On Fatigue Design Curves for 2.25Cr-1Mo-V Steel Reactors at Elevated Temperature in Code Case 2605

2018 ◽  
Vol 140 (2) ◽  
Author(s):  
Jian-Guo Gong ◽  
Fang Liu ◽  
Fu-Zhen Xuan
Keyword(s):  
Stress Level ◽  
Design Method ◽  
Creep Damage ◽  
Damage Parameter ◽  
Damage Factor ◽  
Cycle Number ◽  
Design Curve ◽  
Fatigue Design ◽  
A Value ◽  
Cyclic Frequency

Fatigue design method for 2.25Cr-1Mo-V steel reactors in code case 2605 (CC 2605) is reviewed. Main factors such as the accelerating function of fatigue action, the cyclic frequency, the strain damage factor (β) related to the fatigue design curves are addressed, and the applicable stress level for pure creep rupture analysis in CC 2605 is also discussed. Results indicate that, for the high loading levels, the accelerating function of fatigue action and strain damage factor contribute relatively remarkably to the fatigue design curve. The increase of cyclic frequency leads to a remarkable increase of the allowable fatigue cycle number and hence reduces the conservativeness of fatigue design curve. It should be stipulated in CC 2605 that the applicable stress level is higher than a value of around 200 MPa (slightly dependent on temperature) for the adjusted uniaxial Omega damage parameter and 16 MPa for the creep strain rate when the Omega creep-damage method is employed.

ECA Methodology for Fatigue Design of Risers and Flowlines

2007 ◽  
Author(s):  
C. H. Luk ◽  
T. J. Wang
Keyword(s):  
Fracture Mechanics ◽  
Design Method ◽  
Steel Catenary Riser ◽  
Fatigue Design ◽  
Wide Range ◽  
Fatigue And Fracture ◽  
Level 3 ◽  
Fatigue Loads ◽  
Vessel Motion ◽  
Level 2

Engineering Criticality Assessment (ECA) is a procedure based on fracture mechanics that may be used to supplement the traditional S-N approach and determine the flaw acceptance and inspection criteria in fatigue and fracture design of risers and flowlines. A number of design codes provide guidance for this procedure, e.g. BS-7910:2005 [1]. However, more investigations and example studies are still needed to address the design implications for riser and flowline applications. This paper provides a review of the existing ECA methodology, presents a fracture mechanics design method for a wide range of riser and flowline fatigue problems, and shows flaw size results from steel catenary riser (SCR) and flowline (FL) examples. The first example is a deepwater SCR subjected to fatigue loads due to vessel motion and riser VIV. The second example is a subsea flowline subjected to thermal fatigue loads. The effects of crack re-characterization and material plasticity on the Level-2 and Level-3 ECA results of the SCR and flowline examples are illustrated.

Effect of operating parameters on functional fatigue characteristics of an Ni-Ti shape memory alloy on partial thermomechanical cycling

2022 ◽  
pp. 1045389X2110722
Author(s):  
Swaminathan Ganesan ◽  
Sampath Vedamanickam
Keyword(s):  
Yield Strength ◽  
Applied Stress ◽  
Stress Level ◽  
Crack Nucleation ◽  
Maximum Temperature ◽  
Thermomechanical Cycling ◽  
Permanent Strain ◽  
A Value ◽  
The Stability ◽  
Cycle Temperature

In this study, the influence of upper cycle temperature (maximum temperature in a cycle) and the magnitude of applied stress on the functional properties of an SMA during partial thermomechanical cycling has been studied. A near-equiatomic NiTi SMA was chosen and tested under different upper cycle temperatures (between martensite finish (Mf) and austenite finish (Af) temperatures) and stress level (below and above the yield strength of the martensite). The upper cycle temperature was varied by controlling the magnitude of the current supply. The results show that a raise in the upper cycle temperature causes the permanent strain to increase and also lowers the stability. However, decreasing the stress imposed to a value lower than the yield strength of the martensite improves cyclic stability. The upper cycle temperature was found to influence the crack nucleation, whereas the applied stress level the crack propagation during partial thermomechanical cycling of SMAs. Therefore, decreasing the upper cycle temperature as well as the magnitude of stress applied to lower than the yield stress of martensite have been found to be suitable strategies for increasing the lifespan of SMA-based actuators during partial thermomechanical cycling.

The Iterative Method for Reliability Estimation of Fatigue Life

2012 ◽  
Vol 249-250 ◽  
pp. 628-631
Author(s):  
Xin Li Bai ◽  
Peng Xu ◽  
Jiang Yan Li
Keyword(s):  
Fatigue Life ◽  
Design Method ◽  
Estimation Method ◽  
Engineering Application ◽  
Reliability Estimation ◽  
Fatigue Reliability ◽  
Reliability Design ◽  
Fatigue Design ◽  
Machine Parts ◽  
Stress Cycles

The expression of reliability estimation method for fatigue life of machine parts was derived, and two kinds of stress cycles (reversed cycle and un-symmetric reversed cycle) were considered. An iteration method is presented and the corresponding computer program named STRENGTH-2 is developed for estimating reliable life of machine parts. The engineering application results show that the calculated results are close to experimental results. The proposed method can be convenient to carry out the fatigue reliability design for machine parts under the action of uni-axial and multi-axial loadings, and promote the popularization and application of existing anti-fatigue design method. It has the high value of engineering application.

Reliability Estimation of Fatigue Life for Machine Parts under Uniaxial Constant Amplitude Load

2012 ◽  
Vol 249-250 ◽  
pp. 632-635
Author(s):  
Yu He Li ◽  
Xin Li Bai ◽  
Ying Fang Zhang
Keyword(s):  
Fatigue Life ◽  
Design Method ◽  
Engineering Application ◽  
Reliability Estimation ◽  
Estimation Methods ◽  
Fatigue Reliability ◽  
Constant Amplitude ◽  
Reliability Design ◽  
Fatigue Design ◽  
Machine Parts

Two methods acquiring p-S-N curve for machine parts are given, namely directly searching out the p-S-N curve of the material from material database and using the idealized p-S-N curve. Reliability estimation methods of fatigue life of machine parts are derived under uniaxial constant amplitude load. Two kinds of circumstances (fixed stress and probabilistic stress) and two kinds of stress cycles (reversed cycle and unsymmetric reversed cycle) are considered. An iteration method is presented and the corresponding computer program is developed for estimating reliable life of machine parts. The engineering application results show that the calculated results are closer to experimental results. The suggested method can be convenient to fatigue reliability design of machine parts. It has good stimulative effect on popularization and application of existing anti-fatigue design method for machine parts, and high value of engineering application.

ASME Code-Case Proposal to Explicitly Quantify the Interaction Between the PWR Environment and Component Surface Finish

2017 ◽  
Author(s):  
Thomas Métais ◽  
Stéphan Courtin ◽  
Laurent De Baglion ◽  
Cédric Gourdin ◽  
Jean-Christophe Le Roux
Keyword(s):  
Fatigue Life ◽  
Surface Finish ◽  
Polished Surface ◽  
Design Curve ◽  
Fatigue Design ◽  
Wide Range ◽  
Asme Code ◽  
The Difference ◽  
The Uk ◽  
Technical Basis

Fatigue rules from ASME have undergone a significant change over the past decade, especially with the inclusion of the effects of BWR and PWR environments on the fatigue life of components. The incorporation of the environmental effects into the calculations is performed via an environmental factor, Fen, which is introduced in ASME BPV code-case N-792 [5], and depends on factors such as the temperature, dissolved oxygen and strain rate. Nevertheless, a wide range of factors, such as surface finish, have a deleterious impact on fatigue life, but their contribution to fatigue life is typically taken through the transition factors to build the fatigue design curve [2] and not in an explicit way, such as the Fen factor. The testing supporting the rules pertaining to Environmental Fatigue Correction Factor (Fen) Method in ASME BPV was performed on specimens with a polished surface finish and on the basis that the Fen factor was applicable without alteration of the historical practice of building the design curve through transition factors. The extensive amount of testing conducted and reported in References [2] and [7] (technical basis for ASME BPV current EAF rules) was used to propose a set of transition coefficients from the mean air curve to the design curve on one hand, and on the other hand to build a Fen factor expression, defined as the difference between the life in air and in PWR environments. The work initiated by AREVA in 2005 [9] [10] [11] demonstrated that there is a clear interaction between the two aggravating effects of surface finish and PWR environment for fatigue damage, which was not experimentally tested in the References [2] and [7]. These results have clearly been supported by testing carried out independently in the UK by Rolls-Royce and AMEC FW [12]. These results are all the more relevant as most NPP components do not have a polished surface finish. Most surfaces are either industrially polished or installed as-manufactured. It was concluded that this proposal could potentially be applicable to a wide range of components and could be of interest to a wider community. EDF/Areva/CEA have therefore authored a code-case introducing the Fen-threshold, a factor which explicitly quantifies the interaction between PWR environment and surface finish. This paper summarizes this proposal and provides the technical background and experimental work to justify this proposal.

Cumulative Damage in Fatigue—A Design Method Based on the S-N Curve

1957 ◽  
Vol 61 (559) ◽  
pp. 485-491 ◽  
Author(s):  
John C. Levy
Keyword(s):  
Stress Level ◽  
Extreme Values ◽  
Design Method ◽  
High Stress ◽  
Fatigue Tests ◽  
Three Dimensions ◽  
Average Value ◽  
Straight Line ◽  
Wide Range ◽  
Pull Tests

SummaryIt is suggested that a convenient way of presenting the results of fatigue tests in which two different stress amplitudes are applied alternately is to plot log N against log (n1/n) where N is the total cycles to failure and (n1/n) is the fraction of cycles run at the high stress.With these co-ordinates, a simple geometrical construction gives a safe design method for the two-stress level system using only the conventional S-N curve and the value of (n1/n) expected to be encountered in service. If N1 and N2 are the lives at the high and low stresses as read from the S-N curve, one point may be plotted at (log N1, 0) since this represents the programme when all cycles are at the high stress. On the assumption, shown to be justified, that less than one cycle of high stress per 10,000 total cycles would not significantly affect the life at the low stress, a second point is plotted at (log N2, 4). The straight line joining these two points is always found to predict safe values of N for any value of (n1/n).This conclusion is checked against a wide range of experimental results taken from six different sources in the literature covering rotating-bending and push-pull tests, ferrous and non-ferrous metals, any order of stressing and length of programme cycle from 50 up to 5 million. This last feature means that the length of the programme cycle in service need not be known. All that is required is the proportion in which the two stress amplitudes are mixed. The average value of the ratio (experimental life/predicted life) for the data examined is 1·8, the extreme values being 1 and 56. By plotting in three dimensions an equation is also developed for the three-stress level spectrum and a suggestion is made for an extension of the method to multiple stress levels.

Sensitivity of Estimated Tube Life to Material Property Variation

1983 ◽  
Vol 105 (1) ◽  
pp. 73-79 ◽  
Author(s):  
I. Berman ◽  
M. S. M. Rao
Keyword(s):  
Material Property ◽  
Failure Modes ◽  
Creep Damage ◽  
Cycle Number ◽  
Property Variation ◽  
Life Evaluation ◽  
Creep Fatigue ◽  
Incoloy 800 ◽  
Solar Receiver ◽  
Tube Life

The estimated tube life of the Incoloy 800 tubes of a solar receiver panel under nonaxisymmetric loading is compared for various material property assumptions. The basis of each life evaluation is an elastic-creep analytical study of up to 20 load cycles. The effect on tube life of a variation in the creep rate for the failure modes of creep ratcheting and creep fatigue is studied in some detail. As shown for these elastic-creep conditions, the creep damage and mean diametral strain accumulations per cycle decrease linearly over the calculated 20 cycles when plotted against cycle number on a log-log scale. The predictions of total creep damage and mean diametral strain in 10,000 cycles based on the extrapolated log-log scale curve are substantially lower than the predictions based on multiplication of the change in value of the 20th day of operation by 10,000. A limited evaluation of the effects of variations in other material parameters is also made.

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