J-Integral Approach to Fracture of Rotating Disk

1978 ◽  
Vol 100 (2) ◽  
pp. 128-133 ◽  
Author(s):  
M. Sakata ◽  
S. Aoki ◽  
M. Kanzawa ◽  
N. Ogure ◽  
K. Tateishi
Keyword(s):  
Crack Growth ◽  
Fracture Criterion ◽  
Rotating Disk ◽  
Compact Tension ◽  
Nondestructive Inspection ◽  
Integral Approach ◽  
Plastic Behavior ◽  
J Integral ◽  
Rotating Disks ◽  
Tension Tests

The J-integral has been used as a fracture criterion for elastic-plastic behavior of metals. It may be pertinent to use the JIc concept for design or nondestructive inspection of rotating disks which have crack-like flaws and exhibit some amount of plastic behavior to fracture. JIc for cracked rotating disks of rotor forging steel is determined experimentally and is compared with that obtained using compact specimens. It is shown that prediction based on the compact tension tests agrees well with initiation of crack growth in rotating disks.

Crack Growth and Instable Fracture of Rotating Disks

1985 ◽  
Vol 107 (2) ◽  
pp. 154-160 ◽  
Author(s):  
M. Sakata ◽  
S. Aoki ◽  
K. Kishimoto ◽  
M. Kanzawa ◽  
N. Ogure
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Crack Growth ◽  
Fatigue Cracks ◽  
Instability Criterion ◽  
J Integral ◽  
Rotating Disks ◽  
Predicted Values ◽  
Bursting Speed ◽  
Good Agreement

The fracture of rotating disks that have cracks and/or notches is predicted employing the crack instability criterion based on the J-integral R-curve approach characterizing a material resistance to fracture. The J-integrals of cracked rotating disks are calculated by an elastic-plastic finite element method taking account of the thickness effects. Spin tests were carried out on disks having fatigue cracks and/or notches and the crack extensions as well as the bursting speeds of the disk specimens were measured. It is shown that the predicted values of bursting speed are in good agreement with those obtained by the experiment.

Specimen Curvature and Size Effects on Crack Growth Resistance From Compact Tension Specimens of CANDU Pressure Tubes

2019 ◽  
Author(s):  
Bruce W. Williams ◽  
William R. Tyson ◽  
C. Hari M. Simha ◽  
Bogdan Wasiluk
Keyword(s):  
Fracture Toughness ◽  
Crack Growth ◽  
Crack Extension ◽  
Compact Tension ◽  
Crack Growth Resistance ◽  
Pressure Tube ◽  
Small Scale ◽  
J Integral ◽  
Tube Material ◽  
Pressure Tubes

Abstract CSA Standard N285.8 requires leak-before-break and fracture protection for Zr-2.5Nb pressure tubes in operating CANDU reactors. In-service deuterium uptake causes the formation of hydrides, which can result in additional variability and reduction of fracture toughness. Pressure tube fracture toughness is assessed mainly through rising pressure tube section burst tests. Given the length of the ex-service pressure tubes required for burst testing and the requirement to increase the hydrogen content of irradiated ex-service pressure tubes, only a limited number of burst tests can be performed. Using small-scale compact tension, C(T), specimens are advantageous for obtaining a statistically significant number of fracture toughness measurements while using less ex-service pressure tube material. This work focuses on the study of C(T) geometry designs in order to obtain crack growth resistance and fracture toughness closer to those deduced from burst tests. Because C(T) specimens must be machined from pressure tubes of about 100 mm in diameter and 4 mm in wall thickness, they are out-of-plane curved. As well, they undergo significant tunnelling during crack extension. These two factors can result in a violation of the ASTM standard for fracture toughness testing. The current work examined the influence of specimen curvature and tunnelled crack front on the crack growth resistance curve, or J-R curve. Finite element (FE) models using stationary and growing cracks were used in a detailed numerical investigation. To capture crack tunnelling in the FE models, a damage mechanics approach was adopted, with the critical strain to accumulate damage being a function of crack front stress triaxiality. The J-integral numerically estimated from the domain integral approach was compared to the J-integral calculated from the analytical equations in the ASTM E-1820 standard. In most cases, the difference between the numerical and the standard estimations was less than 10%, which was considered acceptable. It was found that at higher load levels of load-line-displacement, specimen curvature influenced the J-integral results. Crack tunnelling was shown to have a small influence on the estimated J-integrals, in comparison with the straight crack fronts. A modest number of experiments were carried out on unirradiated Zr-2.5Nb pressure tube material using three designs of curved C(T) specimens. It was found that the specimens of both designs that featured a width of 34 mm had more than twice the crack extension of the specimens of the 17-mm width design. The 17-mm width specimens are used mainly to assess the small-scale fracture toughness of pressure tube material. Additionally, the applied J-integral at the maximum load was about 1.4 times higher for the larger-width C(T) specimens. These C(T) specimens also produced J-R curves with greater crack extensions, which were closer to those obtained from the pressure tube section burst tests. Artificially hydrided pressure tube material was not considered in the current work, to avoid any potential source of experimental variability; however, it should be considered in future work.

Non-Linear Fatigue Fracture Analysis of Composite Laminates

2009 ◽  
Vol 17 (6) ◽  
pp. 371-377 ◽  
Author(s):  
V. Rizov
Keyword(s):  
Crack Growth ◽  
Fatigue Fracture ◽  
Composite Laminates ◽  
Compact Tension ◽  
Compact Tension Specimen ◽  
Damage Analysis ◽  
J Integral ◽  
Tension Specimen ◽  
Linear Deformation ◽  
Non Linear

In this paper, results of an experimental and numerical investigation of the effects of non-linear deformation on the fatigue crack growth in composite laminates are presented and discussed. Mode I fatigue fracture experiments are carried out on extended compact tension specimens under sinusoidal load control at a frequency of 4 Hz. The fatigue fracture test data are analysed using a power law relationship between the crack growth rates and the range of the path-independent J-integral. A two- dimensional finite element model of the extended compact tension specimen is set up in order to compute the J-integral values. The model is coupled with damage analysis in order to study the effect of non-linear deformation on the fatigue fracture performance. The damage analysis is based on the Tsai-Wu failure criterion. The non-linear model is verified by carrying out comparisons between the simulated mechanical behaviour of the extended compact tension specimen and the measured one. The damage distribution within the specimen is analyzed. The J-integral is computed over paths surrounding the crack tip and not crossing the damage zone. It is shown that taking into account the damage behaviour improves the fatigue fracture resistance, which is attributed to increased strain energy dissipation as a result of non-linear deformation.

The Determination of the J-Integral on Precracked Charpy Specimens by Instrumented Impact Testing and Slow-Bend Testing

1978 ◽  
Vol 100 (3) ◽  
pp. 253-257 ◽  
Author(s):  
P. Nguyen-Duy ◽  
G. Phelippeau ◽  
R. Simoneau ◽  
G. Begin
Keyword(s):  
Fracture Criterion ◽  
Impact Testing ◽  
Plastic Behavior ◽  
Displacement Curve ◽  
Maximum Point ◽  
J Integral ◽  
Lateral Deformation ◽  
Absorbed Energy ◽  
Point Bend

The fracture criterion JIC is determined on SA-516-70 steel using precracked CVN specimens. The addition of an appropriate side-groove results in a better plane-strain condition at the crack tip and removes a major part of the absorbed energy due to lateral deformation. The value of JIC static is calculated from a single three-point-bend experiment. The displacement of the cracked front is followed by the measurement of the electrical resistance. We have shown that a single specimen is sufficient for determining JIC. Experiments on an instrumented Charpy machine were used for the calculation of the value of JICD. We assumed, for elasto-plastic behavior, that the maximum point of the load-displacement curve corresponds to the instability threshold of the crack. The values of JIC and JICD obtained by these two methods are compared and discussed.

Prediction of crack growth initiation in paper structures using a J-integral criterion

2000 ◽  
Vol 15 (1) ◽  
pp. 4-11 ◽  
Author(s):  
Pär Wellmar ◽  
Øyvind Weiby Gregersen ◽  
Christer Fellers
Keyword(s):  
Crack Growth ◽  
J Integral ◽  
Integral Criterion ◽  
Growth Initiation

scholarly journals Comparison of Modified Mohr–Coulomb Model and Bai–Wierzbicki Model for Constructing 3D Ductile Fracture Envelope of AA6063

2021 ◽  
Vol 34 (1) ◽  
Author(s):  
Jianye Gao ◽  
Tao He ◽  
Yuanming Huo ◽  
Miao Song ◽  
Tingting Yao ◽  
...  
Keyword(s):  
Ductile Fracture ◽  
Fracture Criterion ◽  
Fracture Strain ◽  
Stress Triaxiality ◽  
Ductile Fracture Criterion ◽  
Forming Process ◽  
Tension Tests ◽  
Wide Range ◽  
Round Bar ◽  
Fracture Envelope

AbstractDuctile fracture of metal often occurs in the plastic forming process of parts. The establishment of ductile fracture criterion can effectively guide the selection of process parameters and avoid ductile fracture of parts during machining. The 3D ductile fracture envelope of AA6063-T6 was developed to predict and prevent its fracture. Smooth round bar tension tests were performed to characterize the flow stress, and a series of experiments were conducted to characterize the ductile fracture firstly, such as notched round bar tension tests, compression tests and torsion tests. These tests cover a wide range of stress triaxiality (ST) and Lode parameter (LP) to calibrate the ductile fracture criterion. Plasticity modeling was performed, and the predicted results were compared with corresponding experimental data to verify the plasticity model after these experiments. Then the relationship between ductile fracture strain and ST with LP was constructed using the modified Mohr–Coulomb (MMC) model and Bai-Wierzbicki (BW) model to develop the 3D ductile fracture envelope. Finally, two ductile damage models were proposed based on the 3D fracture envelope of AA6063. Through the comparison of the two models, it was found that BW model had better fitting effect, and the sum of squares of residual error of BW model was 0.9901. The two models had relatively large errors in predicting the fracture strain of SRB tensile test and torsion test, but both of the predicting error of both two models were within the acceptable range of 15%. In the process of finite element simulation, the evolution process of ductile fracture can be well simulated by the two models. However, BW model can predict the location of fracture more accurately than MMC model.

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