C. K. Sung

A survey of finite element techniques for mechanism design

Abstract During the creation of a modern machine system, the designer must generally develop a mathematical model to investigate the levels of vibrational activity, dynamic stresses, bearing loads and often the acoustic radiation associated with the system. Since all of these phenomena may be represented by field theories whose governing equations of motion may be stated as either differential, integral or integro-differential equations, they are all amenable to solution by the single most powerful computational tool available to the analyst: the finite element method. Mechanism design methodologies based on this versatile technique are reviewed herein, their different characteristics are highlighted and future trends indicated.

Material selection: An important parameter in the design of high-speed linkages

Abstract Numerous studies in the literature have demonstrated that members of high-speed linkages should be designed with high strength-to-weight ratios and high stiffness-to-weight ratios. By satisfying these criteria, the designer is able to minimize the troublesome elastodynamic phenomena associated with demonstrates the advantages of using ultra high strength fiber-reinforced composites in this design field by simulating the dynamic responses of flexible four bar linkages manufactured in three different materials (steel, aluminum and a graphite-epoxy laminate). The mechanisms are analyzed using a displacement finite element model and the equations of motion are solved by numerical integration.

An experimental study to demonstrate the superior response characteristics of mechanisms constructed with composite laminates

Abstract A detailed experimental investigation is presented into the dynamic flexural responses of slider-crank and four-bar linkages constructed from steel, aluminum and two graphite-epoxy laminates. This is the first time that an experimental investigation has demonstrated that composite linked mechanisms have superior response characteristics to comparable mechanisms manufactured in the commercial metals, and also that this dynamic behavior is governed by the stiffness-to-density ratio of the link material.

The design of robots and intelligent manipulators using modern composite materials

Abstract The operating speed and endpoint positional accuracy of existing industrial manipulators are limited by the inertial and stiffness characteristics of the articulating members of the robots mechanical linkage. This limitation may be overcome by developing members having high structural stiffness and strength with low mass, and this has been recognized for some time. These characteristics can be obtained by fabricating the moving members of manipulators in fiber reinforced composite materials. In order to establish a basis for the dynamic analysis of robots fabricated in viscoelastic composites, a variational theorem is developed herein. A preliminary comparative study is then undertaken for manipulators manufactured in a graphite-epoxy composite material and also steel in order to demonstrate some of the advantages to be accrued from this proposed new design philosophy.

AN EXPERIMENTAL-STUDY ON THE NONLINEAR ELASTODYNAMIC RESPONSE OF LINKAGE MECHANISMS

Abstract A detailed experimental investigation is presented into the elastodynamic response of four-bar linkages and slider-crank mechanisms. Linkages with different kinematic configurations, and link cross-sectional dimensions are operated over a wide range of crank frequencies, and the experimental responses, which are stored and post-processed using a modern digital data-aquisition system, are then compared with computer simulation results from finite element analyses of these flexible mechanisms. These computer codes are based on a variational theorem which incorporates elastic geometrical nonlinearities, and the equations of motion are solved by utilizing a step-by-step numerical integration algorithm.

A methodology for synthesizing high-performance robots fabricated with optimally tailored composite laminates

Methode de conception de robots hautement performants en materiaux composites stratifies de structure specialement optimisee

An analytical and experimental investigation of high-speed mechanisms fabricated with composite laminates

The articulating members of linkage machinery must be designed and manufactured with high stiffness-to-weight ratios in order that these machine systems operate successfully in a high-speed mode. One approach to satisfying this criterion is to exploit the high specific stiffnesses of polymeric fibrous composite laminates. In this paper, results of mechanical tests of candidate materials are presented and the material constitutive behaviour classified. A variational theorem is then derived by using the Stieltjes convolution notation which enables the equations governing the geometrically-non-linear dynamic response of linkages fabricated in linear viscoelastic composite materials to be systematically established. The formulation includes inertial terms which couple the kinematic deformations of the link material with the kinematics governing the gross motion of the linkage being analyzed. This variational principle provides the basis for a finite element formulation in which the properties of the heterogeneous, two-constituent laminates are represented by a continuum model for a homogeneous single-constituent material. The predictive capability of this model is evaluated by simulating the vibrational response of both experimental four-bar linkages and also slider-crank mechanisms fabricated with simple link geometries, prior to comparing the computer results with experimental data from these laboratory mechanisms.