scholarly journals Study on Dynamic Constitutive Model of Weakly Consolidated Soft Rock in Western China

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Lei Wang ◽  
Hongming Su ◽  
Yue Qin ◽  
Shiguan Chen
Keyword(s):  
Constitutive Equation ◽  
Constitutive Model ◽  
Split Hopkinson Pressure Bar ◽  
Soft Rock ◽  
Frozen Soil ◽  
Constitutive Relationship ◽  
Western China ◽  
Parameter Determination ◽  
Engineering Practice ◽  
The Impact

To obtain the impact mechanical response and establish the dynamic damage constitutive relationship of frozen sandstone at low temperature conditions, the impact test of Cretaceous red sandstone under different temperatures was conducted using a split Hopkinson pressure bar (SHPB) device. According to the characteristics of the stress-strain curves obtained by the test, a constitutive model considering the damage effect, temperature effect, and strain rate effect was established, which was improved by Zhu–Wang–Tang (Z–W–T) constitutive model. It was proved that the fitting curves of constitutive equation were in good agreement with the test curves. The fluctuation amplitude of fitting error was controlled within ±4 MPa. The physical meaning of each parameter of the constitutive model is clear, and most of them are fixed values. The selection range of variable parameters and the related change rules are confirmed, which improves the practicability of constitutive model. The constitutive equation can well describe the nonlinear features of this kind of frozen sandstone under impact loading. It was also found that the constitutive equation was applicable to express the dynamic mechanical properties of rock-like materials such as hard rock, soft rock, frozen soil, raw coal, and concrete. It can be referred to the parameter determination method in this paper to study and determine the parameters, reduce the difficulty of parameter selection, and improve the practicability of the constitutive model and parameters, so as to guide the engineering practice better.

An Experimental Study on Dynamic Constitutive Relationship of 7075-T651 Aluminum Alloy

2013 ◽  
Vol 816-817 ◽  
pp. 84-89
Author(s):  
Yong Gang Kang ◽  
Yuan Yang ◽  
Jie Huang ◽  
Jing Hang Zhu
Keyword(s):  
Aluminum Alloy ◽  
Constitutive Equation ◽  
Strain Rate ◽  
Split Hopkinson Pressure Bar ◽  
Flow Behavior ◽  
Constitutive Relationship ◽  
Hopkinson Pressure Bar ◽  
Experiment Data ◽  
Static Compression ◽  
Quasi Static Compression

7075-T651 aluminum alloy are widely used in aeronautical applications such as wing panels, but there is no corresponding constitutive model for it now. In this paper, the flow behavior of 7050-T651 aluminum alloy was investigated by Split Hopkinson Pressure Bar (SHPB) and quasi-static compression experiment system. The strain hardening parameters were obtained by quasi-static compression experiment data, and the strain rate hardening parameters at various strain rates (1000-3000s-1) and room temperature, and the thermal softening parameter at various temperatures (20-300°C) where strain rate is 3000s-1 were obtained by SHPB experiment data. Then the constitutive equation of 7075-T651 aluminum alloy is obtained based on Johnson-Cook constitutive equation model.

Dynamic mechanical experiments and microstructure constitutive model of frozen soil with different particle sizes

2017 ◽  
Vol 27 (5) ◽  
pp. 686-706 ◽  
Author(s):  
Zhiwu Zhu ◽  
Zhijie Liu ◽  
Qijun Xie ◽  
Yesen Lu ◽  
Dingyun Li
Keyword(s):  
Constitutive Model ◽  
Evolution Equations ◽  
Split Hopkinson Pressure Bar ◽  
Frozen Soil ◽  
Particle Sizes ◽  
Hopkinson Pressure Bar ◽  
Dynamic Mechanical ◽  
Micro Cracks ◽  
Split Hopkinson ◽  
Pressure Bar

To reveal the influences of soil particle size on the dynamic impact mechanical properties of frozen soil, four groups of frozen soil specimens composed of different particle sizes are tested using a split-Hopkinson pressure bar. Based on the Druger–Prager failure criterion and coupled damage-plasticity, a dynamic micro-constitutive model is established for describing the dynamic mechanical behavior of the frozen soil. Macroscopically, frozen soil is assumed to be homogeneous and continuous, although a large number of micro-cracks and micro-voids are distributed randomly throughout the volume. When a frozen soil specimen is subjected to a substantial shock, the propagation of micro-cracks and the collapse of micro-voids can induce damage. The evolution equations of the two damage mechanisms are proposed. Finally, through a comparison, it was shown that simulation results agreed well with the experimental results, thus validating the suitability of the developed model.

A constitutive model for frozen soil based on rate-dependent damage evolution

2017 ◽  
Vol 27 (10) ◽  
pp. 1589-1600 ◽  
Author(s):  
Chenxu Cao ◽  
Zhiwu Zhu ◽  
Tiantian Fu ◽  
Zhijie Liu
Keyword(s):  
Constitutive Model ◽  
Damage Evolution ◽  
Mechanical Response ◽  
Split Hopkinson Pressure Bar ◽  
Frozen Soil ◽  
Experimental Results ◽  
Strain Rates ◽  
Hopkinson Pressure Bar ◽  
Dynamic Mechanical ◽  
Rate Dependent

The deformation of frozen soil under impact loading is usually accompanied by the evolution of internal defects and microdamage. By taking the strain and strain rates into account, a rate-dependent damage evolution law is proposed in this study, under the assumption of equivalent strain. Subsequently, a damage-modified rate-dependent constitutive model is proposed to describe the dynamic mechanical properties of frozen soil. A split Hopkinson pressure bar is utilized to test the dynamic mechanical response of frozen soil at different temperatures and high strain rates. The experimental results show that frozen soil produces obvious strain rate and temperature effects, and that there is a linear relationship between the peak stress and temperature. The theoretical results of the proposed constitutive model agree well with the experimental results, verifying the applicability of the model.

scholarly journals Frost Resistance of Desert Sand Concrete

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Haifeng Liu ◽  
Yingchang Ma ◽  
Jurong Ma ◽  
Weiwu Yang ◽  
Jialing Che
Keyword(s):  
Constitutive Model ◽  
Frost Resistance ◽  
Experimental Results ◽  
Western China ◽  
Engineering Practice ◽  
Peak Strain ◽  
Medium Sand ◽  
Freeze Thaw ◽  
Desert Sand ◽  
Engineering Cost

Demand for medium sand has increased greatly with increasing infrastructure construction items. The shortage of construction sand resources has become a serious problem in many districts. It not only increases the engineering cost, and the overexploitation of river sand and mountain as medium sand also brings a series of serious environment problems. There are abundant desert sand (DS) resources in western China. If DS resources can be used to substitute medium sand to produce desert sand concrete (DSC), which was suitable for engineering practice, the environment can be improved and engineering cost can be reduced. Although many researchers had focused on the mechanical performance of DSC, there were few documents on the frost resistance of DSC. Frost resistance experiments of DSC with 50% desert sand replacement ratio (DSRR) and ordinary concrete (OC) were performed in this paper. Influence of freeze-thaw cycles on the mechanical properties of OC and DSC was analyzed. Experimental results showed that, with increasing freeze-thaw cycles, the damage, peak strain, and porosity increased, while elastic modulus, Poisson's ratio, and peak stress declined, the stress-strain curves tended to be flat. Under the same condition of freeze-thaw cycles, the frost resistance of DSC with 50% DSRR was higher than that of OC. Constitutive model of DSC after different freeze-thaw cycles was formulated. The results predicted by constitutive model agreed well with experimental results, which can provide technical support for DSC engineering practice.

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.

The Dynamic Mechanical Properties of Oxygen Free Copper under the Impact Load

2016 ◽  
Vol 1136 ◽  
pp. 543-548 ◽  
Author(s):  
Qing Feng Liu ◽  
Ning Chang Wang ◽  
Lan Yan ◽  
Feng Jiang ◽  
Hui Huang
Keyword(s):  
Mechanical Properties ◽  
Constitutive Model ◽  
Strain Rate ◽  
Power Law ◽  
Split Hopkinson Pressure Bar ◽  
True Strain ◽  
Dynamic Mechanical Properties ◽  
Experimental Result ◽  
Dynamic Mechanical ◽  
The Impact

The dynamic mechanical properties of oxygen free copper has been tested under the different strain rate (4700s-1~21000s-1) at the room temperature by split Hopkinson pressure bar (SHPB), the true stress-true strain curves has been obtained. Power-Law constitutive model and Johnson-Cook constitutive model have been built to fit the experimental result from SHPB test of oxygen free copper, meanwhile, the constitutive model can be applied to the simulation analysis of cutting process. The results show that the oxygen free copper is sensitive to the strain rate. In addition, the Johnson-Cook constitutive model predicts the plastic flow stress of the oxygen free copper more accurately than the Power-Law constitutive model at the high strain rate.

scholarly journals Dynamic Splitting Behavior and the Constitutive Relationship of Frozen Sandstone Containing a Single Fissure

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Tao Zhao ◽  
Gengshe Yang ◽  
Lei Wang ◽  
Hailiang Jia ◽  
Yuzhe Qiao
Keyword(s):  
Tensile Strength ◽  
Crack Propagation ◽  
Failure Modes ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Properties ◽  
Freezing Temperature ◽  
Constitutive Relationship ◽  
Western China ◽  
Dynamic Tensile Strength ◽  
Fractured Sandstone

Fractured sandstone is widely distributed in mining areas throughout western China where the artificial freezing method is extensively adopted to construct vertical shafts. Blasting and excavation generate stress waves and break frozen fractured sandstone. Among the failure modes of frozen fractured rocks, tensile failure is very common. In this study, the dynamic tensile strength of fractured sandstone samples with four crack inclination angles (0°, 30°, 60°, and 90°) is tested by using a split Hopkinson pressure bar at four subzero temperatures (−5, −10, −15, and −20°C). Accordingly, a damage constitutive relationship that considers the effect of fissure angle and freezing temperature is established. The results show the following: (1) the fissure angle does not significantly affect the dynamic tensile strength of frozen fractured sandstone but mainly affects the failure mode of the sample. (2) The dynamic tensile strength of fractured sandstone has a negative linear correlation with the freezing temperature. (3) When the fissure angle is small, only tensile cracking occurs; when the fissure angle is large, tensile cracking occurs along both the loading direction and the fissure; and shear cracking occurs along the fissure as well. (4) Regardless of the fissure angle, tensile cracking is initiated at the stress-concentration zone and then propagates towards the loading end. Fissure ice provides both resistance to deformation and resistance to crack propagation which affects the crack propagation and coalescence mode. A dynamic constitutive relationship is established by considering the effects of fissure angle and freezing temperature on the dynamic properties of frozen fractured sandstone, which is proven to be highly reliable and provides a reference and basis to study the dynamic mechanical properties of similar rock types.

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 Failure Behavior and Constitutive Model of Weakly Consolidated Soft Rock

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Wei-ming Wang ◽  
Zeng-hui Zhao ◽  
Yong-ji Wang ◽  
Xin Gao
Keyword(s):  
Constitutive Model ◽  
Failure Mechanism ◽  
Triaxial Compression ◽  
Soft Rock ◽  
Confining Pressure ◽  
Western China ◽  
Failure Behavior ◽  
Correction Coefficient ◽  
Compression Tests ◽  
Mining Areas

Mining areas in western China are mainly located in soft rock strata with poor bearing capacity. In order to make the deformation failure mechanism and strength behavior of weakly consolidated soft mudstone and coal rock hosted in Ili No. 4 mine of Xinjiang area clear, some uniaxial and triaxial compression tests were carried out according to the samples of rocks gathered in the studied area, respectively. Meanwhile, a damage constitutive model which considered the initial damage was established by introducing a damage variable and a correction coefficient. A linearization process method was introduced according to the characteristics of the fitting curve and experimental data. The results showed that samples under different moisture contents and confining pressures presented completely different failure mechanism. The given model could accurately describe the elastic and plastic yield characteristics as well as the strain softening behavior of collected samples at postpeak stage. Moreover, the model could precisely reflect the relationship between the elastic modulus and confining pressure at prepeak stage.

scholarly journals Descriptions of the mechanical behaviour of the Xigeda formation in Zhaizi village, Yunnan Province, China

2021 ◽  
Author(s):  
Xiaodong Fu ◽  
Yuxiang Du ◽  
Qian Sheng
Keyword(s):  
Constitutive Model ◽  
Water Content ◽  
Mechanical Behaviour ◽  
Damage Mechanics ◽  
Soft Rock ◽  
Friction Angle ◽  
Triaxial Tests ◽  
Engineering Practice ◽  
Jinsha River ◽  
Damage Constitutive Model

Abstract The Xigeda formation is a set of Cenozoic lacustrine semi-rock discontinuously distributed in Southwest China. As a typical hard soil or soft/weak rock, the Xigeda formation causes problems when encountered in engineering practice due to its previously unknown mechanical behaviour. Typical samples taken from Zhaizi village along the Jinsha River have been studied. Influences of both the water content and the confining pressure on strength indices of the Xigeda formation were investigated by performing triaxial tests, and the statistical correlations between the shear strength index and the water content of the Xigeda formation, and its soft rock and soil are analysed. By introducing the tenets of the theory of damage mechanics, a damage constitutive model for the deformation of the Xigeda formation and the influence of the water content thereon was established. The results show that: (a) the peak strength, the cohesion and the friction angle decrease linearly with increasing water content; (b) the sensitivity of cohesion to water content is ranked (in ascending order) as: soft rock, the Xigeda formation, then soil, and the sensitivity of friction angle to water content is ranked (in ascending order) as: soil, the Xigeda formation, then soft rock; (c) the damage constitutive model requires few input variables, has a simple form, and can reflect the deformation and strength characteristics of the Xigeda formation under different confining pressures and water contents. The results provide a mechanism with which to understand and model (for both theoretical study and engineering application) the Xigeda formation.

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