Water content and primary fractures can change the mechanical characteristics of rock,making it easy to induce geological disasters.Therefore,direct shear tests of red sandstone under the action of water-fracture were...Water content and primary fractures can change the mechanical characteristics of rock,making it easy to induce geological disasters.Therefore,direct shear tests of red sandstone under the action of water-fracture were carried out in this paper.The results show that shear strength of rock samples with fractures is less than that of intact rock samples.With the increase of primary fracture dip angle,shear strength and macroscopic crushing area of the rock sample increases first and then decreases with 20°as the boundary.It shows that the primary fractures weaken the shear mechanical properties and change the macroscopic failure mode.The shear performance of water-bearing rock samples is weaker than that of intact rock samples,and the weakening degree of water-saturated on shear performance of rock samples is lower than that of unsaturated water state.The fracture surfaces of rock samples are divided into‘shortest path single through type’,‘longest path single through type’and‘cross path through type’.The failured rock samples are divided into‘single through type’and‘cross through type’.The research results can provide reference for geological disaster management under relevant conditions.展开更多
Deep geothermal extraction processes expose rock masses to frequent and significant temperature fluctuations. Developing a comprehensive understanding of the shear fracture mechanisms and crack propagation behaviors i...Deep geothermal extraction processes expose rock masses to frequent and significant temperature fluctuations. Developing a comprehensive understanding of the shear fracture mechanisms and crack propagation behaviors in rocks under the influence of cyclic heating is imperative for optimizing geothermal energy extraction. This study encompasses several critical aspects under cyclic heating conditions, including the assessment of stress distribution states, the characterization of two-dimensional fracture paths, the quantitative analysis of three-dimensional damage characteristics on fracture surfaces, and the determination of the fractal dimension of debris generated after the failure of granite. The test results demonstrate that cyclic heating has a pronounced adverse effect on the physical and mechanical properties of granite. Consequently, stress tends to develop and propagate in a direction perpendicular to the two-dimensional fracture path. This leads to an increase in the extent of tensile damage on the fracture surface and accelerates the overall rock failure process. This increases the number of small-sized debris, raises the fractal dimension, and enhances the rock’s rupture degree. In practical enhanced geothermal energy extraction, the real-time monitoring of fracture propagation within the reservoir rock mass is achieved through the analysis of rock debris generated during the staged fracturing process.展开更多
The static and fatigue properties of 7B04 aluminum alloy structures connected by riveting and refill friction stir spot welding(refill FSSW)were compared and analyzed.Results show that the static compression load of t...The static and fatigue properties of 7B04 aluminum alloy structures connected by riveting and refill friction stir spot welding(refill FSSW)were compared and analyzed.Results show that the static compression load of the typical structure connected by riveting and refill FSSW fluctuated in the range of 117-124 kN,and the shear load was in the range of 89-95 kN.Welds spacing had a small influence on the static load of the structures joined by refill FSSW.However,the fatigue life of riveted structures was lower than that joined by refill FSSW.For the welded structure,the heterogeneous microstructures of the welded joint led to the uneven microhardness,and the hook at the lap interface bent upwards at the same time.These factors made the welded structures during the fatigue test failure along the path of sleeve moving.展开更多
In this paper, several widely applied fracture criteria were first numerically examined and the crack-tip-region Jntegral criterion was confirmed to be more applicable to predict fracture angle in an elastic-plastic m...In this paper, several widely applied fracture criteria were first numerically examined and the crack-tip-region Jntegral criterion was confirmed to be more applicable to predict fracture angle in an elastic-plastic multiphase material. Then, the crack propagation in an idealized an elastic-plastic finite element method. The variation dendritic two-phase AI-7%Si alloy was modeled using of crack growth driving force with crack extension was also demonstrated. It is found that the crack path is significantly influenced by the presence of α-phase near the crack tip, and the crack growth driving force varies drastically from place to place. Lastly, the simulated fracture path in the two-phase model alloy was compared with the experimentally observed fracture path.展开更多
An attempt to investigate the mechanical response to the torsional load, torsional tests of TiA1/steel brazed joints were conducted at room temperature. The TiAl/steel joints used in the torsional loading tests were b...An attempt to investigate the mechanical response to the torsional load, torsional tests of TiA1/steel brazed joints were conducted at room temperature. The TiAl/steel joints used in the torsional loading tests were brazed under the optimum parameters of 1 173 K and 300 s. Torsional strength, fracture path and the behavior of the reaction phases were studied. The results show that the average torsional strength of the joints with the diameters of 13mm, 16 mm and 20 mm is 136 N · m, 270 N · m and 490 N · m, respectively; which is 81.9% , 85.5% and 86. 2% of the TiAl base metal, respectively. Fracture path and crack propagation process analysis shows, when subjected to the torsional load, Ag-based solid solution is deformed and cracks germinate at the interface of Ag-based solid solutioa/AlCu2 Ti particles or Ag-based solid solution/AlCu2 Ti layers, grow up and propagate into the Al-Cu- Ti brittle reaction layers, then propagate into the TiAl base metal, subsequently result in failure.展开更多
基金supported by the National Natural Science Foundation of China(52004147,51974173)Natural Science Foundation of Shandong Province(ZR2020QE129).
文摘Water content and primary fractures can change the mechanical characteristics of rock,making it easy to induce geological disasters.Therefore,direct shear tests of red sandstone under the action of water-fracture were carried out in this paper.The results show that shear strength of rock samples with fractures is less than that of intact rock samples.With the increase of primary fracture dip angle,shear strength and macroscopic crushing area of the rock sample increases first and then decreases with 20°as the boundary.It shows that the primary fractures weaken the shear mechanical properties and change the macroscopic failure mode.The shear performance of water-bearing rock samples is weaker than that of intact rock samples,and the weakening degree of water-saturated on shear performance of rock samples is lower than that of unsaturated water state.The fracture surfaces of rock samples are divided into‘shortest path single through type’,‘longest path single through type’and‘cross path through type’.The failured rock samples are divided into‘single through type’and‘cross through type’.The research results can provide reference for geological disaster management under relevant conditions.
基金Project(52409132) supported by the National Natural Science Foundation of ChinaProject(ZR2024QE018) supported by the Natural Science Foundation of Shandong Province,China+2 种基金Project(BK20240431) supported by Basic Research Program of Jiangsu,ChinaProject(SNKJ2023A07-R14) supported by the Major Key Technical Research Projects of Shandong Energy Group,ChinaProject(2024M751813) supported by China Postdoctoral Science Foundation。
文摘Deep geothermal extraction processes expose rock masses to frequent and significant temperature fluctuations. Developing a comprehensive understanding of the shear fracture mechanisms and crack propagation behaviors in rocks under the influence of cyclic heating is imperative for optimizing geothermal energy extraction. This study encompasses several critical aspects under cyclic heating conditions, including the assessment of stress distribution states, the characterization of two-dimensional fracture paths, the quantitative analysis of three-dimensional damage characteristics on fracture surfaces, and the determination of the fractal dimension of debris generated after the failure of granite. The test results demonstrate that cyclic heating has a pronounced adverse effect on the physical and mechanical properties of granite. Consequently, stress tends to develop and propagate in a direction perpendicular to the two-dimensional fracture path. This leads to an increase in the extent of tensile damage on the fracture surface and accelerates the overall rock failure process. This increases the number of small-sized debris, raises the fractal dimension, and enhances the rock’s rupture degree. In practical enhanced geothermal energy extraction, the real-time monitoring of fracture propagation within the reservoir rock mass is achieved through the analysis of rock debris generated during the staged fracturing process.
文摘The static and fatigue properties of 7B04 aluminum alloy structures connected by riveting and refill friction stir spot welding(refill FSSW)were compared and analyzed.Results show that the static compression load of the typical structure connected by riveting and refill FSSW fluctuated in the range of 117-124 kN,and the shear load was in the range of 89-95 kN.Welds spacing had a small influence on the static load of the structures joined by refill FSSW.However,the fatigue life of riveted structures was lower than that joined by refill FSSW.For the welded structure,the heterogeneous microstructures of the welded joint led to the uneven microhardness,and the hook at the lap interface bent upwards at the same time.These factors made the welded structures during the fatigue test failure along the path of sleeve moving.
文摘In this paper, several widely applied fracture criteria were first numerically examined and the crack-tip-region Jntegral criterion was confirmed to be more applicable to predict fracture angle in an elastic-plastic multiphase material. Then, the crack propagation in an idealized an elastic-plastic finite element method. The variation dendritic two-phase AI-7%Si alloy was modeled using of crack growth driving force with crack extension was also demonstrated. It is found that the crack path is significantly influenced by the presence of α-phase near the crack tip, and the crack growth driving force varies drastically from place to place. Lastly, the simulated fracture path in the two-phase model alloy was compared with the experimentally observed fracture path.
基金This work was supported by the National Natural Science Foundation of China （ No. 50975062）, the Science Foundation of Educational Department of Jiangxi Province （ No. GJJ13064）.
文摘An attempt to investigate the mechanical response to the torsional load, torsional tests of TiA1/steel brazed joints were conducted at room temperature. The TiAl/steel joints used in the torsional loading tests were brazed under the optimum parameters of 1 173 K and 300 s. Torsional strength, fracture path and the behavior of the reaction phases were studied. The results show that the average torsional strength of the joints with the diameters of 13mm, 16 mm and 20 mm is 136 N · m, 270 N · m and 490 N · m, respectively; which is 81.9% , 85.5% and 86. 2% of the TiAl base metal, respectively. Fracture path and crack propagation process analysis shows, when subjected to the torsional load, Ag-based solid solution is deformed and cracks germinate at the interface of Ag-based solid solutioa/AlCu2 Ti particles or Ag-based solid solution/AlCu2 Ti layers, grow up and propagate into the Al-Cu- Ti brittle reaction layers, then propagate into the TiAl base metal, subsequently result in failure.
