scholarly journals Study on Mechanical Features of Brazilian Splitting Fatigue Tests of Salt Rock

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Weichao Wang ◽  
Mengmeng Wang ◽  
Xiliang Liu
Keyword(s):  
Tensile Strength ◽  
Failure Modes ◽  
Splitting Method ◽  
Fatigue Tests ◽  
Test Machine ◽  
Salt Rock ◽  
Tablet Splitting ◽  
Splitting Test ◽  
Fracturing Process ◽  
Brazilian Splitting

The microtest, SEM, was carried out to study the fracture surface of salt rock after the Brazilian splitting test and splitting fatigue test were carried out with a servo-controlled test machine RMT-150B. The results indicate that the deviation of using the tablet splitting method is larger than that of using steel wire splitting method, in Brazilian splitting test of salt rock, when the conventional data processing method is adopted. There are similar deformation features in both the conventional splitting tests and uniaxial compression tests. The stress-strain curves include compaction, elasticity, yielding, and failure stage. Both the vertical deformation and horizontal deformation of splitting fatigue tests under constant average loading can be divided into three stages of “loosening-tightness-loosening.” The failure modes of splitting fatigue tests under the variational average loading are not controlled by the fracturing process curve of the conventional splitting tests. The deformation extent of fatigue tests under variational average loading is even greater than that of conventional splitting test. The tensile strength of salt rock has a relationship with crystallization conditions. Tensile strength of thick crystal salt rock is lower than the bonded strength of fine-grain crystals.

scholarly journals Macro/Microtesting and Damage and Degradation of Sandstones under Dry-Wet Cycles

2016 ◽  
Vol 2016 ◽  
pp. 1-16 ◽  
Author(s):  
Xinrong Liu ◽  
Zijuan Wang ◽  
Yan Fu ◽  
Wen Yuan ◽  
Luli Miao
Keyword(s):  
Tensile Strength ◽  
Cross Sections ◽  
Spiral Ct ◽  
Uniaxial Tensile ◽  
Ct Number ◽  
Uniaxial Tensile Strength ◽  
The Three Gorges ◽  
Splitting Test ◽  
The Mean ◽  
Brazilian Splitting

In terms of the degradation of mechanical parameters of rock mass in the hydrofluctuation belt of a reservoir bank slope arising from rainfall and the reservoir level fluctuation, the moderately weathered sandstone in a side slope of the Three Gorges Reservoir Region is selected as a research object to carry out “drying-saturation-drying” tests for disks with two thicknesses (h=25 mm,h=50 mm) in different cycles; a spiral CT machine, an ultrasonic velocity meter, and a light Schmidt hammer are utilzed to conduct nondestructive testing on dry-wet cycles; through the Brazilian splitting test, the uniaxial tensile strength of “dry” and “saturated” sandstones under different dry-wet cycles is obtained. The research shows that, with the increase of the dry-wet circles (n), the longitudinal wave velocity and the rebound strength of sandstones are linearly decreased withn; the uniaxial tensile strength of sandstones and the mean CT number of cross sections are logarithmically decreased withn; the fitting equation of macro/micromechanical parameters and dry-wet cycles (n) of sandstones is raised, which is provided as a reference basis for the weathering process of sandstones under dry-wet cycles.

scholarly journals Deviation Effect of Coaxiality on the Rock Brazilian Split

2020 ◽  
Vol 2020 ◽  
pp. 1-8 ◽  
Author(s):  
Zenghui Zhao ◽  
Mingzhong Zhang ◽  
Qing Ma ◽  
Baosen Chen
Keyword(s):  
Tensile Strength ◽  
Numerical Calculation ◽  
Stress Distribution ◽  
Rock Fracture ◽  
Splitting Method ◽  
Maximum Tensile Stress ◽  
Analytic Solutions ◽  
Calculation Error ◽  
Splitting Test ◽  
Variable Function

Tension failure is one of the main forms of instability in geotechnical engineering. Aiming at the calculation error caused by the loading direction deviation of the Brazilian disc splitting method, a mechanical model of a disc under chord loading was constructed firstly. Based on the theory of complex variable function, the analytic solutions of stresses in a circular disc were deduced, and the calculation error of the tensile strength under chord loading was characterized by defining the error impact rate. And the stress distribution of a disc and the law of rock fracture under chord loading were detailed analyzed through numerical calculation. Through numerical calculation, the stress distribution of the disc and rock failure law under chordwise loading are discussed in detail. The results show that the stress concentration near the loading point is stronger under the chordwise loading comparing with the radial loading, which makes the disc more vulnerable to produce compression failure near the loading point. The disc exhibits a maximum tensile stress and a minimum compressive stress at the intersection of the loaded string and the horizontal diameter, so that tensile rupture damage is likely to occur here. With the increase of deviation angle, the tensile strength measured by the Brazilian splitting test decreases gradually, and the influence rate of error increases significantly. The proposed analytical solution under chord loading provides theoretical guiding significance for nonradial splitting failure of a disc.

scholarly journals The Effect of Stacking Sequence on Fatigue Behaviour of Hybrid Pineapple Leaf Fibre/Carbon-Fibre-Reinforced Epoxy Composites

Polymers ◽  
2021 ◽  
Vol 13 (22) ◽  
pp. 3936
Author(s):  
Mohd Khairul Rabani Hashim ◽  
Mohd Shukry Abdul Majid ◽  
Mohd Ridzuan Mohd Jamir ◽  
Farizul Hafiz Kasim ◽  
Mohamed Thariq Hameed Sultan ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Failure Modes ◽  
High Stress ◽  
Tensile Load ◽  
Fatigue Behaviour ◽  
Fatigue Tests ◽  
Matrix Cracking ◽  
Stacking Sequence ◽  
Fibre Breakage ◽  
Pull Out

This study examined the fatigue behaviour of pineapple leaf fibre/carbon hybrid laminate composites under various stacking sequences. The vacuum infusion technique was used to fabricate the symmetric quasi-isotropic oriented laminates, in which the stacking was varied. The laminate was tested under static and fatigue tensile load according to ASTM D3039-76 and ASTM D3479-96, respectively. Maximum tensile strength and modulus of 119.34 MPa and 6.86 GPa, respectively, were recorded for the laminate with external PALF ply and internal carbon ply oriented at [± 45°2, 0°/90°2]s (PCCP_45090). The fatigue tests showed that PCCP_45090 and CPPC_09045 (with internal PALF ply and external carbon ply oriented at [0°/90°2, ± 45°2]s) exhibited a higher useful life, especially at the high-stress level of the ultimate tensile strength. The normalised stress against the number of cycles showed that the stacking sequences of different ply orientations affected the fatigue behaviour more than the stacking sequences of the material. The laminate stacking sequence significantly affected the hysteresis energy and stiffness evolution. The scanning electron microscopy images showed that the fatigue failure modes included fibre pull-out, fibre breakage, matrix cracking, debonding, and delamination. The study concluded that PCCP_45090 exhibited an outstanding fatigue performance.

Study on the Influence of Inertia Effect in Dynamic Splitting Test of Concrete

2019 ◽  
Vol 815 ◽  
pp. 182-187
Author(s):  
Zhen Fu Chen ◽  
Pan Liu
Keyword(s):  
Tensile Strength ◽  
Working Conditions ◽  
Loading Rate ◽  
Peak Load ◽  
Test Group ◽  
Control Group ◽  
Test Machine ◽  
Inertia Effect ◽  
Dynamic Tensile Strength ◽  
Splitting Test

A group of concrete spilitting tensile test was carried out by using the drop test machine Studying on the inertial effect on the dynamic tensile strength of concrete under different working conditions. The result show:with the increase of the drop height and quailty, peak load, loading rate of the concrete are increasing gradually.peak load of the test group is slightly higher than control group, The inertia effect has a certain influence on the dynamic tensile strength of concrete.

scholarly journals Analytical and Modelling Study on the Spatial Stress Distribution and Failure Process of Disc Specimen in the Brazilian Splitting Test

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Wei Zhang ◽  
Wei-yao Guo ◽  
Zhi-qi Wang
Keyword(s):  
Tensile Strength ◽  
Stress Distribution ◽  
Failure Process ◽  
Spatial Effect ◽  
Diameter Ratio ◽  
Disc Specimen ◽  
Radial Bearing ◽  
Splitting Test ◽  
Brazilian Splitting ◽  
Spatial Stress

To correctly obtain the spatial stress distribution and failure process of disc specimen in the Brazilian splitting test, an analytical solution of three-dimensional stress is deduced. Then, the effects of height-diameter ratio and clamp radian on the spatial stress distribution and failure process are analyzed and studied combined with numerical modelling. At last, the influence of spatial effect on the tensile strength of disc specimen is discussed. The results show that the cracks firstly generate at the two ends of the specimen in the axial direction and then extend due to the nonuniform distribution of tensile stress. The macrocracks coalescence does not mean the capacity loss of radial bearing. The maximum radial bearing capacity of the disc specimen decreases with the increase of height-diameter ratio due to the spatial effect. The tensile strength obtained by the two-dimensional calculation formula is significantly smaller. Therefore, when the commonly-used height-diameter ratio of 0.5 is used in the Brazilian splitting test, a correction factor k = 1.15 − 1.25 is suggested.

scholarly journals Determining Tensile Strength of Rock by the Direct Tensile, Brazilian Splitting, and Three-Point Bending Methods: A Comparative Study

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Zhengjun Huang ◽  
Ying Zhang ◽  
Yuan Li ◽  
Dong Zhang ◽  
Tong Yang ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Tensile Strength ◽  
Damage Evolution ◽  
Failure Modes ◽  
Bending Test ◽  
Evolution Process ◽  
Internal Crack ◽  
Three Point Bending ◽  
Direct Tensile ◽  
Brazilian Splitting

To accurately obtain the tensile strength of rock and fully understand the evolution process of rock failure is one of the key issues to the research of rock mechanics theories and rock mass engineering applications. Using direct tensile, Brazilian splitting, and three-point bending test methods, we performed indoor and numerical simulation experiments on marble, granite, and diabase and investigated the tensile strength and damage evolution process of several typical rocks in the three different tests. Our experiments demonstrate that (1) the strength is about 10% greater in the Brazilian splitting than in the direct tensile, while the tensile modulus is lower; it is the highest in the three-point bending, which is actually subjected to the bending moment and suggested as one of the indexes to evaluate the tensile strength of rock; (2) the strength in splitting tests is strikingly different, while the strain law is basically similar; the direct tensile test with precut slits is more attainable than that with no-cut slits, with an uninfluenced strength; (3) the failure modes of rocks using different methods are featured by different lithology, while their final modes are basically the same under the same method; (4) PFC and RFPA numerical simulation tests are effective to analyze the internal crack multiplication and acoustic emission changes in the rock as well as the damage evolution process of rock in different tests.

scholarly journals Instability analysis of a filament-wound composite tube subjected to compression/bending

2019 ◽  
Vol 28 ◽  
pp. 096369351987741
Author(s):  
Gyula Szabó ◽  
Károly Váradi
Keyword(s):  
Failure Modes ◽  
Slenderness Ratio ◽  
Equivalent Stress ◽  
Bending Test ◽  
Test Machine ◽  
Fe Model ◽  
Rubber Tube ◽  
Nonlinear Buckling ◽  
Cross Sectional ◽  
Composite Tube

The aim of this study is to investigate the global buckling of a relatively long composite cord–rubber tube subjected to axial compression and its cross-sectional instability due to bending by a macromechanical nonlinear finite element (FE) model (nonlinear buckling analysis). Composite reinforcement layers are modelled as transversely isotropic ones, while elastomer liners are described by a hyperelastic material model that assumes incompressibility. Force–displacement, equivalent strain, equivalent stress results along with oblateness and curvature results for the complete process have been presented. It is justified that bending leads to ovalization of the cross section and results in a loss of the load-carrying capacity of the tube. Strain states in reinforcement layers have been presented, which imply that the probable failure modes of the reinforcement layers are both delamination and yarn-matrix debonding. There is a significant increase in strains due to cross-sectional instability, which proves that the effect of cross-sectional instability on material behaviour of the tube is crucial. A parametric analysis has been performed to investigate the effect of the member slenderness ratio on cross-sectional instability of the composite tube. It shows that Brazier force is inversely proportional to the slenderness ratio. It further shows that higher oblateness parameters occur in case of a lower slenderness ratio and that cross-sectional instability takes place at a lower dimensionless displacement in case of a lower slenderness ratio. FE results have been validated by a compression/bending test experiment conducted on a tensile test machine.

scholarly journals Tensile Mechanical Properties and Failure Modes of a Basalt Fiber/Epoxy Resin Composite Material

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Jingjing He ◽  
Junping Shi ◽  
Xiaoshan Cao ◽  
Yifeng Hu
Keyword(s):  
Tensile Strength ◽  
Composite Material ◽  
Fiber Volume Fraction ◽  
Failure Modes ◽  
Volume Fraction ◽  
Basalt Fiber ◽  
Orientation Angle ◽  
Fiber Volume ◽  
Fiber Clustering ◽  
Fiber Orientation Angle

Uniaxial tensile tests of basalt fiber/epoxy (BF/EP) composite material with four different fiber orientations were conducted under four different fiber volume fractions, and the variations of BF/EP composite material failure modes and tensile mechanical properties were analyzed. The results show that when the fiber volume fraction is constant, the tensile strength, elastic modulus, and limiting strain of BF/EP composite material all decrease with increasing fiber orientation angle. When the fiber orientation angle is constant, the tensile strength, elastic modulus, and limiting strain of BF/EP composite material all increase with increasing fiber volume fraction. A certain degree of fiber clustering appears in the epoxy resin when the basalt fiber volume fraction is >1.2%. The fiber equidistribution coefficient and clustering fiber content were used to characterize the basalt fiber clustering effect. With the increase of fiber volume fraction, the clustering fiber content gradually increased, but the fiber equidistribution coefficient decreased. Meanwhile, based on Tsai theory, a geometric model and a tensile mechanical model of the clustering fiber are established. By considering the fiber clustering effect, the BF/EP composite material tensile strength is calculated, and the calculated values are close to the experimental results.

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