基于密度泛函理论的第一性原理的Vienna Ab initio Simulation Package(VASP)软件系统研究了Mg7TMH16(TM=Sc,Ti,V,Y,Zr,Nb)的晶体结构和电子性能.分析了结合能和形成焓,计算得到的结合能显示Mg7TiH16和Mg7NbH16的稳定性最强,形成焓的变...基于密度泛函理论的第一性原理的Vienna Ab initio Simulation Package(VASP)软件系统研究了Mg7TMH16(TM=Sc,Ti,V,Y,Zr,Nb)的晶体结构和电子性能.分析了结合能和形成焓,计算得到的结合能显示Mg7TiH16和Mg7NbH16的稳定性最强,形成焓的变化表明Mg7TMH16具有比MgH2更低的分解温度,电子态密度显示Mg7TMH16表现出明显的金属特性.展开更多
The pre-burying iron sheets approach was used to prepare rock-like materials with ordered multiple pre-cracks. 60 specimens in total were prepared in these experiments. Through biaxial compression experiments, the inf...The pre-burying iron sheets approach was used to prepare rock-like materials with ordered multiple pre-cracks. 60 specimens in total were prepared in these experiments. Through biaxial compression experiments, the influence of both the number of pre-cracks and pre-cracks angles to crack growth was analyzed. Meanwhile, species of rock bridge failure were summarized, namely, wing crack, secondary shear crack between horizontal pre-cracks and secondary shear crack between vertical pre-cracks. The wing crack plays a significant role in crack growth. Furthermore, fractal dimension was adopted to describe quantitatively the crack growth during the failure process. The results indicate that with the failure of specimens, corresponding fractal dimension for specimen monotonically increases, which indicates that the fractal dimension can be considered to the failure of the specimens quantitatively.展开更多
Combined with numerical simulation, the influence of confining stress on cutting process, fracture conditions and cutting efficiencies of soft and hard rock has been conducted on the triaxial testing machine(TRW-3000)...Combined with numerical simulation, the influence of confining stress on cutting process, fracture conditions and cutting efficiencies of soft and hard rock has been conducted on the triaxial testing machine(TRW-3000) designed and manufactured in Central South University(China). Results are obtained by performing analysis on the fracture scopes of cement and granite plates,the characteristics of cutting force in cutting processes and the cutting efficiency. Firstly, the increase of latitude fracture scope and the decrease of longitude fracture scope are both more notable in the tests conducted on cement plates subjected to the increasing confining stresses; secondly, the increase tendency of peak penetration forces obtained from tests conducted on granite plates is more obvious, however, the increase tendencies of average penetration forces achieved from cement and granite plates are close to each other; thirdly, the cutting efficiency could be improved by increasing the spacing between cutters when the confining stress which acts on soft and hard rock increases in a certain degree, and the cutting efficiency of soft rock is more sensitive to the varying confining stresses.展开更多
Based on the triaxial testing machine and discrete element method, the effects of embedded crack on rock fragmentation are investigated in laboratory tests and a series of numerical investigations are conducted on the...Based on the triaxial testing machine and discrete element method, the effects of embedded crack on rock fragmentation are investigated in laboratory tests and a series of numerical investigations are conducted on the effects of discontinuities on cutting characteristics and cutting efficiency. In laboratory tests, five propagation patterns of radial cracks are observed. And in the numerical tests, firstly, it is similar to laboratory tests that cracks ahead of cutters mainly initiate from the crushed zone, and some minor cracks will initiate from joints. The cracks initiating from crushed zones will run through the thinner joints while they will be held back by thick joints. Cracks tend to propagate towards the tips of embedded cracks, and minor cracks will initiate from the tips of embedded cracks, which may result in the decrease of specific area, and disturbing layers play as ‘screens', which will prevent cracks from developing greatly. The peak penetration forces, the consumed energy in the penetration process and the uniaxial compression strength will decrease with the increase of discontinuities. The existence of discontinuities will result in the decrease of the cutting efficiency when the spacing between cutters is 70 mm. Some modifications should be made to improve the efficiency when the rocks containing groups of discontinuities are encountered.展开更多
文摘基于密度泛函理论的第一性原理的Vienna Ab initio Simulation Package(VASP)软件系统研究了Mg7TMH16(TM=Sc,Ti,V,Y,Zr,Nb)的晶体结构和电子性能.分析了结合能和形成焓,计算得到的结合能显示Mg7TiH16和Mg7NbH16的稳定性最强,形成焓的变化表明Mg7TMH16具有比MgH2更低的分解温度,电子态密度显示Mg7TMH16表现出明显的金属特性.
基金Project(E21527)supported by the Open Research Fund Program of Hunan Provincial Key Laboratory of Shale Gas Resource Utilization,ChinaProject(2015zzts077)supported by the Fundamental Research Funds for the Central Universities,China+1 种基金Projects(51174088,51174228)supported by the National Natural Science Foundation of ChinaProject(2013CB035401)supported by the National Basic Research Program of China
文摘The pre-burying iron sheets approach was used to prepare rock-like materials with ordered multiple pre-cracks. 60 specimens in total were prepared in these experiments. Through biaxial compression experiments, the influence of both the number of pre-cracks and pre-cracks angles to crack growth was analyzed. Meanwhile, species of rock bridge failure were summarized, namely, wing crack, secondary shear crack between horizontal pre-cracks and secondary shear crack between vertical pre-cracks. The wing crack plays a significant role in crack growth. Furthermore, fractal dimension was adopted to describe quantitatively the crack growth during the failure process. The results indicate that with the failure of specimens, corresponding fractal dimension for specimen monotonically increases, which indicates that the fractal dimension can be considered to the failure of the specimens quantitatively.
基金Project(2013CB035401)supported by the National Basic Research Program of ChinaProject(51174228)supported by the National Natural Science Foundation of China+1 种基金Project(201304)supported by Open Research Fund of Hunan Province Key Laboratory of Safe Mining Techniques of Coal Mines(Hunan University of Science and Technology),ChinaProject(14C0746)supported by the Education Department of Hunan Province,China
文摘Combined with numerical simulation, the influence of confining stress on cutting process, fracture conditions and cutting efficiencies of soft and hard rock has been conducted on the triaxial testing machine(TRW-3000) designed and manufactured in Central South University(China). Results are obtained by performing analysis on the fracture scopes of cement and granite plates,the characteristics of cutting force in cutting processes and the cutting efficiency. Firstly, the increase of latitude fracture scope and the decrease of longitude fracture scope are both more notable in the tests conducted on cement plates subjected to the increasing confining stresses; secondly, the increase tendency of peak penetration forces obtained from tests conducted on granite plates is more obvious, however, the increase tendencies of average penetration forces achieved from cement and granite plates are close to each other; thirdly, the cutting efficiency could be improved by increasing the spacing between cutters when the confining stress which acts on soft and hard rock increases in a certain degree, and the cutting efficiency of soft rock is more sensitive to the varying confining stresses.
基金Project(2013CB035401) supported by the National Basic Research Program of ChinaProject(51174228) supported by the National Natural Science Foundation of China+1 种基金Project(71380100003) supported by Hunan Provincial Innovation Foundation for Postgraduate,ChinaProject(201304) supported by Open Research Fund of Hunan Province Key Laboratory of Safe Mining Techniques of Coal Mines(Hunan University of Science and Technology),China
文摘Based on the triaxial testing machine and discrete element method, the effects of embedded crack on rock fragmentation are investigated in laboratory tests and a series of numerical investigations are conducted on the effects of discontinuities on cutting characteristics and cutting efficiency. In laboratory tests, five propagation patterns of radial cracks are observed. And in the numerical tests, firstly, it is similar to laboratory tests that cracks ahead of cutters mainly initiate from the crushed zone, and some minor cracks will initiate from joints. The cracks initiating from crushed zones will run through the thinner joints while they will be held back by thick joints. Cracks tend to propagate towards the tips of embedded cracks, and minor cracks will initiate from the tips of embedded cracks, which may result in the decrease of specific area, and disturbing layers play as ‘screens', which will prevent cracks from developing greatly. The peak penetration forces, the consumed energy in the penetration process and the uniaxial compression strength will decrease with the increase of discontinuities. The existence of discontinuities will result in the decrease of the cutting efficiency when the spacing between cutters is 70 mm. Some modifications should be made to improve the efficiency when the rocks containing groups of discontinuities are encountered.
