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1
Qirui, Wang, Zhang Qihu, Yang Liyun, Kong Fuli, Ding Chenxi i Fan Junqi. "Study on Stress Evolution and Crushing Behavior of Jointed Rock Mass under Confining Pressure and Joint Materials". Geofluids 2023 (4.03.2023): 1–15. http://dx.doi.org/10.1155/2023/6954611.
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To study the effects of confining pressure and joint material properties on stress evolution and fracture behavior of jointed rock mass under SHPB impact load, the numerical software LS-DYNA and the indoor SHPB impact system are used to carry out experimental research on intact rock mass and jointed rock mass. The peak stress, reflection and transmission coefficient, and specimen failure state of rock specimens under different schemes are obtained. The effects of confining pressure level and joint material properties on the propagation and attenuation law of explosive stress waves are expounded. The test results show that when the confining pressure is within a specific range, the impact resistance of the limestone specimen can be increased, and the more difficult it is to be destroyed. Moreover, if the confining pressure continues to increase after rising to the peak value, the impact resistance of rock specimens will decline. In that case, the impact resistance of the specimen will decrease—the dynamic strength of jointed rock mass changes with a change in joint material. The dynamic strength of cement jointed rock is the highest, that of gypsum jointed rock is the second, and that of epoxy resin jointed rock is the lowest. The impact damage resistance of the jointed rock has the same law as the above.
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Chen, Qingzhi, Yuanming Liu i Shaoyun Pu. "Strength Characteristics of Nonpenetrating Joint Rock Mass under Different Shear Conditions". Advances in Civil Engineering 2020 (24.08.2020): 1–13. http://dx.doi.org/10.1155/2020/3579725.
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The mechanical property of jointed rock mass is an important factor to be considered in the analysis, evaluation, and design of actual rock engineering. The existence of joints threatens the stability and safety of underground engineering projects built in the rock mass. In order to study the change of mechanical properties and strength characteristics of nonpenetrating jointed rock mass under different test conditions, direct shear tests and triaxial tests were carried out. Direct shear tests under different normal stresses were carried out for nonpenetrating jointed rock mass to prepare specimens for triaxial tests. Then, triaxial tests were carried out to study the change of mechanical properties and strength characteristics of the nonpenetrating jointed rock mass. In the direct shear test part, the greater the normal stress is, the stronger the shear strength and the more serious the shear failure would be. The main conclusions are as follows: (1) the strength of rock mass would increase with the increase of confining pressure for those rock specimens with same degrees of shear after the direct shear test; (2) for rock specimens with different degrees of shear after the direct shear test, if the shearing degree of the rock specimen was greater, the strength of the rock specimen would be lower in the triaxial test; (3) for rock specimens with the same damage degree after direct shear test, the greater the normal stress in direct shear test is, the smaller the peak axial pressure would be in the triaxial test; (4) if the specimen was sheared under higher normal stress in direct shear test, the cohesion of it would be lower and the internal friction angle would be larger. For the specimens under the same normal stress, if the shear failure of one specimen was more serious, the cohesion of it would be smaller and the internal friction angle would be larger.
3
Xiong, L. X., H. Y. Yuan, Y. Zhang, K. F. Zhang i J. B. Li. "Experimental and Numerical Study of the Uniaxial Compressive Stress-Strain Relationship of a Rock Mass with Two Parallel Joints". Archives of Civil Engineering 65, nr 2 (1.06.2019): 67–80. http://dx.doi.org/10.2478/ace-2019-0019.
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AbstractA “rock bridge”, defined as the closest distance between two joints in a rock mass, is an important feature affecting the jointed rock mass strength. Artificial jointed rock specimens with two parallel joint fractures were tested under uniaxial compression and numerical simulations were carried out to study the effects of the inclination of the rock bridge, the dip angle of the joint, rock bridge length, and the length of joints on the strength of the jointed rock mass. Research results show: (1) When the length of the joint fracture, the length of the rock bridge, and the inclination of the rock bridge stay unchanged, the uniaxial compressive strength of the specimen gradually increases as the inclination of the joint fracture increases from 0°to 90°. (2) When the length of the joint fracture, the length of the rock bridge, and the inclination of the joint fracture stay unchanged, the uniaxial compressive strength of the specimen shows variations in trends with the inclination of the rock bridge increasing from 30° to 150° (3). In the case when the joint is angled from the vertical loading direction, when the dip angle of the joint fracture, the inclination of the rock bridge, and the length of the rock bridge stay unchanged, the uniaxial compressive strength of the specimen gradually decreases with an increasing length of joint fracture. When the dip angle of the joint fracture, the inclination of the rock bridge, and the length of the joint fracture stay unchanged, the uniaxial compressive strength of the specimen does not show a clear trend with an increase of the length of the rock bridge.
4
Cao, Rihong, Hua Dai, Rubing Yao, Hang Lin i Kaihui Li. "Failure Behaviour of Jointed Rock Masses with 3D Nonpenetrating Joints under Uniaxial Compression: Insights from Discrete Element Method Modelling". Applied Sciences 12, nr 21 (31.10.2022): 11027. http://dx.doi.org/10.3390/app122111027.
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It is well known that joints or fissures have an important effect on the failure mechanism of natural rocks. Previously, many numerical and experimental papers have been carried out to study the strength anisotropy and failure characteristics of jointed rocks. However, few studies have been carried out on the failure mechanism of nonpersistent jointed rock masses with different persistence, especially for nonpersistent joints in three dimensions. In the present study, the failure characteristics of a 3D nonpersistent jointed rock mass with different inclinations (θ) and persistence (K) are studied by numerical simulation. For the 3D digital elevation model (DEM), the linear parallel bond model (LPBM) and smooth-joint model (S-J) were used to model the rock-like material and joint interface, respectively. The connections between the geometric parameters of joints and peak strength are revealed. For the peak strength, the joint persistence only plays a minor role in specimens with inclinations of 0° and 90°, and its influence on strength is mainly reflected in the specimens with shear failure (θ = 45°, 60°, and 75°). Based on microcrack accumulation and evolution, four typical failure processes (shear failure, split failure, mixed failure, and intact failure) are analysed from the micro perspective. The shear stress evolution process on the 3D nonpersistent joint of the specimen with different inclinations under K1 = 0.42 was monitored by the measurement circle, and it was found that the distribution of shear stress inside the rock bridge is related to the failure mode of the specimen. For the specimens with θ = 0° and 90°, the shear stress had little change, indicating that there is slight shear slip behaviour on the joint surface. When the inclination is 45°, 60°, and 75°, the shear stress changes obviously during loading, indicating that the shear action is strong in this failure mode.
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D, Karunakaran, i Venkatachalapathy VSK. "Investigations of Microstructure and Mechanical Properties of Lap Jointed Dissimilar Metals by Friction Stir Spot Welding Process". Journal of Manufacturing Engineering 18, nr 1 (1.03.2023): 011–19. http://dx.doi.org/10.37255/jme.v18i1pp011-019.
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The joining of different materials is required for industrial application to utilize the hydride structures with attractive advantages such as superior strength to weight ratio, low cost, high tensile strength and less weight of the component. Specifically, Al-Cu composite material is widely used in foil conductors of a transformer, electrical connectors, foil windings in capacitors and tubes in heat exchangers. However, joining or spot welding the Al parts to Cu parts are significant challenge owing to variation in mechanical properties and chemical compositions of joining materials. In this present research work, the friction stir spot welded process (FSSWP) is carried out to join the Al and Cu materials. Further, microstructure and mechanical properties of friction stir spot welded specimens (FSSW) are studied at different tool rotational speeds likely from 1000rpm to 1500rpm. The microstructural study is carried out using scanning electron microscope images at the interface and overall welded region. The tensile strength of both single and double spot-welded specimens is analyzed using a universal tensile test machine. The output of this study states that the optimal tool rotational speed is 1500rpm for both single and double spot-welded specimens. Moreover, the double spot-welded specimen exhibits more tensile with a crack-free spot-welded surface than that of the single spot-welded specimen. The tensile strength double spot-welded specimen has a 6.8% higher strength than that of a single spot-welded specimen. Based on the present study, it is concluded that the double spot-welded specimen can be used for different industrial applications to replace Cu material with this Al-Cu material that gives added advantages to those components.
6
Pan, Jiliang, Xu Wu, Qifeng Guo, Xun Xi i Meifeng Cai. "Uniaxial Experimental Study of the Deformation Behavior and Energy Evolution of Conjugate Jointed Rock Based on AE and DIC Methods". Advances in Civil Engineering 2020 (10.09.2020): 1–16. http://dx.doi.org/10.1155/2020/8850250.
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Conjugate joint is one of the most common joint forms in natural rock mass, which is produced by different tectonic movements. To better understand the preexisting flaws, it is necessary to investigate joint development and its effect on the deformation and strength of the rock. In this study, uniaxial compression tests of granite specimens with different conjugate joints distribution were performed using the GAW-2000 compression-testing machine system. The PCI-2 acoustic emission (AE) testing system was used to monitor the acoustic signal characteristics of the jointed specimens during the entire loading process. At the same time, a 3D digital image correlation (DIC) technique was used to study the evolution of stress field before the peak strength at different loading times. Based on the experimental results, the deformation and strength characteristics, AE parameters, damage evolution processes, and energy accumulation and dissipation properties of the conjugate jointed specimens were analyzed. It is considered that these changes were closely related to the angle between the primary and secondary joints. The results show that the AE counts can be used to characterize the damage and failure of the specimen during uniaxial compression. The local stress field evolution process obtained by the DIC can be used to analyze the crack initiation and propagation in the specimen. As the included angle increases from 0° to 90°, the elastic modulus first decreases and then increases, and the accumulative AE counts of the peak first increase and then decrease, while the peak strength does not change distinctly. The cumulative AE counts of the specimen with an included angle of 45° rise in a ladder-like manner, and the granite retains a certain degree of brittle failure characteristics under the axial loading. The total energy, elastic energy, and dissipation energy of the jointed specimens under uniaxial compression failure were significantly reduced. These findings can be regarded as a reference for future studies on the failure mechanism of granite with conjugate joints.
7
Ping, Yang, i Shu Chen Li. "Triaxial Compression Experimental Study on Post-Peak Deformation Characteristics of Rock Masses with Persistent Joints". Advanced Materials Research 1030-1032 (wrzesień 2014): 1074–77. http://dx.doi.org/10.4028/www.scientific.net/amr.1030-1032.1074.
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Controlling the stability of surrounding rocks in underground excavations during in-depth resource development must be confronted with post-peak deformation and failure problems of jointed rock masses. This paper describes routine triaxial compression testing on standard cylinder specimen with persistent joints in different inclinations and under different confining pressures, and analyzes deformation characteristics of rock masses with persistent joints in different inclinations and under different confining pressures. Test results show that the peak strength, residual strength, and peak strain of the jointed specimen basically increase with increasing confining pressures but decrease with increasing joint inclinations. Test results well reflect that it is incorrect to evaluate deformation characteristics of jointed rock masses with continuum mechanics and research results provide a reference for the research on the stability of surrounding rocks in underground excavations.
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Wang, Qing Han, Shu Cai Li, Li Ping Li, Jing Wang i Qian Zhang. "Crack Propagation of Jointed Rock and Application". Applied Mechanics and Materials 651-653 (wrzesień 2014): 1143–46. http://dx.doi.org/10.4028/www.scientific.net/amm.651-653.1143.
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The excavation engineering in jointed rock masses, due to the changes in its original stress state, the preexisting fissures will expand and new fissures may emerge, which will degrade its mechanical and strength properties. This paper uses the DDARF method to preinstall fissures of different numbers and spacing in the rock block, then studies the crack initiation, expansion, transfixion and the destruction process by numerical modeling experiment, and finds the relevant stress strain curve. It also studies the influence of the numbers of fissures and different spacing and the influence of lateral compression on the test specimen to find the strength envelope of the test specimen. The parameters are applied in a case study. The differences in the failure behaviors of the intact and jointed rock masses after cavern excavation are analyzed and compared.
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Zhang, Zhiyu, Zhuo Li, Yonghui Huang i Haoshan Liu. "Influence of the Number of Parallel Joints on the Dynamic Mechanical Properties of Rock-Like Features". Geofluids 2022 (22.04.2022): 1–11. http://dx.doi.org/10.1155/2022/1564195.
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The number and distribution of joints in rock are closely related to their physical and mechanical properties. In this paper, given the propagation law of explosive stress waves in jointed rock during rock blasting and the influence of joints on dynamic mechanical properties and crushing energy dissipation of rock, parallel joints are simulated in the construction of concrete specimens using a mica sheet. The discrete Hopkinson test device is used to perform the impact test, which is based on the three-wave and fractal theory. Under dynamic load, the fluctuation characteristics, failure mode, fractal dimension, and energy dissipation transfer law of rock-like specimens with various parallel joints are studied in detail. The results show that the overall failure of the specimen becomes more severe with the increase of parallel joints, and the failure mode is changed from the conjugate shear failure of the complete specimen to the edge collapse failure with joints. Thus, as the number of joints increases, the static strength decreases, and the degree of reduction is positively related to the number of joints. With the number of joints, the changing trend of enhancement factor increases first and then slows down. Compared with nonjointed specimens, the transmission coefficient of 1-3 jointed specimens is decreased by 0.22, 0.05, and 0.17, respectively. The dimension of the specimen D f is positively correlated. Under the synonymous impact pressure of 0.35 MPa, the corresponding fractal dimension is increased from 2.27 to 2.42. The crushing energy consumption density, transmission coefficient, and dynamic compressive strength σ d of the specimen are significantly negatively correlated, and the crushing energy consumption density of the specimen decreased from 0.82 J/cm3 to 0.28 J/cm3.
10
Abdennour, C. Seibi, i M. Al-Alawi. "Experimental Investigation and Failure Analysis of Fastened GRP under Bending Using Finite Element Method and Artificial Neural Networks". Sultan Qaboos University Journal for Science [SQUJS] 4 (1.12.1999): 71. http://dx.doi.org/10.24200/squjs.vol4iss0pp71-78.
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This paper presents a novel approach that predicts the strength and failure modes of jointed Glass Reinforced Polyester (GRP) samples under bending using Finite Element Method (FEM) and Artificial Neural Network (ANN). The mechanical behavior of fastened glass fiber reinforced plastics composites under bending have been experimentally investigated. Samples were obtained from Amiantit Oman, a manufacturing company operating in Russail Industrial Zone in the Sultanate of Oman. The experimental program involved the conduct of three point bending tests as well as bending tests of mechanically fastened joints under static loads. The experimental results showed that the dimensions of the specimen such as the bending span length, specimen width, and specimen pitch affect GRP strength and stiffness. FEM and ANN results predicted accurately the types of failure modes and their locations along the specimens and compared well with the experimental results.
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Sitharam, T. G., M. Ramulu i V. B. Maji. "Static and Dynamic Elastic Modulus of Jointed Rock Mass". International Journal of Geotechnical Earthquake Engineering 1, nr 2 (lipiec 2010): 89–112. http://dx.doi.org/10.4018/jgee.2010070107.
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In this paper the compressive strength/elastic modulus of the jointed rock mass was estimated as a function of intact rock strength/modulus and joint factor. The joint factor reflects the combined effect of joint frequency, joint inclination and joint strength. Therefore, having known the intact rock properties and the joint factor, jointed rock properties can be estimated. The test results indicated that the rock mass strength decreases with an increase in the joint frequency and a sharp transition was observed from brittle to ductile behaviour with an increase in the number of joints. It was also found that the rocks with planar anisotropy exhibit the highest strength in the direction perpendicular to the anisotropy and the lowest at an inclination of 30o-45o in jointed samples. The anisotropy of the specimen influences the dynamic elastic modulus more than the static elastic modulus. The results were also compared well with the published works of different authors for different type of rocks.
12
Liu, Xin Yu, Ai Hua Liu i Bang Biao Wu. "An Experimental Study on the Mechanical Characteristics of Sandstone-Like Material with Preset Filling Joints". Applied Mechanics and Materials 353-356 (sierpień 2013): 644–49. http://dx.doi.org/10.4028/www.scientific.net/amm.353-356.644.
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This paper investigates the strength and deformation characteristics of the sandstone-like material containing the preset filling joints. The test specimens are designed with different height-diameter ratio. The uniaxial compression and shear tests were performed during the experimental studies. The results show that: (1) the failure models of the 3 kinds specimens including ones without joints, ones with "cruciform" joints and ones with "intersecting parallels" joints are similar to the general trend, e.g. X-shaped conjugated single-slope shear failure and single-slope shear failure under compression and shear tests ; (2) under uniaxial compression, the performance of intact specimen is clearly affected by its size, and the strength of jointed one is significantly affected by the weakening of the structure. This impact depends on the joints conditions, e.g. joint density, with filling material or without filling material; (3) Deformation modulus E and Cohesion c have no significant change for the 2 kinds jointed specimens, but the internal friction angle is obviously affected by joints and their fillings. The internal friction angle decreases rapidly with the increase of joints number.
13
Su, Ronghua, i Xiaolin Liu. "Fracture Failure Characteristics of Jointed Sandstone under Uniaxial Compression". Geofluids 2020 (26.11.2020): 1–14. http://dx.doi.org/10.1155/2020/8812522.
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Jointed rocks are ubiquitous in the complex environments (coupled heat and moisture conditions) encountered in deep underground mining. To investigate the influence of the joint locations on the strength, deformation, and fracture failure characteristics of the jointed sandstone, uniaxial compression tests were carried out for sandstone specimens in a natural moisture state and with a preexisting joint in different locations. The entire test process was recorded by a dynamic strain acquisition system and digital speckle observation equipment. The results show that the peak strength weakening of the jointed sandstone was different with different joint positions. The residual strength and lateral deformation of the jointed sandstone were affected by the location of the joint. The joint locations dominated the evolution of the fractures in the sandstone and influenced the failure mode. The fracture evolution in sandstone with a joint in the middle was characterized by the closure of the fractures away from the starting position and was finally destroyed by the combination of shearing and splitting. The evolution of fractures in the sandstone with a joint at the bottom was stopped on the other side, which was eventually sheared across the joint. Besides, based on fractal theory, the fracture distribution on the specimen surface was analysed at certain points (first appearance of fracture, peak point) and the final destruction state during the fracture evolution. The fractal dimension was obtained, which further characterizes the fracture evolution and failure of sandstone with a joint at different locations.
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Cao, Ping, Wen Cheng Fan i Ke Zhang. "Experimental Research on Failure Modes of Specimen Containing Non-Coplanar Joints". Advanced Materials Research 779-780 (wrzesień 2013): 332–36. http://dx.doi.org/10.4028/www.scientific.net/amr.779-780.332.
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To study the failure mechanism and failure mode of jointed rock under compressive-shear, many rock-like material specimens containing non-coplanar joints were made and a series of experiments were carried out. In the experiments, mica sheets were used as joint fillings, cement mortar was selected as rock-like material. Joints were made by inserting the mica sheet in cement mortar before initial setting. Mica sheets were left down as joint fillings. The results of experiments show that the dip angles of major joint have important influence on the failure mode of specimens. And the emerging position of wing cracks which exist in the prophase of specimens failure process changes with the dip angle. The shear strength of specimens has an important relationship with the dip angle of major joints. The smallest shear strength happens in the specimen with a joint angle of 15°, while the biggest value happens in 60°.
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Arnold, W. S. "Bearing Failures of Pin Jointed CSM Laminates under Biaxial Loading". Advanced Composites Letters 4, nr 2 (marzec 1995): 096369359500400. http://dx.doi.org/10.1177/096369359500400204.
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Preliminary results on the failure characteristics of pin jointed CSM laminates under biaxial loading are presented. Novel cruciform pin jointed test specimens are subjected to a range of biaxial stress fields which are shown to have a pronounced effect on joint strength. Bearing strengths are increased under transverse compression but reduced under transverse tension.
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Yang, Wendong, Guizhi Li, PG Ranjith i Lindong Fang. "An experimental study of mechanical behavior of brittle rock-like specimens with multi-non-persistent joints under uniaxial compression and damage analysis". International Journal of Damage Mechanics 28, nr 10 (19.02.2019): 1490–522. http://dx.doi.org/10.1177/1056789519832651.
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The mechanical behavior of jointed rock masses significantly affects the stability of rock engineering applications. In this paper, the peak strength, Young's modulus and failure patterns of brittle rock-like specimens with multi-non-persistent joints under uniaxial compression are investigated. The joint geometry is defined by four factors: joint angle, spacing, joint length, and rock bridge length. The experiment results show that the joint angle has the greatest influence on the peak strength and Young's modulus of specimens, followed by joint length. A damage mechanical theory is adopted which deals with some sets of joints distributed in rock masses. Based on the geometrical distribution of joints, a macro damage model which considers the influence of the normal vector and area density of joints is used to describe the joints. The peak strength and Young's modulus of jointed specimens predicted by the damage mechanics method reflect the trend of the experimental results, which proves the influence of initial geometric damage of joints on the peak strength and Young's modulus of jointed specimens. The initial geometric damage of joints is mainly induced by the joint area density. Finally, from the micro damage aspect, to analyze the damage evolution and strain softening process of jointed rock masses, a modified numerical model (damage strainsofting model) on the basis of secondary development in fast Lagrangian analysis of Continua is proposed to simulate the fracture development of jointed rock masses. The peak strengths, Young's modulus and failure modes of rock specimens with non-persistent joints under uniaxial compressions are simulated and compared with the results obtained from the lab experiments indicating that the model is capable to replicate the physical processes.
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Wang, Fei, Ping Cao, Yu Chen, Qing-peng Gao i Zhu Wang. "An Experimental Study on Mechanical Behavior of Parallel Joint Specimens under Compression Shear". Advances in Civil Engineering 2018 (8.08.2018): 1–12. http://dx.doi.org/10.1155/2018/5428670.
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In order to investigate the influence of the joint on the failure mode, peak shear strength, and shear stress-strain curve of rock mass, the compression shear test loading on the parallel jointed specimens was carried out, and the acoustic emission system was used to monitor the loading process. The joint spacing and joint overlap were varied to alter the relative positions of parallel joints in geometry. Under compression-shear loading, the failure mode of the joint specimen can be classified into four types: coplanar shear failure, shear failure along the joint plane, shear failure along the shear stress plane, and similar integrity shear failure. The joint dip angle has a decisive effect on the failure mode of the specimen. The joint overlap affects the crack development of the specimen but does not change the failure mode of the specimen. The joint spacing can change the failure mode of the specimen. The shear strength of the specimen firstly increases and then decreases with the increase of the dip angle and reaches the maximum at 45°. The shear strength decreases with the increase of the joint overlap and increases with the increase of the joint spacing. The shear stress-displacement curves of different joint inclination samples have differences which mainly reflect in the postrupture stage. From monitoring results of the AE system, the variation regular of the AE count corresponds to the failure mode, and the peak value of the AE count decreases with the increase of joint overlap and increases with the increase of joint spacing.
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Zhao, Yang, Ye Zhao, Zhe Zhang, Wenhai Wang, Jiaming Shu, Yang Chen, Jianguo Ning i Lishuai Jiang. "Investigating the Influence of Joint Angles on Rock Mechanical Behavior of Rock Mass Using Two-Dimensional and Three-Dimensional Numerical Models". Processes 11, nr 5 (6.05.2023): 1407. http://dx.doi.org/10.3390/pr11051407.
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Numerical testing is an ideal testing method in the research on the mechanical behaviors of jointed rock. However, there are few systematic studies focused on the comparison between the two-dimensional (2D) and the three-dimensional (3D) simulation effects on rock mechanical behaviors, particularly those of jointed rock. In this paper, a particle flow model was established by utilizing PFC2D and PFC3D to represent the rock materials, and the rock (especially jointed rock) mechanical behaviors (uniaxial compressive strength UCS, tensile strength TS, crack initiation stress level Kσ, and the pattern of crack initiation) between 2D and 3D models were compared and analyzed. As expected, the result shows that the UCS and TS showed an increasing tendency with the increase in the joint angle (β) for both the 2D and the 3D models, and the strength of the 3D model was less than that of the 2D model under uniaxial compression but was greater than that of the 2D model under uniaxial tension. The crack initiation and Kσ of the specimens were essentially the same for the 2D and 3D models, and the tensile stresses are more concentrated than the compressive stresses before the failure of the specimen; the uniaxial tensile failure more closely approached abrupt failure than the uniaxial compression failure. The tensile cracks were often initiated at the tips of the joints for both the 2D and 3D models, but they were initiated in the middle of the joints when β was low (β = 0° and β = 15° in both the 2D and 3D models) under uniaxial compression and when β reached 90° under uniaxial tensile. The test results were validated and further analyzed with mathematical analysis. This study has relative referential value to experiments on jointed rock and to analysis of the instability fractures of engineering rock mass.
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Wang, Gui-Lin, Liang Zhang, Zhen Wang, Jian-Zhi Zhang, Fan Sun i Pei-Yong Qiu. "Acoustic-Mechanical Responses of Intact and Flaw-Contained Rock Deformation under Uniaxial Compression: A Comparison". Advances in Civil Engineering 2019 (13.05.2019): 1–12. http://dx.doi.org/10.1155/2019/7940923.
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The study of the mechanical properties and cracking behaviors of jointed rock masses is important in rock engineering projects. In the present study, a series of uniaxial compression experiments were conducted on intact rock, and rock masses with single or double preexisting flaws, and then the strength, deformability, and fracture behavior of samples are investigated. Moreover, photographic monitoring technique and emission monitoring technique are introduced to explore the fracturing mode and the acoustic emission (AE) evolution characteristic of fractured rock during the whole loading process. The obtained results show that the preexisting flaw has a strong influence on the mechanical properties, fracture behavior, and AE characteristic of sandstone specimens. In detail, the stress-strain curves show that no significant stress jump occurs at prepeak and postpeak points for intact sandstone specimens; however, the flaw-contained sandstone specimens exhibit distinct stress jump during the entire loading process. Meanwhile, the strength parameters of the the rock specimen is obviously weakened by the preexisting fissures, and the uniaxial compression strength of rock specimens generally decreases with the increase in the number of preexisting fissure as well as the peak strain and the elastic modulus. The failure modes of intact and flaw-contained sandstone specimens exhibit the splitting failure and the mixed failure modes of shear and tension, respectively. Similarly, the maximum AE counts and AE energy both decrease with the increasing number of preexisting flaw. The present research can enhance the understanding of mechanical properties, cracking behaviors, and failure mechanism of jointed rock mass.
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Yu, Weijian, Hanxiao Guo, Ke Li i Bao Pan. "Experimental Study on Uniaxial Compression Mechanics and Failure Characteristics of Non-Through Fractured Rock". Sustainability 15, nr 6 (10.03.2023): 4968. http://dx.doi.org/10.3390/su15064968.
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The stability of damaged rock mass is a critical problem in the control of surrounding rock in underground engineering. As the main macroscopic defect of rock surrounding engineering, it is of great significance to study its propagation mechanism and the experimental characteristics of rock mechanics. Surface-fractured rock mass is a typical representative of three-dimensional fracture. To reveal the failure mechanism of surface-fractured rock mass, a three-dimensional mechanical failure model of a surface-fractured rock specimen was established, including the initiation, crack propagation, and cooperative deformation of the rock micro-element. Taking the depth of the surface horizontal fissure as a variable, standard rock specimens with surface horizontal fissures of different depths were prepared, and an experimental study of surface-fractured rock specimens was carried out. The RMT rock mechanics test system was used to perform uniaxial compression tests on standard specimens containing fractured rock specimens of different depths. The complete stress–strain curves of samples with different fracture depths were obtained, and the influence of different fracture depths on rock strength and deformation characteristics was analyzed. The crack initiation, propagation, and failure modes of the specimens under uniaxial compression were analyzed based on high-speed camera technology. Through the combination of 3D image processing and acoustic emission monitoring, differences between failure before and after the peak in both asymmetrically damaged rock specimens and symmetrically damaged rock specimens were found. The mechanism of weak strength and weak stability of asymmetrically damaged rock specimens after the peak was explained theoretically. The research results showed that the existence of the horizontal joint plane directly led to a significant reduction in the strength of the jointed rock sample, and the fracture depth played an important role in controlling the failure mode of the jointed rock specimens. The uniaxial compression of rock specimens with horizontal non-penetrating surface fissures produced three-dimensional failure modes, and the depth of surface fissures changed the failure mode of the specimens under uniaxial compression. As the crack depth increased, the failure mode of the specimen changed from tensile failure to shear failure. The surface crack sample showed regional asymmetric failure and poor structural stability.
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González-Fernández, M. A., X. Estévez-Ventosa, F. García-Bastante, L. R. Alejano i A. M. Ferrero. "Study of size effects on the peak and residual strength of intact and artificially fissured granite samples". IOP Conference Series: Earth and Environmental Science 1124, nr 1 (1.01.2023): 012023. http://dx.doi.org/10.1088/1755-1315/1124/1/012023.
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Abstract There are not many studies on jointed rock specimens, which can be considered small scale rock mass analogs. On the other hand, the scale effects in the mechanical properties of such samples have seldom been studied. With the aim of continuing previous research on intact granite rocks, the authors have carried out sets of 25 stress-strain triaxial compressive tests on 1 sub-vertical and 2 sub-horizontal 38 mm, 54 mm and 84 mm diameter jointed granite specimens at various confinements. Peak and residual strength values were obtained and compared to those recovered form intact rock samples. Results suggest that peak strength follows similar trends with scale to those observed on intact rock, even if lower strength values are logically recorded. Regarding residual strength, the obtained results are in line with those observed trends for standard size samples, showing a similar trend for all cases independently of scale, even if we observe larger variability for jointed samples. The authors have also compared the values fitting the generalized Hoek-Brown criterion for rock masses to better understand the behavior in relation to sample size. So scale effects clearly appear on jointed rock peak strength of jointed sample; even if residual strength seems hardly affected by scale.
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Zhao, Yang, Yongning Wu, Qing Xu, Lishuai Jiang, Wanpeng Huang, Peipeng Zhang i Zhongtao Niu. "Numerical Analysis of the Mechanical Behavior and Failure Mode of Jointed Rock under Uniaxial Tensile Loading". Advances in Civil Engineering 2020 (29.10.2020): 1–13. http://dx.doi.org/10.1155/2020/8811282.
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In the field of rock engineering, tensile failure is one of the most significant failure modes due to the presence of joints/fractures. However, due to the limitations of current laboratory testing, it is difficult to carry out direct tensile tests on jointed rock specimens in the laboratory. To study the effect of joints on the mechanical behavior and failure mode of jointed rock specimens, a three-point modeling method that can consider arbitrarily arranged rock joints is deduced and applied to discrete element simulation. The effects of different joint angles (the inclination angle α, rotation angle β, and superimposed angle γ of α and β, where γ is the angle between the joint and horizontal plane), the density (n), and the rate of cutting area (RCA) of the specimen loading surface (LSS) on the tensile strength (σt), elastic modulus in tension (Et), and failure mode of the specimens were analyzed. The results show that the joint angle (considering α, β, and γ) and RCA have a significant effect on the resulting σt and failure mode, while n has a significant effect on Et. The failure mode of the specimen changes from tensile failure along the joint to direct tensile failure of the specimen as γ increases, and the mechanical behavior transitions from unstable to stable. In addition, the main influence of γ on the mechanical behavior of specimens is revealed, and the change process of the failure mode after the cutting of the LSS is analyzed. The present research can be utilized for multiple purposes, including the joint development of surrounding rock and failure dominated by tensile failure in underground engineering, especially for tunnels, roadways, chambers, and so forth.
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Yan, Long, Weiya Xu, Rubin Wang i Qingxiang Meng. "Numerical simulation of the anisotropic properties of a columnar jointed rock mass under triaxial compression". Engineering Computations 35, nr 4 (11.06.2018): 1788–804. http://dx.doi.org/10.1108/ec-07-2017-0240.
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Purpose The purpose of this paper is to investigate the anisotropic characteristics of the special structure of a columnar jointed rock masses and provide reference to forecast the behavioral characteristics of real samples. Design/methodology/approach This study used FLAC3D numerical software to simulate the mechanical behavior of columnar jointed rock masses with different columns angles (ß) under different stress conditions. The peak strength, elastic modulus and Poisson’s ratio were obtained to investigate the strength, deformation characteristics and failure modes of the rock masses under conventional and true triaxial compression. Findings The results showed that the compressive strength of the specimens presents a U-shape under different joint inclinations. The strength of the specimens reaches a maximum value when ß = 90°, and the value for ß = 0° is slightly lower and reaches a minimum value when ß = 50°. The elastic modulus and Poisson’s ratio of the samples are obviously anisotropic, the anisotropic coefficient decreases with increasing confining pressure. When σ2 ≠ σ3, the peak strengths of the samples are related to the direction of the minor principal stress, and the failure modes of the samples are related to the confining pressure and joint inclination. Originality/value The present paper uses a numerical simulation method to examine the strength and deformation characteristics of a columnar jointed rock mass under conventional and true triaxial compression. The aim is to provide a reference to forecast the mechanical characteristics of test samples in the laboratory.
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Feng, Zhongliang, Xin Chen, Yu Fu, Shaoshuai Qing i Tongguan Xie. "Acoustic Emission Characteristics and Joint Nonlinear Mechanical Response of Rock Masses under Uniaxial Compression". Energies 14, nr 1 (2.01.2021): 200. http://dx.doi.org/10.3390/en14010200.
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The joint arrangement in rock masses is the critical factor controlling the stability of rock structures in underground geotechnical engineering. In this study, the influence of the joint inclination angle on the mechanical behavior of jointed rock masses under uniaxial compression was investigated. Physical model laboratory experiments were conducted on jointed specimens with a single pre-existing flaw inclined at 0°, 30°, 45°, 60°, and 90° and on intact specimens. The acoustic emission (AE) signals were monitored during the loading process, which revealed that there is a correlation between the AE characteristics and the failure modes of the jointed specimens with different inclination angles. In addition, particle flow code (PFC) modeling was carried out to reproduce the phenomena observed in the physical experiments. According to the numerical results, the AE phenomenon was basically the same as that observed in the physical experiments. The response of the pre-existing joint mainly involved three stages: (I) the closing of the joint; (II) the strength mobilization of the joint; and (III) the reopening of the joint. Moreover, the response of the pre-existing joint was closely related to the joint’s inclination. As the joint inclination angle increased, the strength mobilization stage of the joint gradually shifted from the pre-peak stage of the stress–strain curve to the post-peak stage. In addition, the instantaneous drop in the average joint system aperture (aave) in the specimens with medium and high inclination angles corresponded to a rapid increase in the form of the pulse of the AE activity during the strength mobilization stage.
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Ambarita, H., M. Daimaruya i H. Fujiki. "Impact Fracture of Jointed Steel Plates of Bolted Joint of Cars". Applied Mechanics and Materials 566 (czerwiec 2014): 232–37. http://dx.doi.org/10.4028/www.scientific.net/amm.566.232.
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The present study is concerned with the development of a fracture criterion for the impact fracture of jointed steel plates of a lap bolted joint used in the suspension parts of a car body. For the accurate prediction of crash characteristics of car bodies by computer-aided engineering (CAE), it is also necessary to examine the behaviour and fracture of the jointed steel plates subjected to impact loads. Although the actual impact fracture of jointed steel plates of a lap bolted joint in cars is complicated, for simplifying it is classified into the shear fracture and the extractive fracture of jointed steel plates. Three kinds of steel plates, i.e., common steel with the tensile strength of 270 MPa and two high tensile strength steels with the tensile strength of 440 and 590 MPa level used for vehicles, are examined. In the impact shear test, the specimens are made of two plates and jointed by a bolt, and in the impact extractive test the specimens are made of a plate and drilled in the centre for a bolt. The impact shear test of jointed steel plates of lap bolted joints is performed using a modified split Hopkinson bar apparatus, while the impact extractive one is performed using one-bar method. Numerical simulations by a FEM code LS-DYNA are also carried out in order to understand the mechanism of shearing and extractive fractures process of jointed steel plates. The obtained results suggest that a stress-based fracture criterion may be developed for the impact shearing and extractive fractures of jointed steel plates of lap bolted joints used in a car body.
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Shu, Pei-Yun, Chen-Yu Lin, Hung-Hui Li, Ta-Wui Cheng, Tzuu-Hsing Ueng i Tai-Tien Wang. "Dynamic Response of Rock Containing Regular Sawteeth Joints under Various Loading Rates and Angles of Application". Applied Sciences 10, nr 15 (28.07.2020): 5204. http://dx.doi.org/10.3390/app10155204.
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Intact rock-like specimens and specimens that include a single planar joint or triangular sawteeth joint at various angles are prepared for split Hopkinson pressure bar (SHPB) testing at loading rates of 303.1–5233.6 GPa/s. Only results that are associated with an error (eε) of less than 20.0% are utilized in subsequent analyses. The effects of the loading rate and angle of the load applied to various joint patterns on the failure type and dynamic peak stresses/strength of the specimens are investigated. Experimental results demonstrate that failure of each specimen can be classified into the following four types, Type A: integrated with or without tiny flake-off, Type B: slide failure, Type C: fracture failure, and Type D: crushing failure. The results of statistical analysis of variance (ANOVA) indicate that the loading rate, the angles of the base plane (β), and the asperity (α) of the sawteeth joint of the specimen all affect its dynamic peak stress when fracture failure occurs. The loading rate and β are important when the slide failure occurs, and the loading rate is the sole factor that significantly influences its dynamic peak stress when the specimen is crushed to failure. The dynamic peak stress of the specimen increases with the loading rate, while the rate of increase gradually decreases. The β and α of a jointed specimen affect the location of stress concentration during loading, further influencing the dynamic peak stress of such a specimen under slide and fracture failure. When the loading rate is high and the specimen is crushed to failure, the influences of β and α disappear, and the increase of loading rate reduces the efficiency of raising the dynamic peak stress.
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Singh, Manjeet, H. Bhunia i J. S. Saini. "Effect of Ply Orientation on Strength and Failure Mode of Pin Jointed Unidirectional Glass-epoxy Nanoclay Laminates". Defence Science Journal 65, nr 6 (10.11.2015): 489. http://dx.doi.org/10.14429/dsj.65.8917.
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In the present work the effect of the different ply orientations and nano filler on the bearing strength and failure mode of the pin joints is investigated both experimentally and numerically. Glass-epoxy composite laminates were prepared with [0°/45°/90°], [0°/45°/0°] and [0°/90°/0°] ply orientations. Nanoclay filler with 1, 2, 3, 4 and 5wt% were added in the epoxy for the said orientations to prepare the pin joints. Results show that the strength of the pin joints is drastically dependent on both ply orientations and nanofiller wt%. The joint geometry i.e., the distance from the free edge of specimen to the diameter of the hole (E/D) ratio and width of the specimen to the diameter of the holes (W/D) ratio were also investigated which effected the failure mode of the joints. Tsai-Wu failure theory along with the characteristics curve method was used for the prediction of failure modes numerically.
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Yang, Jun, Bo Li, Qiang Jia, Yuan Xing Li, Ming Yue Zhang i Hui Chen. "Influence of Stress Concentration on Fatigue Property of Welded Joints of 5083 Aluminum Alloy". Applied Mechanics and Materials 456 (październik 2013): 451–55. http://dx.doi.org/10.4028/www.scientific.net/amm.456.451.
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Fatigue test of the welded joint of 5083 aluminum alloy with smooth and height of specimen and the weld zone than the high test measurement and theoretical stress concentration coefficient calculation, the weld reinforcement effect of stress concentration on the fatigue performance of welded joints. The results show that: Smooth tensile strength of specimens for 264MPa, fatigue strength is 95MPa, the tensile strength of the 36%. Higher tensile strength of specimens for 320MPa, fatigue strength is 70MPa, the tensile strength of the 22%. Higher specimen stress concentration coefficient is 1.64, the stress concentration to the weld toe becomes fatigue initiation source, and reduces the fatigue strength and the fatigue life of welded joints.
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Wang, Lei, Shi Chen Li, Jian Xin Han i Zhong Yi Zeng. "Experimental Study on Strength of Rock Masses with Transfixion Joint under Uniaxial Compression". Applied Mechanics and Materials 353-356 (sierpień 2013): 856–59. http://dx.doi.org/10.4028/www.scientific.net/amm.353-356.856.
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The relationship between the peak strength of rock masses and joint inclination angle is closely, to study its relationship, experiment on pre-existing persistent jointed rock cylindrical standard specimens was made under uniaxial compression by high stiffness servo control testing machine, experiment found that: the residual peak intensity and peak strength are increased with the decrease of jointed and nonlinear. Analysis on the peak intensity changing with the fissure inclination using Kulun strength theory, theory analysis conclusion is consistent with the experiment, prove the conclusions of experiments and theoretical analysis all can reflect the law of rock masses with transfixion joint failure strength well.
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Fu, Jin Wei, Wei Shen Zhu, Li Ge Wang i Xiang Gang Wang. "Numerical Simulation of the Crack Propagation Processes in Rocks with Double Joints". Applied Mechanics and Materials 90-93 (wrzesień 2011): 559–64. http://dx.doi.org/10.4028/www.scientific.net/amm.90-93.559.
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Engineering rock mass is commonly a brittle medium containing lots of joints or fissures. Under the stress redistribution in construction，the crack initiation，propagation，and coalescence may cause the strength and stiffness degradation of such medium. And these have an important impact on the stability of rock mass. By employing the analysis software of FLAC3D and improving the constitutive relation, the failure process of the double-cracked rock specimen under uniaxial and two-dimensional compression are simulated and studied. The numerical results match well with the testing results obtained by former scholars. The strength envelope of the jointed rock is obtained as well, and it is applied to analyzing the stability of a slope project.
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Cao, Ri-hong, Ping Cao, Hang Lin, Xiang Fan, Chunyang Zhang i Taoying Liu. "Crack Initiation, Propagation, and Failure Characteristics of Jointed Rock or Rock-Like Specimens: A Review". Advances in Civil Engineering 2019 (17.02.2019): 1–31. http://dx.doi.org/10.1155/2019/6975751.
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Rock masses are heterogeneous materials containing a large number of discontinuities, and the failure of the natural rock mass is induced by the crack propagation and coalescence of discontinuities, especially for the rock mass around tunnel or underground space. Because the deformation or failure process of jointed rock mass exhibits strongly nonlinear characteristics, it is also very difficult to predict the strength and failure modes of the rock mass. Therefore, it is very necessary to study the failure mechanisms of jointed rock mass under different stress conditions. Apart from the stress condition, the discontinuities geometry also has a significant influence on the mechanical behavior of jointed rock mass. Then, substantial, experimental, and numerical efforts have been devoted to the study of crack initiation, propagation, and coalescence of rock or rock-like specimens containing different kinds of joints or fissures. The purpose of this review is to discuss the development and the contribution of the experiment test and numerical simulation in failure behavior of jointed rock or rock-like specimens. Overall, this review can be classified into three parts. It begins by briefly explaining the significance of studying these topics. Afterwards, the experimental and numerical studies on the strength, deformation, and failure characteristics of jointed rock or rock-like materials are carried out and discussed.
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Soyama, Hitoshi, Michela Simoncini i Marcello Cabibbo. "Effect of Cavitation Peening on Fatigue Properties in Friction Stir Welded Aluminum Alloy AA5754". Metals 11, nr 1 (30.12.2020): 59. http://dx.doi.org/10.3390/met11010059.
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Friction stir welding (FSW) is an attractive solid-state joining technique for lightweight metals; however, fatigue properties of FSWed metals are lower than those of bulk metals. A novel mechanical surface treatment using cavitation impact, i.e., cavitation peening, can improve fatigue life and strength by introducing compressive residual stress into the FSWed part. To demonstrate the enhancement of fatigue properties of FSWed metal sheet by cavitation peening, aluminum alloy AA5754 sheet jointed by FSW was treated by cavitation peening using cavitating jet in air and water and tested by a plane bending fatigue test. The surface residual stress of the FSWed part was also evaluated by an X-ray diffraction method. It was concluded that the fatigue life and strength of FSWed specimen were improved by cavitation peening. Whereas the fatigue life at σa = 150 MPa of FSWed specimen was about 1/20 of the bulk sheet, cavitation peening was able to extend the fatigue life of the non-peened FSW specimen by 3.6 times by introducing compressive residual stress into the FSWed part. This is the first paper to demonstrate the improvement of fatigue properties of FSWed metallic sheet by cavitation peening.
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Pekbey, Yeliz. "Failure Strength of E-Glass/Epoxy Composite Pinned Joints: Effect of Geometry, Clamping Torque and Laminate Orientation". Advanced Composites Letters 16, nr 3 (maj 2007): 096369350701600. http://dx.doi.org/10.1177/096369350701600302.
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The experimental investigations described in this paper were conducted in order to study the strength and failure behavior of composite plate with pin-loaded conditions. The main objective of the present paper was to investigate the influence of certain factors on the strength of the pin-loaded in E-GLASS/EPOXY composite plate with different orientations such as [0/90/±30]s and [0/90/±60]s. These factors included the preload moment (M=0, 2 Nm), the ratio of the edge distance to the pin diameter ( E/ D), and the ratio of the specimen width to the pin diameter ( W/ D). The mechanical properties and failure strengths of E-GLASS/EPOXY composite were obtained with experimental measurements. Based on experiments, the effects of laminate orientation, and preload moment on joint strengths were systematically investigated. In addition, geometrical configurations of specimens were suitably varied in order to observe all possible failure modes. A total of 150 different pin-loaded composite plate specimens were tested under static loading conditions. The specimen tested exhibited different failure modes, consisting of bearing, net-tension and shear-out, depending on the geometry adopted. Guidelines for effective laminate orientations, geometrical configurations and preload moment for mechanically pin connected E-GLASS/EPOXY composite plate were specified based on ultimate bearing strength. From the experiments, it was also found that glass-epoxy with [0/90/±30]s yielded the highest bearing strengths. Bearing strengths reached when E/D and W/D ratios were equal or greater than 4 both [0/90/±30]s and [0/90/±60]s orientations. Besides, the experimental results showed that the load-displacement curve of specimen with M=0, had the lowest the failure strength. M=2Nm preload moment, had the maximum failure load.
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Yoon, Ho Chel, Ren Liang Wang, Montasser Dewidar, Yang Bae Jeon, Jun Yong Choi i Jae Kyoo Lim. "Effects of Resistance Welding on the Failure Strength Properties of Natural Fiber Reinforced Composite". Key Engineering Materials 353-358 (wrzesień 2007): 1974–78. http://dx.doi.org/10.4028/www.scientific.net/kem.353-358.1974.
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This research is concerned with a study of failure strength of natural fiber composite. Tensile-shear tests were carried out with the single-lap resistance welded joined specimens consisting of composite materials. Composite materials were manufactured using the polyester as a matrix and bamboo natural fiber layer as a reinforcement. Two types of specimen with different reinforcement positions were tested to evaluate the failure strength of natural fiber reinforced composite resistance welded joined specimens. The test results were presented by tensile-shear strength. The failure mechanism was discussed in order to explain the lower tensile-shear strength of composite and position of bamboo natural fiber layer on the failure strength properties were explained
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Chen, Xin, Zhongliang Feng i Cheng Cheng. "Numerical Study on Anisotropic Influence of Joint Spacing on Mechanical Behavior of Rock Mass Models under Uniaxial Compression". Energies 13, nr 24 (18.12.2020): 6698. http://dx.doi.org/10.3390/en13246698.
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Mechanical properties of rock masses are dominated by the nonlinear response of joints and their arrangement. In this paper, combined influences of joint spacing (s) and joint inclination angle (β) on mechanical behavior of rock mass models with large open joints under uniaxial compression were investigated by PFC modeling. With a large amount of local measurement circles placed along the pre-defined measurement lines (ML), stresses and joint response parameters at different scales (the measurement circles, the MLs and the whole specimen) were defined and calculated. It was found that macroscopic behaviors of the jointed specimens, such as four types of deformation behaviors, four failure modes, strength, deformability modulus and ductility index, are dominated by nonlinear response of the joint system, especially the interaction between the joints and rock bridges. The joints may experience three stages, i.e., starting to close, closed and opening again. On the joint plane, the peak stresses of the rock bridges and those of the joints may not be reached at the same time; i.e., joint strength mobilization happens with the loss of the rock bridges’ resistance. The influence of s on specimen behavior is little for β = 90°, obvious for β = 0° or 30° and significant for β = 45° or 60°, and this can be related to their different microscopic damage mechanisms.
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Jaafer, Abdulkhaliq, i Dhiaa Chasib Resheqal. "Improving RC Beam-Column Joints Characteristics Using Different Reinforcement Details". Misan Journal of Engineering Sciences 1, nr 1 (11.06.2022): 16–25. http://dx.doi.org/10.61263/mjes.v1i1.10.
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This paper aims to study the effect of concrete confining using a new style of internal closed stirrups and longitudinal steel bars along with the middle third of the beam length of the beam-column joints. Also, the influence of concrete compressive strength was investigated using three types of concrete normal strength concrete (NSC), high strength concrete (HSC), and steel fiber concrete (SFRC). Nine reinforced concrete specimens with the same dimensions are divided into three groups according to the concrete type with different reinforcement details in the middle third of the specimen’s length. Four specimens with (NSC) represent the first group, while three specimens consist in the second group with (HSC). Steel fiber of 2% was used in two specimens of the third group (SFRC). The test results showed that using additional reinforcement steel bars as a closed stirrup arranged about the neutral axis improved the flexural strength and enhanced the load-carrying capacity for the reinforced concrete joints. The ultimate capacity of the joints increased by a range (34 to 50) % more than the control specimen. The ultimate strength was also increased for the specimens due to using high-strength concrete with a range (of 13 to 66) % compared with the specimen of normal compressive strength.
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Zhou, Kefeng, Changxin Liu, Su Li i Yanhui Cheng. "Size Effect on the Rheological Shear Mechanical Behaviors of Different Joints: A Numerical Study". Geofluids 2022 (22.03.2022): 1–9. http://dx.doi.org/10.1155/2022/7484209.
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Under the condition of constant external stress, the displacement and stress of the joint will be adjusted continuously with time, resulting in the creep phenomenon, that is, the continuous increase of the strain with time, which further causes the damage of the jointed rock mass. In order to study the size effect of joint shear rheological mechanical properties, this paper conducted shear rheological numerical simulations on nonpenetrating and penetrating joint models established in Particle Flow Code (PFC) and analyzed the effect of specimen size on the rheological and shear mechanical behavior of the model. The results show the following: (1) For the rheological direct shear test, the instantaneous shear displacement of the joint increases continuously as the size increases, showing a significant positive size effect. (2) For through-type joints, only the cohesion shows a certain size effect, and the shear strength and friction angle have a nonobvious relation with specimen size. (3) For anchored through-type joints, the increase of the model size leads to a decrease in shear strength, while the friction angle-size effect of joints is not remarkable.
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Xie, Bing, Jin Jun Guo i Xiang Xia. "Influence of Loading Rate on Uniaxial Compression Test of Rock Specimen with Random Joints". Advanced Materials Research 396-398 (listopad 2011): 217–20. http://dx.doi.org/10.4028/www.scientific.net/amr.396-398.217.
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Numerical specimens with ramdom joints is established by particle flow code PFC2D and uniaxial compression tests are conducted under three different loading rate. Studies have shown that strength of uniaxial compression are all increased with the loading rate no matter what specimen is complete or with random joints. The sensitivity of changes of uniaxial compressive strength of specimen with random joints decreases with increasing of the loading rate.
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Li, Fei, Huafeng Deng, Wenwen Liu i Guoyong Duan. "Mechanical Properties of Deep Variable Dip Joint Rock Mass in Reservoir Area under Wet and Dry Conditions". Advances in Materials Science and Engineering 2023 (29.04.2023): 1–17. http://dx.doi.org/10.1155/2023/9508173.
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The mechanical property of deep complex jointed rock mass is a hot topic in rock mechanics. In order to grasp the deformation and damage rules of through-going variable dip joint rock masses, the triaxial compression test and joint surface morphology scan test were conducted on cylindrical specimens in dry and wet conditions under 0, 5, 10, and 20 MPa water pressure. Through these tests, the deterioration law of rock samples under different pore water pressure in dry and wet conditions was studied. The effect of pore water pressure on the strength of saturated jointed rock sample is nonlinear. The imposed pore water pressure can significantly increase the axial deformation of rock samples, and higher pore water pressure can facilitate the deformation deterioration of samples. When the pore pressure is high, the rock samples show the characteristics of sliding shear failure. Under different pore pressure, the compressive strength of dry jointed rock is significantly higher than that of saturated jointed rock, and the saturated rock is more susceptible to sliding in the joint plane than dry rock. Dry jointed rock samples have stronger deformation ability than saturated jointed rock samples. The change rate of the morphologic parameters and the distribution of the failure cracks indicate that the stress concentration is evident in the middle of the joint plane.
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Xiong, L. X., H. J. Chen, T. B. Li i Y. Zhang. "Experimental study on the uniaxial compressive strength of artificial jointed rock mass specimen after high temperatures". Geomechanics and Geophysics for Geo-Energy and Geo-Resources 4, nr 3 (15.03.2018): 201–13. http://dx.doi.org/10.1007/s40948-018-0085-7.
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Hou, Jian, Assaad Taoum, Nathan Kotlarewski i Gregory Nolan. "Study on the Effect of Finger-Joints on the Strengths of Laminations from Fiber-Managed Eucalyptus nitens". Forests 14, nr 6 (8.06.2023): 1192. http://dx.doi.org/10.3390/f14061192.
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The performance characteristics of finger-joints as a jointing technique for Eucalyptus nitens is crucial for their use in engineered wood products. This research evaluated the strength of the finger-jointed laminations made from fiber-managed E. nitens. A total of 237 specimens with (117 pieces) and without (120 pieces) finger-joints were sectioned from finger-jointed laminations and tested by bending, tensile, shear, and bearing tests. Bending and tensile tests were paired to identify any correlations. The mean value with finger-joints for bending and tensile were 92.1 MPa and 79.6 MPa, respectively. The presence of finger-joints reduced the strength values. Joint efficiencies in bending and tensile are 0.73 and 0.62, respectively. The distributions of bending and tensile strength were similar for the samples without finger-joints. For the samples with finger-joints, tensile strength was significantly lower than paired bending strength. Shear test results show that the short-span test is inefficient in obtaining the shear strength of fiber-managed E. nitens boards. Meanwhile, the finger-joint efficiency in the bearing is 0.86. The prediction models of lamination’s bending, tensile, and bearing strength were established by non-destructive properties as predictors. Bending strength was highly correlated to the modulus of elasticity value, while tensile and bearing strength were correlated to density. This study obtained promising results on finger-jointed boards from fiber-managed E. nitens suggesting they could be suitable for structural purposes.
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Stolze, Hannes, Michael Gurnik, Sebastian Kegel, Susanne Bollmus i Holger Militz. "Determination of the Bonding Strength of Finger Joints Using a New Test Specimen Geometry". Processes 11, nr 2 (2.02.2023): 445. http://dx.doi.org/10.3390/pr11020445.
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In this study, a specimen geometry for testing finger joints was developed using finite element simulation and proofed by experimental testing. Six different wood species and three adhesives were used for finger-jointing specimens. With the test specimen geometry, the bonding strength of the finger joints was determined without the usual self-locking of the joint. Under load, the test specimen geometry introduces maximum stress at the beginning of the bond line (adhesive zone). However, the test specimen geometry does not generate a symmetric stress state. The main difficulty here is the flank angle of the finger joint geometry. The wood species and adhesives significantly influenced the performance of the finger joints.
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Abbas, Hasan Ali, Zainab Mohamed, Muntadher J. Taher, Sakhiah Abdul Kudus, Manaf Raid Salman i Hasanain Muhammad Ghaltan. "Shear strength characteristics of weathered jointed Kenny Hill interbedded formation for cylindrical specimen under direct shear test". International Journal of Applied Mechanics and Engineering 28, nr 2 (28.06.2023): 1–12. http://dx.doi.org/10.59441/ijame/168938.
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The sliding failures commonly occur in interbedded formations along the weakness plane of the bedding plane a sedimentary rock or the joint interface. Therefore, studying the shear strength characteristics at the bedding plane or interface is crucial for evaluating the expected failure plane. In this study, the shear strength characteristics of planar jointed Kenny Hill shale, sandstone, and shale-sandstone specimens were investigated using the direct shear box method. The results reveal that the friction angle values for the planar sandstone, shale-sandstone, and shale are 31.28°, 21.1°, and 19.34°, respectively. These findings, combined with the shear stress-strain behavior, suggest that the interface (shale-sandstone) is primarily influenced by the shale characteristics rather than the sandstone characteristics. Hence, it is important to consider failure along the interface when analyzing critical conditions, particularly in slope failure scenarios.
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Wang, X. B. "Effects of Joint Width on Strength, Stress-Strain Curve and Strain Localization of Rock Mass in Uniaxial Plane Strain Compression". Key Engineering Materials 353-358 (wrzesień 2007): 1129–32. http://dx.doi.org/10.4028/www.scientific.net/kem.353-358.1129.
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Effects of joint width (JW) on the macroscopic stress-strain curve, the failure process and mode of jointed rock specimen (JRS) in plane strain compression are modeled by use of FLAC. The failure criterion of intact rock outside the inclined joint is a composite Mohr-Coulomb criterion with tension cut-off and the linear strain-softening post-peak constitutive relation is adopted. The joint is treated as quadrate elements of ideal plastic material beyond the peak strength. A written FISH function is used to automatically find elements in the joint. Numerical results show that the peak strength of JRS depends on JW and is lower than that of intact rock specimen without joint. For JRS, the shear strains are concentrated into the joint or the new generated shear bands (NGSBs); the peak strength decreases with an increase of JW. At lower or higher joint inclination angle (JIA), the failure mode and pattern of NGSBs are not related to JW. The post-peak response becomes ductile at wider JW and higher JIA. The post-peak slope of stress-strain curve at lower JIA is not dependent on JW since the width and inclination angle of NGSBs are not affected by JW.
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Li, Huigui, Zhengkai Yang i Huamin Li. "Mechanical Characteristics and Failure Mechanism of Siltstone with Different Joint Thickness". Advances in Civil Engineering 2020 (24.10.2020): 1–10. http://dx.doi.org/10.1155/2020/3824538.
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The mechanics of rock mass is significantly affected by joints, but many existing studies of jointed rocks make simplifications that do not consider the joint thickness. To further study the influence of joint thickness on rock mechanics (mechanical properties, failure mechanism, damage model, etc.), we fabricated jointed siltstone specimens with different joint thickness (5, 10, 15, and 20 mm) and the specimens were subjected to uniaxial compression tests. The effects of joint thickness on the uniaxial compression strength (UCS), the strain at UCS, the elastic modulus, and the stress-strain curves were thus analyzed. For the stress-strain curve, with rising joint thickness, the upper concave in the initial compression stage intensified, the slope of the stress-strain in the elastic stage decreased, and the sudden stress drop after peak strength became more obvious. Both the peak compression strength and the elastic modulus gradually decreased with rising joint thickness, but a positive correlation was found between the strain at UCS and the joint thickness.
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Hao, Rui Hua, Jia Chen Liu, Min Wang, Xue Dong i Ming Chao Wang. "Tensile Strength and Bonding Mechanism of the Mullite Eramic/Ceramic Sample Joined by Phosphate Adhesive". Materials Science Forum 745-746 (luty 2013): 571–76. http://dx.doi.org/10.4028/www.scientific.net/msf.745-746.571.
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The aluminum phosphate adhesive was prepared by aluminum dihydrogen phosphate and ceramic fillers. The mullite, silica and silicon powders were added as the fillers to improve the mechanical property and high temperature property. The specimens were prepared by joining the mullite ceramic/ceramic by phosphate adhesive. The strengths of the specimens treated at different temperatures were studied. The results indicated that the tensile strength at room temperature was 2.02 MPa, and it reached 5.06 MPa when the specimen was treated at 800°C. The bonding effect and bonding property at high temperature were discussed through the SEM analysis. Besides, the bonding mechanism was also explored.
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Qian, Xi Kun, i Cong Cong Li. "Study of the Failure Mode of a Jointed Rock Mass due to a Stress Wave". Advances in Civil Engineering 2021 (15.07.2021): 1–12. http://dx.doi.org/10.1155/2021/1342691.
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The mechanical response and failure process of a jointed rock mass subjected to dynamic loading is very important for the safety and stability of rock engineering projects. In this study, we use RFPA2D-Dynamic, a rock dynamic failure process analysis platform, to establish a two-dimensional impact model of a jointed rock mass to analyze the mechanism of crack propagation in a jointed rock mass with preexisting cracks under dynamic loading. We discuss the influence of the stress wavelength and precrack inclination on the dynamic failure process and mode of the rock mass and compare this failure process with the failure model under static loading. The results show that the dynamic failure process and crack initiation type of a jointed rock mass are closely related to the stress wavelength. For a given peak, as the stress wavelength increases, the failure mode changes from local cracking that occurs above the precracks to a global instability caused by wing cracks. Meanwhile, as the wavelength increases, the shear cracks and mixed tensile-shear cracks generated at the two ends of the precracks are replaced by tensile cracks. The precrack inclination on a jointed rock mass mainly affects the strength of the jointed rock mass and the final failure mode. Specifically, when the joint inclination is small, the rock mass is severely damaged in the region above the precracks because the stress wave forms a region of cracks with a concentrated distribution. As the joint inclination increases, the damaged region becomes larger while the rock mass is less prone to failure; the strength of the rock mass gradually increases, and the wing cracks produced at the two ends of precracks propagate toward the upper and lower ends of the rock mass. However, when the stress wavelength is small, the precracks of different inclinations form cracks in the region above the precracks with a length similar to the precracks. For this condition, the propagation of the cracks is mainly controlled by the stress wavelength, while the influence of the inclination of the precracks is not significant. There is a significant difference between the failure modes of a rock specimen under dynamic loading or static loading because the stress wave produces a reflected tension wave in the direction parallel to the wave attack of the joint plane, which leads to spalling, while the wing cracks are more likely to occur under static loading.
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Brožek, M. "Soldering steel sheets using soft solders". Research in Agricultural Engineering 59, No. 4 (5.12.2013): 141–46. http://dx.doi.org/10.17221/7/2012-rae.
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The paper contains strength tests results of joints soldered using lead and leadless soft solders. For tests lead solders types Sn63Pb37, Sn60Pb40, Pb60Sn40 and Pb48Sn32Bi and leadless soft solders types Sn96Ag4, Sn99Cu1, Sn70Zn30 and Sn96Ag3Cu1 were used. As basic joint material steel sheet of 1.0 mm thickness and zinc-coated steel sheet of 1.0 mm thickness were used. The size of test specimen was 100 × 20 mm. Two sheets were always cleaned and jointed together. For heating the propane-butane plus air flame was used. The tested assemblies were loaded using the universal tensile-strength testing machine until their failure. At the tests the force needed for assemblies’ failure and failure type (in the soldered joint, in the basic material) was recorded and the solder strength was calculated from the measured data. The test results show that for soldering of steel sheets as well of zinc-coated steel sheets of 1.0 mm thickness the joints soldered using the lead soft solder type Sn63Pb37 and the leadless soft solder type Sn96Ag4 were of the highest strength.
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Cao, Ri Hong, Ping Cao, Pi Hua Wen i Rui Wen Chen. "Failure Characteristics of Rock-Like Material with Multi-Fissures under Uniaxial Compression". Applied Mechanics and Materials 711 (grudzień 2014): 129–32. http://dx.doi.org/10.4028/www.scientific.net/amm.711.129.
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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.
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Wasantha, P. L. P., P. G. Ranjith i Daniel R. Viete. "Specimen Slenderness and the Influence of Joint Orientation on the Uniaxial Compressive Strength of Singly Jointed Rock". Journal of Materials in Civil Engineering 26, nr 6 (czerwiec 2014): 06014002. http://dx.doi.org/10.1061/(asce)mt.1943-5533.0000907.
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