Quantified evaluation of the influence of testing frequency on the fatigue behaviour of unalloyed steels for implementation in resource-efficient fatigue life prediction methods

到目前为止，凯撒斯劳滕应用科学与材料测试系(WWHK)开发的疲劳寿命预测方法(LPV)仅限于LCF(低周疲劳)和HCF(高周疲劳)之间的过渡以及HCF范围(约。3到5x10^5个周期)。这在一定程度上导致了有关LPV潜力开发的科学问题，这就是为什么要在本研究项目中进行系统调查的原因。之所以还不可能将程序和方法扩展到VHCF(甚高循环疲劳)范围，是因为WWHK没有必要的测试基础设施，无法在合理的时间框架内实现循环次数达到10^8。通过批准大规模设备申请，采购了一台共振试验机并投入运行，这使得也可以在技术上合理的时间框架内实现VHCF制度的循环次数。这里必须考虑两个因素。相关的损伤机制可以从HCF变化到VHCF范围。例如，裂纹起始点移动到缺陷区域的体积中，如夹杂物和析出物，特别是在高强度材料条件下。对于延性材料，在激活持续滑移带的临界阈值以下也可以检测到损伤发展，这可以归因于高循环次数和相关的积累过程。出于这个原因，有必要检查到目前为止使用的测量技术中的哪一种也可以用于高循环状态。变形速率对单周损伤发展有显著影响。必须能够量化频率和损伤贡献以及由此产生的疲劳寿命之间的关系，从而使其可用于LPV。因此，其目的是开发用于VHCF区域的LPV，并用数学方法实现对变形速率和与载荷相关的机制的影响，并通过实验验证预测质量。在工作计划范围内，扩展西澳大利亚西部大学LPV的全面机械测试将得到TU Dortmund University材料测试工程(WPT)教席的详细微结构表征的支持。钢SAE1045(C45E，1.0503)将被用作测试材料，因为已完成的调查已经提供了测试频率为5赫兹的数据库。因此，在这个研究项目中，可以重点关注60至260赫兹的频率范围，从而可以重点研究共振测试系统的使用。

The fatigue life prediction methods (LPV) developed at the department of Materials Science and Materials Testing (WWHK) at the University of Applied Sciences Kaiserslautern have so far been limited to the transition between LCF (Low Cycle Fatigue) and HCF (High Cycle Fatigue) as well as to the HCF range (approx. 3 to 5x10^5 cycles). This has led in part to scientific questions regarding the exploitation of the potential of LPV, which is why systematic investigations are to be carried out in this research project. The reason why it has not yet been possible to extend the procedures and methods to the VHCF (Very High Cycle Fatigue) range is that the WWHK did not have the necessary testing infrastructure to achieve cycle numbers up to 10^8 within a reasonable time frame. Through the approval of the large-scale equipment application, a resonance testing machine was procured and taken into operation, which makes it possible that cycle numbers in the VHCF regime can also be achieved in a technically justifiable time frame. Two factors must be considered here. Relevant damage mechanisms can change from the HCF to the VHCF range. For example, crack initiation points shift into the volume in the area of defects, such as inclusions and precipitates, especially in the case of high-strength material conditions. In the case of ductile materials, damage development can also be detected below the critical threshold value for the activation of persistent slip bands, which can be attributed to the high cycle numbers and the associated accumulation processes. For this reason, it is necessary to check which of the measurement techniques used so far can also be used for the high cycle regime. The deformation rate has a significant influence on the damage development per cycle. It is essential that the relationship between frequency and damage contribution and the resulting fatigue life can be quantified and thus made usable for LPV. The aim is therefore to develop LPV for the use in the VHCF regime and to implement influences regarding deformation rate and load-related mechanisms in mathematical approaches and to validate the prediction quality through experiments. Within the work program, the comprehensive mechanical tests to extend the LPV at WWHK will be supported by detailed microstructural characterization at the Chair of Materials Test Engineering (WPT) at TU Dortmund University. The steel SAE 1045 (C45E, 1.0503) is to be used as test material, since a database for the test frequency 5 Hz is already available from completed investigations. Thus, within this research project, the frequency range of 60 to 260 Hz and thus the use of the resonance test system can be focused on.