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Ultrasonic fatigue testing under multiaxial loading on a railway steel
International Journal of Fatigue ( IF 6 ) Pub Date : 2020-07-01 , DOI: 10.1016/j.ijfatigue.2020.105581
Pedro R. da Costa , Henrique Soares , Luís Reis , Manuel Freitas

Abstract Ultrasonic fatigue testing is a relative recent fatigue study methodology that applies resonant principles for the induction of stress cycles in a specific designed material specimen. Such experimental method can apply fatigue damage at high frequencies, most commonly at 20 kHz. It was created with the main purpose of studying material fatigue life in the Very High Cycle Fatigue regime between 10E07 and 10E09 cycles with a higher performance of time and energy wise in comparison to conventional servo-hydraulic machines. In this study an ultrasonic fatigue testing machine was used in order carry out multiaxial tension/torsion fatigue tests at a frequency of 20 kHz. The main objective was to reach a reliable multiaxial fatigue testing method, by modifying only the specimen, with the ability to choose the shear-axial stress ratio. The improved design of the testing method was focused in innovative design specimen by conducting both numerical and experimental analysis. Thermographic imaging, laser displacement measurements, and the application of rosette strain gauges to the main stress region of the specimen were carried out in order to validate the new improved design concepts. These strain and displacement results were compared with the ones obtained by finite element and a good agreement was achieved. A first series of fatigue tests were carried out intension/torsion multiaxial fatigue and the results are discussed in order to understand the feasibility of multiaxial fatigue tests at ultrasonic frequencies.

中文翻译:

铁路钢多轴载荷超声疲劳试验

摘要 超声疲劳试验是一种相对较新的疲劳研究方法,它应用共振原理在特定设计的材料试样中诱导应力循环。这种实验方法可以在高频下应用疲劳损伤,最常见的是在 20 kHz 下。创建它的主要目的是研究 10E07 和 10E09 周期之间极高周疲劳状态下的材料疲劳寿命,与传统伺服液压机器相比,它具有更高的时间和能量性能。在这项研究中,使用超声波疲劳试验机以 20 kHz 的频率进行多轴拉伸/扭转疲劳试验。主要目标是通过仅修改样本来实现可靠的多轴疲劳测试方法,并能够选择剪切轴应力比。通过进行数值和实验分析,测试方法的改进设计集中在创新设计样本上。进行了热成像、激光位移测量以及将应变片应用于试样的主要应力区域,以验证新的改进设计概念。这些应变和位移结果与有限元获得的结果进行了比较,并取得了良好的一致性。进行了第一系列疲劳试验,强度/扭转多轴疲劳,并讨论了结果,以了解多轴疲劳试验在超声频率下的可行性。进行了激光位移测量,并在试样的主要应力区域应用了花环应变片,以验证新的改进设计概念。这些应变和位移结果与有限元获得的结果进行了比较,并取得了良好的一致性。进行了第一系列疲劳试验,强度/扭转多轴疲劳,并讨论了结果,以了解多轴疲劳试验在超声频率下的可行性。进行了激光位移测量,并在试样的主要应力区域应用了玫瑰花形应变片,以验证新的改进设计概念。这些应变和位移结果与有限元获得的结果进行了比较,并取得了良好的一致性。进行了第一系列疲劳试验,强度/扭转多轴疲劳,并讨论了结果,以了解多轴疲劳试验在超声频率下的可行性。
更新日期:2020-07-01
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