Influence of Temperature and Stress Ratio on the Low-Cycle Fatigue Behavior of Trimarc-1 /Ti-6Al-2Sn-4Zr-2Mo

2009 ◽  
pp. 199-199-18 ◽  
Author(s):  
DJ Buchanan ◽  
R John ◽  
KE Goecke
Keyword(s):  
Stress Ratio ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Cycle Fatigue ◽  
Influence Of Temperature

Investigation of High Cycle and Low Cycle Fatigue Interaction on Fatigue Behavior of Welded Joints

2012 ◽  
Vol 217-219 ◽  
pp. 2101-2106
Author(s):  
Liang Chen Wu ◽  
Dong Po Wang
Keyword(s):  
Adverse Effect ◽  
Fatigue Life ◽  
Welded Joints ◽  
High Frequency ◽  
Stress Ratio ◽  
High Cycle Fatigue ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Low Frequency ◽  
Cycle Fatigue

Samples of Q345 steel welded joints were tested to failure under low cycle fatigue(LCF),high cycle fatigue(HCF) and combined fatigue(CCF) using an apparatus that is capable of providing interactive LCF/HCF loading. The stress ratio R is 0.5 and the frequency of HCF is about 19kHz. The result indicates that not only high frequency minor cycles superimposed on low frequency major cycles , but also low frequency minor cycles superimposed on high frequency major cycles can do remarkable damage to fatigue performance of welded joints. The CCF strength is characterized by amplitude envelope. If CCF fatigue life is characterized by LCF life, adverse effect of HCF component is underestimated. If CCF fatigue life is characterized by HCF life, adverse effect of LCF component is overrated.

Damage accumulation near a hole under low cycle fatigue proceeding from measurements of local deformation response

2020 ◽  
Vol 86 (10) ◽  
pp. 46-55
Author(s):  
S. I. Eleonsky ◽  
Yu. G. Matvienko ◽  
V. S. Pisarev ◽  
A. V. Chernov
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Damage Accumulation ◽  
Stress Ratio ◽  
Low Cycle Fatigue ◽  
Accumulation Process ◽  
Stress Range ◽  
Cycle Fatigue ◽  
Deformation Response

A new destructive method for quantitative determination of the damage accumulation in the vicinity of a stress concentrator has been proposed and verified. Increase of damage degree in local area with a high level of the strain gradient was achieved through preliminary low-cycle pull-push loading of plane specimens with central open holes. The above procedure is performed for three programs at the same stress range (333.3 MPa) and different stress ratio values 0.33, – 0.66 and – 1.0, and vice versa for two programs at the same stress ratio – 0.33 and different stress range 333.3 and 233.3 MPa. This process offers a set of the objects to be considered with different degree of accumulated fatigue damages. The key point of the developed approach consists in the fact that plane specimens with open holes are tested under real operation conditions without a preliminary notching of the specimen initiating the fatigue crack growth. The measured parameters necessary for a quantitative description of the damage accumulation process were obtained by removing the local volume of the material in the form of a sequence of narrow notches at a constant level of external tensile stress. External load can be considered an amplifier enhancing a useful signal responsible for revealing the material damage. The notch is intended for assessing the level of fatigue damage, just as probe holes are used to release residual stress energy in the hole drilling method. Measurements of the deformation response caused by local removing of the material are carried out by electronic speckle-pattern interferometry at different stages of low-cycle fatigue. The transition from measured in-plane displacements to the values of the stress intensity factor (SIF) and the T-stress was carried out on the basis of the relations of linear fracture mechanics. It was shown that the normalized dependences of the stress intensity factor on the durability percentage for the first notch (constructed for four programs of cyclic loading with different parameters), reflect the effect of the stress ratio and stress range of the loading cycle on the rate of damage accumulation. The data were used to obtain the explicit form of the damage accumulation function that quantitatively describes damage accumulation process. The functions were constructed for different stress ratios and stress ranges.

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.

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