scholarly journals Low-Cycle Fatigue and Cyclic Deformation Behavior of Type 16-8-2 Weld Metal at Elevated Temperature

2009 ◽  
pp. 57-57-16 ◽  
Author(s):  
DT Raske
Author(s):  
Peng Zhao ◽  
Fu-Zhen Xuan ◽  
De-Long Wu

Fatigue testing for an important turbine rotor material (X12CrMoWVNbN10-1-1 steel) was carried out over a wide range of strain and stress amplitudes at 873K. Particular attention was paid to the effect of control mode on the cyclic deformation behavior and life assessment at elevated temperature. Two main domains were observed depending both on the strain and stress amplitudes, where the effect of control mode was different. In the micro plastic deformation domain, the cyclic softening is slight and there is no clear difference in fatigue behavior between the stress and strain modes. In the plastic damage regime, stress cycling causes more significant softening or damage than strain cycling. The dependence of damage behavior on the evolution of dislocation substructure was focused. On the other hand, it is not possible to use strain based life model to predict fatigue life with the test results under a different control mode. A unified energy-based model is proposed based upon the deformation mechanism and the experimental results, which can assess the low cycle fatigue life with different control modes. The results obtained in this study could have significant implications in the design of structures.


Author(s):  
Masaki Mitsuya ◽  
Hiroshi Yatabe

Buried pipelines may be deformed due to earthquakes and also corrode despite corrosion control measures such as protective coatings and cathodic protection. In such cases, it is necessary to ensure the integrity of the corroded pipelines against earthquakes. This study developed a method to evaluate the earthquake resistance of corroded pipelines subjected to seismic ground motions. Axial cyclic loading experiments were carried out on line pipes subjected to seismic motion to clarify the cyclic deformation behavior until buckling occurs. The test pipes were machined so that each one would have a different degree of local metal loss. As the cyclic loading progressed, displacement shifted to the compression side due to the formation of a bulge. The pipe buckled after several cycles. To evaluate the earthquake resistance of different pipelines, with varying degrees of local metal loss, a finite-element analysis method was developed that simulates the cyclic deformation behavior. A combination of kinematic and isotropic hardening components was used to model the material properties. These components were obtained from small specimen tests that consisted of a monotonic tensile test and a low cycle fatigue test under a specific strain amplitude. This method enabled the successful prediction of the cyclic deformation behavior, including the number of cycles required for the buckling of pipes with varying degrees of metal loss. In addition, the effect of each dimension (depth, longitudinal length and circumferential width) of local metal loss on the cyclic buckling was studied. Furthermore, the kinematic hardening component was investigated for the different materials by the low cycle fatigue tests. The kinematic hardening components could be regarded as the same for all the materials when using this component as the material property for the finite-element analyses simulating the cyclic deformation behavior. This indicates that the cyclic deformation behavior of various line pipes can be evaluated only based on their respective tensile properties and common kinematic hardening component.


2004 ◽  
Vol 36 (1-2) ◽  
pp. 85-98 ◽  
Author(s):  
L.J. Chen ◽  
P.K. Liaw ◽  
H. Wang ◽  
Y.H. He ◽  
R.L. McDaniels ◽  
...  

1996 ◽  
Vol 460 ◽  
Author(s):  
D. B. Hanes ◽  
R. Gibala

ABSTRACTThe monotonie mechanical behavior in tension and compression of FeAl has been well documented. However, very little work has been done on the cyclic deformation behavior of this material. In this work, the behavior of FeAl (42 at. % Al) under low cycle fatigue was studied, including the effects of test environments and surface coatings. It was found that the fatigue life of this alloy is limited by environmental embrittlement. This embrittlement process can be equally well prevented by deformation in an oxygen environment or by coating the alloy with a protective film. The type of film applied appears to have little effect. Similar results were seen in monotonie testing.


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