Implementation of Multi-Axial Fatigue Theory in FE Packages

Abstract:

Many mechanical or structural components are subjected to multi-axial, irregular cyclic loading during service. The direction and amplitude of principal stress and strain vary over a period of time results in non-proportional cyclic loading on the component. At geometrical discontinuities, even a monotonic load will result in multi-axial state of stress. In general, the life of the components subjected to multi-axial stress loadings, are evaluated using classical yield theories. The Tresca and von Mises criterions along with Basquin-Coffin and Manson life curve are widely used in commercially available Finite Element Analysis (FEA) tools. These classical methods are conservative and may not yield good experimental correlation at all the loading conditions and this augments the need for robust life estimation methodology.There are many commercially available FEA tools to estimate the multi-axial fatigue life viz. nCODE^® which uses Wang-Brown method [1]. However, it has been found that for shear dominated fatigue material Fatemi-Socie criteria is more suitable. So an attempt is made to develop a an algorithm to implement Fatemi-Socie criteria in a commercially available generic FEA software in a cost effective way. This paper discusses how to estimate the life of a sample specimen subjected to multi-axial and non-proportional loading conditions. The classical yield criteria based on von-Mises stress with Basquin-Coffin and Manson equation and critical plane method viz, Fatemi-Socie criteria are implemented in to commercial FEA tool, ANSYS. This paper also attempt to see how these theories compare with experimental data. Results of this study would help in leveraging the established process of implementing custom based life estimation method in ANSYS for the estimation of the life of the mechanical components.

• Periodical: Key Engineering Materials (Volume 719)
• Pages: 46-54
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.719.46
• Online since: November 2016
• Authors: Madhu Bharadwaj*, Prajwal Rao, Sowmianarayanan Srinivasan
• Keywords: ANSYS, Basquin-Coffin, Fatemi-Socie Criteria, Manson, Multi-Axial Fatigue

References

[1] Design Life Theory Guide, nCode help manual.

[2] Susmel, Luca., A simple and efficient numerical algorithm to determine the orientation of the critical plane in multiaxial fatigue problem, International Journal of Fatigue, 2010, Vols. 32; 1875-1883.

DOI: 10.1016/j.ijfatigue.2010.05.004

[3] Kurath, Peter and Darrel F Socie, The relationship between observed fatigue damage and life estimation model, NASA Contract report 182191, August, (1988).

[4] Justin Lee Koch, proportional and non propotional biaxial fatigue of Inconel 718, Masters thesis, university of Illinois, (1985).

[5] Manson, S. S, Fatigue: A complex subject—Some simple approximations, Experimental Mechanics, Issue 4, pp.193-226, , July 1965, Vol. Volume 5.

[6] Coffin, L F, A study of effect of cyclic thermal stresses on ductile metal, Trans. ASME 1954, pp.931-50.

[7] Basquin, O H., The exponential law of endurance test, Am Soc Test Mater Proc 1910, p.20: 625-30.

[8] Fatemi A, Socie DF, A critical plane approach to multiaxial fatigue damage including out of phase loading, Fatigue and Fracture of Engineering Materials and Structures1988, p.11: P149-65.

DOI: 10.1111/j.1460-2695.1988.tb01169.x

[10] Papuga, Mapping of Fatigue Damages – Program Shell of FE-Calculation, Czech Technical University in Prague, August 2005. PhD Thesis.

[11] Socie, D. F. and Marquis, G. B. Multiaxial fatigue, Society of Automotive Engineers, Inc., (2000).

[12] Ali Fatemi, Ralph I Stephen, Robert R Stephen, Henry O Fuchs, Metal Fatigue in Engineering, A wiley-interscience Publication , (2001).