Topics On Flexible Airplane Dynamics Pt 1 Residual Stiffness Effects In Truncated Modal Analysis PDF Download

The flexible airframe equations of motion are derived with an arbitrary number of elastic de grees of freedom included. The number of equa tions is reduced to include only those necessary for adequate dynammic representation of the air frame, and the effects of the excluded modes are shown. The result is that a matrix X sub in finity must be calculated which is a function of the flexibility represented by the excluded modes. The calculation of this matrix is com plicated by the fact that it is, in explicit form, a function of the mode shapes for the ex cluded elastic degrees of freedom. Usually only a few of these higher order mode shapes can be found withh any accuracy. The problem is resolved by identifying two quantities, X sub f and X sub f infinity, which are ssuperposable to give the complete effects of structural static deflections, X sub infinity. This physi cally satisfying result is implemented by re lating X sub f infinity and X sub f to basic geometrical, inertial, and stiffness properties. The solution is completely general and applies to all elastic systems. (Author).