Role of Quantitative NDE Techniques in Life Management of Gas Turbine Components

Abstract

A number of earlier publications discussed the benefits of probabilistic analysis and probabilistic lifing in application to critical rotating engine components. One of the important variables in both probabilistic and deterministic lifing analysis is the level of residual stress in the component. Near surface residual stresses directly influence the fatigue life of critical engine rotating components. Depending on sign and magnitude a near surface residual stress gradient can either inhibit or accelerate fatigue initiation and crack propagation. A major barrier to introducing subsurface residual stress information into the life calculation process is the necessity to make accurate and reliable nondestructive measurements on as produced hardware. The paper reviews several NDE technologies that could be candidates for both production and in-service non-destructive residual stress measurements. The importance of having accurate residual stress information and its use in the probabilistic design and life management process is illustrated on several examples. A linkage with several ongoing industry R&D programs is discussed.