Design Innovation Paper

Strain Rate Calculation Approach in Environmental Fatigue Evaluations

[+] Author and Article Information
Mark A. Gray

estinghouse Electric Company LLC,
Monroeville, PA 15146
e-mail: grayma@westinghouse.com

Matthew C. Salac

Westinghouse Electric Company LLC,
Monroeville, PA 15146
e-mail: salacmc@westinghouse.com

David H. Roarty

Westinghouse Electric Company LLC,
Monroeville, PA 15146
e-mail: roartydh@westinghouse.com

E. Lyles Cranford

Westinghouse Electric Company LLC,
Monroeville, PA 15146
e-mail: cranfoel@westinghouse.com

Contributed by the Pressure Vessel and Piping Division of ASME for publication in the JOURNAL OF PRESSURE VESSEL TECHNOLOGY. Manuscript received April 6, 2011; final manuscript received November 25, 2013; published online April 28, 2014. Assoc. Editor: Somnath Chattopadhyay.

J. Pressure Vessel Technol 136(4), 045001 (Apr 28, 2014) (5 pages) Paper No: PVT-11-1095; doi: 10.1115/1.4026113 History: Received April 06, 2011; Revised November 25, 2013

Fatigue usage factor evaluations including the effects of reactor water environment have been performed in numerous nuclear plant license renewal efforts. A large number of these evaluations have used the environmental fatigue penalty factor, Fen, approach prescribed in various regulatory documents. The Fen equations require input of strain rate, but the prescribing documents do not provide methodology or criteria for the quantification of the strain rate to be input. As a result, numerous approaches have been offered and studied. This paper presents an approach used by Westinghouse to include strain rate in an automated calculation of Fen based on the modified rate approach (MRA) to integrated strain rate applications. The starting point of the approach is ASME Code Section III NB-3200 fatigue analysis. With environmental fatigue evaluations in new plant designs now emerging in ASME Code criteria, strain rate considerations remain part of the discussion. The intent of this paper is to provide further insight into this process.

Copyright © 2014 by ASME
Topics: Fatigue , Stress , Cycles
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Grahic Jump Location
Fig. 2

Stress range sign assignment logic

Grahic Jump Location
Fig. 1

TENPES linking method

Grahic Jump Location
Fig. 3

Example stress intensity time history (stress versus time)



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