MPISI – Materials Probe for Internal Strain Investigations
The MPISI (Zulu name for the spotted hyena) material science neutron diffraction instrument is located at the SAFARI-1 research reactor of the South African Nuclear Energy Corporation (Necsa) SOC Limited.
It is optimized for non-destructive depth-resolved studies of internal strain in bulk structures originating from manufacturing processes and in-service loads. By exploiting the superior penetrating capabilities of neutrons MPISI provides a valuable analysis technique for cutting-edge research in materials engineering and related scientific disciplines. The instrument configuration also allows for the investigation of crystallographic texture in engineered processed materials and natural geological samples.
Typical samples that have already been comprehensively investigated are:
· Welded steel plates (up to 30 mm in thickness),
· Aluminium ring and plug specimen that has a 50 mm diameter,
· Additive manufactured titanium specimens,
· High-resolution investigations, i.e. depth resolution and near surface stresses:
- Laser shock peened aluminium plates 3.3 mm in thickness,
- Laser welded and shock peened aluminium plates 3.3 mm in thickness,
- Laser treated steels.
MPISI is designed to be on equal standing with similar instruments at leading international facilities. State-of-the-art data acquisition, control and analyses systems enable measurement of complex multi-dimensional strain maps of samples whilst optimising neutron beam utilisation. By employing micro-stepping, in conjunction with surface scans, samples can be positioned to within 10 µm accuracy.
Resolution of the MPISI instrument measured from NIST standard silicon powder
Data reduction and analysis
Data reduction is primarily performed in-house using custom-developed software called ScanManipulator
Data acquisition times
The graphs below give an indication of data acquisition times required for the materials alpha-iron (mild steel), aluminium and titanium to attain strain accuracies of 50 microstrain at gauge volume sizes as indicated in the graph legend.
Aluminium ring and plug specimen [GA Webster (ed.), “Neutron Diffraction Measurements of Residual Stress in a Shrink-fit Ring and Plug” 2000 VAMAS Report No. 38 ISSN 1016-2186]
Hot rolled, followed by cold rolled, aluminium plate 3.3 mm in thickness: Correlation of stress results measured on MPISI (Necsa: investigated with a gauge volume of 0.6 x 15 x 0.6 mm3) and Kowari (Ansto, Bragg Institute, Australia: gauge volume of 0.2 x 15 x 0.2 mm3 )
MPISI is accessible by the scientific community for academic and commercial project proposals.
For more information contact:
Dr Andrew Venter: +27 12 305 5038
ISO/TC 135/SC 5/WG 7: Modernisation of ISO/TS 21432 “Non-destructive testing – Standard test method for determining residual stresses by neutron diffraction”, for review as International Standard in 2016. Participation member of project team.
Dr. Deon Marais
B.Eng Computer and Electronic; M.Eng Nuclear; PhD Nuclear Engineering
+27 12 305 5645
Dr. Andrew Michael Venter
+27 12 305 5038