Browsing by Author "Kumar, J.K.R."

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Failure Analysis of Cooling Tower Fan-Arm
(Springer, 2020) Padasale, B.; Kumar, J.K.R.; Sondar, P.R.; Cadambi, S.; Hegde, S.R.
This work presents failure investigation of cooling tower fan-arms commissioned in a chemical processing plant. The analysis aims at understanding the mechanism and root-cause of the failure. The investigation involves site visits, microstructural analysis, fracture surface analysis, hardness measurements, numerical stress analysis and experimental simulation. Work concludes that the fan-arms failed due to the lack of post-weld heat treatment, which caused localized stress-corrosion and pitting at critical locations that served as crack initiation sites. Fatigue loading condition and presence of residual stresses at the weld enabled easy propagation of cracks that led to recurring premature failure. Based on the root-cause and the mechanism identified in this analysis, proper pre-heating and post-weld heat treatment is recommended to relieve the residual stresses at the critical locations and thus to avoid/minimize such recurring failures in future. © 2020, ASM International.
Failure of a Cooling Water Pump Shaft
(Springer, 2021) Sondar, P.R.; Kumar, J.K.R.; Chawla, S.; Dsilva, P.C.; Hegde, S.R.
This study investigates the failure of an industrial cooling water pump which experienced a drive shaft failure. As per the fail-safe design, during adverse loading of the shaft, key should fail by shear. The key, if fails, can be easily replaced to resume the operation of the pump. However, this investigation reveals that both the key and the shaft failed due to materials processing issues. A detailed failure analysis was carried out including design calculations, visual inspection, dye penetrant inspection, magnetic particle inspection, hardness test, microstructural analysis, and fractography. The study found that the hardness of the shaft varied radially from the core to the surface. The subsurface of the shaft near the keyway, happened to be significantly softer than the key. During operation, the keyway widened by plastic deformation and caused rattling of the key. Due to rattling and vibration, the key developed numerous fatigue cracks and eventually failed by crack linkages. The shaft eventually failed by torsional shear near the midpoint of the keyway. The analysis adjudged hardness variation in the shaft due to materials processing issues as the root cause of the failure. © ASM International 2020.
Failure of Soap Extruder Bolt Assembly
(Springer, 2023) Kumar, J.K.R.; Mogra, N.; Padasale, B.; Dsilva, P.C.; Sondar, P.; Hegde, S.R.
Present work investigates failure of EN8 steel bolt in a bolt–pin assembly that was used as a fastener in an industrial soap extruder. Unexpectedly, EN19 steel pin that is supposedly the sacrificial element in the assembly remained intact. The investigation follows standard failure-analysis procedure comprising, site-visit, visual inspection, metallography, mechanical-testing, design-analysis, numerical stress-analysis, and fractography. The design-analysis finds that the materials of construction were mistakenly swapped between the pin and the bolt that caused plastic-deformation, necking, and eventual failure of the bolt during operational peak-loading condition. The numerical stress analysis illustrates that the bolts failed at the thread-root region that acted as the stress-raiser. Additionally, the investigation finds that poor-quality machining left-behind jagged thread-root profile that increased the stress-concentration furthermore. The metallography and the fractography indicate that a transverse crack that was initiated at poorly machined thread-root led to the brittle fracture of the bolt. The investigation illustrates how human errors can cause recurring failure of critical components leading to production losses and makes suitable recommendations to prevent such failures in the future. © 2023, ASM International.