Metallic materials are extensively used in engineering structures and fatigue failure is one of the most common failure modes of metal structures. Fatigue phenomena occur when a material is subjected to fluctuating stresses and strains, which lead to failure due to damage accumulation. Different methods, including the Palmgren-Miner linear damage rule- (LDR-) based, multiaxial and variable amplitude loading, stochastic-based, energy-based, and continuum damage mechanics methods, forecast fatigue life. This paper reviews fatigue life prediction techniques for metallic materials. An ideal fatigue life prediction model should include the main features of those already established methods, and its implementation in simulation systems could help engineers and scientists in different applications. In conclusion, LDR-based, multiaxial and variable amplitude loading, stochastic-based, continuum damage mechanics, and energy-based methods are easy, realistic, microstructure dependent, well timed, and damage connected, respectively, for the ideal prediction model.

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A Review on Fatigue Life Prediction Methods for Metals

In this study, based on the Miner rule, a new linear damage accumu- lation rule is proposed to consider the strengthening and damaging of low amplitude loads with different sequences using fuzzy sets theory. This model improves the application of the traditional Miner rule, by considering not only the damaging and strengthening of low amplitude loads, but also the load sequence effects. To apply the proposed model, the law of selecting membership functions for differ- ent load spectra is found, and different membership functions are investigated to show the important influence on estimating fatigue life. Applicability of the method is validated by comparing with the experimental data. It is also found that the predicted fatigue life by the proposed method is more accurate and reliable than that by the traditional ones.

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Fatigue Life Estimation Considering Damaging and Strengthening of Low amplitude Loads under Different Load Sequences Using Fuzzy Sets Approach

We put forward a general procedure for assessment of damage evolution based on the concept of entropy production. The procedure is applicable to both constant- and variable amplitude loading. The results of a series of bending fatigue tests under both two-stage and three-stage loadings are reported to investigate the validity of the proposed methodology. Also presented are the results of experiments involving bending, torsion, and tension–compression fatigue tests with Al 6061-T6 and SS 304 specimens. It is shown that, within the range of parameters tested, the evolution of fatigue damage for these materials in terms of entropy production is independent of load, frequency, size, loading sequence and loading history. Furthermore, entropy production fractions of individual amplitudes sums to unity.

A thermodynamic approach to fatigue damage accumulation under variable loading

Fatigue design of engineering structures is typically based on lifetime calculation using a cumulative damage law. The linear damage rule by Miner is the universal standard for fatigue design even though numerous experimental studies have shown its deficiencies and possible non-conservative outcomes. In an effort to overcome these deficiencies, many nonlinear cumulative damage models and life prediction models have been developed since; however, none of them have found wide acceptance. This review article aims to provide a comprehensive overview of the state-of-the art in cumulative damage and lifetime prediction models for endurance based high-cycle fatigue design of metal structures.

https://biblio.ugent.be/publication/8689660/file/8689662.pdf

Cumulative damage and life prediction models for high-cycle fatigue of metals : a review

Fatigue is a damage accumulation process in which the material property deteriorates and degenerates continuously under cyclic loading. The analysis of damage accumulation plays a key role in preve...

A nonlinear fatigue damage accumulation model considering strength degradation and its applications to fatigue reliability analysis

A new energy-based life prediction framework for calculation of axial and bending fatigue results at various stress ratios has been developed. The purpose of the life prediction framework is to assess the behavior of materials used in gas turbine engines, such as Titanium 6Al-4V (Ti 6AI-4V) and Aluminum 6061-T6 (Al 6061-T6). The work conducted to develop this energy-based framework consists of the following entities: (1) a new life prediction criterion for axial and bending fatigue at various stress ratios for Al 6061-T6, (2) the use of the previously developed improved uniaxial energy-based method to acquire fatigue life prior to endurance limit region (Scott-Emuakpor et al., 2007, "Development of an Improved High Cycle Fatigue Criterion, " ASME J. Eng. Gas Turbines Power, 129, pp. 162-169), (3) and the incorporation of a probabilistic energy-based fatigue life calculation scheme to the general uniaxial life criterion (the first entity of the framework), which is capable of constructing prediction intervals based on a specified percent confidence level. The precision of this work was verified by comparison between theoretical approximations and experimental results from recently acquired Al 606-T6 and Ti 6Al-4V data. The comparison shows very good agreement, thus validating the capability of the framework to produce accurate uniaxial fatigue life predictions for commonly used gas turbine engine materials.

Herman Shen

Papers

An Energy-Based Uniaxial Fatigue Life Prediction Method for Commonly Used Gas Turbine Engine Materials

In situ study of static and dynamic strain energy density at notch roots and fatigue cracks using digital image correlation