scholarly journals Numerical tests on thermal cracking characteristics of rocks with different scales

2018 ◽  
Vol 10 (8) ◽  
pp. 168781401879214 ◽  
Author(s):  
Yang Xiao ◽  
Rui Zhao ◽  
Qing-Xiang Huang ◽  
Jun Deng ◽  
Jun-Hui Lu
Keyword(s):  
Acoustic Emission ◽  
Thermal Destruction ◽  
Thermal Damage ◽  
Process Analysis ◽  
Failure Process ◽  
Acoustic Emissions ◽  
Thermal Cracking ◽  
Tensile Failure ◽  
Failure Patterns ◽  
Different Diameters

Realistic failure process analysis, a thermal software simulation, was used to explore the scale effect of thermal cracking of rock under the thermal–mechanical coupling loading. The patterns and characteristics of thermal destruction were analyzed by simulating the thermal cracking of rocks with the same diameter different lengths, the same length but different diameters, and the same size ratio but different sizes (same length/diameter ratio but with different diameters). The acoustic emission and energy changes were also studied during thermal destruction. The results represented that the main forms of thermal cracking are tensile failure and shear failure. The smaller the scale is (length, diameter, and size), the more complex the pattern of thermal damage exhibited as failure patterns of inverted “S” or “V.” With the increasing scale, thermal damage models were simpler. The elastic modulus was determined by the diameter of specimens, and the peak stress was determined by the length of specimens. Overall, as the scale increased, the stress intensity decreased, but the number of acoustic emissions and acoustic emission energy and the corresponding accumulation increased.

Modelling of Thermal Cracking Behaviours of Fiber-Reinforced Composites

2007 ◽  
Vol 334-335 ◽  
pp. 237-240
Author(s):  
Tao Xu ◽  
Shan Yong Wang ◽  
Chun An Tang ◽  
Li Song ◽  
Shi Bin Tang
Keyword(s):  
Process Analysis ◽  
Failure Process ◽  
Damage Model ◽  
Mechanical Damage ◽  
Thermal Cracking ◽  
Model Material ◽  
Thermal Mismatch ◽  
Failure Patterns ◽  
Damage And Fracture ◽  
The Matrix

In this paper, a coupled thermal-mechanical-damage model, Material Failure Process Analysis for Thermo code (abbreviated as MFPA-thermo), was applied to investigate the formation, extension and coalescence of cracks in FRCs, caused by the thermal mismatch of the matrix and the particles under uniform temperature variations. The effects of the thermal mismatch between the matrix and fibers on the stress distribution and crack development were also numerically studied. The influences of the material heterogeneity, the failure patterns of FRCs at varied temperatures are simulated and compared with the experimental results in the present paper. The results show that the mechanisms of thermal damage and fracture of the composite remarkedably depend on the difference between the coefficients of thermal expansion of the fibers and the matrix on a meso-scale. Meanwhile, the simulations indicate that the thermal cracking of the FRCs at uniform varied temperatures is an evolution process from diffused damage, nucleation, and finally linkage of cracks.

Three Dimensional Numerical Approach to Splitting Failure of Rock Discs

2007 ◽  
Vol 353-358 ◽  
pp. 921-924
Author(s):  
Tao Xu ◽  
Tian Hui Ma ◽  
Chun An Tang ◽  
Zheng Zhao Liang
Keyword(s):  
Standardized Test ◽  
Process Analysis ◽  
Failure Process ◽  
Numerical Approach ◽  
Rock Failure ◽  
Test Method ◽  
Tensile Failure ◽  
Numerical Code ◽  
Failure Patterns ◽  
Splitting Failure

The Brazilian splitting tests have been commonly and widely used as a standardized test method on disc or cylinder specimens to measure the indirect tensile strength of rocks in mining engineering and other rock engineering. In this paper, a novel numerical code, 3D Rock Failure Process Analysis code, was applied to implement the splitting tensile failure tests on rock discs. The influences of the heterogeneity on stress distribution in rock are also discussed and the splitting failure patterns of specimens subjected to Brazilian tests are simulated. The simulated splitting results of rock discs were found quite realistic, which indicate that the rock failure analysis method is applicable and practical for the study of rock disc splitting failure.

scholarly journals Research on Failure Characteristics of Concrete Three-Point Bending Beams with Preexisting Cracks in Different Positions Based on Numerical Simulation

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Liuqun Zhao ◽  
Li Zheng ◽  
Hui Qin ◽  
Tiesuo Geng ◽  
Yonggang Tan ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Bearing Capacity ◽  
Failure Modes ◽  
Failure Process ◽  
Engineering Application ◽  
Tensile Failure ◽  
Engineering Structures ◽  
Failure Characteristics ◽  
Three Point Bending ◽  
Wide Range

Concrete three-point bending beams with preexisting cracks are widely used to study the growth process of I-II mixed mode cracks. Studying the failure characteristics of preexisting cracks at different locations on concrete three-point bending beams not only has important scientific significance but also has a wide range of engineering application backgrounds in the safety assessment of engineering structures. In this paper, through several numerical experiments, the influence of preexisting cracks at different positions on the failure characteristics of concrete three-point bending beams is studied, and three typical failure modes are obtained. The failure process of the specimens with three typical failure modes is discussed in detail, and it is pointed out that the crack failure mode is tensile failure. The change trends of bearing capacity, acoustic emission quantity, and acoustic emission energy of three typical failure modes are analyzed. The maximum bearing capacity, the maximum acoustic emission quantity, and energy of three failure modes of concrete three-point bending beams generally show an increasing trend.

Numerical Simulation on Failure Patterns of Rock Discs and Rings Subject to Diametral Line Loads

2004 ◽  
Vol 261-263 ◽  
pp. 1517-1522 ◽  
Author(s):  
Wan Cheng Zhu ◽  
K.T. Chau ◽  
Chun An Tang
Keyword(s):  
Tensile Strength ◽  
Standardized Test ◽  
Process Analysis ◽  
Failure Process ◽  
Brazilian Test ◽  
Rock Failure ◽  
Numerical Code ◽  
Failure Patterns ◽  
Rock Failure Process ◽  
Indirect Tensile

Brazilian test is a standardized test for measuring indirect tensile strength of rock and concrete disc (or cylinder). Similar test called indirect tensile test has also been used for other geomaterials. Although splitting of the disc into two halves is the expected failure mode, other rupture modes had also been observed. More importantly, the splitting tensile strength of rock can vary significantly with the specimen geometry and loading condition. In this study, a numerical code called RFPA2D (abbreviated from Rock Failure Process Analysis) is used to simulate the failure process of disc and ring specimens subject to Brazilian test. The failure patterns and splitting tensile strengths of specimens with different size and loading-strip-width are simulated and compared with existing experimental results. In addition, two distinct failure patterns observed in ring tests have been simulated using RFPA2D and thus this verifies the applicability of RFPA2D in simulating rock failure process under static loads.

scholarly journals Investigation on Pore-Fracture of Coal and Its Influence Mechanism on Tensile Failure Behavior of Coals with Bursting Proneness

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Yutao Li ◽  
Qingwei Guo ◽  
Xunchen Liu ◽  
Yaodong Jiang ◽  
Bo Zhang ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Spatial Distribution ◽  
Failure Mode ◽  
Failure Process ◽  
Elastic Strain Energy ◽  
Tensile Failure ◽  
Failure Behavior ◽  
Secondary Fracture ◽  
Deformation And Failure ◽  
Influence Mechanism

Both computed tomography (CT) and notched semicircular bend (NSCB) tests are performed for coals with high and medium bursting proneness to extract the scientific expression of pore-fracture and its influence mechanism on the tensile failure behavior. The acoustic emission (AE) parameters in the sample during loading and failure are monitored, and the influence mechanism of pore-fracture on tensile failure behavior of coal is analyzed. The result illustrates that the spatial distribution feature of the pore-fracture in coals with high and medium bursting proneness is extremely different. The deformation and failure mode of the coals are affected by many factors, loading mode, notch depth and width, mechanical properties of matrix and minal, spatial distribution feature of pore-fracture, etc. The influence of primary pore-fracture in the coal on the extension and penetration of the secondary fracture could be divided into two types: bifurcation and promotion, which would cause different local damage in the sample and affect the final failure mode. The feature of acoustic emission parameters indicates that the deformation and failure process of a sample under loading could be divided into four stages: compaction stage, elastic deformation stage, displacement plastic growth stage, and post peak failure stage, which is the result of comprehensive action of many factors. The evolution process of secondary fracture is accompanied by the dissipation of elastic strain energy and the intensification of internal damage of coal, which reflects the failure process of coal.

Study of the Effect of Joint Trace Lengths on Failure Strength of Rock

2014 ◽  
Vol 501-504 ◽  
pp. 603-606
Author(s):  
Yun Jie Zhang ◽  
Tao Xu
Keyword(s):  
Compressive Strength ◽  
Process Analysis ◽  
Failure Process ◽  
Strain Curve ◽  
Peak Stress ◽  
Experimental Results ◽  
Peak Strain ◽  
Joint Orientation ◽  
Trace Length ◽  
Failure Patterns

Numerical simulations the different rock sample in the uniaxial compression have been conducted using Rock Failure Process Analysis program (RFPA2D) to evaluate the effects of joint trace lengths on the overall mechanical behaviour of jointed rock masses in this paper. Numerically simulated stress-strain curve, peak stress, peak strain and failure patterns were compared with the corresponding experimental results. We found that for a series of partially-spanning joint geometries with the same joint orientation, the projected area will be proportional to the square of the trace length. Thus, the relationship between compressive strength and partially-spanning joint geometry for the tests carried out to explore the influence of joint trace length may be expressed as a linear correlation between compressive strength and projected area.Numerical simulations agree well with experimental results.

Tensile progressive damage and compressive postbuckling analysis of open-hole laminate composites

2020 ◽  
Vol 39 (17-18) ◽  
pp. 637-653
Author(s):  
Huairong Kang ◽  
Pengfei He ◽  
Cunman Zhang ◽  
Ying Dai ◽  
Zhongde Shan ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Damage Mechanics ◽  
Failure Process ◽  
Tensile Failure ◽  
Progressive Damage ◽  
Laminate Composites ◽  
Crack Distribution ◽  
Failure Patterns ◽  
Fiber Damage ◽  
Open Hole

Laminate composites contain holes as a means of connection in industrial applications. A better understanding of the mechanical properties of open-hole components is necessary. Herein, progressive damage postbuckling analysis models are proposed for investigation of tensile damage and compressive buckling behaviors of open-hole laminate composites. The progressive damage model is based on failure criteria provided by the continuum damage mechanics model; virtual crack closure technology was employed to calculate the energy release rate for crack delamination in compressive postbuckling analysis. The models were utilized to analyze variations in the tensile and compressive mechanical properties, failure process, and buckling evolution of open-hole laminate composites using finite element analysis. The tensile failure patterns and failure processes of plies with different open-hole laminate composite angles were obtained and analyzed. Buckling characteristics, as well as the progression of buckling onset, buckling propagation, crack delamination, unstable delamination, and global buckling, were investigated. The influence of delamination crack length and crack distribution on the buckling properties of open-hole laminate composites are discussed in detail. Additionally, unstable and stable buckling characteristics were examined. The numerical results were in good agreement with theoretical and experimental results; damage initiated at the edge of a hole propagated to two sides with the onset of matrix damage, followed by fiber damage. The fiber damage of a 0°-ply led ultimately to laminate failure. The laminate with a symmetrical crack distribution showed stable buckling, whereas a short, nonsymmetrical distribution of cracks usually led to unstable buckling and delamination.

Numerical Study of Effect of Joint Tip Distance from Sample End on Rock Failure

2014 ◽  
Vol 501-504 ◽  
pp. 244-247
Author(s):  
Yun Jie Zhang ◽  
Cheng Fan
Keyword(s):  
Uniaxial Compression ◽  
Numerical Study ◽  
Process Analysis ◽  
Rock Fracture ◽  
Failure Process ◽  
Strain Curve ◽  
Peak Stress ◽  
Rock Failure ◽  
Peak Strain ◽  
Failure Patterns

In this paper,the mechanical properties of rock experiencing the variation of joint tip distance from sample end under uniaxial compression condition were simulated.Numerical simulation for the different rock sample in the uniaxial compression have been conducted to evaluate the effects of joint tip distance from sample end on the overall mechanical behaviour of jointed rock masses. It was done using the Rock Failure Process Analysis program RFPA2D. Numerically simulated stress-strain curve, peak stress, peak strain and failure patterns were compared with the corresponding physical tests. We found that specimen joint tip distance from sample end corresponding value (distance from the crack tip to the compression surface) linear relationship with the compressive strength values .Numerical simulations agree well with physical results, it is shown that RFPA2D is suitable for the analysis of joint tip distance from sample end effect on rock fracture.

Study on the Thermal Cracking Processes of Composite Subjected to Thermal Loading

2012 ◽  
Vol 256-259 ◽  
pp. 2867-2870
Author(s):  
Shi Bin Tang ◽  
Zheng Zhao Liang ◽  
Ya Fang Zhang
Keyword(s):  
Thermal Expansion ◽  
Thermal Loading ◽  
Coefficient Of Thermal Expansion ◽  
Process Analysis ◽  
Failure Process ◽  
Thermal Cracking ◽  
The Matrix ◽  
Rock Failure Process ◽  
High Or Low Temperature ◽  
Radial Cracks

A numerical method RFPA-T (Thermal Induced Rock Failure Process Analysis) code is used to study the thermal cracking processes of quasi-brittle materials subjected to high or low temperature. The numerical results indicate that thermal stress concentrating along the interface between the matrix and the embedded grains due to their different coefficient of thermal expansion (CTE). The modeling results indicate that θ-crack is generated during temperature increment as the CTE of the embedded grain is smaller than that of the matrix. However, radial-cracks emerged when the temperature decrease. The results obtained from RFPA-T code show a good agreement with experimental evidence of crack patterns caused by thermal expansion mismatch.

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