NDTnet 1998 Aug, Vol.3 No.8

Abstract

Shape welding is an interesting alternative method of materials manufacturing. At the same time, the existence of uncontrollable residual stress distributions in welded materials hinders the wide application of this method. On the other hand, the shape welded ferritic layers on austenitic tubes can help suppress stress corrosion because these layers produce compressive stress states in an austenitic tube. The analysis of residual stresses through ferritic welds in austenitic materials can be helpful for the optimization of the corresponding welding technique. The investigated sample (Fig.1) was cut from the manufactured tube.

The neutron diffraction strain measurements were performed with the PEARL instrument on ISIS. The scheme of measurements of radial (along y-axis) and tangential (perpendicular to x,y-plane) components is shown in Fig. 1. These two components were measured simultaneously using the right-hand (RD) and the left-hand (LD) detectors at the scattering angles of +90°. The direct beam was formed by a slit of 2x2 mm². Two focusing radialcollimators in front of the detectors determined the width of 1.8 mm of a window for the scattered beams. The direct beam was scanned along the line AB (see Fig.1) to the depth x=5 mm from the top surface. To measure the axial (along the x-axis of the tube) component, the sample was turned by hand by on 90° so that the x,y-plane was horizontal. The lattice parameters, a, at each measured point were determined for three mutually perpendicular directions of the scattering vector Q by the Rietveld refinement program (Fig.2 for the y-phase and Fig.3 for the -phase). We have used the so-called boundary (edge) values, a, measured far away from the transition zone between the base and the welded materials, as the stress-free value of the lattice parameter, an. For the current measurements, these are the points y=2 mm in Fig.2 and y=34 mm in Fig.3. The obtained strain values appear to be quite reasonable. Detailed calculations of stress tensor components with different combinations of the experimental data and their comparison with the results of the destructive turning out method as well as the theoretical estimates by the finite element method are currently in process.

Fig.1

Fig.2

Fig.3

Abstract Source:
Book of Abstracts, 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN: 87-986898-0-00

Full-Text Source:
Proceedings of the 7th European Conference on Non-Destructive Testing, 26-29 May 1998, ISBN:

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