scholarly journals Study on the Rock Size Effect of Quasistatic and Dynamic Compression Characteristics

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Jun Zhou ◽  
Xiangrui Meng ◽  
Chongyan Liu ◽  
Zhixi Liu ◽  
Wensong Xu ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Size Effect ◽  
Strain Rate ◽  
Failure Modes ◽  
Rock Strength ◽  
Dynamic Compression ◽  
Testing Machine ◽  
Impact Testing ◽  
Dynamic Compressive Strength ◽  
Quasistatic Loading

To study the size effect of rock under quasistatic and dynamic conditions, the changes in compressive strength with the change in specimen size are measured. Cylindrical granite specimens with length-diameter ratios in the range of 0.5∼1 are used for uniaxial compression tests using an RMT testing machine and an SPHB impact testing machine. Under quasistatic loading, the failure modes of the specimens with different length-diameter ratios are different. The larger the size of the specimen structure is, the greater the probability of defects such as joints and micro cracks is and the smaller the influence of the specimen on the distribution of a three-dimensional stress state is. The rock strength decreases with increasing length-diameter ratio. Using the improved Weibull formula, the size of the specimen is expressed by the volume, and the calculated rock strength of different volumes is similar to the compressive strength from the quasistatic tests. Under dynamic loading, the dynamic compressive strengths of the specimens with different length-diameter ratios are similar, and the failure mode of the specimens is different from that under quasistatic loading. Soon after a crack appears in a specimen, the specimen splits. As the size of the specimens decreases, the fragments size to approach the millimeter scale. By improving the Weibull distribution formula and considering variation in strain rate caused by the size of the specimen, the dynamic compressive strength of rocks of different volumes is calculated by introducing the critical strain rate and related parameters, and the results are similar to the experimental dynamic compressive strength obtained. The improved Weibull formula based on the strength size effect can accurately describe the quasistatic and dynamic compressive strength laws.

Experimental and Numerical Analysis of Qinling Mountain Engineered Rocks during Pulse-Shaped SHPB Test

2015 ◽  
Vol 16 (3-4) ◽  
pp. 165-171
Author(s):  
Shi Liu ◽  
Jinyu Xu
Keyword(s):  
Compressive Strength ◽  
Elastic Modulus ◽  
Strain Rate ◽  
Energy Absorption ◽  
Absorption Rate ◽  
Failure Modes ◽  
Dynamic Compression ◽  
Peak Strain ◽  
Compression Stress ◽  
Dynamic Compressive Strength

AbstractIn order to study the dynamic compression mechanical properties of engineering rock under high strain rate （100~102 S−1）loads, dynamic compression tests of three common engineering rocks (marble, sandstone and granite) taken from the Qinling Mountain are studied subjected to five different kinds of shock air pressure using Φ 100 mm split Hopkinson pressure bar test system improved with purple copper waveform shaper. The dynamic compression stress-strain curves, dynamic compressive strength, peak strain, energy absorption rate and elastic modulus of three rocks variation with strain rate are researched. The dynamic compression failure modes under different strain rates are analyzed. Then the three-dimensional numerical simulations of waveform shaper shaping effects and stress wave propagation in the SHPB tests are carried out to reproduce the test results. The research results show that the dynamic compression stress-strain curves show certain discreteness, and there is an obvious rebound phenomenon after the peak. With the increase in strain rate, the dynamic compressive strength, peak strain and energy absorption rate are all in a certain degree of increase, but the elastic modulus have no obvious change trend. Under the same strain rate, the dynamic compressive strength of granite is greatest while of sandstone is least. With the increase in strain rate, the margin of increase in peak strain and energy absorption rate of granite is greatest while of sandstone is least. The failure modes of the sample experience a developing process from outside to inside with the increase of strain rate.

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

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.

The Effect of Dynamic Compression on the Evolution of Microstructure in Aluminium and its Alloys

2013 ◽  
Vol 58 (4) ◽  
pp. 1097-1103
Author(s):  
B. Leszczyńska-Madet ◽  
M. Richert
Keyword(s):  
Strain Rate ◽  
Dynamic Compression ◽  
Testing Machine ◽  
Shear Bands ◽  
Impact Testing ◽  
Transmission Electron ◽  
The Mean ◽  
Chord Method ◽  
Evolution Of Microstructure ◽  
Falling Weight

Abstract In the work, the microstructure and selected properties of aluminium and its alloys (AlCu4Zr0.5, AlMg5, AlZn6Mg2.5CuZr) deformed with high strain rate were investigated. The cylindrical samples were compressed by a falling - weight-type impact-testing machine at the strain rate ranging from 1.77-6.06x102 s-1 in order to attain true strains between Φ = 0 - 0.62. After compression, the microhardness of the samples was tested and the microstructure was examined by means of both optical (LM) and transmission electron microscopy (TEM). Additionally the misorientation of selected microstructural elements using proprietary KILIN software was determined. The large density of shear bands, bands and microbands was the characteristic feature of the microstructure. The statistical width of the microbands observed in the microstructure was calculated using the mean chord method. The obtained data demonstrate reduction of the microbands width with the increase of deformation. The main object of investigations concerns the microstructure elements refinement affected by dynamic compression.

scholarly journals Dynamic Compressive Properties of Carbon Nanofibers Reinforced Concrete under Impact Load

2021 ◽  
Author(s):  
Wei Xia ◽  
Jinyu Xu ◽  
Liangxue Nie
Keyword(s):  
Compressive Strength ◽  
Elastic Modulus ◽  
Impact Toughness ◽  
Strain Rate ◽  
Carbon Nanofibers ◽  
Impact Load ◽  
Dynamic Compression ◽  
Dynamic Elastic Modulus ◽  
Compressive Properties ◽  
Dynamic Compressive Strength

Abstract To explore the dynamic compressive properties of carbon nanofibers reinforced concrete (CNFC), a 100mm-diameter Split Hopkinson Pressure Bar (SHPB) was used to carry out the impact compression test respectively on the plain concrete samples and the CNFC samples with different fiber volume fractions (respectively, 0.1%, 0.2%, 0.3% and 0.5%). On this basis, the change characteristics of concrete at five different strain rate levels in dynamic compressive strength, dynamic compression deformation, impact toughness and dynamic elastic modulus of concrete were compared and analyzed. The results show that the dynamic compressive strength, dynamic compression deformation and impact toughness of concrete are enhanced by carbon nanofibers to varying degrees. Specifically, when the content of carbon nanofibers is 0.3%, its enhancement effect on dynamic compressive strength is the best; when the content of carbon nanofibers is 0.2%, it helps enhance the dynamic elastic modulus of concrete, but other content can only have the opposite effect. The dynamic compressive strength, impact toughness and dynamic elastic modulus of plain concrete and CNFC gradually increase with the increase of strain rate level, indicating the existence of significant linear relationship; although the dynamic peak strain and ultimate strain increase wholly with the increase of strain rate, there is no obvious linear correlation between them. In addition, the micro test results show that the addition of an appropriate amount of carbon nanofibers help exert the small size effect, strengthen crack resistance and improve the microstructure of the matrix, effectively enhancing the dynamic compressive properties of concrete under impact load.

Effect of Carboxylic CNTs Filling on Mechanical Behaviors of Basalt Fiber/Epoxy Composites

2018 ◽  
Vol 913 ◽  
pp. 529-535
Author(s):  
Zhi Ming Yang ◽  
Jin Xu Liu ◽  
Xin Ya Feng ◽  
Shu Kui Li ◽  
Xin Lei Wang ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Epoxy Matrix ◽  
Dynamic Compression ◽  
Basalt Fiber ◽  
Epoxy Composites ◽  
Mechanism Analysis ◽  
Basalt Fibers ◽  
Pressing Method ◽  
Axial Tensile ◽  
Dynamic Compressive Strength

In order to improve the mechanical properties of basalt fiber/epoxy composites, carboxylic CNTs were filled into the epoxy matrix of basalt fiber/epoxy composites. Firstly, the carboxylic CNTs filled epoxy composites with different carboxylic CNTs content were studied. Quasi-static and dynamic compression results show that when the content of carboxylic CNTs increased from 0wt% to 1wt%, both ultimate quasi-static and dynamic compressive strength of CNTs filled epoxy composites showed increasing tendencies. However when the content of carboxylic CNTs increased from 1 wt% to 1.5 wt% both ultimate quasi-static and dynamic compressive had decreasing tendencies. Base on above results, carboxylic CNTs (1wt%) filled basalt fiber/epoxy composites were fabricated by mould pressing method. Quasi-static and dynamic compression results showed that both ultimate quasi-static and ultimate dynamic compressive strength of carboxylic CNTs filled basalt fiber/epoxy composite were enhanced compared with those of basalt fiber/epoxy composites without CNTs. However, the critical failure strain were all lower than those of basalt fiber/epoxy composites without CNTs. Failure mechanism analysis showed that the carboxylic CNTs was beneficial for forming good interfacial bonding between epoxy matrix and basalt fibers, and the advantage of high axial tensile strength of basalt fibers could be fully utilized, which is responsible for the enhanced ultimate compressive strength of carboxylic CNTs filled basalt fiber/epoxy composites.

Size Effect of Uniaxial Compressive Strength of Limestone

2012 ◽  
Vol 229-231 ◽  
pp. 233-238 ◽  
Author(s):  
Ze Hui Chen ◽  
Chang Wu Liu ◽  
Ji Wei Deng
Keyword(s):  
Compressive Strength ◽  
Elastic Modulus ◽  
Size Effect ◽  
Shear Failure ◽  
Testing Machine ◽  
Peak Strain ◽  
Test Results ◽  
Effect Model ◽  
Splitting Failure ◽  
Uniaxial Compressive Test

Using the MTS testing machine, the uniaxial compressive test of varisized da-qing limestones were undertaken, and the effect of dimensions about compressive strength, peak strain, elastic modulus and destructional forms of rock specimens were studied. It demonstrates that along with the increase of length-diameter ratio, peak strain and compressive strength turn smaller, elastic modulus gradually increases, the destruction of rock samples have a transformation from splitting failure to shear failure. Combined with the test results, Obert L model and Yang Shengqi model, the two size-effect models with extensive applications are analyzed and contrasted. And the conclusion is drawn that Obert L model has a relatively broad applicability, while Yang Shengqi model has a stronger Targeting and higher accuracy. Thus based on the Yang Shengqi model, the size-effect model of da-qing limestone is put forward, and the result indicates that this model corresponds well with the test results, having certain practical value.

Size Effect Analysis during Material Deformation with High Strain Rate

2013 ◽  
Vol 589-590 ◽  
pp. 198-203
Author(s):  
Feng Jiang ◽  
Lan Yan ◽  
Zhong Wei Hu ◽  
Yi Ming(Kevin) Rong
Keyword(s):  
Shear Stress ◽  
Size Effect ◽  
Strain Rate ◽  
Split Hopkinson Pressure Bar ◽  
Failure Strain ◽  
Testing Machine ◽  
Hopkinson Pressure Bar ◽  
Dynamic Impact ◽  
Impact Tests ◽  
Material Deformation

The goal of this study is to analyze the material deformation behavior in the micron level by quasi-static and dynamic impact tests of hat shaped specimen. Three type of specimen with different shear ring thicknesses (800μm, 400μm, 50μm) were designed. The quasi-static and dynamic impact tests were performed by electronic universal testing machine and split Hopkinson pressure bar (SHPB) respectively. During the material deformation in the SHPB test, the value scope of strain is 0 to 9 while the value scope of strain rate is 0.001s-1 to 400000s-1. The size effect phenomenon on shear stress and failure strain with different shear ring thickness was investigated. The shear stress and failure strain of material increases with the decrease of shear ring thickness. And the size effect phenomenon was weakened with the increase of strain rate.

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

Geofluids ◽  
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.

scholarly journals Study on the Dynamic Mechanical Properties of Metamorphic Limestone under Impact Loading

Lithosphere ◽  
2021 ◽  
Vol 2021 (Special 4) ◽  
Author(s):  
Zhiyu Zhang ◽  
Qingyun Qian ◽  
Hao Wang ◽  
Yonghui Huang ◽  
Jianguo Wang ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Energy Dissipation ◽  
Strain Rate ◽  
Failure Modes ◽  
Fractal Theory ◽  
Sudden Change ◽  
Mining Area ◽  
Strain Rates ◽  
Damage And Fracture ◽  
Corner Cracks

Abstract To study the dynamic damage and fracture of metamorphic limestone under explosive load and the stability of the surrounding rock, the stress-strain curve, fracture morphology, and energy dissipation characteristics of metamorphic limestone in the Dahongshan mining area under different strain rates were studied by the Hopkinson pressure bar (SHPB), stress wave analysis, and fractal theory. The experimental results show that the crushing form and degree are significantly affected by the loading strain rate. There are several typical failure modes. When the strain rate is 17.56 s−1, there is no obvious failure except corner cracks. When the strain rate is between 26.92 s−1 and 56.18 s−1, the failure mode of the specimen is axial splitting failure, and when the strain rate is 67.34 s−1, splitting and shearing failure occur. With the increase of the strain rate, the growth rate of the dynamic compressive strength slows down. Compared with static compressive strength, the strength factor increases from 1.15 to 4.19. Also, the fractal dimension shows a gentle increase. When Df is in the range of 1.82~2.24, there is a sudden change in fragmentation when the strain rate is in the range of 34.70 s−1~56.18 s−1. Energy dissipation density increases logarithmically with the strain rate. The results reveal the dynamic breaking and energy consumption laws of metamorphic limestone under impact loads with different strain rates and could provide some reference value for the safe and efficient construction in the Dahongshan mining area and similar engineering projects.

scholarly journals Impact of twisting high-performance polyethylene fibre bundle reinforcements on the mechanical characteristics of high-strength concrete

2019 ◽  
Vol 69 (334) ◽  
pp. 184
Author(s):  
Y. Zhang ◽  
L. Yan ◽  
S. Wang ◽  
M. Xu
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Reinforced Concrete ◽  
Strain Rate ◽  
Uniform Distribution ◽  
Dynamic Compression ◽  
Splitting Tensile Strength ◽  
Fibre Reinforced Concrete ◽  
Compressive Strength Of Concrete ◽  
Concrete Matrix

The quasi-static and dynamic mechanical behaviours of the concrete reinforced by twisting ultra-high molecular weight polyethylene (UHMWPE) fibre bundles with different volume fractions have been investigated. It was indicated that the improved mixing methodology and fibre geometry guaranteed the uniform distribution of fibres in concrete matrix. The UHMWPE fibres significantly enhanced the splitting tensile strength and residual compressive strength of concrete. The discussions on the key property parameters showed that the UHMWPE fibre reinforced concrete behaved tougher than the plain concrete. Owing to the more uniform distribution of fibres and higher bonding strength at fibre/matrix interface, the UHMWPE fibre with improved geometry enhanced the quasi-static splitting tensile strength and compressive strength of concrete more significantly than the other fibres. The dynamic compression tests demonstrated that the UHMWPE fibre reinforced concrete had considerable strain rate dependency. The bonding between fibres and concrete matrix contributed to the strength enhancement under low strain-rate compression.

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