scholarly journals Theoretical and Experimental Study of the Effects of Impact Drilling Parameters on the Properties of Surrounding Rock Damage

2020 ◽  
Vol 2020 ◽  
pp. 1-17
Author(s):  
Zhi Liu ◽  
Wanrong Wu ◽  
Qianhua Hao ◽  
Peng Sun ◽  
Yuangen Ding
Keyword(s):  
Impact Load ◽  
Damage Model ◽  
Testing Machine ◽  
Rock Breaking ◽  
Rock Damage ◽  
Test Bed ◽  
Impact Power ◽  
Drilling Tools ◽  
Longitudinal Acoustic Wave ◽  
Rock Specimens

Using a self-designed hydraulic impact drilling test-bed and rock core drill, six groups of cylindrical granite specimens (93 mm dia. × 200 mm) containing central axial holes formed either by impact or nonimpact drilling methods were tested in uniaxial compression to failure on an Instron 1346 universal testing machine to investigate their mechanics and damage properties. The longitudinal acoustic wave velocities were measured before testing. The rock specimens were grouped according to the method of drilling the central hole (impact load exerted by different impact power and different frequencies for an approximately identical impact power, or nonimpact drilling). In this study, a statistical constitutive damage model based on Weibull distribution was used to calculate the degree of rock damage after drilling center holes. The experimental curves were measured to analyze the damage evolution process and the radius of rock damage. These indicate that rock damage increased with the increase of impact power and decreased with increasing impact frequency at constant impact power. This was also verified by the measured longitudinal wave velocity in all rock specimens. These results have significance for guiding the design of composite rock drilling tools that are dedicated to improving rock-breaking efficiency.

scholarly journals Theoretical and Experimental Study on Damage Properties of Surrounding Rock under High-Frequency Constant Impact Load

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Zhi Liu ◽  
Wanrong Wu ◽  
Zhuang Yao ◽  
Qianhua Hao
Keyword(s):  
High Frequency ◽  
Rock Specimen ◽  
Impact Load ◽  
Testing Machine ◽  
Peak Stress ◽  
Effective Elastic Modulus ◽  
Surrounding Rock ◽  
Hole Diameter ◽  
Rock Damage ◽  
Hole Radius

This paper aims to investigate the mechanics and damage properties of granite by drilling a center hole in Φ50 × 100 mm standard granite specimens under high-frequency constant impact load and then applying them to the uniaxial compression experiment through the INSTRON 1346 universal material testing machine. According to the experimental results, under constant impact load, as the center hole diameter increases, the peak stress of the rock specimen increases accordingly and the effective elastic modulus of the rock specimen decreases first and then increases gradually. In this study, by theoretical analysis of the surrounding rock damage caused under high-frequency impact load, a statistical damage constitutive model that has taken surrounding rock damage into consideration is established on the basis of the Weibull distribution. Meanwhile, the experimental curve is obtained to analyze the damage and damage radius of surrounding rock under high-frequency impact load. The results show that the surrounding rock damage and damage ratio (the ratio of damage radius to center hole radius) of rock decrease with the increase of the center hole diameter. This model that can effectively describe the damage laws of surrounding rock under impact load serves as a guide for the design and development of composite rock-drilling tools.

scholarly journals An Electro Breakdown Damage Model for Granite and Simulation of Deep Drilling by High-Voltage Electropulse Boring

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Changping Li ◽  
Longchen Duan ◽  
Songcheng Tan ◽  
Victor Chikhotkin ◽  
Xiaohui Wang
Keyword(s):  
Numerical Simulation ◽  
Shock Wave ◽  
Electric Field ◽  
High Voltage ◽  
Breakdown Strength ◽  
Damage Model ◽  
Wave Model ◽  
Confining Pressure ◽  
Rock Breaking ◽  
Particle Flow Code

Electropulse rock breaking has wide application prospects in hard rock drilling and ore breaking. At present, there are no suitable physical mathematical models that describe electropulse boring (EPB) processes under confining pressures. In this paper, a high-voltage electropulse breakdown damage model is established for granite, which includes three submodels. It considers electric field distortions inside the rock, and an electric field distribution coefficient is introduced in the electro-breakdown model. A shock-wave model is also constructed and solved. To simulate the heterogeneity of rocks, EPB rock breaking in deep environments is simulated using the two-dimensional Particle Flow Code (PFC2D) program. The solved shock wave is loaded into the model, and confining pressure is applied by the particle servo method. An artificial viscous boundary is used in the numerical simulation model. Using this approach, a complete numerical simulation of electropulse granite breaking is achieved. Breakdown strength and the influences of physical and mechanical parameters on it are also obtained. Time-varying waveforms of electrical parameters are obtained, and the effect of confining pressure on EPB is also described.

scholarly journals Investigation of the influence mechanism of rock damage on rock fragmentation and cutting performance by the discrete element method

2019 ◽  
Vol 6 (5) ◽  
pp. 190116 ◽  
Author(s):  
Si-fei Liu ◽  
Shuai-feng Lu ◽  
Zhi-jun Wan ◽  
Jing-yi Cheng
Keyword(s):  
Cutting Force ◽  
Rock Cutting ◽  
Rock Breaking ◽  
Pulse Number ◽  
Rock Fragmentation ◽  
Cutting Performance ◽  
Tensile Failure ◽  
Rock Damage ◽  
Damage Factor ◽  
Mining Machinery

Rock damage is one of the key factors in the design and model choice of mining machinery. In this paper, the influence of rock damage on rock fragmentation and cutting performance was studied using PFC 2D . In PFC 2D software, it is feasible to get rock models with different damage factors by reducing the effective modulus, tensile and shear strength of bond by using the proportional factors. A linear relationship was obtained between the proportion factor and damage factor. Furthermore, numerical simulations of rock cutting with different damage factors were carried out. The results show that with the increase of damage factor, the rock cutting failure mode changes from tensile failure to brittle failure, accompanied by the propagation of macro cracks, the formation of large debris and a notable decrease in the peak cutting force. The mean cutting force is negatively correlated with the damage factor. Besides this, the instability of cutting force was evaluated by the fluctuation index and the pulse number of unit displacement. It was found that the cutting force was quite stable when the damage factor was 0.3, which improves the reliability of cutting machines. Finally, the cutting energy consumption of rock cutting with different damage factors was analysed. The results reveal that an increase of damage factor can raise the rock cutting efficiency. The aforementioned findings play a significant role in the development of assisted rock-breaking technologies and the design of cutting head layout of mining machinery.

90 Degree Impact Simulation of Steel Wheel

2017 ◽  
Author(s):  
Qian Gao ◽  
Yingchun Shan ◽  
Xiandong Liu ◽  
Er Jiang
Keyword(s):  
Impact Test ◽  
Impact Load ◽  
Reference Method ◽  
Bending Test ◽  
Test Bed ◽  
The Road ◽  
Steel Wheel ◽  
Impact Simulation ◽  
Deformation State ◽  
The Impact

The wheel is one of the important safety components of the vehicle. So, it is required to pass the dynamic rotating bending test, the dynamic radial fatigue test and the impact test. The 90-degree impact test represents the driving performance of a vehicle when the vehicle drives through the road pits, or drives in other harsh conditions. As for the steel wheel, there are no mandatory requirements for the impact test. In recent years, some steel wheel enterprises bring up 90-degree impact test for steel wheels in order to ensure the quality of their products. In this paper, a finite element simulation model of the steel wheel impact test bed under the case of 90-degree was established according to an enterprise’s impact test requirement. The software “ABAQUS” was used to simulate the 90-degree impact test. A wheel / tire overall model was assembled, considering the impacts of tire inflation and the tire preloading process. Then the deformation state of the rim under 90-degree impact load was analyzed to predict whether it could pass the requirements of relevant impact test successfully. The results show that the steel wheel does not meet the requirements of the impact test, which makes it necessary to study the steel wheel’s impact test and optimize the structure of the rim. This paper also provides a reference method for the impact simulation of the steel wheel.

scholarly journals Damage Model and Numerical Experiment of High-Voltage Electro Pulse Boring in Granite

Energies ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 727 ◽  
Author(s):  
Changping Li ◽  
Longchen Duan ◽  
Songcheng Tan ◽  
Victor Chikhotkin ◽  
Wenpeng Fu
Keyword(s):  
Shock Wave ◽  
High Voltage ◽  
Geometric Model ◽  
Damage Model ◽  
Wave Model ◽  
Potential Method ◽  
Rock Breaking ◽  
Particle Flow Code ◽  
Rock Surface ◽  
Rock Breakage

High-voltage electro pulse boring (EPB) has the advantages of high rock-breaking efficiency and good wall quality, and is a new and efficient potential method of rock breaking. The EPB process is defined as random because it is affected by many factors. At present, there is no suitable physical and mathematical model to describe the process and results of rock breakage in EPB, and the conclusions reached regarding rock-breakage mechanisms are not uniform. In this study, a complete damage model of high voltage EPB in granite is established, which includes a shock wave model and a damage model of high voltage EPB in granite. The damage model is based on the Particle Flow Code two-dimensional program. Use of a damage model of EPB accommodates the complete process of high voltage EPB, from discharge to production of a shock wave, and so rock-breaking via electro pulse can be simulated and calculated. The time-varying waveforms of shock waves with different electrical parameters are simulated and calculated on the basis of the model. Different shock wave forms are loaded into the surface and internal rock in the damage geometric model of EPB granite. Then, the breakage process of the rock surface and internally, and the mechanism of rock breakage using EPB are analyzed. This study provides a scientific basis for the quantitative expression and prediction of rock fragmentation in EPB in order to improve the drilling efficiency and reduction of energy loss in the process of EPB.

Effect of Acrylic Foam Film on Impact Reduction

2016 ◽  
Vol 715 ◽  
pp. 107-110
Author(s):  
Kyohei Takeo ◽  
Taichi Nogami ◽  
Tadaharu Adachi ◽  
Ryohei Koretoh ◽  
Hitoshi Tada
Keyword(s):  
Thin Films ◽  
Impact Load ◽  
Testing Machine ◽  
Research Impact ◽  
Foam Films ◽  
Impact Reduction ◽  
Foam Film ◽  
Reduction Effect ◽  
Falling Weight ◽  
The Impact

Recently, Thin Foam Films are Applied to Cushion Materials on Various Instruments, such as Mobile Phones, Tablet Computers, Etc. because of Reducing Load due to Drop Impact or Collision. Testing Methods of the Thin Films must Be Established to Estimate Effect of Thin Films on Reduction of the Impact Load. in this Research, Impact Reduction Effect of the Acrylic Foam Film with a Thickness below 1000μm was Clarified by Developing a Falling Weight Testing Machine. Maximum Value of the Impact Load Decreased Dominantly and the Plateau Region was Longer as the Thickness Increased. the Duration of the Load was Longer for the Thicker Film. Therefore, the Thin Acrylic Foam Films were Found to Be Effective in the Reduction of the Large Impact Load over 20 Kn.

The Effect of the Impactor Diameter and Boundary Conditions on Low Velocity Impact Composites Behaviour

2007 ◽  
Vol 7-8 ◽  
pp. 217-222 ◽  
Author(s):  
Ana M. Amaro ◽  
Paulo N.B. Reis ◽  
A.G. Magalhães ◽  
Marcelo F.S.F. de Moura
Keyword(s):  
Boundary Conditions ◽  
Damage Model ◽  
Testing Machine ◽  
Three Dimensional ◽  
Experimental Tests ◽  
Low Velocity Impact ◽  
Low Velocity ◽  
Velocity Impact ◽  
Impact Energies ◽  
The Impact

The aim of present work is to study the influence of the impactor diameter and boundary conditions on low velocity impact on carbon-fibre-reinforced epoxy laminates. Experimental tests were performed on [04,904]s laminates, using a drop weight-testing machine. Circular plates were tested under low velocity impacts for two diameters of the hemispherical impactor, 12.7 mm and 20 mm, and considering similar impact energies, 2.6 J for the first impactor and 3 J for the second one. Rectangular and square plates were analysed under low velocity impacts with different boundary conditions. The impacted plates were inspected by X-radiography. Numerical simulations were also performed considering interface finite elements compatible with three-dimensional solid elements including a cohesive mixed-mode damage model, which allows to model delamination between layers. The impact tests showed that both the impactor’s diameter and boundary conditions have influence on the delaminated area. Good agreement between experimental and numerical analysis for shape, orientation and size of damage was obtained.

Research on the Rock Breaking by Double Disc Cutter Test-Bed

2013 ◽  
Vol 690-693 ◽  
pp. 2484-2489 ◽  
Author(s):  
Peng Zhou ◽  
Chao Wang ◽  
Wei Xian Gao ◽  
Yu Hou Wu
Keyword(s):  
Maximum Stress ◽  
Tunnel Boring Machine ◽  
Rock Breaking ◽  
Disc Cutter ◽  
Test Bed ◽  
Underground Engineering ◽  
Tunnel Boring ◽  
Disc Cutters ◽  
Optimal Spacing ◽  
Rock Tunnel

Rock tunnel boring machine is one of the main machineries and equipments for underground engineering, and the failure of tool systems is its main failure form. Rock hob test-bed is the only testing equipment for tool failure and wear. In this paper, the breaking rock by the double disc cutter is simulated and four kinds of rocks are selected to test the influece of rock characteristics and spacing between two disc cutters on the rock breaking by the double disc cutter test-bed. The results show that there is different optimal spacing between two disc cutters for different rock; the optimal spacing is inversely proportional to the hardness of the rocks; the maximum stress appears the boundary between the disc cutter and rock.

Laboratory investigation on the mechanical behaviour of Tournemire argillite

2015 ◽  
Vol 52 (3) ◽  
pp. 268-282 ◽  
Author(s):  
H. Abdi ◽  
D. Labrie ◽  
T.S. Nguyen ◽  
J.D. Barnichon ◽  
G. Su ◽  
...  
Keyword(s):  
Mechanical Behaviour ◽  
Mechanical Response ◽  
Damage Model ◽  
Orientation Angle ◽  
Triaxial Tests ◽  
Experimental Program ◽  
Emission Data ◽  
Testing Program ◽  
Bedding Planes ◽  
Rock Specimens

This paper presents the results of a laboratory testing program that was designed to investigate the mechanical behaviour of the Tournemire argillite. Eighty rock samples were obtained from boreholes drilled at different angles in the walls and floor of an existing gallery at the Tournemire Underground Research Laboratory (URL), France. The experimental program consists of the measurement of the physical properties of the argillite and its mechanical response to loading during uniaxial tests, triaxial tests with various confining pressures, unconfined and confined cyclic tests, and Brazilian tests. Since the Tournemire argillite is characterized by the presence of closely spaced bedding planes, the rock specimens were loaded in different directions to bedding planes (i.e., loading orientation angle, θ = 0°, 30°, 45°, 60°, and 90°). Acoustic emission data were also recorded to detect the initiation and propagation of micro-cracks during the uniaxial tests. Most of the tests were performed at the natural moisture content of the rock specimens as delivered to CANMET Laboratories in Ottawa, Canada, where the experiments were conducted. The main objective of the testing program is to identify the mechanical properties of the Tournemire argillite. This paper mainly focuses on the description and interpretation of the test results. The development of an elastoplastic-damage model to describe the mechanical behaviour of the Tournemire argillite is the subject of another paper.

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