scholarly journals Study on the Elastic–Plastic Correlation of Low-Cycle Fatigue for Variable Asymmetric Loadings

Materials ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2451 ◽  
Author(s):  
Junhong Zhang ◽  
Weidong Li ◽  
Huwei Dai ◽  
Nuohao Liu ◽  
Jiewei Lin
Keyword(s):  
Low Cycle Fatigue ◽  
Strain Ratio ◽  
Stress Effect ◽  
Mean Stress ◽  
Cycle Fatigue ◽  
Ratcheting Strain ◽  
Asymmetric Loading ◽  
Pressure Tubing ◽  
Proposed Model ◽  
The Mean

The mean stress effect in fatigue life varies by material and loading conditions. Therefore, a classical low cycle fatigue (LCF) model based on mean stress correction shows limits in asymmetric loading cases in both accuracy and applicability. In this paper, the effect of strain ratio (R) on LCF life is analyzed and a strain ratio-based model is presented for asymmetric loading cases. Two correction factors are introduced to express correlations between strain ratio and fatigue strength coefficient and between strain ratio and fatigue ductility coefficient. Verifications are conducted through four materials under different strain ratios: high-pressure tubing steel (HPTS), 2124-T851 aluminum alloy, epoxy resin and AZ61A magnesium alloy. Compared with current widely used LCF models, the proposed model shows a better life prediction accuracy and higher potential in implementation in symmetric and asymmetric loading cases for different materials. It is also found that the strain ratio-based correction is able to consider the damage of ratcheting strain that the mean stress-based models cannot.

Uniaxial Ratcheting and Low-Cycle Fatigue Failure of U75V Rail Steel

2016 ◽  
Vol 853 ◽  
pp. 246-250 ◽  
Author(s):  
Tao Fang ◽  
Qian Hua Kan ◽  
Guo Zheng Kang ◽  
Wen Yi Yan
Keyword(s):  
Fatigue Life ◽  
Strain Amplitude ◽  
Stress Ratio ◽  
Stress Amplitude ◽  
Rail Steel ◽  
Low Cycle Fatigue ◽  
Mean Stress ◽  
Cycle Fatigue ◽  
Ratcheting Strain ◽  
Cyclic Straining

Experiments on U75V rail steel were carried out to investigate the cyclic feature, ratcheting behavior and low-cycle fatigue under both strain- and stress-controlled loadings at room temperature. It was found that U75V rail steel shows strain amplitude dependent cyclic softening feature, i.e., the responded stress amplitude under strain-controlled decreases with the increasing number of cycles and reaches a stable value after about 20th cycle. Ratcheting strain increases with an increasing stress amplitude and mean stress, except for stress ratio, and the ratcheting strain in failure also increases with an increasing stress amplitude, mean stress and stress ratio. The low-cycle fatigue lives under cyclic straining decrease linearly with an increasing strain amplitude, the fatigue lives under cyclic stressing decrease with an increasing mean stress except for zero mean stress, and decrease with an increasing stress amplitude. Ratcheting behavior with a high mean stress reduces fatigue life of rail steel by comparing fatigue lives under stress cycling with those under strain cycling. Research findings are helpful to evaluate fatigue life of U75V rail steel in the railways with passenger and freight traffic.

scholarly journals Multiaxial fatigue life estimation in low-cycle fatigue regime including the mean stress effect

2018 ◽  
Vol 165 ◽  
pp. 16002
Author(s):  
Daniela Scorza ◽  
Andrea Carpinteri ◽  
Giovanni Fortese ◽  
Camilla Ronchei ◽  
Sabrina Vantadori ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Low Cycle Fatigue ◽  
Equivalent Strain ◽  
Mean Value ◽  
Multiaxial Fatigue ◽  
Stress Effect ◽  
Mean Stress ◽  
Cycle Fatigue ◽  
Structural Components ◽  
Mean Stress Effect

The goal of the present paper is to discuss the reliability of a strain-based multiaxial Low-Cycle Fatigue (LCF) criterion in estimating the fatigue lifetime of metallic structural components subjected to multiaxial sinusoidal loading with zero and non-zero mean value. Since it is well-known that a tensile mean normal stress reduces the fatigue life of structural components, three different models available in the literature are implemented in the present criterion in order to take into account the above mean stress effect. In particular, such a criterion is formulated in terms of strains by employing the displacement components acting on the critical plane and, then, by defining an equivalent strain related to such a plane. The Morrow model, the Smith-Watson-Topper model and the Manson-Halford model are applied to define such an equivalent strain. The effectiveness of the new formulations is evaluated through comparison with some experimental data reported in the literature, related to biaxial fatigue tests performed on metallic specimens under in-and out-of-phase loadings characterised by non-zero mean stress values.

scholarly journals A strain ratio based modification on low-cycle fatigue model for asymmetric loading

Authorea ◽  
2020 ◽  
Author(s):  
Junhong Zhang ◽  
weidong li ◽  
Jiewei Lin ◽  
yongbo qiu ◽  
tianyi zhou ◽  
...  
Keyword(s):  
Low Cycle Fatigue ◽  
Strain Ratio ◽  
Cycle Fatigue ◽  
Asymmetric Loading ◽  
Fatigue Model

Effect of Mean Stress and of Mean Strain in Low-Cycle Fatigue of A-517 and A-201 Steels

1970 ◽  
Vol 92 (1) ◽  
pp. 35-51 ◽  
Author(s):  
J. Dubuc ◽  
J. R. Vanasse ◽  
A. Biron ◽  
A. Bazergui
Keyword(s):  
Plastic Strain ◽  
Pressure Vessel ◽  
Room Temperature ◽  
Low Cycle Fatigue ◽  
Fatigue Tests ◽  
Mean Stress ◽  
Cycle Fatigue ◽  
The Mean ◽  
Mean Strain

A number of low-cycle fatigue tests has been carried out at room temperature on two materials commonly used in pressure vessel fabrication. For strain-controlled tests, the influence of different mean strains is studied; similarly, the effect of varying the mean stress is analyzed for stress-controlled tests. Relations involving elastic and plastic strain ranges, and the variations of strains or stresses during the fatigue tests are discussed.

Novel Modeling of Mean Stress Effect on the High-Cycle Fatigue Performance of Preloaded Threaded Fasteners

2019 ◽  
Author(s):  
Sayed A. Nassar ◽  
Tianwu Li
Keyword(s):  
Experimental Data ◽  
High Cycle Fatigue ◽  
High Strength ◽  
Fatigue Performance ◽  
Stress Effect ◽  
Mean Stress ◽  
Cycle Fatigue ◽  
Mean Stress Effect ◽  
Threaded Fasteners ◽  
Proposed Model

Abstract An experimentally validated model is proposed for the effect of fastener mean stress on its high cycle fatigue (HCF) performance. The model is also used for comparing fatigue performance of ultra-high strength (UHS) fasteners Class 14.8, 15.8 and 16.8 with that of commercially available (CA) Class 10.9 and 12.9 fasteners. Respective mean stress-adjusted S-N curves are constructed using experimental data following applicable ASTM standards. Proposed model results are compared with other existing models that account for the effect of mean stress such as Goodman, Gerber, Morrow, Soderberg, and Elliptic (ASME) models. Detailed discussion of the results, failure mode, and conclusions are provided.

Strain Ratio Effect on the Low Cycle Fatigue Behavior and Microstructure of High-Mn Austenitic Alloy Undergoing the Strain-Induced ε-Martensitic Transformation

2018 ◽  
Vol 941 ◽  
pp. 1065-1070
Author(s):  
Ilya Nikulin ◽  
Takahiro Sawaguchi
Keyword(s):  
Martensitic Transformation ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Control Mode ◽  
Total Strain ◽  
Lattice Rotation ◽  
Mean Stress ◽  
Total Strain Amplitude ◽  
Cycle Fatigue ◽  
The Mean

The effect of the strain asymmetry on low-cycle fatigue properties and microstructure of Fe–15Mn–10Cr–8Ni–4Si (in. wt. %) alloy undergoing the strain-induced ε-martensitic transformation (ε-MT) were investigated at strain ratios,R, of-1, -0.2, 0.2 and 0.5 under total strain-control mode with total strain amplitude of 0.01. At studied strain ratios the clear asymmetry in tension and compression stress providing tensile mean stress was observed in alloy deformed atRof-0.2, 0.2 and 0.5. The mean stress rapidly decreases to ~ 100 cycles and remain almost zero until failure. It was found that strain-induced ε-martensitic transformation and lattice rotation of austenite provide cyclic hardening of the studied alloy leading to the mean stress relaxation and provides the stability in hysteresis loops behavior at studiedR. As a consequence, the fatigue life,Nf, of the alloy remains on the level of the alloy deformed by LCF atR, of -1 (NfR=-1=9200 cycles). The details of the fatigue behavior, deformation mechanisms and microstructure evolution of the studied alloy are discussed.

Stress-Strain Behavior of Inconel 718 During Low Cycle Fatigue

1982 ◽  
Vol 104 (3) ◽  
pp. 186-191 ◽  
Author(s):  
T. S. Cook
Keyword(s):  
Inconel 718 ◽  
Low Cycle Fatigue ◽  
Cyclic Stress ◽  
Fatigue Tests ◽  
Mean Stress ◽  
Cycle Fatigue ◽  
Stress Strain ◽  
Strain Behavior ◽  
Varied Temperature ◽  
The Mean

In the development of better methods of assessing damage accumulation, one of the requirements is an understanding of the cyclic constitutive behavior of the material. It is known that the cyclic stress-strain behavior is affected by temperature and possibly Rε ratio (εmin/εmax) and that the properties change as cycles are accumulated. This report presents some results, particularly the development of a mean stress in the material, obtained during low cycle fatigue tests of Inconel 718. The tests varied temperature and Rε ratio to determine their effects on the cyclic constitutive relation. Changes in the cyclic stress-strain behavior as a function of cycles were also examined. It was possible to relate the mean stress to either the total or plastic strain ranges for all temperatures. There was sufficient scatter in the data to prevent an unambiguous interpretation of the effect of Rε ratio on the mean stress, however.

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