Investigation into the fundamentals of contact mechanics in turbine blades roots to enable improved techniques for design optimisation and reliability

在涡轮风扇发动机中，在风扇叶片的基部处存在大量金属对金属接触。这些接触受到变化的负载，这是由于热效应和发动机振动引起的;在这些条件下，可能发生称为微动疲劳的损坏现象。了解导致材料退化和裂纹萌生的过程和条件对于准确预测发动机部件的寿命和确保发动机设计的安全性至关重要。这项工作的总体目标是促进对涡轮机叶片根部接触力学的理解，通过加强对接触附近应力状态的理解，改进设计优化和寿命预测技术。该项目将补充罗尔斯公司正在进行的基础接触研究。Royce plc作为其Cornerstone研究项目的一部分，将在基础水平上纳入接触工作，但也将考虑特定于涡轮机部件的特征。研究各种参数对触点预期寿命的影响。测试中需要考虑的参数包括：单晶材料中的材料取向效应、接触几何形状（平面/桶形）、局部几何形状效应（例如，应力集中点（如缺口或拐角）的接近度）和温度。许多这些接触特性（如材料取向效应和局部几何效应）以前没有在微动疲劳的背景下进行过任何深入的研究，因此，他们的影响目前知之甚少。测试结果将用于促进对基本力学和所研究参数影响的理解。该项目的另一部分将是分析性质的;根据实验结果，将开发数值和分析模型，以模拟接触的应力状态和预期寿命。接触压力、剪切牵引力及其相关应力场的建模方法可能包括：使用有限元软件、分布式位错技术、直接解析解和使用渐近应力场。这些方法将需要修改其标准形式，以允许正在调查的影响。该项目福尔斯EPSRC工程主题，并与材料工程-金属和合金研究领域有关。

In a turbofan engine a large number of metal on metal contacts are present at the base of the fan blades. Theses contacts are subject to varying loads, both due to thermal effects and resulting from vibrations present with the engine; under these conditions a damage phenomenon known as fretting fatigue can occur. Understanding processes and conditions that lead to material degradation and crack initiation is crucial to accurately predict the lifetime of engine components, and to ensure safety in engine design. The overall goal of this work is to advance the understanding of contact mechanics in turbine blade roots to enable improved techniques for design optimisation and life prediction via enhanced understanding of the stress-state in the vicinity of the contact.The project will be complementary to the fundamental contact research being undertaken by Rolls-Royce plc as part of their Cornerstone research project and will incorporate work on contacts at a fundamental level but will also consider features specific to turbine components.A part of this project will involve an experimental investigation into the effect of various parameters on the expected lifespan of a contact. Parameters to be considered for testing include; material orientation effects in single crystal materials, contact geometry (flat/barrelled), local geometry effects (e.g. proximity of stress raisers such as notches or corners) & temperature. Many of these contact properties (such as material orientation effects and local geometry effects) have not previously been studied in any depth in the context of fretting fatigue, and as such their effects are currently poorly understood. The test results will be used to advance understanding of the fundamental mechanics and the influence of the parameters investigated.The other part of this project will be analytical in nature; informed by the results of the experiments numerical and analytical models will be developed to model the state of stress and expected lifetime of the contact. Methods employed in modelling the contact pressure, shear traction and their associated stress fields may include; The use of Finite element software, The Distributed dislocation technique, Direct analytical solutions and the use of asymptotic stress fields. These methods will require modification from their standard forms to allow for the effects being investigated.This project falls within the EPSRC engineering Theme and is related to the Materials Engineering - Metals & Alloys research area.