Low-Cycle Fatigue Evaluation Using the Weld Master S-N Curve

2006 ◽  
Author(s):  
P. Dong ◽  
Z. Cao ◽  
J. K. Hong
Keyword(s):  
Test Data ◽  
Low Cycle Fatigue ◽  
Strain Curve ◽  
Cyclic Stress ◽  
Structural Stress ◽  
Stress Strain ◽  
Strain Behavior ◽  
Scale Test ◽  
Stress Estimation ◽  
Fatigue Evaluation

In the context of fatigue evaluation in the low-cycle regime, the use of the master S-N curve in conjunction with elastic FE-based structural stress calculations is presented. An elastic pseudo structural stress estimation is introduced by assuming that Neuber’s rule applies in relating structural stress and strain concentration at a weld to the material’s cyclic stress-strain behavior. With the pseudo structural stress procedure, recent sources of recent full scale test data on pipe and vessel welds were analyzed as a validation of the proposed procedure. The estimated fatigue lives versus actual test lives show a reasonable agreement. Finally, the feasibility of using monotonic stress-strain curves as a first approximation is also examined for applications when cyclic stress-strain curve may not be readily found. The analysis results indicate that the life estimations using monotonic stress-strain curves are reasonable, with the recent test data falling within mean ± 2σ, where σ represents the standard deviation of the master S-N curve.

Cyclic Stress-Strain Behavior and Low-Cycle Fatigue of Ti 6-4 at 260°C

1992 ◽  
Vol 114 (4) ◽  
pp. 390-398 ◽  
Author(s):  
T. Bui-Quoc ◽  
R. Gomuc ◽  
A. Biron
Keyword(s):  
Strain Amplitude ◽  
Low Cycle Fatigue ◽  
Strain Curve ◽  
Cyclic Stress ◽  
Fatigue Tests ◽  
Cycle Fatigue ◽  
Stress Strain ◽  
Strain Behavior ◽  
Show Evidence ◽  
Strain Cycling

Low-cycle fatigue tests on Ti 6-4 (Ti-6Al-4V) have been carried out at 260°C under strain-controlled conditions with constant strain amplitude and increasing multistep strain levels. The results of constant strain amplitude tests were used to establish the fatigue diagram whereas the multistep tests were examined to assess the cyclic stress-strain behavior in comparison with the conventional stress-strain curve. Most of the tests were carried out under zero-to-tension conditions in the intermediatecycle range (Nf ≃ 3 x 103 to 105 cycles). The effect of prior strain cycling on the tensile properties was also investigated. The experimental data is discussed together with theoretical evaluations. In addition, microstructural examinations of the rupture surfaces have been made to show evidence on the type of crack initiation sites and on the crack propagation modes at different strain levels.

Cyclic Stress-Strain Behavior and Low Cycle Fatigue of Ti 6242

1990 ◽  
Vol 18 (3) ◽  
pp. 160
Author(s):  
A Wolfenden ◽  
T Bui-Quoc ◽  
R Gomuc ◽  
A Biron ◽  
HL Nguyen ◽  
...  
Keyword(s):  
Low Cycle Fatigue ◽  
Cyclic Stress ◽  
Cycle Fatigue ◽  
Stress Strain ◽  
Strain Behavior

Cyclic Plastic Deformation of a Circular Plate With Work Hardening

1984 ◽  
Vol 106 (4) ◽  
pp. 336-341
Author(s):  
R. Winter
Keyword(s):  
Fatigue Life ◽  
Low Cycle Fatigue ◽  
Nonlinear Behavior ◽  
Strain Curve ◽  
Strain Range ◽  
Cyclic Strain ◽  
Cyclic Stress ◽  
Cycle Fatigue ◽  
Stress Strain ◽  
Element Analysis

An experimental and theoretical study was performed of the nonlinear behavior of a simply supported flat circular aluminum plate under reversed cyclic central load. The application is for the analysis of cyclic stress and strain of structural components in the plastic range for predicting low-cycle fatigue life. The main purpose was to determine the relative accuracy of an elastic-plastic large deformation finite element analysis when the material properties input data are derived from monotonic (noncyclic) stress-strain curves versus that derived from cyclic stress-strain curves. The results showed that large errors could be induced in the theoretical prediction of cyclic strain range when using the monotonic stress-strain curve, which could lead to large errors in predicting low-cycle fatigue life. The use of cyclic stress-strain curves, according to the model developed by Morrow, et al., proved to be accurate and convenient.

An Analytical-Based Structural Strain Method for Low Cycle Fatigue Evaluation of Girth-Welded Pipes

2017 ◽  
Author(s):  
Xianjun Pei ◽  
Wei Wang ◽  
Pingsha Dong
Keyword(s):  
Test Data ◽  
Low Cycle Fatigue ◽  
Deformation Condition ◽  
Structural Stress ◽  
Pipe Section ◽  
Fatigue Evaluation ◽  
Welded Pipe ◽  
Structural Strain ◽  
Outer Fiber ◽  
Strain Method

As a further extension to the structural stress based master S-N curve method adopted by ASME Div 2 since 2007, this paper presents an analytical-based structural strain method for girth-welded piping components. Here, structural strain is defined as outer and inner fiber strains calculated corresponding to a deformation condition in which a pipe section plane before deformation remains as a plane after deformation. The analytical formation takes into account all possible plastic deformation conditions a pipe section subjected to a combined remote cyclic bending and axial tension. A simple numerical procedure is used for solving both outer fiber and inner fiber strains, as well as the corresponding elastic core size. For fatigue evaluation purpose, the outer fiber strain can be used to calculate the corresponding pseudo elastic structural stress range so that the structural stress based master S-N curve can be directly used. Under linear elastic deformation conditions, the structural strain definition becomes exactly the same as that calculated by the structural stress method which is the basis on the ASME Div 2 master S-N was developed. A set of a recent full scale girth-welded pipe component test data in low-cycle regime was analyzed using the structural strain method. The results showed that all these new test data fall well within the ASME Div 2 master S-N curve scatter band defined by mean+-standard deviations. In addition to its demonstrated effectiveness, the key advantage of this structural strain method is its simplicity for dealing with girth-welded pipe sections, since finite element stress analysis is no longer needed.

Reliability Analysis of LCF Life for a Turbine Disk

2010 ◽  
Vol 146-147 ◽  
pp. 1379-1385
Author(s):  
Yang Gao ◽  
Chang Jun Yang ◽  
Kai Lin ◽  
Qing Gao
Keyword(s):  
Reliability Analysis ◽  
Low Cycle Fatigue ◽  
Three Dimensional ◽  
Strain Curve ◽  
Cyclic Strain ◽  
Cyclic Stress ◽  
Turbine Disk ◽  
Fatigue Reliability ◽  
Three Dimensional Model ◽  
Stress Strain

Cyclic stress-strain curve and cyclic strain-life curve appear distinct scatters, and the scatter of fatigue life increases with reducing of the strain levels. A methodology for reliability simulation of low cycle fatigue (LCF) life for turbine disk structures is developed in this paper. First, probabilistic cyclic stress-strain model and linear heteroscedastic probabilistic cyclic strain-life model are founded based on the fatigue test data. Second, three dimensional model of a turbine disk is built, and the fatigue reliability analysis of this turbine disk is implemented in probabilistic design module (PDS) of ANSYS by the combination of response surface method (RSM) and Monte Carlo simulation (MCS). The predicted life with reliability 0.9987 is well consistent with the technology life obtained from disks LCF tests by scatter factors method.

Cyclic stress–strain behavior and low cycle fatigue life of cast A356 alloys

2011 ◽  
Vol 33 (12) ◽  
pp. 1600-1607 ◽  
Author(s):  
M.S. Song ◽  
Y.Y. Kong ◽  
M.W. Ran ◽  
Y.C. She
Keyword(s):  
Fatigue Life ◽  
Low Cycle Fatigue ◽  
Cyclic Stress ◽  
Cycle Fatigue ◽  
Stress Strain ◽  
Strain Behavior
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