Showing papers by "Satish C. Sharma published in 2012"

Effect of carbon nanotube orientation on the mechanical properties of nanocomposites

Abstract: Carbon nanotubes (CNTs) have been regarded as ideal reinforcements of high-performance composites with enormous applications. In this paper, nano-structure is modeled as a linearly elastic composite medium, which consists of a homogeneous matrix having hexagonal representative volume elements (RVEs) and homogeneous cylindrical nanotubes with various inclination angles. Effects of inclined carbon nanotubes on mechanical properties are investigated for nano-composites using 3-D hexagonal representative volume element (RVE) with short and straight CNTs. The CNT is modeled as a continuum hollow cylindrical shape elastic material with different angles. The effect of the inclination of the CNT and its parameters is studied. Numerical equations are used to extract the effective material properties for the hexagonal RVE under axial as well as lateral loading conditions. The computational results indicated that elastic modulus of nano-composite is remarkably dependent on the orientation of the dispersed SWNTs. It is observed that the inclination significantly reduces the effective Young’s modulus of elasticity under an axial stretch. When compared with lateral loading case, effective reinforcement is found better in axial loading case. The effective moduli are very sensitive to the inclination and this sensitivity decreases with the increase of the waviness. In the case of short CNTs, increasing trend is observed up to a specific value of waviness index. It is also found from the simulation results that geometry of RVE does not have much significance on stiffness of nano-structures. The results obtained for straight CNTs are consistent with ERM results for hexagonal RVEs, which validate the proposed model results.

Vibration based performance prediction of ball bearings caused by localized defects

Abstract: This paper is focused on accurate performance prediction due to localized defects (like spalls) of microns level on the bearing components, which is essential to the design for high performance. In the mathematical formulation, the contacts between the rolling elements and the races are considered as nonlinear springs, whose stiffnesses are obtained by using Hertzian contact deformation theory. The formulation predicts the discrete spectra with the characteristic defect frequencies and their harmonics, which is helpful in prediction of system stability and to avoid severe (chaotic) vibrations in a rotor bearing system. The results are presented in the form of bifurcation diagrams, Fast Fourier Transformation (FFT) and Poincare maps for individual defects of bearing components. The system also shows the three different categories of system behavior under nonlinear dynamic conditions.

Vibration-based fault diagnosis of a rotor bearing system using artificial neural network and support vector machine

Abstract: This paper presents the vibration analysis of the healthy and cracked rotor supported on various faulty bearings. In rotating machines, one of the main causes of breakdown is faults in ball bearings. This study is mainly focused on fault diagnosis of rotor bearing system using artificial neural network (ANN) and support vector machine (SVM). The vibration response is obtained and analysed for the healthy and cracked rotor with the various defects of ball bearings. The specific defects considered on bearings are: crack in outer race, inner race with spall and corrosion pitting in balls. Statistical methods are used to extract features and to reduce the dimensionality of original vibration features. A comparative experimental study of the effectiveness of ANN and SVM is carried out. The results show that for this study, ANN is a better classifier than SVM.

Performance of a noncircular 2‐lobe multirecess hydrostatic journal bearing with wear

Abstract: Purpose – Noncircular journal bearings are used in industry because of their simplicity, efficiency and low cost. During the life time of a machine, these are required to be operated over a number of years and are submitted to several stops and starts. As a result, the bush becomes progressively worn out and the bearing performance changes. The purpose of this paper is to study theoretically the influence of wear on the performance of a non‐circular 2‐lobe four‐pocket multirecess hybrid journal bearing system.Design/methodology/approach – The Reynolds equation governing the flow of lubricant in the clearance space of a non‐circular 2‐lobe multirecess worn hybrid journal bearing system has been solved using FEM along with appropriate boundary conditions. The defects caused by wear are centered on the load line and range from 10 per cent to 50 per cent of the bearing radial clearance.Findings – The numerically simulated results based on a Newtonian lubricant and the steady state flow field system have been ...

Influence of Micropolar Lubrication on the Performance of 4-Pocket Capillary Compensated Conical Hybrid Journal Bearing

Abstract: The present paper deals with a theoretical analysis of 4-pocket capillary compensated conical hybrid journal bearing system operating with micropolar lubricant. The modified Reynolds equation for a conical journal bearing system operating with micropolar lubricant has been derived. In the present study, Eringen's micropolar theory has been used to model micropolar lubrication in cylindrical coordinate system. The study has been carried out for the different values of micropolar parameters, that is, characteristic length () and coupling number (). The conical bearing configurations having semicone angle 10∘, 20∘, 30∘, and 40∘ have been studied. The study suggests that micropolar lubricant offers better performance vis- a-vis Newtonian lubricant for bearing configurations having values of semicone angle 10∘and 20∘.

Chaotic response analysis of single-walled carbon nanotube due to surface deviations

Abstract: Nonlinear vibrational behavior of a single-walled carbon nanotube based mass sensors is considered The modeling involves stretching of the mid plane and damping The equation of motion involves two nonlinear terms due to the curved geometry and the stretching of the central plane due to the bridged boundary conditions The manifestation of instability and chaos in the dynamic response is observed The regions of periodic, sub-harmonic and chaotic behavior are clearly seen to be dependent on added mass and the surface deviations Poincare maps and frequency spectra are used to explicate and demonstrate the miscellany of the system behavior

A multiscale approach for estimating the chirality effects in carbon nanotube reinforced composites

Abstract: In this paper, the multiscale representative volume element approach is proposed for modeling the elastic behavior of carbon nanotubes reinforced composites. The representative volume element incorporates the continuum approach, while carbon nanotube characterizes the atomistic approach. Space frame structure similar to three dimensional beams and point masses are employed to simulate the discrete geometrical constitution of the single walled carbon nanotube. The covalent bonds between carbon atoms found in the hexagonal lattices are assigned elastic properties using beam elements. The point masses applied on each node are coinciding with the carbon atoms work as mass of beam elements. The matrix phase is modeled as a continuum medium using solid elements. These two regions are interconnected by interfacial zone using beam elements. Analysis of nanocomposites having single walled carbon nanotube with different chiralities is performed, using an atomistic finite element model based on a molecular structural mechanics approach. Using the proposed multi scale model, the deformations obtained from the simulations are used to predict the elastic and shear moduli of the nanocomposites. A significant enhancement in the stiffness of the nanocomposites is observed. The effects of interfacial shear strength, stiffness, tensile strength, chirality, length of carbon nanotube, material of matrix, types of representative volume elements and types of loading conditions on the mechanical behavior of the nanocomposites are estimated. The finite element results are compared with the rule of mixtures using formulae. It is found that the results offered by proposed model, are in close proximity with those obtained by the rule of mixtures.

3D Surface Roughness Effects on Transient Non-Newtonian Response of Dynamically Loaded Journal Bearings

Abstract: The influence of 3D surface roughness on the transient non-Newtonian response of a dynamically loaded journal bearing under mixed lubrication is studied. A study of the transient non-Newtonian response of a dynamically loaded journal bearing under mixed lubrication condition is performed including the effects of 3D surface roughness parameters such as roughness orientation and characteristics of surface roughness of opposing surfaces and the variation of fluid viscosity across and along the fluid-film thickness due to shear thinning and viscoelastic behavior of the lubricant. The Reynolds equation is modified to include the effects of surface roughness, viscosity variation across the fluid-film, and viscoelastic properties of the lubricant. The power law model and Maxwell's model are employed to characterize shear thinning and viscoelastic properties of the lubricant, respectively. The solution of the modified average Reynolds equation is obtained using a finite element method and appropriate iterative sc...

Performance Characteristics of Micropolar Lubricated Membrane-Compensated Worn Hybrid Journal Bearings

Abstract: The objective of the present article is to analytically study the effect of wear on the performance of a membrane-compensated hybrid journal bearing system under micropolar lubrication. The lubricating oil containing additives and contaminants has been modeled as a micropolar fluid. The wear on the bearing surface due to the transient (start–stop) operations has been modeled using Dufrane's abrasive wear model. The modified Reynolds equation governing the flow of micropolar lubricant in the clearance space of a bearing has been solved using an iterative scheme based on the finite element method (FEM) and the Newton-Raphson method. The numerically simulated results are presented for a wide range of restrictor design parameters, wear depth parameter, and micropolar parameters. The numerically simulated results suggest that the wear on the bearing surface and micropolar parameters of the lubricant significantly affect the bearing performance. Therefore, it is imperative to take into account the effect of wea...

Response surface modeling of vibrating omega tube (Copper) electromechanical Coriolis mass flow sensor

Abstract: Response Surface Methodology (RSM) is a combination of statistical and mathematical techniques to represent the relationship between the inputs and outputs of a physical system by explicit functions. This methodology has been widely employed in many applications such as design optimization, response prediction and model validation. But so far the literature related to its application in Coriolis mass flow sensing is scarce. Therefore the present work evaluates the effect of sensor location, excitation frequency on the performance of Coriolis Mass Flow Sensor (CMFS). The experiments were performed in a systematic manner with three successive trials using the indigenously developed setup of CMFS. Central composite design of RSM was adopted for analyzing the results. A second order, non-linear mathematical model has been developed for establishing the relationship among design parameters. Analysis of variance (ANOVA) has been performed to verify the fit and adequacy of the developed mathematical models.

Performance evaluation of a copper omega type Coriolis mass flow sensor with an aid of ANFIS tool

Abstract: The performance evaluation of a copper omega type Coriolis mass flow sensor using an adaptive neuro-fuzzy inference system (ANFIS) has been studied for influencing input design parameters. The exhaustive experimentation has been carried out under various operational conditions and further this data set is utilized for modeling using ANFIS. The results are in good agreement with the experimental results stating that this technique may be applied to predict the performance of mass flow sensor.

Effect of Punica granatum Linn. (Peel) on Blood Glucose Level in Normal and Alloxan-Induced Diabetic Rats

Abstract: The hydro alcoholic peel extract of Punica granatum Linn. var. arakta was investigated for its effect on blood glucose level in normal and alloxan induced diabetic rats. The effect was studied at two dose levels, 50 and 100 mg/kg body weight. The activity was compared with the standard drug glibenclamide (2 mg/kg, orally). The plant extract significantly lowered blood glucose level in both normal (P<0.05) and diabetic (P<0.01) rats.

Dynamic analysis of fixed-free single-walled carbon nanotube-based bio-sensors because of various viruses

Abstract: In the present study, the vibrations of the fixed-free single-walled carbon nanotube (SWCNT) with attached bacterium/virus on the tip have been investigated. To explore the suitability of the SWCNT as a bacterium/virus detector device, first the various types of virus have been taken for the study and then the resonant frequencies of fixed-free SWCNT with attachment of those viruses have been simulated. These resonant frequencies are compared with the published analytical data, and it is shown that the finite element method (FEM) simulation results are in good agreement with the analytical data. The results showed the sensitivity and suitability of the SWCNT having different length and different masses (attached at the tip SWCNT) to identify the bacterium or virus.

Influence of Couple Stress Lubricant on the Performance of Orifice Compensated Non-Recessed Hole-Entry Hydrostatic/Hybrid Journal Bearing

Abstract: The lubricants are generally additized in order to enhance their lubricating properties. As a consequence of this, they exhibit nonlinear relationship between the shear stress and shear strain. One class of lubricants which has received considerable attention in recent years is the couple stress lubricants. The study of couple stress fluid flows has been the subject of increased interest owing to its widespread industrial and scientific applications such as synthetic fluids, polymer-thickened oils, liquid crystals and animal bloods. The present work is therefore aimed to study analytically the influence of couple stress lubricant on the performance of an orifice compensated non-recessed hole-entry hydrostatic/hybrid journal bearings. The modified Reynolds equation based on Stoke’s couple stress fluid theory has been solved by using the Finite Element Method. The numerically simulated results have been presented for various valves of couple stress parameters and external loads. The numerically simulated results reveal that the influence of couple stress lubricant increases the value of minimum fluid film thickness at constant value of external load for hybrid journal bearing vis-a-vis Newtonian lubricant. Further, it has been observed that the value of direct fluid film damping coefficient (C22) is larger for hydrostatic journal bearing lubricated with couple stress lubricant.© 2012 ASME

Dry Sliding Wear Behavior of Hot Forged and Annealed Cu-Cr-SiС In Situ Composite

Abstract: In-situ composites offer a wide selection of constituent and an opportunity for understanding the mechanisms their mechanical properties so that intelligent decisions may be taken while tailoring a composite for a specific application. Properties of material are basically governed by the constituent phases and their distribution and depend on the composition and processing conditions. In the present investigation tribological properties of hot forged Cu-Cr-SiC and annealed after hot forging system are proposed to be studied by addition of Cr and SiC into the copper matrix. The effect of constituent phases on tribological properties after hot forged and annealed after hot forged has been investigated. It is expected to enhance the understanding of tribological properties in this presented work for the hot forged Cu-Cr-SiC composite system.

Fluid Flow and Inclusion Removal in Multi‐Strand Tundish with Nozzleblockage

Abstract: Association for Iron and Steel Technology;Process Technol. Modeling Comm. Extr. Process. Div.;Solidification Comm. Mater. Process. Manuf. Div.;Miner., Met. Mater. Soc. (TMS)