Division of Mechanics

Unilateral Contact of Vibrating Beams

Researcher: Lars Johansson

In this project, conducted in cooperation with ABB Atom AB, the motion of a beam excited by prescribed forces is considered. The beam is constrained by unilateral contact against springs at contact sites along the beam. The gaps at the contact sites are allowed to change due to wear. Since there might be an initial gap at a contact site, or a gap might develop due to wear, and since the springs might have a nonlinear force-displacement relation, the problem considered is strongly nonlinear.

This is a type of problem that occurs in power applications, for example when the tubes in a heat exchanger is excited by flowing water and the tubes are rubbed against the baffles, or when the fuel rods in a nuclear reactor are rubbed against the spacer grids, also because of water flow excitation. Obviously it is important to keep the wear to a minimum in nuclear equipment due to the risk of increased radioactive contamination of surrounding equipment.

Recently an effort has been made to include the effects of random excitation in the model.

This project was terminated during 1998. It has resulted in the following publications:

Johansson, L., Beam Motion with Unilateral Contact Constraints and Wear of Contact Sites, J. Pressure Vessel Technology, 119, 105-110, 1997.

Knudsen J., Massih, A.R. & Johansson, L., Calculation of Vibro-Impact Dynamics of Loosely Supported Rods, Proceedings, ASME International Congress and Exposition, Dallas, Texas, 16-21 Nov. 1997.

Johansson, L., Motion of Beams with Unilateral Contact Constraints and Wear, Proceedings of the First International Symposium on Impact and Friction of Solids, Structures and Intelligent Machines, edited by A. Guran, World Scientific, 2000.

Further, one additional paper has been submitted for publication.

This page is maintained by: Lars Johansson, and was last changed: 28 November 2000