THE QUANTITAVE ANALYSIS OF FRACTURE USING THE CONFOCAL LASER SCANNING MICROSCOPY

The study of the parts fracture surface is the basic and important part of determination of the fracture process causes and chronology. The quality and objectivity of fractographic analysis depends largely on the effectiveness of tools used for the fracture study. The main disadvantage of traditional methods used in this area is the two-dimensionality of images that greatly complicates the quantitative analysis of the fracture surface. In this context, the method of confocal laser scanning microscopy (CLSM) is one of the prospective techniques providing a high-quality measuring accuracy of the objects surface geometry in three-dimensional space, a wide scanning range along the vertical axis and the necessary depth of field. Moreover, CLSM method does not require the electrical conductivity and special specimen surface preparation, as well as the presence of vacuum.

In this study, the authors developed and tested the technique of exposure and further impact specimen fractures analysis using the CLSM. To be the subject of research, the authors selected the fractures of fully brittle and fully ductile fracture surfaces of 20 grade steel, the fractures of which were obtained during impact tests of the specimens hold at the temperatures of -196°C and +150°C, respectively. During the research, the optimal amplification, the lens type, the scanning pitch and the image noise filter were determined. The research showed that to measure the fracture surface ductility it is possible to use such parameter as the characteristic fracture surface area Sr, which value changes significantly while going from ductile to brittle fracture. The research showed that the CLSM application allows converting the qualitative analysis of metal products fracture into quantitative one improving the objectivity and accuracy of fractographic analysis.