Abstract
A new critical plane approach based on the modified Manson-Coffin curve method (MMCCM) is presented in this paper for predicting fatigue lifetime under variable amplitude (VA) multiaxial fatigue loading. The critical plane is assumed to coincide with that material plane experiencing the maximum variance of the resolved shear strain. Fatigue damage is hypothesized to be a function of both the amplitude of the resolved shear strain and the so-called critical plane stress ratio. The latter quantity depends on the mean value and the variance of the stress perpendicular to the critical plane as well as on the variance of the shear stress resolved along the direction experiencing the maximum variance of the resolved shear strain. Load cycles are counted from the resolved shear strain time history by using the classic rain flow counting method. Palmgren-Miner’s linear damage rule is applied to estimate cumulative fatigue damage. The accuracy and reliability of the proposed approach is checked by using several experimental data taken from the literature. The estimated fatigue lives based on the new approach are seen to be in sound agreement with the experimental results.
Highlights
Fatigue life prediction approaches based on the concept of the critical plane are generally accepted to be more accurate for multiaxial fatigue life estimation
The Maximum Variance Method (MVM) postulates that the critical plane can be defined as that plane containing the direction that experiences the maximum variance of the resolved shear stress
The present paper summarizes an attempt of extending the use of the Modified Manson-Coffin Curve Method (MMCCM) to those situations where complex variable amplitude loadings are involved
Summary
Fatigue life prediction approaches based on the concept of the critical plane are generally accepted to be more accurate for multiaxial fatigue life estimation. The Maximum Variance Method (MVM) postulates that the critical plane can be defined as that plane containing the direction (passing through the assumed critical point) that experiences the maximum variance of the resolved shear stress. The MMCCM is suggested here as being applied in conjunction with the maximum variance method (MVM) to estimate fatigue lifetime by directly post-processing the strain state relative to that material plane containing the direction along which the variance of the resolved shear strain is maximized. Eq (13) makes it evident that the determination of the direction experiencing the maximum variance of the resolved shear strain is a conventional multi-variable optimization problem It can be satisfactorily solved by using the so-called Gradient Ascent Method [19]. Can be evaluated, at any instant, t, of the load history, through the following relationship:
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
