scholarly journals Determination of Holmquist–Johnson–Cook Constitutive Parameters of Coal: Laboratory Study and Numerical Simulation

Processes ◽  
2019 ◽  
Vol 7 (6) ◽  
pp. 386 ◽  
Author(s):  
Beijing Xie ◽  
Zheng Yan ◽  
Yujing Du ◽  
Zeming Zhao ◽  
Xiaoqian Zhang
Keyword(s):  
Numerical Simulation ◽  
Constitutive Model ◽  
Split Hopkinson Pressure Bar ◽  
Impact Damage ◽  
Triaxial Compression ◽  
Model Parameters ◽  
Compression Tests ◽  
Hopkinson Pressure Bar ◽  
The Impact ◽  
Constitutive Parameters

The main sensitivity parameters of the Holmquist–Johnson–Cook constitutive model for coal were obtained from a variety of tests such as uniaxial compression, uniaxial cyclic loading, splitting and triaxial compression tests, as well as the indirect derivation equation of a briquette. The mechanical properties of briquettes under dynamic impact were investigated using a split Hopkinson pressure bar experiment. Based on the experimental measurement of the Holmquist–Johnson–Cook constitutive model, the numerical simulation of briquette was performed using ANSYS/LS-DYNA software. A comparison between experimental and simulation results verified the correctness of simulation parameters. This research concluded that the failure of briquette at different impact velocities started from an axial crack in the middle of the coal body, and the sample was swollen to some extent. By the increase of impact velocity, the severity of damage in the coal body was increased, while the size of the coal block was decreased. Moreover, there was good compliance between experimental and simulated stress wave curves in terms of coal sample failure and fracture morphology at different speeds. Finally, the parameters of the validated Holmquist–Johnson–Cook constitutive model were applied to the numerical simulation model of the impact damage of heading face and the process of coal seam damage in the roadway was visually displayed. The obtained results showed that the Holmquist–Johnson–Cook constitutive model parameters suitable for the prominent coal body were of great significance for the improvement and exploration of the occurrence mechanism of coal and rock dynamic disasters.

scholarly journals On the Development of Material Constitutive Model for 45CrNiMoVA Ultra-High-Strength Steel

Metals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 374 ◽  
Author(s):  
Xin Hu ◽  
Lijing Xie ◽  
Feinong Gao ◽  
Junfeng Xiang
Keyword(s):  
Constitutive Model ◽  
Strain Rate ◽  
High Strength Steel ◽  
Split Hopkinson Pressure Bar ◽  
High Strength ◽  
Model Parameters ◽  
Hopkinson Pressure Bar ◽  
Simulation Accuracy ◽  
Ultra High Strength Steel ◽  
Split Hopkinson

For the implementation of simulations for large plastic deformation processes such as cutting and impact, the development of the constitutive models for describing accurately the dynamic plasticity and damage behaviors of materials plays a crucial role in the improvement of simulation accuracy. This paper focuses on the dynamic behaviors of 45CrNiMoVA ultra-high-strength torsion bar steel. According to investigation of the Split-Hopkinson pressure bar (SHPB) and Split-Hopkinson tensile bar (SHTB) tests at different strain rate and different temperatures, 45CrNiMoVA ultra-high-strength steel is characterized by strain hardening, strain-rate hardening and thermal softening effects. Based on the analysis on the mechanism of the experimental results and the limitation of classic Johnson-Cook (J-C) constitutive model, a modified J-C model by considering the phase transition at high temperature is established. The multi-objective optimization fitting method was used for fitting model parameters. Compared with the classic J-C constitutive model, the fitting accuracy of the modified J-C model significantly improved. In addition, finite element simulations for SHPB and SHTB based on the modified J-C model are conducted. The SHPB stress-strain curves and the fracture morphology of SHTB samples from simulations are in good agreement with those from tests.

scholarly journals Research On Water-Immersion Softening Mechanism of Coal Rock Mass Based on Split Hopkinson Pressure Bar Experiment

2021 ◽  
Author(s):  
Zhiyuan Liu ◽  
Gang Wang ◽  
Jinzhou Li ◽  
Huaixing Li ◽  
Haifeng Zhao ◽  
...  
Keyword(s):  
Moisture Content ◽  
Coal Sample ◽  
Split Hopkinson Pressure Bar ◽  
Water Immersion ◽  
Compression Tests ◽  
Hopkinson Pressure Bar ◽  
Impact Compression ◽  
Split Hopkinson ◽  
Pressure Bar ◽  
The Impact

Abstract The coal mining process is affected by multiple sources of water such as groundwater and coal seam water injection. Understanding the dynamic mechanical parameters of water-immersed coal is helpful to the safe production of coal mines. The impact compression tests were performed on coal with different moisture contents by using the ϕ50 mm Split Hopkinson Pressure Bar (SHPB) experimental system, and the dynamic characteristics and energy loss laws of water-immersed coal with different compositions and water contents were analyzed. Through analysis and discussion, it is found that: (1) When the moisture content of the coal sample is 0%, 30%, 60%, the stress, strain rate and energy first increase and then decrease with time; (2) When the moisture content of the coal sample increases from 30% to 60%, the stress "plateau" of the coal sample disappears, resulting in an increase in the interval of the compressive stress and a decrease in the interval of the expansion stress. (3) The increase of the moisture content of the coal sample will affect its impact deformation and failure mode. When the moisture content is 60%, the incident rod end and the transmission rod end of the coal sample will have obvious compression failure, and the middle part of the coal sample will also experience expansion and deformation. (4) The coal composition ratio suitable for the impact experiment of coal immersion softening is optimized.

scholarly journals Nonlinear Dynamic Constitutive Model of Frozen Sandstone Based on Weibull Distribution

2020 ◽  
Vol 2020 ◽  
pp. 1-10 ◽  
Author(s):  
Lei Wang ◽  
Hongming Su ◽  
Shiguan Chen ◽  
Yue Qin
Keyword(s):  
Elastic Modulus ◽  
Constitutive Model ◽  
Strain Rate ◽  
Split Hopkinson Pressure Bar ◽  
Soft Rock ◽  
Strain Curve ◽  
Peak Stress ◽  
Experimental Results ◽  
Compression Tests ◽  
Hopkinson Pressure Bar

To obtain the dynamic mechanical properties of frozen sandstone at different temperatures (i.e., 20°C, −10°C, −20°C, and −30°C), dynamic uniaxial compression tests of saturated sandstone are conducted using a split-Hopkinson pressure bar. The experimental results demonstrated that the brittleness of the saturated sandstone increased and its plasticity weakened with a decrease in temperature. The peak strength and dynamic elastic modulus of the sandstone were positively correlated with its strain rate. The peak stress was most sensitive to the strain rate at −10°C, and the elastic modulus was most sensitive to the strain rate at −30°C. According to the evident segmentation characteristics of the obtained stress-strain curve, a viscoelastic dynamic constitutive model considering the strain rate effect and temperature effect is developed; this model combines a nonlinear (or linear) body and a Maxwell body in parallel with a damage body. The applicability of the constitutive model is also verified using experimental data. The fitting results were demonstrated to be in good agreement with the experimental results. Furthermore, the fitting results serve as reference for the study of the constitutive model of weakly cemented soft rock and the construction of roadway freezing methods.

scholarly journals Constitutive Parameters Identification of AZ31B-H24 Magnesium Alloy and Energy-Absorption Analysis in Structural Panel Use

2018 ◽  
Vol 153 ◽  
pp. 01004
Author(s):  
Yuedong Yang ◽  
Jiqing Chen ◽  
Fengchong Lan ◽  
Wu Zeng ◽  
Zhengwei Ma
Keyword(s):  
Magnesium Alloy ◽  
Constitutive Model ◽  
Energy Absorption ◽  
Split Hopkinson Pressure Bar ◽  
Parametric Identification ◽  
Hopkinson Pressure Bar ◽  
Curve Fit ◽  
Wide Range ◽  
Pressure Bar ◽  
Constitutive Parameters

As a novel lightweight material, AZ31B magnesium alloy is considered as the most potential material to instead baseline steel in some automotive parts. However, their structural use is quite limited and so far proper numerical modeling has not been developed to represent magnesium alloy. In present study, the Split Hopkinson Pressure Bar (SHPB) test is utilized to investigate material dynamic mechanism for AZ31B-H24 over a wide range of strain rates from 1389 s-1 to 7296 s-1. Parametric identification for Johnson-Cook (J-C) constitutive model available in the commercial finite element package LS-DYNA is carried out. Proper parameters are obtained by curve fit using genetic algorithm with experimental results. Constitutive model after parametric identification is applied to automotive outer panels for crashworthiness analysis. Energy absorption with magnesium alloy substituted baseline steel under lightweight 51.18% is obtained and the key problem of thin-walled magnesium alloy applied in automotive structure is advanced.

scholarly journals Numerical Simulation of Split-Hopkinson Pressure Bar Tests for the Combined Coal-Rock by Using the Holmquist–Johnson–Cook Model and Case Analysis of Outburst

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Beijing Xie ◽  
Dongxin Chen ◽  
Hao Ding ◽  
Guangyu Wang ◽  
Zheng Yan
Keyword(s):  
Numerical Simulation ◽  
Rock Burst ◽  
Split Hopkinson Pressure Bar ◽  
Tensile Failure ◽  
Hopkinson Pressure Bar ◽  
Finite Element Software ◽  
Split Hopkinson ◽  
Coal Rock ◽  
Pressure Bar ◽  
The Impact

In the coal and rock dynamic disasters, such as the rock burst, dynamic load damage often acts simultaneously on the combined coal and rock mass. Based on the split-Hopkinson pressure bar (SHPB) test of the combined coal and rock with a bullet velocity of 4.590–8.791 m/s, the numerical model of four kinds of combined coal and rock with different sandstone-coal-sandstone ratios, including 1 : 1 : 1, 2 : 1 : 1, 1 : 1 : 2, and 1 : 2 : 1, is investigated. A finite element software (LS-DYNA) and the Holmquist–Johnson–Cook (HJC) constitutive model of rock are employed in these regards. The stress waveform, the oscillation phenomenon of stress wave, and the damage process of the specimen in the impact test of the composite coal and rock are studied. The obtained results show that the compression-shear failure is the main failure mode of the coal body and the tensile failure of the sandstone along the axial direction in the composite coal-rock specimens. Moreover, it is found that combination of coal and rock samples is mainly destroyed by the coal body, which has no correlation with the impact speed and combination mode. Finally, numerical simulation about Hongling coalmine extralarge tunnel malfunction is carried out. Obtained results showed the protruding and stress change processes of the coal seam of the tunnel exposing. It is found that the simulation results are in an excellent agreement with those from the field investigation. The present study may provide a reference for further understanding the mechanism of the coal and rock dynamic disasters, such as the rock burst.

Study on Dynamic Behavior of AFRP-Wrapped Circular Concrete Specimens under Repeated Impacts

2017 ◽  
Vol 25 (1) ◽  
pp. 103-112
Author(s):  
Hengwen Song ◽  
Hui Yang ◽  
Shi Zhang
Keyword(s):  
Strain Rate ◽  
Split Hopkinson Pressure Bar ◽  
Impact Damage ◽  
Peak Stress ◽  
Hopkinson Pressure Bar ◽  
Split Hopkinson ◽  
Repeated Impacts ◽  
Damage Condition ◽  
Pressure Bar ◽  
The Impact

A series of damage tests and axially repeated compressive tests with high strain rates were conducted to investigate the behavior of aramid fiber reinforced polymer (AFRP) wrapped concrete under repeated impacts. The relation between damage condition and variables such as impact number and polymer thickness were examined. The tests were performed using a 100 mm diameter Split Hopkinson Pressure Bar (SHPB) apparatus and a nonmetal supersonic test meter. Various AFRP layers were applied to produce varied confinement ratios. The experimental results indicated that the AFRP-wrapped concrete exhibited excellent performance in resisting repeated impacts. Also, the specimens maintained their shapes and bearing capacity after multiple impacts with a mean strain rate of 50 s−1. No distinct decline was observed from the history of peak stress and impact toughness in AFRP-wrapped concrete. Moreover, additional AFRP layers significantly decreased the impact damage on the core concrete, as reflected by the different strain rate histories in damage progression.

Research on the Characteristics of Electromagnetic Radiation in the Impact Damage Process of Coal

2014 ◽  
Vol 1006-1007 ◽  
pp. 121-127
Author(s):  
Jin Gui Wang ◽  
Su Zhang ◽  
Li Hao Ai ◽  
Ying Feng Sun
Keyword(s):  
Electromagnetic Radiation ◽  
Noise Reduction ◽  
Split Hopkinson Pressure Bar ◽  
Impact Damage ◽  
Test System ◽  
Hopkinson Pressure Bar ◽  
Hilbert Huang Transform ◽  
Damage Process ◽  
Reduction Effect ◽  
The Impact

The damage process of coal is often accompanied by electromagnetic radiation. Researches on the characteristics of electromagnetic radiation in the impact damage of coal are significance. Due to the presence of background noise of environment and instrument. The acquisition signals contain noise. So noise reduction is also important. Using split Hopkinson pressure bar (SHPB) and transient ZDKT-1 type magnetic vibration test system, we acquisition electromagnetic radiation signal in the process of impact damage of coal. By using Hilbert huang transform (HHT),we reduced the noise in the original signal. Then we analysed the characteristics of electromagnetic radiation signal after noise reduction. It is demonstrated that: (1) It can get good noise reduction effect for electromagnetic radiation signal by HHT method.(2) The characteristics of signals show that straight line rises in the beginning, index decreases in the middle, and small oscillation occurs in the end.(3) The duration of electromagnetic radiation signal are less than 2 s , and the frequency are 0 ~ 40 Hz. (4) The amplitude of signals increase with impact velocities.

scholarly journals Study of statistical damage constitutive model of layered composite rock under triaxial compression

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Yong-Sheng Liu ◽  
Zhuan-Zhuan Qiu ◽  
Xue-Cai Zhan ◽  
Hui-Nan Liu ◽  
Hai-Nan Gong
Keyword(s):  
Constitutive Model ◽  
Axial Strain ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Layered Composite ◽  
Model Parameters ◽  
Compression Tests ◽  
Fitting Method ◽  
Confining Pressures ◽  
Curve Fitting Method

Abstract The layered composite rock was subjected to triaxial compression tests under constant confining pressure and the stress–strain curves under different confining pressures were obtained. Based on the continuous damage theory and statistical strength theory, it is assumed that the strength of rock microelements obeys Weibull distribution by taking the defects such as random micro-cracks in the rock into account. The statistical constitutive model of layered composite rock with damage correction is established by taking the axial strain of rock as a random distribution variable of microelement strength. The model parameters were determined by the curve fitting method and referring to some test parameters. By comparing the experimental data and the constitutive model curve, the rationality and feasibility of the model are verified.

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