SGER: A Novel Method for In-Situ Fatigue Experiments

这是一项高风险的小额拨款，用于探索性研究（SGER），在透射电子显微镜下进行原位疲劳实验。经典的金属疲劳现象尚不清楚，部分原因是反向变形的位错动力学尚未表征。在循环变形过程中，只有有限的成功是直接观察位错，例如在透射电子显微镜下的原位循环或反向塑性变形试验中观察到的。当施加的拉伸或剪切应力相反时，问题与薄箔的屈曲有关。分析表明，在垂直方向上交替施加拉应力可以扭转位错的运动，避免了箔的屈曲。为了在透射电子显微镜下进行这种原位机械测试，首席研究员设计了一种新的试样夹。将进行一系列的原位反变形疲劳试验，并将为反变形现象提供新的见解。金属合金的疲劳会导致工业机械、运输系统和相关基础设施领域中使用的金属合金部件的意外失效。这项研究应该能增进对这一领域的理解。＊＊＊

9416775 Kassner This is a high-risk, small grant for exploratory research (SGER) to perform in-situ fatigue experiments in the transmission electron microscope. The classic metal-fatigue phenomenon is poorly understood, partially because the dislocation dynamics of reversed deformation has not been characterized. Only limited success has been achieved with direct observation of dislocations during cyclic deformation, such as observed in in-situ cyclic or reversed plastic deformation tests in the transmission electron microscope. The problem is associated with buckling of thin foils when the applied tensile or shear stress is reversed. Analysis shows that dislocation movement can be reversed by tensile stressing in alternating perpendicular directions, and buckling of the foil can be avoided. A new specimen holder has been designed by the principal investigator for performing such mechanical tests in-situ in the transmission electron microscope. A series of in-situ reversed deformation fatigue tests will be run and should provide new insights into reversed deformation phenomena. %%% Fatigue of metal alloys can lead to unanticipated failure of metal alloy components used in industrial machinery, transportation systems, and related infrastructure areas. This research should provide improved understanding in this field. ***