Monday  |  Salon 8  |  05:50 PM–06:10 PM

#16752–Direct FRF Expansion

Dynamic substructuring involves estimating the dynamics of a coupled system or assembly using the dynamics of the system’s individual, uncoupled components. In the substructuring process, dynamic information pertaining to each component’s connection points is required to accurately define the component’s connection stiffness. The dynamic information needed to define a component’s connection includes both translational and rotational degrees of freedom. A system model containing components with truncated rotational degrees of freedom will not be representative of the true physical system assembly. Analytically, the process of dynamic substructuring is generally straightforward as all the information pertaining to each component is assumed to be known. Experimentally, however, the rotational degrees of freedom required to define a component’s connection are traditionally difficult to measure due to limitations in transducer hardware. Existing methods of acquiring rotational degrees of freedom involve expanding translational mode shapes to rotational ones. Expanding a truncated set of translational mode shapes often leads to significant modal truncation error in the expanded rotary modes.

A method of directly expanding translational frequency response measurements to rotational ones was developed in this work to circumvent the process of expanding translational mode shapes. The proposed FRF expansion technique aims to provide an improved alternative for experimentally acquiring rotational degrees of freedom by eliminating the need for mode shape extraction. As rotational degrees of freedom traditionally have a heightened sensitivity to modal truncation, the proposed FRF expansion technique works to mitigate these errors. The proposed direct FRF expansion technique was validated using various analytical and experimental test cases.

John Seymour   University of Massachusetts at Lowell
Peter Avitabile   University of Massachusetts at Lowell
Ray Joshua   Honeywell