Quantitative analysis and benchmarking of positional accuracies of neutron strain scanners

Positional accuracy is an important parameter in residual stress investigations with neutron diffraction, considering that precise measurements of strains at the same localised position along a number of sample orientations are required, including investigations of complete complex shaped engineering components. This study reports the development of a standardised approach for quantitative analysis of positional accuracy on neutron strain scanners that builds on previous campaigns. The approach uses standardised sample sets with specific geometries that enable quantitative assessment of instrumental and sample alignment procedures and associated accuracies. This method has been implemented on four participating instruments: ENGINX (United Kingdom), MPISI (South Africa), SALSA (France) and STRESS-SPEC (Germany), to render results representative of monochromatic and time-of-flight strain scanners. The benchmarking results show comparable performance between the instruments with positional accuracies around 100 ?m readily achieved. This standardised approach confirms the high positional precision attainable for non-destructive stress determination, to unequivocally benefit utilisation by academia and industry alike. It is envisaged that this common calibration protocol and reporting template that conforms to the newly developed Neutron Quality Label for Internal Stress Characterisation be adopted by other facilities to facilitate expansion of the supportive network.

Automated summary

Positional accuracy is a crucial parameter in neutron diffraction residual stress investigations, requiring precise measurements of strains at localized positions along multiple sample orientations. A standardized approach has been developed for quantitative analysis of positional accuracy on neutron strain scanners, using specific sample sets with geometries for assessment of alignment procedures and accuracies. The method has been implemented on four instruments to achieve comparable performance with positional accuracies around 100 µm, confirming the high precision attainable for non-destructive stress determination.