J-Integral and Crack Opening Displacement as Crack Initiation Criteria in Rubber

1986 ◽  
Vol 59 (5) ◽  
pp. 787-799 ◽  
Author(s):  
R. F. Lee ◽  
J. A. Donovan
Keyword(s):  
Crack Initiation ◽  
Carbon Black ◽  
Crack Growth ◽  
Crack Opening ◽  
Crack Tip ◽  
J Integral ◽  
Carbon Black Content ◽  
Opening Displacement ◽  
Critical Crack ◽  
Growth Initiation

Abstract 1. Evaluation of ∫σdδ where σ is the net section stress and δ is the deformed crack tip diameter requires only one specimen to characterize the initiation of crack growth in unfilled and carbon-black-filled NR. 2. ∫σdδ is equal to one half of the J-integral for crack growth initiation, which is identical to the Thomas tearing energy for a blunt notch. 3. The critical J-integral for crack initiation increases linearly with carbon black content. 4. The critical crack tip radius for crack initiation is independent of carbon black content, and the required crack tip region stress increases linearly with carbon black content.

J-Integral and Crack Opening Displacement as Crack Initiation Criteria in Natural Rubber in Pure Shear and Tensile Specimens

1987 ◽  
Vol 60 (4) ◽  
pp. 674-688 ◽  
Author(s):  
R. F. Lee ◽  
J. A. Donovan
Keyword(s):  
Crack Initiation ◽  
Carbon Black ◽  
Pure Shear ◽  
Crack Opening ◽  
Crack Size ◽  
J Integral ◽  
Carbon Black Content ◽  
Opening Displacement ◽  
Critical Crack ◽  
Tip Radius

Abstract For PS and SEN specimens: 1) Jδ (one half Jθ) can be determined from one specimen and is independent of crack size and specimen geometry. 2) J and T at initiation differed. 3) J at initiation increased with carbon black content, but the critical crack-tip radius did not.

Test for Crack Opening Displacement of Steel Fiber Reinforced Concrete under Three-Point Bending

2010 ◽  
Vol 36 ◽  
pp. 157-161 ◽  
Author(s):  
Tin Gyi Zhang ◽  
Yuan Bao Leng ◽  
Dan Ying Gao
Keyword(s):  
Crack Opening Displacement ◽  
Crack Opening ◽  
Mouth Opening ◽  
Crack Tip ◽  
Crack Mouth Opening Displacement ◽  
Crack Tip Opening Displacement ◽  
Opening Displacement ◽  
Critical Crack ◽  
Critical Crack Opening ◽  
Crack Tip Opening

Based on the principle of electrical measurement method, the clip gauge was made to measure the crack opening displacement (COD).Through the three-point bending test on the specimens of steel fiber reinforced high strength concrete (SFHSC), the effect of the fiber volume fraction (ρf) upon the critical crack opening displacement (the critical crack tip opening displacement and the critical crack mouth opening displacement) was studied. The result shows that the effect of ρf on mouth-tip ratio (the ratio of critical crack mouth opening displacement to critical crack tip opening displacement) can reflect its effect upon the critical crack opening displacement. According to the geometrical relationship between the initial crack length and the critical crack opening displacement，calculation method for the initial crack length was proposed. Based on the test result, the formula was established for calculating the critical crack tip opening displacement.

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.

A Fracture Mechanics Investigation on Crack Growth in Massive Forming

2005 ◽  
Vol 482 ◽  
pp. 339-342 ◽  
Author(s):  
Gernot Trattnig ◽  
Christof Sommitsch ◽  
Reinhard Pippan
Keyword(s):  
Crack Initiation ◽  
Crack Growth ◽  
Hydrostatic Stress ◽  
Crack Opening ◽  
Crack Depth ◽  
High Stress ◽  
Symmetry Plane ◽  
Stress Triaxiality ◽  
Opening Displacement ◽  
Massive Forming

To understand the crack growth in massive forming and to consequentially avoid crack growth in workpieces, it is necessary to investigate its dependence on the crack depth and thus on the state of hydrostatic stress. Prior work shows that the crack opening displacement (COD) for shallow cracked tension specimens with low stress triaxiality is twice as high as for deep cracked specimens with high stress triaxiality. This work examines the crack growth in compression specimens with pre-cracked cylindrical upsetting samples. The compression samples were cut in the stress symmetry plane in order to observe crack initiation and crack growth by a single specimen technique. In this way it is possible to observe blunting, crack initiation and crack growth inside the upsetting specimens. The resulting COD does not differ significantly from the values achieved in tension samples with short surface cracks.

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.

Crack-Tip Shielding in Metal-Matrix Composites: Modelling Of Crack Bridging by Uncracked Ligaments

1988 ◽  
Vol 120 ◽  
Author(s):  
Jian Ku Shang ◽  
R. O. Ritchie
Keyword(s):  
Metal Matrix Composites ◽  
Metal Matrix ◽  
Fatigue Cracks ◽  
Crack Opening ◽  
Crack Tip ◽  
Matrix Composites ◽  
Opening Displacement ◽  
Crack Bridging ◽  
Critical Crack ◽  
Crack Tip Shielding

AbstractAs part of an investigation into the micro-mechanisms of crack-tip shielding associated with the growth of fatigue cracks in metal-matrix composites, simple models are developed for the role of crack bridging in high-strength aluminum alloys reinforced with SiC particulate (AI/SiCp). Based on experimental observations of crack growth, crack-tip shielding and crack-path morphology in these alloys, the bridges are found to be associated with uncracked ligaments in the wake of the crack tip, and are modelled in terms of approaches based on a critical crack-opening displacement or critical tensile strain in the ligament.

Predictions of Creep Crack Initiation Periods in Pre-Compressed 316H Stainless Steel

2013 ◽  
Author(s):  
K. M. Tarnowski ◽  
C. M. Davies ◽  
G. A. Webster ◽  
D. W. Dean
Keyword(s):  
Stainless Steel ◽  
Crack Initiation ◽  
Crack Growth ◽  
Crack Opening ◽  
Creep Crack Growth ◽  
Prediction Methods ◽  
Opening Displacement ◽  
Crack Growth Behaviour ◽  
Creep Crack ◽  
Significant Difference

Pre-compression of 316H stainless steel significantly alters its tensile, uniaxial creep and crack growth behaviour. It has previously been shown that reliable and conservative creep crack initiation predictions can generally be obtained for as-received 316H stainless steel using a variety of prediction methods. Given the changes in material behaviour caused by pre-compression, this paper applies similar prediction methods to pre-compressed 316H stainless steel at 550°C. Several procedures are available for estimating creep crack initiation time periods. The suitability of a procedure depends on the availability of the necessary material data. The procedures considered in this paper include the use of the creep fracture mechanics parameter C*, the crack opening displacement concept, the sigma-d approach and the time dependent failure assessment diagram. Creep crack growth tests have been performed on compact tension specimens manufactured from 316H stainless steel which was uniformly pre-compressed by 4% and 8% at room temperature. For each test, the time for creep crack initiation to occur was recorded. Predicted creep crack initiation times have been compared with the experimentally determined values. Comparisons with as-received material are also included. For pre-compressed material, conservative creep crack initiation predictions were only consistently achieved using steady state creep crack growth rates predicted from C*. This is a significant difference to as-received material for which conservative predictions were generally obtained by a variety of methods. At this time, there is only a limited set of pre-compressed data making it difficult to draw firm conclusions about the appropriateness of the various creep crack initiation prediction methods. The differences in the results between the pre-compressed and as-received material do however highlight the need for further tests on pre-compressed material.

The Relationship Between Stress Intensity Factor, Crack Opening Displacement and J-Integral in Zr-2.5 Percent Nb

1980 ◽  
Vol 102 (1) ◽  
pp. 97-100 ◽  
Author(s):  
L. A. Simpson
Keyword(s):  
Stress Intensity ◽  
Crack Opening Displacement ◽  
Crack Extension ◽  
Crack Opening ◽  
J Integral ◽  
Opening Displacement ◽  
Crack Face ◽  
Critical Crack ◽  
Wide Range ◽  
The Relationship

Crack opening displacement (COD) has been determined in Zr-2.5 percent Nb over a wide range of applied stress intensity, K. Prior to initiation of crack extension, COD was determined from measurements of stretch zones in specimens which had undergone hydrogen-induced, sub-critical crack growth. In post initiation measurements (during slow stable crack extension), COD was determined from crack face displacement. Both methods were self consistent and depended on the plastic-zone-corrected K in accordance with the Wells equation. The J-integral was also determined during stable crack extension using the method of Garwood, et al. The results are consistent with the COD measurements based on theoretical relationships between the two crack tip parameters.

Fracture Mechanics Applied to Elevated Temperature Crack Growth

1989 ◽  
Vol 111 (3) ◽  
pp. 306-313 ◽  
Author(s):  
E. H. Jordan ◽  
G. J. Meyers
Keyword(s):  
Intensity Factor ◽  
Crack Growth ◽  
Crack Opening ◽  
J Integral ◽  
Strain Intensity ◽  
Opening Displacement ◽  
Hastelloy X ◽  
Test Conditions ◽  
Tubular Specimens ◽  
Temperature Crack

Twenty-six isothermal crack growth tests were performed on Hastelloy-X tubular specimens at a variety of temperatures and strain ranges. Conditions were selected to include nominally elastic and nominally plastic conditions. A number of parameters including the stress intensity factor, strain intensity factor, J-integral, Crack Opening Displacement, and Tompkins model were examined for their ability to correlate the data. Test conditions were selected such that growth rates at a single value of the parameter were obtained at radically different crack lengths, thus exploring the geometry independence of the correlating parameter. None of the parameters were fully satisfactory. However, COD calculated from J-integral appeared to be the most successful.

scholarly journals Fracture toughness and crack growth of brackish ice using chevron-notched specimens

1994 ◽  
Vol 40 (135) ◽  
pp. 415-426
Author(s):  
Lars Stehn
Keyword(s):  
Fracture Toughness ◽  
Crack Growth ◽  
Crack Opening ◽  
Initial Crack ◽  
Effect Study ◽  
Small Scale ◽  
Opening Displacement ◽  
Critical Crack ◽  
Experimental Calibration ◽  
Brackish Ice

AbstractField-test equipment called FIFT (a Field Instrument for Fracture toughness Tests on ice) was used in both field and laboratory fracture-toughness tests on brackish sea ice from the Gulf of Bothnia. An experimental calibration was performed and a compliance expression was then derived for the Short Rod Chevron Notched (SRCN) specimen. Using the SRCN configuration, for which the initial crack growth is shown to be stable, and measured load-point displacements, preliminary crack-growth velocities are found. The obtained estimated crack velocity is, on average,ȧe= 20 ms−1, albeit with a large standard deviation. The results indicate that critical crack (crack-jumping) growth occurs. The apparent fracture toughness,KQ, was found to have a pronounced dependency on porosity in the form of brine volume. The results obtained are derived from a linearly elastic fracture mechanics (LEFM) theory. Consequently, the tests were designed to satisfy small-scale yielding requirements in terms of notch sensitivity and brittleness. The linearity of the load vs crack-opening displacement curves together with a size-effect study, showing that the specimen is notch-sensitive for grain-sizes ranging from 1.6 to nearly 100 mm, indicate that LEFM could be applicable.

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