Browsing by Author "Dsilva, P."

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    Biodegradation of PEEK Piston Rings
    (Elsevier Ltd, 2021) Shetty, P.; Dsilva, P.; Sondar, P.R.; Kumar, B.G.; Hegde, S.
    Polyether ether ketone (PEEK) is considered a high performance thermoplastic with excellent mechanical, chemical, and thermal properties. It is generally believed that this material is chemically and biologically inert, and is used for various biomedical and industrial applications, especially in the form of fiber reinforced polymeric composites. Contrary to the general belief, the present work reports the biodegradation of PEEK piston rings that were used in a reciprocating CO2 compressor. A series of circumstantial and direct evidences were collected by following various tests and characterization methods to confirm the degradation of the piston rings by bacterial attack. The bacterial cells were extracted from the degraded piston rings, cultured in agar medium and then studied using scanning electron microscope. An experimental simulation was carried out by depositing and incubating a bacterial culture on the pristine surface of a PEEK specimen. The simulation experiment revealed an early stage of bacterial degradation in the form of cracking of the PEEK specimen surface. The results of various tests, characterization, and the experimental simulation presented in the paper suggest that PEEK based composites degrade due to enzymatic hydrolysis process by Myxococcus Xanthus, the rod–shaped soil bacteria. © 2021
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    Creep cavitation damage of K-type thermocouples
    (Elsevier Ltd, 2023) Rakshan Kumar, J.K.; Bhattacharjee, D.; Dsilva, P.; Praveen, R.; Hegde, S.R.
    This work investigates premature failure of K-Type thermocouples that were used in a chemical processing plant. The work presents a detailed metallurgical failure analysis involving, site visit, visual inspection, metallography, optical microscopy, scanning electron microscopy, and fractography. The analysis reveals that the thermocouple wires endured creep cavitation damage during service and eventually failed by creep-rupture. Interestingly, the influence of creep on the degradation of industrial thermocouples is not detected and reported thus far. By presenting analytical stress calculations using temperature dependent materials properties, the current work reveals that the thermal expansion mismatch between various materials of thermocouple causes high tensile stresses in the thermocouple wires during elevated temperature services. The work concludes that high tensile stresses at elevated temperature operation caused premature creep failure of the K-type thermocouples. © 2022