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RESEARCH PAPERS

# Residual Stresses Evaluation in Welds and Implications for Design for Pressure Vessel Applications

[+] Author and Article Information
John W. H. Price

Department of Mechanical Engineering, Monash University, Clayton, Victoria 3800 AustraliaJohn.Price@eng.monash.edu.au

Anna M. Pardowska

Department of Mechanical Engineering, Monash University, Clayton, Victoria 3800 AustraliaAnna.Paradowska@eng.monash.edu.au

Raafat Ibrahim

Department of Mechanical Engineering, Monash University, Clayton, Victoria 3800 AustraliaRaafat.Ibrahim@eng.monash.edu.au

Trevor R. Finlayson

School of Physics, Monash University, Clayton, Victoria 3800 AustraliaTrevor.Finlayson@spme.monash.edu.au

J. Pressure Vessel Technol 128(4), 638-643 (Jan 22, 2006) (6 pages) doi:10.1115/1.2349577 History: Received August 16, 2005; Revised January 22, 2006

## Abstract

Welding residual stresses have important consequences on the performance of engineering components. High residual stresses may lead to loss of performance in corrosion, fatigue, and fracture but as yet these consequences are poorly quantified. The major cause of this is that residual stress often remains the single largest unknown in industrial damage situations since it is difficult to measure or estimate theoretically. One of the key issues in the study of residual stress is that the detail of the stress distribution on a small scale (in the order of millimeters) can be important. In this paper, the neutron diffraction technique is used which while it is a very expensive technique, is capable of nondestructively measuring residual stresses at this scale up to a depth of $35mm$. The investigation reported compares the residual stress characteristics due to various restraints for a single bead and in fully restrained samples with different numbers of beads. This paper considers the results of the neutron diffraction studies in relation to fitness for purpose guidance and implication for pressure vessel design.

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## Figures

Figure 1

Illustration of the weldments: (a) unrestrained single bead on plate (sample I); (b), (c), and (d) are fully restrained: (b) single bead on plate (sample II); (c) two beads (sample III); and (d) three beads on plate 50% overlapping (sample IV)

Figure 2

Optical micrograph through welded section showing: fusion line, FL, parent metal, PM, weld metal, WM, and heat affected zone, HAZ

Figure 3

Hardness profile 1.5mm below the surface of the parent material. HAZ from −7mm to 7mm from the center line of the weld x=0.

Figure 4

Principles of the neutron diffraction technique showing Bragg reflection from the crystal plane d. (The grain size is greatly exaggerated for clarity—there is normally a large number of grains in the gauge volume).

Figure 5

The direction of the measurements (transverse x, normal y, longitudinal z) using neutron diffraction on the single bead-on-plate

Figure 6

Unrestrained sample I. The longitudinal, transverse, and normal components of strains (a) and stresses (b) measured by neutron diffraction against distance from the weld centerline. Error bars based on uncertainty in the value of the peak diffraction angle are shown.

Figure 7

Strains and stresses measured in fully restrained sample II

Figure 8

The change in residual stress (RS) in fully restrained sample I in comparison to unrestrained sample II

Figure 9

The change in (a) longitudinal, (b) normal, and (c) transverse stress distribution after depositing first bead (sample II), second bead (sample III), and third bead (sample IV)

## Errata

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