Kowari

Strain Scanning (along with reflectometry) has been the major growth area in neutron scattering since its inception 20 years ago. The basic idea is to perform a diffraction experiment, and determine the lattice parameters for the phase(s) of interest in an engineering component. Deviations from a standard unstressed specimen (which can be another portion of the same object) are strains, and with some simple analysis stresses can be extracted. This may be averaged across a whole sample, for instance in the case of metal-ceramic composites, to understand how load is shared between the metal matrix and the ceramic reinforcement. More often, one uses carefully defined apertures before and after the specimen to define a gauge volume of ~1mm³ or less. The object, which may be as large as a whole engine, is then translated and rotated to map out the strains (and therefore the stresses) within the object of engineering interest.

The main advantage of using neutrons (as opposed to X-rays) is that neutrons can penetrate centimetres into the object of interest. X-rays, on the other hand, are mainly useful for surface problems, like coatings on gears or cutting tools, and for issues in the semiconductor industry. Both neutron and X-ray strain-scanning is limited to crystalline materials, so we cannot study stresses in plastics or glass by this method.

All our activities in this area are in partnership with the Institute for Materials and Engineering Sciences, and its various projects including the 'Neutrons for Engineering' Project.

The basic experiment is very simple, and the main challenge is to design the instrument sample table in such a way that it can accommodate large objects (up to 1 tonne) and move them around reproducibly to within ~20 mm. The major limitation of our present HIFAR instrument is that it simply does not have enough room at the sample position to handle most engineering problems. In the last 5 years or so, neutron facilities around the world have been constructing dedicated strain scanners, and KOWARI will be in this first wave of dedicated strain scanners.

In Australia, we see the major usage being in problems with steel (and to a lesser extent aluminium-alloy) components, particularly welds. This reflects the nature of Australia's dominant industries: mining, power generation and transmission, shipbuilding, railways, construction (for instance of sports stadia), life extension of defence assets, and so on. In Europe and the USA, there is a greater emphasis on higher value-added applications from the aerospace, defence and automotive industries, where composite and other unconventional materials are increasingly being used. Our ambition is to be good enough at what we do that we will attract business from around the world, much as the Canadians have already done at Chalk River. We hope to build a program that is roughly 50% commercial and 50% academic.

The basic-science interest is likely to be in understanding, at a microscopic level, what is going on in well-known processes like plastic deformation and creep, and in new materials and composites. Much of this work will require facilities for applying stresses in situ, and at specified elevated temperatures. It is also clear that there will be an increase in the study of the correlation between texture (preferred orientation of the grains, due to processing) and residual stresses, and in-situ studies of important processes like rolling, welding, milling, etc. So long as the rigs for such studies can be designed and funded in the future, this will all be possible on KOWARI.

There is a web highlight on laser-repair of steam-turbine blades for power stations (through the CRC for Welded Structures), and our present experimental portfolio includes: pressure-vessel steels, aircraft-skin aluminium alloys, automobile brake rotors, welding of rails, hardening of die steels, coatings for aero-engine components, and various problems in stainless steel.