Methods for the Design, Quality Control, & Management of Fatigue-Limited Metal Components

Author:  Berkley
Source:  US Patent 5,625,664
Doc ID:  1995036
Year of Publication:  1995
Abstract:  
Improved methods for managing a population of metal components subject to fatigue failure are provided. The residual compressive stress in the critical surfaces of such components, especially in areas of high stress concentration, are measured non-destructively using x-ray diffraction techniques. The measured surface residual compressive stress is used as a management criterion. A component having a surface residual compressive stress greater than a predetermined value can be returned to service. However, once the measured surface residual compressive stress of a component falls below the predtermined value, it can either be removed permanently from service, or it can be reworked to increase its surface residual compressive stress and then returned to service. Additionally, by measuring the surface residual compressive stress of an individual component, the remaining servic life of that individual component can be estimated. These methods for management of populations of such metal components allow for increasing the service life of the components in a safe and effective manner. Methods are also provided for the manufacture and/or design of metal parts with improved performance criterion (e.g., reduction in weight) while maintaining acceptable service life. Methods using surface residual compressive stress measurements during and/or after the manufacturing process in order to prevent, for example, introduction of metal parts having insufficient surface residual compressive stress levels for their intended use.