Alexander F. Vakakis / Lawrence A. Bergman, Univ. of Illinois at Urbana-Champaign Proposal No. CMS-0000060 Proposal Title: Nonlinear Localization for Shock Isolation of Flexible Structures
Project Abstract:
A unique response reduction strategy for complex structures subjected to shock-induced vibrations is proposed. The vulnerability of flexible structures to large magnitude transient inputs is well documented. Various methods have been proposed and, in some cases, implemented through which the reliability of these structures can be enhanced. Typical solutions include passive isolation and auxiliary damping devices, which have been employed for many years with varying degrees of success. The primary focus of the proposed research is the development of a new type of passive nonlinear shock isolation system for protection of flexible structures, based upon the concept of nonlinear localization. Here, rather than relying strictly on compliance and adequate "rattle space," the system takes induced vibrational energy and passively confines it to a preassigned secondary system away from the primary structure to be isolated, where it can be passively dissipated. The technique has been applied successfully to complex systems subjected to periodic loading, and in this project its efficacy under transient conditions will be studied, both analytically and experimentally. The project consists of three main tasks. First, a series of one-dimensional simulations and scale model experiments will be conducted to validate the concept of nonlinear localization in the context of protecting flexible structures subjected to large, transient inputs. Next, performance of a shock isolation system applied to a large, complex structure subjected to a series of multi-axial transients will be evaluated by modeling and simulation. Finally, a proof of concept experiment will be conducted using a larger scale structure on a multi-axis simulator. Through the use of nonlinear localization, the resulting shock isolation system will serve a dual purpose, providing protection in the linear regime for small-scale inputs and in the nonlinear regime for larger scale transients, while limiting the deformation ordinarily required for protection in the latter regime. The potential payoff is more compact and efficient passive protective systems.
Impact of Budget Revision:
The original two year budget provided for a total of two months (one month per year) of summer support for each of the two PI's and two calendar years of support for each of 2 Ph.D.-level graduate students. In order to reduce the overall budget from $261,868 to $180,000, summer support for each investigator is reduced to .10 month per year for each PI. This change will impact the summer progress of the graduate students, though hopefully not in a substantial way. Further, one Ph.D.-level student has been replaced by an M.S.-level student. On the experimental side, there will be no change to the one-dimensional experiment. We will, however, attempt to coordinate the multi-axial test program with another academic institution having an appropriate shaker facility. Assuming some coordination is possible at minimal cost, the goals of the project will remain fundamentally unchanged. The budget has been revised to reflect this.
