Direct sample positioning and alignment methodology for strain measurement by diffraction

Nicolas Ratel-Ramond (1, 2) , D. J Hughes (1) , A. King (3) , B. Malard (4) , Z. Chen (1) , P. Busby (5) , P. J Webster (1, 5)

1 ILL - Institut Laue-Langevin
2 CEMES - Centre d'élaboration de matériaux et d'études structurales
3 University of Manchester [Manchester]
4 LTPCM - Laboratoire de thermodynamique et physico-chimie métallurgiques
5 University of Salford

An ISO International Organization for Standardization TTA Technology Trends Assessment was published in 2001 for the determination of residual stress using neutron diffraction which identifies sample alignment and positioning as a key source of strain measurement error. Although the measurement uncertainty by neutron and synchrotron x-ray diffraction for an individual measurement of lattice strain is typically of the order of 10– 100 10 −6 , specimens commonly exhibit strain gradients of 1000 10 −6 mm −1 or more, making sample location a potentially considerable source of error. An integrated approach to sample alignment and positioning is described which incorporates standard base-plates and sample holders, instrument alignment procedures, accurate digitization using a coordinate measuring machine and automatic generation of instrument control scripts. The methodology that has been developed is illustrated by the measurement of the transverse residual strain field in a welded steel T-joint using neutrons.

Domaines: Science des matériaux [cond-mat.mtrl-sci]; Instrumentations et Détecteurs [physics.ins-det]

Nicolas Ratel-Ramond, D. J Hughes, A. King, B. Malard, Z. Chen, et al.. Direct sample positioning and alignment methodology for strain measurement by diffraction. Review of Scientific Instruments, 2005, 76 (5), pp.055103. ⟨10.1063/1.1896726⟩. ⟨hal-01761649⟩