Research Publications

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    Application of flux cored arc welding (fcaw) without pre-heating for heavy structures in ship building fabrication & construction of heavy offshore structural steels /
    (Journal of Construction Engineering, Technology & Management, 2020-06-04) Rao, K. S. Jagan; Nagesh, B. H.; Kumar, I. N. Niranjan
    In fusion welding processes, the reason often given to explain the need for preheating, controlling the inter pass temperature (in multi-pass welds), and post-weld heat treatment (PWHT) is to reduce the risk of residual stresses and it can be removed by heating weldment in the heat affected zone (HAZ). Cold cracking is a hydrogen embrittlement phenomenon, often referred to as hydrogen induced cracking or HAZ cracking. During the construction and fabrication of heavy offshore structures, several failures have been noticed during the welding of structures with higher plate thicknesses where preheating is not properly done. However, many welding engineers cannot readily arrange the preheating in offshore structures, oil and gas installations and in other locations where heavy ship building activities are being done. In this context, experimental studies have been performed on transient heat transfer in welding distortion control by using flux-cored arc welding process (Dual Shielded-DS) without application of pre-heating as specified by the various welding international codes. The authors have studied various samples and tested them in which the FCAW welding has been done with and without preheat. The eight-step welding method enunciated by welding standards with preheating has been slightly modified into again eight step method without preheating and still obtained the same strength, toughness, hardness and stiffness. The use of tubular electrodes with very small diameters has extended the use of this process to work pieces of smaller section size. A main advantage of using flux-cored arc welding (DS) is the ease with which specific weld-metal things can be developed. By adding alloying elements to the flux core, resulting in increased tensile strength and hardness. The process is easy to automate and is readily adaptable to flexible manufacturing systems and robotics.
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    Wear and friction properties of H-Al-17Si alloy with dry, lubrication and coated (DLC-Star) conditions under HFRR /
    (OJS/PKP, 2021-12-16) Nagesh, B. H.
    Dry, lubrication (SAE15W40), and coated (DLC-Star) reciprocating tribological tests on rapid solidified AlSi17Cu3.5-4Mg0.6-0.8 alloy was conducted using a high frequency linear reciprocating rig (HFRR) at ambient temperature. The alloy fabricated with the rheo-stir squeeze casting procedure under T-6 condition. However, at different loading (0-30 N) conditions, wear and friction properties of rapid solidified H-Al-17Si alloy are investigated. It is observed that the lower friction coefficient value obtained for DLC-Star coated H-Al-17Si alloy compared to dry and lubrication conditions. Though, for dry and lubricated sliding, the obtained wear coefficient values are 2.9X10-3 mm3/N.m and 4.0X10-4 mm3/N.m. A lower coefficient of wear value of 5.4X10-5 mm3/N.m was recorded with DLC-star coating under dry conditions. The alloy wear coefficient values first increases with applied load (up to 20 N) and then decreases (20 N to 30 N). EDS, AFM surface roughness profilometer, SEM, and advanced metallurgical microscope (AMM) analysis techniques used for the characterization of surface morphologies. The developments in friction and wear coefficients were fundamentally ascribed to the dispersion and size of primary Si elements and the development of tribo-oxide films on the rapid solidified AlSi17 alloy coated (DLC-Star) surfaces.
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    Friction and wear properties of rapid solidified H-Al-17Si alloys processed by UV assisted stir - squeeze casting with DLC-Star (CrN + a-c:H) coating under HFRR /
    (Faculty of Engineering, 2020-12-14) Nagesh, B. H.
    Tribological properties of rapid solidified hyper eutectic AlSi17Cu3.5-4Mg0.6-0.8 (H-Al-17Si) alloy were investigated under different loading conditions. The alloy was produced by the rheo-stir squeeze casting process with the T-6 condition. Experimental studies were conducted using high frequency linear reciprocating rig (HFRR) with a ball-on-plate geometry. The effect of applied load (10-50 N) on the wear and friction (COF) coefficients were studied under dry, lubricated (SAE15W40), and coated dry (DLC-Star) sliding conditions. For dry and lubricated sliding, COF values of hyper eutectic AlSi17Cu3.5-4Mg0.6-0.8 alloy were 0.26 and 0.042. A lower COF value of 0.013 was recorded with DLC-star (CrN + a-c:H) coating under dry condition. Whereas, the least wear coefficient is also observed with DLC-star coating (4.6X10-5 mm3/N.m) compared to the dry and lubricated sliding conditions (2.7X10-3 mm3/N.m and 3.8X10-4 mm3/N.m). The developments in COF and wear coefficients were mainly attributed to the distribution and size of primary Si granules and the formation of transfer layers on the coated surfaces of AlSi17Cu3.5-4Mg0.6-0.8 alloy. Surface morphologies were examined using SEM, AFM, surface roughness profilometer, and advanced metallurgical microscope (AMM) analysis techniques.
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    Measurement of small vessel machinery vibration induced acoustic signature levels /
    (Journal of Naval Architecture and Marine Engineering, 2019-12-26) Kumar, G. V. V. Pavan ; Nagesh, B. H.
    Ship vibrations, airborne and underwater noise levels have always been a challenging topic from a performance point of view in ship design, building and operation. The measurement shall help in monitoring the self-noise and the technical state of their machinery mechanism. The vibration levels on the main engine and auxiliary Genset foundation, airborne noise levels of the engine room and underwater self-noise levels of a small mechanized fishing trawler was measured at the jetty in idling condition. The vibration levels on the foundation measured the average value of 0.207 mm/s for the main engine and 1.36 mm/s for auxiliary Genset. The airborne noise levels measured 99 dB (A) in the engine room. The peak underwater sound pressure levels measured 162 dB re 1µPa. The response spectra indicate the peak vibration and noise levels in the lower frequency region <1.2 kHz. The machinery excitation forces transferred to the hull surface as pressure fluctuations which generated the airborne and underwater noise levels. Though the measurement limited to jetty conditions, detailed analysis can be useful for detection, classification, and tracking of small vessels.
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    Design of high speed slamming planing craft
    (Indian Maritime University, Visakhapatnam, 2019) Hadassah, T.; Nagesh, B. H. ; Niranjan Kumar, I. N.
    This paper chronicles the hypothetical study, test results, design aspects such as stability characteristics, vessel’s high speed performance i.e. short take-off and landing distance, and vertical take-off and landing characteristics, operating at low shallow draft,high speed propulsion efficiency sans cavitation interference, less machinery operating noise, compact hullform & structure, efficient conveyance and applications of High Speed Slamming Planing craft (HSSP). Amongst High Speed Performance Marine Vessels, this is one of the unique design proposition; based on the research, facsimile, exploratory and hypothetical study of a genus of large corytophanid lizards also known as basilisks moving on the water surface and on parallel study of the small high speed vessels.