Ravi Raveendra - Academia.edu (original) (raw)

Papers by Ravi Raveendra

Research paper thumbnail of Coupled Weld-Rupture Analysis of Automotive Assemblies: A Study to Demonstrate the Impact of Welding Processes on the Performance of Weldments

SAE Technical Paper Series

Research paper thumbnail of Calibration of International Space Station (ISS) Node 1 Vibro-Acoustic Model

Reported here is the ability of utilizing the Energy Finite Element Method (E-FEM) to predict the... more Reported here is the ability of utilizing the Energy Finite Element Method (E-FEM) to predict the vibro-acoustic sound fields within the International Space Station (ISS) Node 1 and to compare the results with actual measurements of leak sounds made by a one atmosphere to vacuum leak through a small hole in the pressure wall of the Node 1 STA module during its period of storage at Stennis Space Center (SSC). While the E-FEM method represents a reverberant sound field calculation, of importance to this application is the requirement to also handle the direct field effect of the sound generation. It was also important to be able to compute the sound fields in the ultrasonic frequency range. This report demonstrates the capability of this technology as applied to this type of application.

Research paper thumbnail of Boundary Element Method for High Frequency Acoustic Analysis

Noise Control and Acoustics, 1997

A boundary element formulation based on energy flow is developed for the analysis of high frequen... more A boundary element formulation based on energy flow is developed for the analysis of high frequency acoustic problems. Unlike traditionally modelled acoustic pressure and velocity variables, the variation of space-averaged energy density at high frequencies is rather smooth and therefore energy parameters are well suited for the description of acoustic behavior. The governing differential and integral equations based on energy variables are similar to the Helmholtz equations for acoustic problems based on pressure and velocity variables and thus the extension of existing solution techniques for the solution of integral equations based on energy flow parameters is rather straightforward.

Research paper thumbnail of An Experimental Investigation of

of failure mode interaction in laminated composites subjected to compressive loading

Research paper thumbnail of Calibration of International Space Station (ISS) Node 1 Vibro-Acoustic Model-Report 2

Reported here is the ability of utilizing the Energy Finite Element Method (E-FEM) to predict the... more Reported here is the ability of utilizing the Energy Finite Element Method (E-FEM) to predict the vibro-acoustic sound fields within the International Space Station (ISS) Node 1 and to compare the results with actual measurements of leak sounds made by a one atmosphere to vacuum leak through a small hole in the pressure wall of the Node 1 STA module during its period of storage at Stennis Space Center (SSC). While the E-FEM method represents a reverberant sound field calculation, of importance to this application is the requirement to also handle the direct field effect of the sound generation. It was also important to be able to compute the sound fields in the ultrasonic frequency range. This report demonstrates the capability of this technology as applied to this type of application.

Research paper thumbnail of Computation of Sound Transmission Loss and Absorption Coefficient of Multi-Layer Systems

Noise Control and Acoustics, 2001

Sound transmission and absorption of multi-layer sound absorbents are discussed in this manuscrip... more Sound transmission and absorption of multi-layer sound absorbents are discussed in this manuscript. A new matrix formulation based on four pole parameters is utilized to derive the transmission loss and absorption coefficient of the absorbents. A transfer matrix relating pressure to acoustic velocity provides the required information to calculate the transmission loss and absorption coefficient. The multi-layer sound absorbents considered are structural panels, elastic porous linings and air-gaps. No limitations are imposed on the number of layers. Some realistic configurations of a multi-layer sound absorbent are studied to demonstrate the applicability of the four-pole parameter technique.

Research paper thumbnail of Identification of Incoherent Noise Sources

Noise Control and Acoustics, 2001

A Nearfield Acoustical Holography (NAH) technique that is applicable to the identification of mul... more A Nearfield Acoustical Holography (NAH) technique that is applicable to the identification of multiple, incoherent noise sources from measured sound pressure fields are described. Initially, a partial coherence approach is adopted to decouple an incoherent acoustic field into a set of fully coherent, mutually incoherent partial fields. Subsequently, NAH is applied individually to each coherent partial field to reconstruct the corresponding source field. A boundary element based NAH reconstruction procedure is utilized so that the technique is valid for arbitrary source geometry. The process is validated by identifying the sources in a two-speaker system that was driven by independent signal generators.

Research paper thumbnail of Determination of Vehicle Interior Noise due to Electric Motor

SAE Technical Paper Series, 2019

Research paper thumbnail of Material Characterization of Multi-Layered Noise Control Treatments from Random-Incidence Transmission Loss

SAE Technical Paper Series, 2019

Research paper thumbnail of A Novel Approach for High Frequency Interior Noise Prediction

SAE Technical Paper Series, 2018

Research paper thumbnail of Advanced Modeling for Fatigue Growth of Small Surface Cracks

The primary result of the sponsored research is the development and application of the boundary e... more The primary result of the sponsored research is the development and application of the boundary element method for two- and three-dimensional fatigue crack growth analysis. The two-dimensional formulation developed previously (AFOSR Contract No. F49620-84-C-0042) was extended to investigate the crack tip behavior of long and short cracks under cyclic loading. The influence of residual plasticity on stress intensity factor was used to obtain an unambiguous estimate of the plastic zone size. It was demonstrated that the effect of the plastic wake on the stress intensity factor for crack opening (closure) and the effect of the residual stress on the retardation are identical manifestations of the same plasticity process. The boundary integral equations also provide insight to the mathematical equivalence of these two effects. Keywords: Fracture mechanics, Fatigue crack growth, Crack retardation, Crack closure, Crack opening displacement, Boundary element method.

Research paper thumbnail of An Integrated Experimental/Numerical Noise Source Identification Technique, #273

Proceedings of SPIE - The International Society for Optical Engineering

Research paper thumbnail of Progressive Failure Analysis Method of a Pi Joint with Uncertainties in Fracture Properties

53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference<BR>20th AIAA/ASME/AHS Adaptive Structures Conference<BR>14th AIAA, 2012

In this presentation, the structural performance of fiber reinforced composite laminate Pi joints... more In this presentation, the structural performance of fiber reinforced composite laminate Pi joints is studied through a progressive failure analysis (PFA) method. The bonded joint area that is the weakest link of the Pi joint structure is modeled using the discrete cohesive zone method (DCZM). The damage growth and failure of the bonded interface is modeled through an exponential decaying traction-separation law that governs the behavior of DCZM elements. This interface model is implemented into a non-linear finite element (FE) code for modeling the progressive failure of the composite Pi joint structures. The present PFA framework is incorporated with a probabilistic analysis module to consider material variability and manufacturing inconsistencies. The proposed PFA methodology is demonstrated for a 2D Pi-shaped laminate composite structure adhesively bonded through a Pi joint, and subjected to a pull-off load.

Research paper thumbnail of Computational modeling of failure in composite structures including uncertainties in material and geometrical properties

52nd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference, 2011

This paper is concerned with a progressive failure analysis methodology for fiber reinforced comp... more This paper is concerned with a progressive failure analysis methodology for fiber reinforced composite laminates combining various analytical models designed for investigating failure mechanisms at different length scales. The methodology here employs a fundamental mechanism based approach to predict failure or damage initiation with strong coupling between the multiple length scales. The discrete cohesive zone model elements are used to model the adhesion and delamination failure at macroscale while Schapery theory, a continuum damage theory based on thermodynamics, is used to model material degradation occurring at the lamina level. Furthermore, the present numerical framework is incorporated with a probabilistic analysis module, based on the NEESUS software, to consider material variability and manufacturing inconsistencies. The combined analysis modules are implemented in a non-linear finite element code for modeling the progressive failure of advanced composite structures. The proposed progressive failure analysis methodology is applied to several cases for validating its capability of predicting the evolution of the interactive failure mechanisms in composite structures.

Research paper thumbnail of The Interaction of Failure Modes in the Compression Response and Failure of Laminated Composites

53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference<BR>20th AIAA/ASME/AHS Adaptive Structures Conference<BR>14th AIAA, 2012

Failure mode interactions when a laminated fiber reinforced composite is subjected to compression... more Failure mode interactions when a laminated fiber reinforced composite is subjected to compression is studied here. Delamination, fiber kink-banding and their interaction are seen to dominate the failure response. An upscaled semi-homogenized laminate model is developed to predict the observed compression response of multi-directional laminates. A reduced 2-D formulation is presented first to determine the interfaces most susceptible to delamination. Subsequently, cohesive elements are added along these interfaces to introduce delamination capability in the model. Predictions of the model are compared against experimental data, and are found to be in agreement with respect to compressive strength and failure modes.

Research paper thumbnail of BIE Solutions for Applied Thermoplasticity by Collocation

Discretization Methods in Structural Mechanics, 1990

The design application of BIE methods to the stress analysis of advanced turbomachinery component... more The design application of BIE methods to the stress analysis of advanced turbomachinery components involves four domain integral problems: transient thermal strains, temperature dependent material properties, steep thermal gradients due to thermal shock, and plastic strains caused by thermal shock. Application of the BIE method to such problems has been significantly hindered by the need to provide domain elements to model each of these effects. The goal of the current study is to include each of these effects through the use of collocation methods, using particular solutions corresponding to properly selected global interpolation functions.

Research paper thumbnail of An Indirect Boundary Element Technique for Exterior Periodic Acoustic Analysis

SAE Technical Paper Series, 1997

Research paper thumbnail of Interior Noise Prediction Based on Energy Finite Element Method

SAE Technical Paper Series, 2005

Research paper thumbnail of Sound Power Sensitivity Analysis and Design Optimization Using BEM

SAE Technical Paper Series, 2003

A general numerical formulation based on the Boundary Element Method (BEM) for computing radiated... more A general numerical formulation based on the Boundary Element Method (BEM) for computing radiated sound power sensitivity is presented in this paper. The total radiated sound power is computed using surface acoustic pressure and velocity information. Explicit analytical differentiation of the sound power with respect to acoustic normal velocities is performed on the boundary integral equations to obtain sound power sensitivity information. The formulation is applicable to structures with arbitrary geometries, free edges, openings, and multiple connections. Acoustic absorption materials applied on the structure surface can also be modeled as impedance boundary conditions. The developed formulation is validated and its application is demonstrated.

Research paper thumbnail of Improving the Acoustical Performance of Poroelastic Materials

SAE Technical Paper Series, 2005

Research paper thumbnail of Coupled Weld-Rupture Analysis of Automotive Assemblies: A Study to Demonstrate the Impact of Welding Processes on the Performance of Weldments

SAE Technical Paper Series

Research paper thumbnail of Calibration of International Space Station (ISS) Node 1 Vibro-Acoustic Model

Reported here is the ability of utilizing the Energy Finite Element Method (E-FEM) to predict the... more Reported here is the ability of utilizing the Energy Finite Element Method (E-FEM) to predict the vibro-acoustic sound fields within the International Space Station (ISS) Node 1 and to compare the results with actual measurements of leak sounds made by a one atmosphere to vacuum leak through a small hole in the pressure wall of the Node 1 STA module during its period of storage at Stennis Space Center (SSC). While the E-FEM method represents a reverberant sound field calculation, of importance to this application is the requirement to also handle the direct field effect of the sound generation. It was also important to be able to compute the sound fields in the ultrasonic frequency range. This report demonstrates the capability of this technology as applied to this type of application.

Research paper thumbnail of Boundary Element Method for High Frequency Acoustic Analysis

Noise Control and Acoustics, 1997

A boundary element formulation based on energy flow is developed for the analysis of high frequen... more A boundary element formulation based on energy flow is developed for the analysis of high frequency acoustic problems. Unlike traditionally modelled acoustic pressure and velocity variables, the variation of space-averaged energy density at high frequencies is rather smooth and therefore energy parameters are well suited for the description of acoustic behavior. The governing differential and integral equations based on energy variables are similar to the Helmholtz equations for acoustic problems based on pressure and velocity variables and thus the extension of existing solution techniques for the solution of integral equations based on energy flow parameters is rather straightforward.

Research paper thumbnail of An Experimental Investigation of

of failure mode interaction in laminated composites subjected to compressive loading

Research paper thumbnail of Calibration of International Space Station (ISS) Node 1 Vibro-Acoustic Model-Report 2

Reported here is the ability of utilizing the Energy Finite Element Method (E-FEM) to predict the... more Reported here is the ability of utilizing the Energy Finite Element Method (E-FEM) to predict the vibro-acoustic sound fields within the International Space Station (ISS) Node 1 and to compare the results with actual measurements of leak sounds made by a one atmosphere to vacuum leak through a small hole in the pressure wall of the Node 1 STA module during its period of storage at Stennis Space Center (SSC). While the E-FEM method represents a reverberant sound field calculation, of importance to this application is the requirement to also handle the direct field effect of the sound generation. It was also important to be able to compute the sound fields in the ultrasonic frequency range. This report demonstrates the capability of this technology as applied to this type of application.

Research paper thumbnail of Computation of Sound Transmission Loss and Absorption Coefficient of Multi-Layer Systems

Noise Control and Acoustics, 2001

Sound transmission and absorption of multi-layer sound absorbents are discussed in this manuscrip... more Sound transmission and absorption of multi-layer sound absorbents are discussed in this manuscript. A new matrix formulation based on four pole parameters is utilized to derive the transmission loss and absorption coefficient of the absorbents. A transfer matrix relating pressure to acoustic velocity provides the required information to calculate the transmission loss and absorption coefficient. The multi-layer sound absorbents considered are structural panels, elastic porous linings and air-gaps. No limitations are imposed on the number of layers. Some realistic configurations of a multi-layer sound absorbent are studied to demonstrate the applicability of the four-pole parameter technique.

Research paper thumbnail of Identification of Incoherent Noise Sources

Noise Control and Acoustics, 2001

A Nearfield Acoustical Holography (NAH) technique that is applicable to the identification of mul... more A Nearfield Acoustical Holography (NAH) technique that is applicable to the identification of multiple, incoherent noise sources from measured sound pressure fields are described. Initially, a partial coherence approach is adopted to decouple an incoherent acoustic field into a set of fully coherent, mutually incoherent partial fields. Subsequently, NAH is applied individually to each coherent partial field to reconstruct the corresponding source field. A boundary element based NAH reconstruction procedure is utilized so that the technique is valid for arbitrary source geometry. The process is validated by identifying the sources in a two-speaker system that was driven by independent signal generators.

Research paper thumbnail of Determination of Vehicle Interior Noise due to Electric Motor

SAE Technical Paper Series, 2019

Research paper thumbnail of Material Characterization of Multi-Layered Noise Control Treatments from Random-Incidence Transmission Loss

SAE Technical Paper Series, 2019

Research paper thumbnail of A Novel Approach for High Frequency Interior Noise Prediction

SAE Technical Paper Series, 2018

Research paper thumbnail of Advanced Modeling for Fatigue Growth of Small Surface Cracks

The primary result of the sponsored research is the development and application of the boundary e... more The primary result of the sponsored research is the development and application of the boundary element method for two- and three-dimensional fatigue crack growth analysis. The two-dimensional formulation developed previously (AFOSR Contract No. F49620-84-C-0042) was extended to investigate the crack tip behavior of long and short cracks under cyclic loading. The influence of residual plasticity on stress intensity factor was used to obtain an unambiguous estimate of the plastic zone size. It was demonstrated that the effect of the plastic wake on the stress intensity factor for crack opening (closure) and the effect of the residual stress on the retardation are identical manifestations of the same plasticity process. The boundary integral equations also provide insight to the mathematical equivalence of these two effects. Keywords: Fracture mechanics, Fatigue crack growth, Crack retardation, Crack closure, Crack opening displacement, Boundary element method.

Research paper thumbnail of An Integrated Experimental/Numerical Noise Source Identification Technique, #273

Proceedings of SPIE - The International Society for Optical Engineering

Research paper thumbnail of Progressive Failure Analysis Method of a Pi Joint with Uncertainties in Fracture Properties

53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference<BR>20th AIAA/ASME/AHS Adaptive Structures Conference<BR>14th AIAA, 2012

In this presentation, the structural performance of fiber reinforced composite laminate Pi joints... more In this presentation, the structural performance of fiber reinforced composite laminate Pi joints is studied through a progressive failure analysis (PFA) method. The bonded joint area that is the weakest link of the Pi joint structure is modeled using the discrete cohesive zone method (DCZM). The damage growth and failure of the bonded interface is modeled through an exponential decaying traction-separation law that governs the behavior of DCZM elements. This interface model is implemented into a non-linear finite element (FE) code for modeling the progressive failure of the composite Pi joint structures. The present PFA framework is incorporated with a probabilistic analysis module to consider material variability and manufacturing inconsistencies. The proposed PFA methodology is demonstrated for a 2D Pi-shaped laminate composite structure adhesively bonded through a Pi joint, and subjected to a pull-off load.

Research paper thumbnail of Computational modeling of failure in composite structures including uncertainties in material and geometrical properties

52nd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference, 2011

This paper is concerned with a progressive failure analysis methodology for fiber reinforced comp... more This paper is concerned with a progressive failure analysis methodology for fiber reinforced composite laminates combining various analytical models designed for investigating failure mechanisms at different length scales. The methodology here employs a fundamental mechanism based approach to predict failure or damage initiation with strong coupling between the multiple length scales. The discrete cohesive zone model elements are used to model the adhesion and delamination failure at macroscale while Schapery theory, a continuum damage theory based on thermodynamics, is used to model material degradation occurring at the lamina level. Furthermore, the present numerical framework is incorporated with a probabilistic analysis module, based on the NEESUS software, to consider material variability and manufacturing inconsistencies. The combined analysis modules are implemented in a non-linear finite element code for modeling the progressive failure of advanced composite structures. The proposed progressive failure analysis methodology is applied to several cases for validating its capability of predicting the evolution of the interactive failure mechanisms in composite structures.

Research paper thumbnail of The Interaction of Failure Modes in the Compression Response and Failure of Laminated Composites

53rd AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference<BR>20th AIAA/ASME/AHS Adaptive Structures Conference<BR>14th AIAA, 2012

Failure mode interactions when a laminated fiber reinforced composite is subjected to compression... more Failure mode interactions when a laminated fiber reinforced composite is subjected to compression is studied here. Delamination, fiber kink-banding and their interaction are seen to dominate the failure response. An upscaled semi-homogenized laminate model is developed to predict the observed compression response of multi-directional laminates. A reduced 2-D formulation is presented first to determine the interfaces most susceptible to delamination. Subsequently, cohesive elements are added along these interfaces to introduce delamination capability in the model. Predictions of the model are compared against experimental data, and are found to be in agreement with respect to compressive strength and failure modes.

Research paper thumbnail of BIE Solutions for Applied Thermoplasticity by Collocation

Discretization Methods in Structural Mechanics, 1990

The design application of BIE methods to the stress analysis of advanced turbomachinery component... more The design application of BIE methods to the stress analysis of advanced turbomachinery components involves four domain integral problems: transient thermal strains, temperature dependent material properties, steep thermal gradients due to thermal shock, and plastic strains caused by thermal shock. Application of the BIE method to such problems has been significantly hindered by the need to provide domain elements to model each of these effects. The goal of the current study is to include each of these effects through the use of collocation methods, using particular solutions corresponding to properly selected global interpolation functions.

Research paper thumbnail of An Indirect Boundary Element Technique for Exterior Periodic Acoustic Analysis

SAE Technical Paper Series, 1997

Research paper thumbnail of Interior Noise Prediction Based on Energy Finite Element Method

SAE Technical Paper Series, 2005

Research paper thumbnail of Sound Power Sensitivity Analysis and Design Optimization Using BEM

SAE Technical Paper Series, 2003

A general numerical formulation based on the Boundary Element Method (BEM) for computing radiated... more A general numerical formulation based on the Boundary Element Method (BEM) for computing radiated sound power sensitivity is presented in this paper. The total radiated sound power is computed using surface acoustic pressure and velocity information. Explicit analytical differentiation of the sound power with respect to acoustic normal velocities is performed on the boundary integral equations to obtain sound power sensitivity information. The formulation is applicable to structures with arbitrary geometries, free edges, openings, and multiple connections. Acoustic absorption materials applied on the structure surface can also be modeled as impedance boundary conditions. The developed formulation is validated and its application is demonstrated.

Research paper thumbnail of Improving the Acoustical Performance of Poroelastic Materials

SAE Technical Paper Series, 2005