Theoretical Research on the Dynamic Crack Propagation Velocity Based on Nonlocal Field Theories

2009 ◽  
Vol 417-418 ◽  
pp. 953-956
Author(s):  
Cai Ping Liu ◽  
Qing Quan Duan ◽  
Jian Ping Zuo
Keyword(s):  
Crack Propagation ◽  
Dynamic Fracture ◽  
Propagation Velocity ◽  
Characteristic Length ◽  
Theoretical Research ◽  
Field Theories ◽  
Dynamic Crack Propagation ◽  
Dynamic Crack ◽  
Crack Propagation Velocity ◽  
Nonlocal Field

The purpose of this paper is to discuss the nonlocal effect on dynamic crack propagation velocity. Some experimental phenomena in dynamic fracture and simulative results using molecular & atom dynamics were analyzed and discussed in this paper. The authors found that there were still some disagreements on the dynamic crack propagation velocity. Based on these researches, we introduced nonlocal field theories into the estimation of dynamic crack propagation velocity. The dynamic crack propagation velocity is affected not only by the crack instability, but by characteristic length of material. A nonlocal characteristic length parameter M is defined through a double pile-up dislocation model. According to the Mott’s research method for crack velocity in dynamic fracture and the nonlocal field theories, an approximate theoretical dynamic propagation velocity is obtained. And we conclude that the velocity is related to the combined activity of the nonlocal characteristic length parameter M, the velocity of longitudinal wave, constant k, crack length and Poisson’s ratio.

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 Study on Crack Propagation of the Tunnel Model under Dynamic Loading

2021 ◽  
Vol 2021 ◽  
pp. 1-18
Author(s):  
Chengxiao Li ◽  
Yuantong Zhang ◽  
Peng Xu ◽  
Chen An
Keyword(s):  
Fracture Toughness ◽  
Crack Propagation ◽  
Dynamic Fracture ◽  
Propagation Velocity ◽  
Fracture Process ◽  
Test Results ◽  
Crack Propagation Velocity ◽  
Propagation Law ◽  
Initial Fracture ◽  
The Impact

Crack defects make it difficult to predict the dynamic fracture of tunnel specimens under an impact load. To study the impact of the velocity and crack location on a roadway under dynamic load, specimens with tunnel-type voids were made using polymethyl methacrylate. The split-Hopkinson bar was used as the loading method, and a digital laser dynamic caustics system was used to observe the fracture process of the specimens. The dynamic fracture process was evaluated by the crack propagation velocity, displacement, and dynamic stress intensity factor. To predict and verify the test results, ABAQUS was used to simulate the test process. It was found that the results of the simulated combinations of the crack propagation path and initial fracture toughness change law are consistent with the test results. The initial fracture toughness and the peak value of the crack propagation velocity increased with the increase of the impact velocity. The crack propagation law and trajectory were affected by the location of the prefabricated cracks.

scholarly journals Dynamic Fracture Analysis of Functional Gradient Material Coating Based on the Peridynamic Method

Coatings ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 62 ◽  
Author(s):  
Yu Zhang ◽  
Zhanqi Cheng ◽  
Hu Feng
Keyword(s):  
Elastic Modulus ◽  
Crack Propagation ◽  
Dynamic Fracture ◽  
Gradient Material ◽  
Dynamic Crack Propagation ◽  
Dynamic Crack ◽  
Functional Gradient ◽  
Damage And Failure ◽  
Functional Gradient Material ◽  
Graded Material

Functional gradient materials (FGMs) have tremendous potential due to their characteristic advantage of asymptotic continuous variation of their properties. When an FGM is used as a coating material, damage and failure of the interface with the substrate component can be effectively inhibited. In order to study the dynamic crack propagation in FGM coatings, a new method, peridynamics (PD), was used in the present study to simulate dynamic fractures of FGM coatings bonded to a homogeneous substrate under dynamic loading. The bond-based PD theory was employed to study crack propagation and branching in the FGM coating. The influences of the coating gradient pattern, loading, and the geometry and size of the structure on crack curving and propagation under impact loading were investigated. The numerical results show that different forms of the elastic modulus of graded material, the geometry of the structure, and the loading conditions have considerate effects on crack propagation in FGM coatings, but a specific form of elastic modulus had a limited effect on the dynamic fracture of FGM coating.

scholarly journals Relationship Between Apparent (Total) Charpy Vee-Notch Toughness and the Corresponding Dynamic Crack-Propagation Resistance

1998 ◽  
Author(s):  
Brian N. Leis ◽  
Robert J. Eiber ◽  
L. Carlson ◽  
A. Gilroy-Scott
Keyword(s):  
Crack Propagation ◽  
Ductile Fracture ◽  
Dynamic Fracture ◽  
Empirical Models ◽  
Full Scale ◽  
Dynamic Crack Propagation ◽  
Dynamic Crack ◽  
Propagation Resistance ◽  
Crack Propagation Resistance ◽  
Arrest Toughness

The consequences of a dynamic fracture in a gas-transmission pipeline require that pipelines be designed to avoid such incidents at a high level of certainty. For this reason, the related phenomonology has been studied since the early 1970s when the possibility of a dynamic ductile fracture was recognized. Full-scale experiments were done to characterize the fracture and gas dynamics associated with this process and empirical models were developed as a means to represent these experiments in a design or analysis setting. Such experiments focused on pure methane gas, and in the early days used steels with toughnesses less than 100 J, consistent with the steel making capabilities of the 1970s. Subsequently, interest shifted to larger diameter, higher pressure, higher BTU “rich” gases requiring higher toughness steels. The full-scale tests conducted to validate the arrest toughness levels determined that these empirical models were non-conservative. This paper presents a relationship between the dynamic crack propagation resistance and the apparent crack propagation resistance as measured by Charpy vee-notch (CVN) test specimens. This relationship is used in conjunction with the existing Battelle empirical criterion for dynamic-fracture arrest to determine the apparent toughness required to arrest a propagating ductile fracture in gas-transmission pipelines. The validity of this relationship is illustrated by successful predictions of arrest toughness in pipelines under a range of conditions including rich gases and high-toughness steels, including those showing a rising upper-shelf behavior.

Analytical Modeling of Dynamic Crack Propagation in DCB Specimens

2009 ◽  
Author(s):  
Amir Reza Shahani ◽  
Mohammad Reza Amini Fasakhodi
Keyword(s):  
Crack Propagation ◽  
Shear Deformation ◽  
Crack Growth ◽  
Crack Tip ◽  
Dynamic Crack Propagation ◽  
Velocity Versus ◽  
Beam Specimen ◽  
Dynamic Crack ◽  
Static Case ◽  
Crack Propagation Velocity

An analytical solution via the beam theory considering shear deformation effects is developed to solve the static and dynamic fracture problem in a bounded medium such as DCB (Double Cantilever Beam) specimen. In the static case, the stress intensity factor (SIF) is derived at the crack tip through the compliance approach for fixed displacement conditions. In the dynamic case, the energy balance criterion is employed to obtain the equation of motion for a running crack and the problem is solved supposing quasi-static crack propagation. Finally, a closed form relation for the crack propagation velocity versus specimen parameters and crack growth resistance of the material is found. Therefore, the effects of various parameters are investigated on the crack growth velocity. It is shown that the reacceleration of crack growth appears when the crack tip approaches the end of specimen under fixed displacement loading. The predicted results are compared with those cited in the literature and a good agreement is observed. It is seen that shear deformation effects are more significant when the small values of a0/h is considered in the analysis.

scholarly journals Rock Dynamic Crack Propagation under Different Loading Rates Using Improved Single Cleavage Semi-Circle Specimen

2019 ◽  
Vol 9 (22) ◽  
pp. 4944
Author(s):  
Fei Wang ◽  
Meng Wang ◽  
Mohaddeseh Mousavi Nezhad ◽  
Hao Qiu ◽  
Peng Ying ◽  
...  
Keyword(s):  
Crack Propagation ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Stress Intensity Factor ◽  
Crack Arrest ◽  
Dynamic Crack Propagation ◽  
Dynamic Crack ◽  
Hopkinson Pressure Bar ◽  
Tight Sandstone ◽  
Crack Propagation Velocity ◽  
Loading Rates

The objective of this paper is to investigate the complete process of dynamic crack propagation in brittle materials under different loading rates. By using Improved Single Cleavage Semi-Circle (ISCSC) specimens and Split Hopkinson Pressure Bar equipment, experiments were conducted, with the fracture phenomenon and crack propagation of tight sandstone investigated. Meanwhile, the process of crack propagation behaviour was simulated. Moreover, with the experimental–numerical method, the crack propagation dynamic stress intensity factor (DSIF) was also calculated. Then, the crack propagation toughness of tight sandstone under different loading rates was investigated and illustrated elaborately. Investigation results demonstrate that ISCSC specimens can achieve the crack arrest position unchanged, and the numerical simulation could effectively deduce the actual crack propagation, as their results were well matched. During crack propagation, the crack propagation DSIF in the whole process increases with the rising loading rate, and so does the crack propagation velocity. Several significant dynamic material parameters of tight sandstone are also given, for engineering reference.

scholarly journals Uncovering the dynamic fracture behavior of PMMA

2019 ◽  
Author(s):  
Javad Mehrmashhadi ◽  
Longzhen Wang ◽  
Florin Bobaru
Keyword(s):  
Crack Propagation ◽  
Dynamic Fracture ◽  
Fracture Behavior ◽  
Numerical Models ◽  
Process Zone ◽  
Crack Tip ◽  
Dynamic Crack Propagation ◽  
Experimental Investigations ◽  
Dynamic Crack ◽  
Strain Rates

Experimental investigations of dynamic crack propagation in PMMA induced by impact show single cracks running at around 300-400 m/s. Existing numerical models for simulating dynamic fracture in PMMA consistently produce crack propagation speeds significantly higher than those measured experimentally. Here we uncover the reason for this puzzle by showing that localized softening in the fracture process zone (caused by heating due to high strain rates in front of the crack tip), leads to crack propagation speeds that match the observed ones. We introduce a new constitutive model in our peridynamic formulation for PMMA to account for material softening in the crack tip region. With the new model, the computed crack speed and crack length evolution match very closely those found experimentally.

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