Detection of Micro Cracks in a Model Structure under Thermal Transient Loading by Micro Indentation Test

摘要

The micro hardness testing machine was applied to detect micro cracks on the model vessel under cyclic thermal transient with creep and fatigue. Micro hardness by the micro indentation test was measured along thickness of the model vessel. The micro hardness value decreased in the region of intergranular cracks from surface of the vessel and increased near the crack tip in comparison with no crack region. The decrease of micro hardness value in the crack region corresponded to creep-fatigue damage D≥1 under the cyclic thermal transient, where the creep--fatigue damage was calculated by the linear damage fraction rule. The micro indentation method was applicable to the detection of micro cracks.