Fatigue Crack Growth in Notched Parts With Compressive Mean Load

1972 ◽  
Vol 94 (1) ◽  
pp. 243-247 ◽  
Author(s):  
H. Saal
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Fracture Mechanics ◽  
Residual Stresses ◽  
Mild Steel ◽  
Crack Growth ◽  
Notch Root ◽  
Compressive Load ◽  
Notched Specimens ◽  
Mechanics Model

A fracture mechanics model is proposed to describe fatigue crack propagation in notched specimens. This model accounts for residual stresses which are present at the notch root after unloading from maximum compressive load. This is of particular interest for specimens subjected to compressive mean load. According to the model, cracks will stop growing at the boundary of the plastically deformed zone if the specimen is subjected to compressive load only. Validity of the model was verified with notched specimens of mild steel.

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.

Repercussion of Autofrettage on the Fatigue Crack Growth in the Vicinity of Catalyst Entry Opening for Polyethylene Autoclave Reactor

2015 ◽  
Author(s):  
Navid Haeri ◽  
Brian A. Cornah
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Fracture Mechanics ◽  
Residual Stresses ◽  
Crack Growth ◽  
Corner Crack ◽  
Linear Elastic ◽  
Study Results ◽  
The Impact ◽  
Autoclave Reactor

Background. The authors conducted a study to analyse the impact of autofrettage practice on the fatigue crack growth in the vicinity of the catalyst entry nozzle in a MK.15 ICI LDPE autoclave reactor. Methods. The authors created 3-D finite element models of the quadrant of the opening. Elastic-plastic analysis was carried out to evaluate the residual stresses from the autofrettage which were then used as an input to the fracture mechanics analysis. Linear Elastic Fracture Mechanics (LEFM) methodology was then deployed associating a Radial Direction, Quarter-Circular Corner Crack pattern as per API 579/ASME VIII Div.3 for the purpose of calculating the crack tip stress intensity. A number of hypothetical pressure cycles were considered in order to calculate the crack growth rate as per ASME Div.3 (Paris’ Law) both with and without residual stresses from autofrettage analysis. Results. The study results showed the change in the crack behaviour as a result of adding the autofrettage residual stresses onto the model and discussed the implications of such a practice on the design life for autoclave reactors.

Analysis of Corrosion Fatigue Crack Growth in Welded Tubular Joints

1985 ◽  
Vol 107 (2) ◽  
pp. 212-219 ◽  
Author(s):  
S. J. Hudak ◽  
O. H. Burnside ◽  
K. S. Chan
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Fracture Mechanics ◽  
Crack Growth ◽  
Corrosion Fatigue ◽  
Offshore Structures ◽  
Corrosion Fatigue Crack ◽  
Tubular Joints ◽  
Mechanics Model ◽  
Weld Toe

An improved fracture mechanics model for fatigue crack growth in welded tubular joints is developed. Primary improvements include the use of a wide-ranged equation for the fatigue crack growth rate properties and the incorporation of the influence of local weld-toe geometry into the stress intensity factor equations. The latter is shown to explain the dependence of the fatigue life on the size of tubular joints. Good agreement between predicted and measure fatigue lives of full-scale joints tested in air further supports the applicability of the fracture mechanics approach to offshore structures. Although the model should also be applicable to corrosion fatigue, additional imput data and verification testing are needed under these conditions. Factors which could improve the model are discussed.

Effect of Hardness and Tensile Mean Stress on Fatigue Crack Growth in Beryllium Copper

1969 ◽  
Vol 11 (3) ◽  
pp. 343-349 ◽  
Author(s):  
L. P. Pook
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Residual Stresses ◽  
Crack Growth ◽  
Fatigue Crack Growth Rate ◽  
Mean Stress ◽  
Growth Data ◽  
Beryllium Copper

Some fatigue crack growth data have been obtained for age-hardened beryllium copper. The fatigue crack growth rate was found to be very dependent on the hardness and tensile mean stress. This dependence is believed to be associated with the intense residual stresses surrounding Preston-Guinier zones.

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