Nonlinear Localization for Shock Isolation of Flexile Structures

Alexander F. Vakakis / Lawrence A. Bergman，伊利诺伊大学厄巴纳-香槟分校项目摘要：提出了一种针对复杂结构在冲击诱发振动下的独特响应减小策略。柔性结构对大震级瞬态输入的脆弱性已得到充分证明。已经提出并在某些情况下实施了各种方法，通过这些方法可以提高这些结构的可靠性。典型的解决方案包括被动隔离和辅助阻尼装置，它们已经使用多年，取得了不同程度的成功。提出的研究的主要重点是基于非线性局部化的概念，开发一种用于柔性结构保护的新型被动非线性隔震系统。在这里，系统不是严格依赖于顺应性和足够的“震动空间”，而是将诱导振动能量被动地限制在一个预先指定的远离主结构的二级系统中，在那里它可以被动地消散。该技术已成功应用于周期性加载的复杂系统，在本项目中，将从分析和实验两方面研究其在瞬态条件下的有效性。该项目包括三个主要任务。首先，将进行一系列一维模拟和比例模型实验，以验证非线性局部化的概念，以保护受到大瞬态输入的柔性结构。接下来，将通过建模和仿真来评估应用于大型复杂结构的冲击隔离系统在一系列多轴瞬态下的性能。最后，将在多轴模拟器上使用更大规模的结构进行概念验证实验。通过使用非线性局部化，产生的冲击隔离系统将起到双重作用，在线性状态下为小规模输入提供保护，在非线性状态下为大规模瞬态提供保护，同时限制在后一种状态下通常需要的保护变形。潜在的回报是更紧凑和有效的被动保护系统。预算修订的影响：最初的两年预算为两位PI中的每一位提供了两个月（每年一个月）的夏季支持，并为两位博士级研究生中的每一位提供了两个日历年的支持。为了将总预算从261,868美元减少到18万美元，每名调查员的夏季支助减少到。每个PI每年10个月。这一变化将影响研究生的暑期学习进度，尽管希望不会产生实质性的影响。此外，一名博士级别的学生被一名硕士级别的学生取代。在实验方面，一维实验不会发生变化。然而，我们将尝试与另一个拥有适当激振器设备的学术机构协调多轴试验项目。假设以最小的成本进行一些协调是可能的，项目的目标将基本保持不变。为了反映这一点，已对预算进行了修订。

Alexander F. Vakakis / Lawrence A. Bergman, Univ. of Illinois at Urbana-ChampaignProposal No. CMS-0000060Proposal Title: Nonlinear Localization for Shock Isolation of Flexible StructuresProject 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.