Nonlinear Localization for Shock Isolation of Flexile Structures

亚历山大·瓦卡基斯/劳伦斯·A·伯格曼，大学伊利诺伊州厄巴纳-香槟分校CMS-0000060建议标题：柔性结构的非线性局部化隔振项目摘要：提出了一种适用于复杂结构在冲击振动下的独特响应减振策略。柔性结构对大幅值瞬时输入的脆弱性是有据可查的。已经提出了各种方法，并在某些情况下实现了这些方法，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减震装置，这些装置已经使用多年，取得了不同程度的成功。提出的研究重点是基于非线性局部化的概念，开发一种新型的用于柔性结构保护的被动非线性隔震系统。在这里，该系统不是严格依赖于顺应性和足够的“摇摆空间”，而是将诱导的振动能量被动地限制在一个预先分配的二级系统中，远离要隔离的主结构，在那里它可以被被动消散。该技术已成功地应用于周期载荷作用下的复杂系统，本项目将从解析和实验两个方面研究其在暂态条件下的有效性。首先，将进行一系列一维模拟和缩尺模型实验，以验证非线性局部化的概念在保护受大的瞬时输入的柔性结构的背景下的有效性。接下来，将通过建模和仿真来评估应用于大型复杂结构的隔振系统在一系列多轴瞬变情况下的性能。最后，在多轴模拟器上进行了大尺度结构的概念验证实验，通过使用非线性局部化，所得到的隔震系统将具有双重用途，既为小尺度输入提供线性区域的保护，又为较大范围的瞬变过程提供非线性区域的保护，同时限制后者区域通常需要的变形。潜在的回报是更加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名PI每人提供了总共两个月(每年一个月)的暑期支助，为两名博士水平的研究生每人提供了两个日历年的支助。为了将预算总额从261 868美元减少到180 000美元，每个调查员的暑期支助减至每年0.1个月。这一变化将对研究生的暑期进步产生影响，尽管希望不会有太大影响。此外，一名博士水平的学生已经被一名硕士水平的学生取代。在实验方面，一维实验不会改变。然而，我们将尝试与另一家拥有适当摇床设施的学术机构协调多轴试验计划。假设可以以最小的成本进行一些协调，项目的目标将从根本上保持不变。预算已经修订，以反映这一点。

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.