Papers by Author: J. Pineault

Abstract: To enhance the fatigue resistance of mechanical components, different surface treatment processes are often applied to put the near surface layer into compression. Surface treatment processes are typically associated with deformation and work-hardening of the material. When applying x-ray diffraction techniques to the characterization of such surfaces, the work-hardening will cause the x-ray diffraction peak width to increase. When peak widths reach high values, the peak tail may extend beyond the active area or window of the multichannel x-ray detector, in which case the peak is truncated. Subsequent analytical treatment of broad diffraction peaks is troublesome and advanced numerical methods are required to accurately determine the peak position. The following work indicates that when a wider detector is used it is possible to collect the full, non-truncated peak, determine the peak position with a high level of confidence and subsequently, to calculate the residual stress with much improved repeatability and reproducibility.

Abstract: With recent issues related to stress corrosion cracking (SCC) and thermal fatigue of power plant components, including nuclear steam generator tubing, condenser tubing, boiler tubes steam turbine blades, the residual stress in materials plays an important role in determining those susceptible for failure caused by fatigue or SCC. These residual stresses, combined with the applied stresses inherited from manufacturing and assembly can be tensile or compressive. The SCC can act in a corrosive environment only when the stresses in the material are tensile, thus leading to cracking of the component and the structure. Thermal fatigue can be originated from thermal gradients caused during the operation of power plants. Proto Manufacturing Limited, leader in the residual stress measurement and equipment development tailored for these applications has developed instruments capable of measuring residuals tresses in confined areas such as inner diameter of tubes as small as 50 mm in diameter, non-destructively in the direction of interest, axial direction. In this paper interesting examples of new x-ray diffraction instrument and measurement validation are presented along with application inside a 50 mm I.D.

Abstract: Although x-ray diffraction techniques have been applied to the measurement of residual stress in the industry for decades, some of the related details are still unclear to many production and mechanical testing engineers working in the field. This is because these details, specifically those associated with the transition between diffraction and mechanics, are not always emphasized in the literature. This paper will emphasize the appropriate calculation methods and the steps necessary to perform high quality residual stress measurements. Additionally, details are given regarding the difference between mechanical and x-ray elastic constants, as well as the true meaning of stress and strain from both diffraction and strain gage point of view. Cases where the material is subject to loading above the yield limit are also included.