An Evaluation of the Staircase and Over-Stress Probe Methods for Fatigue Life Characterization in Aluminum Sand Castings

Laboratory-based fatigue test methods are often used to estimate the life of components in service conditions. Two common laboratory-based methods used for fatigue durability are the Staircase and the Over-Stress Probe (OSP) methods. Both methods are widely used in academia and industry; both have benefits and limitations in adequately providing for a lifespan estimation. A study was conducted to examine the results from staircase and OSP fatigue tests on 176 specimens taken from AlSiCuMg engine block castings. The OSP method was found to allow a more complete fractographic assessment of porosity compared to the staircase method. It is concluded that the OSP method yields information to better drive decisions regarding process changes that influence desired specific outcomes in terms of product performance and durability.