scholarly journals Effects of Mean Stress and Prestrain on Fatigue-Damage Summation

2009 ◽  
pp. 93-93-12 ◽  
Author(s):  
TH Topper ◽  
BI Sandor
Keyword(s):  
Fatigue Damage ◽  
Mean Stress ◽  
Damage Summation

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.

Fatigue Damage Behavior of a Structural Component Made of P355NL1 Steel Under Block Loading

2009 ◽  
Vol 131 (2) ◽  
Author(s):  
Hélder F.S.G Pereira ◽  
Abílio M. P. De Jesus ◽  
Alfredo S. Ribeiro ◽  
António A. Fernandes
Keyword(s):  
Fatigue Damage ◽  
Structural Component ◽  
Stress Ratio ◽  
Sequence Effect ◽  
Block Loading ◽  
Fatigue Damage Accumulation ◽  
Load Sequence ◽  
Stress Ratios ◽  
Remote Stress ◽  
Damage Summation

The common design practice of pressure vessels subjected to variable amplitude loading is based on the application of a linear damage summation rule, also known as the Palmgren–Miner’s rule. Even though damage induced by small stress cycles, below the fatigue limit, are often taken into account in design codes of practice by two-slope stress-life curves, the sequential effects of the load history have been neglected. Several studies have shown that linear damage summation rules can predict conservative as well as nonconservative lives depending on the loading sequence. This paper presents experimental results about the fatigue damage accumulation behavior of a structural component made of P355NL1 steel, which is a material usually applied for pressure vessel purposes. The structural component is a rectangular double notched plate, which was subjected to block loading. Each block is characterized by constant remote stress amplitude. Two-block sequences were applied for various combinations of remote stress ranges. Three stress ratios were considered, namely, R=0, R=0.15, and R=0.3. Also, constant amplitude fatigue data are generated for the investigated structural component. In general, the block loading illustrates that the fatigue damage evolves nonlinearly with the number of load cycles and is a function of the load sequence, stress levels, and stress ratios. In particular, a clear load sequence effect is verified for the two-block loading, with null stress ratio. For the other (higher) stress ratios, the load sequence effect is almost negligible; however the damage evolution still is nonlinear. This suggests an important effect of the stress ratio on fatigue damage accumulation.

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.

Effect of ratcheting fatigue damage on the evolution of tensile properties of Al–Mg alloy

2019 ◽  
Vol 233 (14) ◽  
pp. 5033-5047 ◽  
Author(s):  
Pankaj Kumar ◽  
Bimal Das ◽  
Akhilendra Singh
Keyword(s):  
Tensile Properties ◽  
Fatigue Damage ◽  
Damage Evolution ◽  
Structural Integrity ◽  
Stress Amplitude ◽  
Cyclic Hardening ◽  
Mg Alloy ◽  
Tensile Behaviour ◽  
Aged Alloy ◽  
Mean Stress

This work aims to investigate the effect of damage accumulation on the evolution of tensile properties due to prior ratcheting fatigue in as-received and artificially aged conditions of Al–Mg alloy (AA 5754). Uniaxial asymmetric stress controlled tests for various combinations of mean stress and stress amplitude are performed at room temperature. Progressive degradation in the mechanical properties of structures and machines subjected to cyclic loading during service period can affect the structural integrity. In view of this, ratcheting fatigue tests are interrupted at various life fractions for particular mean stress and stress amplitude followed by tensile tests to understand the damage evolution during ratcheting for both conditions of alloy. Also, the effect of mean stress and stress amplitude on the post ratcheting tensile behaviour is analysed by conducting the ratcheting tests up to 150 cycles. Cyclic hardening is exhibited in the initial cycles followed by saturation for both as-received and artificially aged alloy. Ratcheting strain increases with the increase in both mean stress and stress amplitude. Drastic changes in tensile properties are noticed with ratcheting fatigue damage evolution for both conditions of alloy. The evolution of tensile properties due to prior loading history such as ratcheting fatigue can provide fundamental understanding in the design of structural components.

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 Correia ◽  
Mohamed Benguediab ◽  
Abilio M.P. de Jesus
Keyword(s):  
Fatigue Damage ◽  
Numerical Study ◽  
Hysteresis Loops ◽  
Scientific Work ◽  
Simulation Method ◽  
Stress Effect ◽  
Mean Stress ◽  
Random Loading ◽  
Content Type ◽  
The Mean

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.Design/methodology/approachThe study of fatigue under random loading is based on same concepts which as constant loading with addition of damage summation. The damage of materials due a stress cycle depends not only on the alternating stress but also on the mean stress.FindingsThe cycles counting simulation method allows quantifying the hysteresis loops, even if for small amplitude stresses.Originality/valueThe cycles are low or medium; the damage occurs most often, the higher values of alternating stresses cause the most failure of materials.

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