Fatigue Crack Growth in Complex Residual Stress Fields due to Surface Treatment and Foreign Object Damage under Simulated Flight Cycles

模拟飞行周期下表面处理和异物损坏导致复杂残余应力场中的疲劳裂纹扩展

• 批准号: EP/E05658X/1
• 负责人: Jie Tong
• 金额: $ 35.42万
• 依托单位: University of Portsmouth
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2007
• 资助国家: 英国
• 起止时间: 2007 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FE05658X%2F1
• 关键词: Fatigue; Crack; Growth; Complex; Residual

Damage tolerance approach has been employed in the assessment of structural integrity of critical aeroengine components, where a conjoint action of high cycle fatigue (HCF) and low cycle fatigue (LCF) often occurs. The low cycles are identified with the period between takeoff and landing, while high cycles are a result of inflight aerodynamically induced vibrations. It is imperative that fatigue integrity assessment of aero engine components is carried out under the combined HCF and LCF loading conditions to simulate in service loading conditions. The Portsmouth team is one of the leading exponents in the study of fatigue crack growth under combined HCF and LCF loading conditions, in close collaboration with Rolls-Royce, QinetiQ and US Air Force. In recent years, foreign object damage (FOD) has been identified as one of the main life limiting factors for turbine blades. Impacts due to small hard particle ingestion during takeoff and landing can reach velocities up to 500 m/s and cause severe damage to aerofoils in aero engines. Damage due to FOD is estimated at 4 billion US dollars annually for the aeroengine industry. Reduction in fatigue strength due to projectile impacts has been studied exclusively for HCF loading conditions, mainly in the US. The first study on the effects of combined HCF and LCF under FOD on crack growth was carried out at Portsmouth (GR/R79258). Significant progress has been made in the assessment of residual stresses and their effects on crack driving force. Specifically, tensile residual stresses were found in the vicinity of the crater root made by FOD; and the depth of these tensile stresses can reach to more than 0.2 mm. Upon application of a combined HCF and LCF loading block, the local stress ratios were elevated which prompted early crack growth preferentially from these sites, resulting in significantly increased crack growth rates, as compared with either HCF or LCF loading alone. For aerofoils, the accelerated crack growth was only revealed when the residual stresses due to FOD were considered in the calculation of crack driving force. The leading edge of aerofoils is particularly susceptible to FOD. In recent years, the introduction of advanced surface treatments, such as laser shock peening (LSP) or low plasticity burnishing (LPB), have significantly improved the fatigue strength and crack growth resistance. Such treatments aim at producing significant compressive residual stresses along the leading edge of fan blades, such that the critical region of the blades becomes considerably more damage tolerant to avoid catastrophic failures. Typically, the depths of the compressive residual stresses can be achieved using LSP or LPB are 1-2 mm, as opposed to ~0.2 mm by conventional shot peening. A fundamental understanding of fatigue damage process due to FOD in the presence of LSP/LSB is vital, if they are to be utilized to the full potential in enhancing fatigue resistance of fracture critical components, particularly in the event of FOD.The proposed research aims at developing a predictive model for fatigue crack onset and early growth under simulated flight cycles. The model will take into account of the effect of residual stresses due to surface treatment as well as FOD. Dynamic impact will be modelled and the stabilised and the relaxation of residual stresses will be studied using the finite element analysis and validated by the X-ray diffraction method. The effectiveness of the surface treatment will be evaluated and the model will be validated using simulated inflight test data. Such studies are critical if onset and early crack growth due to FOD is to be modelled accurately, so that predictive tools may be made available to aeroengine industry for FOD-affected fatigue integrity. The work contributes to the safe design and life management of critical aeroengine components such as turbine blades.

损伤容限方法已用于评估航空发动机关键部件的结构完整性，其中经常发生高周疲劳（HCF）和低周疲劳（LCF）的联合作用。低周期是指起飞和着陆之间的时间，而高周期是飞行中空气动力引起的振动的结果。航空发动机部件的疲劳完整性评估必须在 HCF 和 LCF 联合载荷条件下进行，以模拟服役载荷条件。朴茨茅斯团队是 HCF 和 LCF 复合载荷条件下疲劳裂纹扩展研究的领先者之一，与劳斯莱斯、QinetiQ 和美国空军密切合作。近年来，异物损坏（FOD）已被确定为涡轮叶片的主要寿命限制因素之一。起飞和着陆期间吸入的小硬颗粒造成的冲击速度可达 500 m/s，并对航空发动机的机翼造成严重损坏。据估计，航空发动机行业每年因 FOD 造成的损失达 40 亿美元。弹丸撞击导致的疲劳强度降低专门针对 HCF 载荷条件进行了研究，主要是在美国。朴茨茅斯 (GR/R79258) 首次研究了 FOD 下 HCF 和 LCF 组合对裂纹扩展的影响。残余应力及其对裂纹驱动力影响的评估已取得重大进展。具体而言，在FOD形成的凹坑根部附近发现了残余拉应力；这些拉应力的深度可达0.2毫米以上。在应用 HCF 和 LCF 加载块组合时，局部应力比升高，这促使早期裂纹优先从这些位置生长，与单独使用 HCF 或 LCF 加载相比，导致裂纹生长速率显着增加。对于翼型件，只有在计算裂纹驱动力时考虑 FOD 引起的残余应力时，才会显示加速裂纹扩展。机翼的前缘特别容易受到 FOD 的影响。近年来，激光冲击喷丸（LSP）或低塑性抛光（LPB）等先进表面处理技术的引入，显着提高了疲劳强度和抗裂纹扩展能力。这种处理的目的是沿着风扇叶片的前缘产生显着的残余压缩应力，从而使叶片的关键区域变得更加耐损伤，以避免灾难性故障。通常，使用 LSP 或 LPB 可以获得 1-2 毫米的残余压缩应力深度，而传统喷丸处理的残余压缩应力深度约为 0.2 毫米。如果要充分利用 LSP/LSB 的潜力来增强断裂关键部件的抗疲劳性，特别是在发生 FOD 的情况下，对 LSP/LSB 存在下 FOD 引起的疲劳损伤过程的基本了解至关重要。拟议的研究目标开发模拟飞行循环下疲劳裂纹发生和早期扩展的预测模型。该模型将考虑表面处理和 FOD 造成的残余应力的影响。将使用有限元分析对动态冲击进行建模，并研究残余应力的稳定和松弛，并通过 X 射线衍射方法进行验证。将评估表面处理的有效性，并使用模拟飞行测试数据验证模型。如果要对 FOD 引起的裂纹产生和早期裂纹扩展进行准确建模，此类研究至关重要，从而为航空发动机行业提供预测工具，以了解 FOD 影响的疲劳完整性。这项工作有助于涡轮叶片等关键航空发动机部件的安全设计和寿命管理。

项目成果

Residual stress fields after FOD impact on flat and aerofoil-shaped leading edges

• DOI: 10.1016/j.mechmat.2012.08.007
• 发表时间: 2012-12
• 期刊: Mechanics of Materials
• 影响因子: 3.9
• 作者: P. Frankel;P. Withers;M. Preuss;H.T. Wang;J. Tong;D. Rugg

Residual stresses due to foreign object damage in laser-shock peened aerofoils: Simulation and measurement

• DOI: 10.1016/j.mechmat.2014.12.001
• 发表时间: 2015-03-01
• 期刊: MECHANICS OF MATERIALS
• 影响因子: 3.9
• 作者: Lin, B.;Zabeen, S.;Withers, P. J.
• 通讯作者: Withers, P. J.

Evolution of a laser shock peened residual stress field locally with foreign object damage and subsequent fatigue crack growth

• DOI: 10.1016/j.actamat.2014.09.032
• 发表时间: 2015-01-15
• 期刊: ACTA MATERIALIA
• 影响因子: 9.4
• 作者: Zabeen, S.;Preuss, M.;Withers, P. J.
• 通讯作者: Withers, P. J.

Fatigue crack growth in laser-shock-peened Ti-6Al-4V aerofoil specimens due to foreign object damage

• DOI: 10.1016/j.ijfatigue.2013.10.001
• 发表时间: 2014-02-01
• 期刊: INTERNATIONAL JOURNAL OF FATIGUE
• 影响因子: 6
• 作者: Lin, B.;Lupton, C.;Tong, J.
• 通讯作者: Tong, J.

Ratchetting strain as a driving force for fatigue crack growth

• DOI: 10.1016/j.ijfatigue.2012.01.003
• 发表时间: 2013
• 期刊: International Journal of Fatigue
• 影响因子: 6
• 作者: J. Tong;Liguo Zhao;B. Lin