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.

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.

A Study of the Low Cycle Fatigue Characteristics of Annealed AISI 347 Stainless Steel And Overaged 6951-T6 Aluminum Push-Pull Specimens

1977 ◽  
Vol 99 (3) ◽  
pp. 391-398
Author(s):  
J. A. Friedericy ◽  
R. F. Graves
Keyword(s):  
Stainless Steel ◽  
Stress Field ◽  
Room Temperature ◽  
Elastic Limit ◽  
Fatigue Testing ◽  
Low Cycle Fatigue ◽  
Cyclic Stress ◽  
Test Machine ◽  
Cycle Fatigue ◽  
Temperature Levels

In a cyclic application the Neuber theory becomes the Wetzel-Morrow approach. The Neuber theory for stresses and strains in a notch is extended to apply to specimens for which the nominal stresses and strains in the material in the field adjacent to the notch may exceed the elastic limit. Also, when the cyclic nominal stresses and strains exceed the elastic or proportional limit of the materials, this extension can be applied if a mechanism external to the nominal stress field is applied to cause the stress field to change in a predetermined manner for each successive cycle. In the case of a notched push-pull specimen, the external mechanism would be a tensile test machine and the field adjacent to the notch would be that of the nominally induced stresses and strains by means of the machine. The state of stress and strain in the notch is the result of the shape and size of the notch as well as the nominal stresses and strains adjacent to the notch. A supporting test program is discussed which dealt with the low cycle fatigue testing of two metals, AISI 347 stainless steel and 6951-T6 aluminum. A push-pull specimen was used which was designed to handle fully reversed cyclic loads from 100 cycles on up. Both fatigue and cyclic stress-strain tests were performed. The strain ranges predicted by the extended theory were inserted in the Universal Slopes equation and the cyclic lives of the specimens at various applied stress levels were determined, including those exceeding the elastic limit of the material. Good correlation was obtained between theory and experiment at the temperature levels tested. The steel specimens were tested at room temperature and 1000°F (537°C) and the aluminum specimens at room temperature and 300°F (149°C).

Low-Cycle Fatigue Life Prediction by a New Critical-Plane Method

2008 ◽  
Vol 385-387 ◽  
pp. 209-212
Author(s):  
Dan Jin ◽  
Jian Hua Wu ◽  
Yang Zhang
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Weight Function ◽  
Life Prediction ◽  
Low Cycle Fatigue ◽  
304 Stainless Steel ◽  
Cycle Fatigue ◽  
Critical Plane ◽  
Plane Method ◽  
Rainflow Cycle Counting

A series of low-cycle fatigue experiments of axial-torsional loading of variable amplitudes were performed on the tubular specimens of 304 stainless steel. Two models of multiaxial low-cycle fatigue life, KBM and FS method, are evaluated based on the fatigue life data of 304 stainless steel. Rainflow cycle counting and the Liner Damage Rule are used to calculate fatigue damage. It was shown that the part prediction results are nonconservative for the two models. The life prediction is done again based on the weight function critical plane method for the two models. The prediction results are better by using the weight function critical plane method than the previous results for KBM model. But the prediction results are improved little for FS model in spite of the weight function critical plane method being used.

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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