Linear and Nonlinear Aspects of Self-Excited Vibrations in Circulatory Systems
Prof. Dr. Peter Hagedorn, TU Darmstadt
Date: Friday, November 01, 2013
Place: EA 409
Self-excited vibrations in mechanical engineering systems are in general unwanted and sometimes dangerous. There are many systems exhibiting self-excited vibrations which up to this day cannot be completely avoided, such as brake squeal, the galloping vibrations of overhead transmission lines, the ground resonance in helicopters and others. These systems have in common that in the linearized equations of motion the self-excitation terms are given by non-conservative, circulatory forces. It has been well known for some time, that such systems are very sensitive to damping.
Recently, several new theorems concerning the effect of damping on the stability and on the self-excited vibrations were proved by some of the authors. This presentation discusses these new mathematical results for practical mechanical engineering systems. It turns out that the structure of the damping matrix is of utmost importance, and the common assumption, namely representing the damping matrix as a linear combination of the mass and the damping matrices, may give completely misleading results for the problem of instability and the onset of self-excited vibrations. The presentation will be about some new linear and also about nonlinear aspects of these problems.
About the Speaker:
Peter Hagedorn was born in 1941 in Berlin, Germany. He grew up in Brazil, where he graduated (Engineer’s degree) in mechanical engineering in 1964 at EPUSP and in 1966 earned his doctoral degree at the same University. He then worked as a research assistant and later as ‘dozent’ (similar to lecturer) at the University of Karlsruhe, Germany. In 1971 he got his ‘habilitation’ (similar to Dr. Sc.) at Karlsruhe. From 1973 to 1974 he was a visiting Research Fellow at the Department of Aeronautics and Astronautics, Stanford University. Since October 1974 he is full professor of mechanics at the Technische Universität Darmstadt and head of the Dynamics and Vibrations group. He also has served as visiting professor at Rio de Janeiro (Brazil), Berkeley, Paris, Irbid (Jordan) and Christchurch (New Zealand), where he also holds an Adjunct Professorship at UCC. He has served as Head of Department and Vice-President to his home University in Darmstadt and he is serving in a number of professional and editorial committees. He is author of over 250 papers and nine books on a variety of topics in the general field of dynamics and vibrations and analytical mechanics. He is currently head of the Dynamics and Vibrations Group at the Chair of Numerical Methods in Mech. Engineering (fnb, Professor Schäfer) at TU Darmstadt, Associated to the Graduate School of Computational Engineering.