Faculty Publications

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Publications by NITK Faculty

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    A comparative study on the effectiveness of system parameters in monitoring pre-load loss in bolted joints
    (Springer Verlag service@springer.de, 2018) Anginthaya, K.; Kuchibhatla, S.A.R.; Gangadharan, K.V.; Kishan, A.
    This article presents the monitoring of bolt loosening in a single bolted lap joint between two steel beams. The bolt loosening is initially studied using system modal parameters for various boundary conditions. Natural frequency and modal damping ratio in lower modes were not found to be reliable. Transmissibility function was seen to have a more reliable trend to identify the state of the joint. An in-house setup was developed to produce loosening in the bolted joint. Testing configuration was optimized by structural analysis. Strain measurements were carried out using Fiber Bragg-grating sensors while sinusoidal load was applied on the test structure. The results have been used to discuss a viable approach to identify the health of, or recognize a loosening trend, in a bolted joint. © 2018, The Brazilian Society of Mechanical Sciences and Engineering.
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    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.