scholarly journals The effect of buffer-layer on the steady-state energy release rate of a tunneling crack in a wind turbine blade joint

2018 ◽  
Vol 188 ◽  
pp. 64-71 ◽  
Author(s):  
Jeppe B. Jørgensen ◽  
Bent F. Sørensen ◽  
Casper Kildegaard
Keyword(s):  
Steady State ◽  
Energy Release Rate ◽  
Wind Turbine ◽  
Energy Release ◽  
Buffer Layer ◽  
Turbine Blade ◽  
Release Rate ◽  
State Energy ◽  
Wind Turbine Blade

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.

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.

Calculating Energy Release Rate as a Function of Crack Length Using a Multiple-Step Crack Closure Technique in Tire Finite Element Models

2018 ◽  
Vol 46 (3) ◽  
pp. 130-152
Author(s):  
Dennis S. Kelliher
Keyword(s):  
Finite Element ◽  
Energy Release Rate ◽  
Crack Length ◽  
Energy Release ◽  
Crack Closure ◽  
Release Rate ◽  
Fatigue Behavior ◽  
Three Dimensions ◽  
Quantitative Prediction ◽  
Closure Technique

ABSTRACT When performing predictive durability analyses on tires using finite element methods, it is generally recognized that energy release rate (ERR) is the best measure by which to characterize the fatigue behavior of rubber. By addressing actual cracks in a simulation geometry, ERR provides a more appropriate durability criterion than the strain energy density (SED) of geometries without cracks. If determined as a function of crack length and loading history, and augmented with material crack growth properties, ERR allows for a quantitative prediction of fatigue life. Complications arise, however, from extra steps required to implement the calculation of ERR within the analysis process. This article presents an overview and some details of a method to perform such analyses. The method involves a preprocessing step that automates the creation of a ribbon crack within an axisymmetric-geometry finite element model at a predetermined location. After inflating and expanding to three dimensions to fully load the tire against a surface, full ribbon sections of the crack are then incrementally closed through multiple solution steps, finally achieving complete closure. A postprocessing step is developed to determine ERR as a function of crack length from this enforced crack closure technique. This includes an innovative approach to calculating ERR as the crack length approaches zero.

Sign in / Sign up

Export Citation Format

Share Document