S.R. Kasiviswanathan’s research while affiliated with Michigan State University and other places

The flexure of a cuboid mixture of a nonlinearly elastic solid and an ideal fluid is considered in the context of the theory of interacting continua. The Helmholtz free energy function for the mixture is assumed to be of a Neo-Hookean type. The effect of flexure on the distribution of the fluid content and the radial stresses in the deformed, swollen, cylindrical configuration is investigated. Classical results for the flexure of a cuboid of an incompressible nonlinearly elastic material [1] are also derived by considering the special case of the mixture with zero fluid content. It is anticipated that the results presented herein will be valuable to practicing engineers, and also guide and motivate future experimental work.

In this work, the finite extension and torsion of a swollen elastic cylinder bonded to an inner rigid cylindrical core are investigated in the context of the theory of interacting continua. The boundary value problem is solved numerically in order to determine the variation of the stretch-ratios, the stresses and also the volume fraction of the solid. The results of these investigations not only demonstrate significant gradients in the stretch ratios and severe stress concentrations but also stress reversals under certain conditions. These stress reversals which occur in the neighborhood of the interface of the inner and outer cylinders can have a significant impact on damage studies pertaining to fiber/matrix debonding in fiber-reinforced composites, for example.

This experimental investigation is focused on characterizing a class of electro-rheological (ER) fluids and also characterizing a class of smart structures featuring this class of suspensions. These studies involved the imposition of different applied voltages on the ER fluid domain and various concentrations of the suspension particles. Electro-rheological fluids belong to a class of colloidal suspensions whose global characteristics can be controlled by the imposition of an appropriate external electric field upon the fluid domain. Therefore, when these fluids are embedded within a smart beam-like structure, the global properties of the beam, and hence its vibrational response, can also be controlled. In this work, the energy dissipation characteristics of smart cantilever beam specimens were measured. Different ER fluid smart beam specimens with various concentrations were employed in these investigations to provide insight on the relationship between the particle concentration of the suspension with damping ratio of the smart beam and the electric field intensity imposed on the beam. The coupled electrical and mechanical dynamic properties of smart materials featuring hydrous ER fluids were experimentally studied using a Rheometrics RMS 800 mechanical spectrometer to gain insight into their effectiveness in vibration control applications. THe experimental results demonstrate the non-Newtonian rheological behavior of ER fluids, and the ability of this class of smart beams to dissipate energy increases with the increase of particulate concentration and also the applied electric field.

This paper presents an exposition on the embryonic eclectic field of smart materials and structures, prior to discussing how different classes of these innovative biomimetic materials will influence design practices pertaining to diverse commercial and industrial products in the machine tool, medical, aerospace, automotive and sporting goods industries.

A collection of diverse experimental investigations is presented herein which demonstrates the active vibration-control capabilities of macroscopically smart fibrous composite structures featuring electro-rheological (ER) fluids, piezoelectric materials and fiber-optic sensing systems. This collage of investigations demonstrates the ability of beam- and plate-like structures fabricated in this class of smart laminated materials to tailor their elastodynamic characteristics in real-time. By judicious selection, the smart-materials designer can synthesize numerous classes of hybrid actuation systems from a variety of generic actuator systems in order to satisfy a broad range of performance specifications that cannot be satisfied by integrating only a single type of actuator system within this class of composite structures.

The steady MHD flow of a micropolar fluid between two infinite parallel, non-coaxially rotating disks, is studied. It is observed that a set of one-parameter family of exact solutions exists for the velocity and the micro-rotation components. The expressions for the components of the forces and couples acting on the plates are obtained. Numerical results explaining the effects of various parameters, associated with the flow, are discussed for some interesting special cases. We observe that the increase in Hartmann number distorts the velocity profile and decreases the boundary layer thickness. The magnitude of components of micro-rotation vector decreases for an increase in Hartmann number. So far a very few authors have shown interest in the study of MHD flow of a micropolar fluid. This paper appears to be the first to present an exact solution for the MHD flow of a micropolar fluid.

Several theoretical and experimental investigations have highlighted the vulnerability of polymeric fiber-reinforced composite materials to severe hygro-thermal environments. Traditionally, single constituent theories have been employed to model the constitutive response of idealized polymeric composite materials in hygro-thermal environments. Typically, these theories do not incorporate moisture as a distinct constituent in an explicit sense, and the moisture and temperature effects are treated as being uncoupled from the mechanical response of the composite material.The deficiencies of traditional techniques in modeling the hygro-thermo-elastic response of polymeric composites are addressed in this paper by treating the moisture-composite aggregate within the context of Mixture Theory. This approach not only permits the explicit incorporation of moisture and its effects, but it also allows the possibility of deriving constitutive equations to model the coupled hygro-thermo-elastic response of idealized fiber-reinforced composite materials undergoing small deformations. An illustrative example is presented in order to highlight the significant role of the fibers in modifying the hygro-thermo-elastic characteristics of the overall composite material. The authors believe that this is the first paper which rigorously treats the hygro-thermo-elastic behavior of polymeric composites in the context of Mixture Theory, and it is anticipated that this approach will have significant relevance in solving practical problems in defense, aerospace and manufacturing environments, where significant variations in moisture and temperature conditions are routinely encountered.

A collection of diverse experimental investigations are presented herein which demonstrate the active vibration control capabilities of macroscopically smart fibrous composite structures featuring electro-rheological (ER) fluids, piezoelectric materials, and fiber optic sensing systems. This collage of investigations demonstrates the ability of beam and plate-like structures fabricated in this class of smart laminated materials to tailor their elastodynamic characteristics in real-time. Furthermore, by judicious selection, the smart-materials designer can synthesize numerous classes of hybrid actuation systems from a variety of generic actuator systems in order to satisfy a broad range of performance specifications that cannot be satisfied by embedding only a single type of actuator systems within this class of composite structures.

The flow and heat transfer of an incompressible viscous fluid contained between two infinite parallel disks performing torsional oscillations of the same frequency but rotating with different angular velocities about two non-coincident parallel axes where the disks are maintained at different temperatures are investigated. The governing equations are nonlinear and the solution is obtained by a perturbation procedure with the parameter ε (≪1), the ratio of the angular velocity of the lower disk to the frequency of the torsional oscillations of the disks. Physically important quantities, namely the forces on the disks are calculated. The corresponding heat transfer problem is studied and the solution is presented for the temperature at zeroth order in ε. The heat flux is depicted graphically for various values of the ratio of the Eckert number and Prandtl number on the heat transfer.

The unsteady heat transfer associated with flow due to eccentrically rotating disks considered by Ramachandra Rao and Kasiviswanathan (1987) is studied via reformulation in terms of cylindrical polar coordinates. The corresponding exact solution of the energy equation is presented when the upper and lower disks are subjected to steady and unsteady temperatures. For an unsteady flow with nonzero mean, the energy equation can be solved by prescribing the temperature on the disk as a sum of steady and oscillatory parts.