A Sensitivity Study on Numerical Analysis of Dynamic Girth Crack Propagation

1981 ◽  
Vol 103 (2) ◽  
pp. 169-174 ◽  
Author(s):  
A. S. Kobayashi ◽  
A. F. Emery ◽  
W. J. Love ◽  
A. Jain
Keyword(s):  
Crack Propagation ◽  
Large Scale ◽  
Sensitivity Study ◽  
Initial Crack ◽  
Dynamic Crack Propagation ◽  
Opening Angle ◽  
Dynamic Crack ◽  
Critical Crack ◽  
Scale Yielding ◽  
Crack Tip Opening

Dynamic motion of pre-existing girth crack in an axially stressed, 18-in-dia 316 stainless steel pipe in the presence of large-scale yielding was analyzed by a finite difference shell code. A critical crack tip opening angle (CTOA) was used as a dynamic fracture criterion and the sensitivities of dynamic crack propagation to differences in CTOA, finite differences mesh sizes, initial crack sizes and initial crack bluntnesses, were analyzed numerically. Hold-off times for the onset of dynamic crack propagation nearly doubled and tripled, while terminal crack velocities decreased about 22 percent and 47percent when the CTOA was increased from 0.10 to 0.19 and to 0.30, respectively. Doubling of the axial length of the initial crack length and an overdriving condition simulated by a larger CTOA did not change the terminal crack velocity.

Molecular-Dynamics Simulations Of Fracture: An Overview Of System Size And Other Effects

1995 ◽  
Vol 409 ◽  
Author(s):  
B. L. Holian ◽  
S.J. Zhou ◽  
P.S. Lomdahl ◽  
N. Gronbech-Jensen ◽  
D.M. Beazley ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Crack Propagation ◽  
Large Scale ◽  
Initial Conditions ◽  
Three Dimensional ◽  
Crack Tip ◽  
System Size ◽  
Dynamic Crack Propagation ◽  
Dynamic Crack ◽  
Dislocation Loops

AbstractWe have studied brittle and ductile behavior and their dependence on system size and interaction potentials, using molecular-dynamics (MD) simulations. By carefully embedding a single sharp crack in two- and three-dimensional crystals, and using a variant of the efficient sound-absorbing reservoir of Holian and Ravelo [Phys. Rev. B 51, 11275 (1995)], we have been able to probe both the static and dynamic crack regimes. Our treatment of boundary and initial conditions allows us to elucidate early crack propagation mechanisms under delicate overloading, all the way up to the more extreme dynamic crack-propagation regime, for much longer times than has been possible heretofore (before unwanted boundary effects predominate). For example, we have used graphical display of atomic velocities, forces, and potential energies to expose the presence of localized phonon-like modes near the moving crack tip, just prior to dislocation emission and crack-branching events. We find that our careful MD method is able to reproduce the ZCT brittle-ductile criterion for short-range pair potentials [static lattice Green's function calculations of Zhou, Carlsson, and Thomson, Phys. Rev. Letters 72, 852 (1994)].We report on progress we have made in large-scale 3D simulations in samples that are thick enough to display realistic behavior at the crack tip, including emission of dislocation loops. Such. calculations, using our careful treatment of boundary and initial conditions - especially important in 3D - have the promise of opening up new vistas in fracture research.

Predicting Crack Velocity and Fracture Arrest Pressure From Simulations of Dynamic Pipe Rupture

2019 ◽  
Author(s):  
Bruce W. Williams ◽  
Su Xu ◽  
William R. Tyson
Keyword(s):  
Crack Propagation ◽  
Crack Front ◽  
Crack Velocity ◽  
Pressure Profile ◽  
Gas Pressure ◽  
Dynamic Crack Propagation ◽  
Opening Angle ◽  
Dynamic Crack ◽  
Pipe Steels ◽  
Soil Pressure

Abstract During a gas pipeline rupture event, the crack propagation velocity can exceed 300 m/s and the crack can run for several hundreds of metres before arresting. The current model to predict arrest pressure is the Battelle Two Curve Method (BTCM) using the Charpy V-notch energy to characterize propagation toughness. It has been shown that this model can give non-conservative predictions for high-strength pipe steels. Hence, the Crack Tip Opening Angle (CTOA) has been introduced as a promising parameter to describe crack propagation. The objective of the current work was to study the crack propagation process in pipe by Finite Element Analysis (FEA) techniques to gain a better understanding of crack driving force and factors influencing CTOA. Implicit FEM simulations of dynamic crack propagation in pipes with diameters ranging from 355 mm to 1219 mm with a wall thickness of about 19 mm were performed using material properties representative of either X65 or X80 pipeline steel. The specification of a critical CTOA and the nodal release algorithm in the software WARP3D were employed to propagate the crack up to about two metres in the simulations. For a given critical CTOA, pipe diameter, and pipe thickness a set of simulations was performed where the initial applied gas pressure varied from as low as 4 MPa up to 60 MPa (which corresponds to about 80% of the yield strength of the material). The CTOA values used in the simulations ranged from 5° to 20° and corresponded to CTOA measurements obtained in concurrent work from Drop Weight Tear Tests performed on pipe steels. To accurately predict crack velocity, it was important to apply a flap loading profile near the crack front representative of the gas pressure response during pipe rupture. Comparison of the crack propagation response was carried out between a constant pressure profile just behind the crack front and a pressure profile that varied with circumference a round the pipe. The influence of soil pressure on the flap loading response was also considered in the models. The predicted pressure versus crack velocity profiles and the arrest pressure can then be subsequently used to predict the arrest length for a given CTOA.

Dynamic crack propagation in matrix involving inclusions by a time-domain BEM

2012 ◽  
Vol 36 (5) ◽  
pp. 651-657 ◽  
Author(s):  
Jun Lei ◽  
Yue-Sheng Wang ◽  
Yifeng Huang ◽  
Qingsheng Yang ◽  
Chuanzeng Zhang
Keyword(s):  
Crack Propagation ◽  
Time Domain ◽  
Dynamic Crack Propagation ◽  
Dynamic Crack

Dynamic Crack Propagation in Single-Crystalline Silicon

1998 ◽  
Vol 539 ◽  
Author(s):  
T. Cramer ◽  
A. Wanner ◽  
P. Gumbsch
Keyword(s):  
Crack Propagation ◽  
Crystalline Silicon ◽  
Potential Drop ◽  
Tensile Tests ◽  
Terminal Velocity ◽  
Dynamic Crack Propagation ◽  
Dynamic Crack ◽  
Single Crystalline Silicon ◽  
Single Crystalline ◽  
Crack Propagation Velocity

AbstractTensile tests on notched plates of single-crystalline silicon were carried out at high overloads. Cracks were forced to propagate on {110} planes in a <110> direction. The dynamics of the fracture process was measured using the potential drop technique and correlated with the fracture surface morphology. Crack propagation velocity did not exceed a terminal velocity of v = 3800 m/s, which corresponds to 83%7 of the Rayleigh wave velocity vR. Specimens fractured at low stresses exhibited crystallographic cleavage whereas a transition from mirror-like smooth regions to rougher hackle zones was observed in case of the specimens fractured at high stresses. Inspection of the mirror zone at high magnification revealed a deviation of the {110} plane onto {111} crystallographic facets.

scholarly journals Dynamic crack propagation in a 2D elastic body. The out-of plane case

PAMM ◽  
2007 ◽  
Vol 7 (1) ◽  
pp. 1090801-1090802
Author(s):  
A.-M. Sändig ◽  
A. Lalegname ◽  
S. Nicaise
Keyword(s):  
Crack Propagation ◽  
Elastic Body ◽  
Dynamic Crack Propagation ◽  
Dynamic Crack ◽  
Plane Case ◽  
Out Of Plane

Dynamic Crack Propagation and Arrest in PWR Pressure Vessel Steel: Interpretation of Experiment With the X-FEM Method

2007 ◽  
Author(s):  
B. Prabel ◽  
S. Marie ◽  
A. Combescure
Keyword(s):  
Finite Element ◽  
Crack Propagation ◽  
Strain Rate ◽  
Thermal Shock ◽  
Crack Growth ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Crack Propagation ◽  
Dynamic Crack ◽  
Pressure Vessel Steel ◽  
Vessel Steel

In the frame of analysis of the pressure thermal shock in a PWR RVP and the associated R&D activities, some developments are performed at CEA on the dynamic brittle propagation and crack arrest. This paper presents a PhD work on the modeling of the dynamic brittle crack growth. For the analyses, an important experimental work is performed on different geometries using a French RPV ferritic steel: Compact Tension specimens with different thickness, isothermal rings under compression with different positions of the initial defect to study a mixed mode configuration, and a ring submitted to thermal shock. The first part of this paper details the test conditions and main results. To propose an accurate interpretation of the crack growth, a viscous-elastic-plastic dynamic model is used. The strain rate influence is taken into account based on Cowper-Symond’s law (characterization was made from Split Hopkinson Pressure Bar tests). To model the crack propagation in the Finite Element calculation, eXtended Finite Element Method (X-FEM) is used. The implementation of these specific elements in the CEA F.E. software CAST3M is described in the second part of this paper. This numerical technique avoids re-meshing, because the crack progress is directly incorporated in the degrees of freedom of the elements crossed by the crack. The last part of this paper compares the F.E. predictions to the experimental measurements using different criteria. In particular, we focused on a RKR (Ritchie-Knott-Rice) like criterion using a critical principal stress in the front of the crack tip during the dynamic crack extension. Critical stress is found to depend on crack speed, or equivalently on strain rate. Good results are reported concerning predictive simulations.

Sign in / Sign up

Export Citation Format

Share Document