scholarly journals Experimental Investigation of Dynamic Compression Mechanical Properties of Frozen Fine Sandstone

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Jiehao Wu ◽  
Haibo Wang ◽  
Qi Zong ◽  
Ying Xu
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Failure Modes ◽  
Peak Stress ◽  
Freezing Temperature ◽  
Fracture Morphology ◽  
Tensile Failure ◽  
Average Strain ◽  
Average Strain Rate ◽  
The Impact

Aiming at the dynamic mechanical properties of weakly cemented fine sandstone in the rich water-bearing strata in western China under dynamic loading, a 50 mm rod diameter separation Hopkinson pressure bar (SHPB) test was used to study the Paleogene fine sandstone in a coal mine in Ningxia. The system carried out the impact compression tests of −15°C, −20°C, and −30°C and the average strain rate of 28 s−1–83 s−1 and obtained the dynamic compressive strength of the frozen fine sandstone specimens under different test conditions. The strain curve and the fracture morphology were analyzed for the relationship between dynamic peak stress, peak strain, dynamic strength growth coefficient (DIF), and fracture morphology and strain rate. The results show that the peak stress of frozen fine sandstone increases from the decrease of freezing temperature under the same average strain rate. The peak stress of the specimen increases from the increase in the average strain rate of the same freezing temperature. The failure modes of specimen are mainly divided into axial splitting tensile failure and compression crushing failure. To the splitting tensile failure and the compression crushing failure, the main factors determining the two failure modes are the strain rate, while the temperature affects the severity of the impact damage. In the load strain rate and temperature range, the DIF of the frozen fine sandstone is linearly correlated with the strain rate, and the lower the temperature, the slower the growth rate of the DIF.

Research on the Mechanical Properties and Energy Consumption Transfer Law of Cement Tailings Backfill Under Impact Load

2021 ◽  
Vol 13 (5) ◽  
pp. 889-898
Author(s):  
Yong-Ye Mu ◽  
Xiang-Long Li ◽  
Jian-Guo Wang ◽  
Zhi-Gao Leng
Keyword(s):  
Mechanical Properties ◽  
Energy Transfer ◽  
Impact Load ◽  
Peak Stress ◽  
Peak Strain ◽  
Impact Compression ◽  
Average Strain Rate ◽  
Failure Morphology ◽  
The Stability ◽  
The Impact

The cemented tailings backfill (CTB), which plays a significant role in the stability of mine structure, is made of cement, tailings, and water in a certain proportion. When blasting and excavating an underground mine, the CTB will be disturbed by blasting. The impact load of blasting has an impact on the stability of the CTB, which is directly related to the safety of mine construction. The mechanical behaviour of CTB is generally affected by the cement-tailings ratio (C/T) and average strain rate (ASR). Therefore, a series of impact experiments were carried out on three CTB specimens with different C/T using a SHPB. Combined with the experimental results, this account reports studies on the effects of C/T and ASR on the mechanical properties of CTB, and on the energy transfer laws of CTB during impact compression. The research results show that when the ASR is less than 70 s−1, the peak stress and the peak strain have the same trend, and both of them continue to increase with the increase of ASR.When the ASR exceeds 70 s−1, as the ASR increases, the peak stress continues to increase, but the peak strain decreases gradually. Afterwards, the law of energy transfer of the CTB specimen was analyzed. It was found that as the incident energy increased, the energy reflection ratio of the CTB increased. Both the energy transmitted ratio and the energy dissipation ratio decreased. The volumetric energy showed a sharp increase first and then a trend Because of the slowly increasing trend. Finally, according to the failure morphology of the CTB, it is found that the ASR and the C/T together affect the failure of the CTB. The failure model of the CTB is mainly split failure and crush failure.

Experimental Study on Dynamic Mechanical Properties of Amphibolites, Sericite-quartz Schist and Sandstone under Impact Loadings

2012 ◽  
Vol 13 (2) ◽  
pp. 209-217
Author(s):  
Jun-Zhong Liu ◽  
Jin-Yu Xu ◽  
Xiao-Cong Lv ◽  
De-Hui Zhao ◽  
Bing-Lin Leng
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Failure Mode ◽  
Failure Modes ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Mechanical Properties ◽  
Tensile Failure ◽  
Strength Increase ◽  
Dynamic Mechanical ◽  
Rock Samples

Abstract In order to investigate rock dynamic mechanical properties of amphibolites, sericite-quartz schist and sandstone under the different strain rates varying from 30 s -1 to 150 s -1 , the specimens were subjected to axial impact at different projectile speeds by using the split Hopkinson pressure bar (SHPB) of 100 mm in diameter. The optimal experimental size of rock samples is verified by analyzing the stress equilibrium of cylindrical rock samples in different thicknesses. It has studied the mechanic properties of these three rocks which under impact loadings; and analysed the dynamic compressive strength, failure modes, energy dissipation variation with the strain-rate and the strain-rate hardening effect from the perspective of material microstructure. Experimental results show that the dynamic Young's modulus of rock samples increase with strain-rate slightly. The dynamic failure modes of different rock samples are always different. When at a lower strain-rate, the damage of sandstone takes a peeling off the external radial tensile failure mode, but that of amphibolites takes axial splitting mode; when at a higher strain-rate, sandstone takes granular crushing failure mode, and that of amphibolites and of sericite-quartz schist take massive crushing mode. Significant strain-rate effect can be represented by a linear relation between the specific energy absorption and the strain-rate , or between the dynamic strength increase factor η and .

scholarly journals Triaxial Mechanical Properties and Micromechanism of Calcareous Sand Modified by Nanoclay and Cement

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Wei Wang ◽  
Jian Li ◽  
Jun Hu
Keyword(s):  
Mechanical Properties ◽  
Failure Modes ◽  
Peak Stress ◽  
Cement Composite ◽  
Friction Angle ◽  
Stress And Strain ◽  
Calcareous Sand ◽  
Marine Biological ◽  
Different Content ◽  
The Impact

Calcareous sand is developed by the fracture of marine biological skeleton under the impact of seawater. Calcareous sand is not transported in the process of deposition. Therefore, calcareous sand retains the characteristics of marine biological skeleton, low strength, and porous. In order to study the effect of nanoclay and cement on the modification of calcareous sand, a series of tests were carried out on the modified cement calcareous sand (CCS) with different content of nanoclay. In this study, the triaxial mechanical properties and failure modes of nanoclay and cement composite modified calcareous sand (NCCS) were studied through the triaxial UU test. Then, SEM tests were carried out on CCS and NCCS samples, and the micromechanism of nanoclay and cement composite modified Nanhai calcareous sand was analyzed. The results showed that (1) the shear properties of CCS could be improved by adding nanoclay. The optimum admixture ratio of nanoclay was 8%, and its peak stress was 23%-39% higher than that of CCS. (2) The peak stress and strain of NCCS showed a linear correlation. (3) Compared with CCS, the internal friction angle and cohesion of NCCS were increased by 5.2% and 52%, respectively. (4) Nanoclay could improve the compactness and structure of cement calcareous sand, and the macroscopic performance is the improvement of peak stress and cohesion.

Research on the Mechanical Behavior of Styropor Concrete at High Strain Rates

2010 ◽  
Vol 168-170 ◽  
pp. 2086-2091
Author(s):  
Ze Bin Hu ◽  
Jin Yu Xu ◽  
Jie Zhu ◽  
Qiang He ◽  
Gang Li ◽  
...  
Keyword(s):  
Elastic Modulus ◽  
Strain Rate ◽  
Mechanical Behavior ◽  
High Strain ◽  
Dynamic Strength ◽  
Strain Rates ◽  
Average Strain ◽  
High Strain Rates ◽  
Average Strain Rate ◽  
The Impact

Mechanical behavior of Styropor concrete(EPSC) added with various volumetric fractions of EPS subjected to high strain rates were studied by using the Large-Diameter-SHPB. The infection of volumetric fractions and average strain rate to dynamic properties of EPSC were investigated. The experimental results show that under high strain rate condition, the dynamic strength, dynamic strength increase factor(DIF) and limit strain of EPSC are strain rate dependent, the strain rate effect can be expressed by linear approximations, and the relationship between elastic modulus and average strain rate is independent.With the addition of volumetric fractions of EPS, the impact compressive strength and elastic modulus of EPSC declines, and the toughness of EPSC is reinforced.

High strain rate and low temperature effects on the compressive behaviour of concrete

2020 ◽  
pp. 204141962092741
Author(s):  
Thomas J MacLean ◽  
Alan Lloyd
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
High Strain ◽  
Peak Stress ◽  
Image Correlation ◽  
Stress Strain ◽  
Compressive Behaviour ◽  
Average Strain Rate ◽  
Industrial Storage ◽  
Static Conditions

Temperature and strain rate are important factors when considering the mechanical properties of engineering materials, as they can greatly influence the material behaviour. The research presented here is an experimental investigation to determine the effects of low temperatures and high strain rates on the compressive behaviour of concrete. The primary purpose of the research is the development of experimental stress–strain relationships under these conditions, as this is a largely unexplored research topic. Thirty-five 101.6 mm × 203.2 mm concrete cylinders were tested in uniaxial compression at the University of New Brunswick. The specimens were loaded either under static conditions or dynamically with an average strain rate of approximately 1 s−1, while being exposed to temperatures from 20°C to −70°C to simulate extreme climatic temperature and those attainable within industrial storage facilities. The compression strain of the specimens was obtained using digital image correlation. The mechanical properties studied were the compressive strength, strain associated with the peak stress and general stress–strain behaviour due to the increased strain rate and temperature variations.

Effect of discontinuous long polyimide fiber on mechanical properties, fracture morphology, and crystallization behaviors of polyamide-6 matrix composites

2017 ◽  
Vol 31 (2) ◽  
pp. 223-245 ◽  
Author(s):  
Chichi Jiang ◽  
Enlin Han ◽  
Xiaodong Wang ◽  
Dezhen Wu
Keyword(s):  
Mechanical Properties ◽  
Fiber Surface ◽  
Fracture Morphology ◽  
Polyamide 6 ◽  
Tensile Failure ◽  
Matrix Composites ◽  
Absorption Mechanism ◽  
Crystallization Behaviors ◽  
Major Mechanism ◽  
The Impact

This work has conducted an extensive investigation on the effect of discontinuous long polyimide (PI) fiber on the mechanical properties, fracture morphology, and crystallization behaviors of polyamide-6 (PA6) matrix composites. A series of PA6 matrix composites with different contents of PI fiber were prepared through a standard melt-pultrusion process. The resulting composite specimens not only achieved a prominent reinforcement but also obtain a significant improvement in impact toughness. It is highlighted that the composites achieved a remarkable increase in Izod impact strength by a factor of five compared to pure PA6 when 12 wt% of PI fiber was incorporated. Moreover, the tensile strength of the composites reached 143 MPa at a fiber content of 18 wt%. The mechanical properties could be well predicted by the Cox-Krenchel model, but a negative deviation in experimental data was observed at high fiber concentrations due to the decrease of residual fiber length and fiber aggregation. The morphologic observation of fracture surface indicated that fiber pullout was a major mechanism for tensile failure as a result of long PI fiber-reinforcing effectiveness, and it was also the predominant energy absorption mechanism for the impact fracture of composite specimens. The presence of long PI fiber not only enhanced the crystallinity of PA6 matrix but also induced a well-defined transcrystalline layer on the fiber surface due to its high nucleating ability.

scholarly journals Experimental Study on the Mechanical Properties and Compression Size Effect of Recycled Aggregate Concrete

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2323
Author(s):  
Yubing Du ◽  
Zhiqing Zhao ◽  
Qiang Xiao ◽  
Feiting Shi ◽  
Jianming Yang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Size Effect ◽  
Compressive Stress ◽  
Failure Modes ◽  
Recycled Concrete ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Aggregate Concrete ◽  
Substitution Ratio ◽  
The Impact

To explore the basic mechanical properties and size effects of recycled aggregate concrete (RAC) with different substitution ratios of coarse recycled concrete aggregates (CRCAs) to replace natural coarse aggregates (NCA), the failure modes and mechanical parameters of RAC under different loading conditions including compression, splitting tensile resistance and direct shear were compared and analyzed. The conclusions drawn are as follows: the failure mechanisms of concrete with different substitution ratios of CRCAs are similar; with the increase in substitution ratio, the peak compressive stress and peak tensile stress of RAC decrease gradually, the splitting limit displacement decreases, and the splitting tensile modulus slightly increases; with the increase in the concrete cube’s side length, the peak compressive stress of RAC declines gradually, but the integrity after compression is gradually improved; and the increase in the substitution ratio of the recycled aggregate reduces the impact of the size effect on the peak compressive stress of RAC. Furthermore, an influence equation of the coupling effect of the substitution ratio and size effect on the peak compressive stress of RAC was quantitatively established. The research results are of great significance for the engineering application of RAC and the strength selection of RAC structure design.

Experimental investigation and modeling of dynamic thermomechanical behavior of 4-harness satin weave carbon/epoxy composites

2017 ◽  
Vol 31 (9) ◽  
pp. 1181-1203 ◽  
Author(s):  
Xueyao Hu ◽  
Hui Guo ◽  
Weiguo Guo ◽  
Feng Xu ◽  
Longyang Chen ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Composite Laminates ◽  
Failure Modes ◽  
Shear Failure ◽  
Experimental Studies ◽  
Temperature Shift ◽  
Thermomechanical Coupling ◽  
Longitudinal Splitting ◽  
Wide Range

Theoretical and experimental studies on the compressive mechanical behavior of 4-harness satin weave carbon/epoxy composite laminates under in-plane loading are conducted over the temperature range of 298–473 K and the strain rate range of 0.001–1700/s in this article. The stress–strain curves of 4-harness satin weave composites are obtained at different strain rates and temperatures, and key mechanical properties of the material are determined. The deformation mechanism and failure morphology of the samples are observed and analyzed by scanning electron microscope (SEM) micrographs. The results show that the uniaxial compressive mechanical properties of 4-harness satin weave composites are strongly dependent on the temperature but are weakly sensitive to strain rate. The peak stress and elastic modulus of the material have the trend of decrease with the increasing of temperature, and the decreasing trend can be expressed as the functional relationship of temperature shift factor. In addition, SEM observations show that the quasi-static failure mode of 4-harness satin weave composites is shear failure along the diagonal lines of the specimens, while the dynamic failure modes of the material are multiple delaminations and longitudinal splitting, and with the increasing of temperature, its longitudinal splitting is more serious, but the delamination is relatively reduced. A constitutive model with thermomechanical coupling effects is proposed based on the experimental results and the increment theory of elastic–plastic mechanics. The experimental verification and numerical analysis show that the model is shown to be able to predict the finite deformation behavior of 4-harness satin weave composites over a wide range of temperatures.

Tensile behaviors of co-woven-knitted fabric reinforced composites under various strain rates

2011 ◽  
Vol 45 (24) ◽  
pp. 2495-2506 ◽  
Author(s):  
Pibo Ma ◽  
Hong Hu ◽  
Lvtao Zhu ◽  
Baozhong Sun ◽  
Bohong Gu
Keyword(s):  
Strain Rate ◽  
Failure Modes ◽  
Shear Failure ◽  
High Strain ◽  
Tensile Failure ◽  
Knitted Fabric ◽  
Strain Rates ◽  
High Strain Rates ◽  
Textile Composite ◽  
Interface Failure

This article reports the tensile behaviors of a novel kind of 3D textile composite, named as co-woven-knitted fabric (CWKF) reinforced composite, under quasi-static and high strain rates. The tensile tests were conducted along the warp direction (0°), bias direction (45°), and weft direction (90°) at quasi-static strain rate of 0.001/s and high strain rates ranging from 1589/s to 2586/s. The results indicate that the tensile strength, failure strain, tensile stiffness, energy absorption, and resilient energy are strain rate sensitive along all the three directions. The relationships between the mechanical parameters and the strain rate were also analyzed. The fractograph of the CWKF composite demonstrate that the tensile failure modes are matrix shear failure and fibers breakage under the quasi-static testing condition while interface failure and fibers pullout are at high strain rates.

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