From the author’s recent studies, it was found that, in low/medium/high cycle fatigue(LHCF) regime, the Wöhler Curve Method is well suitably employed to perform the fatigue life assessment of metals, in which the stress-based intensity parameter calculation is based on the linear-elastic analysis. In this study, an attempt is made through many fatigue test data of notch components of metals from the literature to illustrate that, in LHCF regime, the Notch S-N Curve Method is well suitable for fatigue life analysis of notch components of metals, in which the stress-based intensity parameter calculation is based on the linear-elastic analysis. By concepts of the critical stress and the critical distance by Taylor and by two calibration fatigue failure curves of a smooth specimen and notch specimen by Susmel and Taylor, further, a local approach for predicting the notch S-N curve is proposed based the linear elastic stress fields ahead of notches. Accuracy of the Notch S-N Curve Method is proven by many fatigue test data of notch components of metals from the literature in LHCF regime.

In this letter, an attempt is made that, in low and extremely low cycle fatigue regime, applicability of the Wöhler Curve Method is examined using experimental fatigue data from the literature. The conclusion is that the Wöhler Curve Method is well suitable for fatigue life assessment of metallic materials in low and extremely low cycle fatigue regime.

Recently, the author specifically concerned with for low-cycle fatigue (LCF) of metals. An attempt was made that the well-known Wöhler Curve Method was used to perform LCF assessment of metals. From the author’s study, it is sure that the Wöhler Curve Method is well suitable for LCF life analysis of metals, in which the stress-based intensity parameter calculation is on the basis the linear-elastic analysis. In view of the fact that medium/high cycle fatigue lives of metals is well calculated by the Wöhler Curve Method, thus from the author’s study it appears to be possible that, for low/medium/high cycle fatigue (LHCF) of metals, the Wöhler Curve Method is well suitable for fatigue life assessment. This study specifically concern with such a subject. By using a number of the fatigue test data of metals from the literature, it has been proven that, in LHCF regime, the Wöhler Curve Method and the generalized Wöhler Curve Method are well suitably used to perform the fatigue life assessment of metals under uniaxial and multiaxial loading, respectively.

Recently, a description on a practicability of the Wöhler Curve Method for LCF of metallic materials was given by Yan. By the description and the low-cycle fatigue test data of 16MnR steel, it is important to illustrate that, for LCF of the metallic material, such a way that a “stress quantity” calculated based on the linear-elastic analysis is taken to be the stress intensity parameter, S, to establish a relationship between the stress intensity parameter, S, and the fatigue life, N, is practicable. In this study, many examples from the literature are given to illustrate that the Wöhler Curve Method is well suitable for LCF analysis of metallic materials

In this paper, it is important to illustrate that, for the LCF of metallic materials, a “stress quantity” calculated based on the linear-elastic analysis of the studied component is taken to be a mechanical quantity, S, to establish a relation of the mechanical quantity, S, to the fatigue life, N, is practicable. Based on the practicability, a prediction equation, for a low/medium/high cycle fatigue life assessment of metallic materials, is proposed. The prediction equation is a stress invariant based one, in which the computation of stress invariant is on the basis of the linear-elastic analysis of the studied component. Using experimental data of plain specimens reported in literature, it is proved that the prediction equation is both accurate and high efficient. In addition, the prediction equation in conjunction with the Theory of Critical Distances and linear-elastic notch mechanics are combined to establish the fatigue life estimation equation of the notched components. Finally, using experimental data of the fatigue life of 16MnR steel, validation verification of the notch fatigue life prediction equation is given.

The S-N equation is one of the most important equations in fatigue model investigation. A majority of fatigue models, including multiaxial fatigue model and mean effect models, are established on the basis of the S-N equation. Obviously, an accuracy of the S-N equation is very important. Taking into account that the S-N equation is, in fact, an empirical one in which the material constants are determined by numerical fitting fatigue experimental data, in this paper, the S-N equation can be improved, by further processing these fatigue experimental data, to present a new type of S-N equation that is more accurate than the S-N equation. The new type of S-N equation is called a similar S-N equation in this paper. By using a large number of experimental data of metallic materials reported in literature, an accuracy of the similar S-N equation has been proven.

On the basis of the multiaxial fatigue limit equation by Liu and Yan, a fracture equation of mixed mode crack is proposed in this note. By means of the test data on the mixed crack fracture reported in literature, the fracture equation has been verified to be not only simple in computation but also high in accuracy.

Many models of multiaxial fatigue limit under the bending and torsion loading have been reported in literature. In this paper, an attempt is made to extend the multiaxial fatigue limit models to finite fatigue life. Further these empirical models together with uniaxial S-N equations, including the axial S-N equation and torsion S-N equation, are used to perform multiaxial fatigue life assessment. By using a large number of experimental data of fatigue life reported in literature, an accuracy of these empirical models has been checked.

In this note, a linear mean stress model is presented on basis of the multiaxial model of fatigue life of metal materials proposed by Liu and Yan. By using the experimental data of fatigue life of metal materials reported in the literature, the model is systematically validated.