Investigation of the cyclic behavior of carbon steels at different control modes and strain rates

碳钢在不同控制模式和应变率下的循环行为研究

• 批准号: 528786920
• 负责人: Dr.-Ing. Marcus Klein
• 金额: --
• 依托单位: Fachgebiet und Institut für Werkstoffkunde
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/528786920?language=en
• 关键词: Investigation; cyclic; behavior; carbon; steels

The aim of the research project is to extend the state of research on the cyclic behavior of hypoeutectoid carbon steels under different control types and strain rates. Two equally important sub-objectives are being pursued: On the one hand, quantitative models describing the influences of strain rate and control type are improved so that results obtained on ultrasonic fatigue testing equipment can be used to infer force-controlled material behavior at low or moderate frequencies (less than 1 kHz). On the other hand, the mechanism-based understanding of VHCF behavior is improved. For this purpose, the differences between the mechanisms in conventional testing and the mechanisms in ultrasonic testing are characterized across scales. In this project, displacement- and stress-controlled tests on conventional testing machines and displacement-controlled tests on ultrasonic fatigue testing machines will be performed on two heat treatment batches each of 42CrMo4 and 50CrMo4. Based on the resulting data set, the materials scientific method for converting the results of force- and displacement-controlled tests that has been developed in preceding research is evaluated. If successful, validation of the algorithm will allow inference from ultrasonic fatigue testing equipment results to stress-controlled material behavior at high frequencies. Further, the influence of strain rate on fatigue behavior is inferred directly from the results of displacement-controlled tests on conventional testing machines as well as ultrasonic fatigue testing equipment. Compared to the current state of research, this is advantageous because the disturbance variable ‘control type’ is eliminated and thus the uncertainty of the statement is significantly reduced. In parallel to the vibration tests, extensive materials analytical investigations such as (FIB-) SEM, XPS, nanoindentation and EBSD investigations are carried out. These investigations will be adjusted to help elucidate the differences in mechanisms in the ultrasonic and conventional fatigue tests. Improved understanding of the differences in mechanisms will bring improved understanding of mechanisms in general. Emphasis is placed on the following questions: (Why) is the evolution of microstructure in ultrasonic testing different from the evolution of microstructure in conventional testing? (Why) do experiments performed at different frequencies differ with respect to the introduction of oxygen and nitrogen and with respect to the diffusion of carbon? How does the strain rate (variable in single fatigue tests due to the sinusoidal signal) affect the cyclic material behavior? To what mechanisms, if any, are differences in the lifetime and in the development of the microstructure attributed?

该研究项目的目的是扩展亚共析碳钢在不同控制类型和应变速率下的循环行为的研究状况。 两个同样重要的子目标正在追求：一方面，定量模型描述的应变率和控制类型的影响进行了改进，使超声波疲劳试验设备上获得的结果可以用来推断力控制的材料行为在低或中等频率（小于1 kHz）。另一方面，提高了对VHCF行为的基于机制的理解。为此目的，在常规测试和超声波测试的机制之间的差异，其特征在于跨尺度。在本项目中，将对42 CrMo 4和50 CrMo 4各两个热处理批次进行常规试验机上的位移和应力控制试验以及超声波疲劳试验机上的位移控制试验。基于所得到的数据集，材料的科学方法转换的力和位移控制的测试，已经在以前的研究中开发的结果进行了评估。如果成功，算法的验证将允许从超声疲劳测试设备结果推断高频下的应力控制材料行为。此外，应变率对疲劳性能的影响是直接从传统的试验机以及超声波疲劳试验设备上的位移控制试验的结果推断出来的。 与目前的研究状况相比，这是有利的，因为干扰变量“控制类型”被消除，从而显着降低了声明的不确定性。在振动测试的同时，进行了广泛的材料分析研究，如（FIB-）SEM，XPS，纳米压痕和EBSD研究。这些调查将进行调整，以帮助阐明在超声波和传统的疲劳试验的机制的差异。更好地理解机制的差异将有助于更好地理解一般机制。重点讨论了以下问题：（为什么）超声检测中的微观组织演变不同于常规检测中的微观组织演变？(Why)在不同频率下进行的实验在氧和氮的引入方面以及在碳的扩散方面是否不同？ 应变率（由于正弦信号，在单次疲劳测试中可变）如何影响循环材料行为？寿命和微观结构发展的差异归因于什么机制（如果有的话）？