Multiaxial Fatigue

In this note, the problem of the calibration of the Dang Van multiaxial fatigue criterion is addressed. The discussion is based on uniaxial fatigue tests performed with different stress ratios. Results show that the usual technique for calibrating the constants of the Dang Van criterion does not agree with experimental evidence, especially for negative stress ratios. For this reason, a different fatigue failure locus made of two straight line segments is proposed and typical three-dimensional rolling contact stress histories are analyzed using the traditional and proposed methods. Results show that the conventional technique does not agree with knowledge coming from shakedown approaches of rolling contact while the proposed method seems to constitute a more appropriate limit.

""A method for fatigue life assessment in high-cycle domain under multiaxial loading is presented in this paper. This approach allows fatigue assessment under any kind of load history, without limitations. The methodology lies on the construction - at a macroscopic level - of an “indicator” in the form of a set of cycles, representing plasticity that can arise at mesoscopic level throughout fatigue process. During the advancement of the loading history new cycles are created and a continuous evaluation of the damage is made.

Fatigue life prediction with failure probability estimation for materials subjected to multiaxial loading is an important task in engineering design because it reduces the financial cost by eliminating expensive experimental tests. Owing to the complex deterioration mechanisms of fatigue failure, existing fatigue life prediction models are of the empirical or semi-empirical type, and their applicability is limited to validating the loading condition and material. Improper selection of the fatigue model could result in non-conservative life prediction with high financial and catastrophic consequences. To solve this problem, an innovative approach based on the Gaussian process for fatigue life prediction under multiaxial loading is presented. The inherent features of the Gaussian process predispose its application to fatigue life prediction under multiaxial loading as an efficient and practical approach to avoid the problem in selecting adequate semi-empirical parametric fatigue models. The model was validated on two sets of experimental data obtained by fatigue testing of S355N steel and 2124 T851 aluminum alloy under uniaxial and multiaxial loadings. In the model training process, only data obtained under uniaxial and pure torsion cyclic loadings were applied. Owing to the implemented physics-based input data, which are related to the stress components acting on the critical plane of crack initiation, the model accurately predicted the fatigue lives of the two tested materials by implementing the squared exponential covariance function. In addition, the fatigue lives were also computed using four parametric fatigue strength criteria (Crossland, Matake, Carpinteri et al., and Papuga-Růžička models). The best results obtained by the parametric models exhibited a lower fatigue prediction performance than the results using the Gaussian process-based model.

The fatigue lives are reduced accompanying an additional cyclic hardening under strain controlled non-proportional cyclic loading in which principal directions of stress and strain are altered within a cycle. This study predicts non-proportional cyclic hardening and multiaxial fatigue life for several BCC and FCC metals under constant amplitude strain cycling. A novel procedure to determine non-proportional cyclic hardening form uniaxial tensile properties has discussed in this study. Standard plastic strain energy density based fatigue criteria with considering the non-proportional cyclic hardening effect successfully predicts multiaxial fatigue lives. The predictions of non-proportional cyclic hardening and multiaxial fatigue life through models are validated by experimental results of various BCC and FCC metals which are collected from literatures.

In the present study, the authors attempted to predict the fatigue lifetime of a real-scale integral concrete bridge with H-shaped steel piles resulting from working and environmental conditions. In this regard, various types of nonproportional variable amplitude loads were applied on the bridge, such as temperature variations and sea waves clash. To this end, CATIA software was used to model the real-scale bridge with its accessories, such as a concrete deck, concrete anchors (walls), I-shaped concrete beams (Ribs), and steel piles. Subsequently, stress analysis was performed to determine the critical area apt to fail. The results showed that steel piles are the most critical bridge components. As a result, in future analysis, the purpose will be to study this critical area, and the effect of relative humidity on the fatigue properties of concrete was ignored. Subsequently, the time history of stress tensor components in the critical area was obtained by performing transient dynamic analysis. Various well-known equivalent stress fatigue theories (von Mises, Findley, Dang Van, McDiarmid, Carpinteri–Spagnoli, Modified Findley, Modified McDiarmid, and Liu–Zenner) were utilized to calculate the equivalent stress caused by the simultaneous effect of temperature variations and sea waves clash. Eventually, the fatigue life of the structure was predicted by employing the rainflow counting algorithm and the Palmgren–Miner damage accumulation rule. The results indicated a reduction in the multiaxial fatigue life of the structure under the simultaneous effects of two phenomena, the daily temperature variations and the sea waves clash, of approximately 87% and 66%, respectively, compared with the fatigue life of the structure under either the effect of temperature changes or the effect of sea waves clash, separately. Therefore, it was necessary to consider all the cyclic loads in the structural design step to estimate the fatigue life of the structure. Moreover, the findings of this case study revealed that the lowest value of multiaxial fatigue lifetime is related to the application of the Liu-Zenner criterion. In other words, this criterion is more conservative than the other used criteria.

In the present study, the authors attempted to predict the fatigue lifetime of a real-scale integral concrete bridge with H-shaped steel piles resulting from working and environmental conditions. In this regard, various types of nonproportional variable amplitude loads were applied on the bridge, such as temperature variations and sea waves clash. To this end, CATIA software was used to model the real-scale bridge with its accessories, such as a concrete deck, concrete anchors (walls), I-shaped concrete beams (Ribs), and steel piles. Subsequently, stress analysis was performed to determine the critical area apt to fail. The results showed that steel piles are the most critical bridge components. As a result, in future analysis, the purpose will be to study this critical area, and the effect of relative humidity on the fatigue properties of concrete was ignored. Subsequently, the time history of stress tensor components in the critical area was obtained by performing transient dynami...

Fatigue failure occurring in most engineering components, generally is related to multiaxial loadings. Variation in principal axes of
stresses and strains in multiaxial loading causes additional hardening and this is assumed as the main reason of fatigue life decrease.
The origin of multiaxiality may have diverse reasons and may arise from multiaxial loading, complicated geometry or residual
stresses. In the present study various multiaxial fatigue criteria were applied for predicting fatigue life of an alloy and by using the
finite element method a hollow cylindrical specimen made of alloy GH4169 was simulated under strain controlled multi-axial
loading at high temperature. Hysteresis loops derived from simulation results and estimated life have been validated and compared
with reference sample experimental results. The results shows that approaches considering simultaneous effect of stress, strain and
additional hardening, especially at high temperature loading condition, could better predict the life. Among the presented criteria,
Fatemi-Kurath, Fatemi-Socie and energy criteria have closest predictions to experimental results.
Keywords: multiaxial fatigue, hysteresis loops, high temperature fatigue, low cycle fatigue

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