Dynamic Compression Damage Energy Consumption and Fractal Characteristics of Shale

Studying the relationship between energy consumption and crushed size of shale under different loading conditions is the key to efficient shale cracking. The split Hopkinson pressure bar system was used to study the dynamic mechanical properties of shale under parallel- and vertical-bedding loading, and energy dissipation in the impact tests was calculated. Relationships between the average crushed size of shale fracture products and energy dissipation and between the fractal dimension and dissipated energy were studied using fractal theory. The experimental results showed that the dynamic compressive strength of shale under parallel- and vertical-bedding conditions had an obvious positive correlation with the strain rate. Dissipative energy of the shale samples under loading in both directions increased with the increase of strain rate. The increase of the strain rate enhanced crushing of the sample. The vertical-bedding shale samples had stronger ability to absorb energy and more internal crack propagation. Dissipative energies of the shale samples in the parallel- and vertical-bedding impact tests were positively related to the fractal dimension. The fractal dimension increased with the increase of dissipative energy during sample failure; with further increase in the dissipative energy, its effect on the change of fractal dimension gradually weakened.

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Experimental Study on Dynamic Compression Characteristics of Red Sandstone under Wetting-Drying Cycles

Advances in Civil Engineering ◽

10.1155/2020/6688202 ◽

2020 ◽

Vol 2020 ◽

pp. 1-10

Author(s):

Bin Du ◽

Haibo Bai ◽

Minglei Zhai ◽

Shixin He

Keyword(s):

Compressive Strength ◽

Fractal Dimension ◽

Strain Rate ◽

Split Hopkinson Pressure Bar ◽

Dynamic Compression ◽

Degradation Mechanism ◽

Impact Compression ◽

Red Sandstone ◽

Dynamic Compressive Strength ◽

The Impact

To study the influence of wetting-drying cycles on dynamic mechanical properties of rock masses, the impact compression tests of red sandstone samples were carried out by using a split Hopkinson pressure bar (SHPB) apparatus with a diameter of 50 mm. The results showed that under the same number of wetting-drying cycles, the dynamic compressive strength of red sandstone increased exponentially with the strain rate, and the sensitivity of the strain rate decreased with the increase of wetting-drying cycles. The deterioration effect of wetting-drying cycles was significant, and the dynamic and static compressive strength decreased with the increase of wetting-drying cycles; the higher the strain rate, the stronger the sensitivity to wetting-drying cycles. Besides, the influence of wetting-drying cycles and strain rate was comprehensively studied, and the equation of dynamic compressive strength of red sandstone was obtained. After different wetting-drying cycles, the fractal characteristics of red sandstone dynamic fragmentation were obvious, and the fractal dimension was 2.02–2.80, and the fractal dimension increased logarithmically with the strain rate. Finally, the internal microstructure of red sandstone after different wetting-drying cycles was analyzed, and the degradation mechanism of the rock by the cycles was discussed.

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Breakage Characterization of Magnetite under Impact Loads and Cyclic Impact Loading

Energies ◽

10.3390/en13205459 ◽

2020 ◽

Vol 13 (20) ◽

pp. 5459

Author(s):

Liang Si ◽

Yijun Cao ◽

Guixia Fan

Keyword(s):

Fractal Dimension ◽

Strain Rate ◽

Intergranular Fracture ◽

Split Hopkinson Pressure Bar ◽

Fractal Theory ◽

Fracture Morphology ◽

Impact Loads ◽

Impact Compression ◽

Cyclic Impact ◽

The Impact

A series of impact compression tests were conducted to study the breakage characteristics of magnetite, as well as the impact pressure on its strain rate and dynamic compressive strength. The dynamic mechanical properties and fragmentation size distribution of magnetite under diverse impact loads and cyclic impact were investigated, with fractal theory as a basis and split Hopkinson pressure bar (SHPB). Breakage methods were also employed to analyze the fracture morphology of magnetite. According to the result, the fractal dimension can reflect the distribution of fragments in various sizes. If the strain rate increases, the fractal dimension will be larger, the fragment size will be finer, and the fragmentation degree will be more influential. A micro-analysis of SEM images demonstrates that the fracture morphology is determined by mineral properties. Under low load cyclic impact, intergranular fracture is the main fractography. Besides, the intergranular fracture will be changed to a transgranular one as the impact load increases.

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Experimental Research on Mechanical and Energy Characteristics of Reinforced Rock under Dynamic Loading

Shock and Vibration ◽

10.1155/2019/4356729 ◽

2019 ◽

Vol 2019 ◽

pp. 1-11 ◽

Cited By ~ 3

Author(s):

Xinxi Liu ◽

Yu Li ◽

Fujun Zhao ◽

Yanming Zhou ◽

Weiwei Wang ◽

...

Keyword(s):

Energy Dissipation ◽

Strain Rate ◽

Dynamic Loading ◽

Split Hopkinson Pressure Bar ◽

Dynamic Compression ◽

Surrounding Rock ◽

Absorbed Energy ◽

Energy Characteristics ◽

Deep Mining ◽

The Stability

The properties of anchored surrounding rock may vary considerably under complex geological and stress conditions, especially dynamic loading in deep mining. Therefore, comprehensive study of the reinforced mechanism is required to prevent failures associated with deep mining. In this paper, with sandstone as matrix and steel bar as bolt, the dynamic compression test of reinforced rock was carried out by using a 50 mm rod diameter split Hopkinson pressure bar (SHPB) test device. The mechanical and energy characteristics of reinforced rock under dynamic loading were analyzed. The results show that the dynamic strength of reinforced sample is greater than that of unreinforced sample and increases with the increase of the strain rate. The reflected energy and absorbed energy increase with the increase of incident energy, while the transmitted energy increases slightly. The higher the strain rate, the larger the energy dissipation rate and the higher the degree of fragmentation. It shows that the energy dissipation characteristic reflects the internal damage process to some extent. Compared with the results of unreinforced samples, the reflected energy of reinforced samples significantly increases and the absorbed energy will significantly decrease. It can be seen that the bolt can reduce absorbed energy of surrounding rock, thereby improving the stability of roadway surrounding rock. The results may provide reference for the stability of deep roadway and support design.

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Study on the Fractal Characteristics of the Pomegranate Biotite Schist under Impact Loading

Geofluids ◽

10.1155/2021/1570160 ◽

2021 ◽

Vol 2021 ◽

pp. 1-8

Author(s):

Jianguo Wang ◽

Ting Zuo ◽

Xianglong Li ◽

Zihao Tao ◽

Jun Ma

Keyword(s):

Compressive Strength ◽

Fractal Dimension ◽

Energy Consumption ◽

Energy Dissipation ◽

Strain Rate ◽

Power Relationship ◽

Strain Rates ◽

Biotite Schist ◽

Fractal Characteristics ◽

Dynamic Compressive Strength

In order to study the fractal characteristics of the pomegranate biotite schist under the effect of blasting loads, a one-dimensional SHPB impact test was carried out to test the dynamic compressive strength, damage morphology, fracture energy dissipation density, and other parameters of the rocks under different strain rates; besides, sieve tests were conducted to count the mass fractal characteristics of the crushed masses under different strain rates to calculate the fractal dimension of the crushed rock D . Finally, the relationships between fractal dimension and dynamic compressive strength, crushing characteristics, and energy dissipation characteristics were analysed. The results show that under different impact loads, the strain rate effect of the rock is significant and the dynamic compressive strength increases with the increasing strain rate, and they show a multiplicative power relationship. The higher the strain rate of the rock, the deeper the fragmentation and the higher the fractal dimension, and the fractal dimension and rock crushing energy density are multiplied by a power relationship. By performing the comparative analysis of the pomegranate biotite schist, a reasonable strain rate range of 78.75 s-1~82.51 s-1 and a reasonable crushing energy consumption density range of 0.78 J·cm-3~0.92 J·cm-3 were determined. This research provides a great reference for the analysis of dynamic crushing mechanism, crushing block size distribution, and crushing energy consumption of the roadway surrounding rock.

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SHPB Dynamic Experiment on Silica Fume Concrete

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.631-632.771 ◽

2013 ◽

Vol 631-632 ◽

pp. 771-775 ◽

Cited By ~ 2

Author(s):

Rong Jun Chen ◽

Hong Wei Liu ◽

Rui Zeng

Keyword(s):

Mechanical Properties ◽

Strain Rate ◽

Silica Fume ◽

High Speed ◽

Split Hopkinson Pressure Bar ◽

Dynamic Compression ◽

Impact Resistance ◽

Dynamic Mechanical Properties ◽

Hopkinson Pressure Bar ◽

The Impact

Dynamic mechanical properties of silica fume concrete in a number of strain rate under the conditions of dynamic compression mechanical properties subjected to various strain rates were studied, and gained the stress versus strain curves, details of an experimental investigation using 74 mm-diameter split Hopkinson pressure bar(SHPB) apparatus were presented. The results showed that: The admixture of silica fume concrete impact resistance, especially under the impact of the performance of high-speed has a very important influence, with the impact velocity increased, the strain rate increase, and its impact more obvious.

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Energy Dissipation and Particle Size Distribution of Granite under Different Incident Energies in SHPB Compression Tests

Shock and Vibration ◽

10.1155/2020/8899355 ◽

2020 ◽

Vol 2020 ◽

pp. 1-14

Author(s):

Fengqiang Gong ◽

Hangyu Jia ◽

Zongxian Zhang ◽

Jian Hu ◽

Song Luo

Keyword(s):

Particle Size ◽

Energy Dissipation ◽

Particle Size Distribution ◽

Critical Incident ◽

Incident Energy ◽

Dynamic Compression ◽

Dissipated Energy ◽

Compression Tests ◽

The Impact ◽

Rock Specimens

To investigate energy dissipation and particle size distribution of rock under dynamic loads, a series of dynamic compression tests of granite specimens were conducted using a conventional split-Hopkinson pressure bar (SHPB) device with a high-speed camera. The experimental results show that the dissipated energy increases linearly with an increasing incident energy, following two different inclined paths connected by a critical incident energy, and the linear energy dissipation law in the dynamic compression test has been confirmed. This critical incident energy was found to be 0.29–0.33 MJ/m3. As the incident energy was smaller than the critical incident energy, the rock specimens remained unruptured after the impact. When the incident energy was greater than the critical incident energy, the rock specimens were ruptured or fragmented after the impact. In addition, the experimental results indicate that the dissipated energy and energy consumption ratio of a rock specimen, either unruptured or fragmented, increase with an increasing strain rate. Furthermore, it was found that fragment sizes at each mesh decrease with an increasing incident energy; that is, fragmentation becomes finer as incident energy increases.

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Dynamic Compressive Strength Tests of Corroded SFRC Exposed to Drying–Wetting Cycles with a 37 mm Diameter SHPB

Materials ◽

10.3390/ma14092267 ◽

2021 ◽

Vol 14 (9) ◽

pp. 2267

Author(s):

Hui Chen ◽

Xiangqiang Zhou ◽

Qiang Li ◽

Rui He ◽

Xin Huang

Keyword(s):

Strain Rate ◽

Steel Fiber ◽

Split Hopkinson Pressure Bar ◽

Dynamic Compression ◽

Strain Curve ◽

Fiber Reinforced Concrete ◽

Impact Compression ◽

Dynamic Increase Factor ◽

Compression Performance ◽

The Impact

This study focuses on the dynamic compression performance of corroded steel fiber-reinforced concrete (SFRC) exposed to drying–wetting chloride cycles by a 37 mm diameter split Hopkinson pressure bar (SHPB) system. Three steel fiber contents (0.5%, 1.0%, 2.0%, by volume) were incorporated into concrete, and samples were subjected to drying–wetting cycles for different corrosion durations (30 days, 60 days, 90 days) after 28 days age. The sample damage mode, stress–strain curve and the dynamic compression performance of corroded SFRC were compared with plain concrete. Through the experimental data, strain-rate effect, fiber reinforcement effect and the corrosion duration influence on the impact compression property of SFRC were identified. The dynamic increase factor results of these samples were compared with the existing models in previous published literature. An empirical dynamic increase factor profile characterization model considering fiber content, corrosion duration and strain-rate is proposed.

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Green Preparation, Spheroidal, and Superior Property of Nano-1,3,5,7-Tetranittro-1,3,5,7-Tetrazocane

Journal of Nanomaterials ◽

10.1155/2018/5839037 ◽

2018 ◽

Vol 2018 ◽

pp. 1-8 ◽

Cited By ~ 5

Author(s):

Xinlei Jia ◽

Jingyu Wang ◽

Conghua Hou ◽

Yingxin Tan

Keyword(s):

Activation Energy ◽

Particle Size ◽

Fractal Dimension ◽

Particle Size Distribution ◽

Size Distribution ◽

Fractal Theory ◽

Crystal Form ◽

Decomposition Temperature ◽

Scanning Calorimetry ◽

The Impact

Herein, a green process for preparing nano-HMX, mechanical demulsification shearing (MDS) technology, was developed. Nano-HMX was successfully fabricated via MDS technology without using any chemical reagents, and the fabrication mechanism was proposed. Based on the “fractal theory,” the optimal shearing time for mechanical emulsification was deduced by calculating the fractal dimension of the particle size distribution. The as-prepared nano-HMX was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC). And the impact sensitivities of HMX particles were contrastively investigated. The raw HMX had a lower fractal dimension of 1.9273. The ideal shearing time was 7 h. The resultant nano-HMX possessed a particle size distribution ranging from 203.3 nm to 509.1 nm as compared to raw HMX. Nano-HMX particles were dense spherical, maintaining β-HMX crystal form. In addition, they had much lower impact sensitivity. However, the apparent activation energy as well as thermal decomposition temperature of nano-HMX particles was decreased, attributing to the reduced probability for hotspot generation. Especially when the shearing time was 7 h, the activation energy was markedly decreased.

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Dynamic Characteristics of Deep Dolomite Under One-Dimensional Static and Dynamic Loads

Journal of The Institution of Engineers (India) Series A ◽

10.1007/s40030-019-00424-5 ◽

2019 ◽

Vol 101 (1) ◽

pp. 49-56 ◽

Cited By ~ 1

Author(s):

Jianguo Wang ◽

Yang Liu ◽

Kegang Li

Keyword(s):

Strain Rate ◽

Axial Compression ◽

Split Hopkinson Pressure Bar ◽

Dynamic Strength ◽

Strong Positive Correlation ◽

Hopkinson Pressure Bar ◽

Irreversible Damage ◽

One Dimensional ◽

Rock Structure ◽

The Impact

AbstractThe failure characteristics of rock subjected to impact disturbance under one-dimensional static axial compression are helpful for studying the problems of pillar instability and rock burst in deep, high geostress surrounding rock under blasting disturbances. Improved split Hopkinson pressure bar equipment was used for one-dimensional dynamic–static combined impact tests of deep-seated dolomite specimens under axial compression levels of 0, 12, 24, and 36 MPa. The experimental results demonstrate that the dolomite specimens exhibit strong brittleness. The dynamic strength always maintains a strong positive correlation with the strain rate when the axial compression is fixed; when the strain rate is close, the dynamic elasticity modulus and peak strength of the specimens first increase and then decrease with the increase in axial compression, and the peak value appears at 24 MPa. The impact resistance of specimens can be enhanced when the axial compression is 12 or 24 MPa, but when it increases to 36 MPa, the damage inside the specimen begins to cause damage to the dynamic rock strength. Prior to the rock macroscopic failure, the axial static load changes the rock structure state, and it can store strain energy or cause irreversible damage.

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Seismic Damage Model of Bridge Piers Subjected to Biaxial Loading Considering the Impact of Energy Dissipation

Applied Sciences ◽

10.3390/app9071481 ◽

2019 ◽

Vol 9 (7) ◽

pp. 1481 ◽

Cited By ~ 1

Author(s):

Shangshun Lin ◽

Zhanghua Xia ◽

Jian Xia

Keyword(s):

Energy Dissipation ◽

Structural Damage ◽

Biaxial Loading ◽

Mechanical Performance ◽

Damage Model ◽

Damage Index ◽

Seismic Damage ◽

Bridge Piers ◽

Dissipated Energy ◽

The Impact

The large degradation of the mechanical performance of hollow reinforced concrete (RC) bridge piers subjected to multi-dimensional earthquakes has not been thoroughly assessed. This paper aims to improve the existing seismic damage model to assess the seismic properties of tall, hollow RC piers subjected to pseudo-static, biaxial loading. Cyclic bilateral loading tests on fourteen 1/14-scale pier specimens with different slenderness ratios, axial load ratios, and transverse reinforcement ratios were carried out to investigate the damage propagation and the cumulative dissipated energy with displacement loads. By considering the influence of energy dissipation on structural damage, a new damage model (M-Usami model) was developed to assess the damage characteristics of hollow RC piers. The results present four consecutive damage stages during the loading process: (a) cracking on concrete surface, (b) yielding of longitudinal reinforcements; (c) spalling of concrete, and (d) collapsing of pier after the concrete crushed and the longitudinal bars ruptured due to the flexural failure. The damage level caused by the seismic waves can be reduced by designing specimens with a good seismic energy dissipation capacity. The theoretical damage index values calculated by the M-Usami model agreed well with the experimental observations. The developed M-Usami model can provide insights into the approaches to assessing the seismic damage of hollow RC piers subjected to bilateral seismic excitations.

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