Dragan Marinković

Aspects of Modeling Piezoelectric Active Thin-walled Structures

The objective of this article is to reconsider some important aspects of modeling piezoelectric active thin-walled structures. Hence, it is dealt here with thin-walled laminated structures involving piezoelectric patches. A recently developed shell type finite element is used for the purpose. The first aspect is adequate modeling of electric field within the piezoelectric patches polarized in the thickness direction. The influence of higher order functions for the electric field on the accuracy of the model is discussed. The second aspect is related to modeling geometrical non-linearities in the behavior of the considered structures and their significance on the accuracy of the predicted behavior. Both aspects are considered with respect to static and dynamic cases.

Dynamical modelling of hydraulic excavator considered as a multibody system

Original scientific paper This paper considers the development of a plane multibody mechanical model of a hydraulic excavator simultaneously containing an open kinematic chain and closed loops. The Lagrange multiplier technique is used for modelling of the constrained mechanical systems. This approach is used for working out the dynamic equations of excavator motion in the case of performing transportation and digging operations. The excavator is considered as a rigid body system and detailed governing equations of the mechanical and hydraulic systems are presented. The performed verification and a typical digging task simulation show the applicability of the model for study of the excavator motion simulation. Simulation results of the machine’s response are provided. It is shown that the digging process considerably influences the mechanical and hydraulic system parameters. Such models can be used for training simulators, sizing components and system design.