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.

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.

scholarly journals Fatigue Growth Models for Multiple Long Cracks in Plates under Cyclic Tension Based on ΔKI, ΔJ-Integral and ΔCTOD Parameter

2011 ◽  
Vol 488-489 ◽  
pp. 525-528 ◽  
Author(s):  
Željko Božić ◽  
Siegfried Schmauder ◽  
Marijo Mlikota
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Fracture Mechanics ◽  
Crack Growth ◽  
Steel Plate ◽  
Growth Models ◽  
Fatigue Tests ◽  
Collinear Cracks ◽  
Cyclic Tension ◽  
Multiple Site Damage

This paper presents the implementation of fatigue crack growth power law equations based on ΔK,ΔJ-integral andΔCTODfracture mechanics parameters determined in an FE analysis, to plates with multiple site damage (MSD). Results of fatigue tests with constant amplitude tensile loading carried out on mild steel plate specimens damaged with a single central crack and with three collinear cracks are presented. A relatively larger plastic zone occurred in the crack tip region at higher fatigue crack growth rate (FCGR), from 10-7to 10-6m/cycle. The crack growth models based on the elastic-plastic fracture mechanics (EPFM) parameters describe better fatigue crack growth in this range as compared to the liner elastic models.

scholarly journals Application of a New, Energy-Based ΔS* Crack Driving Force for Fatigue Crack Growth Rate Description

Materials ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 518 ◽  
Author(s):  
Grzegorz Lesiuk
Keyword(s):  
Stress Intensity Factor ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Crack Growth ◽  
Engineering Practice ◽  
Stress Effect ◽  
New Energy

This paper presents the problem of the description of fatigue cracking development in metallic constructional materials. Fatigue crack growth models (mostly empirical) are usually constructed using a stress intensity factor ΔK in linear-elastic fracture mechanics. Contrary to the kinetic fatigue fracture diagrams (KFFDs) based on stress intensity factor K, new energy KFFDs show no sensitivity to mean stress effect expressed by the stress ratio R. However, in the literature there is a lack of analytical description and interpretation of this parameter in order to promote this approach in engineering practice. Therefore, based on a dimensional analysis approach, ΔH is replaced by elastic-plastic fracture mechanics parameter—the ΔJ-integral range. In this case, the invariance from stress is not clear. Hence, the main goal of this paper is the application of the new averaged (geometrically) strain energy density parameter ΔS* based on the relationship of the maximal value of J integral and its range ΔJ. The usefulness and invariance of this parameter have been confirmed for three different metallic materials, 10HNAP, 18G2A, and 19th century puddle iron from the Eiffel bridge.

A two-parameter fracture mechanics model for fatigue crack growth in brittle materials

2014 ◽  
Vol 119 ◽  
pp. 132-147 ◽  
Author(s):  
Sergii G. Kravchenko ◽  
Oleksandr G. Kravchenko ◽  
C.T. Sun
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Fracture Mechanics ◽  
Crack Growth ◽  
Brittle Materials ◽  
Mechanics Model ◽  
Two Parameter

Fatigue Pre-Cracking Curved Wide Plates in Bending

2010 ◽  
Author(s):  
Mark D. Richards ◽  
Timothy S. Weeks ◽  
J. David McColskey ◽  
Bo Wang ◽  
Yong-Yi Wang
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Fracture Mechanics ◽  
Stress Field ◽  
Crack Growth ◽  
Field Analysis ◽  
Four Point Bending ◽  
Stress Field Analysis

Curved wide plate (CWP) testing in tension, on API 5L X100 pipes of 36-inch (916-mm) diameter and 0.75-inch (19-mm) wall thickness, has been initiated in support of strain-based design using high strength steel for oil and gas pipeline applications. The CWP tests are being used to optimize and validate welding procedures and to determine the defect tolerance within the girth welds. A traditional pre-requisite for fracture mechanics testing is a final extension of a crack via fatigue pre-cracking to produce a representative flaw. A method of fatigue pre-cracking CWP specimens for final notch preparation in bending was developed to meet ASTM guidelines for fracture mechanics testing. Fatigue pre-cracking for the present specimen geometry was possible in bending due to lower requisite force capacity equipment which allowed for greater cyclic loading frequencies. In order to achieve sufficient stress levels for fatigue crack growth in the curved plate, a stress field analysis was performed to optimize the loading support configuration in four-point bending. In addition to the stress field analysis, a 3-D finite element model of the CWP specimen was generated to analyze the notched CWP specimen in four-point bending. Finite element analysis (FEA) results and experimental data were used to confirm the hypothesis that, under the proposed loading arrangement, the closed-form solutions for stress-intensity (K) of flat plates in bending can be used to approximate the K for CWP specimens in bending. Validation of a solution for stress-intensity factor subsequently allowed the determination of force amplitude levels for fatigue crack growth. Force and crack mouth opening displacement (CMOD) data were analyzed to correlate compliance with crack length measurements. From experimental results, a method was developed that enable the repeatable and well characterized extension of surface flaws by fatigue pre-cracking in curved wide plate specimens in bending.

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.

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