On the Behaviour of Discontinuous Interfaces under Dynamic Loading

不连续的界面，如螺栓连接，给机械部件的设计带来了重大的工程挑战。虽然螺栓联接在经典力学中被很好地理解，但对这种界面在高速碰撞场景中如何反应的理解是有限的。特别是，这对燃气轮机的设计提出了一个重大问题，当地的速度可以很容易地超过数百米每秒(在叶片尖端)。更好地了解这些部件的性能可以实现更精致的涡轮机设计，在减轻重量的同时保持结构完整性。这项拟议的研究旨在促进对非连续界面在承受冲击载荷时的行为的理解，例如存在于螺栓连接中的不连续界面。这将涉及详细的高速率实验和测试后材料分析与数值建模的结合。其目的将是增进对撞击事件期间和之后复杂界面的力学的理解，并提供对数值模拟方法的验证。感兴趣的典型现象可能包括(但不限于)动态摩擦、表面光洁度、摩擦加热、螺栓结构的静态、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充分的结构性理解方面的重要性。最终目的将是为燃气轮机发动机的设计提供参考，以适应风扇叶片关闭等负载情况，其中有多种螺栓连接，直接影响结构的响应和最终的完整性。具体的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。这些特征将在各种不同的高速冲击加载条件下进行测试，以检验上述感兴趣的现象。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性能的理解。该项目还将涉及开发一个精细化的计算模型，并根据通过这项工作构建的大型测试矩阵进行验证，以用于商业有限元代码(例如LS-DYNA或ABAQUS)。该模型将有助于预测风扇叶片关闭事件中不连续界面的行为，以及该区域以外的其他加载场景，从而允许对新叶片设计的成本与保真度进行分析。该项目的一个重要方面是设计一种新的试验平台，专门用于研究螺栓接口。这也可能包括开发定制的夹具来测试螺栓连接。这些夹具的目的是确保螺栓试件的精确预加载，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改装，以进行初步试验，并根据这些试验的结果，开发出完全定制的试验台。这个项目属于EPSRC的工程与制造、未来和物理科学主题。这个项目是与劳斯莱斯合作进行的，劳斯莱斯承诺在DPhil期间支持这个项目。

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.