Interaction Diagram for Time Dependent Fatigue

1983 ◽  
Vol 105 (4) ◽  
pp. 273-279 ◽  
Author(s):  
V. M. Radhakrishnan
Keyword(s):  
Fatigue Life ◽  
Loading Condition ◽  
Low Cycle Fatigue ◽  
Time Dependent ◽  
Cycle Fatigue ◽  
Interaction Diagram ◽  
Cycle Dependent ◽  
Propagation Stage ◽  
Dependent Interaction ◽  
Strain Hold

Interaction of fatigue with corrosion and creep has been analyzed through a parameter [Fi] introduced at the crack propagation stage. Assuming the effect of corrosion and creep to become dominant below a certain frequency, a model is proposed which is able to explain the stress-hold and the strain-hold effects on the fatigue life in time dependent fatigue. Beyond a certain period stress-hold leads to time-dependent and strain-hold leads to cycle-dependent interaction life. By suitably evaluating the parameter [Fi], life under any type of loading condition can be estimated. Based on the parameter, an interaction diagram is proposed for predicting the fatigue life in time dependent high temperature low cycle fatigue.

Frequency and Hold-Time Effects on Low Cycle Fatigue Life of Notched Specimens at Elevated Temperature

1989 ◽  
Vol 111 (1) ◽  
pp. 54-60 ◽  
Author(s):  
Masao Sakane ◽  
Masateru Ohnami ◽  
Teruyoshi Awaya ◽  
Nakao Shirafuji
Keyword(s):  
Fatigue Life ◽  
Low Cycle Fatigue ◽  
Hold Time ◽  
Strain Range ◽  
Fem Analysis ◽  
Time Dependent ◽  
Cycle Fatigue ◽  
Time Effects ◽  
Notched Specimens ◽  
Cycle Dependent

This paper describes the frequency and hold-time effects on high temperature low cycle fatigue for round notched specimens. Unnotched and notched specimens having different elastic stress concentration factors were fatigued under triangular and trapezoidal stress waves at frequencies ranging from 5 Hz to 0.0001 Hz at 873 K. The three specific fracture characteristics were observed: cycle dependent, time dependent, and cycle-time dependent. The respective notch sensitivity occurred in the respective fracture regime. The fatigue life of notched specimens was predicted from the elastic-plastic-creep cyclic FEM analysis using the linear damage rule and the strain range partitioning rule. Both the life prediction methods predicted the creep-fatigue life within almost a factor of two scatter band.

Effect of Surface Finish and Loading Conditions on the Low Cycle Fatigue Life of Stainless Steel Welded Piping in PWR Environment

2013 ◽  
Author(s):  
Yuichi Fukuta ◽  
Yuichiro Nomura ◽  
Seiji Asada
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Austenitic Stainless Steel ◽  
Surface Finish ◽  
Loading Condition ◽  
Low Cycle Fatigue ◽  
Complex Loading ◽  
Fatigue Tests ◽  
Cycle Fatigue ◽  
Effect Of Surface

NUREG/CR-6909 of USA and JSME of Japan proposed new rules for evaluating environmental effects in fatigue analyses of reactors components. These rules were established from a lot of fatigue data with polished specimens under simple loading condition. The effects of surface finish or complex loading condition were reported in some papers, but these data were obtained with the simple shaped specimens. In order to evaluate the effects of surface finish and loading condition and to confirm the applicability of the proposed rules to actual components, Low Cycle Fatigue tests are performed in PWR environment with the specimens cut from 316 austenitic stainless steel welded piping. The pipes are machined to have three levels of surface finish condition and the load pattern simulating the thermal stress is applied to specimens. In this study, the effect of surface finish on fatigue life is included to be small for 316 austenitic stainless steel welded piping. Considering the insensitive region in the current evaluation rule, predicted accuracy is increased and possibility of improving the current rule is indicated.

Flaw Tolerance Assessment for Low-Cycle Fatigue of Stainless Steel

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Masayuki Kamaya
Keyword(s):  
Fatigue Life ◽  
Intensity Factor ◽  
Crack Growth ◽  
Loading Condition ◽  
Low Cycle Fatigue ◽  
Fatigue Curve ◽  
Fatigue Tests ◽  
Strain Intensity ◽  
Cycle Fatigue ◽  
Flaw Tolerance

According to Appendix L of the Boiler and Pressure Vessel Code Section XI, flaw tolerance assessment is performed using the stress intensity factor (SIF) even for low-cycle fatigue. On the other hand, in Section III, the fatigue damage is assessed using the design fatigue curve (DFC), which has been determined from strain-based fatigue tests. Namely, the stress is used for the flaw tolerance assessment. In order to resolve this inconsistency, in the present study, the strain intensity factor was used for crack growth prediction. First, it was shown that the strain range was the key parameter for predicting the fatigue life and crack growth. The crack growth rates correlated well with the strain intensity factor even for the low-cycle fatigue. Then, the strain intensity factor was applied to predict the crack growth under uniform and thermal cyclic loading conditions. The estimated fatigue life for the uniform cyclic loading condition agreed well with that obtained by the low-cycle fatigue tests, while the fatigue life estimated for the cyclic thermal loading condition was longer. It was shown that the inspection result of “no crack” can be reflected to determining the future inspection time by applying the flaw tolerance analysis. It was concluded that the flaw tolerance concept is applicable not only to the plant maintenance but also to plant design. The fatigue damage assessment using the design fatigue curve can be replaced with the crack growth prediction.

Effects of compressive strain hold on low-cycle fatigue life at elevated temperatures

2009 ◽  
Vol 5 (2-3) ◽  
pp. 89-96
Author(s):  
Kazuo Kobayashi ◽  
Masao Hayakawa ◽  
Megumi Kimura ◽  
Koji Yamaguchi
Keyword(s):  
Fatigue Life ◽  
Elevated Temperatures ◽  
Low Cycle Fatigue ◽  
Compressive Strain ◽  
Cycle Fatigue ◽  
Strain Hold

Low-Cycle Corrosion Fatigue of Three Engineering Alloys in Salt Water

1988 ◽  
Vol 110 (3) ◽  
pp. 234-239 ◽  
Author(s):  
H. Bernstein ◽  
C. Loeby
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Corrosion Fatigue ◽  
Low Cycle Fatigue ◽  
Salt Water ◽  
Time Dependent ◽  
Cycle Fatigue ◽  
Plastic Strain Range ◽  
Fatigue Data ◽  
1045 Steel

Low-cycle fatigue tests were conducted under strain control in salt water on 2024 aluminum, 304 stainless steel, and 1045 steel. All three materials showed a significant reduction in life due to corrosion fatigue in the low-cycle fatigue regime. The corrosion fatigue life of the aluminum and steel was time dependent, with significantly shorter lives at lower frequencies or at longer strain hold times. The corrosion fatigue life of the stainless steel was not time dependent for the conditions studied. Elastic and plastic strain-range versus life equations were modified by a frequency term to predict the corrosion fatigue life. This model correlated the fatigue data to within a factor of 1.28. A modification of this model correlated some corrosion fatigue data in the literature to within a factor of 1.19.

Flaw Tolerance Assessment for Low-Cycle Fatigue of Stainless Steel

2015 ◽  
Author(s):  
Masayuki Kamaya
Keyword(s):  
Fatigue Life ◽  
Intensity Factor ◽  
Crack Growth ◽  
Loading Condition ◽  
Low Cycle Fatigue ◽  
Fatigue Curve ◽  
Fatigue Tests ◽  
Strain Intensity ◽  
Cycle Fatigue ◽  
Flaw Tolerance

According to Appendix L of the BPVC Section XI, flaw tolerance assessment is performed using the stress intensity factor even for low-cycle fatigue. On the other hand, in Section III, the fatigue damage is assessed using the design fatigue curve, which has been determined from strain-based fatigue tests. Namely, the stress is used for the flaw tolerance assessment, whereas the strain (Ke factor) is quoted for the design. In order to resolve this inconsistency, in the present study, the strain intensity factor was used for crack growth prediction. First, it was shown that the strain range was the key parameter for predicting the fatigue life and crack growth. The crack growth rates correlated well with the strain intensity factor even for the low-cycle fatigue. Then, the strain intensity factor was applied to predict the crack growth under uniform and thermal cyclic loading conditions. The estimated fatigue life for the uniform cyclic loading condition agreed well with that obtained by the low-cycle fatigue tests, while the fatigue life estimated for the cyclic thermal loading condition was longer. It was shown that the inspection result of “no crack” can be reflected to determining the future inspection time by applying the flaw tolerance analysis. It was concluded that the flaw tolerance concept is applicable not only to the plant maintenance but also to plant design. The fatigue damage assessment using the design fatigue curve can be replaced with the crack growth prediction.

Low-Cycle Fatigue Performance of Buckling Restrained Braces and Assessment of Cumulative Damage under Severe Earthquakes

2018 ◽  
Vol 763 ◽  
pp. 867-874
Author(s):  
Yu Shu Liu ◽  
Ke Peng Chen ◽  
Guo Qiang Li ◽  
Fei Fei Sun
Keyword(s):  
Fatigue Life ◽  
Energy Dissipation ◽  
Structural Reliability ◽  
Low Cycle Fatigue ◽  
Engineering Application ◽  
Fatigue Performance ◽  
Cycle Fatigue ◽  
Variable Amplitude ◽  
Buckling Restrained Braces ◽  
Energy Dissipation Devices

Buckling Restrained Braces (BRBs) are effective energy dissipation devices. The key advantages of BRB are its comparable tensile and compressive behavior and stable energy dissipation capacity. In this paper, low-cycle fatigue performance of domestic BRBs is obtained based on collected experimental data under constant and variable amplitude loadings. The results show that the relationship between fatigue life and strain amplitude satisfies the Mason-Coffin equation. By adopting theory of structural reliability, this paper presents several allowable fatigue life curves with different confidential levels. Besides, Palmgren-Miner method was used for calculating BRB cumulative damages. An allowable damage factor with 95% confidential level is put forward for assessing damage under variable amplitude fatigue. In addition, this paper presents an empirical criterion with rain flow algorithm, which may be used to predict the fracture of BRBs under severe earthquakes and provide theory and method for their engineering application. Finally, the conclusions of the paper were vilified through precise yet conservative prediction of the fatigue failure of BRB.

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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