Automated Dynamic Analysis of Chain-Driven Mechanical Systems

Abstract

A general approach to analyze the dynamics of chain-driven systems subjected to transient loads is developed and applied. The method suitable for many automated dynamic analysis techniques involves the simulation of the dynamic effect of chain by a displacement function and the introduction of this function as a kinematic constraint to couple with the system equations of motion. A general purpose dynamic analysis algorithm, the DADS code (Dynamic Analysis and Design Systems), is then employed to generate the set of system equations and to provide a computer-aided dynamic analysis of the overall chain-driven system. Two ways of formulating the chain displacement functions are described. One provides the displacement of the chain based on the pitch circles of chain sprockets; the other includes a consideration of the polygonal effect of the chain which contributes essentially to the dynamics of the chain. The latter involves the use of the principle of kinematic equivalency, i.e., modeling the chain dynamic effect by a four-bar linkage. Using the proposed displacement function, the kinematic motion of the chain can be taken into account. This procedure, therefore, makes the system adaptable to conventional dynamic analysis code in which the chain is usually not included as one of the standard elements. Moreover, pulsation and dynamic load of the chain as well as the system dynamic response due to chain effect may be estimated. A typical large-scale chain-driven system which is an externally powered machine gun is investigated to illustrate the potential usefulness of the approach.