BASIC MECHANICAL INTERACTIONS IN SHAKER TESTING

Simple models representing a shaker and a test object are used to illu strate changes in test object response due to shaker dynamics and diff erences between the test and service environment. The degree of coupli ng is quantified in terms of ratios of the natural frequencies and the masses. Regions of overstress can depend on reproducing absolute rath er than relative motion in a lest. Shaker tests reproducing output spe ctra observed in service, when shaker/fixture impedance is higher than the impedance in service, is shown to cause overtest at frequencies b elow natural frequencies of the service environment.