Shot Peen Impact on Life, Part 3: Development of a Fracture Mechanics/Threshold Behavior Predictive Model

Author:  M Tufft
Source:  Conf Proc: ICSP-7 (pg 264-273)
Doc ID:  1999037
Year of Publication:  1999
Abstract:  
Shot peening, long recognized for its potential to increase fatigue life capability has also been observed to cause the reverse effect under some circumstances. Single particle impact tests resulted in two major observations: 1) increase in velocity correlated with a deviation from Hertzian impact behavior, and 2) as impact severity increased, so did accumulation of microstructrual slip. these observations ultimately led to the development of a dual criteria Fracture Mechanics / Threshold Behavior fatigue life predictive model. This model, developed for Rene 88DT, permits a lower bound life estimate and can be used to help define robust peening conditions. A microstructural slip depth measurement is used to define an initial crack size for a Fracture Mechanics calculation, providing a lower-bound life estimate. An impact severity criteria, linked to total shot velocity, is used to identify conditions for which the Fracture Mechanics model life estimate is conservative.