Multiaxial Fatigue Under Variable Amplitude Loads

1999 ◽  
Vol 121 (3) ◽  
pp. 286-293 ◽  
Author(s):  
K. S. Kim ◽  
J. C. Park ◽  
J. W. Lee
Keyword(s):  
Shear Strain ◽  
Strain Range ◽  
Multiaxial Fatigue ◽  
Test Material ◽  
Computation Method ◽  
Strain History ◽  
Maximum Shear Strain ◽  
Variable Amplitude Loading ◽  
Variable Amplitude ◽  
Rainflow Cycle Counting

Multiaxial fatigue under variable amplitude loading is investigated using Kandil et al.’s parameter, rainflow cycle counting on the shear strain history, and the Miner-Palmgren damage rule. Fatigue data are obtained on tubular specimens of S45C steel under proportional and nonproportional tension-torsion loading. The approaches using the maximum shear strain range (Δγmax) plane and the maximum damage (Dmax) plane as the critical plane are investigated. The damage is computed for each reversal or for each cycle. The results show that both Δγmax and Dmax approaches yield acceptable fatigue lives irrespective of the damage computation method. Damage computation for each reversal tends to shift fatigue life toward the nonconservative side for some nonproportional loading. It is concluded that the overall procedure used in this study is viable for multiaxial life prediction under variable amplitude loading for the test material.

An Experimental Evaluation for Four Multiaxial Fatigue Approaches

2014 ◽  
Vol 627 ◽  
pp. 425-428
Author(s):  
Dan Jin ◽  
Da Jiang Tian ◽  
Qi Zhou Wu ◽  
Wei Lin
Keyword(s):  
Low Cycle Fatigue ◽  
Multiaxial Fatigue ◽  
304 Stainless Steel ◽  
Normal Strain ◽  
Cycle Fatigue ◽  
Critical Plane ◽  
Maximum Shear Strain ◽  
Rainflow Cycle Counting ◽  
Tubular Specimens ◽  
Damage Rule

A series of tests for low cycle fatigue were conducted on the tubular specimens for 304 stainless steel under variable amplitude and irregular axial-torsional loading. Rainflow cycle counting and linear damage rule are used to calculate fatigue damage and four approaches, e.g. SWT(Smith-Watson-Topper), KBM(Kandil-Brown-Miller), FS(Fatemi-Socie), and LKN(Lee-Kim-Nam) approach are employed to predict the fatigue life. The maximum shear strain plane, the maximum normal strain plane, and the maximum damage plane are considered as the critical plane, respectively. The effects of the choice of the critical plane on previous approaches are discussed. It is shown that comparing with the maximum shear/normal strain approach, the predictions are improved by using the maximum damage plane approach, part nonproportional paths for SWT, AV and part nonproportional paths for KBM, TV paths for FS. But for LKN, the prediction results are nonconservative for some paths than that of the maximum shear/normal strain approach.

Comparison of multiaxial fatigue damage models under variable amplitude loading

2012 ◽  
Vol 26 (11) ◽  
pp. 3439-3446 ◽  
Author(s):  
Hong Chen ◽  
De-Guang Shang ◽  
Yu-Jie Tian ◽  
Jian-Zhong Liu
Keyword(s):  
Fatigue Damage ◽  
Multiaxial Fatigue ◽  
Variable Amplitude Loading ◽  
Variable Amplitude ◽  
Damage Models

Fractographic Study on the Use of Rainflow Counting for Small and Long Cracks in AA7050

2014 ◽  
Vol 891-892 ◽  
pp. 687-692 ◽  
Author(s):  
Paul White ◽  
David S. Mongru
Keyword(s):  
Crack Growth ◽  
Fatigue Loading ◽  
Variable Amplitude Loading ◽  
Variable Amplitude ◽  
Counting Technique ◽  
Rainflow Cycle Counting ◽  
Small Cracks ◽  
The Individual ◽  
Rainflow Counting ◽  
Variable Amplitude Fatigue

Using ada/dNequation to predict fatigue crack growth for a variable amplitude loading sequence, requires converting the sequence into an equivalent series of constant amplitude cycles, which is sometimes achieved using the rainflow cycle counting technique. Rainflow counting views small intermediate cycles as an interruption to a larger cycle, in effect, the crack tip remembers the state of the larger cycle. This has been shown to be an effective technique in predicting fatigue growth rates for long cracks, but has not been extensively investigated for use in predicting the growth of small cracks. An investigation was made into the applicability of rainflow cycle counting for predicting the crack growth of small and long cracks created with variable amplitude fatigue loading in AA7050-T7451 plate, a common modern aircraft material. A series of coupons were tested with a number of different variable amplitude loading sequences which had distinct marker bands inserted to separate the individual segments of loading and enable them to be identified fractographically. For the sequences examined, which covered varying numbers of interrupted cycles and a staircase of three steps, the baseline and the rainflow loading segments within each sequence showed effectively the same rate of growth for the same stress intensity range in both the small and long crack coupons, demonstrating that rainflow cycle counting was a suitable cycle counting technique for both small and long cracks.

Multiaxial Fatigue Damage Models

2006 ◽  
Vol 324-325 ◽  
pp. 747-750 ◽  
Author(s):  
De Guang Shang ◽  
Guo Qin Sun ◽  
Jing Deng ◽  
Chu Liang Yan
Keyword(s):  
Shear Strain ◽  
Fatigue Damage ◽  
Multiaxial Fatigue ◽  
Normal Strain ◽  
Critical Plane ◽  
Proportional Loading ◽  
Maximum Shear Strain ◽  
Damage Models ◽  
Thin Tube ◽  
Critical Plane Approach

Two multiaxial damage parameters are proposed in this paper. The proposed fatigue damage parameters do not include any weight constants, which can be used under either multiaxial proportional loading or non-proportional loading. On the basis of the research on the critical plane approach for the tension-torsion thin tubular multiaxial fatigue specimens, two multiaxial fatigue damage models are proposed by combining the maximum shear strain and the normal strain excursion between adjacent turning points of the maximum shear strain on the critical plane. The proposed multiaxial fatigue damage models are used to predict the fatigue lives of the tension-torsion thin tube, and the results show that a good agreement is demonstrated with experimental data.

Modelling the Behavior of Short Fatigue Cracks under Variable Amplitude Loading Using FEM

2007 ◽  
Vol 353-358 ◽  
pp. 985-988
Author(s):  
Yan Hai Xu ◽  
Yong Xiang Zhao
Keyword(s):  
Fatigue Cracks ◽  
Crack Tip ◽  
Strain Range ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Variable Amplitude Loading ◽  
Plastic Strain Range ◽  
Variable Amplitude ◽  
Short Cracks ◽  
Crack Tip Opening

The behavior of short fatigue cracks under variable amplitude loading (VA) was investigated by FEM. The crack closure induced by the crack surface roughness was taken into consideration by using the contact between these crack surfaces. The effects of variable amplitude loading on the performance of short cracks are demonstrated with factors such as grain orientation and misorientation, crack length and the friction efficient between the contacted crack surfaces. Through the two indicators, crack tip opening displacement represented by "CTOD and "CTSD and the plastic strain range of crack tip, the characteristics of short cracks affected by loading blocks are discussed in detail. It is shown from the numerical results that the significance of the design of loading blocks in the fatigue experiments is evident and the performance of short cracks from the variable amplitude loading is more effective due to the closer to practice.

A New Multiaxial Fatigue Testing Method for Variable-Amplitude Loading and Stress Ratio

2003 ◽  
Author(s):  
Tommy J. George ◽  
M.-H. Herman Shen ◽  
Theodore Nicholas ◽  
Charles J. Cross
Keyword(s):  
Fatigue Test ◽  
Fatigue Testing ◽  
Low Cost ◽  
Design Procedure ◽  
Element Model ◽  
Multiaxial Fatigue ◽  
Biaxial Stress ◽  
Variable Amplitude Loading ◽  
Variable Amplitude ◽  
Stress Ratios

A new vibration-based multiaxial fatigue testing methodology for assessing high cycle turbine engine material fatigue strength at various stress ratios is presented. The idea is to accumulate fatigue energy on a base-excited plate specimen at high frequency resonant modes and to complete a fatigue test in a much more efficient way at very low cost. The methodology consists of: (1) a topological design procedure, incorporating a finite element model, to characterize the shape of the specimens for ensuring the required stress state/pattern, (2) a vibration feedback empirical procedure for achieving the high cycle fatigue experiments with variable-amplitude loading, and finally (3) a yielding procedure for achieving various uniaxial stress ratios. The performance of the methodology is demonstrated by the experimental results from mild steel, 6061-T6 aluminum, and Ti-6Al-4V plate specimens subjected to fully reversed bending for both uniaxial and biaxial stress states. Results are compared with those produced using traditional fatigue test machines.

Multiaxial Fatigue Under Variable Amplitude Loading

Fatigue '96 ◽  
1996 ◽  
pp. 983-988
Author(s):  
E. Vidal-Sallé ◽  
B. Kenmeugne ◽  
J.L. Robert ◽  
J. Bahuaud
Keyword(s):  
Multiaxial Fatigue ◽  
Variable Amplitude Loading ◽  
Variable Amplitude
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