scholarly journals Mechanical properties and progressive failure characteristics of sandstone containing elliptical and square openings subjected to biaxial stress

PLoS ONE ◽  
2021 ◽  
Vol 16 (3) ◽  
pp. e0246815
Author(s):  
Honggang Zhao ◽  
Haitao Sun ◽  
Dongming Zhang ◽  
Chao Liu
Keyword(s):  
Mechanical Properties ◽  
Failure Mode ◽  
Failure Modes ◽  
Biaxial Stress ◽  
Tensile Fracture ◽  
Biaxial Compression ◽  
Lateral Stress ◽  
Variable Theory ◽  
Failure Characteristics ◽  
Elliptical Opening

Two kinds of common tunnel shapes, i.e. elliptical opening and square opening were selected for biaxial compression tests, and the influences of two kinds of opening shapes on the mechanical properties, failure characteristics and failure modes of sandstone were compared and analyzed. The complex variable theory and mapping functions were used to obtain the analytical stress solution around elliptical and square openings. The results show that the stability of the specimen containing an elliptical opening was better than that of the specimen containing a square opening under the same lateral stress. Compared with the elliptical opening, the local damage was formed earlier in the square opening which might be caused by a higher stress concentration around the square opening. The stress distributions around openings were influenced by the opening shape and lateral stress coefficient. The top and bottom of square opening were more prone to tensile fracture, and the distribution range of tensile was larger than that of elliptical opening. When the opening failed, the intensity of square opening failure was weaker than that of elliptical opening. On the basis of the average frequency value and the rise angle value, the failure mode of specimen containing elliptical or square opening was distinguished. It was found that the mixed tension and shear failure dominated the failure of specimens with different opening shapes, and the number of shear cracks in the specimen containing a square opening was greater than that in the specimen containing an elliptical opening. The above method of judging failure mode by acoustic emission signals was well verified by the CT images of damaged specimens.

scholarly journals Experimental Study on the Mechanical Properties and Failure Characteristics of Layered Aeolian Sand Paste-Like Backfill—A Case Study from Shanghe Coal Mine

Minerals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 577
Author(s):  
Xiaoping Shao ◽  
Wuliang Sun ◽  
Xin Li ◽  
Long Wang ◽  
Zhiyu Fang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Failure Mode ◽  
Wave Velocity ◽  
Coal Mine ◽  
Failure Modes ◽  
Shaanxi Province ◽  
Experimental Result ◽  
Failure Characteristics ◽  
Important Direction

Filling mining is an important direction in green coal mining. In the filling site, a layered filling body can be formed due to technological problems. In this paper, we take Shanghe Coal Mine (Shaanxi Province, China) as the background. In order to explore the mechanical properties and failure modes of layered backfill, specimens with different layered proportions (1:1, 1:3, 3:1) were made and studied concerning the aspects of wave velocity, porosity, strength and failure modes. The experimental result demonstrates that with the increase of curing time and fly ash (FA) content, the wave velocity of ASPLB decreases the porosity and the strength increases. In addition, the layered structure has a significant effect on the strength and failure mode of the specimen. Uniaxial compression experiments showed that after 28 days of curing with Ratio III, the strength of layered backfill (LB) was reduced by 14% and the strength of 3:1 LB was increased by 16.7% and 40% compared with 1:1 LB and 1:3 LB, respectively. A digital speckle experiment showed that the failure mode of ASPLB is a vertical fracture without penetration, and the fracture propagation of layered ASPLB is hindered by the stratification. Based on the above research, the scheme that meets the requirements of the Shanghe Coal Mine is determined, and its reliability is verified, providing guidance for scientific stratification and the filling of gob.

scholarly journals Effect of weld nugget size on failure mode and mechanical properties of microscale resistance spot welds on Ti–1Al–1Mn ultrathin foils

2018 ◽  
Vol 10 (7) ◽  
pp. 168781401878528 ◽  
Author(s):  
Feng Chen ◽  
Shiding Sun ◽  
Zhenwu Ma ◽  
GQ Tong ◽  
Xiang Huang
Keyword(s):  
Mechanical Properties ◽  
Failure Mode ◽  
Failure Modes ◽  
Mechanical Performance ◽  
Weld Nugget ◽  
Interfacial Failure ◽  
Spot Welds ◽  
Resistance Spot ◽  
Resistance Spot Welds ◽  
Pullout Failure

We use tensile–shear tests to investigate the failure modes of Ti–1Al–1Mn microscale resistance spot welds and to determine how the failure mode affects the microstructure, microhardness profile, and mechanical performance. Two different failure modes were revealed: interfacial failure mode and pullout failure mode. The welds that fail by pullout failure mode have much better mechanical properties than those that fail by interfacial failure mode. The results show that weld nugget size is also a principal factor that determines the failure mode of microscale resistance spot welds. A minimum weld nugget size exists above which all specimens fail by pullout failure mode. However, the critical weld nugget sizes calculated using the existing recommendations are not consistent with the present experimental results. We propose instead a modified model based on distortion energy theory to ensure pullout failure. Calculating the critical weld nugget size using this model provides results that are consistent with the experimental data to high accuracy.

Failure Modes of a Laminated Composite With Complaint Interlayers

2020 ◽  
Vol 88 (3) ◽  
Author(s):  
M. R. O’Masta ◽  
V. S. Deshpande
Keyword(s):  
Failure Mechanism ◽  
Failure Mode ◽  
Failure Modes ◽  
Volume Fraction ◽  
Flexural Rigidity ◽  
Laminated Composite ◽  
High Volume ◽  
Tensile Fracture ◽  
Reduced Order ◽  
Fe Simulations

Abstract Composites comprising a high-volume fraction of stiff reinforcements within a compliant matrix are commonly found in natural materials. The disparate properties of the constituent materials endow resilience to the composite, and here we report an investigation into some of the mechanisms at play. We report experiments and simulations of a prototype laminated composite system comprising silicon layers separated by polymer interlayers, where the only failure mechanism is the tensile fracture of the brittle silicon. Two failure modes are observed for such composites loaded in three-point bending: failure under the central roller in (i) the top ply (in contact with the roller) or (ii) the bottom ply (free surface). The former mode is benign with the beam retaining load carrying capacity, whereas the latter leads to catastrophic beam failure. Finite element (FE) simulations confirm this transition in failure mode and inform the development of a reduced order model. Good agreement is shown between measurements, FE simulations, and reduced order predictions, capturing the effects of material and geometric properties on the flexural rigidity, first ply failure mode, and failure load. A failure mechanism map for this system is reported that can be used to inform the design of such laminated composites.

scholarly journals Experimental Studies on Cracking and Local Strain Behaviors of Rock-Like Materials with a Single Hole before and after Reinforcement under Biaxial Compression

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Jian Liao ◽  
Yanlin Zhao ◽  
Liming Tang ◽  
Qiang Liu
Keyword(s):  
Mechanical Properties ◽  
Aluminum Alloy ◽  
Failure Modes ◽  
Lateral Pressure ◽  
Peak Strength ◽  
Biaxial Compression ◽  
Tensile Cracks ◽  
Fracture Surfaces ◽  
Single Hole ◽  
Aluminum Alloy Tube

In deep underground engineering, circular roadways are widely used; many rock engineering problems can usually be simplified as mechanical analysis of rock structures with holes. To reveal the influence of intrahole reinforcement on the mechanical properties of rock with a single hole, this paper takes the single-hole rock-like material specimens with different reinforcement conditions as the research object. The RYL600 rock shear rheometer was used to conduct biaxial compression tests and, combined with HD industrial cameras and high-precision strain gauges, to study the effects of different reinforcement thicknesses and different lateral pressure on the mechanical properties of single-hole rock-like materials during the total stress and strain process. The thickness of the reinforced aluminum alloy pipe in the whole test is divided into four types: 0, 1, 1.5, and 2 mm. Under different reinforcement conditions, it is divided into 4 series of 0, 0.5, 1, and 1.5 MPa according to the different lateral pressure. Research shows the following: (1) Under the same lateral pressure, as the reinforcement thickness of the aluminum alloy tube increases, the reinforcement effect of the aluminum alloy tube on the specimen increases, and the strength of the reinforced specimen is increased by 1.42%~33.04% compared with the strength of the unreinforced specimen; under the same reinforced thickness of the aluminum tube, the peak strength of the specimen increases with the increase of lateral pressure, and the peak strength of the specimen with lateral pressure is 3.34%~50.26% higher than that of the specimen without lateral pressure. (2) Increasing the lateral pressure can significantly reduce the primary tensile cracks of the specimen. As the reinforcement thickness increases, the primary tensile cracks and remote cracks of the specimen are significantly reduced, and the failure surface of the specimen gradually tends to the middle of the sample. (3) The failure modes of specimens with holes can be divided into five types: single bevel type I, single bevel type II, single bevel type III, bevel T type, and single part shear type. All of these five failure modes are shear cracks that develop into fracture surfaces, while remote cracks and primary tensile cracks do not develop into fracture surfaces.

scholarly journals Research of Transitional Failure Mode as Damage Evolution in Rock Wall

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Xiao-guang Li ◽  
Changhong Li ◽  
Yuan Li ◽  
Pu-jin Zhang
Keyword(s):  
Rock Mass ◽  
Stress State ◽  
Failure Mode ◽  
Damage Evolution ◽  
Failure Modes ◽  
Surface Instability ◽  
Biaxial Stress ◽  
Strength Analysis ◽  
Loading Test ◽  
Rock Wall

The stress condition of tunnel surrounding rock mass is complex. The stress concentration of in situ brittle rock mass caused by excavation results in localized damage evolution parallel to the free face, which is called surface instability. The rock wall shows the transition characteristics of the failure mode with the distance from the surface to the depth. Low strength surface instability and transition failure modes of the tunnel’s rock wall are common in deep condition but cylindrical specimens cannot simulate stress state of rock wall surface well in conventional rock mechanics tests. This paper conducted the indoor experimental study of the biaxial stress state and studied the surface instability of samples. An indoor test device for the simulation of transitional surface failure of the rock wall was developed. Through a biaxial stress loading test on the rectangular rock sample, the damage process and crack development of rock samples were analyzed, and the law of stress and strain related to the failure mode transition was characterized as well. Based on test results and strength analysis, an explanation of the failure theory and its corresponding model are proposed based on the maximum strain strength theory. Furthermore, this paper concludes that the failure mode of surface instability presents transition feature from brittle to ductile with the increase of distance from the surface to depth.

Failure Characteristics of Rock-Like Material with Multi-Fissures under Uniaxial Compression

2014 ◽  
Vol 711 ◽  
pp. 129-132
Author(s):  
Ri Hong Cao ◽  
Ping Cao ◽  
Pi Hua Wen ◽  
Rui Wen Chen
Keyword(s):  
Mechanical Behavior ◽  
Failure Mode ◽  
Distribution Density ◽  
Failure Modes ◽  
Jointed Rock ◽  
Similar Material ◽  
Failure Characteristics ◽  
Micro Cracks ◽  
Inclination Angles ◽  
Main Factor

Mechanical behavior and failure mode of jointed rock is one of the significant researches in rock mechanics field. In this work, combined with similar material testing and discrete element numerical method(PFC) to investigate the mechanical behavior and failure mode of the rock-like materials with multi-fissures. The numerical analyses agree well with physical experimentation. It is found that, fissures will weaken the strength of the rock-like material, and when the angle of the fissures is about 25°, the strength of the material reaches a minimum value. The weakening effect of fissure on specimen strength would decrease gradually along with the increase of fissure angle. Compared with the effects of fissure angle, the influence of cracks number to the strength is relatively small. The fissure inclination angle was the main factor of the failure modes. With the different fissure inclination angles, the crack tip of Micro-cracks presents different developmental pattern. However, the influence of fissure distribution density on the failure mode mainly reflects at the fracture penetration mode.

scholarly journals Analysis of Rock β-Dynamic Parameters and the Stability of Earthquake Dangerous Rocks Based on PFC

2020 ◽  
Vol 2020 ◽  
pp. 1-17
Author(s):  
Yun Tian ◽  
Lin-feng Wang ◽  
Biao Zeng ◽  
Hong-hua Jin
Keyword(s):  
Mechanical Properties ◽  
Rock Mass ◽  
Failure Mode ◽  
Confining Pressure ◽  
Particle Flow ◽  
Particle Flow Code ◽  
Triaxial Tests ◽  
Tensile Fracture ◽  
Rock Materials ◽  
Synthetic Rock

Mesoparameters of rock materials are the main factors affecting the macromechanical properties of dangerous rock slopes. Based on the principle of particle flow and synthetic rock mass technology (SRM), the influence of mesoparameters on macromechanical properties is investigated by calibrating mesoparameters of rock materials at depth for a rock sequence in Beichuan Qiang Autonomous County, Sichuan Province, China. By combining these parameters with conventional and dynamic cycle triaxial tests, sensitivity analysis of rock β-parameters was completed. As a result, the reliability of mesoparameters in the simulation of dangerous rocks is strengthened, providing a basis to examine the failure mechanism of earthquake dangerous rocks in this region. Results indicate that, in the triaxial test, sandstone failed in tension, and brittleness gradually weakened as confining pressure increased. Mudstone recorded shear failure, and the characteristic value of brittle attenuation showed a V-shaped change with increasing confining pressure. Under cyclic loading, cracks had a degrading effect on the damping ration (β) and the damping coefficient (C) of sandstone. Mudstone recorded relatively low β and low brittleness whilst sandstone had high β and high brittleness. In rock materials, β n is more sensitive than β s in mechanical properties. When the value of the β n -parameter was between 0.2 and 0.3 and the value of the β s -parameter was between 0.2 and 0.6, rock brittleness was more stable, and the reflected macroscopic mechanical properties were the most authentic. By using a deepened mesoparameter trial adjustment method, the failure mode of the Particle Flow Code (PFC) dangerous rock model near provincial highway 205, simulated under conditions for the Wenchuan earthquake, indicated a tensile fracture-horizontal slip failure. The simulated failure mode was consistent with that of real dangerous rocks, with the failure trend being concentrated between the first and the third layer of the rock mass.

scholarly journals KAJIAN EKSPERIMENTAL TENSILE PROPERTIES KOMPOSIT POLIESTER BERPENGUAT SERAT KARBON SEARAH HASIL MANUFAKTUR VACUUM INFUSION SEBAGAI MATERIAL STRUKTUR LSU

2018 ◽  
Vol 14 (1) ◽  
pp. 61
Author(s):  
Kosim Abdurohman ◽  
Aryandi Marta
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Tensile Test ◽  
Failure Mode ◽  
Modulus Of Elasticity ◽  
Failure Modes ◽  
Volume Fraction ◽  
Manufacturing Method ◽  
Vacuum Infusion

Vacuum infusion is a manufacturing method to improve mechanical properties of composite. Before apply this in LSU structure, it should be experimented using tensile test to know mechanical properties of the composite. Tensile test is an experimental to know tensile strength, modulus of elasticity, and failure modes of composite. Experimental process of CFRP composite using unidirectional carbon fiber and polyester matrix was done using vacuum infusion technology, strart from specimens preparation until testing steps. Manufacturing results gave the values of composite density and thickness; mass and volume fraction of fiber and matrix materials. Specimens and testing process are refer to ASTM D3039 tensile test standard for composite matrix polymers. The testing results showed 1011.67 MPa ultimate tensile strength, 59074.96 MPa modulus of elasticity, and SGV (long spliting, gage, various) failure mode . ABSTRAKVacuum infusion merupakan salah satu metode manufaktur yang digunakan untuk meningkatkan sifat mekanik komposit. Untuk mengaplikasikan metode ini dalam pembuatan struktur LAPAN Surveillance UAV (LSU), perlu diketahui terlebih dahulu sifat mekanik dari komposit hasil metode ini secara eksperimen. Salah satu eksperimen yang dilakukan yaitu pengujian tarik untuk mendapatkan tensile strength, modulus elastisitas, dan failure mode yang terjadi pada komposit. Eksperimen dilakukan terhadap komposit CFRP menggunakan material serat karbon searah (UD) 0⁰ dan matriks poliester dibuat dengan metode vacuum infusion mulai dari tahap preparasi sampai tahap pengujian. Dari hasil manufaktur didapat nilai densitas dan ketebalan komposit serta fraksi massa dan fraksi volume material penyusun komposit. Spesimen dan proses pengujian mengikuti standar ASTM D3039 yang merupakan standar pengujian tarik untuk komposit dengan matriks polimer. Hasil pengujian menunjukkan nilai ultimate tensile strength 1011,67 MPa, modulus elastisitas 59074,96 MPa, dan failure mode SGV (Long Spliting, Gage, Various).

scholarly journals Mechanical Analysis of Grouted Sleeve Lapping Connector

2019 ◽  
Vol 9 (22) ◽  
pp. 4867
Author(s):  
Qiong Yu ◽  
Jiaqiu Sun ◽  
Zhiyuan Xu ◽  
Lingzhi Li ◽  
Zhi Zhang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Stress Distribution ◽  
Failure Modes ◽  
High Reliability ◽  
Precast Concrete ◽  
Compressive Strain ◽  
Tensile Load ◽  
Bond Stress ◽  
Tensile Fracture ◽  
Manufacturing Cost

Compared to grouted splice connectors that have been widely used in constructing precast concrete structures, grouted sleeve lapping connectors have the advantages of a large sleeve interior diameter and low manufacturing cost. In this study, 16 grouted sleeve lapping connectors and three grouted splice connectors were tested under an incremental tensile load. The differences in their tensile capacities and failure modes, especially the mechanical properties of the grouted sleeve lapping connectors, were investigated. It was found that the tensile capacities of the grouted sleeve lapping connectors were up to 2.45 times that of the grouted splice connectors when the sleeve inner surfaces were smooth. All of the grouted sleeve lapping connectors failed by a bar tensile fracture or bar-grout slip, whereas the only failure mode of the grouted splice connectors was grout-sleeve failure. The bond stress distribution around the inserted bar in the grouted sleeve lapping connector was similar to the bond stress distribution around a single bar anchored in concrete. The ultimate hoop compressive strain of the sleeve and the corresponding load increase with greater lap length. In addition, an approximate mechanical model with high reliability was put forward to describe the mechanical properties of the grouted sleeve lapping connector.

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 .

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