A modified nonlinear fatigue damage accumulation model

Abstract

This paper presents a modified nonlinear fatigue damage accumulation model accounting for load interaction effects. The original model is based on physical property degradation of materials, from which the load interaction effects are ignored. However, the load interaction effects have a significant influence on the fatigue life. In the study, by analyzing five damage models, a load interaction parameter is obtained and added to the original model. Experimental work is then carried out to verify the modified model of four categories of experimental data from smooth and notch specimens under two-level stress loading. Moreover, comparison is made among the results calculated by the test data, the Miner’s rule, the original model, and the modified model.

Residual fatigue life prediction based on a novel damage accumulation model considering loading history

“…The residual life of the K417 alloy under LH loading path was estimated using the proposed and existing models . It should be pointed out that the physical materials of K417 at 750 and 850°C were introduced into the physics based model (Equation ) due to the lack of experimental data.…”

“…Ye‐Wang model accounted for the effect of loading sequence and could be applied conveniently in engineering using equivalent‐loading postulate. Lv et al pointed out that the effect of load interaction had a significant influence on the residual fatigue life and modified Ye‐Wang model by introducing a loading interaction factor: …”

Nonlinear fatigue damage accumulation and life prediction of metals: A comparative study

“…Then, Equation can be simplified as The two‐block loading spectrum which is of special interest to test nonlinear damage models, is normally defined by the applied high and low stress amplitude blocks, respectively, during n H and n L loading cycles. Lv et al presented a new damage accumulation model by extending the Ye‐Wang model for fatigue analysis under variable amplitude loadings. For two‐block loadings, by introducing the equivalent fatigue damage concept, the residual life fraction under the second block can be obtained by where n 1 and n 2 represent the number of cycles at the two loading stress levels, respectively, and N f 1 and N f 2 stand for fatigue life at the corresponding loading stress level.…”

“…As aforementioned, this effect will produce extra damage behavior with influence on residual life, which often leads to overestimated fatigue life. According to this, Lv et al introduced an interaction factor σ 1 / σ 2 into the damage exponent of Equation where σ 1 and σ 2 are the two stresses characterizing the two‐block loadings.…”

“…In addition, the number of damage nuclei produced by different loading stress levels will lead to the change of damage accumulation, and this effect will increase with the larger difference between the stress levels. In this regard, similar to the work, a load ratio is introduced to describe the load interaction effects under two‐block loadings: …”