Tutorial on experimental dynamic substructuring using the transmission simulator method

Abstract

Although analytical substructures have been used successfully for years, practical experimental substructures have been limited to special cases until recently. Many of the historical practical applications were based on a single point attachment. Since substructures have to be connected, theoretically, in both translation and rotation degrees of freedom, measurement translation responses and forces around the single point attachment could be used to estimate the rotational responses and moments. For multiple attachment points, often the rotations and moments have been neglected entirely. In addition, often the effect of the joint stiffness and damping is neglected. The translation simulator approach developed by Allen and Mayes captures the interface forces and motions through a fixture called the transmission simulator, overcoming the historical difficulties. The experimental free modes of the experimental substructure mounted to the transmission simulator and the finite element model of the transmission simulator are used to couple the experimental substructure to another substructure and subtract the transmission simulator. This captures the effects of the joint stiffness and damping. The experimental method and mathematics will be explained with examples. The tutorial assumes a basic understanding of the linear multi-degree of freedom equations of motion and the modal approximation. © The Society for Experimental Mechanics, Inc. 2012.