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.

航空发动机关键部件经常发生高周疲劳（HCF）和低周疲劳（LCF）的联合作用，损伤容限方法已被应用于其结构完整性评估。低周波与起飞和着陆之间的时间段有关，而高周波则是飞行中空气动力引起的振动的结果。为了模拟航空发动机的服役状态，对发动机零部件进行高周疲劳和低周疲劳复合载荷下的疲劳完整性评估是十分必要的。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主要代表之一，与劳斯莱斯、QinetiQ和美国空军密切合作。近年来，外来物损伤（FOD）已被确定为涡轮机叶片的主要寿命限制因素之一。在起飞和着陆过程中，由于吸入小的硬颗粒而产生的冲击可达到高达500 m/s的速度，并对航空发动机中的翼型造成严重损坏。据估计，航空发动机工业每年因FOD造成的损失为40亿美元。在疲劳强度减少由于弹丸的影响已经专门研究了HCF加载条件下，主要是在美国。在朴茨茅斯（GR/R79258）进行了第一项关于FOD下HCF和LCF组合对裂纹扩展影响的研究。残余应力及其对裂纹驱动力影响的研究取得了重大进展。具体地说，拉伸残余应力被发现在附近的弹坑根部由FOD;当施加HCF和LCF组合加载块时，局部应力比升高，这促使早期裂纹优先从这些位置扩展，导致裂纹扩展速率显著增加，与单独的HCF或LCF负载相比。对于翼型，只有在计算裂纹驱动力时考虑了FOD引起的残余应力，才能揭示裂纹加速扩展的规律。翼型的前缘特别容易受到FOD的影响。近年来，先进的表面处理，如激光冲击强化（LSP）或低塑性抛光（LPB）的引入，显着提高了疲劳强度和裂纹扩展阻力。这种处理的目的是沿着风扇叶片的前缘沿着产生显著的压缩残余应力，使得叶片的关键区域变得相当多的损伤容限，以避免灾难性故障。通常，使用LSP或LPB可以实现的压缩残余应力的深度为1-2 mm，而传统喷丸处理的深度为~0.2 mm。疲劳损伤过程中由于外物损伤的LSP/LSB的存在下的一个基本的理解是至关重要的，如果他们被利用到最大的潜力，在提高抗疲劳断裂的关键部件，特别是在FOD.The拟议的研究旨在开发一个预测模型疲劳裂纹萌生和早期增长下模拟飞行循环。该模型将考虑由于表面处理以及FOD的残余应力的影响。动态冲击将建模和稳定和残余应力的松弛将使用有限元分析和验证的X射线衍射方法进行研究。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。这些研究是至关重要的，如果发病和早期裂纹扩展由于FOD是准确建模，使预测工具可用于航空发动机工业FOD影响的疲劳完整性。该工作有助于航空发动机关键部件如涡轮机叶片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.

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.

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.

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