scholarly journals Study on the Damage Evolution Process and Fractal of Quartz-Filled Shale under Thermal-Mechanical Coupling

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Zhonghu Wu ◽  
Huailei Song ◽  
Liping Li ◽  
Zongqing Zhou ◽  
Yujun Zuo ◽  
...  
Keyword(s):  
Fractal Dimension ◽  
Critical Temperature ◽  
Failure Mode ◽  
Damage Evolution ◽  
Damage Mechanics ◽  
Thermal Damage ◽  
Failure Modes ◽  
Factors Affecting ◽  
Mechanical Coupling ◽  
Theory Of Damage

Filling of brittle minerals such as quartz is one of the main factors affecting the initiation and propagation of reservoir fractures in shale fracturing, in order to explore the failure mode and thermal damage characteristics of quartz-filled shale under thermal-mechanical coupling. Combining the theory of damage mechanics and thermoelasticity, RFPA2D-Thermal is used to establish a numerical model that can reflect the damage evolution of shale under thermal-solid coupling, and the compression test under thermal-mechanical coupling is performed. The test results show that during the temperature loading process, there is a temperature critical value between 60°C and 75°C. When the temperature is less than the critical temperature, the test piece unit does not appear obvious damage. When the temperature is greater than the critical temperature, the specimen unit will experience obvious thermal damage, and the higher the temperature, the more serious the cracking. Under the thermal-mechanical coupling of shale, the tensile strength and elastic modulus of shale show a decreasing trend with the increase of temperature. The failure modes of shale under thermal-solid coupling can be roughly divided into three categories: “V”-shaped failure (30°C, 45°C, and 75°C), “M”-shaped failure (60°C), and inverted “λ”-shaped failure (90°C). The larger the fractal dimension, the more complex the failure mode of the specimen. The maximum fractal dimension is 1.262 when the temperature is 60°C, and the corresponding failure mode is the most complex “M” shape. The fractal dimension is between 1.071 and 1.189, and the corresponding failure mode is “V” shape. The fractal dimension is 1.231, and the corresponding failure mode is inverted “λ” shape.

scholarly journals Study on Mesoscopic Damage Evolution Characteristics of Single Joint Sandstone Based on Micro-CT Image and Fractal Theory

2021 ◽  
Vol 2021 ◽  
pp. 1-18
Author(s):  
Hao Liu ◽  
Lulin Zheng ◽  
Yujun Zuo ◽  
Zhonghu Wu ◽  
Wenjibin Sun ◽  
...  
Keyword(s):  
Fractal Dimension ◽  
Failure Mode ◽  
Digital Image ◽  
Damage Evolution ◽  
Failure Modes ◽  
Dimension Theory ◽  
Box Dimension ◽  
Damage Degree ◽  
Evolution Characteristics ◽  
Fracture Damage

The different directions of joints in rock will lead to great differences in damage evolution characteristics. This study utilizes DIP (digital image processing) technology for characterizing the mesostructure of sandstone and combines DIP technology with RFPA2D. The mesoscale fracture mechanics behavior of 7 groups of jointed sandstones with various dip angles was numerically studied, and its reliability was verified through theoretical analysis. According to digital image storage principle and box dimension theory, the box dimension algorithm of rock mesoscale fracture is written in MATLAB, the calculation method of fractal dimension of mesoscale fracture was proposed, and the corresponding relationship between mesoscale fractal dimension and fracture damage degree was established. Studies have shown that compressive strength as well as elastic modulus of sandstone leads to a U-shaped change when joint dip increases. There are a total of six final failure modes of joint samples with different inclination angles. Failure mode and damage degree can be quantified by D (fractal dimension) and ω (mesoscale fracture damage degree), respectively. The larger the ω, the more serious the damage, and the greater the D, the more complex the failure mode. Accumulative AE energy increases exponentially with the increase of loading step, and the growth process can be divided into gentle period, acceleration period, and surge period. The mesoscale fracture damage calculation based on the fractal dimension can be utilized for quantitatively evaluating the spatial distribution characteristics of mesoscale fracture, which provides a new way to study the law of rock damage evolution.

Viscoplastic Constitutive Modeling of Anisotropic Damage Under Nonproportional Loading

2000 ◽  
Vol 123 (4) ◽  
pp. 403-408 ◽  
Author(s):  
C. L. Chow ◽  
X. J. Yang ◽  
Edmund Chu
Keyword(s):  
Constitutive Modeling ◽  
Damage Evolution ◽  
Damage Mechanics ◽  
Evolution Equations ◽  
Forming Limit ◽  
Anisotropic Damage ◽  
Limit Curve ◽  
Forming Limit Curve ◽  
Localized Necking ◽  
Theory Of Damage

Based on the theory of damage mechanics, a viscoplastic constitutive modeling of anisotropic damage for the prediction of forming limit curve (FLC) is developed. The model takes into account the effect of rotation of principal damage coordinates on the deformation and damage behaviors. With the aid of the damage viscoplastic potential, the damage evolution equations are established. Based on a proposed damage criterion for localized necking, the model is employed to predict the FLC of aluminum 6111-T4 sheet alloy. The predicted results agree well with those determined experimentally.

Aging Effect on Corrosion Damage Evolution Behavior of Fuse-Head Used for Electric Explosive Device

2012 ◽  
Vol 166-169 ◽  
pp. 1883-1886
Author(s):  
You Hong Zhang ◽  
Qian Zhang ◽  
Xin Long Chang ◽  
Chun Guo Yue ◽  
Shi Ying Zhang ◽  
...  
Keyword(s):  
Damage Evolution ◽  
Failure Modes ◽  
Experimental Studies ◽  
Corrosion Damage ◽  
Aging Effect ◽  
Factors Affecting ◽  
Temperature And Humidity ◽  
Explosive Device ◽  
Effects Of Temperature ◽  
Evolution Behavior

Degradation of mechanical properties of electric explosive device fuse-head was serious in different temperature and humidity environments. The objective of this study was to examine the effects of temperature and humidity aging on the damage evolution behavior of fuse-head used for electric explosive device. In this paper, the experimental studies were presented to appreciate the influence of humidity and temperature on the corrosion damage and firing of electric explosive device. The damage mechanisms and failure modes were determined through nondestructive evaluation. The explosive broken and corrosion damage on lead induced by temperature and humidity aging were the main factors affecting the firing probability. At last, the evolution rule of corrosion damage in the environment of different relative humidity and temperature was discussed.

scholarly journals Study on Mesoscale Damage Evolution Characteristics of Irregular Sandstone Particles Based on Digital Images and Fractal Theory

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Lujing Zheng ◽  
Lulin Zheng ◽  
Yujun Zuo ◽  
Hao Liu ◽  
Bin Chen ◽  
...  
Keyword(s):  
Fractal Dimension ◽  
Failure Mode ◽  
Damage Evolution ◽  
Fractal Theory ◽  
Rock Breaking ◽  
Rock Breakage ◽  
Damage Degree ◽  
Final Failure ◽  
Fracture Damage ◽  
Breakage Mechanism

To study the mesoscale damage evolution law of irregular sandstone particles, based on RFPA2D and digital image processing technology, a real mesostructure numerical model of irregular sandstone particles is established to simulate the breakage process of particles, the effects of loading conditions and mesoscale heterogeneity on irregular sandstone particle damage are studied, and the calculation method of fractal dimension of irregular rock particles mesoscale fracture is proposed. The results show that the fracture damage degree (ω) and fractal dimension (D) maximum values of the constrained particles are 0.733 and 1.466, respectively, and the unconstrained particles are 0.577 and 1.153, respectively. The final failure mode of constrained particles is more complicated than unconstrained particles, the damage is more serious, and the fracture is more complete. Thus, the larger values of D yield a more complicated final failure mode of the particles. Consequently, with the larger ω, the final damage is more serious, and the breakage effect is comparatively better. The study is of great significance for exploring the laws of rock particle breakage and energy consumption, rock breakage mechanism, and searching for efficient and energy-saving rock-breaking methods.

scholarly journals Statistical Constitutive Model of Thermal Damage for Deep Rock considering Initial Compaction Stage and Residual Strength

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Lingjie Zhu ◽  
Xiaoli Xu ◽  
Xiaojian Cao ◽  
Shaoyong Chen
Keyword(s):  
Constitutive Model ◽  
Residual Strength ◽  
Damage Evolution ◽  
Damage Mechanics ◽  
Thermal Damage ◽  
Peak Stress ◽  
Confining Pressure ◽  
Evolution Rate ◽  
Correction Coefficient ◽  
Initial Compaction

From the theory of damage mechanics, based on the Hoek-Brown strength criterion and Weibull distribution law of rock microelement strength, a statistical constitutive model of rock thermal damage is established by using equivalent strain hypothesis, and the theoretical model is modified by considering the compression coefficient and residual strength correction coefficient. The rationality of the modified model is verified by experimental data. The results show that the stress-strain curves of rock can be divided into four stages: initial compaction, stable damage propagation, damage strengthening expansion, and damage failure according to the characteristics of rock damage evolution. The peak stress of rock increases exponentially with the increase of confining pressure, and the maximum damage evolution rate decreases exponentially with the increase of confining pressure, which indicates that confining pressure delays the development of cumulative damage. The peak stress and maximum damage evolution rate of rock decrease exponentially with the increase of temperature, which accelerates the damage of rock. The initial damage of rock is thermal damage caused by temperature, and the damage value increases with the increase of temperature. The revised theoretical curve reflects the characteristics of rock compaction stage and residual strength and improves the coincidence with the experimental curve. The research results provide a reference for the establishment of thermal damage constitutive model of rock in deep engineering.

scholarly journals Research of Transitional Failure Mode as Damage Evolution in Rock Wall

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Xiao-guang Li ◽  
Changhong Li ◽  
Yuan Li ◽  
Pu-jin Zhang
Keyword(s):  
Rock Mass ◽  
Stress State ◽  
Failure Mode ◽  
Damage Evolution ◽  
Failure Modes ◽  
Surface Instability ◽  
Biaxial Stress ◽  
Strength Analysis ◽  
Loading Test ◽  
Rock Wall

The stress condition of tunnel surrounding rock mass is complex. The stress concentration of in situ brittle rock mass caused by excavation results in localized damage evolution parallel to the free face, which is called surface instability. The rock wall shows the transition characteristics of the failure mode with the distance from the surface to the depth. Low strength surface instability and transition failure modes of the tunnel’s rock wall are common in deep condition but cylindrical specimens cannot simulate stress state of rock wall surface well in conventional rock mechanics tests. This paper conducted the indoor experimental study of the biaxial stress state and studied the surface instability of samples. An indoor test device for the simulation of transitional surface failure of the rock wall was developed. Through a biaxial stress loading test on the rectangular rock sample, the damage process and crack development of rock samples were analyzed, and the law of stress and strain related to the failure mode transition was characterized as well. Based on test results and strength analysis, an explanation of the failure theory and its corresponding model are proposed based on the maximum strain strength theory. Furthermore, this paper concludes that the failure mode of surface instability presents transition feature from brittle to ductile with the increase of distance from the surface to depth.

Reliability Analysis of Structure System Considering Failure Modes of Strength, Fatigue and Buckling

2008 ◽  
Vol 385-387 ◽  
pp. 257-260 ◽  
Author(s):  
Wei Guang An ◽  
Hai An ◽  
Yong Yi Zhang
Keyword(s):  
Failure Mode ◽  
Damage Mechanics ◽  
Failure Modes ◽  
Structural System ◽  
Structural Element ◽  
Structure System ◽  
Residual Structure ◽  
Calculating Method ◽  
Strength Failure ◽  
Buckling Failure

There could be multi-failure modes in the course of working of the structure system including slender bar members. For example, strength failure, fatigue failure and buckling failure, especially sudden buckling failure would bring large disaster to structure. In this paper, according to Fatigue and Damage Mechanics theory, safe margin expression of the different failure mode of structure (static strength, fatigue and buckling) is given firstly, then by analyzing different failure mode of structural element under static and fatigue loads, and failure mode of the calculating element is confirmed by comparing the failure probability value of different failure mode. In the course of searching for significant failure paths, not only is failure mode that stiffness matrix of structure is zero considered, but also buckling failure mode of compressed residual structure is considered too, so that failure analysis is more reasonable. In the end, the reliability calculating method of the structural system is given, and the validity of the method proposed in this paper is explained combining an example.

Damage Analysis of Thermal-Mechanical Coupling on Concrete Member under High Temperature

2013 ◽  
Vol 639-640 ◽  
pp. 1187-1192
Author(s):  
Shui Ping Yin ◽  
Song Hua Tang ◽  
Yong Hong Li ◽  
Chao Chen ◽  
Fang Tian ◽  
...  
Keyword(s):  
High Temperature ◽  
Structural Damage ◽  
Damage Mechanics ◽  
Thermal Damage ◽  
Damage Model ◽  
Damage Analysis ◽  
Concrete Member ◽  
Cumulative Impact ◽  
Mechanical Coupling ◽  
Structural Resistance

The fire has brought great harm to human, so it is of vital significance to establish a scientific method of structural fire resistance design to avoid personnel casualties and economic loss in the destroy or collapse of the structure in fire. The mechanical properties of materials deteriorate at the high temperature of the fire, and the structure can be damaged easily, so the damage cumulative impact must be considered in the structural resistance capability to fire. Damage mechanics is a powerful tool in the study of structural damage and destroy. In the paper, the damage mechanics is introduced into the calculation of resistance capability to fire of concrete structure, and the thermal-damage analysis of concrete member is achieved through the second development on ANSYS platform by using the residual strength thermal-damage model at high temperature.

scholarly journals Study on the Microscale Tensile Properties of Lower Cambrian Niutitang Formation Shale Based on Digital Images

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Huailei Song ◽  
Zhonghu Wu ◽  
Anli Wang ◽  
Wenjibin Sun ◽  
Hao Liu ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Fractal Dimension ◽  
Failure Mode ◽  
Lower Cambrian ◽  
Failure Modes ◽  
Azimuth Angle ◽  
Natural Fracture ◽  
Hydraulic Fractures ◽  
Fracture Rate ◽  
Calcite Veins

Tensile strength is an important parameter that affects the initiation and propagation of shale reservoir fractures during hydraulic fracturing. Shale is often filled with minerals such as calcite. To explore the effect of calcite minerals on the tensile strength and failure mode of shale, in this paper, lower Cambrian shale cores were observed by microslice observations and core X-ray whole-rock mineral diffraction analysis, and 7 groups of numerical direct tensile tests were performed on simulated shale samples with different azimuth angles. The test results show that as the azimuth angle α increases, the tensile strength of the samples gradually decreases, and the fracture rate also shows a decreasing trend. The failure modes can be summarized as root-shaped (0° and 15°), step-shaped (30 and 45°), fishbone-shaped (60°), and river-shaped (75° and 90°) fracturing. The smaller the azimuth angle α, the easier it is for hydraulic fractures to propagate along the direction of the calcite veins and inhibit the formation of fracture networks in the shale matrix. Considering the correlation between the acoustic emission characteristics and failure mode, the fractal dimension is used to reflect the microscopic failure mode of shale. The larger the fractal dimension, the higher the fracture rate is, the more microcracks exist at the edge of the main crack, the more severe the internal damage is, and the more complex the failure mode of the sample is. As the azimuth angle α increases, the fractal dimension shows a decreasing trend, and the crack becomes smoother. This research has important reference value for the study of hydraulic fracture initiation mechanisms and natural fracture propagation.

Viscoplastic Constitutive Modeling of Anisotropic Damage Under Nonproportional Loading

2000 ◽  
Author(s):  
C. L. Chow ◽  
X. J. Yang ◽  
Edmund Chu
Keyword(s):  
Constitutive Modeling ◽  
Damage Evolution ◽  
Damage Mechanics ◽  
Evolution Equations ◽  
Forming Limit ◽  
Anisotropic Damage ◽  
Limit Curve ◽  
Forming Limit Curve ◽  
Localized Necking ◽  
Theory Of Damage

Abstract Based on the theory of damage mechanics, a viscoplastic constitutive modeling of anisotropic damage for the prediction of forming limit curve (FLC) is developed. The model takes into account the effect of rotation of principal damage coordinates on the deformation and damage behaviors. With the aid of the damage viscoplastic potential, the damage evolution equations are established. Based on a proposed damage criterion for localized necking, the model is employed to predict the FLC of aluminum 6111-T4 sheet alloy. The predicted results agree well with those determined experimentally.

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