The Effect of Mean Stress and Mean Strain on Fatigue Damage Following Overloads

2003 ◽  
Author(s):  
A. E. Nolting ◽  
D. L. Duquesnay
Keyword(s):  
Fatigue Damage ◽  
Mean Stress ◽  
Mean Strain

scholarly journals Investigation of Changes in Fatigue Damage Caused by Mean Load under Block Loading Conditions

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2738
Author(s):  
Roland Pawliczek ◽  
Tadeusz Lagoda
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Strain Curve ◽  
Mean Value ◽  
Fatigue Properties ◽  
Stress Strain ◽  
Reference Case ◽  
Block Loading ◽  
The Mean ◽  
Mean Strain

The literature in the area of material fatigue indicates that the fatigue properties may change with the number of cycles. Researchers recommend taking this into account in fatigue life calculation algorithms. The results of simulation research presented in this paper relate to an algorithm for estimating the fatigue life of specimens subjected to block loading with a nonzero mean value. The problem of block loads using a novel calculation model is presented in this paper. The model takes into account the change in stress–strain curve parameters caused by mean strain. Simulation tests were performed for generated triangular waveforms of strains, where load blocks with changed mean strain values were applied. During the analysis, the degree of fatigue damage was compared. The results of calculations obtained for standard values of stress–strain parameters (for symmetric loads) and those determined, taking into account changes in the curve parameters, are compared and presented in this paper. It is shown that by neglecting the effect of the mean strain value on the K′ and n′ parameters and by considering only the parameters of the cyclic deformation curve for εm = 0 (symmetric loads), the ratio of the total degree of fatigue damage varies from 10% for εa = 0.2% to 3.5% for εa = 0.6%. The largest differences in the calculation for ratios of the partial degrees of fatigue damage were observed in relation to the reference case for the sequence of block n3, where εm = 0.4%. The simulation results show that higher mean strains change the properties of the material, and in such cases, it is necessary to take into account the influence of the mean value on the material response under block loads.

Fatigue Life Prediction of the Vulcanized Natural Rubber

2005 ◽  
Vol 297-300 ◽  
pp. 16-21
Author(s):  
Chang Su Woo ◽  
Wan Doo Kim ◽  
Jae Do Kwon ◽  
Wan Soo Kim
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Natural Rubber ◽  
Fatigue Damage ◽  
Material Model ◽  
Damage Parameter ◽  
Element Analysis ◽  
Critical Location ◽  
Lagrange Strain ◽  
Mean Strain

Fatigue lifetime prediction methodology of the vulcanized natural rubber was proposed by incorporating the finite element analysis and fatigue damage parameter determined from fatigue test. Finite element analysis of 3D dumbbell specimen of natural rubber was performed based on a hyper-elastic material model determined from the tension, compression and shear tests. Stroke controlled fatigue tests were conducted using fatigue specimens at different levels of mean strain. The Green-Lagrange strain at the critical location determined from the FEM was used for evaluating the fatigue damaged parameter of the natural rubber. It was shown that the maximum Green-Lagrange strain was proper damage parameter, taking the mean strain effects into account. Fatigue lives of the natural rubber are predicted by using the fatigue damage parameters at the critical location. Predicted fatigue lives of the natural rubber agreed fairly well the experimental fatigue lives a factor of two.

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.

Cycle-Dependent Stress Relaxation of A-286 Alloy

1960 ◽  
Vol 82 (3) ◽  
pp. 654-658 ◽  
Author(s):  
A. S. Ross ◽  
JoDean Morrow
Keyword(s):  
Fatigue Life ◽  
Material Behavior ◽  
Mean Stress ◽  
Fatigue Specimen ◽  
Fatigue Data ◽  
The Mean ◽  
Cycle Dependent ◽  
Mean Strain ◽  
Mean Stresses ◽  
Strain Cycling

When an axial fatigue specimen is subjected to repeated strain cycling about a fixed mean strain value, the mean stress decreases with the number of strain cycles. To explore this type of material behavior, tubular fatigue specimens of A-286 alloy have been axially tested under conditions of controlled strain, and the cycle-dependent relaxation of mean stress measured. Fatigue data for five initial mean stresses are also reported. It was found that, in the case of A-286 alloy, most of the relaxation occurred early in the fatigue life, especially during the first ten cycles.

scholarly journals Effects of Temperature on the Evolution of Yield Surface and Stress Asymmetry in A356–T7 Cast Aluminium Alloy

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7898
Author(s):  
Elanghovan Natesan ◽  
Johan Ahlström ◽  
Stefan Eriksson ◽  
Christer Persson
Keyword(s):  
Flow Stress ◽  
Aluminium Alloy ◽  
Internal Combustion Engines ◽  
Elevated Temperatures ◽  
Internal Combustion ◽  
Effect Of Temperature ◽  
Mean Stress ◽  
Cast Aluminium ◽  
Stress Asymmetry ◽  
Mean Strain

As the electrification of vehicle powertrains takes prominence to meet stringent emission norms, parts of internal combustion engines like cylinder heads are subjected to an increased number of thermal load cycles. The cost-effective design of such structures subjected to cyclic thermo-mechanical loads relies on the development of accurate material models capable of describing the continuum deformation behaviour of the material. This study investigates the effect of temperature on the evolution of flow stress under cyclic loading in A356-T7 + 0.5% Cu cast aluminium alloy commonly used in modern internal combustion engine cylinder heads. The material exhibits peak stress and flow stress asymmetry with the stress response and flow stress of the material under compressive loading higher than under tension. This peak and flow stress asymmetry decrease with an increase in temperature. To compare this stress asymmetry against conventional steel, cyclic strain-controlled fatigue tests are run on fully pearlitic R260 railway steel material. To study the effect of mean strain on the cyclic mean stress evolution and fatigue behaviour of the alloy, tests with tensile and compressive mean strains of +0.2% and −0.2% are compared against fully reversed (Rε = −1) strain-controlled tests. The material exhibits greater stress asymmetry between the peak tensile and peak compressive stresses for the strain-controlled tests with a compressive mean strain than the tests with an identical magnitude tensile mean strain. The material exhibits mean stress relaxation at all temperatures. Reduced durability of the material is observed for the tests with tensile mean strains at lower test temperatures of up to 150 °C. The tensile mean strains at elevated temperatures do not exhibit such a detrimental effect on the endurance limit of the material.

Numerical study of fatigue damage under random loading using Rainflow cycle counting

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Tayeb Kebir ◽  
José A.F.O. Correia ◽  
Mohamed Benguediab ◽  
Abilio M.P. De Jesus
Keyword(s):  
Fatigue Damage ◽  
Numerical Study ◽  
Scientific Work ◽  
Stress Effect ◽  
Mean Stress ◽  
Random Loading ◽  
Content Type ◽  
Rainflow Cycle Counting ◽  
The Mean ◽  
Rainflow Counting

PurposeThe purpose of this scientific work is to simulate the fatigue damage under random loading, taking into account the mean stress effect on fatigue lifetime and using the Rainflow counting technique to assess the fatigue damage by the Ansys software. The used material is aluminum alloy 6082-T6. A comparison with literature results has confirmed this investigation in this paper.Design/methodology/approachThe study of fatigue under random loading is based on the same concepts as constant loading with the addition of damage summation. The proportion of damage caused by a stress cycle depends not only on the alternating stress but also on the mean stress.FindingsAnalysis of the fatigue damage shows that the number of relative damage due to each cycle.Originality/valueThis paper aims to simulate the fatigue damage under random loading for aluminum alloys.

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