STATISTICALLY GENERATED WEIGHTED CURVE FIT OF RESIDUAL FUNCTIONS FOR MODAL-ANALYSIS OF STRUCTURES

A statistically generated weighting function for a second-order polyno mial curve fit of residual functions has been developed. The residual flexibility test method, from which a residual function is generated, is a procedure to modal test large structures in a free-free environme nt to measure the effects of higher order modes and stiffness at disti nct degree of freedom interfaces. Due to the present damping estimate limitations in the modal parameter evaluation (natural frequencies and mode shapes) of test data, the residual function has regions of irreg ular data, which should be a smooth curve in a second-order polynomial form. A weighting function of the data is generated by examining the variances between neighboring data points. From a weighted second-orde r polynomial curve fit, an accurate residual flexibility value call be obtained. The residual flexibility value and free-free modes from tes ting are used to improve a mathematical model of the structure, which is used to predict constrained mode shapes.