The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
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Realistic Artificial Flaws for NDE Qualification – A Novel Manufacturing Method Based on Thermal Fatigue

Mika Kemppainen

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Department of Mechanical Engineering for public examination and debate in Auditorium K216 at Helsinki University of Technology (Espoo, Finland) on the 14th of July, 2006, at 12 noon.

Overview in PDF format (ISBN 951-22-8263-1)   [30693 KB]
Dissertation is also available in print (ISBN 951-22-8262-3)

Abstract

Part of regular maintenance of power plants is periodically performed non-destructive in-service inspections (ISIs). The reliability of the ISI is based on the performance of the applied non-destructive inspection procedures and capability of the inspection personnel verified by qualification procedures. In qualification representative flaws are used for simulating postulated or actual service-induced flaws. However, different artificial flaw manufacturing procedures used so far have shown certain limitations in producing representative flaws including variations in reproducibility, introduction of artefacts and non-representative flaw characteristics. Consequently, better artificial flaw manufacturing methods are needed.

The aim of this study was to fulfil the need by developing an artificial flaw manufacturing method. The method would allow production of realistic flaws with controllable size, location and characteristics and without additional disturbances, hence, avoiding the current problems.

A controlled flaw manufacturing method based on the thermal fatigue damage mechanism was developed. The produced flaws and their characteristics were extensively examined to evaluate their representativeness by means of non-destructive and destructive testing methods. The developed method produces natural thermal fatigue cracks with realistic characteristics, e.g., opening, tortuous propagation, condition of residual stresses, and roughness of the fracture surface.

The method is applicable for different materials and components. The produced flaws were compared to service-induced flaws by experimental measurements and by referring the open literature. Produced flaws are judged to be realistic flaws simulating essential characteristics of service-induced flaws and giving realistic NDE response. The developed method overcomes problems related to previous flaw manufacturing methods including, among others, non-representative flaw characteristics, difficulties in applicability to ready-made components and induced artifacts or disturbances.

This thesis consists of an overview and of the following 8 publications:

  1. Elfving, K., Hänninen, H., Kemppainen, M., Saarinen, P. and Virkkunen, I., 2004. Method for Producing Defects and Tensile Residual Stresses. United States Patent, US6723185 (B1), 20 April, 2004. © 2004 by authors.
  2. Kemppainen, M., Virkkunen, I., Pitkänen, J., Paussu, R. and Hänninen, H., 2003. Realistic Cracks for In-Service Inspection Qualification Mock-ups. The e-Journal of Nondestructive Testing & Ultrasonics, ISSN: 1435-4934. Vol. 8, no. 3, March 2003. pp. 1-8. © 2003 NDT.net. By permission.
  3. Kemppainen, M., Virkkunen, I., Pitkänen, J., Paussu, R. and Hänninen, H., 2003. Comparison of Realistic Artificial Cracks and In-Service Cracks. The e-Journal of Nondestructive Testing & Ultrasonics, ISSN: 1435-4934. Vol. 8, no. 3, March 2003. pp. 1-6. © 2003 NDT.net. By permission.
  4. Kemppainen, M., Virkkunen, I., Pitkänen, J., Paussu, R. and Hänninen, H., 2003. Advanced Flaw Production Method for In-Service Inspection Qualification Mock-ups. Nuclear Engineering and Design, 224. pp. 105-117. © 2003 Elsevier Science. By permission.
  5. Pitkänen, J., Kemppainen, M. and Virkkunen, I., 2003. Ultrasonic Study of Crack under a Dynamic Thermal Load. Proceedings of the Review of Progress in Quantitative Nondestructive Evaluation Conference, Vol. 23, 27 July - 1 August 2003, Green Bay, Wisconsin, USA. Thompson, D. O. and Chimenti, D. E., eds., American Institute of Physics Conference Proceedings, Vol. 700, 2004. pp. 1582-1586. 0-7354-0173-X/04. © 2003 American Institute of Physics. By permission.
  6. Kemppainen, M., Pitkänen, J., Virkkunen, I. and Hänninen, H., 2003. Advanced Flaw Manufacturing and Crack Growth Control. Proceedings of the Review of Progress in Quantitative Nondestructive Evaluation Conference, Vol. 23, 27 July - 1 August 2003, Green Bay, Wisconsin, USA. Thompson, D. O. and Chimenti, D. E., eds., American Institute of Physics Conference Proceedings, Vol. 700, 2004. pp. 1272-1279. 0-7354-0173-X/04. © 2003 American Institute of Physics. By permission.
  7. Virkkunen, I., Kemppainen, M., Pitkänen, J. and Hänninen, H., 2003. Effect of Thermal Stresses along Crack Surface on Ultrasonic Response. Proceedings of the Review of Progress in Quantitative Nondestructive Evaluation Conference, Vol. 23, 27 July - 1 August 2003, Green Bay, Wisconsin, USA. Thompson, D. O. and Chimenti, D. E., eds., American Institute of Physics Conference Proceedings, Vol. 700, 2004. pp. 1224-1231. 0-7354-0173-X/04. © 2003 American Institute of Physics. By permission.
  8. Kemppainen, M., Virkkunen, I., Pitkänen, J., Hukkanen, K. and Hänninen, H., 2003. Production of Realistic Artificial Flaw in Inconel 600 Safe-end. Proceedings of the Conference on Vessel Penetration Inspection, Crack Growth and Repair, sponsored by USNRC and Argonne National Laboratory, 29 September - 2 October 2003, Washington D.C., Gaithersburg, USA. NUREG/CP-0191, Vol. 1, pp. 51-60 and Vol. 2, pp. 181-196 (presentation slides). © 2003 by authors.

Keywords: thermal fatigue, artificial flaw, flaw manufacturing method, non-destructive evaluation qualification, performance demonstration, ultrasonic testing

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© 2006 Helsinki University of Technology

Last update 2011-05-26