International Journal of Fatigue最新文献_第8页

A novel bidirectional LSTM network model for very high cycle random fatigue performance of CFRP composite thin plates 针对 CFRP 复合材料薄板超高循环随机疲劳性能的新型双向 LSTM 网络模型

IF 5.7 2区材料科学 Q1 ENGINEERING, MECHANICAL

International Journal of Fatigue

Pub Date : 2024-09-29 DOI: 10.1016/j.ijfatigue.2024.108627

Yueao Jian , Peng Hu , Qihan Zhou , Nan Zhang , Deng’an Cai , Guangming Zhou , Xinwei Wang

This study proposes a novel Double-layer Bidirectional Long Short-Term Memory (BiLSTM) neural network model, shorted as TDA-BiLSTM, which integrates Transfer learning and Attention mechanisms. The model aims to predict the fatigue life of carbon fiber reinforced polymer (CFRP) thin plate structures subjected to very high cycle random vibration fatigue loads. Distinct from conventional servo-hydraulic and ultrasonic fatigue testing methods, this research pioneers the use of a vibration table for very high cycle fatigue (VHCF) testing to fill the gap in the field. By training and validating data across various life ranges, the TDA-BiLSTM model demonstrates significant advantages in training speed and predicting accuracy. Its bidirectional structure and attention mechanism effectively capture complex patterns and long-term dependencies in sequence data. Experimental results indicate that the TDA-BiLSTM model achieves significantly lower Mean Absolute Error (MAE) and Root Mean Square Error (RMSE) compared to Long Short-Term Memory (LSTM) and Long Short-Term Memory with Transfer learning (Tr-LSTM) models across different life ranges on the ε-N curve, indicating higher accuracy and stability in strain life prediction tasks. Additionally, an analysis of typical damage areas using Scanning Electron Microscopy (SEM) reveals the failure mechanisms of CFRP plates under very high cycle vibration fatigue loads.

本研究提出了一种新颖的双层双向长短期记忆（BiLSTM）神经网络模型，简称为 TDA-BiLSTM，它集成了迁移学习和注意机制。该模型旨在预测承受极高循环随机振动疲劳载荷的碳纤维增强聚合物（CFRP）薄板结构的疲劳寿命。与传统的伺服液压和超声波疲劳测试方法不同，该研究率先使用振动台进行超高循环疲劳（VHCF）测试，填补了该领域的空白。通过对不同寿命范围的数据进行训练和验证，TDA-BiLSTM 模型在训练速度和预测准确性方面表现出显著优势。其双向结构和注意力机制能有效捕捉序列数据中的复杂模式和长期依赖关系。实验结果表明，在ε-N 曲线上的不同寿命范围内，TDA-BiLSTM 模型的平均绝对误差（MAE）和均方根误差（RMSE）明显低于长短期记忆（LSTM）模型和带迁移学习的长短期记忆（Tr-LSTM）模型，这表明其在应变寿命预测任务中具有更高的准确性和稳定性。此外，利用扫描电子显微镜（SEM）对典型损伤区域的分析揭示了 CFRP 板在极高循环振动疲劳载荷下的失效机制。

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引用次数: 0

Predicting the fatigue life of T800 carbon fiber composite structural component based on fatigue experiments of unidirectional laminates 基于单向层压板疲劳实验预测 T800 碳纤维复合材料结构件的疲劳寿命

IF 5.7 2区材料科学 Q1 ENGINEERING, MECHANICAL

International Journal of Fatigue

Pub Date : 2024-09-28 DOI: 10.1016/j.ijfatigue.2024.108622

Yidong Zhang , Tao Zheng , Gang Liu , Huihu Lu , Guang Li , Qingsong Zong , Yunpeng Gao , Wei Zhang

This study is based on the fatigue experiment results of unidirectional laminates and investigates the fatigue performance of T800 carbon fiber/epoxy resin composite structural components through experimental and numerical analysis. Fatigue experiments were performed on [0]₁₆, [90]₁₆, and [±45]₈ laminates individually, obtaining the fundamental fatigue parameters necessary for modeling. The fatigue life model for T800 carbon fiber/epoxy resin unidirectional laminates was refined, and fatigue degradation rules were provided for the fatigue progressive damage model. A fatigue progressive damage analysis model for T800 laminates was established based on the 3D Hashin criterion, predicting the fatigue life and fatigue damage failure process of the laminates. A fatigue life prediction model was developed for T800 carbon fiber composite I-beam structural components, which can predict the primary types of fatigue failure, fatigue life and the location of fatigue failure occurrence. The predicted fatigue life of structural components shows good consistency with the experimental results. This method can calculate structural components including ply angles of 0°, 45°, and 90° and obtain the fatigue life contour.

本研究以单向层压板的疲劳实验结果为基础，通过实验和数值分析研究了 T800 碳纤维/环氧树脂复合材料结构组件的疲劳性能。分别对 [0]16、[90]16 和 [±45]8 薄片进行了疲劳实验，获得了建模所需的基本疲劳参数。完善了 T800 碳纤维/环氧树脂单向层压板的疲劳寿命模型，并为疲劳渐进损伤模型提供了疲劳退化规则。根据三维哈辛准则建立了 T800 板材的疲劳渐进损伤分析模型，预测了板材的疲劳寿命和疲劳损伤失效过程。建立了 T800 碳纤维复合材料工字钢结构件的疲劳寿命预测模型，可预测疲劳破坏的主要类型、疲劳寿命和疲劳破坏发生的位置。预测的结构部件疲劳寿命与实验结果具有良好的一致性。该方法可计算包括 0°、45° 和 90°层角的结构部件，并获得疲劳寿命等值线。

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引用次数: 0

In-plane biaxial fatigue life prediction model for high-cycle fatigue under synchronous sinusoidal loading 同步正弦加载下高循环疲劳的面内双轴疲劳寿命预测模型

IF 5.7 2区材料科学 Q1 ENGINEERING, MECHANICAL

International Journal of Fatigue

Pub Date : 2024-09-27 DOI: 10.1016/j.ijfatigue.2024.108618

Youzhi Liu , Qianyang Sun , Dahai Zhang , Peiwei Zhang , Peifei Xu , Qingguo Fei

The unique advantage of in-plane biaxial loading is no rotation of the maximum principal stress during cyclic loading, which has a distinct effect on fatigue life. This study aims to propose a life prediction model for in-plane biaxial fatigue encompassing both in-phase and out-of-phase conditions. For synchronous sinusoidal loadings, an equivalent stress expression is derived using the integral method, accounting for the influences of shear and normal stresses across all planes. The equivalent stress is then compared to a reversed uniaxial constant amplitude loading to predict fatigue life. To validate and compare the model, in-phase and out-of-phase in-plane biaxial fatigue experiments were conducted using 24 nickel-based superalloy cruciform specimens at temperatures of 420℃, 550℃, and 600℃. The results show that the proposed model is superior to conventional stress-invariant based models, with most results staying within the ± 2 error bands. Using the proposed model, the effects of mean tensile stress, biaxiality and phase shift are discussed. Additionally, a novel non-proportional factor is introduced to enhance multiaxial fatigue life prediction by distinctly separating the effects of principal stress and its directional variations.

面内双轴加载的独特优势在于循环加载时最大主应力不会发生旋转，这对疲劳寿命有明显的影响。本研究旨在提出一种平面内双轴疲劳寿命预测模型，包括相内和相外两种情况。对于同步正弦加载，采用积分法推导出等效应力表达式，其中考虑到了所有平面的剪应力和法向应力的影响。然后将等效应力与反向单轴恒幅加载进行比较，以预测疲劳寿命。为了验证和比较该模型，使用 24 个镍基超合金十字形试样在 420℃、550℃ 和 600℃温度下进行了相内和相外平面双轴疲劳实验。结果表明，所提出的模型优于传统的基于应力不变量的模型，大多数结果的误差都在± 2 范围内。利用提出的模型，讨论了平均拉伸应力、双轴性和相移的影响。此外，还引入了一个新的非比例因子，通过明确区分主应力及其方向变化的影响来增强多轴疲劳寿命预测。

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引用次数: 0

Fatigue life prediction method for bolted joints based on equivalent structural stress under tensile–compressive loading 基于拉伸-压缩载荷下等效结构应力的螺栓连接疲劳寿命预测方法

IF 5.7 2区材料科学 Q1 ENGINEERING, MECHANICAL

International Journal of Fatigue

Pub Date : 2024-09-26 DOI: 10.1016/j.ijfatigue.2024.108625

Long Yang , Guangwu Yang , Zhe Zhang , Yuqing Yuan , Guozheng Kang

In this study, load amplitude–life (F_a–N) curves were obtained through tensile–compressive fatigue tests of bolted joints. It was observed that the correlation coefficient squared (R²) value of the F_a–N curve with the same geometric and pre-tightening parameters was high, but the R² value of the F_a–N curve with all the parameters was low, indicating poor correlation and inability to meet the engineering requirements. Therefore, an equivalent structural stress model for the bolted joint was first developed based on a mechanical model with a strict mathematical definition to normalize these F_a–N curves, which considered the bolted joint loads as the input conditions and integrated the geometric and pre-tightening parameters. Subsequently, a classical beam–shell equivalent finite element model of the bolted joint was constructed. The nodal loads in the bolted connection zone were coupled with the forces and moments of the beam element nodes through finite element simulation, and the equivalent structural stress (σ_s) of the bolted joint was then obtained based on the equivalent structural stress model. Consequently, the equivalent structural stress–life (S_s–N) curve and probabilistic stress–life (P–S_s–N) curve normalized for different F_a–N curves were obtained by fitting the data of σ_s and N. Lastly, the accuracy of the fatigue life prediction method based on equivalent structural stress was verified by conducting the vibration fatigue test on the bolted joint structure of the subway antenna bracket.

本研究通过螺栓连接的拉伸-压缩疲劳试验获得了载荷振幅-寿命（Fa-N）曲线。结果表明，在相同几何参数和预紧参数下，Fa-N 曲线的相关系数平方 (R2) 值较高，但在所有参数下，Fa-N 曲线的 R2 值较低，表明相关性较差，无法满足工程要求。因此，首先基于具有严格数学定义的力学模型开发了螺栓连接的等效结构应力模型，以归一化这些 Fa-N 曲线，该模型将螺栓连接载荷视为输入条件，并整合了几何参数和预紧参数。随后，构建了螺栓连接的经典梁壳等效有限元模型。通过有限元模拟将螺栓连接区域的节点载荷与梁单元节点的力和弯矩耦合，然后根据等效结构应力模型得出螺栓连接的等效结构应力（σs）。最后，通过对地铁天线支架的螺栓连接结构进行振动疲劳试验，验证了基于等效结构应力的疲劳寿命预测方法的准确性。

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引用次数: 0

Residual stress induced granular bright facets around inclusions in high-strength steels under high-cycle fatigue 高循环疲劳下高强度钢中夹杂物周围残余应力诱发的粒状亮面

IF 5.7 2区材料科学 Q1 ENGINEERING, MECHANICAL

International Journal of Fatigue

Pub Date : 2024-09-26 DOI: 10.1016/j.ijfatigue.2024.108623

Jugan Zhang , Yongqing Wang , Chi Zhang , Jiayi Yan , Zhigang Yang , Hao Chen , Hanwei Fu , Qing Yin , Ye Liu , Yun Bai

Granular bright facets (GBFs) are frequently observed adjacent to inclusions and within fish-eye areas in the fatigue fractures of high-strength steels under very-high-cycle fatigue (VHCF), considered as a characteristic fracture feature of VHCF. Previous understanding on GBF formation emphasizes the occurrence of nanocystallization in microstructure. In this study, however, the same morphology can also be observed under high-cycle fatigue (HCF). GBF, although closer to fatigue crack initiator and experiencing more stress cycles than the peripheral part of fish-eye (PPFE), exhibits rougher surface morphology in the absence of accumulated plastic strain in microstructure, manifesting relieved crack surface wear. This indicates that the traditional theories on GBF formation for VHCF becomes invalid for HCF. The root cause for GBF formation under HCF is analyzed to be the presence of residual stress around inclusions, which reduces the contact pressure of fatigue crack surfaces inducing wear relief. Accordingly, an analytical model capable of predicting GBF thickness with the effects of HCF conditions and steel properties taken into consideration is established. The model yields accurate predictions of GBF thickness with various loading stresses and inclusion diameters, validated by experimental observations. This study provides theoretical guidance for HCF fracture analysis and fatigue life prediction.

在超高循环疲劳（VHCF）条件下的高强度钢疲劳断裂中，经常在夹杂物附近和鱼眼区域内观察到颗粒状亮面（GBF），这被认为是 VHCF 的特征性断裂特征。以往对 GBF 形成的理解强调微观结构中存在纳米结晶。但在本研究中，在高循环疲劳（HCF）条件下也能观察到相同的形态。GBF 虽然比鱼眼（PPFE）的外围部分更接近疲劳裂纹的起始点，经历的应力循环也更多，但在微观结构中没有累积塑性应变的情况下，其表面形态却更粗糙，表现为裂纹表面磨损减轻。这表明，VHCF 形成 GBF 的传统理论在 HCF 中失效。据分析，HCF 条件下 GBF 形成的根本原因是夹杂物周围存在残余应力，从而降低了疲劳裂纹表面的接触压力，导致磨损缓解。因此，考虑到 HCF 条件和钢材特性的影响，建立了一个能够预测 GBF 厚度的分析模型。该模型能准确预测不同加载应力和夹杂物直径下的 GBF 厚度，并通过实验观察进行了验证。这项研究为 HCF 断裂分析和疲劳寿命预测提供了理论指导。

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引用次数: 0

Alpha-case promotes fatigue cracks initiation from the surface in heat treated Ti-6Al-4V fabricated by Laser Powder Bed Fusion 通过激光粉末床熔融技术制造的热处理 Ti-6Al-4V 中，α-壳促使疲劳裂纹从表面萌生

IF 5.7 2区材料科学 Q1 ENGINEERING, MECHANICAL

International Journal of Fatigue

Pub Date : 2024-09-26 DOI: 10.1016/j.ijfatigue.2024.108621

Quentin Gaillard , Florian Steinhilber , Amélie Larguier , Xavier Boulnat , Jean-Yves Buffiere , Guilhem Martin , Sylvain Dancette , Sophie Cazottes , Rémy Dendievel , Christophe Desrayaud

This research investigates the effect of the formation of an oxygen-stabilised titanium alpha layer – called alpha-case at the surface – on the fatigue properties of Ti-6Al-4V (Ti64) alloy components produced by Laser Powder Bed Fusion (L-PBF). Three post processing heat treatments with different controlled atmospheres were carried out on samples with as-built surfaces to evaluate how differences in alpha-case layer thickness and hardness affect the material’s susceptibility to surface embrittlement and its overall fatigue performance. The investigation includes bulk and subsurface microstructural analysis, surface characterisation by X-ray computed tomography (XCT), and fatigue testing. Key findings show that alpha-case layers can reduce the fatigue resistance of L-PBF fabricated Ti64. The presence of a 70

\pm

3 µm thick alpha-case layer was found to promote crack initiation. This is emphasised by a higher density of initiated cracks, thus leading to a reduction in fatigue life. Conversely, thinner alpha-case layers were found to have a reduced impact on the fatigue performance, highlighting the critical role of post processing heat treatments in modulating the fatigue resistance of the material. The use of XCT to characterise the surfaces of the specimens in 3D confirms that fatigue cracks primarily initiate at surface notches, highlighting the predominance of as-built surfaces over microstructure in determining the fatigue resistance of L-PBF Ti64 components.

本研究调查了氧稳定钛α层（表面称为α-壳）的形成对通过激光粉末床融合（L-PBF）生产的 Ti-6Al-4V (Ti64) 合金部件疲劳性能的影响。我们对带有坯料表面的样品进行了三种不同控制气氛的后处理热处理，以评估α-壳层厚度和硬度的差异如何影响材料的表面脆化敏感性及其整体疲劳性能。调查包括块体和次表层微结构分析、X 射线计算机断层扫描（XCT）表面表征和疲劳测试。主要研究结果表明，α-壳层会降低 L-PBF 制成的 Ti64 的抗疲劳性能。研究发现，70±3 µm 厚的α-外壳层会促进裂纹的产生。这突出表现在萌生裂纹的密度更高，从而导致疲劳寿命缩短。相反，较薄的α-表壳层对疲劳性能的影响较小，这凸显了后处理热处理在调节材料抗疲劳性能方面的关键作用。使用 XCT 对试样表面进行三维表征证实，疲劳裂纹主要从表面凹口处开始，这突出表明在决定 L-PBF Ti64 部件的抗疲劳性时，竣工表面比微观结构更重要。

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引用次数: 0

A Monte-Carlo approach for crack initiation modeling of cast superalloys informed by crystal plasticity 根据晶体塑性建立铸造超合金裂纹起始模型的蒙特卡洛方法

IF 5.7 2区材料科学 Q1 ENGINEERING, MECHANICAL

International Journal of Fatigue

Pub Date : 2024-09-26 DOI: 10.1016/j.ijfatigue.2024.108616

Niklas Sayer , Markus Fried , Sebastian Münstermann

Crystal plasticity simulations of materials to assess the fatigue response on the microscale are becoming increasingly popular in industrial application. However, in the case of parts made from cast Ni-base superalloys, the amount of pores in a part combined with the fine spatial discretization around the pores needed due to strong mechanical gradients quickly leads to a computationally impractical number of mesh elements. In this paper we show an alternative to explicit crystal plasticity modeling of part-scale porosity by introducing a Monte-Carlo submodel that recombines the fatigue response of single pores predicted by crystal plasticity into the fatigue response of the pore agglomerate. The model can be applied in realtime due to the use of precomputed crystal plasticity results. We demonstrate that fatigue indicator parameters predicted by the Monte-Carlo submodel agree well with those predicted by explicit crystal plasticity simulations. Lastly, we apply the proposed model to study the influence of different porosity volume percentages, pore sizes and pore morphologies on the fatigue indicator parameters of a cast MAR-M247 superalloy.

对材料进行晶体塑性模拟，以评估微观尺度上的疲劳响应，在工业应用中越来越受欢迎。然而，对于由镍基超级合金铸造而成的零件，由于机械梯度较大，零件中的孔隙数量与孔隙周围所需的精细空间离散化相结合，很快就会导致网格元素数量在计算上不切实际。本文通过引入蒙特卡洛子模型，将晶体塑性预测的单个孔隙的疲劳响应重新组合为孔隙团聚的疲劳响应，展示了零件尺度孔隙率显式晶体塑性建模的替代方法。由于使用了预先计算的晶体塑性结果，该模型可以实时应用。我们证明，蒙特卡洛子模型预测的疲劳指标参数与显式晶体塑性模拟预测的参数非常吻合。最后，我们应用所提出的模型研究了不同孔隙度体积百分比、孔隙大小和孔隙形态对铸造 MAR-M247 超级合金疲劳指标参数的影响。

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引用次数: 0

High cycle fatigue behavior and strengthening mechanisms of laser powder bed fusion pure tantalum 激光粉末床熔融纯钽的高循环疲劳行为和强化机制

IF 5.7 2区材料科学 Q1 ENGINEERING, MECHANICAL

International Journal of Fatigue

Pub Date : 2024-09-26 DOI: 10.1016/j.ijfatigue.2024.108624

Rongzheng Huang , Haiqiong Xie , Lin Guo , Xu Cai , Xujing Yang , Kai Wei

The fatigue behavior and strengthening mechanisms of the laser powder bed fusion pure tantalum (LPBF-Ta), coupled with a fatigue life prediction model, were originally explored. The fatigue strength of LPBF-Ta fabricated at the optimal laser energy density (154.16 J/mm³) is 348 MPa (10⁶ cycles), showing a remarkable improvement of about 80 % and 50 % compared with that of the annealed and cold worked commercially pure tantalum, respectively. The microstructural analysis identifies that cellular structures averaging 300 nm in size contribute 438.2 MPa to strengthening, serving as the main contributor to fatigue strength. The breaching of cell walls by dislocations, along with the activation of cross-slip, ensures plasticity and ultimately enhances fatigue strength. Besides, the analysis of the defects reveals that the internal lack of fusion pore can induce the secondary fatigue crack, resulting in a region of brittle crack propagation. Furthermore, a finite life prediction model is established by originally incorporating the size of the crack source defect, and it significantly improves the prediction accuracy of the fatigue life. These results provide guidance for the development of fatigue strengthening strategies for LPBF-Ta.

最初探讨了激光粉末床熔融纯钽（LPBF-Ta）的疲劳行为和强化机制，并建立了疲劳寿命预测模型。在最佳激光能量密度（154.16 J/mm3）下制造的 LPBF-Ta 的疲劳强度为 348 MPa（106 次循环），与退火和冷加工的商业纯钽相比，分别显著提高了约 80% 和 50%。微观结构分析表明，平均尺寸为 300 nm 的细胞结构对强度的贡献为 438.2 MPa，是疲劳强度的主要贡献者。位错对细胞壁的破坏以及交叉滑移的激活确保了塑性，并最终提高了疲劳强度。此外，对缺陷的分析表明，内部缺乏融合孔隙会诱发二次疲劳裂纹，导致脆性裂纹扩展区域。此外，通过将裂纹源缺陷的尺寸考虑在内，建立了有限寿命预测模型，显著提高了疲劳寿命的预测精度。这些结果为制定 LPBF-Ta 的疲劳强化策略提供了指导。

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引用次数: 0

Fatigue damage mechanics approach to predict the end of incubation and breakthrough of leading edge protection coatings for wind turbine blades 用疲劳损伤力学方法预测风力涡轮机叶片前缘保护涂层的孵化和突破结束时间

IF 5.7 2区材料科学 Q1 ENGINEERING, MECHANICAL

International Journal of Fatigue

Pub Date : 2024-09-23 DOI: 10.1016/j.ijfatigue.2024.108617

Antonios Tempelis, Kristine Munk Jespersen, Leon Mishnaevsky Jr.

The state of the surface of the leading edge of wind turbine blades is important for optimal aerodynamic performance. Rain erosion leads to damage and roughness on the leading edge. In this study, we present an approach to predict the level of roughness of the leading edge based on fatigue damage accumulation due to impacts of rain droplets. Impact simulations of droplets on the protective coating layer are coupled with rain erosion test data and fatigue S-N curves. Fatigue damage values are then related to surface roughness levels. An approach to extract S-N curve parameters from a rain erosion test and then make predictions for other coatings based only on the output of impact simulations is presented and tested against test data. Both the end of incubation and coating breakthrough times are predicted with this approach. Stress, strain and energy density values were used as fatigue damage indicators and the respective predictions were compared to each other. It was found that the maximum principal strain gave the best predictions and matched the experimental trends.

风力涡轮机叶片前缘表面的状态对于优化空气动力性能非常重要。雨水侵蚀会导致前缘受损和粗糙。在本研究中，我们提出了一种基于雨滴撞击造成的疲劳损伤累积来预测前缘粗糙度的方法。雨滴对保护涂层的冲击模拟与雨水侵蚀测试数据和疲劳 S-N 曲线相结合。然后将疲劳损伤值与表面粗糙度水平联系起来。介绍了一种从雨水侵蚀试验中提取 S-N 曲线参数的方法，然后仅根据冲击模拟的输出结果对其他涂层进行预测，并根据试验数据进行了测试。这种方法可以预测孵育结束时间和涂层突破时间。应力、应变和能量密度值被用作疲劳损伤指标，并将各自的预测结果进行了比较。结果发现，最大主应变的预测结果最好，与实验趋势相吻合。

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引用次数: 0

Effect of microstructure rafting on deformation behaviour and crack mechanism during high-temperature low-cycle fatigue of a Ni-based single crystal superalloy 微结构筏化对镍基单晶超合金高温低循环疲劳过程中的变形行为和裂纹机制的影响

IF 5.7 2区材料科学 Q1 ENGINEERING, MECHANICAL

International Journal of Fatigue

Pub Date : 2024-09-20 DOI: 10.1016/j.ijfatigue.2024.108619

L. Tan , X.G. Yang , D.Q. Shi , W.Q. Huang , S.Q. Lyu , Y.S. Fan

The low cycle fatigue behaviours of a microstructure rafting Ni-based single crystal superalloy have been experimentally investigated at 980 ℃. Deformation of γ/γ’ phases and the corresponding dislocation configurations were investigated, highlighting rafting γ/γ’ morphology that contributes to crack initiation and propagation, as well as macro-scale accumulated plastic strain. Unlike the discrete slip lines of a virgin superalloy, intense slips developed along the parallel {111} slip plane result in crossed slip bands in the rafting superalloy. The decreased resistance of widened γ channels to dislocation movement, along with the prevention of dislocation cutting through γ’ precipitates in pre-existing dense dislocation networks, facilitates crack propagation in the γ channel in the slightly rafting superalloy. As the rafting state increases, the dislocation network loses its protective effect by reducing coherency stress and acting as a superdislocation source, which facilitates crack propagation along the γ/γ’ interface. Finally, a microstructure-based fatigue model is developed considering the reduction of deformation resistance induced by rafting. The fatigue loading control mode effect is introduced by a combination of resolved shear stress and tensile stress effects on crack initiation. The LCF life of rafting Ni-based superalloys significantly decreases under stress-controlled conditions compared to strain-controlled conditions due to the increase in cumulative plastic strain. However, the insignificant impact of the initial surface oxide layer on LCF life is revealed.

在 980 ℃ 下对一种微结构筏状镍基单晶超级合金的低循环疲劳行为进行了实验研究。研究了γ/γ'相的变形和相应的位错构型，突出显示了筏状γ/γ'形态对裂纹萌生和扩展以及宏观累积塑性应变的影响。与原始超耐热合金的离散滑移线不同，沿平行{111}滑移面发展的强烈滑移导致筏式超耐热合金中出现交叉滑移带。加宽的 γ 通道对位错运动的阻力减小，同时阻止了位错切割预先存在的密集位错网络中的γ'析出物，从而促进了轻微筏化超耐热合金中 γ 通道的裂纹扩展。随着筏化状态的增加，位错网络会失去保护作用，降低相干应力并成为超位错源，从而促进裂纹沿γ/γ'界面扩展。最后，考虑到漂移引起的变形抗力降低，建立了基于微结构的疲劳模型。疲劳加载控制模式效应是由裂纹萌生时的剪应力和拉应力效应共同作用产生的。与应变控制条件相比，由于累积塑性应变的增加，筏化镍基超合金在应力控制条件下的 LCF 寿命明显缩短。然而，初始表面氧化层对 LCF 寿命的影响并不明显。

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引用次数: 0