On the Behaviour of Discontinuous Interfaces under Dynamic Loading

螺栓连接等不连续接口是机械零部件设计的主要工程挑战。虽然螺栓连接在经典力学中得到了相当好的理解，但对这种界面在高速冲击情况下如何反应的理解是有限的。特别地，这对燃气涡轮机的设计提出了主要问题，其中局部速度可以容易地超过每秒数百米（在叶片尖端处）。更好地了解这些部件的性能可以实现更精细的涡轮机设计，在保持结构完整性的同时减轻重量。拟议中的研究旨在推进不连续界面的行为时，受到冲击载荷的理解，如目前在螺栓连接。这将涉及详细的高速率实验和试验后材料分析与数值模拟相结合。目的是加深对撞击事件期间和之后复杂界面力学的理解，并验证数字建模方法。感兴趣的典型现象可以包括（但不限于）动态摩擦、表面光洁度、摩擦加热、螺栓连接结构的静态、动态和模态响应、材料/几何非线性。预计还需要考虑多尺度效应及其在提供全面结构理解方面的重要性。最终目的是为燃气涡轮机发动机的设计提供信息，用于诸如风扇叶片关闭等载荷情况，其中存在直接影响结构响应及其最终完整性的多个螺栓接头。感兴趣的特定接口连接包括但不限于螺栓和螺母、紧固螺母、螺纹孔、垫圈和防旋转装置。将在各种不同的高速冲击载荷条件下测试这些特征，以检查上述感兴趣的现象。通过改变测试参数（如冲击速度、材料类型等），将建立对这些因素如何影响业绩的理解。该项目还将涉及开发一个精细的计算模型，通过这项工作构建的大型测试矩阵进行验证，用于商业有限元代码（例如LS-Dyna或Abaqus）。该模型将是预测风扇叶片关闭事件中的不连续界面行为以及该区域之外的其他加载场景的重要辅助工具，允许对新叶片设计进行成本与保真度分析。该项目的一个重要方面是设计一个新的测试平台，专门用于研究螺栓连接接口。这也可能涉及定制夹具的开发，以测试螺栓连接。这些夹具的目的是确保螺栓连接样本的精确预加载，以及动态加载的良好控制应用。可以对现有的气体驱动装置进行修改以用于初始实验，并且可以基于这些试验的结果来开发完全定制的测试装置。该项目属于工程和制造未来和物理科学的EPSRC主题福尔斯。该项目正在与罗尔斯·罗伊斯公司合作执行，罗尔斯·罗伊斯公司承诺在博士期间支持该项目。

Discontinuous interfaces such as bolted connections present a major engineering challenge for the design of mechanical components. While bolted connections are fairly well understood in classical mechanics, understanding of how such interfaces react in high velocity impact scenarios is limited. In particular this poses a major issue for the design of gas turbines, where local velocities can easily exceed hundreds of meters per second (at the blade tips). A greater understanding of the behaviour of these parts can allow for more refined turbine design, reducing weight while maintaining structural integrity. The proposed research seeks to advance the understanding of the behaviour of discontinuous interfaces when subject to impact loading, such as are present in bolted joints. This will involve a combination of detailed high-rate experimentation and post-test material analysis coupled with numerical modelling. The aim will be to develop an improved understanding of the mechanics of complex interfaces during and after impact events, and to provide validation of numerical modelling approaches. Typical phenomena of interest may include (but not be limited to) dynamic friction, surface finish, frictional heating, static, dynamic and modal response of bolted structures, material/geometric non-linearity. It is also expected that multi-scale effects and their importance in providing full structural understanding will need to be considered. The ultimate destination will be to inform the design of gas turbine engines for load cases such as Fan Blade Off where there is a multiplicity of bolted joints that directly affect the response of the structure and its ultimate integrity. Specific interface joins of interest include, but are not limited to, bolts and nuts, captive nuts, threaded holes, washers & anti-rotation devices. These features will be tested under various different high velocity impact loading conditions to examine the aforementioned phenomena of interest. By varying test parameters (such as impact velocity, material type, etc.), an understanding of how these factors influence performance will be established. This project will also involve the development of a refined computational model, validated against the large test matrix constructed through this work, for use in commercial finite element codes (e.g. LS-Dyna or Abaqus). This model will be an important aid to predicting the behaviour of discontinuous interfaces in Fan Blade off events as well as other loading scenarios outside of this area, allowing for cost versus fidelity analysis of new blade designs. One important aspect of this project is the design of a new test platform dedicated to the study of bolted interfaces. This may also involve the development of bespoke fixtures to test bolted connections. The purpose of these fixtures will be to ensure precise pre-loading of the bolted specimen, and the well-controlled application of dynamic loading. Pre-existing gas-driven apparatus may be modified for initial experiments and based on the results of these trials a fully bespoke test rig may be developed. This project falls within the EPSRC themes of Engineering and Manufacturing the Future and Physical Sciences. This project is being performed in collaboration with Rolls Royce, who have committed to support this for the duration of the DPhil.