In-Phase and Out-of-Phase Multiaxial Fatigue

1991 ◽  
Vol 113 (1) ◽  
pp. 112-118 ◽  
Author(s):  
F. Ellyin ◽  
K. Golos ◽  
Z. Xia
Keyword(s):  
External Pressure ◽  
Damage Parameter ◽  
Multiaxial Fatigue ◽  
Pressure Vessel Steel ◽  
Proportional Loading ◽  
Vessel Steel ◽  
Total Strain Energy Density ◽  
Number Of Cycles ◽  
Life Predictions ◽  
Cycles To Failure

In this investigation, thin-walled circular cylindrical specimens fabricated from a low alloy pressure vessel steel (ASTM A-516 Gr. 70) were subjected to various multiaxial loading conditions. The tests were conducted under strain-controlled condition, and loading was provided through an axial actuator and internal and external pressure across the specimen wall. Four in-plane strain ratios (ρ = Δεt/Δεa) were tested, and the most damaging case was the equi-biaxial in-plane straining, ρ = 1. For the latter condition, 90 deg out-of-phase loading was also investigated. These tests indicated a dramatic decrease in the number of cycles to failure, Nf, as a result of out-of-phase loading. The influence of the plastic strain path on life is thus clearly demonstrated. It is shown that the total strain energy density, ΔWt = ΔWe+ + ΔWp, correlates with both the in-phase and out-of-phase cyclic tests, and therefore is a proper damage parameter to be used for life predictions. A brief description of how ΔWt can be calculated is given for the case of proportional loading. The predicted results are compared with the experimental data, and the agreement is found to be very good indeed.

Life Prediction of Notched Components

1995 ◽  
Vol 117 (1) ◽  
pp. 50-55 ◽  
Author(s):  
M. Giglio ◽  
L. Vergani
Keyword(s):  
Strain Energy ◽  
Fem Analysis ◽  
Fatigue Tests ◽  
Pressure Vessel Steel ◽  
Total Strain Energy ◽  
Vessel Steel ◽  
Number Of Cycles ◽  
Experimental Values ◽  
Cycles To Failure ◽  
Notched Components

In this study, keyhole and smooth specimens, made from a low alloy pressure vessel steel (ASTM A-533 grade B), were subjected to monoaxial fatigue tests. The results show the influence of the stress concentration factor, Kt, on the number of cycles to failure, Nf. Total strain energy per cycle, ΔWt = ΔWp + ΔWe, was proved to be a good parameter for predicting the life of notched components. Elasto-plastic FEM analysis, utilizing the cyclic and monotonic curve of the material, showed close agreement with the experimental values.

Multiaxial Fatigue of 16MnR Steel

2008 ◽  
Vol 131 (2) ◽  
Author(s):  
Zengliang Gao ◽  
Tianwen Zhao ◽  
Xiaogui Wang ◽  
Yanyao Jiang
Keyword(s):  
Pure Shear ◽  
Ambient Air ◽  
Shear Loading ◽  
Multiaxial Fatigue ◽  
Experimental Results ◽  
Pressure Vessel Steel ◽  
Critical Plane ◽  
Cracking Behavior ◽  
Vessel Steel ◽  
Axial Torsion

Uniaxial, torsion, and axial-torsion fatigue experiments were conducted on a pressure vessel steel, 16MnR, in ambient air. The uniaxial experiments were conducted using solid cylindrical specimens. Axial-torsion experiments employed thin-walled tubular specimens subjected to proportional and nonproportional loading. The true fracture stress and strain were obtained by testing solid shafts under monotonic torsion. Experimental results reveal that the material under investigation does not display significant nonproportional hardening. The material was found to display shear cracking under pure shear loading but tensile cracking under tension-compression loading. Two critical plane multiaxial fatigue criteria, namely, the Fatemi–Socie criterion and the Jiang criterion, were evaluated based on the experimental results. The Fatemi–Socie criterion combines the maximum shear strain amplitude with a consideration of the normal stress on the critical plane. The Jiang criterion makes use of the plastic strain energy on a material plane as the major contributor to the fatigue damage. Both criteria were found to correlate well with the experiments in terms of fatigue life. The predicted cracking directions by the criteria were less satisfactory when comparing with the experimentally observed cracking behavior under different loading conditions.

scholarly journals New research findings on non-proportional low cycle fatigue

2019 ◽  
Vol 300 ◽  
pp. 08003
Author(s):  
Anghel Cernescu ◽  
Rhys Pullin
Keyword(s):  
Low Cycle Fatigue ◽  
Strain Range ◽  
Material Constant ◽  
Multiaxial Fatigue ◽  
Shear Strain Rate ◽  
Proportional Loading ◽  
New Research ◽  
Life Predictions ◽  
Multiaxial Loadings ◽  
Additional Hardening

One of the challenges regarding multiaxial fatigue damage predictions is non-proportional loading. Relevant studies have shown that these multiaxial loadings cause significant additional hardening and reduction in durability due to non-proportionality. Fatigue life predictions due to non-proportional loadings are based on an equivalent non-proportional strain range that considers a material constant related to additional hardening and a non-proportionality factor. In this paper an analysis of the non-proportional factor for three multiaxial loadings forming a square in γ/√3 – ε coordinates is carried out. One of the observations revealed by this analysis is the sensitivity of the non-proportional factor to variable shear strain rate.

scholarly journals Taking into account the non-proportional loading effect on high cycle fatigue life predictions obtained by invariant-based approaches

2019 ◽  
Vol 300 ◽  
pp. 12003
Author(s):  
Lorenzo Bercelli ◽  
Cédric Doudard ◽  
Sylvain Moyne
Keyword(s):  
High Cycle Fatigue ◽  
Equivalent Stress ◽  
Multiaxial Fatigue ◽  
Proportional Loading ◽  
Industrial Structures ◽  
Complete Chain ◽  
Stress Signals ◽  
Definition Of ◽  
Life Predictions ◽  
Fatigue Criterion

Industrial structures are often subjected to multiaxial fatigue loadings. If the multiple stress signals are not synced the loading is said to be non-proportional. Most of the multiaxial fatigue criteria give highly inaccurate lifetime predictions when used in the case of such loadings. The scalar equivalent stress defined by the criteria does not take into account the non-proportional nature of the multiaxial loading and leads to non-conservative predictions. Moreover a multiaxial fatigue criterion can only be applied on a stress cycle which has no clear definition when multiple unsynced signals are to be considered. This study addresses these issues by proposing a correction of an invariant based multiaxial fatigue criterion through the definition of a non-proportional degree indicator. A definition of multiaxial cycle is also given based on the Wang-Brown method. Finally a complete chain of invariant based lifetime prediction for non-proportional multiaxial fatigue is validated.

scholarly journals Effect of Shear/Axial Stress Ratio on Multiaxial Non-Proportional Loading Fatigue Damage on AISI 303 Steel

Metals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 89
Author(s):  
Vitor Anes ◽  
Luis Reis ◽  
Manuel Freitas
Keyword(s):  
Stress Ratio ◽  
Axial Stress ◽  
Experimental Program ◽  
Shear Stresses ◽  
Normal Stresses ◽  
Proportional Loading ◽  
Varied Range ◽  
Number Of Cycles ◽  
The Relationship ◽  
Cycles To Failure

In this paper, we investigate the cyclic response of AISI 303 stainless steel subjected to non-proportional loads with different amplitude ratios between shear stresses and normal stresses. Based on the experiments, a relationship between the proportional reference load and a varied range of non-proportional loads was established. To achieve this objective, an experimental program was implemented to evaluate the non-proportional parameter Y. Then, the evolution of this parameter was analyzed with the number of cycles to failure and with the ratio between shear and normal stresses, finally, the evolution of the non-proportional parameter Y was mapped by two functions. The results show that the non-proportional response of the AISI 303 can be estimated using the two functions obtained. This allows the estimation of the relationship between non-proportional and proportional stresses as a function of the number of cycles to failure together with the relationship between shear and normal stresses. The results obtained have direct application in the evaluation of accumulated damage, assessed in real-time, resulting from variable amplitude loading spectra. This is of particular interest for the evaluation of structural health monitoring of structures and mechanical components.

A General Criterion for Low-Cycle Multiaxial Fatigue Failure

1989 ◽  
Vol 111 (3) ◽  
pp. 263-269 ◽  
Author(s):  
A. Makinde ◽  
K. W. Neale
Keyword(s):  
Shear Strain ◽  
Fatigue Failure ◽  
Low Cycle Fatigue ◽  
Multiaxial Fatigue ◽  
General Criterion ◽  
Cycle Fatigue ◽  
Maximum Shear Strain ◽  
Number Of Cycles ◽  
New Criterion ◽  
Cycles To Failure

A new, general criterion is proposed for multiaxial low-cycle fatigue failure. Contours of constant fatigue life on a plot of maximum shear strain against the tensile strain acting normal to the plane of maximum shear strain are represented by a parametric criterion of the form g(θ,Nf)=kf1(θ)f2(Nf). Here g is the magnitude of the vector from the origin to a point on the constant life contour, θ is the angle associated with g in this space, Nf is the number of cycles to failure, k is a constant and f1 (θ) and f2(Nf) are two separate functions of θ and Nf, respectively. It is shown that all previously proposed macroscopic criteria are particular cases of the failure function g(θ, Nf). Experimental results from several authors are analyzed using the new criterion.

scholarly journals Multiaxial fatigue strength under non-proportional loading of additively manufactured notched components of Ti-6Al-4V

2019 ◽  
Vol 300 ◽  
pp. 03005 ◽  
Author(s):  
Stefano Bressan ◽  
Javad Razavi ◽  
Fumio Ogawa ◽  
Takamoto Itoh ◽  
Filippo Berto
Keyword(s):  
Heat Treatment ◽  
Strain Path ◽  
Fatigue Tests ◽  
Multiaxial Fatigue ◽  
Plastic Behavior ◽  
Proportional Loading ◽  
Material Microstructure ◽  
Powder Bed ◽  
Layer Orientation ◽  
Number Of Cycles

In this study fatigue tests have been conducted on additively manufactured notched specimens made of titanium alloy Ti-6Al-4V under uniaxial loading and multiaxial non-proportional loading. Laser powder bed fusion technique has been employed to fabricate cylindrical specimens which have been successively machined to obtain a circumferential notch. Four varieties of specimens were fabricated depending on the build orientation and the application of a post-fabrication stress-relief heat treatment. The influence of layer orientation and heat treatment on the material microstructure has been analyzed. Strain controlled tests were performed with both proportional loading represented by a push-pull strain path and non-proportional loading represented by a circle strain path. The number of cycles to failure under both proportional and non-proportional loadings seemed not depending on layer orientation and heat-treatment. The cyclic plastic behavior of the material has been verified through the observation of the softening and hardening curves. The surface of the crack has been finally analyzed to verify the crack initiation position which has been detected on voids or defects located in the vicinity of the notch tip.

A Total Strain Energy Density Theory for Cumulative Fatigue Damage

1988 ◽  
Vol 110 (1) ◽  
pp. 36-41 ◽  
Author(s):  
K. Golos ◽  
F. Ellyin
Keyword(s):  
Energy Density ◽  
Strain Energy Density ◽  
Strain Energy ◽  
Elastic Strain Energy ◽  
Cumulative Damage ◽  
Total Strain ◽  
Pressure Vessel Steel ◽  
Total Strain Energy ◽  
Vessel Steel ◽  
Total Strain Energy Density

A unified theory based on the cyclic strain energy density criterion is presented first. It is shown that the fatigue failure in both low and high-cycle regimes, and cumulative damage and loading sequence, can all be expressed in terms of a single damage parameter. The damage criterion is based on the total strain energy density per cycle (sum of the plastic and tensile elastic strain energy). Both the crack initiation and propagation phases of the fatigue life are embodied in this approach. A systematic investigation into the cyclic, fatigue and cumulative damage behavior of the pressure vessel steel, A-516 Gr. 70, is subsequently presented. The comparison between the predicted and experimental results is found to be good.

Nondestructive estimation of remaining fatigue life without the loading history

2019 ◽  
Vol 29 (3) ◽  
pp. 482-502 ◽  
Author(s):  
JY Jang ◽  
M Mehdizadeh ◽  
MM Khonsari
Keyword(s):  
Fatigue Life ◽  
Damage Parameter ◽  
Nondestructive Method ◽  
Loading History ◽  
Number Of Cycles ◽  
Life Predictions ◽  
Short Time ◽  
Remaining Fatigue Life ◽  
Nondestructive Estimation ◽  
Good Agreement

A new nondestructive method to estimate the remaining fatigue life of a fatigue specimen with unknown knowledge of the loading history is presented. It requires only one short-time excitation test. The method utilizes the concept of damage parameter and the temperature rise to reliably predict the remaining number of cycles before fracture. A generalized procedure and numerous experimentally verified examples are presented. It is shown that the method can be applied to both constant and variable stress levels. Extensive laboratory tests reveal that the results of the remaining fatigue life predictions are in very good agreement with measurements.

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