13th International Conference on Fracture June 16–21, 2013, Beijing, China -7- stress acting on the maximum normal strain range plane. The extended Cruse-Meyer model is expressed as n mean B C f N A , ( ) 10 max σ εΔ = . (3) Obviously, this equation is identical with the original Cruse-Meyer model. In this work the parameters A and B are from the fitting of local strain-life curve of weldment at R = -1. And parameter C can be estimated at R = 0.1. In order to obtain the local stress and strain, FE computations were conducted for cyclic loadings with isotropic hardening assumed. Material properties were from previous analysis. Fig. 7 presents comparison between the predicted fatigue lifetime with the experimental results. All data are within the scatter band with a factor of 2. Figure 7. Fatigue life comparison results based on Cruse-Meyer model 4.2 Notched Fatigue Prediction Even under uniaxial cyclic loading, the presence of a hole will cause a local multiaxial stress fields near the notch root, axial and circumferencial strresses. Below the root surface the stress state is general bi-axial tensile loading mode, although the axial tensile stress dominates. Additionally, the stresses and strains vary with the distance substantially. Hence, the multiaxial fatigue models find application to analyze the problem. The prediction from the extended Cruse-Meyer model is listed in Table 3, based on the local stresses and strains at the notch root surface. The parameters ABC are taken from the previous smooth fatigue analysis. Obviously, the prediction is too conservative in comparing with experiments. Combining the extended Cruse-Meyer model with the critical distance method should improve the prediction. Two criteria, i.e. PM based and LM based, can be defined as d B C p d n mean N A ] [ ( ) 10 , max , σ εΔ = , (4)
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