Stress measurement by X-ray diffractometry

Details Stress measurement by X-ray diffractometry Stress measurement by X-ray diffractometry

1983-02-18

1985-12-24

Krass, Errol A.

Boots, shoes, and leggings

73786, 364508, 378 72, G01N 1500, G01M 500

Patent

active

045610622

ABSTRACT:
A portable X-ray diffractometer for measurement of residual stress in metallic specimens, especially large structures, such as bridges, pipelines etc. The instrument consists of a pair of position sensitive detectors arranged to be mounted in fixed positions relative to the specimen. An X-ray source that projects a collimated incident beam onto the area of the specimen under examination is located between the detectors so that each receives a diffraction line. The source is scanned stepwise in an arc about the specimen area, while the specimen and both the detectors remain fixed. The diffraction lines received in each detector are stored in a computer as histograms of intensity values. For each angular relationship between the incident beam and the chosen direction of strain measurement, a series of such intensity values corresponding to a given diffraction angle for successive diffraction lines is averaged and a resultant diffraction line obtained for each detector. To keep the mean strain directions constant and achieve a constant range of grain orientations for all diffraction angles, the instrument restricts the intensity values so averaged to those that fall within a virtual window. This window is moved along the channels, one or more channels per scanning step. The two resultant series of averaged values are examined to find peaks or other characteristics of the diffraction line and the angular relationships corresponding thereto. This knowledge enables determination of lattice strains in two directions, the two strains determining the stress in the specimen surface.

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Jrl. of Metals, "Review of Nondestructive Methods for Residual Stress Measurement", Jul. 1981, C. O. Ruud, pp. 35-39.
Advances in X-Ray Analysis, vol. 20 (1977), "A Dual Detector Diffractometer for Measurement of Residual Stress", C. M. Mitchel, pp. 379-391.
Advances in X-Ray Analysis, vol. 22 (1979), "New Method for Fast XRPD using a Position Sensitive Detector", H. E. Gobel, pp. 255-265.

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