Showing papers in "Journal of Engineering for Industry in 1974"

Vibration Control Using Semi-Active Force Generators

Abstract: A type of force generator which can respond to general feedback signals from a vibrating system in order to control the vibration but which does not require the power supply of a servomechanism is described. Computer simulation studies show that performance comparable to that of fully active vibration control systems can be achieved with the semi-active type of device. Physical embodiments of the concept are discussed and compared to hardware used in active and passive vibration control systems.

A Study of the Drilling Process

Abstract: Drilling is a complex three dimensional cutting process yet it is possible to simulate the action of a two flute twist drill with two dimensional models provided consideration is given to the influence of the feed velocity on the cutting geometry at the drill point. Two models of chip formation and an indentation model are developed to simulate the action of the drill point. From these models equations are derived for the prediction of total torque and thrust given the cutting conditions, drill geometry, and an empirical factor which is related to the work material. Computed values of torque and thrust are shown to compare favorably with those obtained from drilling tests on an 0.45 percent C steel. The shape and magnitude of the wear zone about the chisel edge is estimated and it is shown that the observed finite thrust force as the feed rate approaches zero can be attributed to the “cutting” action of the chisel edge.

The Laboratory Simulation of Vehicle Service Stress

Abstract: A simulation technique which will enable the response of vehicle components or complete vehicles to be reproduced in the laboratory is presented. For the case of a complete four wheeled vehicle it is shown how synthesized random displacements, based on a knowledge of the road surface undulations, can be derived; it is demonstrated that the information necessary to derive these four signals can be obtained from the spectral density evaluated from a single traverse along the road. Comparison is made between vehicle response measured on the test track, and the response on the simulator under synthesized random displacements and point-by-point profile excitation.

Sinusoidal response of composite-material plates with material damping.

Abstract: A general forced-vibration analysis is presented for laminated anisotropic rectangular plates including material damping. The theory used is the laminated version of the Mindlin plate theory and includes thickness-shear flexibility and rotatory and coupling inertia. A solution is obtained by the Rayleigh-Ritz method, extended to include the energy dissipated and the work done by the excitation. The analysis is applied to prediction of the resonant frequencies and associated nodal patterns and damping ratios of the first five modes for a series of rectangular plates with free edges. The plates considered consist of unidirectional boron-fiber/epoxy composite material with respective fiber orientations of 0, 10, 30, 45, 60, and 90 deg.

An Evaluation of Stresses and Deflection of Spur Gear Teeth Under Strain

Abstract: This paper aims at an evaluation of the stresses induced by a static load applied to gear teeth. For spur gears of different ratios with 20-deg pressure angle and standard addendum proportions, the stresses and deflections are computed by the finite element method. Formulas are drawn allowing a simple calculation of the maximum stresses, and the results are compared with what is given by ISO and AGMA standards related to the strength of gear teeth.

Transient Response of Rotor-Bearing Systems

Abstract: The equations of motion necessary to calculate the transient response of a multimass flexible rotor supported by nonlinear, damped bearings are derived from energy principles. Rotor excitation may be the result of imbalance, internal friction, rotor acceleration, nonlinear forces due to any number of bearing or seal stations, and gyroscopic couples developed from skewed disk effects. The method of solution for transient response simulation is discussed in detail and is based on extensive evaluation of numerical methods available for transient analysis. Examples of the application of transient response for the analysis of rotor bearing systems are presented and compared to actual machine performance. Recommendations for the use and extension of the present system simulation model are discussed.

Optimum Design of an Impact Absorber

Abstract: A shock absorber with nth order stiffness and mth order damping is designed for optimum response to a step change in base velocity (an acceleration impulse). The objective of the design is to minimize the maximum acceleration level occurring during the transient response. A single constraint is used to limit relative motion between the base and the isolated mass and another constraint is added to limit the oscillatory nature of the system response. Results of the study are presented on dimensionless curves showing the optimum stiffness and damping coefficients and the expected system performance as functions of m and n.