Another Look at Sine-Dwell Mode Testing

Abstract

A simple and systematic method is described for the measurement of natural modes of vibration through the application of single frequency sinusoidal forces using a minimum number of shakers. It is an explicit procedure which can be prescribed for execution by technical personnel with no previous mode test experience. Anticipated advantages in the application of this selective orthogonal excitation (SOREX) methodology include 1) the achievement of improved mode isolation, 2) elimination of the need for many shakers, 3) shortened test duration, and 4) freedom from dependence upon special insight of the test conductor. The method derives from a rejection of the classical use of phase coherence of response as a test criterion in favor of a more rational and practicable test logic. b / F g_ [G] / [/] [K] m [M] n q, q Q x,x 7 X ¥ Q ',0 Nomenclature = scalar coefficient = number of shakers = vector of applied forces = hysteretic damping coefficient = generalized damping matrix unit matrix generalized stiffness matrix number of modes mass matrix number of local coordinates generalized coordinate vectors vector of generalized forces local coordinate vectors orthogonality par ameter, Eq. (11) square of frequency ratio contaminated mode vector, Eq. (12) real, imaginary components of admittance, Eq.(9) circular frequency