Method for measuring and extending the service life of fatigue-limited metal components

A method for managing a population of metals parts in order to extend the service life of individual metal parts in the population, wherein said metal parts are manufactured having relatively high levels of residual compressive stress and said metal parts are subject to fatigue-related failure during service, said method comprising, for each individual metal part in the population:

• (1) removing the individual metal part from the population from service;
• (2) measuring the remaining residual compressive stress of the surface of the individual metal part in one or more areas of stress concentration using x-ray diffraction techniques;
• (3) comparing the remaining residual compressive stress measured in the one or more areas of stress concentration to a predetermined level;
• and
• (4) if the remaining residual compressive stress remains above the predetermined level, returning the individual metal part to service;
• or
• (5) if the remaining residual compressive stress is at or below the predetermined level, reworking the individual metal part to increase the residual compressive stress to a reworked level above the predetermined level and then returning the individual metal part to service.

A method for determining when to remove a metal part from service, wherein said metal part is manufactured having relatively high levels of residual compressive stress and said metal part is subject to fatigue-related failure, said method comprising:

• (1) measuring the remaining residual compressive stress of the surface of the metal part in one or more areas of stress concentration using x-ray diffraction techniques;
• (2) comparing the remaining residual compressive stress measured in the one or more areas of high stress concentration to a predetermined value;
• and
• (3) removing the metal part from service if the remaining residual compressive stress measured in the one or more areas of stress concentration is less than the predetermined level.

A method for extending the service life of a metal part, wherein said metal part is manufactured having relatively high levels of residual compressive stress and said metal part is subject to fatigue-related failure during service, said method comprising:

• (1) measuring the remaining residual compressive stress of the surface of the metal part in one or more areas of stress concentration using x-ray diffraction techniques;
• (2) comparing the remaining residual compressive stress measured in the one or more areas of stress concentration to a predetermined level;
• and
• (3) if the remaining residual compressive stress remains above the predetermined level, returning the metal part to service;
• or
• (4) if the remaining residual compressive stress is at or below the predetermined level, reworking the metal part to increase the residual compressive stress to a reworked level above the predetermined level and then returning the metal part to service.