0
Research Papers: Design and Analysis

Crack Growth Under High-Cycle Thermal Fatigue Loading: Effects of Stress Gradient and Relaxation in a Crack Network

[+] Author and Article Information
Masayuki Kamaya

 Institute of Nuclear Safety System, Inc., 64 Sata, Mihama-cho, Fukui 919-1205, Japankamaya@inss.co.jp

J. Pressure Vessel Technol 133(6), 061203 (Oct 19, 2011) (7 pages) doi:10.1115/1.4004560 History: Received October 09, 2009; Accepted June 06, 2011; Published October 19, 2011; Online October 19, 2011

High-cycle thermal fatigue is a critical problem in nuclear power plants. To prevent crack initiation, Japan Society of Mechanical Engineers has issued a guideline for design, although growth analysis was not included. In this study, the feasibility of incorporating crack growth analysis into the design and integrity evaluation was investigated. Two characteristics of thermal fatigue loading were considered. The first was the effect of stress gradient in the depth direction. It was shown that the steep stress gradient near the surface significantly reduced the stress intensity factor (SIF) of deep cracks. Assuming that crack growth was arrested by small SIF values, it was judged possible to leave certain detected cracks unrepaired. Otherwise, the cracks should be removed regardless of their size. The other characteristic was the displacement controlled boundary condition. Through finite element analyses, it was revealed that the displacement controlled boundary condition reduced the SIF, and the magnitude of its reduction depended on the crack depth and boundary length. It was concluded that, under thermal fatigue loading, the cracks that were detected in the in-service inspection had already been arrested if they did not penetrate the wall thickness. It is effective to consider the crack arrest scenario for design and integrity assessment of cracked components under high-cycle thermal fatigue loading.

FIGURES IN THIS ARTICLE
<>
Copyright © 2011 by American Society of Mechanical Engineers
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Figure 1

Model for thermal fatigue cracking

Grahic Jump Location
Figure 2

Change in SIF with crack depth

Grahic Jump Location
Figure 3

Stress in the depth direction at the time when crack of 5 mm depth shows maximum SIF

Grahic Jump Location
Figure 4

Change in crack depth with time (frequency: 1 Hz). (a) Initial crack depth ao  = 1 mm; (b) initial crack depth ao  = 3 mm

Grahic Jump Location
Figure 5

Time required to get a 10 mm crack depth (initial crack depth ao  = 1 mm)

Grahic Jump Location
Figure 6

Ratio of TTI to TTF at various frequencies (initial crack depth ao  = 1 mm)

Grahic Jump Location
Figure 7

Depth of arrested crack due to small SIF less than Kth (temperature amplitude Ta  = 140 K, initial crack depth ao  = 1 mm)

Grahic Jump Location
Figure 8

A summary of crack initiation and arrest behavior according to temperature amplitude and frequency

Grahic Jump Location
Figure 9

The crack network model for finite element analysis

Grahic Jump Location
Figure 10

An example of a finite element mesh for crack network (a = 2.5 mm, Wx  = 2 mm, wall thickness: 10 mm)

Grahic Jump Location
Figure 11

Change in SIF with depth of network crack (temperature amplitude Ta  = 140 K, initial crack depth ao  = 1 mm)

Grahic Jump Location
Figure 12

Change in SIF normalized by the theoretical solution with crack depth normalized by the crack network size. The thick line is calculated using Eq. 13. (temperature amplitude Ta  = 140 K, initial crack depth ao  = 1 mm).

Grahic Jump Location
Figure 13

Depth of arrested crack due to small SIF less than Kth for the displacement boundary condition Wx  = 2 mm (temperature amplitude Ta  = 140 K, initial crack depth ao  = 1 mm)

Grahic Jump Location
Figure 14

A summary of crack initiation and arrest behavior according to temperature amplitude and frequency for the displacement boundary condition Wx  = 2 mm

Tables

Errata

Discussions

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related Journal Articles
Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In