An assessment of the crack tip opening displacement criterion for predicting creep crack growth

1996 ◽  
Vol 77 (1) ◽  
pp. 29-40 ◽  
Author(s):  
L. Xia ◽  
T. H. Hyde ◽  
A. A. Becker
Keyword(s):  
Crack Growth ◽  
Creep Crack Growth ◽  
Crack Tip ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Creep Crack ◽  
Crack Tip Opening

The Inelastic Line-Spring: Estimates of Elastic-Plastic Fracture Mechanics Parameters for Surface-Cracked Plates and Shells

1981 ◽  
Vol 103 (3) ◽  
pp. 246-254 ◽  
Author(s):  
D. M. Parks
Keyword(s):  
Fracture Mechanics ◽  
Crack Growth ◽  
Computing Time ◽  
Crack Tip ◽  
J Integral ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Elastic Plastic ◽  
Plates And Shells ◽  
Crack Tip Opening

Recent studies of the mechanics of elastic-plastic and fully plastic crack growth suggest that such parameters as the J-integral and the crack tip opening displacement can, under certain conditions, be used to correlate the initiation and early increments of the ductile tearing mode of crack growth. To date, elastic-plastic fracture mechanics has been applied mainly to test specimen geometries, but there is a clear need for developing practical analysis capabilities in structures. In principle, three-dimensional elastic-plastic finite element analysis could be performed, but, in fact, such analyses would be prohibitively expensive for routine application. In the present work, the line-spring model of Rice and Levy [1-3] is extended to estimate the J-integral and crack tip opening displacement for some surface crack geometries in plates and shells. Good agreement with related solutions is obtained while using orders of magnitude less computing time.

scholarly journals Digital Image Correlation (DIC) Technique for Fatigue Crack Growth Analysis Using ∆CTOD Criteria

2018 ◽  
Vol 7 (4.38) ◽  
pp. 1362
Author(s):  
Akshay B. Patil ◽  
Suraj P. Toppo ◽  
Dr. RKP Singh
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Digital Image Correlation ◽  
Crack Growth ◽  
Digital Image ◽  
Crack Tip ◽  
Image Correlation ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Crack Tip Opening

The present paper deals with an experimental determination of fatigue crack growth rate (FCGR) of microalloyed steel (38MnVS6) to study the crack propagation in forged automobile crankshafts. The criterion based on crack tip opening displacement range (∆CTOD) is used to investigate the fatigue crack growth rate. In the current work use of 2D-digital image correlation (DIC) technique for the measurement of crack tip opening displacement (CTOD) and crack length (a) is proposed. Digital Image Correlation (DIC) is a full field displacement and strain measurement technique. It is easier to measure the crack tip opening displacement (CTOD) and crack length (a) with this technique than other. Fatigue crack growth curve based on crack tip opening displacement (CTOD) criteria is presented using DIC.  

A Nonlinear Analysis of an Equilibrium Craze: Part II—Simulations of Craze and Crack Growth

1988 ◽  
Vol 55 (1) ◽  
pp. 52-58 ◽  
Author(s):  
T. Ungsuwarungsri ◽  
W. G. Knauss
Keyword(s):  
Crack Growth ◽  
Crack Tip ◽  
Energy Dissipation Rate ◽  
Crack Model ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Critical Crack ◽  
Dugdale Model ◽  
Nonlinear Force ◽  
Crack Tip Opening

In this study we investigate the effects of nonlinear fibril behavior on the mechanics of craze and crack growth. The effect of strain-softening cohesive material on crack stability is of particular interest and is examined via a craze and crack model developed in the first part of this work where the formulation and solution of the problem are discussed.1 In this second part, quasi-static growth of a craze with a central crack is analyzed for different nonlinear force-displacement (p-v) relations for the craze fibrils. A “critical crack tip opening displacement” (CTOD), or more precisely, “critical fibril extension” is employed as the criterion for fracture. The p-v relation is further assumed to be invariant with respect to the craze and crack lengths. The results are compared with the Dugdale model; the craze zone size and the energy dissipation rate approach asymptotic values in the limit of long cracks. The problem of craze growth from a precut crack under increasing far-field loading is then studied. In the case where the p-v relation is monotonically softening, the crack can start to grow in an unstable manner before the crack tip opening displacement reaches its critical value.

Use of the reference stress concept to assess the effect of crack growth increment size on the accuracy of creep crack grow predictions

1986 ◽  
Vol 21 (2) ◽  
pp. 109-115
Author(s):  
T H Hyde ◽  
K C Low
Keyword(s):  
Finite Element ◽  
Crack Growth ◽  
Creep Crack Growth ◽  
Growth Increment ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Moving Crack ◽  
Critical Crack ◽  
Creep Crack ◽  
Reference Stress

An approximate method, based on the reference stress concept, for carrying out ‘moving-crack’ calculations, under creep conditions, is presented. Creep crack growth is assumed to be related to the C∗ parameter. The predictions obtained correlate well with detailed, ‘moving-crack’, finite element calculations. Preliminary calculations, to assess the adequacy of finite element meshes and the effect of variations in material properties on the accuracy of predictions, can be carried out quickly and relatively cheaply. The usefulness of the technique is illustrated by using it to show the effect of the magnitude of the crack growth increment assumed and of the value of critical crack tip opening displacement (the initiation parameter assumed) used.

Why Conduct SEN(T) Tests and Considerations in Conducting/Analyzing SEN(T) Testing

2010 ◽  
Author(s):  
S. Kalyanam ◽  
G. M. Wilkowski ◽  
D.-J. Shim ◽  
F. W. Brust ◽  
Y. Hioe ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Crack Growth ◽  
Traditional Approach ◽  
Crack Tip ◽  
Maximum Load ◽  
Single Edge ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Growing Crack ◽  
Crack Tip Opening

This paper outlines a methodology used to conduct a SEN(T) fracture test and discusses the analysis procedure used to obtain J-R and CTOD-R resistance curves from the experimental data. The CTOD-R curve depicts the change in toughness with crack growth, in a manner similar to the J-R curve methodology. Significant crack growth can arise from the start of ductile tearing to maximum load in the case of surface-cracked pipes with heavier-wall piping used in recent designs of natural gas pipelines that are required to handle greater pressures and much lower temperatures. CTOD-R curves provide toughness values that are a factor of 2 to 3 times higher at maximum load when compared to the toughness at crack initiation. The impacts of this on stress and strain-based design of pipelines are highlighted. Further, the differences between the traditional approach that uses the crack-tip-opening-displacement at the initial crack tip (CTOD′) versus the more recent developments that employ the crack-tip-opening-displacement at the growing crack tip (CTOD) are examined. The CTOD-R curve for the growing crack tip is more consistent with J-R curve analyses. Single-edge-notched bend [SEN(B)] or popularly called bend-bar specimens are used for crack-tip-opening-displacement (CTOD) as well as J-integral toughness testing. This paper discusses the advantages of using the fracture toughness data determined from a single-edge-notched tension [SEN(T)] specimen from considerations of the constraints faced by surface cracks in pipelines and the differences in fracture toughness values seen between the SEN(T) and SEN(B) specimens in the transition temperature region.

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