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Fatigue Evaluation of Notched Plate Specimens by the Battelle Structural Stress Method
Abstract:
In this paper, the applicability of the finite element-based, mesh insensitive Battelle structural stress method is demonstrated for fatigue life predictions of notched specimens (non-welded) with different specimen types, and notch shapes. Well-documented notch fatigue data were analyzed using the Battelle structural stress fatigue evaluation procedure, including notched plate fatigue data for steel and aluminum alloys.
The effectiveness of the Battelle structural stress procedure has been demonstrated in a series of earlier publications for welded structures with different joint types, plate thicknesses, and loading modes. Here, a similar Battelle structural stress procedure suitable for finite element modeling and service life simulations is proposed for structures with notches. Unlike weld fatigue data, the crack propagation portion of the fatigue life associated with a notch does not always dominant the total number of cycles to failure. It depends on the stress state at the notch tip. Also, mean stress effects can be seen clearly in S-N curves for notched fatigue data.
Based on the characteristics of the notch stress, a structural stress calculation procedure for notched plates is proposed. A characteristic ligament size is introduced for the equivalent structural stress range calculation. It is found that fatigue test data for notched specimens can be effectively collapsed onto a single master S-N curve regardless of notch geometry, notch stress concentration factor, and mean stress. The proposed procedure can be utilized for fatigue life predictions of notched plates.