A new approach to the investigation of load interaction effects and its application in residual fatigue life prediction

Abstract

Fatigue damage under variable amplitude loading is related to load histories, such as load sequences and load interactions. Many nonlinear damage models have been developed to present load sequences, but load interactions are often ignored. This paper provides a new approach to present load interaction effects for nonlinear damage accumulation. It is assumed that the ratio of two consecutive stress levels is used to describe the phenomenon on damage evolution. By introducing the approach to a nonlinear fatigue model without load interactions, a modified model is developed to predict the residual fatigue life under variable amplitude loading. Experimental data from three metallic materials and welded joints in the literature are employed to verify the effectiveness of the proposed method under two-level loading. The result shows that the modified model predicts more satisfactory estimations than the primary model and Miner rule. Furthermore, the proposed method is calibrated and validated by the case of multilevel loading. It is found that the modified model shows a good estimation and its damage curve presents a typical nonlinear behavior of damage growth. It is also convenient to calculate the residual fatigue life by the Wöhler curve.

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

“…The residual life fraction n 2 / N f 2 at σ 2 can be calculated by Previous researches have shown that the influence of load interaction can be well described by the load ratio. According to this, Peng et al developed a new prediction model of n 2 / N f 2 at σ 2 through modeling the fatigue damage evolution behavior as Combining Equations and , the residual life fraction at σ 2 under two block loadings is given by …”

“…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: …”

“…Previous researches have shown that the influence of load interaction can be well described by the load ratio. According to this, Peng et al 35 developed a new prediction model of n 2 /N f 2 at σ 2 through modeling the fatigue damage evolution behavior as…”

“…In this section, experimental data of P355NL1 steel and four other materials, including Al 2024 T42 alloy, 42 300CVN steel, 43 short carbon fiber reinforced polyetherether-ketone (CFR PEEK), 44 and 45 steel, 15 under two-block loadings are utilized for model validation and comparison. The five mentioned models 30,32,35,37,38 in Section 2 and the proposed one are utilized for a comparative study on nonlinear fatigue damage accumulation under two-block loadings. Correlations between experimental results (n 1 /N f 1 ) and the proposed model predictions (n 2 /N f 2 ) for these two block loadings (H-L and L-H) are presented in Figure 5, where the abscissa and the ordinate represent the life fractions spent at the first and second loading stress level, respectively.…”

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

“…The residual fatigue life depended on not only the effect of the loading sequence but also the loading history, especially the number of preloaded cycles. The existing models 9,33,[35][36][37] may be insufficient to account for the significant improvement of fatigue resistance induced by the previous low-amplitude fatigue loading history. Basaran et al [38][39][40][41][42][43][44][45][46][47] proposed a thermodynamic framework to describe the damage process of solid material under the fatigue loading.…”