Cutting force as an index to identify the ductile-brittle failure modes in rock cutting

2021 ◽  
Vol 146 ◽  
pp. 104834
Author(s):  
Xianwei Dai ◽  
Zhongwei Huang ◽  
Huaizhong Shi ◽  
Xiaoguang Wu ◽  
Chao Xiong
Keyword(s):  
Cutting Force ◽  
Brittle Failure ◽  
Failure Modes ◽  
Rock Cutting

scholarly journals Numerical Simulation of Rock Plate Cutting with Three Sides Fixed and One Side Free

2018 ◽  
Vol 2018 ◽  
pp. 1-21 ◽  
Author(s):  
Zhenguo Lu ◽  
Lirong Wan ◽  
Qingliang Zeng ◽  
Xin Zhang ◽  
Kuidong Gao
Keyword(s):  
Numerical Simulation ◽  
Cutting Force ◽  
Cutting Speed ◽  
Rock Cutting ◽  
Numerical Results ◽  
Peak Force ◽  
Cutting Performance ◽  
Conical Pick ◽  
Cutting Method ◽  
Cutting Angle

In order to overcome conical pick wear in the traditional rock cutting method, a new cutting method was proposed on account of increasing free surface of the rock. The mechanical model of rock plate bending under concentrated force was established, and the first fracture position was given. The comparison between experimental and numerical results indicated that the numerical method is effective. A computer code LS-DYNA (3D) was employed to study the cutting performance of a conical pick. To study the rock size influenced on the cutting performance, the numerical simulations with different thickness, width, and height of a rock plate was carried out. The numerical simulation with the different cutting parameters of cutting speed, cutting angle, and cutting position influenced on cutting performance was also carried out. The numerical results indicated that the peak force increased with the increasing thickness of rock plate. With the increasing width and height of the rock plate, the peak force decreased and then became stable. Besides, the peak force decreased with the increasing of cutting position lxp/lx. Moreover, the peak force increased and then decreased with the increasing of cutting angle. The cutting speed has nonsignificant influence on the peak force. The strong exponential relationship was obtained between the peak force and cutting position, thickness, height, and width of the rock plate at a confidence level of 0.95. A binomial relationship was observed between the peak force and cutting angel. The cutting force comparison between traditional rock cutting and rock plate cutting indicated that the new cutting method can effectively reduce peak cutting force.

scholarly journals Evaluation of Seismic Demand for Substandard Reinforced Concrete Structures

2018 ◽  
Vol 12 (1) ◽  
pp. 9-33
Author(s):  
Nicholas Kyriakides ◽  
Ahmad Sohaib ◽  
Kypros Pilakoutas ◽  
Kyriakos Neocleous ◽  
Christis Chrysostomou ◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Seismic Performance ◽  
Performance Prediction ◽  
Brittle Failure ◽  
Failure Modes ◽  
Shaking Table ◽  
Equivalent Linearization ◽  
Diagram Method ◽  
Capacity Curves ◽  
Non Linear

Background: Reinforced Concrete (RC) buildings with no seismic design exhibit degrading behaviour under severe seismic loading due to non-ductile brittle failure modes. The seismic performance of such substandard structures can be predicted using existing capacity demand diagram methods through the idealization of the non-linear capacity curve of the degrading system, and its comparison with a reduced earthquake demand spectrum. Objective: Modern non-linear static methods for derivation of capacity curves incorporate idealization assumptions that are too simplistic and do not apply for sub-standard buildings. The conventional idealisation procedures cannot maintain the true strength degradation behaviour of such structures in the post-peak part, and thus may lead to significant errors in seismic performance prediction especially in the cases of brittle failure modes dominating the response. Method: In order to increase the accuracy of the prediction, an alternative idealisation procedure using equivalent elastic perfectly plastic systems is proposed herein that can be used in conjunction with any capacity demand diagram method. Results: Moreover, the performance of this improved equivalent linearization procedure in predicting the response of an RC frame is assessed herein. Conclusion: This improved idealization procedure has been proven to reduce the error in the seismic performance prediction as compared to seismic shaking table test results [1] and will be further investigated probabilistically herein.

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.

Brittle failure in compression: splitting faulting and brittle-ductile transition

1986 ◽  
Vol 319 (1549) ◽  
pp. 337-374 ◽  
Keyword(s):  
Mathematical Models ◽  
Closed Form ◽  
Brittle Failure ◽  
Failure Modes ◽  
Ductile Failure ◽  
Singular Integral Equations ◽  
Quantitative Model ◽  
Experimental Results ◽  
Laboratory Model ◽  
Brittle Ductile Transition

The micromechanics of brittle failure in compression and the transition from brittle to ductile failure, observed under increasing confining pressures, are examined in the light of existing experimental results and model studies. First, the micromechanics of axial splitting and faulting is briefly reviewed, certain mathematical models recently developed for analysing these failure modes are outlined, and some new, simple closed-form analytic solutions of crack growth in compression and some new quantitative model experimental results are presented. Then, a simple two-dimensional mathematical model is proposed for the analysis of the brittle—ductile transition process, the corresponding elasticity boundary-value problem is formulated in terms of singular integral equations, the solution method is given, and numerical results are obtained and their physical implications are discussed. In addition, a simple closed-form analytic solution is presented and, by comparing its results with those of the exact formulation, it is shown that the analytic estimates are reasonably accurate in the range of the brittle response of the material. Finally, the results of some laboratory model experiments are reported in an effort to support the mathematical models.

scholarly journals Study on the Mechanical Properties of BFRP Tube Confined Concrete Short Columns under Axial Compression

2020 ◽  
Author(s):  
Xindong Ding ◽  
Shuqing Wang ◽  
Yu Liu ◽  
Zepeng Zheng
Keyword(s):  
Axial Compression ◽  
Brittle Failure ◽  
Failure Modes ◽  
Concrete Strength ◽  
Steel Tube ◽  
Confined Concrete ◽  
Test Results ◽  
Compression Tests ◽  
Short Columns ◽  
Square Steel Tube

Axial compression tests were carried out on 6 square steel tube confined concrete short columns and 6 BFRP square pipe confined concrete axial compression tests. The concrete strength grades were C30, C40, and C50. The test results show that the failure modes of steel pipe and BFRP pipe are obviously different, and the BFRP pipe undergoes brittle failure. Compared with the short columns of concrete confined by BFRP pipes, the ultimate bearing capacity of axial compression is increased by -76.46%, -76.01%, and -73.06%, and the ultimate displacements are -79.20%, -80.78%, -71.71%.

scholarly journals Uniaxial Dynamic Compressive Behaviors of Hydraulic Asphalt Concrete under the Coupling Effect between Temperature and Strain Rate

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5348
Author(s):  
Rui Tang ◽  
Zhenpeng Yu ◽  
Guoqing Liu ◽  
Furong Li ◽  
Wenbin Tang
Keyword(s):  
Quantitative Analysis ◽  
Strain Rate ◽  
Temperature Effect ◽  
Asphalt Concrete ◽  
Brittle Failure ◽  
Failure Modes ◽  
Strain Softening ◽  
Coupling Effect ◽  
Peak Stress ◽  
Stress Strain

To investigate the compressive dynamic properties of hydraulic asphalt concrete under various temperatures, four temperatures and four strain rates have been set to perform the uniaxial compression experiments using hydraulic servo machine in this paper. The influence of temperature and strain rate on the failure modes, stress-strain curves and mechanical characteristic parameters of hydraulic asphalt concrete is analyzed and the results reveal that the failure modes and stress-strain curves have significant temperature effect. When the temperature is between −20 °C and 0 °C, the failure mode is dominated by brittle failure of asphalt binder, and hydraulic asphalt concrete shows obvious strain softening. With the addition of temperature, the failure modes of specimens are transferred from brittle failure to ductile failure since the asphalt changes from elastic-brittleness to viscoelasticity. Influenced by temperature effect, the compressive stress-strain curves of hydraulic asphalt concrete show strain hardening while the peak stress of hydraulic asphalt concrete is obviously decreased, and the variation coefficient of peak stress has a power relation with temperature. With successive increases in strain rate, the stress-strain curves of hydraulic asphalt concrete gradually are transferred from strain hardening to strain softening. The peak stress and stiffness modulus of specimens under compression gradually increase, and the dynamic increase factor of peak stress is linearly related with the logarithm value of strain rate after dimensionless treatment. In terms of the quantitative analysis of the experimental data, two relationship models of the coupling effect between temperature and strain rate are proposed. The proposed models have good applicability to the quantitative analysis of the experimental results in the manuscript. This paper offers important insights into the application and development of hydraulic asphalt concrete in hydraulic engineering.

Combined Puncture and Cutting of Soft-Coated Fabrics by a Pointed Blade: Energy, Force and Stress Failure Criteria

2019 ◽  
pp. 152808371987388
Author(s):  
Ennouri Triki ◽  
Chantal Gauvin
Keyword(s):  
Total Energy ◽  
Cutting Force ◽  
Failure Modes ◽  
Stress Component ◽  
Shear Loading ◽  
Critical Force ◽  
Analytical Models ◽  
Protective Gloves ◽  
Coated Fabrics ◽  
Soft Elastomer

Soft elastomer-coated fabrics are widely used in engineering and protective applications. Puncture cutting by sharp-tipped objects is one of the most common failure modes of protective gloves made of coated fabrics. In order to investigate the puncture-cutting process of soft elastomer-coated fabrics, we studied the mechanisms and mechanics of pointed-blade insertion into specimens cut out from four protective gloves. Experimental and analytical analyses showed that total energy and critical puncture-cutting force calculated analytically are both able to predict the puncture-cutting resistance of soft elastomer-coated fabrics measured experimentally. Total energy is obtained from the relationship between the puncture-cutting work and the created fracture area, while critical force is calculated by two analytical models developed for soft elastomeric membranes. The components of the critical puncture-cutting force are predicted analytically and then used to calculate the compressive and shear loading stress components based on the contact surface between the pointed blade tip and material. Since there is a linear relationship between the compressive stress component and shear stress component, a modified linear strength criterion is proposed for puncture cutting of soft elastomer-coated fabrics by a pointed blade. Our stress-based criterion connects the 45° tensile strength (in the 45° direction) and biaxial strengths (in the course direction, 0°, and wale direction, 90°) to both compressive and shear loading stresses. The analytical and experimental results are consistent. This investigation can be used as a guideline to evaluate the puncture cutting of soft elastomer-coated fabrics using an energy-based criterion, critical force-based criterion, or stress-based criterion.

Influence of Roof Rock Thickness on the Failure Probability of Thermally Stable Diamond Composite Rock Cutting Tips

2021 ◽  
Vol 878 ◽  
pp. 98-103
Author(s):  
Yong Sun ◽  
Xing Sheng Li ◽  
Hua Guo
Keyword(s):  
Failure Probability ◽  
Failure Modes ◽  
Roof Rock ◽  
Cutting Temperature ◽  
Rock Cutting ◽  
Estimation Accuracy ◽  
Thermally Stable ◽  
Diamond Composite ◽  
Sudden Failure ◽  
Underground Coal Mines

Thermally Stable Diamond Composite (TSDC) has been used to make rock cutting tips to tackle the challenges of high cutting temperature and high abrasiveness met in hard rock cutting. Various research has been conducted to investigate the failure behaviour and predict the failure risk of the TSDC tips in real rock cutting operations. Based on the scenario of roadway development in underground coal mines, a series studies have been carried out to estimate the probability of TSDC tip sudden failure suffered from randomly occurring excessive bending force, which is one of major failure modes of the TSDC tips. This study aims to improve estimation accuracy of the failure probability by removing the constraint on roof rock thickness that has been adopted in existing research.

Sign in / Sign up

Export Citation Format

Share Document