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Research Papers: Materials and Fabrication

# Computational and Experimental Studies of High Temperature Crack Initiation in the Presence of Residual Stress

[+] Author and Article Information
Noel P. O’Dowd

Department of Mechanical and Aeronautical Engineering, Materials and Surface Science Institute,  University of Limerick, Limerick, Ireland

Kamran M. Nikbin

Department of Mechanical Engineering, Imperial College London, London SW7 2AZ, UK

Robert C. Wimpory

Hahn-Meitner Institut, Glienicker Strasse 100, D-14109 Berlin, Germany

Farid R. Biglari

Department of Mechanical Engineering, Amirkabir University of Technology, Hafez Avenue, Tehran, Iran

Manus P. O’Donnell

British Energy Generation Ltd., Barnett Way, Barnwood, Gloucester GL4 3RS, UK

J. Pressure Vessel Technol 130(4), 041403 (Aug 22, 2008) (7 pages) doi:10.1115/1.2967831 History: Received October 27, 2006; Revised June 19, 2007; Published August 22, 2008

## Abstract

Residual stresses have been introduced into a notched compact tension specimen of a 347 weld material by mechanical compression. The required level of compressive load has previously been determined from finite-element studies. The residual stress in the vicinity of the notch root has been measured using neutron diffraction and the results compared with those obtained from finite-element analysis. The effect of stress redistribution due to creep has been examined and it is found that a significant reduction in stress is measured after $1000h$ at $650°C$. The implications of these results with regard to the development of damage in the specimen due to creep relaxation are examined.

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## Figures

Figure 1

Schematic of compact tension specimen

Figure 2

Tensile data for the 347 MMA weld steel

Figure 4

Finite element mesh of the C(T) specimen

Figure 5

Load-displacement curve during the compression of the notched specimen

Figure 6

Comparison of the experimental data and FE predictions for the back-face strain (see Fig. 1)

Figure 3

Predicted creep response of the material

Figure 7

Residual stress profiles obtained from the finite-element analysis

Figure 8

Comparison of the plane strain and plane stress finite-element solutions with the 3D solutions

Figure 9

Comparison between the finite-element and the measured residual stresses

Figure 13

Residual stress at the central line following creep at 650°C

Figure 14

Measured residual stress following precompression and after 1000h at 650°C

Figure 15

Stress triaxiality following precompression and after 1000h at 650°C

Figure 16

Damage (normalized by the uniaxial failure strain) ahead of the notch after 1000h at 650°C

Figure 10

Prediction between the numerical and experimental stresses: (a) hydrostatic and (b) equivalent (von Mises) stresses

Figure 17

Predicted fracture surface for the notched specimen for εf=1%

Figure 11

Evolution of notch stress in the specimen

Figure 12

Comparison of stress distribution following creep for two different creep models

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