Showing papers by "S. P. Harsha published in 2013"

Fault diagnosis of rolling element bearing with intrinsic mode function of acoustic emission data using APF-KNN

Abstract: This paper presents a fault diagnosis technique based on acoustic emission (AE) analysis with the Hilbert-Huang Transform (HHT) and data mining tool HHT analyzes the AE signal using intrinsic mode functions (IMFs), which are extracted using the process of Empirical Mode Decomposition (EMD) Instead of time domain approach with Hilbert transform, FFT of IMFs from HHT process are utilized to represent the time frequency domain approach for efficient signal response from rolling element bearing Further, extracted statistical and acoustic features are used to select proper data mining based fault classifier with or without filter K-nearest neighbor algorithm is observed to be more efficient classifier with default setting parameters in WEKA APF-KNN approach, which is based on asymmetric proximity function with optimize feature selection shows better classification accuracy is used Experimental evaluation for time frequency approach is presented for five bearing conditions such as healthy bearing, bearing with outer race, inner race, ball and combined defect The experimental results show that the proposed method can increase reliability for the faults diagnosis of ball bearing

Vibrational characteristics of defective single walled BN nanotube based nanomechanical mass sensors: single atom vacancies and divacancies

Abstract: In the present work, vibrational characteristics of a single walled BN nanotube (SWBNNT) is explored considering point defects (single atom vacancies and di-vacancies) to use SWBNNTs as nanomechanical mass sensors. Resonant frequency based analysis of SWBNNT with different types of point defect is performed using an atomistic finite element model based on molecular structural mechanics. The cantilevered configuration of zigzag (14,0) form of SWBNNT with different point defects is modeled considering it as a space frame structure with three dimensional elements and point masses, such that the proximity of the model to the actual atomic structure of nanotube is significantly retained. The finite element simulation approach is used to analyze the effect of point defects like single atom vacancies (VB – boron vacancy and VN – nitrogen vacancy) and divacancies (VBN). The present approach is validated by comparing the obtained simulation results for resonant frequency variation against attached mass at the tip of the cantilevered SWBNNTs, with continuum mechanics based analytical results for defect-free SWBNNT and are found in good agreement. An increase in resonant frequencies observed, when the point defects (VB, VN and VBN) move from fixed-end to the free end of the cantilevered configuration of the SWBNNTs. Also, the resonant frequency shift due to different point defects is analyzed against the attached mass at the free end, for the different positions of the point defect along the length of the nanotube and results indicate that the mass sensitivity limit of 10 −25 kg can be obtained. Using present atomistic finite element model based simulation approach, different atomic structures, different types of point defect as well as boundary conditions can be simulated effectually. The present atomistic finite element model based resonant frequency analysis of defective SWBNNTs is useful to develop the algorithm for the detection of the added mass, identification of the type of point defect and its position along the length of the nanotube.

An efficient finite element model for analysis of single walled boron nitride nanotube-based resonant nanomechanical sensors

Abstract: In this paper, the dynamics analysis of single walled boron nitride nanotubes (SWBNNT) as a resonant nanomechanical sensor by using the finite element method has been reported. Molecular structural mechanics-based finite element model (FEM) has been developed by using three-dimensional elastic beams and point masses, such that the proximity of the model to the actual atomic structure of nanotube is significantly retained. Different types of armchair layups of SWBNNTs are considered with cantilevered and bridged end constraints. By implementing the finite element simulation approach, the resonant frequency shift-based mass sensitivity analysis is performed for both types of end constraints for considered armchair form of the SWBNNTs with different aspect ratios. For both types of end constraint, continuum mechanics-based analytical formulations, considering effective wall thickness of nanotubes are used to validate the present FEM-based simulation approach. The intermediate landing position of the added ma...

Vibration signature analysis of a high speed rotor supported on ball bearings due to localized defects

Abstract: This paper presents the vibration signature analysis of the high speed rolling element bearings due to localized defects with an un-cracked and a cracked rotor. In rotating machines, one of the main causes of breakdown is faults in ball bearings and crack in rotors. Thus, accurate prediction of severe vibration conditions and characteristic defect frequencies is crucial for the reliable operation. A test rig of a high speed rotor supported on healthy and defective ball bearings is used. The vibration response is obtained and analyzed for the un-cracked and cracked rotor with and without defects on bearing components. The defects such as spalls on the outer race, inner race and on the rolling elements are considered for the study. Combined parametric effects have been analyzed to predict the dynamic response of a rotor-bearing system using response surface method. It is also observed that the severe vibrations occur under bearings with spall on the inner race surface and on a ball under high speed rotor co...

The 'forgotten disease' (or the never known).

Abstract: Lemierre's syndrome is an acute oropharyngeal infection with secondary septic thrombophlebitis of the internal jugular vein and frequent metastatic infections. Despite its rarity, it is important to have a high degree of clinical suspicion to recognise it early. A history of sore throat followed by metastatic infections and abscesses should alert the clinician to the possibility of this unusual infection. We present a case of Lemierre's syndrome presenting with meningitis in a previously healthy young adult along with a review of the pathophysiology of necrobacillosis and its diagnosis, diagnostic difficulty and treatment.

Study of subjective responses on ride comfort in public transport Uttarakhand State buses

Abstract: Today, ride comfort has developed facets that are as significant as safety and speed in assessing the physical characteristics of transportation. The road roughness and vehicle vibration play a predominant role in the subjective evaluation of the ride comfort and activity comfort. The quality of life on board road vehicles is influenced by the level of ride comfort which is basically related to vibration levels and the perception of fatigue. The present study encompasses a questionnaire based study conducted on public transport buses in India, in different routes between Roorkee to Hardwar, Hardwar to Roorkee, and Saharanpur to Roorkee together with vibration measurements on the seat and floor with vertical (z) and lateral (y) directions. The subjective study involved reading of a national Hindi newspaper, to obtain a subjective opinion and to quantify the difficulty in reading and also from the vibration measurements the seat accelerations were measured for suggesting the proper design of seats in public transportation buses. The Preference technique method was adopted and the level of discomfort analyzed in 7- point Semantic scale. The conclusions from the seat location, postures adapted for reading and the vibration measurements served as useful guidelines for conducting experimental work in the Laboratory.

Single Walled Boron Nitride Nanotube Reinforced Composite Based Nanomechanical Resonator

Abstract: Boron nitride nanotubes (BNNTs) possess extremely high stiffness and strength and may provide the ultimate reinforcing materials for the development of nanocomposites. In this paper, the Young’s modulus of BNNT based composites are evaluated using a 3-D nanoscale representative volume element based on continuum mechanics (CM) and using the finite element method (FEM). Additionally, the suitability of the BNNTs reinforced polymeric composites as nanomechanical resonators, using CM based approach and FEM is illustrated in this paper. Analytical formulas based on CM are used to examine the mass sensitivity of single walled BNNT (SWBNNT) reinforced composite considered as a thin wall BNNT for different aspect ratios and volume fractions of BNNT in composites. The FEM analysis, considering SWBNNT as a transversely anisotropic material is performed and results are compared with the CM based approach. The results indicated that the mass sensitivity of SWBNNT reinforced composite based nanomechanical resonators can reach 10−3 fg and a logarithmically linear relationship exists between the resonant frequency and the attached mass, when mass is larger than 10−3 fg. The simulation results which have been obtained based on FEM are found to be in good agreement with the analytical approach used in this paper.

Analysis Of Seated Human Body Under Low Frequency Vibrations Using Transmissibility And Driving Point Mechanical Impedance.

Abstract: Humans are more sensitive to whole Body Vibration under low frequency range. Under this frequency range human feels more discomfort. Due to this reason more research is going on from more number of years in low frequency range.As a part of research biodynamic models are prepared to number of degrees of freedom and these results are compared with the experimental data.In the present study the authors prepared a 5 DOF biodynamic model of the human body in a sitting posture without backrest under sinusoidal excitation to determine the.dynamic response characteristics such as Driving point mechanical impedance (DPMI)which describes the “to-the–body “forcemotion relationship at the seat to human interference and Transmissibility function describes the “through–the-body “ vibration transmission properties. As a part of this study analytical transmissibility data is validated with the experimental data. The resonant frequencies of the human subjects computed on the basis of Transmissibility function are found to be within close to that of the expected for the human body.

Response Surface Method based Railway Wheel Optimisation for Natural Frequency

Abstract: In this paper, response surface method is used to find out the fatigue life equation by taking load and dimensions of the wheel as variables. The natural frequency is taken as a factor for fatigue life. An ANOVA analysis is carried out to formulate the natural frequency function. An objective function has been formulated to minimise the mass of railway wheel considering the strength and geometrical constraints of inner hub-hole, hub-web interface and hub-rim interface.