双轴弯曲超声疲劳实验方法  

Development of Ultrasonic Fatigue Test Method on Biaxial Bending

作　　者：汪歆彧 阳东彤 唐森 黄北海 徐波[1,2] 王宠[1,2] 王清远[1,2,3] Xinyu Wang;Dongtong Yang;Sen Tang;Beihai Huang;Bo Xu;Chong Wang;Qingyuan Wang(Failure Mechanics and Engineering Disaster Prevention Key Laboratory of Sichuan Province,Sichuan University,Chengdu,610065;Key Laboratory of Deep Underground Science and Engineering,Sichuan University,Chengdu,610065;School of Mechanical Engineering,Chengdu University,Chengdu,610106)

机构地区：[1]四川大学灾变力学与工程防灾四川省重点实验室,成都610065 [2]四川大学深地科学与工程教育省重点实验室,成都610065 [3]成都大学机械工程学院力学系,成都610106

出　　处：《固体力学学报》2024年第6期724-734,共11页Chinese Journal of Solid Mechanics

摘　　要：面向航空发动机叶片等薄壁材料长寿命耐久性测试需求,本文提出了一种适合双轴弯曲疲劳试验的超声加速疲劳实验方法.从简谐振动原理出发设计了固有频率为20 kHz的四阶和三阶弯曲垂直叠加TC4十字双轴超声疲劳试样.通过应变片测量对该方法的振动频率和振动模态进行了测定,并结合激光传感器对超声弯曲疲劳的应力进行了标定.开展了双轴弯曲加载下的超高周疲劳性能验证性实验.通过对不同加载条件下的S-N曲线、裂纹扩展路径和断口形貌分析,揭示了双轴弯曲超高周疲劳失效破坏行为的特征.结果表明,TC4钛合金在超高周阶段仍然呈持续下降趋势.由于梯度应力分布,双轴弯曲疲劳寿命明显高于单轴超声疲劳寿命.裂纹扩展行为与常规双轴疲劳时相似,均形成“H”型或“Y”型裂纹.断口分析表明裂纹萌生区呈现出大面积的脆性断裂特征,形态主要表现为面片和由面片合并形成的撕裂脊.双轴弯曲疲劳时出现的板条状刻面特征与航空发动机多轴疲劳失效实际案例特征相同,说明该方法有效的再现了实际工况下的多轴弯曲疲劳载荷加载.Thin-walled metal components frequently undergo multiaxial bending fatigue during operation,necessitating an experimental method to replicate loading conditions for investigating material properties.In this study,a novel biaxial bending test method using ultrasonic fatigue technology was proposed.The design involved a cruciform TC4 titanium alloy specimen tuned to a natural frequency of 20 kHz based on the principle of harmonic vibration,featuring vertically superimposed fourth-order and third-order bending modes to ensure the maximum stress region remained in the test section.Arc transitions were utilized in other regions to mitigate stress concentration.Finite element simulations and strain gauge tests were conducted to calibrate stress amplitudes in the specimens.Analysis of S-N curves,crack propagation paths,and fracture morphologies revealed the failure mechanisms of biaxial bending fatigue in the very high cycle regime under varied loading conditions.It was found that TC4 titanium alloy exhibited no fatigue limit in the very high cycle regime,showing a continuous downward trend.Owing to gradient stress distribution,biaxial bending fatigue demonstrated significantly longer fatigue life compared to uniaxial ultrasonic fatigue.Meanwhile,crack propagation behavior resembled conventional biaxial fatigue,producing H-shaped or Y-shaped cracks.Fracture surfaces exhibited a brittle characteristic in a large area of the crack initiation zone,with morphology primarily characterized by facets and tearing ridges formed through facet coalescence.In contrast to uniaxial bending fatigue,the facets in biaxial bending showed a batten pattern akin to multiaxial fatigue failure.

关 键 词：超高周疲劳 双轴疲劳 弯曲疲劳 裂纹萌生 裂纹路径 

分 类 号：V231.95[航空宇航科学与技术—航空宇航推进理论与工程]