Collaborative Research: New Nonlinear Modal Analysis Framework for Multi-Scale Modeling of Structures with Bolted Interfaces

合作研究：用于螺栓连接结构多尺度建模的新型非线性模态分析框架

• 批准号: 1561810
• 负责人: Matthew Allen
• 金额: $ 30万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-01 至 2020-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1561810&HistoricalAwards=false
• 关键词: Collaborative; Research; New; Nonlinear; Modal

Engineers in many industries use the finite element method to divide structures into small elements so that the equations governing each can be found and solved by computers. This allows one to compute the stresses and deformation of structures with complicated shapes such as airplanes, machines, biomedical implants, etc. and to predict whether the structure can survive the loads it will experience in operation. While this method has proven very effective in many scenarios, even modern computers are not powerful enough to model the interfaces between parts accurately. As a result, billions of dollars are spent annually testing structures to determine the stiffness of interfaces, such as bolted connections, in order to adjust the simulation models so that they better capture the real behavior of the structure. This makes new machines much more expensive and often leads to designs that break prematurely, potentially endangering lives. Prediction is particularly difficult when a structure, such as an aircraft, experiences dynamic loads due to turbulence in the air passing over the wings. This work will explore a new means of simulating the motion of structures with bolted interfaces and will perform experiments to seek to understand how to model friction and microscopic slip in the joints and its effect on vibration damping. The methodology can be easily integrated in existing finite element software, to facilitate its transition and broad adoption. The research will be complemented by outreach activities at the PIs institutions and a short course exposing students and researchers to the technique formulated as part of the project.The physics that are responsible for energy dissipation in mechanical joints are complicated and span the full range of length scales. While much has been learned in recent years about the nature of nano- and meso-scale contact interfaces, friction is exceedingly complicated and may be influenced by local elasticity, chemistry, plasticity, surface roughness and lubrication provided by oxides or thin layers of wear particles. This work posits a new reduced order modeling framework that allows one to connect the physics of small scale contacts to the global motion of the assembly. An extension to modal analysis that can then be used to obtain a wealth of insight into the response of the structure under a variety of loading conditions. The methodology will be validated through simulations on various structures and through experiments on assemblies with bolted interfaces, providing new insights into the role of interfaces on a structure's response. Simulations will be performed to understand how the features/parameters of various friction laws manifest themselves in the damping and nonlinearity of the global dynamic response.

许多行业的工程师使用有限元法将结构划分为小单元，以便计算机可以找到并求解控制每个单元的方程。 这使得人们可以计算具有复杂形状的结构（如飞机，机器，生物医学植入物等）的应力和变形，并预测结构是否能够承受其在操作中将经历的负载。 虽然这种方法在许多情况下都被证明是非常有效的，但即使是现代计算机也没有足够的能力来准确地建模部件之间的接口。 因此，每年花费数十亿美元测试结构以确定界面（例如螺栓连接）的刚度，以便调整仿真模型，使得它们更好地捕捉结构的真实的行为。 这使得新机器更加昂贵，并且经常导致设计过早破裂，可能危及生命。 当一个结构，如飞机，经历动态载荷时，由于空气中的湍流通过机翼，预测是特别困难的。 这项工作将探索一种新的方法来模拟螺栓连接界面的结构的运动，并将进行实验，以寻求了解如何建模摩擦和微观滑动的关节及其对振动阻尼的影响。该方法可以很容易地集成到现有的有限元软件，以促进其过渡和广泛采用。该研究将通过在PI机构的推广活动和短期课程来补充，使学生和研究人员了解作为项目一部分制定的技术。负责机械关节中能量耗散的物理学是复杂的，跨越整个长度范围。 虽然近年来已经了解了很多关于纳米和介观尺度接触界面的性质，但摩擦是非常复杂的，并且可能受到局部弹性、化学、塑性、表面粗糙度和由氧化物或磨损颗粒薄层提供的润滑的影响。 这项工作假定一个新的降阶建模框架，允许一个连接的物理小规模接触的全球运动的装配。 对模态分析的扩展，可用于深入了解结构在各种载荷条件下的响应。 该方法将通过对各种结构的模拟和对螺栓连接接口的组件的实验进行验证，从而为接口对结构响应的作用提供新的见解。 将进行模拟，以了解各种摩擦定律的特征/参数如何在全局动态响应的阻尼和非线性中表现出来。