CAREER: Nonlinear Dynamics of Assemblies at High Temperatures

这个职业生涯项目将支持研究，这将有助于在高温下运行的结构故障的新知识。这对于发动机尤其重要，例如喷气式飞机上的航空涡轮机或发电厂中的燃气涡轮机。从事这些发动机设计的工程师面临的一个挑战是，他们必须设计一种必须在通常超过1400摄氏度的温度下运行的结构。如此高的温度会显著改变部件的性能;然而，对于这些部件中的特定疲劳（即损坏）机制如何随温度变化，了解甚少。该项目的重点是基础研究，可以导致所需的知识，以改善这些结构的设计过程。这些新知识将使工程师能够设计更高效的结构，不需要频繁维护，并将提供计算工具来预测结构在整个生命周期中的性能。该项目是建立在PI的努力，创造一个研究经验，从事代表性不足的群体，提供指导，并建立一个同行和外部支持网络。这个CAREER项目的主要研究目标是测试的假设，接口消耗更多的能量在组件在高温下比微动实验或模型校准到低温环境的预测。第二个目标是应用复杂的步骤定理和广义复数理论的领域，以创建一个新的方法参数化的非线性结构动力学模型作为温度的函数。为了实现这些目标，将追求实验和理论进步。实验将侧重于发现结构中的非线性如何随着温度的变化而变化，以及多个非线性如何相互作用（例如，由于平面内拉伸而具有几何非线性的火箭面板和由于螺栓连接而具有界面非线性）。同时，一个新的，参数化的降阶模型将被提出，表示一个系统的温度方面的数值模型，并将通过实验进行验证。该建模框架是基于一个复杂的步骤定理，通过在系统中引入广义复数相对于一个指定的变量来评估系统的灵敏度的扩展？该奖项反映了NSF的法定使命，并被认为是值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估的支持。

This CAREER project will support research that will contribute new knowledge related to the failure of structures that operate at high temperatures. This is particularly important for engines, such as the aeroturbines found on jets, or the gas turbines found throughout power plants. One challenge facing design engineers working on these engines is that they must design a structure that has to operate at temperatures often in excess of 1400 degree Celsius. Temperatures this high significantly change the way in which components perform; however, very little knowledge exists for how the specific fatigue (i.e. damage) mechanisms in these components evolve with temperature. This project focuses on fundamental research that can lead to the needed knowledge for improving the design process of these structures. The new knowledge will enable engineers to design more efficient structures that don't need frequent maintenance and will provide computational tools to predict the performance of a structure over its entire life cycle. This project is built on the PI's efforts to create a research experience that engages underrepresented groups, provides mentorship, and builds a peer and external support network.The primary research objective of this CAREER project is to test the hypothesis that interfaces dissipate more energy in assemblies at high temperatures than predicted by fretting experiments or models calibrated to low temperature environments. A second objective is to apply the complex step theorem and the field of generalized complex number theory to create a new method for parameterizing nonlinear structural dynamics models as functions of temperature. To accomplish these objectives, both experimentation and theoretical advancement will be pursued. Experiments will focus on discovering how nonlinearities in structures evolve as a function of temperature, and how multiple nonlinearities interact (e.g. a rocket panel that has geometric nonlinearities due to in-plane stretching and interfacial nonlinearities due to bolted joints). In parallel, a new, parameterized reduced order model will be proposed that expresses the numerical model of a system in terms of temperature and will be validated by the experiments. This modeling framework is based on an extension of the complex step theorem to evaluate sensitivities of a system with respect to a specified variable through the introduction of generalized complex numbers in the system?s definition.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.