Tape joints have been a key tool in assembly of nuclear weapons for almost 40 years. In that time sufficient experience has been gained to have confidence on the robustness of this technology within established design constraints; the structural dynamics of systems assembled by tape joints are much less well understood. Though there is lore that tape joined structures behave linearly in the axial direction, even that is contradicted by the literature, where such structures are found to be bi-linear (nonlinear) in axial modes. Experimental results presented here show much more significant nonlinearity when such systems vibrate in such a way that there is bending across the joint cross-section.In addition, it will be difficult to understand the nonlinear structural dynamics before the pre-loads on the tape joints is known. Therefore, a strategy to deduce the joint pre-loads from surface strain measurements has been developed. This technique exploits finite element analysis to generate an approximate Green's function to map tape loads to surface strain and employs numerical optimization to solve an inverse problem. This technique is demonstrated on the same test specimen employed in the dynamics experiments.
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AcknowledgmentThe authors thank Chi S. ("David") Lo and Jeff Payne for their continued support and patience with respect to the analytic portion of this work. Laura Jacobs-O'Malley is thanked for funding the experimental portion of this work.Michael Jew designed the test specimen employed in this study, but was drawn off by other urgencies before he could perform the tests. That work fell into the hands of Everest Sewell who took the data, Todd Simmermacher who supervised, and Brandon Zwink who helped translate it to Matlab readable form.The authors especially appreciate some very useful suggestions made by Randall Mayes and Michael Ross with respect to the preparation of this report.4