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Abstract—Fatigue analysis can be performed using one of the three basic methodologies such as stresslife
theory, strain-life theory, and crack- growth approach. These techniques determine the number
of cycles to failure. Stress-life theory is suitable when elastic stresses and strains are considered.
However, for the components having nominal cyclic elastic stresses and plastic deformation,
local strain-life theory is used for predicting the fatigue life. In the present work, fatigue behaviour
of structural steel parabolic spring, subjected to fully reversible cyclic loading, is analyzed using
different strain-life theories. The analysis is aimed to predict the fatigue life of parabolic spring
and to study the effects of trapezoidal and inverted trapezoidal cross-sections and applied
cyclic stress amplitude through finite element analysis. The modelling of parabolic spring is
carried out in CATIA software whereas ANSYS workbench is used for the finite element analysis.
Maximum Von Mises stress criterion is used for predicting the failure of parabolic spring. It is
observed that Morrow’s strain-life theory is found to be conservative compared to Smith-Watson-
Topper (SWT) strain-life theory under the fully reversible cyclic loading. However, if the loading
sequence is predominantly tensile in nature, SWT theory gives conservative result.
Index Terms—Parabolic spring, Fatigue life, Cyclic loading, FEM, Strain-life theories
Cite: Nagendra and S K Srivastava, "Fatigue Life Prediction of Parabolic Spring Based on Strain Life Theories," International Journal of Mechanical Engineering and Robotics Research, Vol. 3, No. 1, pp. 320-326, January 2014.