Cyclic fatigue crack growth of silicon nitride under a constant maximum stress intensity

1995 ◽  
Vol 14 (4) ◽  
pp. 241-243 ◽  
Author(s):  
G. Choi
Keyword(s):  
Fatigue Crack ◽  
Stress Intensity ◽  
Silicon Nitride ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Maximum Stress ◽  
Cyclic Fatigue ◽  
Maximum Stress Intensity ◽  
Constant Maximum

Consideration on Fatigue Crack Growth Thresholds Under Negative Stress Ratio

2019 ◽  
Author(s):  
Kunio Hasegawa ◽  
Saburo Usami ◽  
Valery Lacroix
Keyword(s):  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Intensity Factor ◽  
Crack Growth ◽  
Stress Ratio ◽  
Maximum Stress ◽  
Maximum Stress Intensity ◽  
Maximum Stress Intensity Factor

Abstract Fatigue crack growth thresholds ΔKth are provided by several fitness-for-service (FFS) codes. When evaluating cracked components subjected to cyclic loading, maximum stress intensity factor Kmax and/or minimum stress intensity factor Kmin are required. However, the definitions of the thresholds ΔKth under negative stress ratio R are not clearly written, except for BS (British Standards) 7910. In addition, the ΔKth are given by constant values under negative R. Fatigue crack growth rates under negative stress ratio is recommended to use maximum stress intensity factor Kmax by ASTM (American Society of Testing and Materials) E 647, because of the Kmax being close to crack driving force. Therefore, it deems that the ΔKth under negative R seems to be Kmax. This paper shows that the Kmax converted by the ΔKth are not constant values under negative R based on the survey of experimental data. The Kmax decreases with decreasing the stress ratio R. Therefore, the ΔKth for the FFS codes are less conservative. As experimental data under negative stress ratio R were taken by Kmax – Kmin, the definition of the threshold ΔKth is benefit to use Kmax – Kmin, instead of Kmax.

Cyclic fatigue crack growth tests in silicon nitride using a small bending specimen with a micro notch

2003 ◽  
Vol 2003.78 (0) ◽  
pp. _2-21_-_2-22_
Author(s):  
Atsushi SUGETA ◽  
Masahiro JONO ◽  
Yoshihiko UEMATSU ◽  
Shuhei FUJITA ◽  
Tomoya OKANO
Keyword(s):  
Fatigue Crack ◽  
Silicon Nitride ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Cyclic Fatigue

scholarly journals Fatigue Crack Growth Thresholds at Negative Stress Ratio for Ferritic Steels in ASME Code Section XI

2019 ◽  
Vol 141 (3) ◽  
Author(s):  
Kunio Hasegawa ◽  
Bohumir Strnadel ◽  
Saburo Usami ◽  
Valery Lacroix
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Stress Ratio ◽  
Maximum Stress ◽  
Ferritic Steels ◽  
Intensity Factors ◽  
Asme Code ◽  
Maximum Stress Intensity ◽  
Stress Ratios

Thresholds of fatigue crack growth rates are important characteristics for fatigue crack growth assessment for the integrity of structural components. ASME Code Section XI provides fatigue crack growth thresholds for ferritic steels in air and water environments. The threshold is given as a constant value under a negative stress ratio. However, the thresholds are not clearly defined in the range of negative stress ratios. The definition seems to be maximum stress intensity factors. Besides, the thresholds expressed by the maximum stress intensity factors decrease with decreasing stress ratios. This means that the thresholds under negative stress ratios become unconservative assessments. The objective of this paper is to discuss the definition of fatigue crack growth threshold and to propose the threshold equation for the ASME Code Section XI, based on experimental data obtained from a literature survey.

Effective Modeling of Fatigue Crack Growth in Pipelines

2012 ◽  
Author(s):  
Steven J. Polasik ◽  
Carl E. Jaske
Keyword(s):  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Fracture Mechanics ◽  
Crack Growth ◽  
Growth Models ◽  
Critical Parameters ◽  
Operating Pressure ◽  
Mechanics Model ◽  
Key Variables

Pipeline operators must rely on fatigue crack growth models to evaluate the effects of operating pressure acting on flaws within the longitudinal seam to set re-assessment intervals. In most cases, many of the critical parameters in these models are unknown and must be assumed. As such, estimated remaining lives can be overly conservative, potentially leading to unrealistic and short reassessment intervals. This paper describes the fatigue crack growth methodology utilized by Det Norske Veritas (USA), Inc. (DNV), which is based on established fracture mechanics principles. DNV uses the fracture mechanics model in CorLAS™ to calculate stress intensity factors using the elastic portion of the J-integral for either an elliptically or rectangularly shaped surface crack profile. Various correction factors are used to account for key variables, such as strain hardening rate and bulging. The validity of the stress intensity factor calculations utilized and the effect of modifying some key parameters are discussed and demonstrated against available data from the published literature.

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