Modeling of complex systems using nonlinear, flexible multibody dynamics.

摘要

Finite element based multibody dynamics formulations extend the applicability of classical finite element methods to the modeling of flexible mechanisms. A general computer code will include rigid and flexible bodies, such as beams, joints, and active elements. These procedures are designed to overcome the modeling limitations of conventional multibody formulations that are often restricted to the analysis of rigid systems or use a modal representation to model the flexibility of elastic components.; As multibody formulations become more widely accepted, the need to model a wider array of phenomena increases. The goal of this work is to present a methodology for the analysis of complex systems that may require the modeling of new joints and elements, or include the effects of clearance, freeplay or friction in the joints.; Joints are essential components of multibody systems, rigid or flexible. Usually, joints are modeled as perfect components. In actual joints, clearance, freeplay, friction, lubrication and impact forces will can have a significant effect on the dynamic response of the system.; Certain systems require the formulation of new joints for their analysis. Among one of them is the curve sliding joint which enforces the sliding of a body on a rigid curve connected to another body. The curve sliding joint is especially useful when modeling a vibration absorber device mounted on the rotor hub of rotorcraft: the bifilar pendulum.; The formulation of a new modal based element is also presented. A modal based element is a model of an elastic substructure that includes a modal representation of elastic effects together with large rigid body motions. The proposed approach makes use of a component mode synthesis technique that allows the analyst to choose any type of modal basis and simplifies the connection to other multibody elements. The formulation is independent of the finite element analysis package used to compute the modes of the elastic component.