scholarly journals Compressive Test Characteristics and Constitutive Relation of Wet Polypropylene Macrofibers Shotcrete

2020 ◽  
Author(s):  
Fenghui LI ◽  
Yunhai Cheng ◽  
Fei Wu ◽  
Chang Su ◽  
Gangwei Li
Keyword(s):  
Mechanical Response ◽  
Average Energy ◽  
Strain Curve ◽  
Peak Stress ◽  
Compression Tests ◽  
Compressive Test ◽  
Response Characteristics ◽  
Test Characteristics ◽  
High Crack ◽  
Supporting Effect

Abstract Shotcrete is often subject to poor ductility and cracking problems, particularly under high stresses. To address these issues, we investigated the feasibility of adding polypropylene macrofibres to shotcrete. To evaluate the supporting effect, we used dry shotcrete, wet shotcrete, and wet polypropylene macrofibre shotcrete as samples. We compared and analysed the mechanical response characteristics thereof in uniaxial compression tests by acoustic emission monitoring. The results showed that the three materials were brittle, but the ductility, residual strength, and bearing capacity of polypropylene macrofibre shotcrete were significantly enhanced. The energy absorption value of plain shotcrete was higher in the cracking stage, while that of polypropylene macrofibre shotcrete was higher in the post-peak stage, which indicated that the polypropylene macrofibre shotcrete had the characteristics of a high crack-initiation strength and toughness. Besides, the energy release from fibre shotcrete occurred after the peak stress rather than near the peak stress. The average energy absorbed by polypropylene macrofibre shotcrete was significantly higher than that in dry shotcrete and wet shotcrete, which suggested that polypropylene macrofibre shotcrete could mitigate the brittle instability of a shotcrete layer. Based on the test data, a constitutive model of damage statistics was established. The comparison between the experimental data and the fitting results could reflect the characteristics of the total stress-strain curve of such shotcrete. The results provide a basis for the optimisation of polypropylene macrofibre shotcrete layers.

scholarly journals Compressive Test Characteristics and Constitutive Relationship of Wet Polypropylene Macrofiber-Reinforced Shotcrete

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Fenghui Li ◽  
Yunhai Cheng ◽  
Fei Wu ◽  
Chang Su ◽  
Gangwei Li
Keyword(s):  
Mechanical Response ◽  
Average Energy ◽  
Strain Curve ◽  
Peak Stress ◽  
Constitutive Relationship ◽  
Compression Tests ◽  
Response Characteristics ◽  
Test Characteristics ◽  
High Crack ◽  
Relationship Of

Shotcrete is often subject to poor ductility and cracking problems, particularly under high stresses. In order to deal with these issues, the feasibility of adding polypropylene macrofibers to shotcrete was verified. To ascertain the supporting effect, dry shotcrete, wet shotcrete, and wet polypropylene macrofiber-reinforced shotcrete (WPMS) were used as samples. Furthermore, the mechanical response characteristics thereof in uniaxial compression tests were compared and analyzed by acoustic emission (AE) monitoring. The results showed that the three materials were brittle, but the ductility, residual strength, and bearing capacity of polypropylene macrofiber-reinforced shotcrete were significantly enhanced. The energy absorption value of plain shotcrete was higher in the cracking stage, while that of polypropylene macrofiber-reinforced shotcrete was greater in the postpeak stage, which showed that the polypropylene macrofiber-reinforced shotcrete had the characteristics of a high crack-initiation strength and toughness. Besides, the energy release from fiber shotcrete occurred after the peak stress rather than near the peak stress. The average energy absorbed by polypropylene macrofiber-reinforced shotcrete was significantly higher than that in dry shotcrete and wet shotcrete, which implied that polypropylene macrofiber-reinforced shotcrete could mitigate the brittle instability of a shotcrete layer. A constitutive model of damage statistics was established based on the test data. The comparison between the experimental data and the fitting results can reflect the characteristics of the total stress-strain curve of such shotcrete. The results provide a basis for the optimization of polypropylene macrofiber-reinforced shotcrete layers.

A First Principles Study of Ultra-Thin (AIO)n Nanorods: Mechanical Behaviour Under Tension and Compression

2005 ◽  
Vol 219 (3) ◽  
pp. 123-130
Author(s):  
X Song ◽  
Q Ge ◽  
S. C. Yen ◽  
H-K Ching
Keyword(s):  
Mechanical Behaviour ◽  
First Principles ◽  
Density Functional ◽  
Mechanical Response ◽  
Minimum Energy ◽  
Strain Curve ◽  
Compression Tests ◽  
The Density Functional Theory ◽  
Tension And Compression ◽  
Energy Configurations

A first principles approach based on the density functional theory (DFT) was used to study the mechanical behaviour of the linear (Al-O) n nanorods with n spanned 1 to 10. The minimum-energy configurations for the nanostructures are first found by fully relaxing the coordinates of the atoms. Virtual tension and compression tests were then conducted by applying a series of tensile/compressive deformations to the relaxed structures and calculating the corresponding forces required to maintain the equilibrium of the deformed nanorods. A force-strain curve is then obtained for all the nanorods from these virtual tests. The mechanical response of the two shortest nanorods is similar to that of the ductile aluminium, but the longer nanorods deform in a similar manner to the brittle aluminium oxide. All the nanorods demonstrate a much higher compressive strength than tensile strength.

scholarly journals Dynamic Behavior and Fatigue Damage Evolution of Sandstone under Uniaxial Cyclic Loading

2020 ◽  
Vol 2020 ◽  
pp. 1-9 ◽  
Author(s):  
Yidan Sun ◽  
Yu Yang ◽  
Min Li
Keyword(s):  
Cyclic Loading ◽  
Fatigue Damage ◽  
Mechanical Response ◽  
Compressive Strain ◽  
Damage Model ◽  
Testing Machine ◽  
Strain Curve ◽  
Peak Stress ◽  
Creep Theory ◽  
Cycle Number

The mechanical response characteristics of sandstone specimens under different stress amplitudes and loading frequencies were tested by a TAW-2000 rock triaxial testing machine. The characteristics of the stress-strain curve and the evolution process of strain damage under cyclic loading are analyzed. Based on creep theory and the disturbance state concept, a theoretical model between the axial compressive strain, axial compressive stress, and cycle number is established. The results show that there exists an upper threshold value of stress in cyclic loading above which the specimen will be damaged. As peak stress increases, the energy loss and irreversible deformation caused by damage gradually increase. When loading to an unstable peak stress under cyclic loading, the fatigue damage of sandstone under cyclic loading undergoes three characteristic stages: the initial stage; the stable stage; and the accelerated failure stage. The parameters of the strain damage model based on the disturbance state concept of sandstone are identified by test data, and the rationality of the model is validated by comparing theoretical values with experimental measurements.

scholarly journals A Stress-Strain Model for Brick Prism under Uniaxial Compression

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Keun-Hyeok Yang ◽  
Yongjei Lee ◽  
Yong-Ha Hwang
Keyword(s):  
Strain Curve ◽  
Peak Stress ◽  
Test Results ◽  
Compression Tests ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Proposed Model ◽  
Relationship Model ◽  
Strain Relationship ◽  
Strain Model

This study proposes a simple and rational stress-strain relationship model applicable to brick masonry under compression. The brick prism compression tests were conducted with different mortar strengths and with constant brick strength. From the observation of the test results, shape of the stress-strain curve is assumed to be parabola. In developing the stress-strain model, the modulus of elasticity, the strain at peak stress, and the strain at 50% of the peak stress on the descending branch were formulated from regression analysis using test data. Numerical and statistical analyses were then performed to derive equations for the key parameter to determine the slopes at the ascending and descending branches of the stress-strain curve shape. The reliability of the proposed model was examined by comparisons with actual stress-strain curves obtained from the tests and the existing model. The proposed model in this study turned out to be more accurate and easier to handle than previous models so that it is expected to contribute towards the mathematical simplicity of analytical modeling.

The Study on BFRP Binding Force of Secondary Compression Tests of Concrete Short Columns

2011 ◽  
Vol 418-420 ◽  
pp. 116-120
Author(s):  
Wei Ha Ma
Keyword(s):  
Initial Stress ◽  
Strain Curve ◽  
Peak Stress ◽  
Stress And Strain ◽  
Compression Tests ◽  
Secondary Stress ◽  
Stress Strain Curve ◽  
Binding Force ◽  
Short Columns ◽  
Strength And Deformation

This article has test researched on the BFRP constraint compression of the concrete short columns secondary stress axial compression , got C20, C25 reinforced concrete specimens of stress-strain curve test, studies show that strengthened specimens of strength and deformation of the increased significantly, and the degree of improve related with the size of initial stress. Through testing the processing and analysis of data, concludes that the calculation formula of peak stress and strain of the strengthening specimens under the secondary stress and can reflect the influence of different condition of initial stress .

scholarly journals Nonlinear Dynamic Constitutive Model of Frozen Sandstone Based on Weibull Distribution

2020 ◽  
Vol 2020 ◽  
pp. 1-10 ◽  
Author(s):  
Lei Wang ◽  
Hongming Su ◽  
Shiguan Chen ◽  
Yue Qin
Keyword(s):  
Elastic Modulus ◽  
Constitutive Model ◽  
Strain Rate ◽  
Split Hopkinson Pressure Bar ◽  
Soft Rock ◽  
Strain Curve ◽  
Peak Stress ◽  
Experimental Results ◽  
Compression Tests ◽  
Hopkinson Pressure Bar

To obtain the dynamic mechanical properties of frozen sandstone at different temperatures (i.e., 20°C, −10°C, −20°C, and −30°C), dynamic uniaxial compression tests of saturated sandstone are conducted using a split-Hopkinson pressure bar. The experimental results demonstrated that the brittleness of the saturated sandstone increased and its plasticity weakened with a decrease in temperature. The peak strength and dynamic elastic modulus of the sandstone were positively correlated with its strain rate. The peak stress was most sensitive to the strain rate at −10°C, and the elastic modulus was most sensitive to the strain rate at −30°C. According to the evident segmentation characteristics of the obtained stress-strain curve, a viscoelastic dynamic constitutive model considering the strain rate effect and temperature effect is developed; this model combines a nonlinear (or linear) body and a Maxwell body in parallel with a damage body. The applicability of the constitutive model is also verified using experimental data. The fitting results were demonstrated to be in good agreement with the experimental results. Furthermore, the fitting results serve as reference for the study of the constitutive model of weakly cemented soft rock and the construction of roadway freezing methods.

scholarly journals Experimental Study on Mechanical Properties of Briquette Coal Samples with Different Moisture Content

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Wang Haidong ◽  
Tao Yang ◽  
Wang Deyue ◽  
Sun Xin ◽  
Gao Jiahui
Keyword(s):  
Mechanical Properties ◽  
Moisture Content ◽  
Coal Seam ◽  
Mechanical Response ◽  
Triaxial Compression ◽  
Strain Curve ◽  
Confining Pressure ◽  
Coal And Gas Outburst ◽  
Compression Tests ◽  
Gas Outburst

Coal seam water injection is an important technical method to prevent and control coal and gas outburst and other disasters. Water can soften coal and change its mechanical properties. In order to study the mechanical properties of coal samples with different moisture content, briquette coal samples with five moistures content (4%, 6%, 8%, 10%, and 12%) were selected to carry out triaxial compression tests under different confining pressures (0.1, 0.2, 0.4, 0.8, and 1.2 MPa). Then, the mechanical response mechanism of the water-bearing briquette coal was analyzed. The results show that the slope of the linear elastic stage of the stress-strain curve gradually decreases with the increase of moisture content. Water-bearing coal exhibits strain strengthening characteristics under high confining pressure, which transforms the water-bearing coal from brittle to ductile state. The peak stress under different moisture content conditions shows a linear relationship with the confining pressure. The internal friction angle decreases linearly with the increase of moisture content. The cohesion varies parabolically with the increase of moisture content and reaches the maximum value when the moisture content is 8%. The coal body with moisture content between 7% and 9% has a high bonding force, which is beneficial to the consolidation of the coal body. Therefore, ensuring a reasonable moisture content of coal through coal seam injection can provide a basis for preventing coal and gas outburst.

Effects of temperature gradient on the granite’s mechanical properties

2021 ◽  
pp. 1-10
Author(s):  
Jinyong Pei ◽  
Huagang He ◽  
Dongtao Hu ◽  
Shanke Lv ◽  
Jing Wang ◽  
...  
Keyword(s):  
High Temperature ◽  
Temperature Gradient ◽  
Strain Curve ◽  
Peak Stress ◽  
Tangent Modulus ◽  
Peak Strain ◽  
Compression Tests ◽  
Different Temperatures ◽  
Effects Of Temperature ◽  
Increasing Temperature

Temperature gradient significantly affects the production of surrounding rock stress in mining engineering. The mechanics and deformation characteristics of the rock will change under the temperature gradient, thereby increasing the probability of accidents in the roadway. This paper conducts uniaxial compression tests on granite at different temperatures from room temperature to 250∘C, and analyzes in detail the changes in the stress-strain curve, peak stress, peak strain and tangent modulus of granite under high temperature and different temperature gradient conditions. The results of this study are as follows: (1) Under high temperature conditions, the granite’s peak stress and tangent elastic modulus increased with temperature from 17 to 100∘C, then decreased from 100∘C to 250∘C, whereas the granite’s peak strain increased steadily with increasing temperature; (2) under temperature gradient, the granite’s peak stress and tangent modulus first decreased and then increased with increasing temperature gradient, while the granite’s peak strain first decreased and then increased at 100∘C, but first increased and then decreased from 150∘C to 250∘C.

Quasi-static Compressive Properties and Behavior of Single-cell Miura Origami Column Fabricated by 3D Printed PLA Material

2020 ◽  
Vol 3 (2) ◽  
pp. 66-73
Author(s):  
Farid Triawan ◽  
Geraldy Cahya Denatra ◽  
Djati Wibowo Djamari
Keyword(s):  
Single Cell ◽  
Peak Stress ◽  
Absorption Capacity ◽  
Compression Tests ◽  
Compressive Properties ◽  
Folding Pattern ◽  
Column Structure ◽  
Thin Walled ◽  
And Behavior ◽  
Initial Peak

The study of a thin-walled column structure has gained much attention due to its potential in many engineering applications, such as the crash box of a car. A thin-walled square column usually exhibits high initial peak force, which may become very dangerous to the driver or passenger. To address this issue, introducing some shape patterns, e.g., origami folding pattern, to the column may become a solution. The present work investigates the compressive properties and behavior of a square box column structure which adopts the Miura origami folding pattern. Several test pieces of single-cell Miura origami column with varying folding angle and layer height are fabricated by a 3D printer. The filament is made of Polylactic Acid (PLA), which is a brittle material. Then, compression tests are carried out to understand its compressive mechanical properties and behavior. The results show that introducing a Miura origami pattern to form a thin-walled square column can dramatically lower down the initial peak stress by 96.82% and, at the same time, increase its ductility, which eventually improves the energy absorption capacity by 61.68% despite the brittle fracture behavior.

Studies on Related ms Magnitude Rate Models in Triangular Wave Unloading Section of Calcium Medium-Fine Sandstone

2010 ◽  
Vol 152-153 ◽  
pp. 164-170
Author(s):  
Jie Liu ◽  
Jian Lin Li ◽  
Ying Xia Li ◽  
Shan Shan Yang ◽  
Ji Fang Zhou ◽  
...  
Keyword(s):  
Mechanical Response ◽  
Strain Curve ◽  
Experimental System ◽  
Constant Term ◽  
Lag Time ◽  
Vertical Force ◽  
Time Segment ◽  
Triangular Wave ◽  
Apparent Modulus ◽  
The Impact

Specific to the improvement in the present research of mechanical response under cyclic loading, this paper, taking the calcareous middle- coarse sandstone as the research subject and the RMT-150C experimental system in which data is recoded by ms magnitude as the platform, develops several related models concerning the unloading rate of triangle waves. The unloading process is divided into lag time segment and non-lag time segment, with criterions and related parameters provided as well. The term apparent elastic modulus is defined. The test data analysis shows that there exist a linear relationship between the apparent modulus and instant vertical force before load damage in non-lag time segment. On the preceding basis, a rate-dependent model of triangular wave un-installation section in non-lag time segment is established. Due to the inability of the loading equipment to accurately input the triangle wave, the average loading rate is amended and a constant term is added into it. The model is proved to be reliable, as the predicted value of the deformation rate and the stress strain curve coincides with measured value. At the same time, the impact of the lag time is pointed out quantitatively and a predication model of lag time segment is set up.

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