Influence of testing frequency on the fatigue behavior in the HCF/VHCF-range of the magnesium alloy AZ31

试验频率对镁合金AZ31在HCF/VHCF范围内疲劳行为的影响

• 批准号: 452852691
• 负责人: Professorin Dr.-Ing. Martina Zimmermann
• 金额: --
• 依托单位: Institut für Werkstoffwissenschaft
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2020
• 资助国家: 德国
• 起止时间: 2019-12-31 至 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/452852691?language=en
• 关键词: Influence; testing; frequency; fatigue; behavior

Due to their high strength and low density, magnesium alloys are an attractive material, which is increasingly used in the automotive and aerospace industries. Since components in these application areas are often exposed to cyclical loading, fatigue behavior is of importance with regard to the possible uses and limitations of an alloy class. In wrought magnesium alloys, which, in contrast to cast alloys, are to a great extent free of coarse defects, the deformation behavior is primarily determined by the hexagonal lattice structure and hence plays a decisive role in the fatigue behavior. In addition to the dislocation glide, the formation of deformation twins is of particular importance . Both mechanisms can cause crack initiation. Which one of them dominates during fatigue damage accumulation depends on various factors, such as the load amplitude. At high load amplitudes, cracks tend to occur in twins, whereas at low amplitudes, crack initiation takes place in slip bands.In recent years, increasing research activities have dealt with the properties under cyclic loading and have investigated various influencing factors, such as the texture of the microstructure, the atmosphere and the influence of the test frequency. However, especially regarding likely frequency influences, there is a mixed picture regarding the fatigue behavior. So far, phenomenological descriptions of the results have primarily been found in the literature. Furthermore, rarely any results can be found on the influence of frequencies above 100 Hz. But especially in the course of the increased investigations regarding the VHCF range, corresponding testing machines were also developed, such as the ultrasonic fatigue testing technique, operating at a frequency of 20 kHz.In the proposed project, the influence of the test frequency on the fatigue behavior of the magnesium wrought alloy AZ31 (Mg-Al-Zn) in the HCF / VCHF range will be investigated at frequencies of 100 Hz and 20 kHz. A special focus of the investigation will be on the deformation mechanisms that contribute to crack initiation. As a further influencing factor on the fatigue behavior of AZ alloys, a pronounced transient behavior and a significant Bauschinger effect could be observed. These aspects are also addressed in connection with the displacement controlled ultrasonic testing system as part of the planned project.

由于其高强度和低密度，镁合金是一种有吸引力的材料，越来越多地用于汽车和航空航天工业。由于这些应用领域中的部件经常受到循环载荷的影响，因此疲劳性能对于合金类别的可能用途和限制非常重要。在锻造镁合金中，与铸造合金相比，锻造镁合金在很大程度上没有粗糙缺陷，变形行为主要由六方晶格结构决定，因此在疲劳行为中起决定性作用。除了位错滑移外，形变孪晶的形成也是特别重要的。这两种机制都可能导致裂纹萌生。在疲劳损伤累积过程中，它们中的哪一个占主导地位取决于各种因素，如载荷幅值。在高载荷幅值下，裂纹倾向于在孪晶中萌生，而在低载荷幅值下，裂纹萌生发生在滑移带中。近年来，越来越多的研究活动涉及循环载荷下的性能，并调查了各种影响因素，如微观组织的织构、气氛和试验频率的影响。然而，特别是关于可能的频率影响，关于疲劳行为存在混合情况。到目前为止，对结果的现象学描述主要见于文献中。此外，很少有任何结果可以发现的影响，频率高于100赫兹。但特别是在对VHCF范围的研究不断增加的过程中，也开发了相应的测试机器，例如在20 kHz频率下运行的超声波疲劳测试技术。在拟议的项目中，试验频率对变形镁合金AZ 31疲劳性能的影响将在100 Hz和20 kHz的频率下研究HCF / VCHF范围内的（Mg-Al-Zn）。调查的一个特别重点将是有助于裂纹萌生的变形机制。作为AZ合金疲劳行为的进一步影响因素，可以观察到显著的瞬态行为和显著的Bauschinger效应。作为计划项目的一部分，位移控制超声波检测系统也涉及这些方面。