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Vel, Senthil S.

Works: 6 works in 6 publications in 1 language and 5 library holdings
Roles: Author
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Publications about Senthil S Vel
Publications by Senthil S Vel
Most widely held works by Senthil S Vel
Experimental Investigation into the Fatigue Life of Hybrid Joints Under Fully Reversed Flexure Loading ( file )
1 edition published in 2008 in English and held by 0 libraries worldwide
Glass Reinforced Polymers (GRP's) have a variety of properties that make them desirable for use in marine applications. For instance: high strength, low weight, corrosion resistance, inherent complex forming abilities, and low electromagnetic signature characteristics can be exceedingly advantageous in such areas. The U.S. Navy currently has an objective to investigate the use of lightweight materials to enhance naval capabilities, and GRP's have been of particular interest. Composite/metal hybrid systems offer a potential solution to many of the complications encountered in the construction of naval vessels, such as the weight of materials that are currently used and difficulty of forming them. Prevention of structural failures in a ship is essential if human injury, casualties and economic loss are to be avoided. Fatigue of connections is a major concern in an ocean environment. The overall objective of this research is to develop and demonstrate methods for fatigue testing various common and novel steel/composite hybrid connections and to evaluate their suitability for their desired applications. Fatigue of hybrid connections subject to out-of-plane loading is highly variable and there is a lack of data reported in the literature. The intention of this effort is to provide additional baseline data for this type of connection. Testing and analysis techniques were successfully developed and employed. It was determined that separate analyses of the individual components of a hybrid joint (e.g. the composite plate and the steel T-section) are insufficient to determine the effects of fatigue loading on a given joint due to the effects of joining methods on the strength. Fatigue testing of a full joint configuration is necessary to adequately evaluate its response to fatigue loading. Further testing beyond what is presented in this report is recommended
Effect of Temperature and Viscoelastic Creep on the Clamp-Up Load in Hybrid Composite/Metal Bolted Joints ( file )
1 edition published in 2009 in English and held by 0 libraries worldwide
Hybrid composite to metal bolted joints are the focus of much research due the inherent advantages that they present. In particular, they are very attractive to designers and engineers alike due to their simplicity and ease of disassembly. However, hybrid connections are particularly susceptible to metal fatigue, stress relaxation primarily due to viscoelastic creep of the composite, thermal effects due to coefficient of thermal expansion mismatch, galvanic corrosion between the dissimilar constituents of the joint and moisture absorption causing differential strain between the metal and composite. The study presented in this report focuses in an investigation of the effects of temperature and primary creep in hybrid metal to composite bolted connections. The study's relevance stems from the desire to apply this technology to naval applications, where watertight integrity must be maintained. It was then decided to examine this type of connection at the subcomponent level. Therefore, EGlass/vinyl ester plates!4" thick were bolted to aluminum and steel plates of the same thickness with instrumented steel bolts to determine the primary stress relaxation response. Special attention was placed on the effects of temperature change on the stress relaxation that hybrid connections are particularly susceptible from. A model was developed with the sole purpose of integrating the existing coefficient of thermal expansion mismatch between all the joint parts in the scheme of analysis. Experiments were carried out to obtain the CTE of the composite material used in the hybrid connection tests, and a computer program, GASmooth, was specifically written to correct the thermal effects on the stress relaxation data
Design Optimization and Fatigue Analysis of Laser Stake Welded Connections ( file )
1 edition published in 2008 in English and held by 0 libraries worldwide
This report summanzes research on the design and fatigue analysis of laser-stake welded connections performed at the University of Maine from January 2006 to December 2007 for the Structural Response of Hybrid Ship Connections Subjected to Fatigue Loads (HSCF) project. Laser welding is a maturing technology that can be used to fabricate metal/composite hybrid connections wherein modular composite panels with embedded steel inserts are welded to a steel ship hull. The static and fatigue response of continuous laser welded steel connections for ship structures has been analyzed using finite element techniques. The stress analyses, which are based on the principles of linear elastic fracture mechanics, will enable engineers to design robust laser welded lap joints for prescribed loads. It is found that the overlap length. weld width and plate thicknesses play a major role in determining joint strength under different loading conditions. The fatigue response of laser welded lap joints is also investigated for different weld geometries and loading conditions using a fracture specific finite element program FRANC2D. It is found that the weld width has a significant effect on the crack trajectory and fatigue life of the joint
Finite Element Analyses and Experimental Testing of Hybrid Composite/Metal Joints Subjected to Fully Reversed Flexure Fatigue Loading ( file )
1 edition published in 2009 in English and held by 0 libraries worldwide
The goal in this research is to accurately assess the fatigue life of hybrid composite/metal connections focusing upon bolted joints used in removable panels. Experimental testing was performed in flexure fatigue as part of this effort and is essential for fatigue life evaluation. In addition, analytical studies were performed using finite element analysis. Existing finite element modeling software offers a robust method for assessing the structural integrity of proposed hybrid connections. Ansys, a finite element modeling program, was used to study the response of two hybrid connection configurations subjected to fully-reversed flexure fatigue loading. A through-the-thickness stress investigation at critical locations in the connection was developed. Variables in the hybrid connection were altered in a parametric study and effects on flexibility and stress were observed. Through the use various models, a method for predicting the fatigue life in hybrid joints is proposed
Detection of Bolt Stress Relaxation in Hybrid Bolted Connections ( file )
1 edition published in 2003 in English and held by 0 libraries worldwide
The effort summarized in this report focuses upon real time detection of stress relaxation in bolted connections in hybrid structures. A proof-of-concept test bed for this effort consists of a 24-1/2 inch square plate made of Eglass/vinyl ester composite. Several interrogation techniques were employed and compared including: 1) low frequency modal analysis; 2) high frequency transfer functions and 3) high frequency transmittance functions. Each of these techniques employed a piezoelectric actuator bonded to the panel so to deliver a characterized disturbance in a controlled manner. The technique using transmittance functions to evaluate changes in bolt tensioning level shows the most promise
Analytical solutions for the deformation of anisotropic elastic and piezothermoelastic laminated plates by Senthil S Vel( file )
1 edition published in 1999 in English and held by 0 libraries worldwide
Author's abstract: The Eshelby-Stroh formalism is used to analyze the generalized plane strain quasistatic deformations of an anisotropic, linear elastic laminated plate. The formulation admits any set of boundary conditions on the edges and long faces of the laminate. Each lamina may be generally anisotropic with as many as 21 independent elastic constants. The three dimensional governing differential equations are satisfied at every point of the body. The boundary conditions and interface continuity conditions are satisfied in the sense of a Fourier series. Results are presented for three sample problems to illustrate the versatility of the method. The solution methodology is generalized to study the deformation of finite rectangular plates subjected to arbitrary boundary conditions. The effect of truncation of the series on the accuracy of the solution is carefully examined. Results are presented for thick plates with two opposite edges simply supported and the other two subjected to eight different boundary conditions. The results are compared with three different plate theories. The solution exhibits boundary layers at the edges except when they are simply supported. Results are presented in tabular form for different sets of edge boundary conditions to facilitate comparisons with predictions from various plate theories and finite element formulations. The Eshelby-Stroh formalism is also extended to study the generalized plane deformations of piezothermoelastic laminated plates. The method is capable of analyzing laminated plates with embedded piezothermoelastic patches. Results are presented for a thermoelastic problem and laminated elastic plates with piezothermoelastic lamina attached to its top surface. When a PZT actuator patch is attached to an elastic cantilever substrate, it is observed that the transverse shear stress and transverse normal stress are very large at the corners of the PZT-substrate interface
English (6)
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