Session: 13-12-01: Modeling of the Fracture, Failure, and Fatigue in Solids I

Paper Number: 168249

An Energy-Based Predictor for Uniaxial, Pure Shear, and Multiaxial Fatigue Life in Metals 

An energy-based fatigue life predictor combining the shear stress and strain ranges on the critical plane of the maximum shear strain amplitude and the normal stress and strain ranges has been proposed to predict multiaxial fatigue life, as well as uniaxial and pure shear fatigue life. The proposed predictor employs a weight factor to account for the different effects of shear and normal terms on fatigue life. The shear strain and stress ranges on the critical plane are taken into account, while the ranges of positive normal stress and strain occurring perpendicular to the critical plane are considered, since compressive normal stress and strain do not significantly contribute to fatigue damage. To evaluate the fatigue predictor, the fatigue life of four different metal materials - SS400 carbon steel, GH4169 super alloy, TC4 titanium alloy, and 7075-T651 aluminum alloy - was predicted using not only the proposed predictor but also the Fatemi-Socie, Smith-Watson-Topper, and Findley fatigue predictors. Uniaxial and mixed-mode tests were conducted on SS400 carbon steel to investigate the effects of shear stress and strain. For the other materials, fatigue test data, including uniaxial, pure shear, and multiaxial fatigue tests, were obtained from the literature. Finite element simulations were conducted to calculate the fatigue predictors. The SS400 material was modeled using a combined isotropic/kinematic hardening model, and an optimization algorithm was proposed for the material parameters. The optimization algorithm was developed by categorizing the possible scenarios into four cases when comparing the simulation results with the test results and modifying the corresponding parameters for each case. When cyclic loading was applied to a dog-bone-shaped specimen, buckling occurred. To simulate this, a buckling analysis was conducted, and geometric inhomogeneity was applied to the finite element model of the dog-bone-shaped specimen using the mode shape obtained from the buckling analysis results. For the other materials, finite element analysis was carried out using the material properties provided in the literature. The comparison of the fatigue predictors for the four different materials demonstrated that the proposed predictor provides better fatigue life predictions for uniaxial, pure shear, and multiaxial fatigue tests. The Smith-Watson-Topper predictor does not accurately predict the life of pure shear fatigue test data, whereas the proposed predictor shows good agreement for all fatigue test data with cycles ranging from 500 to 100,000. The other predictors provide better predictions than the Smith-Watson-Topper predictor. However, they do not perform well in the range where the life is below 1,000 cycles.

Presenting Author: Wonho Lee Sogang University

Presenting Author Biography: N/A

Authors:

Jinwoo Park Sogang University
Wonho Lee Sogang University
Hyun-Yong Jeong Sogang University