0
Research Papers: Materials and Fabrication

A New Technique for Intergranular Crack Formation in Alloy 600 Steam Generator Tubing

[+] Author and Article Information
Tae Hyun Lee

 Seoul National University, 56-1, Shillim, Kwanak, Seoul 151-742, Koreaehfaks2@snu.ac.kr

Il Soon Hwang

 Seoul National University, 56-1, Shillim, Kwanak, Seoul 151-742, Korea

Han Sub Chung

 Korea Electric Power Research Institute, 103-16 Mungi, Yusung, Taejon 305-380 Korea

Jang Yul Park

 Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439

J. Pressure Vessel Technol 130(1), 011403 (Jan 17, 2008) (11 pages) doi:10.1115/1.2826423 History: Received July 03, 2006; Revised December 22, 2006; Published January 17, 2008

For the integrity management of steam generator (SG) tubes, nondestructive evaluation performed using eddy current test (ECT) is necessary in the assessment. The reliability of ECT evaluation is dependent on the accuracy of ECT for various kinds of defects. For basic calibration and qualification of these techniques, cracked SG tube specimens having mechanical and microstructural characteristics of intergranular cracks in the field are needed. To produce libraries of laboratory-degraded SG tubes with intergranular cracks, a radial denting method was explored for generating inside diameter and outside diameter axial cracks by three-dimensional finite element analysis and experimental demonstration. The technique is proven to be applicable for generating axial cracks with long and shallow geometries as opposed to the semicircular cracks typically obtained by the internal-pressurization method. In addition, a direct current potential drop method with array probes was developed for accurate monitoring and controlling of crack size and shape. By these methods, long and shallow intergranular axial cracks more typical of actual degraded SG tubes were successfully produced.

Copyright © 2008 by American Society of Mechanical Engineers
Your Session has timed out. Please sign back in to continue.

References

Figures

Grahic Jump Location
Figure 19

Potential contour and dc flow vector of CT specimen using electrostatic FEM computational results

Grahic Jump Location
Figure 11

Surface axial crack produced on the tube outer surface by the radial dent loading

Grahic Jump Location
Figure 12

Destructive examination of 17.65‐mm-o.d. long and shallow crack and sectioned area for confirming the crack depth (numbers represent locations of the DCPD probe)

Grahic Jump Location
Figure 13

Results of outside diameter circumferential crack generation by direct tensile loading

Grahic Jump Location
Figure 14

SEM observation on fracture surface of circumferential crack after rupture

Grahic Jump Location
Figure 28

Result of DCPD signal of real experiment for outside diameter circumferential crack as a function of time

Grahic Jump Location
Figure 29

Result of correlation analysis between the measured DCPD data and predicted DCPD simulation data for an outside diameter circumferential crack

Grahic Jump Location
Figure 15

Overview of apparatus for inside diameter axial generation (applying the DCPD method)

Grahic Jump Location
Figure 16

Schematic of traveling microscope technique to confirm initiation condition of crack, as an in situ monitoring method for inner wall crack generation

Grahic Jump Location
Figure 17

Destructive examination of 25.4‐mm-i.d. long and shallow crack and sectioned area for confirming the crack depth (numbers represent locations of the DCPD probe)

Grahic Jump Location
Figure 18

Schematic of DCPD FEA simulation model and FEM meshing model

Grahic Jump Location
Figure 1

The schematic of goals and approach of this thesis

Grahic Jump Location
Figure 2

Result of crack initiation time as a function of Na-tetrathionate concentration and load

Grahic Jump Location
Figure 3

Schematic of the radial denting method applied for the axial cracking at either outer or inner surface

Grahic Jump Location
Figure 4

Finite element mesh structure used in FEA of dent loading

Grahic Jump Location
Figure 5

Stress distribution in the tube cross section of a dent loaded tube

Grahic Jump Location
Figure 6

Circumferential stress distribution at each position as a function of denting load per unit axial length (the location of each point is defined in Fig. 5)

Grahic Jump Location
Figure 7

Diametric displacements corresponding to the initial position with loading to 35.6kN∕m followed by unloading (the location of each point is defined in Fig. 5)

Grahic Jump Location
Figure 8

Vertical diameter changes measured (a) and predicted by three-dimensional FEA (b) after a radial dent loading to 40.0kN∕m followed by unloading

Grahic Jump Location
Figure 9

(a) Finite element mesh structures employed for the tube taking into account a fourfold symmetry, (b) predicted shear stress, (c) von Mises stress, and (d) axial stress distribution contours under direct tensile loading

Grahic Jump Location
Figure 10

Dent loading test apparatus with DCPD and observation microscope

Grahic Jump Location
Figure 25

DCPD signal in proportion to the crack depth for the 17.65mm long intergranular outside diameter axial crack

Grahic Jump Location
Figure 26

Normalized DCPD signals and flaw depth for a mechanical notch and for the 17.65mm long intergranular crack as a function of axial distance from the specimen center

Grahic Jump Location
Figure 27

Comparison of measured DCPD signal and predicted DCPD data using FEA of 25.4‐mm-i.d. axial crack

Grahic Jump Location
Figure 20

Comparison between Johnson’s theoretical normalized potential data with FEM simulation results as a function of normalized crack length

Grahic Jump Location
Figure 21

Twofold symmetry FEA meshing model and predicted potential contours of Alloy 600 tube specimen without crack

Grahic Jump Location
Figure 22

FEM meshing model with crack that has a fixed a∕c ratio of 0.1

Grahic Jump Location
Figure 23

Predicted DCPD increase as a result of an outside diameter axial crack at each DCPD probe position as a function of crack depth (the fixed a∕c ratio is 0.1)

Grahic Jump Location
Figure 24

DCPD measurements from the probe arrangement compared with the actual crack depth of a penny-shaped machine notch produced by a diamond saw cut

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.

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