EVALUATION OF CRACKING BEHAVIOR OF PIPELINE X70 STEEL FROM DWTT BROKEN SPECIMENS

1 STRNADEL Bohumír
Co-authors:
1 HASEGAWA Kunio 1 SKALNÝ Pavel
Institution:
1 Center of Advanced Innovation Technologies - VSB-Technical University of Ostrava, Ostrava, Czech Republic, EU, bohumir.strnadel@vsb.cz, kunioh@kzh.biglobe.ne.jp, pavel.skalny@vsb.cz
Conference:
24th International Conference on Metallurgy and Materials, Hotel Voronez I, Brno, Czech Republic, EU, June 3rd - 5th 2015
Proceedings:
Proceedings 24th International Conference on Metallurgy and Materials
Pages:
573-577
ISBN:
978-80-87294-58-1
ISSN:
2694-9296
Published:
12th January 2015
Proceedings of the conference were published in Web of Science and Scopus.
Metrics:
55 views / 17 downloads
Abstract

Fracture surfaces of X70 steel DWTT broken samples are analyzed using statistical methods and fractal concepts. Applying self-affine fracture profile construction method and the first return probability method the Hurst exponent of ductile fracture areas has been found. Increasing percentage of ductile fracture on broken DWTT sample surface the Hurst exponent grows. Modeling of the DWTT fracture surface area by triangle net the statistical distribution of deviations between normal vectors of two neighboring elementary triangles has been discovered. This distribution behaves as Gaussian mixture. The mean value of deviation angles is lower for ductile than for brittle fracture regions whereas scatter of deviation angles are about the same for the both modes of cracking. Calculated fracture surface map of ductile fracture probability highly corresponds to real distribution of ductile and brittle fracture areas on fracture surface of the broken sample. Newly developed statistical methods of the fracture surface treatment of DWTT broken samples is useful tool for objective evaluation of ductile fracture percentage.

Keywords: X70 steel, DWTT samples, fracture surface, Hurst exponent, statistical analysis

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