Aerospace Applications of Quasi Static Modal Analysis with Riveted Joints by Brandon Rapp, Dec. 2025

Aerospace Applications of Quasi Static Modal Analysis with Riveted Joints

Brandon Rapp

Pratt & Whitney

December, 2025

Abstract:

Non-linear modeling of interfaces can be difficult, especially in the case of rivets where the mechanics of the assembly process drive complexities into the assembled joint. One method to bypass the analytical difficulties of modeling riveted joints is to perform testing which is used to calibrate a non-linear joint model, such as a discrete Iwan element, which represents the non-linear friction interaction in the whole joint and replaces a detailed analytical evaluation. Stoker, Gilbert, and Blackham, have recently measured the non-linear response of a thin riveted beam and calibrated the IWAN parameters of such riveted interfaces. The riveted joint model thus derived is applied to two other systems, a riveted beam similar to the BYU system but with modified boundary conditions and a cylindrical duct with multiple layers of riveted sheet metal. Quasi-static modal analysis (QSMA) is used to predict the nonlinear behavior of these structures. These applications represent the extension of the QSMA process from subcomponents to industrial applications. The following discussion will review analysis methodology in applying the rivet IWAN joint, the use of QSMA to derive mode specific non-linear dynamics, application of extended masing rules to predict the non-linear single mode response to sine sweep base excitation input, and finally comparison to test data.

Biography:

Brandon Rapp received his B.S. and M.S. in Mechanical Engineering at Southern Illinois University, Edwardsville, and an additional M.S. in Applied Mathematics from the University of Washington. Brandon Rapp has over fifteen years of experience working in the aerospace field at Pratt and Whitney. His prior research has focused on nonlienar discontinuous systems, near-wall turbulent flow structural response, and industrial damping applications.