modernization program the port is capable for handling vessels up to 14.5 m by maintenance dredging and some jetties extension with piling activity. The major activities of the port operation are the vessel handling using tugs and movement of other vessel within the inner harbor of the Visakhapatnam channel. The underwater noise levels of the channel are measured by deploying Omni-directional hydrophone at different location along the channel and the radiated noise levels due to the tug boat operations. The TASCAM data recorder is used to convert the voltage signal to sound file and Fast Fourier Transformation spectral analysis program for post-processing the time and frequency domain spectrum. The tug machinery self-noise indicated a peak amplitude of 157 dB re 1μ Pa at 425 Hz. The jetty modification work recorded the piling activity radiated noise levels as indicated in the spectrogram in the lower frequency of nearly one second duration. The anthropogenic noise due to tugs movement and the piling activity have major influence in increasing the ambient noise of the region. However, there are no evidence of presence any marine mammals getting effected due to the continuous shipping and other activities in the region. The present study shall help to develop measures to reduce the increase in the ambient noise levels of the region due to various anthropogenic sources as part of a major environment impact assessment study for developing a green port.
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    Study of microstructure and corrosion effects of precipitation hardened high strength aa-7xxx aluminium alloy subjected to cryo rolling
    (Indian Maritime University, Visakhapatnam, 2019) Phaneendra, Y.; Harish Kumar, K.; Niranjan Kumar, I. N.; Prasad, V. V. S.
    The strength and life of an alloy is the primary parameter taken into consideration while building hulls and superstructures for marine applications. Usually AA-7xxx is widely used for these applications and hence is chosen for the present investigation. Cast AA-7xxx alloy reveals distribution of soluble intermetallic compounds in the α-aluminium matrix. In order to improve the mechanical properties and condition the microstructural features, precipitation hardening (solutionizing and ageing) treatment was carried out by varying time and temperature. Ageing treatment was carried out at 120°C varying time interval. Thermo-mechanical treatment, in particular, cold rolling and cryo rolling(-190ºC) is a unique technique to produce super high strength aluminium alloys with elongated grained structure. In order to conduct the rolling at room temperature, the alloy ingot was rolled from 6mm to 1mm with 85% reduction in thickness. Detailed microscopic analysis was done using optical and electron microscopy to understand the phase and structural evolution during ageing. Evolution of coherent precipitates and their morphology were studied using transmission electron microscope. A potentio-dynamic polarization study was performed to evaluate the corrosion behaviour of AA-7xxx series aluminium alloy processed in 3.5% NaCl solution at different conditions. The aged, cold rolled and cryo rolled alloy is found toexhibit better corrosion resistance characteristics in comparison with other alloys.