S. J. Lee

Bio: S. J. Lee is an academic researcher from Texas A&M University. The author has contributed to research in topics: Finite element method & Smart material. The author has an hindex of 2, co-authored 2 publications receiving 96 citations.

Vibration suppression of laminated shell structures investigated using higher order shear deformation theory

Abstract: Third-order shear deformation theories of laminated composite shells are developed using the strain–displacement relations of Donnell and Sanders theories. These theories also account for geometric nonlinearity in the von Karman sense. Analytical (Navier) solutions for vibration suppression in cross-ply laminated composite shells with surface mounted smart material layers are developed using the linear versions of the two shell theories and for simply supported boundary conditions. Numerical results are presented to bring out the parametric effects of shell types (cylindrical, spherical, and doubly curved shells) and material properties on vibration suppression. A simple negative velocity feedback control in a closed loop is used.

Transient responses of magnetostrictive plates by using the GDQ method

Abstract: We used the generalized differential quadrature (GDQ) method to compute the transient response of thermal stresses and center displacement in laminated magnetostrictive plates under thermal vibration. We obtained the GDQ solutions in a three-layer (0° m /90°/0) and a 10-layer (0° m /90°/0°/90°/0) s laminated magnetostrictive plate with four simply supported edges. We presented the transient responses of thermal stress and center displacement with and without velocity feedback control, respectively. The advantage of the GDQ method used provide us with an efficient method to compute the results including shear deformation effect with a few grid points. These GDQ results had its potential that could be used and considered as basic data in the future magnetostrictive laminate studies.

Coupled analysis of composite laminate with embedded magnetostrictive patches

Abstract: A new finite element formulation for composite laminates containing embedded magnetostrictive patches is studied using anhysteretic, coupled, linear properties of magnetostrictive materials, which will act both as sensors and actuators. Constitutive relationships of magnetostrictive materials are represented through two equations, one for actuation and the other for sensing, both of which are coupled through a magneto-mechanical coefficient. The coupled model is studied without assuming any explicit direct relationship with the magnetic field. This is unlike the uncoupled model, where the magnetic field is assumed to be proportional to the actuation current and coil turns per unit length. Hence, both mechanical and magnetic (smart) degrees of freedoms are required to take care of the total mechanical and magnetic energy in the system. In this model, the elastic modulus, the permeability and magneto-elastic constant are assumed not to vary with the magnetic field. Actuation and sensing coils are considered to activate patches and sense the changes in stress in patches. When the actuator patch is excited dynamically by passing an alternating current through the actuation coil, it introduces stress in the structure due to the magneto-mechanical coupling effect, which in turn produces magnetic flux in the sensing patches. This magnetic flux generates open circuit voltage in the sensing coils. A number of numerical experiments are performed to show the essential difference between coupled and uncoupled analyses. For this, static, frequency response and time history analyses are performed in 1D structures. It is found that the ply sequence has a phenomenal effect on the overall response due to coupling.