An Artificial-Intelligence and Machine-Learning Based Methodology to Conduct Seemingly-Strain-Controlled Fatigue Test in a Pressurized-Water-Reactor-Test-Loop-Autoclave, While Not Controlling the Strain

2021 ◽  
Author(s):  
Subhasish Mohanty ◽  
Joseph Listwan
Keyword(s):  
Fatigue Test ◽  
Test Data ◽  
Nuclear Reactor ◽  
Low Cycle Fatigue ◽  
Cyclic Strain ◽  
Cyclic Hardening ◽  
Test Method ◽  
Displacement Sensor ◽  
Pressurized Water ◽  
Test Loop

Abstract In general, low cycle fatigue evaluation of nuclear reactor components requires strain-controlled fatigue test data such as using strain versus life (e-N) curves. Conducting strain-controlled fatigue tests under in-air condition is not an issue. However, controlling strain in a PWR water test is a challenge, since an extensometer cannot be placed in a narrow autoclave (typically used in a high-temperature-pressure PWR-water loop). This is due to lack of space inside an autoclave that houses the test specimen. In addition, installing a contact-type extensometer in the path of a high-pressure flow can be a challenge. These difficulty of using an extensometer in a PWR-water loop led us to use an outside-autoclave displacement sensor which measures the displacement of pull-rod-specimen assembly. However, in our study (based on in-air fatigue test data), we found that a pull-rod-controlled based fatigue test can lead to substantial cyclic hardening/softening resulting substantially different cyclic strain amplitudes and its rates compared to the desired cyclic strain amplitudes and its rates. In this paper, we propose an AI/ML based technique such as using k-Mean clustering technique to improve the pull-rod-control based fatigue test method, such that the gauge-area strain amplitude and rates can reasonably be achieved. In support of this we present the fatigue test results for both 316 SS base and 81/182 dissimilar-metal-weld specimens.

Environmental Fatigue Test of CF8M With a Small Autoclave Simulating PWR Conditions

2008 ◽  
Author(s):  
Il-Seok Jeong ◽  
Gag-Hyeon Ha ◽  
Tae-Ryoung Kim
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Low Cycle Fatigue ◽  
Test Procedure ◽  
Cyclic Strain ◽  
Fatigue Tests ◽  
Operating Conditions ◽  
Measuring Instruments ◽  
Pressurized Water Reactor ◽  
Pressurized Water

To develop a fatigue design curve of cast stainless steel CF8M used in primary piping material of nuclear power plants, low-cycle fatigue tests have been conducted by Korea Electric Power Research Institute (KEPRI). A small autoclave simulated the environment of a pressurized water reactor (PWR), 15 MPa and 315 °C. Fatigue life was measured in terms of the number of cycles with the variation of strain amplitudes at 0.04%/s strain rate. A small autoclave of 1 liter and cylindrical solid fatigue specimens were used for the strain-controlled low cycle environmental fatigue tests to make the experiments convenient. However, it was difficult to install displacement measuring instruments at the target length of the specimens inside the autoclave. To mitigate the difficulty displacement data measured at the shoulders of the specimen were calibrated based on the data relation of the target and shoulder length of the specimen during hot air test conditions. KEPRI developed a test procedure to perform low cycle environmental fatigue tests in the small autoclave. The procedure corrects the cyclic strain hardening effect by performing additional tests in high temperature air condition. KEPRI verified that the corrected test result agreed well with that of finite element method analysis. The process of correcting environmental fatigue data would be useful for producing reliable fatigue curves using a small autoclave simulating the operating conditions of a PWR.

Life evaluation of a combustion chamber by thermomechanical fatigue panel tests based on a creep fatigue and ductile damage model

2019 ◽  
Vol 29 (2) ◽  
pp. 226-245 ◽  
Author(s):  
Tadashi Masuoka ◽  
Jörg R Riccius
Keyword(s):  
High Temperature ◽  
Combustion Chamber ◽  
Fatigue Test ◽  
Test Data ◽  
Low Cycle Fatigue ◽  
Thermomechanical Fatigue ◽  
High Load ◽  
Cycle Fatigue ◽  
Damage Propagation ◽  
Damage Models

The inner liner of a combustion chamber of a cryogenic liquid rocket engine is exposed to a high load induced by the high temperature of the hot gas and the low temperature of the coolant. The high load causes some inelastic strain that accumulates with each operational cycle until the fracture or rupture of the inner liner. A model that can reproduce the propagation of damage under a thermally cycled load is essential for precisely predicting the chamber life. However, the damage propagation phenomenon or the quantitative value of the damage was so far not fully discussed using the damage data obtained from basic testing of a rocket chamber material. The purpose of the present study was to investigate a precise prediction model based on damage mechanics for simulating the damage propagation of a rocket chamber material. In this study, low cycle fatigue test data at a high temperature (900 K) were analyzed, and damage models that could reproduce the damage propagation under cyclic load conditions were investigated. Then the parameters were identified to reproduce uniaxial test data. These damage models were also subject to a finite element method analysis of a thermomechanical fatigue panel test in order to quantitatively evaluate the deformation, damage propagation, and life of a chamber wall. The analysis of low cycle fatigue test data at 900 K suggested a specific model that could precisely reproduce the damage propagation phenomenon and the basic material test data. From the results, it was confirmed that the model could predict the location of crack initiation.

Environmentally-Assisted Fatigue Behavior of 316 Stainless Steels in Simulated PWR Primary Environment: Strain Holding, Zn-Addition, and Their Combined Effect

2019 ◽  
Author(s):  
Hyeon Bae Lee ◽  
Ho-Sub Kim ◽  
Junjie Chen ◽  
Changheui Jang ◽  
Tae Soon Kim ◽  
...  
Keyword(s):  
Oxide Layer ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Cyclic Hardening ◽  
Combined Effect ◽  
Cyclic Behavior ◽  
Peak Strain ◽  
Pressurized Water ◽  
Hardening Behavior ◽  
Zn Addition

Abstract Low cycle fatigue (LCF) tests of type 316 stainless steel (SS) were conducted in simulated pressurized water reactor (PWR) environments to evaluate the effect of zinc (Zn) content and peak strain holding. The LCF lives of 316 SS increased about 2 to 3 times in PWR environments with Zn addition and peak strain holding (Zn-PWRhold condition). Their combined effect was investigated by using cyclic hardening behavior, dislocation structure analysis, and oxide layer observation. The cyclic behavior in Zn-PWRhold condition showed general primary hardening behavior but quite longer softening behavior than other test conditions. Also, the dislocation density was decreased with Zn addition and increased again with peak strain holding. The Zn penetrates into the oxide layer at the crack tip and modifies the oxide characteristics, which results in improvement of corrosion resistance.

scholarly journals Weibull and Bootstrap-Based Data-Analytics Framework for Fatigue Life Prognosis of the Pressurized Water Nuclear Reactor Component Under Harsh Reactor Coolant Environment

2019 ◽  
Vol 3 (1) ◽  
Author(s):  
Jae Phil Park ◽  
Subhasish Mohanty ◽  
Chi Bum Bahn ◽  
Saurin Majumdar ◽  
Krishnamurti Natesan
Keyword(s):  
Fatigue Life ◽  
Fatigue Test ◽  
Safety Factor ◽  
Test Data ◽  
Correction Factor ◽  
Data Analytics ◽  
Probabilistic Approach ◽  
Fatigue Curve ◽  
Pressurized Water ◽  
Best Fit

Abstract In general, the fatigue life of a safety critical pressure component is estimated using best-fit fatigue life curves (S-N curves). These curves are estimated based on underlying in-air condition fatigue test data. The best-fitting approach requires a large safety factor to accommodate the uncertainty associated with large scatter in fatigue test data. In addition to this safety factor, reactor component fatigue life prognostics requires an additional correction factor that in general is also estimated deterministically. This additional factor known as the environmental correction factor Fen is to cater the effect of the harsh coolant environment that severely reduces the life of these components. The deterministic Fen factor may also lead to further conservative estimation of fatigue life leading to unnecessary early retirement of costly reactor components. To address the above-mentioned issues, we propose a data-analytics framework which uses Weibull and Bootstrap probabilistic modeling techniques for explicitly quantifying the uncertainty/scatter associated with fatigue life rather than estimating the lives based on a best-fit based deterministic approach. We assume the proposed probabilistic approach would provide the first hand information for assessing the maximum and minimum effects of pressurized water reactor water on the reactor component. In the discussed approach, in addition to the probabilistic fatigue curves, we suggest using a probabilistic environment correction factor Fen. We assume the probabilistic fatigue curve and Fen would capture the S-N data scatter associated with the bulk effect of material grades, surface finish, strain rate, etc. on the material/component fatigue life.

scholarly journals Methodology for Stress-Controlled Fatigue Test Under In-Air and Pressurized Water Reactor Coolant Water Condition and to Evaluate the Effect of Pressurized Water Reactor Water and Loading Rate on Ratcheting

2018 ◽  
Vol 140 (3) ◽  
Author(s):  
Bipul Barua ◽  
Subhasish Mohanty ◽  
Joseph T. Listwan ◽  
Saurindranath Majumdar ◽  
Krishnamurti Natesan
Keyword(s):  
Loading Rate ◽  
Low Cycle Fatigue ◽  
Cyclic Hardening ◽  
Fatigue Loading ◽  
Stress Rate ◽  
Pressurized Water Reactor ◽  
Pressurized Water ◽  
Water Reactor ◽  
Water Test ◽  
Reactor Coolant Water

This work investigates the behavior of 316 stainless steel (SS) under stress-controlled low cycle fatigue loading. Several fatigue experiments are conducted under different environment such as in air at 300 °C and primary loop water conditions for a pressurized water reactor (PWR). Two different loading conditions are also employed to examine the effect of stress rate on material hardening and ratcheting. During PWR water test, actuator position measurements are used to determine the strain of the specimen. Under PWR environment, 316 SS is found to ratchet to a significantly greater degree compared with in air. At slow stress rate, higher amount of cyclic hardening is observed in 316 SS, and slow stress rate increases the rate of ratcheting. Results also indicate that 316 SS exhibits asymptotic strain response at higher stress loading which can cause material to behave very differently under same stress cyclic loading.

scholarly journals A Survey of Accelerated Vibratory Fatigue Test Method of Aero-Engine Compressor Blading

1985 ◽  
Author(s):  
Tie-Ying Wu ◽  
Qi-Xin Lu
Keyword(s):  
Fatigue Test ◽  
Statistical Methods ◽  
Test Data ◽  
T Test ◽  
Test Method ◽  
Life Distribution ◽  
F Test ◽  
Aero Engine ◽  
Engine Compressor

In this paper, a new accelerated fatigue test (AFT) method based on Miner’s Law is advanced, which is used for vibratory fatigue test of aero-engine compressor blading. By using this method, a sample life distribution can be obtained and it saves time about 50–60%. This approach is validated by experiments and the test data are compared by two statistical methods — namely, F-test and t-test.

scholarly journals Multiaxial Low Cycle Fatigue Test Method for Cruciform Specimen of Nickel-Base Single Crystal Superalloy

2011 ◽  
Vol 60 (12) ◽  
pp. 1130-1137 ◽  
Author(s):  
Noriaki MATSUDA ◽  
Masao SAKANE ◽  
Yuji OHATA ◽  
Morio YORIKAWA ◽  
Kouichi MASUNO ◽  
...  
Keyword(s):  
Single Crystal ◽  
Fatigue Test ◽  
Low Cycle Fatigue ◽  
Test Method ◽  
Single Crystal Superalloy ◽  
Cycle Fatigue ◽  
Cruciform Specimen ◽  
Nickel Base

Low Cycle Fatigue Behavior of Spray Formed Superalloy Rings

2011 ◽  
Vol 399-401 ◽  
pp. 1937-1941 ◽  
Author(s):  
Wen Yong Xu ◽  
Guo Qing Zhang ◽  
Zhou Li
Keyword(s):  
Strain Amplitude ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Hysteresis Loops ◽  
Cyclic Strain ◽  
Cyclic Hardening ◽  
Cyclic Stress ◽  
Total Strain ◽  
Total Strain Amplitude ◽  
Cycle Fatigue

Low cycle fatigue behavior of spray formed superalloy GH738 at 650°C has been investigated under fully reversed total strain-controlled mode. When strain amplitude (Δεt/2) is between 0.32% and 0.4%, cyclic stress response is stable under fully reversed constant total strain amplitude. The stabilized hysteresis loops narrowing sharply to a straight line indicates that the alloy exhibits typical elastic strain. The crack initiates single site from the surface. When strain amplitude is between 0.6% and 1.0%, cyclic hardening is observed until fracture. The tendency for hardening is found to increase with strain amplitude. The hyperesis loops expand gradually, which indicates that plastic deformation happens during cyclic deformation process. The crack initiates multi-sites from the surface. The cyclic strain-stress relationship of spray formed GH738 at 650°C can be illustrated by Δσ/2 =2017(Δεp/2)0.1489.The total strain-life function can expressed by Δεt/2=0.0071(2Nf)-0.0781+0.0647(2Nf) )-0.4914.

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