DIGITAL IMAGING ANALYSIS OF MICROSTRUCTURES AS A TOOL TO IDENTIFY LOCAL PLASTIC DEFORMATION

摘要

This paper presents a methodology to detect plastic deformation at the micro level. The analysis is based on the statistical data describing the morphological and crystallographic textures of a sample microstructure. This data was obtained from optical microscopy using a digital imaging analysis. The important parameters necessary to describe the microstructure were identified as the grain-size and grain-orientation distributions. A change in the weighted product of these two parameters, the grain size as the area of grains and the grain orientation as the moment of inertia of grains, can represent a measure to identify plastic deformation on a small area. A demonstration of its applicability was performed on a real object as part of a ruptured-pipe-failure analysis in a thermal-power-plant boiler. The presented analysis leads to a fast identification of the local plastic deformation and, in the case of periodical analysis of the same sample, it can even be used as a measure to identify creeping.