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On the dynamics of tapered vibro-impacting cantilever with tip mass
P. S. Gandhi,Vishal Vyas 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.1
This paper explores nonlinear dynamic behavior of vibro-impacting tapered cantilever with tip mass with regard to frequency response analysis. A typical frequency response curve of vibro-impacting beams displays well-known resonance frequency shift along with a hysteric jump and drop phenomena. We did a comprehensive parametric analysis capturing the effects of taper, tip-mass, stop location, and gap on the non-smooth frequency response. Analysis is presented in a non-dimensional form useful for other similar cases. Simulation results are further validated with corresponding experimental results for a few cases. Illustrative comparison of simulation results for varying parameters brings out several interesting aspects of variation in the nonlinear behavior.
P.A. Joshi,V.G. Gandhi,M.K. Mishra,M.S. Rao,A. Kumar,D.O. Shah 한국공업화학회 2011 Journal of Industrial and Engineering Chemistry Vol.17 No.2
The comparative study on titanium dioxide (TiO2) catalyzed photocatalytic degradation (PCD) of aqueous aromatic carboxylic acids (phthalic acid, o-nitrobenzoic acid, o-chlorobenzoic acid and benzoic acid) was carried out in the presence of UV radiation using air. The TiO2 catalyst, synthesized by sol–gel technique and calcined at 673 K, resulted ca. 100% anatase phase with 23 nm crystallite size and surface area of 37 m2/g. This catalyst was found to be efficient for PCD of phthalic acid, o-nitrobenzoic acid, ochlorobenzoic acid and benzoic acid in aqueous medium. However, the reactivity and degradation pathway of these carboxylic acids were observed to be greatly influenced by the substituent group present in the aromatic ring. The order of degradation of aromatic carboxylic acids was found to be phthalic acid > o-nitrobenzoic acid > o-chlorobenzoic acid > benzoic acid. The aromatic carboxylic acids having electron withdrawing groups such as –COOH, –NO2 and –Cl were comparatively more reactive for PCD than unsubstituted aromatic acid i.e., benzoic acid. The degradation of ortho substituted benzoic acids (having electron withdrawing groups) follows different mechanistic pathway than that of benzoic acid. Study of various operational parameters like effect of catalyst loading, initial concentration of phthalic acid and kinetics of phthalic acid PCD was also carried out in batch type photocatalytic reactor.
Investigating the Evolution of the Dual AGN System ESO 509-IG066
Kosec, P.,Brightman, M.,Stern, D.,Mü,ller-Sá,nchez, F.,Koss, M.,Oh, K.,Assef, R. J.,Gandhi, P.,Harrison, F. A.,Jun, H.,Masini, A.,Ricci, C.,Walton, D. J.,Treister, E.,Comerford, J.,Privon, G American Astronomical Society 2017 The Astrophysical Journal Vol.850 No.2
Matsuta, K.,Gandhi, P.,Dotani, T.,Nakagawa, T.,Isobe, N.,Ueda, Y.,Ichikawa, K.,Terashima, Y.,Oyabu, S.,Yamamura, I.,Stawarz, L. The Korean Astronomical Society 2012 天文學論叢 Vol.27 No.4
We combine data from two all-sky surveys, the Swift/Burst Alert Telescope 22 Month Source Catalog and the AKARI Point Source Catalogue, in order to study the connection between the hard X-ray (> 10 keV) and infrared (IR) properties of local active galactic nuclei (AGN). We find two photometric diagnostics are useful for source classification: one is the X-ray luminosity vs. IR color diagram, in which type 1 radio-loud AGN are well isolated from other AGN. The second one uses the X-ray vs. IR color-color diagram as a redshift-independent indicator for identifying Compton-thick (CT) AGN. Importantly, CT AGN and starburst galaxies in composite systems can also be separated in this plane based upon their hard X-ray fluxes and dust temperatures. This diagram may be useful as a new indicator to classify objects in new surveys such as with WISE and NuSTAR.
A. Ramachandra Murthy,S. Vishnuvardhan,K.V. Anjusha,P. Gandhi,P.K. Singh 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.5
In the nuclear power plants, stainless steel is widely used for fabrication of various components such aspiping and pipe fittings. These piping components are subjected to cyclic loading due to start up and shutdown of the nuclear power plants. The application of cyclic loading may lead to initiation of crack atstress raiser locations such as nozzle to piping connection, crown of piping bends etc. of the pipingsystem. Crack initiation can also take place from the flaws which have gone unnoticed duringmanufacturing. Therefore, prediction of crack initiation life would help in decision making with respectto plant operational life. The primary objective of the present study is to compile various analyticalmodels to predict the crack initiation life of the pipes with notch. Here notch simulates the stress raisersin the piping system. As a part of the study, Coffin-Manson equations have been benchmarked to predictthe crack initiation life of pipe with notch. Analytical models proposed by Zheng et al. [1], Singh et al. [2],Yang Dong et al. [25], Masayuki et al. [33] and Liu et al. [3] were compiled to predict the crack initiationlife of SA312 Type 304LN stainless steel pipe with notch under fatigue loading. Tensile and low cyclefatigue properties were evaluated for the same lot of SA312 Type 304LN stainless steel as that of pipe test. The predicted crack initiation lives by different models were compared with the experimental results ofthree pipes under different frequencies and loading conditions. It was observed that the predicted crackinitiation life is in very good agreement with experimental results with maximum difference of ±10.0%.
Flexural behaviour of GFRP reinforced concrete beams under cyclic loading
A. Ramachandra Murthy,P. Gandhi,D.M. Pukazhendhi,F. Giftson Samuel,S. Vishnuvardhan 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.84 No.3
This paper examines the flexural performance of concrete beams reinforced with glass fibre-reinforced polymer (GFRP) bars under fatigue loading. Experiments were carried out on concrete beams of size 1500×200×100 mm reinforced with 10 mm and 13 mm diameter GFRP bars under fatigue loading. Experimental investigations revealed that fatigue loading affects both strength and serviceability properties of GFRP reinforced concrete. Experimental results indicated that (i) the concrete beams experienced increase in deflection with increase in number of cycles and failed suddenly due to snapping of rebars and (ii) the fatigue life of concrete beams drastically decreased with increase in stress level. Analytical model presented a procedure for predicting the deflection of concrete beams reinforced with GFRP bars under cyclic loading. Deflection of concrete beams was computed by considering the aspects such as stiffness degradation, force equilibrium equations and effective moment of inertia. Nonlinear finite element (FE) analysis was performed on concrete beams reinforced with GFRP bars. Appropriate constitutive relationships for concrete and GFRP bars were considered in the numerical modelling. Concrete non linearity has been accounted through concrete damage plasticity model available in ABAQUS. Deflection versus number of cycles obtained experimentally for various beams was compared with the analytical and numerical predictions. It was observed that the predicted values are comparable (less than 20% difference) with the corresponding experimental observations.
A. Ramachandra Murthy,S. Vishnuvardhan,M. Saravanan,P. Gandhi 국제구조공학회 2019 Structural Engineering and Mechanics, An Int'l Jou Vol.72 No.1
Structural integrity assessment of piping components is of paramount important for remaining life prediction, residual strength evaluation and for in-service inspection planning. For accurate prediction of these, a reliable fracture parameter is essential. One of the fracture parameters is stress intensity factor (SIF), which is generally preferred for high strength materials, can be evaluated by using linear elastic fracture mechanics principles. To employ available analytical and numerical procedures for fracture analysis of piping components, it takes considerable amount of time and effort. In view of this, an alternative approach to analytical and finite element analysis, a model based on relevance vector machine (RVM) is developed to predict SIF of part through crack of a piping component under fatigue loading. RVM is based on probabilistic approach and regression and it is established based on Bayesian formulation of a linear model with an appropriate prior that results in a sparse representation. Model for SIF prediction is developed by using MATLAB software wherein 70% of the data has been used for the development of RVM model and rest of the data is used for validation. The predicted SIF is found to be in good agreement with the corresponding analytical solution, and can be used for damage tolerant analysis of structural components.
Prediction of stress intensity factor range for API 5L grade X65 steel by using GPR and MPMR
A. Ramachandra Murthy,S. Vishnuvardhan,M. Saravanan,P. Gandhi 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.81 No.5
The infrastructures such as offshore, bridges, power plant, oil and gas piping and aircraft operate in a harsh environment during their service life. Structural integrity of engineering components used in these industries is paramount for the reliability and economics of operation. Two regression models based on the concept of Gaussian process regression (GPR) and Minimax probability machine regression (MPMR) were developed to predict stress intensity factor range (K). Both GPR and MPMR are in the frame work of probability distribution. Models were developed by using the fatigue crack growth data in MATLAB by appropriately modifying the tools. Fatigue crack growth experiments were carried out on Eccentrically-loaded Single Edge notch Tension (ESE(T)) specimens made of API 5L X65 Grade steel in inert and corrosive environments (2.0% and 3.5% NaCl). The experiments were carried out under constant amplitude cyclic loading with a stress ratio of 0.1 and 5.0 Hz frequency (inert environment), 0.5 Hz frequency (corrosive environment). Crack growth rate (da/dN) and stress intensity factor range (K) values were evaluated at incremental values of loading cycle and crack length. About 70 to 75% of the data has been used for training and the remaining for validation of the models. It is observed that the predicted SIF range is in good agreement with the corresponding experimental observations. Further, the performance of the models was assessed with several statistical parameters, namely, Root Mean Square Error (RMSE), Mean Absolute Error (MAE), Coefficient of Efficiency (E), Root Mean Square Error to Observation’s Standard Deviation Ratio (RSR), Normalized Mean Bias Error (NMBE), Performance Index (ρ) and Variance Account Factor (VAF).