Effects of hysteresis energy and mean stress on low-cycle fatigue behaviors of an extruded magnesium alloy

2011 ◽  
Vol 65 (1) ◽  
pp. 53-56 ◽  
Author(s):  
F. Lv ◽  
F. Yang ◽  
S.X. Li ◽  
Z.F. Zhang
Keyword(s):  
Magnesium Alloy ◽  
Low Cycle Fatigue ◽  
Mean Stress ◽  
Cycle Fatigue

Fatigue of AZ91E-T6 Cast Magnesium Alloy

1993 ◽  
Vol 115 (4) ◽  
pp. 391-397 ◽  
Author(s):  
D. L. Goodenberger ◽  
R. I. Stephens
Keyword(s):  
Fatigue Crack ◽  
Magnesium Alloy ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Mean Stress ◽  
Cycle Fatigue ◽  
Cast Magnesium Alloy ◽  
Cast Magnesium

The purpose of this research was to obtain room temperature fatigue behavior of AZ91E-T6 cast magnesium alloy and to determine if commonly used models that depict fatigue behavior are applicable to this cast alloy. Axial strain-controlled fatigue behavior using cylindrical specimens were employed to determine low cycle fatigue behavior with strain ratios R = εmin/εmax = 0, −1, and −2. The conventional log-log total strain low cycle fatigue model properly represented the R = −1 axial fatigue data. Significant mean stress relaxation occurred for all R = 0 and −2 axial fatigue tests. However, for the smaller strain amplitude tests with R = 0, sufficient mean stresses were retained such that fatigue life was reduced. The mean strains/stresses had little influence on the cyclic stress-strain curve which exhibited cyclic strain hardening. Mean stress effects were analyzed using the Morrow, SWT and Lorenzo-Laird models and similar, but oftentimes nonconservative, calculations resulted. Region I and II fatigue crack growth behavior was determined using C(T) speciments with load ratios R = Pmin/Pmax = 0.05 and 0.5. Values of ΔKth and (ΔKth)eff were less than 1.5 MPa m and the Paris equation slopes were between 3.3 and 3.9. Quasi-cleavage was predominant for both fatigue crack growth and final fracture regions. The commonly used low cycle fatigue and fatigue crack growth models appear to reasonably represent most of the results with this AZ91E-T6 cast magnesium alloy.

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 Notch Effect in Low-Cycle Fatigue : 2nd Report : Effect of Stress Change and Mean Stress

1975 ◽  
Vol 18 (119) ◽  
pp. 465-472 ◽  
Author(s):  
Yukitaka MURAKAMI ◽  
Hironobu NISITANI ◽  
Shoh KUSUMOTO
Keyword(s):  
Low Cycle Fatigue ◽  
Stress Change ◽  
Notch Effect ◽  
Mean Stress ◽  
Cycle Fatigue

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.

Proposal of a new low-cycle fatigue life model for cast iron with room temperature calibration involving mean stress and high-temperature effects

2019 ◽  
Vol 233 (14) ◽  
pp. 5056-5073 ◽  
Author(s):  
Cristiana Delprete ◽  
Raffaella Sesana
Keyword(s):  
Finite Element ◽  
Cast Iron ◽  
High Temperature ◽  
Finite Element Model ◽  
Life Prediction ◽  
Low Cycle Fatigue ◽  
Element Model ◽  
Mean Stress ◽  
Exhaust Manifold ◽  
Cycle Fatigue

The paper presents and discusses a low-cycle fatigue life prediction energy-based model. The model was applied to a commercial cast iron automotive exhaust manifold. The total expended energy until fracture proposed by the Skelton model was modified by means of two coefficients which take into account of the effects of mean stress and/or mean strain, and the presence of high temperature. The model was calibrated by means of experimental tests developed on Fe–2.4C–4.6Si–0.7Mo–1.2Cr high-temperature-resistant ductile cast iron. The thermostructural transient analysis was developed on a finite element model built to overtake confidentiality industrial restrictions. In addition to the commercial exhaust manifold, the finite element model considers the bolts, the gasket, and a cylinder head simulacrum to consider the corresponding thermal and mechanical boundary conditions. The life assessment performance of the energy-based model with respect the cast iron specimens was compared with the corresponding Basquin–Manson–Coffin and Skelton models. The model prediction fits the experimental data with a good agreement, which is comparable with both the literature models and it shows a better fitting at high temperature. The life estimations computed with respect the exhaust manifold finite element model were compared with different multiaxial literature life models and literature data to evaluate the life prediction capability of the proposed energy-based model.

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