Eventos Anais de eventos
MECSOL 2019
7th International Symposium on Solid Mechanics
Strain-based fatigue life predictions using measured and estimated material parameters
Submission Author:
Caio Ferreira Barros , RJ
Co-Authors:
Caio Ferreira Barros, Jorge Alberto Rodriguez Duran
Presenter: Caio Ferreira Barros
doi://10.26678/ABCM.MECSOL2019.MSL19-0132
Abstract
The fatigue life can be calculated from local strain amplitudes according to the well known Coffin-Manson relation. For notched bodies, neglecting hardening and softening transients, local strains should follow simultaneously the cyclic stress-strain curve and a stress concentration rule. Occasionally, the fitting constants for the cyclic stress-strain curve are not available and the so called compatible constants are used instead. The compatible constants are calculated from the cyclic constants fitted to the strain-life curve. The present paper evaluates the consequences that this decision have on the final life calculated with the strain-based approach to fatigue and how divergent are the results generated according to the material and analysis parameters. The fatigue life results obtained with the compatible constants for aluminum show considerable divergence in relation to the results obtained with the experimental constants, which varies according to the values of the other parameters of the analysis, such as stress amplitude Sa, stress ratio R and stress concentration factor kt. Between the results, stand out the highly conservative results for lives less than 10⁵ cycles in combinations of R ≥ 0 and kt ≥ 3, as well as the non-conservative results for analysis performed with R ≥ 0, especially for lives greater than 10⁵ cycles. Therefore, in these contexts it is not recommended to use compatible constants.
Keywords
strain-based approach to fatigue, aluminum fatigue, cyclic stress-strain constants, strain-life constants, compatible constants
