Salsa
Strain imager for engineering applications
Macrograph of the ferritic steel weld.The weld runs in the centre of the big plate.
Map of the three perpendicular components of stress, as determined by neutron diffraction.The weld strain affected zone is clearly visible.
The importance of standards
The ILL and the FaME38 laboratory have been strongly involved in the development of a new ISO standard for the determination of residual stress by neutron diffraction. In order to develop industrial confidence in the neutron technique it is important to establish reliable and standard codes of practise. A key part of standard development is the measurement of round-robin samples.
A ferritic steel weld (see figure 1) was prepared and was measured at world-wide neutron sources including the ILL. The stress field in such a weldment is complex as can be seen in figure 2 and is useful for assessing measurement protocols which include sample alignment and data interpretation. The draft standard is currently available as an ISO TTA (technology trends assessment) and is now a full international standard.
Ref.:
- Residual stress distributions in welded ferritic steel T-plate joints . Wimpory R.C. , Stefanescu D. , Smith D.J. , O’Dowd N.P. , Webster G.A. , May P.S. , Kingston E. ; Journal of Neutron Research 11, 201-207 (2003).
- Ferritic steel welds - A neutron diffraction standard Hughes D.J. , Webster P.J. , Mills G. Materials Science Forum 404-407, 561-566 (2002).