Equipment and a test method have been developed which can be used to minimize the distortion of frequency response functions from swept sine testing due to non-linearity. The same system can also be used to measure the distortion and quantify the non-linearity. Linearization is performed by using a shaker drive control which causes the article under test to respond at constant displacement amplitude during the sine sweep. Most non-linearities are displacement sensitive, and if the response displacement is held constant, the structure is made to appear linear. The resulting frequency response functions are cleaner and more amenable to data extraction and curve fitting techniques. If characterization of the non-linearity is desired, the same shaker control system holds a sine dwell at the natural frequency of a particular mode while it varies the amplitude of the shaking force over a desired range. The result of this is a series of plots of frequency and damping as a function of either driving point force or displacement. Experimental data are presented to demonstrate the use of this method on a simple non linear test article with single point sine excitation.
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