Integrity Assessment of Power-Plant Structural Elements Using Fracture Mechanics

Abstract:

The research work aimed to present the usability of the cracked round bar (CRB) specimen type for the determination of the linear-elastic plain strain fracture toughness values (K_Ic or K_Q) on steels; and to demonstrate the applicability of the testing results for the reliability assessment of structural elements having cracks or crack like defects. Micro-alloyed structural steel and heat resistant steel were tested at elevated temperatures, at 260 °C and 410 °C, respectively, using small-sized specimens with small diameters. Four different equations were used for the evaluation of the tests, and the determined fracture toughness values were compared with one another. Reliability assessment calculations were realised on two structural element models, critical crack sizes and safety factors were determined for all cases.

• Periodical: Materials Science Forum (Volume 729)
• Pages: 103-108
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.729.103
• Online since: November 2012
• Authors: János Lukács
• Keywords: Crack Round Bar (CRB) Specimen, Elevated Temperature, Linear-Elastic Plane-Strain Fracture Toughness, Reliability Assessment

References

[1] ASTM E 399, Standard Test Method for Linear-Elastic Plane-Strain Fracture Toughness KIc of Metallic Materials, (2006).

DOI: 10.1520/e0399-08

[2] S. K. Nath, U. Kr. Das, Effect of microstructure and notches on the fracture toughness of medium carbon steel, Journal of Naval Architecture and Marine Engineering. 3 (2006) 15-22.

DOI: 10.3329/jname.v3i1.925

[3] M. Haager, G. Pinter, R. W. Lang, Ranking of PE-HD pipe grades by fatigue crack growth performance, Plastics Pipes XIII, Washington, 2006. pp.1-11.

DOI: 10.1179/174328905x29758

[4] Sz. E. Kovcsik, E. M. Morozov, Kharakterisztiki kratkovremennojj treshhinosztojjkoszti materialov i metodü ikh opredelenija, Kiev, Naukova Dumka, (1988).

[5] O. N. Romaniv, G. N. Nikiforcsin, Mekhanika korrozionnovo razrushenija konsztrukcionnükh szplavov, Moszkva, Metallurgija, (1986).

[6] F. Nilsson, Fracture Mechanics – from Theory to Applications, KTH Högskoletryckeriet, Stockholm, (1999).

[7] P. Romvári, L. Tóth, J. Lukács, Rechnergestützte Lebensdauerabschätzung unter Anwendung der Bruchmechanik, Neue Hütte. 30 (1985) 103-105.

[8] J. Lukács, Effect of Reliability of Crack Propagation Measurement on the Assessment of Life-Times for Structural Elements Having Flaws, The International Journal of Pressure Vessels and Piping. 55 (1993) 261-268.

DOI: 10.1016/0308-0161(93)90034-q

[9] E. Y. Lim et al., Approximate influence functions for part-circumferential interior surface cracks in pipes, in: ASTM STP 791, American Society for Testing and Materials, 1983, pp. I281-I296.

[10] J. C. Jr. Newman, I. S. Raju, Stress intensity factors for internal surface cracks in cylindrical pressure vessels, Journal of Pressure Vessel Technology, Transactions of the ASME. 102 (1980) 342-346.

DOI: 10.1115/1.3263343

[11] H. P. Keller (Ed. ), Bruchmechanik druckbeanspruchter Bauteile, Carl Hanser Verlag/Verlag TÜV Rheinland, München-Wien-Hauser-Köln, (1990).

DOI: 10.1002/mawe.19920230309

[12] J. C. Jr. Newman, I. S. Raju, Stress intensity factors for internal and external surface cracks in cylindrical vessels, Journal of Pressure Vessel Technology, Transactions of the ASME. 104 (1982) 293-298.

DOI: 10.1115/1.3264220