scholarly journals The elasto-plastic Point Method to estimate fatigue lifetime of notched metallic materials under variable amplitude multiaxial fatigue loading

2019 ◽  
Vol 300 ◽  
pp. 13004
Author(s):  
Namiq Zuhair Faruq ◽  
Luca Susmel
Keyword(s):  
Biaxial Loading ◽  
Fatigue Loading ◽  
Medium Carbon Steel ◽  
Multiaxial Fatigue ◽  
Point Method ◽  
Assessment Procedure ◽  
Fatigue Lifetime ◽  
Fatigue Assessment ◽  
Variable Amplitude ◽  
Strain Components

The present paper deals with the formulation and implementation of a novel fatigue lifetime estimation technique suitable for designing notched components against multiaxial fatigue. This fatigue assessment procedure was devised by combining the Modified Manson-Coffin Curve Method and the Shear Strain-Maximum Variance Method with the elasto-plastic Point Method. The accuracy of the approach being proposed was checked against a large number of experimental results that were generated by testing notched cylindrical samples of medium-carbon steel En8. These tests were run under proportional/non-proportional constant/variable amplitude biaxial loading, with the effect of non-zero mean stresses and different frequencies between the axial and torsional stress/strain components being also investigated. The results from this validation exercise demonstrate that the novel multiaxial fatigue assessment methodology being proposed is highly accurate, with its systematic usage resulting in predictions falling within an error factor of 2. This remarkable level of accuracy is very promising especially in light of the fact that this approach can be applied by directly post-processing the results from elasto-plastic Finite Element (FE) models solved using commercial codes.

scholarly journals A universal, damage-criterion-independent cycle counting method for multiaxial and variable amplitude fatigue

2019 ◽  
Vol 300 ◽  
pp. 17004
Author(s):  
K.G. F. Janssens
Keyword(s):  
Fatigue Damage ◽  
Fatigue Loading ◽  
Multiaxial Fatigue ◽  
Mean Stress ◽  
Counting Method ◽  
Damage Criterion ◽  
Variable Amplitude ◽  
Counting Procedure ◽  
Counting Methods ◽  
Set Up

None of the procedures for cycle-counting defined in the ASTM document with designation E1049-85 (Reapproved 2017) [1] are generally applicable to non-proportional, multi-axial Fatigue. In addition, as the concepts of amplitude and mean stress are defined per cycle, their values are dependent (or co-define) the cycle counting method. This poses an obvious problem to the analysis of non-proportional, multi-axial fatigue damage, as lifetime is, not in all but in many cases, an amplitude and mean stress dependent material property. Most of the newer cycle counting methods developed till date are at least inspired by the works of Wang & Brown [2] and of Bannantine & Socie [3], both of which are themselves still frequently used. Being built inspired by counting methods developed for uniaxial cycling, all of the approaches to date known to this author are limited in a way that is very well phrased by Anes et al [4], whom, on page 79 of their article, write that (quote): The damage criterion is the base stone to set up random fatigue. The damage parameter must capture the fatigue damage behavior to allow set up a cycle counting method and an accumulation model. Challenging this statement, a new cycle counting procedure is presented that is completely independent of the damage criterion, and universally works from the simplest uniaxial experiment, to the most complex, variable amplitude and frequency, non-proportional multiaxial fatigue loading. The definition of this new cycle counting concept is surprisingly simple. Despite of its simplicity, the new cycle counting procedure has different advantages when compared to the procedures known to date. Its standalone definition, allows it to be combined with any damage criterion. It does not require periodicity of the loading cycle, and can therefore be straightforwardly used to analyze variable frequency and amplitude, multiaxial fatigue loading.

scholarly journals A Multiaxial Notch Fatigue Methodology to Estimate In-Service Lifetime of Corroded Cast Iron Water Pipes

2013 ◽  
Vol 577-578 ◽  
pp. 125-128
Author(s):  
W. Brevis ◽  
Luca Susmel ◽  
J.B. Boxall
Keyword(s):  
Cast Iron ◽  
Fatigue Damage ◽  
Fatigue Loading ◽  
Multiaxial Fatigue ◽  
Variable Amplitude ◽  
Water Pipes ◽  
Service Lifetime ◽  
Curve Method ◽  
Over Time

The present paper summarises an attempt of using the so-called Modified Wöhler Curve Method (MWCM) to estimate fatigue damage in pitted cast iron water pipes subjected to in-service variable amplitude multiaxial fatigue loading. In this setting, pits are treated as hemispherical/hyperbolic notches whose depth increases over time due to conventional corrosion processes taking places in buried cast-iron pipes. The validity of such an approach is proven by showing, through a case study, that, under particular circumstances, the combined effect of corrosion and fatigue can remarkably shorten the in-service lifetime of cast-iron pipes as observed in the case study.

scholarly journals Equi-Biaxial Loading Effect on Austenitic Stainless Steel Fatigue Life

2014 ◽  
Author(s):  
S. Bradaï ◽  
C. Gourdin ◽  
S. Courtin ◽  
J. C. Le Roux ◽  
C. Gardin
Keyword(s):  
Experimental Data ◽  
Fatigue Life ◽  
Nuclear Power ◽  
Biaxial Loading ◽  
Biaxial Tension ◽  
Strain Tensor ◽  
Austenitic Stainless Steels ◽  
Fatigue Loading ◽  
Fatigue Lifetime ◽  
Biaxial Fatigue

Fatigue lifetime assessment is essential in the design of structures. Under-estimated predictions may result in unnecessary in service inspections. Conversely, over-estimated predictions may have serious consequences on the integrity of structures. In some nuclear power plant components, the fatigue loading may be equi-biaxial because of thermal fatigue. So the potential impact of multiaxial loading on the fatigue life of components is a major concern. Meanwhile, few experimental data are available on austenitic stainless steels. It is essential to improve the fatigue assessment methodologies to take into account the potential equi-biaxial fatigue damage. Hence this requires obtaining experimental data on the considered material with a strain tensor in equi-biaxial tension. The aim of this paper is to present the experimental results obtained with a device “FABIME2” developed in the LISN in collaboration with EDF and AREVA. The specimen geometry is optimized by FEM (Cast3M) simulation in order to obtain a stress concentration localized in the central region during the test. This device allows accurate quantification of the effects of both equi-biaxial strain state as well as structure (such as mean stress) on the fatigue life.

Multiaxial fatigue assessment for outer cylinder of landing gear by critical plane method

2021 ◽  
pp. 095441002110260
Author(s):  
Yingyu Wang ◽  
Xiaofan Zhang ◽  
Xingliang Dong ◽  
Weixing Yao
Keyword(s):  
Outer Cylinder ◽  
Fatigue Loading ◽  
Landing Gear ◽  
Multiaxial Fatigue ◽  
Critical Plane ◽  
Proportional Loading ◽  
Fatigue Lifetime ◽  
Plane Method ◽  
Multiaxial Stress State ◽  
Maximum Variance

The in-service loadings on the landing gear are usually complex and from different directions, which lead to the fatigue critical locations in the landing gear structure mostly in multiaxial stress state. A methodology based on the critical plane method was proposed for estimating the fatigue lifetime of outer cylinder of the main landing gear undergoing variable amplitude (VA) multiaxial proportional loading. The orientation of the critical plane was determined by the so-called maximum variance method. The Bannantine–Socie’s cycle counting method and Miner’s linear rule were applied with Zhang–Yao’s criterion in this research. The calculated results on the fatigue lifetime of the outer cylinder were compared with the experimental data. The results indicate that the methodology proposed in this article is a sound method for fatigue life prediction of engineering components bearing complex VA multiaxial fatigue loading.

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