No description available.

Call number: LD2668 .T4 1966 K78 / Master of Science

No description available.

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: Control; Flexible Plate; Piezoelectric; Robust Control; Switching Controller; Vibration. Includes bibliographical references (p. 44-47).

xii, 205 leaves : photos., diags., tables ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Mechanical Engineering, 1978

No description available.

Thesis (M. E.) (Civil) -- University of Western Sydney, 2002. / A thesis submitted for the degree of Master of Engineering (Civil), School of Engineering and Industrial Design, University of Western Sydney, 2002. Bibliography : p. 42-46.

The analysis of stiffened plate structures subject to complex loads such as air-blast pressure waves from external or internal explosions, water waves, collisions or simply large static loads is still considered a difficult task. The associated response is highly nonlinear and although it can be solved with currently available commercial finite element programs, the modelling requires many elements with a huge amount of input data and very expensive computer runs. Hence this type of analysis is impractical at the preliminary design stage. The present work is aimed at improving this situation by introducing a new philosophy. That is, a new formulation is developed which is capable of representing the overall response of the complete structure with reasonable accuracy but with a sacrifice in local detailed accuracy. The resulting modelling is relatively simple thereby requiring much reduced data input and run times. It now becomes feasible to carry out design oriented response analyses. Based on the above philosophy, new plate and stiffener beam finite elements are developed for the nonlinear static and dynamic analysis of stiffened plate structures. The elements are specially designed to contain all the basic modes of deformation response which occur in stiffened plates and are called super finite elements since only one plate element per bay or one beam element per span is needed to achieve engineering design level accuracy at minimum cost. Rectangular plate elements are used so that orthogonally stiffened plates can be modelled. The von Karman large deflection theory is used to model the nonlinear geometric behaviour. Material nonlinearities are modelled by von Mises yield criterion and associated flow rule using a bi-linear stress-strain law. The finite element equations are derived using the virtual work principle and the matrix quantities are evaluated by Gauss quadrature. Temporal integration is carried out using the Newmark-β method with Newton-Raphson iteration for the nonlinear equations at each time step. A computer code has been written to implement the theory and this has been applied to the static, vibration and transient analysis of unstiffened plates, beams and plates stiffened in one or two orthogonal directions. Good approximations have been obtained for both linear and nonlinear problems with only one element representations for each plate bay or beam span with significant savings in computing time and costs. The displacement and stress responses obtained from the present analysis compare well with experimental, analytical or other numerical results. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

In this work, several studies into the dynamic response of structures are made. In all the studies there is an interaction between the theoretical and experimental work that lead to important results. In the first study, previous theoretical results for the single-mode response of a parametrically excited cantilever beam are validated. Of special interest is that the often ignored nonlinear curvature is stronger than the nonlinear inertia for the first mode. Also, the addition of quadratic damping to the model improves the agreement between the theoretical and experimental results. In the second study, multi-mode responses of a slender cantilever beam are observed and characterized. Here, frequency spectra, pseudo-phase planes, Poincare sections, and dimension values are used to distinguish among periodic, quasi-periodic, and chaotic motions. Also, physical interpretations of the modal interactions are made. In the third study, a theoretical investigation into a previously unreported modal interaction between high-frequency and low-frequency modes that is observed in some experiments is conducted. This modal interaction involves the complete response of the first mode and modulations associated with the third and fourth modes of the beam. A model that captures this type of modal interaction is developed. In the fourth study, the natural frequencies and mode shapes of several composite plates are experimentally determined and compared with a linear finite-element analysis. The objective of the work is to provide accurate experimental natural frequencies of several composite plates that can be used to validate future theoretical developments. / Ph. D.

The nonlinear dynamical behavior of a laterally compressed, flat, composite panel subjected to a high supersonic flow is analyzed. The structural model considers a higher-order shear deformation theory which also includes the effect of the transverse normal stress and satisfies the traction-free condition on both faces of the panel. The possibility of small initial imperfections and in-plane edge restraints are also considered. Aerodynamic loads based on the third-order piston theory are used and the panel flutter equations are derived via Galerkin’s method. Periodic solutions and their bifurcations are obtained by using a predictor-corrector type of numerical integration method, i.e., the Shooting Method, in conjunction with the Arclength Continuation Method for the static solution. For the perfect panel, the amplitudes and frequency of flutter obtained by the Shooting Method are shown to compare well with results from the Method of Multiple Scales when linear aerodynamics is considered and compressive loads are absent. It is seen that the presence of aerodynamic nonlinearities could result in the hard flutter phenomenon, i.e., a violent transition from the undisturbed equilibrium state to that of finite motions which may occur for pre-critical speeds also. Results show that linear aerodynamics correctly predicts the immediate post-flutter behavior of thin panels only. When compressive edge loads or edge restraints are applied, in certain cases multiple periodic solutions are found to coexist with the stable static solution, or multiple buckled states are possible. Thus it is seen that the panel may remain buckled beyond the flutter boundary, or it may flutter within the region where buck-led states exist. Furthermore, the presence of edge restraints normal to the flow tends to stabilize the panel by decreasing the flutter amplitudes and the possibility of hard flutter. Nonperiodic motions (i.e., quasiperiodic and chaotic) of the buckled panel are found to exist, and their associated Lyapunov exponents are calculated. The effects of transverse shear flexibility, aerodynamic nonlinearities, initial imperfections, and in-plane edge restraints on the stability boundaries are also studied. It is observed that the classical plate theory over-predicts the instability loads, and only the shear deformation theory correctly models the panel which is flexible in transverse shear. When aerodynamic nonlinearities are considered, multiple flutter speeds may exist. / Ph. D.