Study of the Precision of X-Ray Stress Analysis.
Abstract
Software is described for complete computer control of residual stress measurements. One program (that incorporates either the two tilt method, the sin squared psi procedure, or the Cohen-Marion technique) has been developed for use with either a normal detector or a position sensitive detector. The operator inputs the desired error in stress and various instrumental parameters that determine systematic errors. The counting strategy to obtain the total error is then determined by the software. Employing this automated system, an investigation of a parabolic fit to the top of a diffraction profile indicates that a three point fit is satisfactory only for sharp profiles. Surprisingly, with a standard detector for fixed total time of data accumulation, the sin squared psi procedure gives better precision than the two tilt method. A position sensitive detector system exhibited excellent precision in replicate residual stress measurements. Errors of + or - 6000 psi were obtained on samples having broad diffraction profiles in only 30 seconds. It was also found that sample displacement is less important for stationary slit geometry than with parafocusing technique. Parallel beam geometry shows minimal effects due to sample displacement (as is well known) but precision of the residual stress measurement decreases because this procedure broadens the diffraction profile. Design parameters for a portable unit based on these results are discussed. This research was supported by the U.S. Office of Naval Research. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 01, 1976
- Accession Number
- ADA027874
Entities
People
- Jerome B. Cohen
- Michael R. James
Organizations
- Northwestern University