The benefits of having 6 legs

SALSA is the world-leading neutron instrument for the assessment of residual stress in engineering components. The neutron beam probes the strain of the crystal lattice of the material being studied. Polycrystalline materials which are typically used in a wide range of industries can be studied (construction, aerospace, transport, power generation…).

One of the principal challenges during strain experiments is the movement of the specimen about the neutron beam (gauge volume). SALSA uses a unique hexapod design which has significant advantages over traditional X,Y,Z translators. The hexapod has six independently driven hydraulic legs which can move a specimen of up to 900kg with a precision of the order of a few microns.

The video below demonstrates the use of SALSA during an experiment. A 300mm diameter, 500mm long steel pipe section is maneuvered around the neutron beam for measurements of lattice strain. By measuring strain in several sample directions it is possible to calculate stress.  This set of measurements would usually take many hours but the video shows the measurements at a faster speed.

Ref.:
 - T.Pirling, G.Bruno and P.J.Withers (2006) "SALSA, a new concept for strain mapping at the ILL", Mat. Sci. Eng. A, 437, 139-144.
 - D.J. Hughes, G. Bruno, T. Pirling and P.J. Withers (2006) "First impressions of SALSA: The new engineering instrument at ILL", Neutron News 17, 3, 28-32.