SYMPOSIA PAPER Published: 01 January 1985
STP36240S

Fatigue Life Estimates for a Simple Notched Component Under Biaxial Loading

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Three-dimensional stress-strain fields are routinely determined for complex components using elastic and elastic-plastic finite element models. Although the local stress-strain response can be easily determined, the proper approach to strain based multiaxial fatigue analysis is not clear. Several multiaxial fatigue theories have been suggested, but there exists a lack of consensus on which model is most appropriate. To clarify the situation, experiments have been performed on two different multiaxial specimen geometries. Results are compared with theoretical predictions.

Thin-walled tube specimens have been tested using combined in-phase tension-torsion loading. This specimen geometry has a simple uniform stress-strain state. Tests were also performed using a solid notched shaft specimen subjected to inphase torsion-bending loads. Stress-strain gradients exist in the notch root. Local multiaxial stress-strain fields were determined using an elastic-plastic finite element model.

Five current multiaxial strain based fatigue theories have been developed to correlate the experimental results. Fatigue life estimates were based upon uniaxial strain controlled fatigue data.

Correlations for the thin-walled tube test series were within a factor of 3 in fatigue life. For the notched shaft specimen with the more complex stress-strain state, life estimates were in error by a factor of 10 in fatigue life. This suggests that the effects of geometry are as important as the selection of the fatigue theory. Much additional work needs to be done to understand the effect of notches in multiaxial fatigue before these methods can be routinely implemented by designers.

Author Information

Fash, JW
University of Illinois at Urbana-Champaign, Urbana, IL
Socie, DF
University of Illinois at Urbana-Champaign, Urbana, IL
McDowell, DL
School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA
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Details
Developed by Committee: E08
Pages: 497–513
DOI: 10.1520/STP36240S
ISBN-EB: 978-0-8031-4921-2
ISBN-13: 978-0-8031-0444-0