Steady-State Crack Propagation in Pressurized Pipelines Without Backfill

1976 ◽  
Vol 98 (1) ◽  
pp. 56-64 ◽  
Author(s):  
M. F. Kanninen ◽  
S. G. Sampath ◽  
C. Popelar
Keyword(s):  
Steady State ◽  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Crack Arrest ◽  
State Dynamic ◽  
Plastic Yield ◽  
Scale Experiment ◽  
Pressurized Pipelines ◽  
Dynamic Energy Release Rate

In a previous paper, a simplified dynamic-shell theory representation was formulated for steady-state motion in a pipeline without backfill. The present work extends this model by (1) incorporating a gas dynamics treatment to determine the axial variation in the pressure exerted by the gas on the pipe walls, and (2) incorporating a plastic yield hinge behind the crack tip. Solutions to the governing dynamic equations are obtained for these conditions and used to calculate the steady-state dynamic energy release rate as a function of crack speed. In the single full-scale experiment in which an independent estimate of the dynamic fracture energy is available for a pipe without backfill, the model predicts a steady-state speed of 780 fps. This can be compared with measured speeds which ranged from 725 to 830 fps in the test. Because the calculated steady-state dynamic energy release rate exhibits a maximum, it is suggested that this approach may offer a basis for crack arrest design of pipelines.

The Dynamic Energy Release Rate for a Steadily Propagating Antiplane Shear Crack in a Linearly Viscoelastic Body

1987 ◽  
Vol 54 (3) ◽  
pp. 635-641 ◽  
Author(s):  
J. R. Walton
Keyword(s):  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Shear Crack ◽  
Viscoelastic Body ◽  
Antiplane Shear ◽  
Singular Stress ◽  
Crack Face ◽  
Standard Linear Solid ◽  
Dynamic Energy Release Rate

The steady-state propagation of a semi-infinite, antiplane shear crack is reconsidered for a general, infinite, homogeneous and isotropic linearly viscoelastic body. As with an earlier study, the inertial term in the equation of motion is retained and the shear modulus is only assumed to be positive, continuous, decreasing, and convex. A Barenblatt type failure zone is introduced in order to cancel the singular stress, and a numerically convenient expression for the dynamic Energy Release Rate (ERR) is derived for a rather general class of crack face loadings. The ERR is shown to have a complicated dependence on crack speed and material properties with significant qualitative differences between viscoelastic and elastic material. The results are illustrated with numerical calculations for both power-law material and a standard linear solid.

Steady-State Crack Propagation in Pressurized Pipelines

1977 ◽  
Vol 99 (1) ◽  
pp. 112-121 ◽  
Author(s):  
C. Popelar ◽  
A. R. Rosenfield ◽  
M. F. Kanninen
Keyword(s):  
Steady State ◽  
Crack Propagation ◽  
Driving Force ◽  
Crack Arrest ◽  
Operating Conditions ◽  
Unstable Crack ◽  
Crack Driving Force ◽  
Plastic Yield ◽  
Pressurized Pipelines ◽  
Full Scale Tests

Previous work at Battelle-Columbus on the development of a theoretical model for unstable crack propagation and crack arrest in a pressurized pipeline is extended in this paper by including the effect of backfill. The approach being developed involves four essential aspects of crack propagation in pipelines. These four components of the problem are: 1 – a shell theory characterization of the dynamic deformation of a pipe with a plastic yield-hinge behind an axially propagating crack, 2 – a fluid-mechanics treatment of the axial variations in the gas pressure acting on the pipe walls, 3 – an energy-based dynamic fracture mechanics formulation for the crack-driving force, and 4 – measured values of the dynamic energy absorption rate for pipeline steels. Comparisons given in the paper show that the steady-state crack speeds predicted by the model are in reasonably good agreement with the crack speeds measured in full-scale tests, both with and without backfill. The analysis further reveals the existence of a maximum steady-state crack-driving force as a function of the basic mechanical properties of the pipe steel and the pipeline goemetry and operating conditions. Quantitative estimates of this quantity provided by the model offer a basis for comparison with the empirical crack-arrest design criteria for pipelines developed by AISI, the American Gas Association, the British Gas Council, and British Steel. These are also shown to be in substantial agreement with the predictions of the model developed in this paper.

On The Response Of Dynamic Cracks To Increasing Overload

1995 ◽  
Vol 409 ◽  
Author(s):  
P. Gumbsch
Keyword(s):  
Steady State ◽  
Crack Propagation ◽  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Mechanical Energy ◽  
Terminal Velocity ◽  
Brittle Crack ◽  
Dislocation Generation ◽  
Stable Crack Propagation

AbstractOne of the most interesting questions in the dynamics of brittle fracture is how a running brittle crack responds to an overload, i.e. to a mechanical energy release rate larger than that due to the increase in surface energy of the two cleavage surfaces. To address this question, dynamically running cracks in different crystal lattices are modelled atomistically under the condition of constant energy release rate. Stable crack propagation as well as the onset of crack tip instabilities are studied.It will be shown that small overloads lead to stable crack propagation with steady state velocities which quickly reach the terminal velocity of about 0.4 of the Rayleigh wave speed upon increasing the overload. Further increasing the overload does not change the steady state velocity but significantly changes the energy dissipation process towards shock wave emission at the breaking of every single atomic bond. Eventually the perfectly brittle crack becomes unstable, which then leads to dislocation generation and to the production of cleavage steps. The onset of the instability as well as the terminal velocity are related to the non-linearity of the interatomic interaction.

The Dynamic Energy Release Rate for a Steadily Propagating Mode I Crack in an Infinite, Linearly Viscoelastic Body

1990 ◽  
Vol 57 (2) ◽  
pp. 343-353 ◽  
Author(s):  
J. R. Walton
Keyword(s):  
Steady State ◽  
Crack Propagation ◽  
Energy Release Rate ◽  
Energy Release ◽  
Release Rate ◽  
Viscoelastic Body ◽  
Mode I ◽  
Mode I Crack ◽  
Failure Zone ◽  
Special Cases

An analysis is presented for the dynamic, steady-state propagation of a semi-infinite, mode I crack in an infinite, linearly viscoelastic body. For mathematical convenience, the material is assumed to have a constant Poisson’s ratio, but the shear modulus is only assumed to be decreasing and convex. An expression for the Stress Intensity Factor (SIF) is derived for very general tractions on the crack faces and the Energy Release Rate (ERR) is constructed assuming that a fully developed Barenblatt type failure zone with nonsingular stresses exists at the crack tip and the loadings have a simple exponential form. For comparative purposes, expressions for the ERR are derived for the special cases of dynamic steady-state crack propagation in elastic material and quasi-static crack propagation in viscoelastic material, both with and without a failure zone. Sample calculations are included for power-law material and a standard linear solid in order to illustrate the combined influence of inertial effects, material viscoelasticity, and a failure zone upon the ERR.

Evaluation of the modified edge lift-off test for adhesion characterization in microelectronic multifilm applications

2001 ◽  
Vol 16 (2) ◽  
pp. 385-393 ◽  
Author(s):  
Jack C. Hay ◽  
Eric G. Liniger ◽  
Xiao Hu Liu
Keyword(s):  
Steady State ◽  
Film Thickness ◽  
Energy Release Rate ◽  
Crack Length ◽  
Energy Release ◽  
Release Rate ◽  
Crack Problem ◽  
Young’S Moduli ◽  
Lift Off ◽  
Unexpected Outcomes

The modified edge lift-off test (MELT) has gained enough acceptance in the community for evaluating interfacial adhesion that there is now commercial equipment for automating the test. However, there are several experimental and mechanics assumptions of the test that may provide unexpected outcomes. Experimental data suggested that for crack lengths greater than 5% of the film thickness the energy release rate was independent of crack length, contradicting the rule of thumb suggesting that the crack length should be greater than 10–20 times the film thickness to obtain a steady-state energy release rate in the edge crack problem. Finite element simulations not only corroborated the experimental observation but seemed to indicate that the crack length required for steady-state conditions was a function of the relative Young's moduli for the film and substrate. It was also shown via an analytical model that plate bending (commonly neglected) can significantly affect the energy release rate in the MELT and lead to incorrect conclusions regarding the reliability of an interface.

Sign in / Sign up

Export Citation Format

Share Document