Yang Dongtong, Tang Sen, Hu Yongtao, Nikitin Alexander, Wang Qingyuan, Liu Yongjie, Li Lang, He Chao, Li Yan, Xu Bo, Wang Chong
MOE Key Laboratory of Deep Earth Science and Engineering, College of Architecture and Environment, Sichuan University, Chengdu 610065, China.
School of Architecture and Civil Engineering, Chengdu University, Chengdu 610106, China.
Materials (Basel). 2022 Jul 13;15(14):4864. doi: 10.3390/ma15144864.
The very high cycle fatigue (VHCF) failure of in-service components is mainly caused by the vibration of thin-wall elements at a high frequency. In this work, a novel model of ultrasonic fatigue test was developed to test thin-wall material in bending up to VHCF with an accelerated frequency. The theoretical principle and finite element analysis were introduced for designing a sample that resonated at the frequency of 20 kHz in flexural vibration. In the advantage of the second-order flexural vibration, the gauge section of the sample was in the pure bending condition which prevented the intricate stress condition for thin-wall material as in the root of cantilever or the contact point of three points bending. Moreover, combining the constraint and the loading contact in one small section significantly reduced heating that originated from the friction at an ultrasonic frequency. Both strain gauge and deflection angle methods were applied to verify the controlling of stress amplitude. The fractography observation on Ti6Al4V samples indicated that the characterized fracture obtained from the novel model was the same as that from the conventional bending test.
服役部件的超高周疲劳（VHCF）失效主要是由薄壁元件的高频振动引起的。在这项工作中，开发了一种新型超声疲劳试验模型，用于以加速频率对薄壁材料进行弯曲直至超高周疲劳试验。介绍了设计在20kHz频率下发生弯曲振动共振的试样的理论原理和有限元分析。利用二阶弯曲振动的优势，试样的标距段处于纯弯曲状态，避免了薄壁材料在悬臂根部或三点弯曲接触点处复杂的应力状态。此外，在一个小区域内将约束和加载接触相结合，显著减少了超声频率下摩擦产生的热量。应用应变片和偏转角方法来验证应力幅值的控制。对Ti6Al4V试样的断口观察表明，从新型模型获得的特征断裂与传统弯曲试验的相同。
