Frictional damping effects on structural dynamics

摩擦阻尼对结构动力学的影响

• 批准号: 2517938
• 金额: --
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2018
• 资助国家: 英国
• 起止时间: 2018 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2517938
• 关键词: Frictional; damping; effects; structural; dynamics

This DPhil project is an Industrial Case (IC) sponsored by EPSRC and Rolls-Royce plc. It falls within the EPSRC research area "Performance and inspection of mechanical structures and systems". The project focuses on the development of a fundamental understanding of friction damping effects on vibrating structures. In jointed structures, the friction generated in the interfaces between different components is known to lead to detrimental effects, such as noise, wear and fatigue damage. However, friction damping can also serve purposes such as energy dissipation, isolation and vibration control. Friction dampers are commonly used in several engineering systems, including civil buildings and turbomachines. Nonetheless, some behaviours due to friction damping, such as the periodic or permanent sticking of the parts in contact or the amplification of the dynamic response within certain frequency ranges, can lead to losses of efficiency and unexpected failures, if unaccounted during the design stage. Therefore, a deeper understanding of these phenomena, as well as the development of reliable approaches for monitoring friction in engineering structures, are essential not only to prevent failures but also to allow the exploration of innovative and efficient design solutions including friction dampers.The current understanding of friction damping effects is still limited, even when simplifying assumptions are considered for structural models, dynamic loadings and friction forces. Therefore, the research strategy followed in this project consists in the development of a series of case-studies where discrete single-degree-of-freedom (SDOF) and multi-degree-of-freedom (MDOF) mass-spring systems are subjected to harmonic loadings and Coulomb friction. These mechanical models are typically considered during the early design stages for structures such as buildings, bladed-disks, mechanical suspensions, braking systems and many others, and allow a high-level investigation of their global dynamic behaviour. In discrete mechanical models, friction damping is usually introduced by considering a contact between one of the masses of the system and a ground-fixed wall. Nonetheless, in engineering applications such as the dovetail joints in gas-turbine blades or the friction dampers located between two different storeys of a building, friction contacts occur between two oscillating components. In the above case-studies, this problem is addressed by also considering friction contacts occurring between two different masses of the system or between a mass and an oscillating base.The dynamic behaviour of these friction damped systems is investigated by combining theory, numerical and experimental approaches. The main challenges addressed from this investigation are:- establishing when the relative motion in a friction contact is characterised by a continuous, stick-slip or stuck motion regime depending on the physical parameters of the problem; - understanding how friction damping affects features of the dynamic response such as resonances, invariant points, low- and high-frequency behaviours; - developing experimental techniques and metrics for detecting and quantifying friction from the response signature of a structure. The first two challenges are addressed by deriving analytical closed-form solutions and developing effective numerical approaches. To date, this study has provided an in-depth understanding of friction damping effects on response features such resonances, invariant points, low- and high-frequency behaviours. Moreover, analytical solutions led to the development of 2-D maps allowing a quick prediction of the motion regime during the design stage. Finally, experimental investigations have been carried out on single- and two-storeys shear frames, providing a validation for the theoretical results and a further insight on the behaviour of metal-to-metal contacts.

该DPhil项目是由EPSRC和Rolls-Royce plc赞助的工业案例（IC）。它福尔斯EPSRC研究领域“机械结构和系统的性能和检测”。该项目的重点是对振动结构的摩擦阻尼效应的基本认识的发展。在连接结构中，已知在不同部件之间的界面中产生的摩擦导致有害影响，例如噪声、磨损和疲劳损伤。然而，摩擦阻尼也可以用于诸如能量耗散、隔离和振动控制的目的。摩擦阻尼器广泛应用于民用建筑和建筑等工程系统中。尽管如此，由于摩擦阻尼的一些行为，如接触部件的周期性或永久性粘附或在某些频率范围内的动态响应放大，如果在设计阶段未考虑，可能导致效率损失和意外故障。因此，深入了解这些现象，以及开发可靠的方法来监测工程结构中的摩擦，不仅是必要的，以防止故障，而且还允许探索创新和有效的设计解决方案，包括摩擦阻尼器。目前的理解摩擦阻尼效应仍然是有限的，即使简化假设被认为是结构模型，动载荷和摩擦力。因此，在这个项目中遵循的研究策略包括在一系列的情况下，研究离散的单自由度（SDOF）和多自由度（MDOF）的质量弹簧系统进行谐波载荷和库仑摩擦的发展。这些力学模型通常在建筑物、叶片盘、机械悬架、制动系统等结构的早期设计阶段被考虑，并允许对其全局动态行为进行高层次的研究。在离散力学模型中，摩擦阻尼通常通过考虑系统的一个质量与地面固定壁之间的接触来引入。然而，在工程应用中，例如燃气涡轮叶片中的燕尾接头或位于建筑物的两个不同楼层之间的摩擦阻尼器，两个振荡部件之间发生摩擦接触。在上述案例研究中，我们还考虑了系统中两个不同质量之间或质量与振动基座之间的摩擦接触，并结合理论、数值和实验方法研究了这些摩擦阻尼系统的动力学行为。从这项调查中解决的主要挑战是：-建立摩擦接触中的相对运动时，其特征在于一个连续的，粘滑或卡住的运动制度，这取决于问题的物理参数; -了解摩擦阻尼如何影响动态响应的功能，如共振，不变点，低频和高频行为; -开发实验技术和指标，用于检测和量化结构的响应签名的摩擦。前两个挑战是通过推导解析封闭形式的解决方案和开发有效的数值方法来解决的。到目前为止，这项研究提供了一个深入的了解摩擦阻尼效应的响应功能，如共振，不变点，低频和高频行为。此外，分析解决方案导致2-D地图的发展，允许在设计阶段的运动状态的快速预测。最后，实验研究已进行了单层和两层剪切框架，提供了一个验证的理论结果和进一步了解的行为，金属对金属的接触。