Harry Lester Kington

Manufacturing Related Residual Stresses and Turbine Disk Life Prediction

Machining and surface processing operations, such as grinding, turning, and shot peening are well known producers of near surface residual stresses. Honeywell has conducted numerous life methods development programs to experimentally quantify the residual stresses and the fatigue life associated with various machining operations and shot peening. This experience shows that the magnitude and depth of the near surface residual stresses from the manufacturing methods have a significant influence on the fatigue life of a component. This paper presents an overview of the role near surface residual stresses from machining operations and shot peening have on the life prediction of turbine disks.

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

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.Copyright

High Temperature Hold Time Effects on Fine Grain Processed 718 Fatigue Properties

Fine Grain Alloy 718 is a relatively cost effective turbine and compressor disk alloy with superior yield strength and low cycle fatigue properties. An understanding of Alloy 718’s response to environmental and temperature conditions under sustained peak or dwell conditions is a requirement for assessing actual in-service capability. This is especially critical when the disk operating conditions exceed historical engine experience with Alloy 718. This paper presents a detailed review of experimental dwell low cycle fatigue and cyclic crack growth results for fine grain alloy 718. The experimental fatigue results combined with the observed physical initiation and propagation mechanisms were used to develop a comprehensive life prediction system for fine grain Alloy 718 turbine disk.