Využití fraktální analýzy při hodnocení lomových ploch DWTT těles

Abstract

Steels for gas and oil pipelines must represent specific mechanical properties in low temperatures, in which they are sensitive to brittle fracture. In case drop weight tear test (DWTT) application of these steels is assessed by percentage of ductile fracture on fracture surface of DWTT specimens. Therefore the essential step of this test is the proper evaluation of percentage of ductile fracture on fracture surface. There are a lot of standards which are describing the process of this test and analyzing results, for example ASTM, GOST, CSN. Obtained results are dependent on the standard, which was used and subjective view of expert, who tested specimens. The goal of this work is to examine the fracture surfaces of the DWTT specimens by using fractal analysis. To achieve this goal was made an algorithm, which determinate fractal dimension of surfaces. Evaluation was made on DWTT specimens, fabricated by steel X52. Obtained results were compared with results by analysis according to standards. Also was founded correlation between fractal dimension of fracture surfaces and percentage of ductile component of fracture on fracture surface.