Analysis on Low Cycle Fatigue Life and Fatigue Fracture Surface Morphology of TC25 Titanium Alloy

2016 ◽  
Vol 697 ◽  
pp. 652-657
Author(s):  
Rong Guo Zhao ◽  
Yi Yan ◽  
Yong Zhou Jiang ◽  
Xi Yan Luo ◽  
Qi Bang Li ◽  
...  
Keyword(s):  
Titanium Alloy ◽  
Fatigue Crack ◽  
Fatigue Life ◽  
Fracture Surface ◽  
Crack Growth ◽  
Fatigue Fracture ◽  
Low Cycle Fatigue ◽  
Observation System ◽  
Cycle Fatigue ◽  
Stress Strain

At room temperature, the low cycle fatigue tests for smooth specimens of TC25 titanium alloy under various stress ranges are operated at a CSS280I-20w Electro Hydraulic Servo Universal Testing Machine with a microscopic observation system, and the low cycle fatigue lifetimes are measured. Based upon the analysis of stress-strain hysteresis loop of low cycle fatigue of TC25 titanium alloy, a simplified Manson-Coffin formula is derived according to both the experimental characteristics and the stress-strain constitutive model, the fatigue lifetimes are plotted against stress ranges, and a stress-fatigue life curve for TC25 titanium alloy is obtained by the linear regression analysis method. Finally, the fracture surface morphologies of TC25 specimens are investigated using a JSM-6360 Scanning Electron Microscopy, and the fatigue fracture mechanisms of low cycle fatigue are studied. It shows that the plastic deformations are mainly formed at the accelerated fracture stage, and various shear lips can be observed on the fracture surfaces, which demonstrates that the shear stress results in the final rupture of TC25 titanium alloy. During the fracture of low cycle fatigue, the cleavage nucleation leads to the formation of fatigue crack initiation region, the fatigue crack growth exhibits a mixed transgranular and intergranular crack growth mode, and in the final rupture region, the fracture surface of low cycle fatigue of TC25 titanium alloy appears as a typical semi-brittle fracture mode.

Low-Cycle Fatigue Performances of P/M Ti-Fe-Mo-Al-Nd Alloy

2007 ◽  
Vol 534-536 ◽  
pp. 973-976
Author(s):  
Hai Yan Liu ◽  
Hui Ping Tang ◽  
Cheng Li ◽  
Yuan Ping Huang ◽  
Boyun Huang ◽  
...  
Keyword(s):  
Titanium Alloy ◽  
Linear Regression ◽  
Fracture Surface ◽  
Fatigue Fracture ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Cycle Fatigue ◽  
Linear Regression Equation ◽  
Fatigue Fracture Surface ◽  
Fatigue Lifetime

The low-cycle fatigue performance and fracture of the P/M Ti-Fe-Mo-Al-Nd Alloys after sintering and forging have been studied, and the linear regression equation of low-cycle fatigue lifetime was obtained. The fatigue performances were investigated [Comment: Not quite sure what is mean by ‘objected’ here.] under two different conditions. The fatigue fracture surface was analyzed by SEM. The low-cycle fatigue behavior of the P/M titanium alloy are discussed.

Low Cycle Fatigue Behavior of TA29 Titanium Alloy at Different Temperatures

2016 ◽  
Vol 849 ◽  
pp. 353-359 ◽  
Author(s):  
Juan Li ◽  
Jian Ming Cai ◽  
Rui Duan ◽  
Xu Huang
Keyword(s):  
Titanium Alloy ◽  
Fatigue Crack ◽  
Fatigue Life ◽  
Strain Amplitude ◽  
Low Cycle Fatigue ◽  
Testing Temperature ◽  
Cyclic Stress ◽  
Cycle Fatigue ◽  
Fatigue Striations ◽  
Different Temperatures

The low cycle fatigue behaviour of TA29 titanium alloy blisk forging at 300°C, 400°C, 500°C, 600°C were studied. The cyclic stress response, the stress-strain behaviour, the fatigue life and the fractograph were observed and analyzed. Through the double logarithm linear regression, the Coffin-Manson model parameters of TA29 titanium alloy at different temperatures were obtained. The results showed that the fatigue life decreases as the strain amplitude increases. Also, the testing temperature has a significant effect on the low cycle fatigue properties of TA29 titanium alloy. At the same level of the strain amplitude, the fatigue life and the peak value of cyclic stress decrease, while the plastic strain component in total strain amplitude increases with the increase of testing temperature. On the basis of the fractograph of fatigue specimens, the initiation of crack is mainly on the surface of the specimen. Fatigue striations can be seen clearly at fatigue crack propagation area. The fatigue striations in stable fatigue crack propagation area were broadened, and the propagation area was reduced and the final rupture area was increased with the increase of testing temperature.

Reeled CRA Clad/Lined Pipeline Installation: Seastate Optimisation From Fatigue and Fracture Perspective

2018 ◽  
Author(s):  
Daowu Zhou ◽  
T. Sriskandarajah ◽  
Heidi Bowlby ◽  
Ove Skorpen
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Low Cycle Fatigue ◽  
Superposition Method ◽  
Cycle Fatigue ◽  
Limit States ◽  
Simplified Approach ◽  
Fatigue And Fracture ◽  
Girth Welds

The deformation mechanism in reel-lay of corrosive resistance alloy (CRA) clad/lined pipes can facilitate defect tearing and low cycle fatigue crack growth in the girth welds. Pipe-lay after straightening will subject the CRA welds to high cycle fatigue. The permissible seastate for installation will be governed by failure limit states such as local collapse, wrinkling of the liner, fatigue and fracture. By means of a recently completed offshore project in North Sea, this paper discusses seastate optimisation when installing pipelines with CRA girth welds, from a fatigue and fracture perspective. The additional limiting requirement in CRA welds to maintain CRA liner integrity can lead to significant assessment work since all critical welds shall be examined. AUT scanned defect data were utilised to maximise permissible seastates based on fatigue allowance from a fatigue crack growth calculation. An alternative simplified approach to derive the crack growth based on a superposition method is studied. It enables a straightforward real-time prediction of crack growth and has the potential to be used during the offshore campaign to improve the installation flexibility. Post-installation fracture assessment under more critical seastates is examined for CRA partial over-matching welds. A comparison of CDF between conventional ECA procedure and 3D FE is provided.

Investigation on Fatigue Damage of the Al5Zn2Mg High Strength Aluminum Alloy

2013 ◽  
Vol 721 ◽  
pp. 12-15 ◽  
Author(s):  
Xian Liang Sun ◽  
Ai Qin Tian ◽  
Wen Bin Chen ◽  
San San Ding ◽  
Shang Lei Yang
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Crack ◽  
Grain Boundary ◽  
Fatigue Fracture ◽  
Low Cycle Fatigue ◽  
High Strength ◽  
Alloy Sample ◽  
Cycle Fatigue ◽  
High Strength Aluminum Alloy ◽  
Propagation Zone

The fatigue fracture and the microstructure of Al5Zn2Mg high strength aluminum alloy were observed by OM, SEM and TEM, and the low cycle fatigue properties were tested and analyzed. The results of experimentation show that the low cycle fatigue life of Al5Zn2Mg high strength aluminum alloy is 9.28×104 cycle in R=0.1, f=8Hz, and σmax=0.75σb. The tensile strength is 444MPa. The fatigue fracture is composed of the initiation zone, the propagation zone, and the sudden fracture zone, which is characteristic of a mixed-type fatigue fracture. The fatigue crack initiates in the surface of Al5Zn2Mg aluminum alloy sample, while there is no fatigue striation in fatigue crack propagation zone. The η′(MgZn2) transitional strengthening phases are precipitated in Al5Zn2Mg aluminum alloy, and mostly distributed in grain boundary. The diameter of η′ strengthening phase is fine, about is 10nm. There is none precipitated zone in width nearby the grain boundary

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