Direct Strain-Controlled Variable Strain Rate Low Cycle Fatigue Testing in Simulated PWR Water

2016 ◽  
Author(s):  
Tommi Seppänen ◽  
Jouni Alhainen ◽  
Esko Arilahti ◽  
Jussi Solin
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Strain Rate ◽  
Fatigue Testing ◽  
Low Cycle Fatigue ◽  
Reference Value ◽  
Hot Water ◽  
Feedback Signal ◽  
Cycle Fatigue ◽  
Experimental Values

A tailored-for-purpose environmental fatigue testing facility was previously developed to perform direct strain-controlled tests on stainless steel in simulated PWR water. Strain in specimen mid-section is generated by the use of pneumatic bellows, and eddy current measurement is used as a feedback signal. The procedure conforms with the ASTM E 606 practice for low cycle fatigue, giving results which are directly compatible with the major NPP design codes. Past studies were compiled in the NUREG/CR-6909 report and environmental reduction factors Fen were proposed to account for fatigue life reduction in hot water as compared to a reference value in air. This database exclusively contained non-stabilized stainless steels, mainly tested under stroke control. The applicability of the stainless steel Fen factor for stabilized alloys was already challenged in past papers (PVP2013-97500, PVP2014-28465). The results presented in this paper follow the same overall trend of lower experimental values (4.12–11.46) compared to those expected according to the NUREG report (9.49–10.37). In this paper results of a dual strain rate test programme on niobium stabilized AISI 347 type stainless steel are presented and discussed in the context of the NUREG/CR-6909 Fen methodology. Special attention is paid to the effect of strain signal on fatigue life, which according to current prediction methods does not affect the value of Fen.

Strain Waveform Effects for Low Cycle Fatigue in Simulated PWR Water

2017 ◽  
Author(s):  
Tommi Seppänen ◽  
Jouni Alhainen ◽  
Esko Arilahti ◽  
Jussi Solin
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Fatigue Testing ◽  
Low Cycle Fatigue ◽  
Reference Value ◽  
Steel Specimen ◽  
Feedback Signal ◽  
Test Results ◽  
Testing Facility ◽  
Reference Curves

In order to perform design code (ASME III, RCC-M, JSME) compatible direct strain-controlled tests in simulated PWR water, a unique environmental fatigue testing facility was previously developed. Pneumatic bellows are used to generate strain in the stainless steel specimen mid-section, while eddy current based measurement is used as a feedback signal. The NUREG/CR-6909 report gathered a large database of test results and proposed environmental reduction factors (Fen) to account for a reduction in fatigue life in simulated LWR environment when comparing to a reference value in air. The database was composed of non-stabilized stainless steels tested using methods which are not directly comparable to those used in air to define the reference curves. Applicability of the stainless steel Fen factors has already been challenged in previous PVP papers (PVP2013-97500, PVP2014-28465, PVP2016-63294). Results in this paper continue to show this trend of lower experimental Fen factors compared to predictions made by the NUREG report. Dual strain rate tests were performed, specifically focusing on the effect of strain waveform shape on fatigue life. Similarly to last year’s results (PVP2016-63294) a distinct effect of strain waveform, presently inadequately accounted for in Fen predictions, was observed.

scholarly journals Fatigue life time modelling of Cu and Au fine wires

2018 ◽  
Vol 165 ◽  
pp. 06002
Author(s):  
Golta Khatibi ◽  
Ali Mazloum-Nejadari ◽  
Martin Lederer ◽  
Mitra Delshadmanesh ◽  
Bernhard Czerny
Keyword(s):  
Fatigue Life ◽  
Strain Rate ◽  
High Cycle Fatigue ◽  
Fatigue Testing ◽  
Low Cycle Fatigue ◽  
Load Ratio ◽  
Life Time ◽  
Material Model ◽  
Cycle Fatigue ◽  
Rate Dependency

In this study, the influence of microstructure on the cyclic behaviour and lifetime of Cu and Au wires with diameters of 25μm in the low and high cycle fatigue regimes was investigated. Low cycle fatigue (LCF) tests were conducted with a load ratio of 0.1 and a strain rate of ~2e-4. An ultrasonic resonance fatigue testing system working at 20 kHz was used to obtain lifetime curves under symmetrical loading conditions up to very high cycle regime (VHCF). In order to obtain a total fatigue life model covering the low to high cycle regime of the thin wires by considering the effects of mean stress, a four parameter lifetime model is proposed. The effect of testing frequency on high cycle fatigue data of Cu is discussed based on analysis of strain rate dependency of the tensile properties with the help of the material model proposed by Johnson and Cook.

Low Cycle Fatigue of Nuclear Pipe Components

1974 ◽  
Vol 96 (3) ◽  
pp. 171-176 ◽  
Author(s):  
J. D. Heald ◽  
E. Kiss
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Room Temperature ◽  
Fatigue Testing ◽  
Low Cycle Fatigue ◽  
304 Stainless Steel ◽  
Code Design ◽  
Hydraulic Pressure ◽  
Cycle Fatigue ◽  
Cyclic Bending

This paper presents the results of low-cycle fatigue testing and analysis of 26 piping components and butt-welded sections. The test specimens were fabricated from Type-304 stainless steel and carbon steel, materials which are typically used in the primary piping of light water nuclear reactors. Components included 6-in. elbows, tees, and girth butt-welded straight sections. Fatigue testing consisted of subjecting the specimens to deflection-controlled cyclic bending with the objective of simulating system thermal expansion type loading. Tests were conducted at room temperature and 550 deg F, with specimens at room temperature subjected to 1050 psi constant internal hydraulic pressure in addition to cyclic bending. In two tests at room temperature, however, stainless steel elbows were subjected to combined simultaneous cyclic internal pressure and cyclic bending. Predictions of the fatigue life of each of the specimens tested have been made according to the procedures specified in NB-3650 of Section III[1] in order to assess the code design margin. For the purpose of the assessment, predicted fatigue life is compared to actual fatigue life which is defined as the number of fatigue cycles producing complete through-wall crack growth (leakage). Results of this assessment show that the present code fatigue rules are adequately conservative.

Influence of the Strain Rate on the Low Cycle Fatigue Life of an Austenitic Stainless Steel with a Ground Surface Finish in Different Environments

2014 ◽  
Vol 891-892 ◽  
pp. 1320-1326 ◽  
Author(s):  
Thibault Poulain ◽  
José Mendez ◽  
Gilbert Hénaff ◽  
Laurent de Baglion
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Austenitic Stainless Steel ◽  
Strain Rate ◽  
Surface Finish ◽  
Power Plants ◽  
Low Cycle Fatigue ◽  
Total Strain Amplitude ◽  
Cycle Fatigue ◽  
Pressurized Water

This paper focuses on the influence of strain rate in Low Cycle Fatigue (LCF) of a 304L austenitic stainless steel at 300 °C in different environments (secondary vacuum, air and Pressurized Water Reactor (PWR) water environment). Moreover test samples are ground to obtain a surface finish rougher than all that could be found in nuclear power plants. Different strain rates (4x10-3, 1x10-4and 1x10-5s-1) are studied, with a triangular waveform at a total strain amplitude of ±0.6%. The influence of strain rate on cyclic stress-strain behavior and fatigue life is firstly analyzed in secondary vacuum, considered as a non-active environment. Then, interactions between stain rate and environmental effects in Air and in PWR environment are presented. In all environments, a decrease in strain rate leads to a negative strain rate dependence of the stress response and a reduction in fatigue life. Finally, SEM observations of fatigue striations in PWR environment indicate a crack propagation rate enhancement when the strain rate is decreased.

scholarly journals Dependence of Temperature and Strain Rate on the Low-Cycle Fatigue Life of Type 321 Stainless Steel

1978 ◽  
Vol 64 (8) ◽  
pp. 1199-1208 ◽  
Author(s):  
Koji YAMAGUCHI ◽  
Kenji KANAZAWA ◽  
Susumu YOSHIDA
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Strain Rate ◽  
Low Cycle Fatigue ◽  
Cycle Fatigue

scholarly journals Fatigue Testing of Wearable Sensing Technologies: Issues and Opportunities

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4070
Author(s):  
Andrea Karen Persons ◽  
John E. Ball ◽  
Charles Freeman ◽  
David M. Macias ◽  
Chartrisa LaShan Simpson ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Prediction Models ◽  
Fatigue Testing ◽  
Low Cycle Fatigue ◽  
Wearable Sensors ◽  
Fatigue Tests ◽  
Proof Of Concept ◽  
Cycle Fatigue ◽  
Wearable Sensing ◽  
Failure Data

Standards for the fatigue testing of wearable sensing technologies are lacking. The majority of published fatigue tests for wearable sensors are performed on proof-of-concept stretch sensors fabricated from a variety of materials. Due to their flexibility and stretchability, polymers are often used in the fabrication of wearable sensors. Other materials, including textiles, carbon nanotubes, graphene, and conductive metals or inks, may be used in conjunction with polymers to fabricate wearable sensors. Depending on the combination of the materials used, the fatigue behaviors of wearable sensors can vary. Additionally, fatigue testing methodologies for the sensors also vary, with most tests focusing only on the low-cycle fatigue (LCF) regime, and few sensors are cycled until failure or runout are achieved. Fatigue life predictions of wearable sensors are also lacking. These issues make direct comparisons of wearable sensors difficult. To facilitate direct comparisons of wearable sensors and to move proof-of-concept sensors from “bench to bedside,” fatigue testing standards should be established. Further, both high-cycle fatigue (HCF) and failure data are needed to determine the appropriateness in the use, modification, development, and validation of fatigue life prediction models and to further the understanding of how cracks initiate and propagate in wearable sensing technologies.

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