scholarly journals Numerical Study on the Dynamic Fracture Energy of Concrete Based on a Rate-Dependent Cohesive Model

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7421
Author(s):  
Penglin Zhang ◽  
Zhijun Wu ◽  
Yang Liu ◽  
Zhaofei Chu
Keyword(s):  
Strain Rate ◽  
Fracture Energy ◽  
Dynamic Fracture ◽  
Loading Rate ◽  
Numerical Study ◽  
Damage Zone ◽  
Concrete Fracture ◽  
Obvious Effect ◽  
Cohesive Model ◽  
Rate Dependent

As an important parameter for concrete, fracture energy is difficult to accurately measure in high loading rate tests due to the limitations of experimental devices and methods. Therefore, the utilization of numerical methods to study the dynamic fracture energy of concrete is a simple and promising choice. This paper presents a numerical investigation on the influence of loading rate on concrete fracture energy and cracking behaviors. A novel rate-dependent cohesive model, which was programmed as a user subroutine in the commercial explicit finite element solver LS-DYNA, is first proposed. After conducting mesh sensitivity analysis, the proposed model is calibrated against representative experimental data. Then, the underlying mechanisms of the increase in fracture energy due to a high strain rate are determined. The results illustrate that the higher fracture energy during dynamic tension loading is caused by the wider region of the damage zone and the increase in real fracture energy. As the loading rate increases, the wider region of the damage zone plays a leading role in increasing fracture energy. In addition, as the strain rate increases, the number of microcracks whose fracture mode is mixed mode increases, which has an obvious effect on the change in real fracture energy.

A loading rate dependent cohesive model for concrete fracture

2012 ◽  
Vol 82 ◽  
pp. 195-208 ◽  
Author(s):  
A.L. Rosa ◽  
R.C. Yu ◽  
G. Ruiz ◽  
L. Saucedo ◽  
J.L.A.O. Sousa
Keyword(s):  
Loading Rate ◽  
Concrete Fracture ◽  
Cohesive Model ◽  
Rate Dependent

A viscous-cohesive model for concrete fracture in quasi-static loading rate

2020 ◽  
Vol 228 ◽  
pp. 106893
Author(s):  
Fábio Luis Gea dos Santos ◽  
José Luiz Antunes de Oliveira e Sousa
Keyword(s):  
Static Loading ◽  
Loading Rate ◽  
Concrete Fracture ◽  
Cohesive Model

Dynamic Fracture of Natural Rubber3

2007 ◽  
Vol 35 (4) ◽  
pp. 252-275 ◽  
Author(s):  
Ali A. Al-Quraishi ◽  
Michelle S. Hoo Fatt
Keyword(s):  
Finite Element ◽  
Carbon Black ◽  
Natural Rubber ◽  
Strain Rate ◽  
Fracture Energy ◽  
Dynamic Fracture ◽  
High Strain ◽  
Field Strain ◽  
Far Field ◽  
Strain Rates

Abstract This paper illustrates how the fracture energy of a tensile strip made of unfilled and 25 phr carbon black-filled natural rubber varies with far-field strain rate in the range 0.01–71 s−1. Quasistatic and dynamic fracture tests were performed at room temperature with an electromechanical INSTRON machine, a servo-hydraulic MTS machine, and Charpy tensile apparatus, respectively. It was found that the fracture energy of the unfilled natural rubber did not vary significantly over the range of sample strain rate, but there was significant variation in the fracture energy of the 25 phr carbon black-filled natural rubber from 0.01 to 71 s−1 sample strain rate. The fracture energy of the 25 phr carbon black-filled natural rubber at a sample strain rate of 0.1 s−1 was about three times greater than it was at the 10 s−1 sample strain rate. While the carbon black fillers increased the fracture energy of natural rubber by about 200% at quasistatic sample strain rates (0.01–0.1 s−1) and at 71 s−1, the carbon black fillers did nothing to improve the fracture energy of natural rubber at sample strain rates between 5 and 29 s−1. In this strain rate range, the fracture energy of 25 phr carbon black-filled natural rubber was almost the same as that in the unfilled natural rubber. The variation in the fracture energy with far-field strain rate was due to changes in the material behavior of natural rubber at high strain rates. Finite element analysis using a high-strain-rate constitutive equation for the 25 phr carbon black rubber specimen was used to calculate the fracture energy of the specimen at a sample strain rate of 55 s−1, and good agreement was found between the test and finite element results.

scholarly journals Strain rate dependence of plastic flow in Ce-based bulk metallic glass during nanoindentation

2007 ◽  
Vol 22 (2) ◽  
pp. 258-263 ◽  
Author(s):  
B.C. Wei ◽  
L.C. Zhang ◽  
T.H. Zhang ◽  
D.M. Xing ◽  
J. Das ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Metallic Glass ◽  
Strain Rate ◽  
Bulk Metallic Glass ◽  
Loading Rate ◽  
Shear Banding ◽  
Rate Dependence ◽  
Strain Rate Dependence ◽  
Serrated Flow ◽  
Rate Dependent

The strain rate dependence of plastic deformation of Ce60Al15Cu10Ni15 bulk metallic glass was studied by nanoindentation. Even though the ratio of room temperature to the glass transition temperature was very high (0.72) for this alloy, the plastic deformation was dominated by shear banding under nanoindentation. The alloy exhibited a critical loading rate dependent serrated flow feature. That is, with increasing loading rate, the alloy exhibited a transition from less prominent serrated flow to pronounced serrated flow during continuous loading but from serrated to smoother flow during stepped loading.

Relationship Between Crack-Tip Constraint and Dynamic Fracture Initiation Toughness

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
Yuh J. Chao ◽  
Cheng Wang ◽  
Yil Kim ◽  
Chi-Hui Chien
Keyword(s):  
Strain Rate ◽  
Dynamic Load ◽  
Loading Rate ◽  
Crack Tip ◽  
Fracture Initiation ◽  
Initiation Toughness ◽  
Rate Dependent ◽  
High Loading Rate ◽  
Fracture Initiation Toughness ◽  
Crack Tip Constraint

Two-dimensional finite element analyses are performed to study the crack-tip constraint in an elastic-plastic, three point bend specimen under dynamic load. Both strain rate-independent and strain rate-dependent materials are considered to elucidate the difference in response due to the material rate effect. It is first demonstrated that the crack-tip stress fields can be adequately characterized by the J-A2 three-term solution within the region of interest 1<r/(J/σo)<5. Consequently, A2 is used as a constraint parameter in constraint evaluations. Results show that the crack-tip constraint decreases with increasing loading rate in rate-independent material. On the other hand, in rate-dependent material, the crack-tip constraint first increases at low loading rate but later decreases at high loading rate. It appears that there is a competition between constraint loss due to dynamic load and constraint gain due to material sensitivity to strain rate. The effect of crack-tip constraint on fracture initiation toughness under dynamic load Kdyn is then studied using a critical stress failure criterion. The results are consistent with experimental data in (a) reduced dynamic fracture initiation toughness, as compared with the static fracture toughness, at low loading rate such as those obtained by ASTM E23 Charpy tests and (b) elevated fracture toughness at high loading rate as frequently reported by experimental researchers.

A Strain Rate-Dependent Finite Element Model of Drop-Weight Tear Tests for Pipeline Steels

2014 ◽  
Author(s):  
P. S. Yu ◽  
C. Q. Ru
Keyword(s):  
Fracture Toughness ◽  
Strain Rate ◽  
Dynamic Fracture ◽  
Bulk Material ◽  
Element Model ◽  
Dynamic Fracture Toughness ◽  
Crack Speed ◽  
Pipeline Steels ◽  
Rate Dependent ◽  
Present Rate

The influence of crack speed on dynamic fracture toughness of pipeline steel has been observed in some recent tests, although it is still a challenge to obtain a specific relationship between dynamic fracture toughness and crack speed due to the expensive costs of experiments. Meanwhile, the understanding of the dependence of fracture toughness on crack speed is critical for material selection and crack-arrest design in high-strength steel pipelines. The present work develops a strain rate-dependent cohesive zone model and related finite element model to analyze speed-dependent dynamic fracture of pipeline steels observed in recent drop-weight tear tests. Different than most of existing cohesive zone models, the traction-separation law of the present model considers the role of rate of separation, and a strain rate-dependent elastic-viscoplastic constitutive model is employed for the bulk material. The speed-dependences of crack-tip-opening angle (CTOA) and energy dissipation observed in experiments are reproduced in our simulations for crack speed up to 150 m/s. A remarkable feature of the present work is that the present rate-dependent model can predict speed-dependent fracture as a consequence of the strain rate effect even when all fixed material parameters are speed-independent. These results suggest that the strain rate effect in the bulk material could be largely responsible for the speed-dependent dynamic fracture of pipeline steels, and the present rate-dependent model could be used to simulate dynamic fracture of pipeline steels especially when experiments are difficult or too expensive.

scholarly journals Demolition of concrete by thermal shock spallation: a mesoscopic numerical study based on embedded discontinuity finite elements

2020 ◽  
Vol 225 (2) ◽  
pp. 191-217
Author(s):  
Timo Saksala
Keyword(s):  
Heat Flux ◽  
Finite Elements ◽  
Plane Strain ◽  
Thermal Loading ◽  
Numerical Study ◽  
Concrete Surface ◽  
Concrete Fracture ◽  
Rate Dependent ◽  
Dry Conditions ◽  
Modelling Approach

AbstractThis paper deals with 2D (plane strain) and axisymmetric numerical modelling of concrete fracture processes under mechanical and thermal loading. A mesoscopic modelling approach with an explicit representation of aggregates as Voronoi polygons is chosen while the concrete fracture model is based on rate-dependent embedded discontinuity finite elements with Rankine criterion indicating a new crack initiation. This choice enables the study of the effects of inherent crack populations on the response of concrete under mechanical and thermal loading. In the numerical examples, the performance of the present modelling approach is first demonstrated in the uniaxial compression and tension tests under plane strain conditions. Then, the problem of thermal spallation of concrete surface under dry conditions due to a high intensity, short duration heat flux is simulated under axisymmetric conditions. The underlying uncoupled thermo-mechanical problem is solved with an explicit time marching scheme based on the staggered approach. Different heat flux intensities and heating times as well as combined effect of surface roughness and pre-stress field are tested. The simulation results suggest that demolition of concrete structures by heat shock is a viable method.

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