Faculty Publications
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Item Modeling and experimental studies on the dynamics of bolted joint structure: Comparison of three vibration-based techniques for structural health monitoring(Springer Science and Business Media Deutschland GmbH info@springer-sbm.com, 2020) Deka, A.; Rao, A.; Kamath, S.; Gaurav, A.; Gangadharan, K.V.Detection of inadequate tightening in bolted joints is quintessential to ensure structural rigidity and to prevent catastrophic failure. Studies show that 30% of assembly failures occur due to inadequate tightening. In the present study, three vibration-based techniques are presented and compared to detect inadequate tightening of bolted joints. Variation in the damped natural frequency, variation in the damping ratio, and variation in the dynamic joint stiffness are studied with varying tightening torques in the bolted joint. The results show that all the three dynamic parameters vary with the tightness of the bolted joint. Dynamic joint stiffness varies significantly as opposed to the damping ratio and damped natural frequency as tightening torque reduces. In order to verify the results of dynamic stiffness method, ANSYS is used to model and analyze the joint. The experimental setup used to calculate the parameters consists of two Euler–Bernoulli beams connected with single lap bolted joint. © Springer Nature Singapore Pte Ltd 2020.Item Effects of High Cyclic Strains on Dynamic Properties of Cohesionless Soils(Springer Science and Business Media Deutschland GmbH, 2025) Akarsh, P.K.; Chaudhary, B.; Sajan, M.K.; Chikkanna, T.; Talkad, P.Soils can experience large cyclic shear strains (>1%) under dynamic loading circumstances such as earthquakes. Determining dynamic properties such as damping ratios and shear modulus is crucial in the design of earthquake-resistant structures. From past studies, it was understood that the dynamic behaviour of soils at higher strains (>0.01%) is different from soils subjected to lower strains (<0.001%) because of nonlinear stress–strain behaviour and damping characteristics at higher strains. Furthermore, it was evident that the majority of tests were carried out on lower strains and only few numbers of studies were reported on tests for higher strains. Hence in this study, the dynamic properties for locally available cohesionless soils tested under high cyclic strains are presented. Generally, the dynamic properties were determined up to strain levels <1% considering a symmetrical hysteresis loop. But the loop becomes asymmetric as the strain level increases and due to which, dynamic properties are over-estimated. So, in this study, the dynamic properties of saturated sand were determined by an actual asymmetric hysteresis loop. Strain-controlled cyclic triaxial tests were conducted on reconstituted soil specimens at a low frequency (0.25 Hz) for variable peak strain levels (0.15–1.5%). The specimens were prepared at different relative densities (30–90%) and consolidated at an effective confining pressure of 100 kPa. The findings of the study revealed that the soil’s shear modulus would degrade more quickly or that the modulus reduction ratio would reduce at higher strain levels (γ ≥ 1%) due to an increase in pore water pressure during undrained cyclic loading. It also turns out that at higher strain values (>1%), the damping ratio significantly decreased. Hence, it is not obvious to extrapolate the trend seen for γ < 1% to get the results for γ > 1%. This work would be helpful for geotechnical practicians and researchers to have insights into the existing methodology for finding the dynamic properties of cohesionless soils at higher cyclic strains. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.Item Response of fly ash-reinforced functionally graded rubber composites subjected to mechanical loading(2012) Doddamani, M.R.; Kulkarni, S.M.A novel approach to estimate the Young's modulus of a functionally graded rubber composite (FGRC) from the damping ratio is demonstrated with the examples of unreinforced and fly ash-reinforced materials. FGRC coupons were prepared using the conventional casting technique. The occurrence of gradation in the specimens was attributed to the variable density of particles present in the fly ash, settling at different depths. The technique of free vibrations was used for experimentation. The damping response of the FGRC specimens was studied. The results obtained from the experiments showed that, with growing filler weight fraction, the Young's modulus of the composite increased. The empirical model developed to predict the magnitude of the modulus turned out to be in good agreement with experimental data. © 2012 Springer Science+Business Media, Inc.Item Vibration analysis of fully and partially filled sandwiched cantilever beam with magnetorheological fluID(Taylor's University, 2020) Srinivasa, N.; Gurubasavaraju, T.M.; Kumar, H.; Arun, M.This paper presents the experimental and computational study on damping effect of the fully and partially filled sandwich cantilever beams. The sandwich beams referred as adaptive beams have a core layer filled with magnetorheological fluid (MRF) between two aluminium face plates. Forced vibration tests were conducted under different magnetic fields with the application of external force in the form of sinusoidal sweep excitation using an electrodynamic shaker. Effect on damping and natural frequency due to change in MR fluid core thickness of 2 mm, 4 mm and 6 mm for the fully filled beam and fluid core length of 75 mm, 150 mm and 250 mm for partially filled beam were investigated. Modal and harmonic analysis of the MR sandwich beams were carried out using FE analysis. The results indicated that in the case of the fully filled beam, a reduction in the natural frequency with the increase in MR fluid core thickness and a better damping at 2 mm fluid core thickness were observed. Also, in the case of the partially filled beam a reduction in natural frequency and improvement in damping is found with the increase in core length and magnetic field. The results of these analyses can be useful in designing the sandwich beams for structural application. © School of Engineering, Taylor's UniversityItem Effect of clamshell powder on the mechanical and damping properties of epoxy-bamboo composites(SAGE Publications Ltd, 2024) Anand, K.J.; Ekbote, T.; Doddamani, S.; Ashoka, E.Compared to single natural fibre composites, hybridising natural fibres with filler particles presents a promising avenue for enhancing composites physical, mechanical, and damping properties. This study delves into incorporating clamshell powder, a filler derived from clams’ hard protective outer shells, into polymer composites. The focus is on investigating the potential of clamshell powder as a filler material to augment the mechanical and damping properties of epoxy-bamboo mat composites. The weight ratio of clamshell fillers varied from 0% to 9%, and the compression moulding method was used to fabricate the composites. As per ASTM standards, mechanical properties were evaluated by conducting tensile and flexural tests. Free vibration tests by impact hammer technique were employed to evaluate the natural frequency, damping ratio, and mode shapes of developed composites to measure damping properties. Results revealed that adding clamshell filler significantly improved composites tensile strength, flexural strength, and damping properties. The addition of clamshell elevated the tensile strength by 18.5%, and flexural strength by 24.2% for composite with 6 wt% filler, which can be attributed to the efficiency of load transfer and the interfacial bonding between fillers and epoxy matrix. SEM analysis supported the experimental results obtained. The highest damping value is received for 9 wt% filler, showing 30% enhancement compared to composites without clamshell filler. Modal analyses using ANSYS software further validated the positive impact of clamshell filler. This study underscores the potential of clamshell filler in enhancing the mechanical and damping properties of epoxy-bamboo composites, broadening their applicability in various fields. © IMechE 2024.