Deformation and rupture of cylindrical shells under dynamic loading

The dynamic plastic response and failure of unstiffened and ring-stiffened cylindrical shells subjected to dynamic loads were studied. The proposed solution methodology, based on a simple computational model of the shell and the concept of equivalence parameters, incorporated two main load-resisting mechanisms in the shell: stretching in the longitudinal direction and bending in the circumferential direction. From this method, the complicated two-dimensional cylindrical shell problem was reduced to a one-dimensional problem of a string-on-foundation. In particular, the magnitude of the transient and final shape of the transverse deflections of the shell undergoing impact and explosive-type loading were predicted. In order to predict shell failure, the solution for the transient deflection was coupled with a simple fracture criterion the critical strain to rupture. Both exact and approximate solutions for the impact and impulsive loading of the unstiffened shell were compared and gave similar results for high velocity impact and impulsive loading. In the ring-stiffened shell, the overall deflection profile was shown to consist of both a global and local (between stiffeners) deflection fields thereby revealing a complex interplay between the stiffener and the bay. Furthermore, a parametric study on the stiffened shell showed that string-onfoundation model for which ring-stiffeners are represented by lumped masses and springs is a promising method of analyzing the structure. Thesis Supervisor: Professor Tomasz Wierzbicki Title: Professor Dedication I dedicate this thesis to two women: my mother and Row Selman. Acknowledgement There are many people who I need to acknowledge, but the most important one of them all is my advisor and mentor, Tom Wierzbicki. Despite the fact that most of our time was spent arguing, I was very fortunate to have met and worked with such a unique person. I have never learned (and probably will never learn) as much from anyone as I did from Tom Wierzbicki. To me, he remains one of the greatest teacher of all time! Although I did not get to work closely with him until the very end, I would also like to acknowledge Professor Frank McClintock for pointing out inconsistencies where they appear and teaching me of even better ways of writing technical information. It is not often that one gets the attention of an engineering professor who is not only skilled in mechanics but also in the art of writing, and for this reason I am lucky. I thank Mr. William McDonald and Dr. Minos Moussouros of the Naval Surface Warfare Center (White Oak) for providing both financial and educational support that was needed to keep this research ongoing. In particular, I dearly acknowledge Minos for supervising my work on both the dimple ring model and the contribution of the shear work rate. The research was supported by the Office of Naval Research under Contract No. NOOO 14-89-C-0301. During my Ph.D. studies and the development of the thesis, I had the privilege of working with three other people, Professor R. Rosales (Applied Mathematics Department, MIT), Dr. Ion Suliciu, and Dr. Miheala Suliciu (both from the Institute of Mathematics of the Romanian Academy, Romania). Through our meetings and heated discussions, I was able to obtain some knowledge about non-linear wave mechanics and its application to plasticity. The impact of these three people on my work will become more evident when reading the thesis. I would also like to thank Professor Norman Jones (University of Liverpool), Professor Steve Reid (UMIST), and Dr. Bill Stronge (Cambridge University) who were kind enough to allow me to visit their respective universities. By learning of their work, I was able to return to MIT with the valuable information needed to solve some of the problems presented in this thesis. Finally, I would also like to acknowledge some very important people: Professor T. Francis Ogilvie, Row Selman, Muriel Bernier, and Judi Sheytanian. The final semester of Ph.D. studies was an unbearable time for me and without the critical advice from these people, I do not think I could of made it out in one piece. (Actually, I'm not sure I did.)