Computational modeling of multiaxial elasto-plastic stress–strain response for notched components under non-proportional loading

A new computational methodology is proposed for fatigue life prediction of notched components subjected to variable amplitude multiaxial loading. In the proposed methodology, an estimation method of non‐proportionality factor (F) proposed by authors in the case of constant amplitude multiaxial loading is extended and applied to variable amplitude multiaxial loading by using Wang‐Brown's reversal counting approach. The pseudo stress correction method integrated with linear elastic finite element analysis is utilized to calculate the local elastic‐plastic stress and strain responses at the notch root. For whole local strain history, the plane with weight‐averaged maximum shear strain range is defined as the critical plane in this study. Based on the defined critical plane, a multiaxial fatigue damage model combined with Miner's linear cumulative damage law is used to predict fatigue life. The experimentally obtained fatigue data for 7050‐T7451 aluminium alloy notched shaft specimens under constant and variable amplitude multiaxial loadings are used to verify the proposed methodology and equivalent strain‐based methodology. The results show that the proposed methodology is superior to equivalent strain‐based methodology.

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Multiaxial notch fatigue life prediction based on pseudo stress correction and finite element analysis under variable amplitude loading

Tao

Shang

Sun

et al. 2018

“…In stage I, shear stress is the dominant factor of damage development, while the normal stress on θ crI should also be taken into account in the meantime. Most existing damage parameters based on the critical plane theory are the combinations of these two parameters, such as MacDiarmid's parameter, Zhang–Yao criterion and Ince–Glinka criterion . Because there are two sub‐stages in stage I and these two sub‐stages have been experimentally observed to be different, the influence of normal stress and shear stress in these two sub‐stages should be different.…”

Section: Accumulative Damage Modelsmentioning

confidence: 99%

“…Most existing damage parameters based on the critical plane theory are the combinations of these two parameters, such as MacDiarmid's parameter, 27 Zhang-Yao criterion 28 and Ince-Glinka criterion. 29,30 Because there are two substages in stage I and these two sub-stages have been experimentally observed to be different, the influence of normal stress and shear stress in these two sub-stages should be different. Therefore, the influences of shear stress and normal stress are respectively quantified as follows:…”

Section: The Proposed Modelmentioning

confidence: 99%

Study on the accumulative fatigue damage rules under multiaxial two‐stage step spectra constructed by loadings with similar lives

Xia

Yao

et al. 2015

In this paper, the influence on the multiaxial fatigue damage accumulation caused by loading path variation was studied. For 2024‐T4 aluminium alloy, the damage evolution during the entire life was first observed. On the basis of the observation, the stage I of fatigue damage evolution was further divided into two sub‐stages, and the dominant stress parameters of these two sub‐stages were proposed. Taking the dominant stress parameters into account, a phased accumulative fatigue damage model was proposed. Then, 12 multiaxial two‐stage step spectra constructed by loadings with approximately identical fatigue lives were carried out on 2024‐T4 aluminium alloy. The accumulative fatigue damage was calculated by the proposed model, and another five commonly used models and the calculated results were compared. According to the comparison, the newly proposed model had the most accurate results with the smallest scatter.

“…Multiaxial loading paths can produce complex stress‐strain responses at the notch area and cause a fatigue failure problem at or near the notch root . In order to satisfy the increasing design requirement for notched components in accordance with lifetime expectancy, light weight, and cost reduction, an efficient and reliable numerical methodology to the fatigue life predictions of practical notched components is urgently needed …”

Section: Introductionmentioning

confidence: 99%

Notch fatigue life prediction considering nonproportionality of local loading path under multiaxial cyclic loading

Tao

Zhang

Zhu

et al. 2019

An innovative numerical methodology is presented for fatigue lifetime estimation of notched bodies experiencing multiaxial cyclic loadings. In the presented methodology, an evaluation approach of the local nonproportionality factor F for notched specimens, which defines F as the ratio of the pseudoshear strain range at 45° to the maximum shear plane and the maximum shear strain range, is proposed and discussed deeply. The proposed evaluation method is incorporated into the material cyclic stress‐strain equation for purpose of describing the nonproportional hardening behavior for some material. The comparison between multiaxial elastic‐plastic finite element analysis (FEA) and experimentally measured strains for S460N steel notched specimens shows that the proposed nonproportionality factor estimation method is effective. Subsequently, the notch stresses and strains calculated utilizing multiaxial elastic‐plastic FEA are used as input data to the critical plane‐based fatigue life prediction methodology. The prediction results are satisfactory for the 7050‐T7451 aluminum alloy and GH4169 superalloy notched specimens under multiaxial cyclic loading.