Abstract
A statistically generated weighting function for a second-order polynomial 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 environment to measure the effects of higher order modes and stiffness at distinct 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 irregular 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-order polynomial curve fit, an accurate residual flexibility value can be obtained. The residual flexibility value and free-free modes from testing are used to improve a mathematical model of the structure, which is used to predict constrained mode shapes.
Highlights
Correlating a mathematical model with test results requires a modal test of the physical structure
The type of modal testing performed depends on the structure and the type of interfacing the structure has with its environment
Modal testing of a structure is required for correlation of a mathematical model of the structure
Summary
Marshall Space Flight Center (MSFC) Structural Analysis Division, ED23 AL 35812, USA. A statistically generated weighting function for a second-order polynomial 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 afree-free environment to measure the effects ofhigher order modes and stiffness at distinct degree of freedom inteifaces. Due to the present damping estimate limitations in the modal parameter evaluation (naturalfrequencies and mode shapes) oftest data, the residual function has regions of irregular data, which should be a smooth curve in a second-order polynomial form. From a weighted second-order polynomial curve fit, an accurate residual flexibility value can be obtained. The residualflexibility value andfree-free modes from testing are used to improve a mathematical model of the structure, which is used to predict constrained mode shapes
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