Mohan Rao - Academia.edu (original) (raw)

Papers by Mohan Rao

SOUND AND VIBRATION/JUNE 2004 This article presents a case study on the radiation, transmission a... more SOUND AND VIBRATION/JUNE 2004 This article presents a case study on the radiation, transmission and reduction of noise from a table saw typically used in the construction industry. The National Institute of Occupational Safety and Health (NIOSH) initiated this project through a multi-university student project program. In the construction industry, little attention has been given to control of noise from equipment and power tools. In order to address these issues, the work presented here is focused on reducing noise radiation from a table saw used in the construction industry from an engineering control point of view. The testing methodologies and results presented in this article address both the airborne and structure-borne noise contributors of the table saw. Sound power and sound intensity measurements were used to identify and rank all possible noise sources from the table saw. The use of these testing techniques in conjunction with experimental modal analysis, operational defl...

2014 ASEE Annual Conference & Exposition Proceedings

Journal of Vibration and Acoustics

A mathematical model to study the longitudinal vibration of an adhesively bonded double-strap joi... more A mathematical model to study the longitudinal vibration of an adhesively bonded double-strap joint is presented in this paper. Energy method and Hamilton’s principle are used to derive the governing equations of motion and natural boundary conditions of the joint system. The adhesive is modeled as a viscoelastic material using complex modulus approach. Both the shear and longitudinal deformation in the adhesive layer are included in the analysis. The equations to predict the system resonance frequencies and loss factors are derived from the system natural and forced boundary conditions for the case of simply supported boundary conditions. A special searching strategy for finding the zeros of a complex determinant has been utilized to obtain the numerical results. The effects of the adhesive shear modulus and structural parameters such as lap ratio, adhesive and strap thickness on the system resonance frequencies and loss factors are also studied.

SAE Technical Paper Series

SAE Technical Paper Series, 2003

Damping measurements on vehicle subsystems are rarely straightforward due to the complexity of th... more Damping measurements on vehicle subsystems are rarely straightforward due to the complexity of the dynamic interaction of system joints, trim, and geometry. Various experimental techniques can be used for damping estimation, such as frequency domain modal analysis curve-fitting methods, time domain decay-rate methods, and other methods based on energy and wave propagation. Each method has its own set of advantages and drawbacks. This paper describes an analytical and an experimental comparison between two, widely used loss factor estimation techniques frequently used in Statistical Energy Analysis (SEA). The single subsystem Power Injection Method (PIM) and the Impulse Response Decay Method (IRDM) were compared using analytical models of a variety of simulated simple spring-mass-damper systems. Frequency averaged loss factor values were estimated from both methods for comparison. The parameters of the analytical models were varied to study the effects of the total number of modes, amount of damping, location of modes within frequency bands, and the width of the frequency bands on loss factor estimation. The analytical study showed that both methods give accurate loss factor values as long as one modal resonance is present in each frequency band and as long as the damping values remain realistic for linear systems. These analytical results were confirmed experimentally by measuring the loss factors of simple steel plates, with and without damping treatments applied.

S V Sound and Vibration, 2001

This article presents the damping effectiveness of free-layer damping materials through standard ... more This article presents the damping effectiveness of free-layer damping materials through standard Oberst bar testing, solid plate excitation (RTC3) testing and prediction through numerical schemes. The main objective is to compare damping results from various industry test methods to performance in an automotive body structure. Existing literature on laboratory and vehicle testing of free-layer viscoelastic damping materials has received significant attention in recent history. This has created considerable confusion regarding the appropriateness of different test methods to measure material properties for damping materials/treatments used in vehicles. The ability to use the material properties calculated in these tests in vehicle CAE models has not been extensively examined. Existing literature regarding theory and testing for different industry standard damping measurement techniques is discussed. This discussion is followed by the comparison of damping treatments through laboratory testing.

International Journal of Solids and Structures, 1993

ABSTRACT In this paper, a theoretical analysis to evaluate the stress field in the adhesive layer... more ABSTRACT In this paper, a theoretical analysis to evaluate the stress field in the adhesive layers of tubular bonded joints subjected to torsional loading is presented. The formulation is suitable to study the static behavior of the joint under general loading conditions as well as steady-state behavior under cyclic loading conditions. The adhesive material is modeled using linear viscoelasticity and numerical results for the shear stresses in the adhesives, joint compliance and joint loss factor are presented for various cases that provide some insights and guidelines in the design of the joint.

Recent Developments in Air and Structure Borne Sound and Vibration, 1992

ABSTRACT

SAE Technical Paper Series, 2009

Journal of Vibration and Acoustics, 1996

In this paper, the results of analytical investigation into the effects of cocuring fiber composi... more In this paper, the results of analytical investigation into the effects of cocuring fiber composite tubes with commercially available damping materials are presented. A comprehensive theory has been developed for studying the vibration of a composite tube with multiple viscoelastic damping layers. The effects of transverse shear deformation, transverse normal stress and strain, rotary inertia, and higher-order stiffness terms are included in the modeling along with shear correction factors. Resonance frequency and loss factor results as a function of various geometric and physical parameters are presented for composite tubes with single and double damping layers. It is demonstrated through a parametric study that in all these systems, careful selection of damping and pre-preg material is needed to optimize the damping benefits desirable and the stiffness reductions that can be tolerated.

ISRN Mechanical Engineering, 2013

This paper presents a modeling technique to study the vibroacoustics of multiple-layered viscoela... more This paper presents a modeling technique to study the vibroacoustics of multiple-layered viscoelastic laminated beams using the Biot damping model. In this work, a complete simulation procedure for studying the structural acoustics of the system using a hybrid numerical model is presented. The boundary element method (BEM) was used to model the acoustical cavity, whereas the finite element method (FEM) was the basis for vibration analysis of the multiple-layered beam structure. Through the proposed procedure, the analysis can easily be extended to another complex geometry with arbitrary boundary conditions. The nonlinear behavior of viscoelastic damping materials was represented by the Biot damping model taking into account the effects of frequency, temperature, and different damping materials for individual layers. The curve-fitting procedure used to obtain the Biot constants for different damping materials for each temperature is explained. The results from structural vibration an...