Authors: J RamirezRico SY Lee J J Ling I C Noyan
Publish Date: 2016/02/29
Volume: 51, Issue: 11, Pages: 5343-5355
Abstract
Using area detectors for stress determination by diffraction methods in a single exposure greatly simplifies the measurement process and permits the design of portable systems without complex sample cradles or moving parts An additional advantage is the ability to see the entire or a large fraction of the Debye ring and thus determine texture and grain size effects before analysis The two methods most commonly used to obtain stress from a single Debye ring are the socalled cos alpha and fullring fitting methods which employ leastsquares procedures to determine the stress from the distortion of a Debye ring by probing a set of scattering vector simultaneously The widely applied sin 2psi method in contrast requires sample rotations to probe a different subset of scattering vector orientations In this paper we first present a description of the different methods under the same formalism and using a unified set of coordinates that are suited to area detectors normal to the incident beam highlighting the similarities and differences between them We further characterize these methods by means of in situ measurements in carbon steel tube samples using a portable detector in reflection geometry We show that in the absence of plastic flow the different methods yield basically the same results and are equivalent An analysis of possible sources of errors and their impact in the final stress values is also presentedLoading experiments were performed at the Robert W Carleton Strength of Materials Laboratory Columbia University Dr A Brügger’s assistance with the loading setup is gratefully acknowledged The Xray portable stress measurement device was kindly supplied by Pulstec Industrial Co Ltd The authors would like to thank Toshikazu Suzuki and Yoshinobu Teramoto for installation and technical support J RamirezRico gratefully acknowledges the support from the Universidad de Sevilla Research Fund V Plan Propio
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