Numerical Simulation of Stress Wave Propagation in Coal-Rock Combination Media

2012 ◽  
Vol 594-597 ◽  
pp. 542-551 ◽  
Author(s):  
Dong Jie Xue ◽  
Hong Wei Zhou ◽  
Jia Dun Liu ◽  
Hai Yang Yi
Keyword(s):  
Numerical Simulation ◽  
Strain Rate ◽  
Stress Wave ◽  
Incident Wave ◽  
Constant Strain Rate ◽  
Stress Wave Propagation ◽  
Propagation Mode ◽  
Reflected Wave ◽  
Strain And Strain Rate ◽  
Coal Rock

By establishing numerical simulation model of SPBH and comparing dynamic response of four kinds of coal-rock combination media subjected to three different stress waves, changes law of the reflected wave, incident wave, strain and strain rate were obtained. The results show that rock-rock combination has almost the same rules of reflected waves as rock-coal combination, coal-coal combination and coal-rock combination, while the coal-coal combination has the largest peak of reflected wave, followed by the coal-rock combination and the rock-coal combination, and the rock-rock combination ranks last. With increasing incident wave peak, the coal-rock combination weakens the peak more apparently. Strain softening occurs in coal samples under stress wave of peak value with the law that strain rate firstly increases, and then maintains a constant value, continues to increase and then decreases, increases reversely and then decreases. Constant strain rate of the phenomenon over time occurs. The results provide guidelines for both the study on propagation mode of stress wave in coal and rock combination media and the prevention of mining-induced dynamic disasters.

scholarly journals Evolution of specimen strain rate in split Hopkinson bar test

2019 ◽  
Vol 233 (13) ◽  
pp. 4667-4687 ◽  
Author(s):  
Hyunho Shin ◽  
Jong-Bong Kim
Keyword(s):  
Strain Rate ◽  
Rate Equation ◽  
Constant Strain Rate ◽  
Strain Curve ◽  
Hopkinson Bar ◽  
Stress Strain ◽  
Split Hopkinson Bar ◽  
Specimen Diameter ◽  
Strain And Strain Rate ◽  
Split Hopkinson

The specimen strain rate in the split Hopkinson bar (SHB) test has been formulated based on a one-dimensional assumption. The strain rate is found to be controlled by the stress and strain of the deforming specimen, geometry (the length and diameter) of specimen, impedance of bar, and impact velocity. The specimen strain rate evolves as a result of the competition between the rate-increasing and rate-decreasing factors. Unless the two factors are balanced, the specimen strain rate generally varies (decreases or increases) with strain (specimen deformation), which is the physical origin of the varying nature of the specimen strain rate in the SHB test. According to the formulated strain rate equation, the curves of stress–strain and strain rate–strain are mutually correlated. Based on the correlation of these curves, the strain rate equation is verified through a numerical simulation and experiment. The formulated equation can be used as a tool for verifying the measured strain rate–strain curve simultaneously with the measured stress–strain curve. A practical method for predicting the specimen strain rate before carrying out the SHB test has also been presented. The method simultaneously solves the formulated strain rate equation and a reasonably estimated constitutive equation of specimen to generate the anticipated curves of strain rate–strain and stress–strain in the SHB test. An Excel® program to solve the two equations is provided. The strain rate equation also indicates that the increase in specimen stress during deformation (e.g., work hardening) plays a role in decreasing the slope of the strain rate–strain curve in the plastic regime. However, according to the strain rate equation, the slope of the strain rate–strain curve in the plastic deformation regime can be tailored by controlling the specimen diameter. Two practical methods for determining the specimen diameter to achieve a nearly constant strain rate are presented.

The Numerical Simulation Research of Thermal Mechanical Simulation Compression Behavior with Uneven Temperature on End

2013 ◽  
Vol 762 ◽  
pp. 368-373
Author(s):  
Lei Yao ◽  
Zheng Fang ◽  
Zhang Ge
Keyword(s):  
Numerical Simulation ◽  
Temperature Field ◽  
Friction Coefficient ◽  
Strain Rate ◽  
Deformation Resistance ◽  
Simulation Research ◽  
Compression Behavior ◽  
Mechanical Simulation ◽  
Strain And Strain Rate ◽  
Lubrication Condition

The study has been performed concerning the influence of temperature field created by heat conduction between sample and the anvils, and the influence of lubrication condition (friction coefficient) on thermal mechanical compression test with numerical simulation, with regard to deformation resistance and distributions of strain and strain rate. The results show that temperature field has an effect on deformation resistance and distributions of strain and strain rate. That will influence on the results from thermal mechanical simulation tests. Further, the results also show that friction coefficient has no influence on deformation resistance, but the friction coefficient will result in uneven distribution of strain and strain rate.

The mechanical properties of pure iron tested in compression over the temperature range 2 to 293 °K

1967 ◽  
Vol 261 (1121) ◽  
pp. 253-287 ◽  
Keyword(s):  
Mechanical Properties ◽  
Flow Stress ◽  
Strain Rate ◽  
Single Crystals ◽  
Yield Stress ◽  
Low Temperatures ◽  
Pure Iron ◽  
Constant Strain Rate ◽  
Frictional Stress ◽  
Strain And Strain Rate

The mechanical properties of pure iron single crystals and of polycrystalline specimens of a zone-refined iron have been measured in compression over the temperature and strain rate ranges 2.2 to 293 °K and 7 x 10 -7 to 7 x 10 -3 s -1 respectively. Various yield stress parameters were determined as functions of both temperature and strain rate, and the reversible changes in flow stress produced by isothermal changes of strain rate or by changes of temperature at constant strain rate were also measured as functions of temperature, strain and strain rate. Both the temperature variation of the flow stress and the strain rate sensitivity of the flow stress were generally identical for the single crystals ( ca. 0.005/M carbon) and the polycrystalline specimens ( ca. 9/M carbon). At low temperatures, the temperature dependence of the yield stress was smaller than that of the flow stress at high strains, probably because of the effects of mechanical twinning, but once again the behaviour of single and polycrystalline specimens was very similar. Below 10 °K, both the flow stress and the extrapolated yield stress were independent of temperature. The results show that macroscopic yielding and flow at low temperatures are both governed by the same deformation mechanism, which is not very impurity sensitive, even in the very low carbon range covered by the experiments. The flow stress near 0 °K is ca. 5.8 x 10 -3 u where [i is the shear modulus. On the basis of a model for thermally activated flow, the activation volume at low temperatures (high stresses) is found to be ca. 5 b 3 . The exponent in the empirical power law for the dislocation velocity against stress relation is ca. 3 near room temperature, but becomes quite large at low temperatures. The results indicate that macroscopic deformation at low temperatures is governed by some kind of lattice frictional stress (Peierls-Nabarro force) acting on dislocations.

VERIFICATION OF THE SHB TEST RESULTS BASED ON THE ONE-DIMENSIONAL STRESS WAVE THEORY

2008 ◽  
Vol 22 (09n11) ◽  
pp. 1068-1073
Author(s):  
TOMOKAZU MASUDA ◽  
KENJI SAITO ◽  
IZUMI MORITA ◽  
SHUSHI IKEDA ◽  
KOICHI MAKII ◽  
...  
Keyword(s):  
Strain Rate ◽  
Stress Wave ◽  
High Speed ◽  
Wave Theory ◽  
High Speed Photography ◽  
Strain Rates ◽  
One Dimensional ◽  
Strain And Strain Rate ◽  
Deformation Behaviors ◽  
The One

In order to evaluate dynamic deformation behaviors under high strain rates, Kobe Steel has developed and applied a Split-Hopkinson Bar (SHB) apparatus. This paper discusses the validity of the strain measurements and strain rates measured by this SHB apparatus. The strain waves that propagated in the incident and transmitted bars and the specimen are captured using a high-resolution type high-speed photography in detail. The strain wave propagated many times in the incident and transmitted bars and the specimen when the specimen was not broken. The amount of the deformation of the specimen decreases with the propagation frequency of the incident wave. On the other hand, to improve accuracy at the strain and strain rate calculated by the one-dimensional stress wave theory, Young's modulus, the longitudinal wave speed, and the density were accurately determined. It was understood that the calculation value showed the strain and strain rate captured with the high-speed photography are a good agreement. As a result, the validity of the measurement accuracy of this SHB could be shown.

The Buckling Mechanism of Square Tube Subjected to the Impact of a Mass

2014 ◽  
Vol 624 ◽  
pp. 267-271
Author(s):  
Zhu Hua Tan ◽  
Bo Zhang ◽  
Peng Cheng Zhai
Keyword(s):  
Numerical Simulation ◽  
Wave Propagation ◽  
Numerical Methods ◽  
Stress Wave ◽  
Significant Influence ◽  
Strain Localization ◽  
Stress Wave Propagation ◽  
Low Velocity ◽  
Buckling Modes ◽  
The Impact

The dynamic response of the square tube subjected to the impact of a mass was investigated by using experimental and numerical methods. The square tube was impacted by a mass at the velocity ranging from 5.09 m/s to 12.78 m/s, and different progressive buckling modes were obtained. The numerical simulation was also carried out to analyze the buckling mechanism of the square tube. The results show that there is obvious stress wave propagation and strain localization in the tube, which has a significant influence on the buckling mechanism of the tube. The stress wave and inertia of the mass play different roles at various impact velocities. And buckling mechanism at low velocity is mainly caused by stress wave, whereas the buckling mechanism at high velocity is resulted from the inertial of the mass.

Evaluation of the AZ31 Formability According to Temperature Using a Constant Strain Rate Test

2009 ◽  
Vol 83-86 ◽  
pp. 375-383
Author(s):  
G. Palumbo ◽  
Donato Sorgente ◽  
Luigi Tricarico
Keyword(s):  
Strain Rate ◽  
Central Region ◽  
Three Dimensional ◽  
Constant Strain Rate ◽  
Tensile Tests ◽  
Equivalent Strain ◽  
Speed Profile ◽  
Stretch Forming ◽  
Punch Speed ◽  
Strain And Strain Rate

The present paper is focused on the Finite Element modeling of the Marciniak stretch-forming test in warm condition. Such a test was proposed by the authors for evaluating the warm formability of the Mg alloy AZ31 according to the most important parameters: the temperature and the strain rate. Tensile tests confirmed the large influence of the strain rate on the deformation of the AZ31, especially when the test temperature is over 200°C. Three dimensional FE simulations were thus carried out in order to analyze the strain and strain rate evolutions during the formability test at the temperature of 200°C. In particular, simulations were aimed at investigating the effect of the specimen’s geometry on the strain rate evolution in the central region, where failure occurs during the Marciniak stretch-forming test. An equation for calculating the punch speed profile able to keep a constant equivalent strain rate in the central region of the specimen has been furnished according to the geometry of the specimen. Its efficiency was validated by means of additional simulations implementing the punch speed profile calculated using the proposed approach.

scholarly journals NUMERICAL SIMULATION OF STRESS WAVE PROPAGATION IN SAP CONCRETE

2018 ◽  
Vol 27 (2) ◽  
pp. 255-267
Author(s):  
Zhenqun Sang ◽  
Zhiping Deng ◽  
Jianglin Xi ◽  
Huibin Yao ◽  
Jiang Wu
Keyword(s):  
Numerical Simulation ◽  
Wave Propagation ◽  
Stress Wave ◽  
Stress Wave Propagation

Numerical Simulation of Stress Wave Propagation Induced by Cut Blasting in Multi-Media

2012 ◽  
Vol 249-250 ◽  
pp. 22-25
Author(s):  
Guo Liang Yang ◽  
Ren Shu Yang ◽  
Chuan Huo ◽  
Yu Long Che
Keyword(s):  
Numerical Simulation ◽  
Stress Wave ◽  
Strong Shock ◽  
Simulation Method ◽  
Stress Waves ◽  
Stress Wave Propagation ◽  
Weathered Rock ◽  
Plastic Damage ◽  
Multi Media ◽  
Set Up

Explosive blasting in rock and other media could induce strong shock wave. Near blasting zone, the blasting energy mainly break rock. Slightly far away from borehole, the blasting energy induces plastic damage. Farther afield, this kind of energy presents elastic deformation. In cut blasting, multi-boreholes initiate at the same time, multi-column stress waves occur superimpose and converge. Especially in multi-media, this process is extremely complex. Adopt numerical simulation method, set up multi-media model, which include weathered rock, highly weathered rock and plain fill. This paper simulated the propagation process of stress wave in these medias. Revealed the propagation mechanics of stress wave.

scholarly journals Numerical Analysis and Experiment for Stress Wave Propagation in Two Connected Cylindrical Bodies with Different Cross-Sectional Area and Same Mechanical Impedance

2018 ◽  
Vol 183 ◽  
pp. 01033
Author(s):  
Hidetoshi Kobayashi ◽  
Yuya Seo ◽  
Kinya Ogawa ◽  
Keitaro Horikawa ◽  
Ken-ichi Tanigaki
Keyword(s):  
Stress Wave ◽  
Incident Wave ◽  
Mechanical Impedance ◽  
Local Deformation ◽  
Cross Sectional Area ◽  
Stress Wave Propagation ◽  
Sectional Area ◽  
Cross Sectional ◽  
Reflected Waves ◽  
And Control

In this study, the behaviour of elastic stress wave propagating two connected cylindrical bodies was examined using dynamic finite element method (FEM). They consist of two bodies with different cross-sectional area, different Young’s modulus and identical mechanical impedance. It was found that when an incident wave passes through the boundary step between two different cross-sectional areas, a pair of reflected waves which has the same amplitude and opposite sign was observed, despite the same mechanical impedance. This phenomenon appears to be caused by the loading and unloading the boundary section due to the arrival and the passage of incident wave. It was also found that a connection manner to insert the smaller diameter cylinder into the other cylinder with a little length is quite effective for the reduction of the reflected wave, because of the superposition of waves from two edges and control of local deformation. This phenomenon was verified by a series of impact experiments using two cylindrical bodies connected by interference fit.

Finite Element Modeling and Numerical Simulation of Superplastic Forming of 8090 Al-Li Alloy in a Rectangular Die

2012 ◽  
Vol 487 ◽  
pp. 116-121 ◽  
Author(s):  
M. Balasubramanian ◽  
K. Ramanathan ◽  
Ke Zhu
Keyword(s):  
Numerical Simulation ◽  
Finite Element ◽  
Strain Rate ◽  
Physical Phenomenon ◽  
Tensile Elongation ◽  
Constant Strain Rate ◽  
Superplastic Forming ◽  
Alloy Sheet ◽  
Low Flow ◽  
Polycrystalline Materials

Superplasticity is a physical phenomenon associated with certain polycrystalline materials which exhibit very high tensile elongation prior to fracture under particular conditions of strain rate and temperature. Aluminium alloy undergoes superplastic elongation in the order of a few thousands percent in elongation with low flow stresses. Superplastic forming processes can provide products with integral structure, light weight and superior strength, all of which are of particular importance for aerospace and automotive components. In the present study an analytical model was developed for a rectangular component by considering constant strain rate. This paper attempts to explore the superplastic behaviors of 8090 Al-Li alloy sheet into a rectangular die using blow forming technique. This has been done by a simple theoretical model and by numerical simulation using standard finite element code ABAQUS. The numerical and analytical results agree reasonably well for both the analytical and theoretical values with regard to variation in pressure and time.

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