Formulation of gradient multiaxial fatigue criteria

ABSTRACT. The present study aims to develop an algorithm able to predict the fatigue lifetime of nitrided steels. Linear multi-axial fatigue criteria are used to take into account the gradients of mechanical properties provided by the nitriding process. Simulations on rotating bending fatigue specimens are made in order to test the nitrided surfaces. The fatigue model is applied to the cyclic loading of a gear from a simulation using the finite element software Ansys. Results show the positive contributions of nitriding on the fatigue strength.

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“…During this study, the choice has been made to select the linear criterion in the following form [6,7]:…”

Section: Multiaxial Fatigue Criteriamentioning

confidence: 99%

Fatigue modelling for gas nitriding

Weil¹,

Jegou²,

Barrallier³

2016

Frattura Ed Integrità Strutturale

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“…It also facilitates consistent extensions to cope with anisotropic fatigue [12] as well as to include stress gradient effects [13], for alternative approaches see e.g. [14,15]. Here, extension to handle also low-cycle fatigue is described.…”

Section: Introductionmentioning

confidence: 99%

A continuum based macroscopic unified low-and high cycle fatigue model

et al. 2019

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In this work, an extension of a previously developed continuum based high-cycle fatigue model is enhanced to also capture the low-cycle fatigue regime, where significant plastic deformation of the bulk material takes place. Coupling of the LCF-and HCF-models is due to the damage evolution equation. The high-cycle part of the model is based on the concepts of a moving endurance surface in the stress space with an associated evolving isotropic damage variable. Damage evolution in the low-cycle part is determined via plastic deformations and endurance function. For the plastic behaviour a non-linear isotropic and kinematic hardening J2-plasticity model is adopted. Within this unified approach, there is no need for heuristic cycle-counting approaches since the model is formulated by means of evolution equations, i.e. incremental relations, and not changes per cycle. Moreover, the model is inherently multiaxial and treats the uniaxial and multiaxial stress histories in the same manner. Calibration of the model parameters is discussed and results from some test cases are shown. *

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“…Even though several models considering the size effect and the gradient effect are available, just a few of them [12][13][14] incorporate both effects in a combined manner as discussed in [15]. Moreover, the role of material defects is most of the time investigated by considering the most critical one and by applying a deterministic criterion like in the work of Murakami [2].…”

Section: Introductionmentioning

confidence: 99%

HCF of AA7050 alloy containing surface defects: Study of the statistical size effect

Abroug

Pessard

Germain

et al. 2018

International Journal of Fatigue

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This work investigates the effect of artificial surface defects on the fatigue limit of a 7050 Aluminum alloy (Al Zn6CuMgZr). A large fatigue testing campaign under fully reversed plane bending loading is undertaken on specimen with artificial surface hemispherical defects. The defect number was varied from 1 to 44 defects per specimen and the diameter size ranged from 60 μm to 800 μm. The test results allow the characterization of both the defect effect and scale effect on the fatigue behavior of the material. A probabilistic approach based on the weakest link concept together with a fatigue crack initiation criterion are used to account for the stress distribution and the size of the highly stressed volume. This approach leads to a probabilistic Kitagawa-Takahashi type diagram, which in this case explains the relationship between the defect size and the scale effect on the fatigue strength. The predictions show good agreement with the experimental results and illustrate the importance of taking the scale effect into account when designing components containing different surface defects types or roughness patterns.

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Formulation of gradient multiaxial fatigue criteria

Cited by 21 publications

References 20 publications

Fatigue modelling for gas nitriding

Fatigue modelling for gas nitriding

A continuum based macroscopic unified low-and high cycle fatigue model

HCF of AA7050 alloy containing surface defects: Study of the statistical size effect

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