Showing papers in "Archive: Journal of Mechanical Engineering Science 1959-1982 (vols 1-23) in 1992"
TL;DR: Based on the analogy between structural mechanics and optimal control theory, the eigensolutions of a symplectic matrix, the adjoint symplectic ortho-normalization relation and the eigenvector expansion method are introduced into the wave propagation theory for sub-structural chain-type structures, such as space structures, composite material and turbine blades.
Abstract: Based on the analogy between structural mechanics and optimal control theory, the eigensolutions of a symplectic matrix, the adjoint symplectic ortho-normalization relation and the eigenvector expansion method are introduced into the wave propagation theory for sub-structural chain-type structures, such as space structures, composite material and turbine blades. The positive and reverse algebraic Riccati equations are derived, for which the solution matrices are closely related to the power flow along the sub-structural chain. The power flow orthogonality relation for various eigenvectors is proved, and the energy conservation result is also proved for wave scattering problems.
44 citations
TL;DR: In this article, the authors investigated the vibration signature of roller bearings, induced by the surface irregularities of components, under various lubricating conditions, and found that the vibration spectra of a normal bearing may have a pattern of equal frequency spacing distribution (EFSD) whose frequency information is similar to that of a damaged bearing.
Abstract: This study investigates the vibration signature of roller bearings, induced by the surface irregularities of components, under various lubricating conditions. The bearing vibration is modelled as the output of the bearing assembly which is subjected to the excitations of surface irregularities through the oil-film. The oil-film acts as a spring between the roller and race. The stiffness of oil-film under different lubricating conditions is studied from the empirical equation of minimum oil-film thickness. It is shown that the vibration spectra of a normal roller bearing may have a pattern of equal frequency spacing distribution (EFSD) whose frequency information is similar to that of a damaged bearing. Under large loading and low running speed, the vibration energy is low if the lubricant viscosity is high. On the other hand, at high running speed, the vibration energy is high with high lubricant viscosity.
16 citations
TL;DR: The form-closure robotic grasping of a rigid object and how fine motion of the grasped object may be induced are discussed and a best approximation can be found.
Abstract: This paper discusses the form-closure robotic grasping of a rigid object and shows how fine motion of the grasped object may be induced. Preloads are applied along point contacts, a knowledge of whose elastic properties are necessary to overcome statical indeterminacy in the grasp, and whose properties can be exploited to allow the induced fine motion. Appropriate values of these preloads can be derived so as to maintain the grasp against external loads and to induce predefined fine motion to the object. Where a defined fine motion cannot be exactly induced, a best approximation can be found. The analytical approach is supported with examples.
6 citations
TL;DR: In this article, the problem of vibration in bladed disc assemblies is discussed in terms of catastrophe theory and the "curve veering" phenomenon, where unstable vibration amplitudes could occur as a result of coupling and mistumng.
Abstract: The problem of vibration in bladed disc assemblies is discussed in terms of catastrophe theory and the ‘curve veering’ phenomenon. A region in the bifurcation diagram of a bladed disc where unstable vibration amplitudes could occur as a result of coupling and mistumng is identified.
6 citations
TL;DR: In this article, a vibration and damping analysis of multi-layered conical shells incorporating layers of viscoelastic materials in addition to elastic ones, the former causing dissipation of vibratory energy, is the subject matter of this paper.
Abstract: The vibration and damping analysis of multi-layered conical shells incorporating layers of viscoelastic materials in addition to elastic ones, the former causing dissipation of vibratory energy, is the subject matter of this paper. The analysis given herein uses Hamilton's variational principle for deriving equations of motion of a general multi-layered conical shell. In view of the correspondence principle of linear viscoelasticity which is valid for harmonic vibrations, the solution is obtained by replacing the moduli of viscoelastic layers by complex moduli. An approximate solution for axisymmetric vibrations of multi-layered conical shells with two end conditions—simply supported edges and clamped edges—is obtained by utilizing the Galerkin procedure. The damping effectiveness in terms of the system loss factor for all families of modes of vibrations for three-, five- and seven-layered shells is evaluated and its variation with geometrical parameters is investigated.
5 citations
TL;DR: The Stirling cycle machine is modelled in the Eulerian reference frame as discussed by the authors, and the energy equation by itself is a transparent statement of the physical phenomena involved, and is simple symbolically.
Abstract: The gas processes in the Stirling cycle machine are usually modelled in the Eulerian reference frame. In Lagrange coordinates the energy equation by itself is a transparent statement of the physical phenomena involved, and is simple symbolically. It is virtually a ‘one-line’ description of the gas processes at all locations and at all points in the cycle.
3 citations
TL;DR: In this paper, a three-dimensional simulation of the modified two-temperature horizontal Bridgman growth of gallium arsenide crystals has been developed, where the computer model solves time-dependent, Navier-Stokes equations with a Boussineq approximation by the finite difference method.
Abstract: A three-dimensional simulation of the modified two-temperature horizontal Bridgman growth of gallium arsenide crystals has been developed. The computer model solves time-dependent, Navier-Stokes equations with a Boussineq approximation by the finite difference method. A new model of nodal latent heat is adopted for melting and freezing processes. The interface of solid-liquid phases as well as flow and temperature fields of both phases are obtained. The simulation finds that the furnace pulling rate and the heat-loss prevention arrangement has an impact on the shape of the interface. The computed solidification fronts agree with the experimental data successfully. The radiation heat loss in the process plays a major role in the heat-transfer mechanism, which has been taken into consideration to obtain the correct trend for the simulation.
2 citations
TL;DR: In this article, a theoretical comparison between fully active and semi-active vibration control applied to a simple vibrating system is presented, focusing on the physical limitations of such active vibration control systems and highlighting the important physical parameters.
Abstract: A theoretical comparison between fully active and semi-active vibration control applied to a simple vibrating system is presented. With the advent of modern transducers and signal processing equipment, control of vibration by active rather than passive means is a practical possibility. There are many ways of implementing such control systems, and this paper discusses and compares a fully active and a semi-active system used to reduce the transmissibility of a single-degree-of-freedom system. The paper concentrates on the physical limitations of such active vibration control systems and highlights and discusses the important physical parameters.
1 citations