New method for handling roof of the base successive mining is proposed, which is induction caving in the roof. The key is that it is made certain to the station of the space-time in the induction caving roof, as the s...New method for handling roof of the base successive mining is proposed, which is induction caving in the roof. The key is that it is made certain to the station of the space-time in the induction caving roof, as the stress is released with the mining process. And applying the catastrophe theory, the influencing factors of induction caving roof are studied in the emptied areas, such as the mechanical property of the surrounding rock, the area of the gob,the scope and dimension of tensile stress. The results show that the key factor is the area of the gob to the method of the induction caving roof. Then according to the geology and the ore characteristic, the three dimension FEM mechanical model is built in Tongkeng Mine, the laws of the tensile stress are analyzed to the space and the time in the roof with the mining, then it is rational design to the mine step and time of the handing the roof.展开更多
Pre-driven longwall retracement roadway(PLRR)is commonly used in large mine shaft.The support crushing disasters occur frequently during the retracement,and roof management is necessary.Taking the 31107 panel as resea...Pre-driven longwall retracement roadway(PLRR)is commonly used in large mine shaft.The support crushing disasters occur frequently during the retracement,and roof management is necessary.Taking the 31107 panel as research background,the roof breaking structure of PLRR is analyzed.It is concluded that the roof cutting with vertical hydraulic fracture(HF)at a specified position,that is,fixed-length roof cutting,can reduce support load and keep immediate roof intact.The extended finite element method(XFEM)is applied to simulate hydraulic fracturing.The results show that both the axial and transverse hydraulic fracturing cannot effectively create vertical HFs.Therefore,a novel construction method of vertical HF based on the stress shadow effect(SSE)is proposed.The stress reversal region and HF orientation caused by the prefabricated hydraulic fracture(PF)are verified in simulation.The sub-vertical HFs are obtained between two PFs,the vertical extension range of which is much larger than that of directional hydraulic fracturing.The new construction method was used to determine the field plan for fixed-length roof cutting.The roof formed a stable suspended structure and deformation of the main PLRR was improved after hydraulic fracturing.展开更多
The forming of sheet metal in a desired and attractive shape is a process that requires an understanding of materials, mechanics and manufacturing principles. Manufacturing a consistent sheet metal component is challe...The forming of sheet metal in a desired and attractive shape is a process that requires an understanding of materials, mechanics and manufacturing principles. Manufacturing a consistent sheet metal component is challenging due to the nonlinear interactions of various material and process parameters. One of the major issues in the manufacturing of inconsistent?sheet metal?parts is springback. Springback is the elastic strain recovery in the material after the tooling is removed and the final shape of the product depends on the springback amount formed. In this study according to the result of simulation the inverted compensation method is adopted to optimize die surface design. Similarly, to predict and compensate the springback error this study presented an analytical approach of forming process in a stepwise modification of the automobile roof panel. Moreover, based on?Dynaform?and?finite element analysis of sheet metal stamping simulation the sprinback in automobile roof panel is predicted and compensated.?In addition, this study examines the significant requirements of the sheet metal forming precision of automobile body and the simulation of forming, stamping and springback of automobile roof panel is carried out, and the result of simulation also is analyzed.展开更多
Based on the characteristics of membrane structures and the air influence factors,this paper presented a method to simulate the air aerodynamic force effects including the added air mass,the acoustic radiation damping...Based on the characteristics of membrane structures and the air influence factors,this paper presented a method to simulate the air aerodynamic force effects including the added air mass,the acoustic radiation damping and the pneumatic stiffness.The infinite air was modeled using the acoustic fluid element of commercial FE software and the finite element membrane roof models were coupled with fluid models.A comparison between the results obtained by FE computation and those obtained by the vibration experiment for a cable-membrane verified the validity of the method.Furthermore,applying the method to a flat membrane roof structure and using its wind tunnel test results,the analysis of nonlinear wind-induced dynamic responses for such geometrically nonlinear roofs,including the roof-air coupled model was performed.The result shows that the air has large influence on vibrating membrane roofs according to results of comparing the nodal time-history displacements,accelerations and stress of the two different cases.Meantime,numerical studies show that the method developed can successfully solve the nonlinear wind-induced dynamic response of the membrane roof with aerodynamic effects.展开更多
基金Project(50490274) supported by the National Nature Science Foundation of China
文摘New method for handling roof of the base successive mining is proposed, which is induction caving in the roof. The key is that it is made certain to the station of the space-time in the induction caving roof, as the stress is released with the mining process. And applying the catastrophe theory, the influencing factors of induction caving roof are studied in the emptied areas, such as the mechanical property of the surrounding rock, the area of the gob,the scope and dimension of tensile stress. The results show that the key factor is the area of the gob to the method of the induction caving roof. Then according to the geology and the ore characteristic, the three dimension FEM mechanical model is built in Tongkeng Mine, the laws of the tensile stress are analyzed to the space and the time in the roof with the mining, then it is rational design to the mine step and time of the handing the roof.
基金financially supported by the Postgraduate Research&Practice Innovation Program of Jiangsu Province(KYCX21_2358)the National Key Research and Development Program of China(2020YFB1314204)National Natural Science Foundation of China(No.52074239)。
文摘Pre-driven longwall retracement roadway(PLRR)is commonly used in large mine shaft.The support crushing disasters occur frequently during the retracement,and roof management is necessary.Taking the 31107 panel as research background,the roof breaking structure of PLRR is analyzed.It is concluded that the roof cutting with vertical hydraulic fracture(HF)at a specified position,that is,fixed-length roof cutting,can reduce support load and keep immediate roof intact.The extended finite element method(XFEM)is applied to simulate hydraulic fracturing.The results show that both the axial and transverse hydraulic fracturing cannot effectively create vertical HFs.Therefore,a novel construction method of vertical HF based on the stress shadow effect(SSE)is proposed.The stress reversal region and HF orientation caused by the prefabricated hydraulic fracture(PF)are verified in simulation.The sub-vertical HFs are obtained between two PFs,the vertical extension range of which is much larger than that of directional hydraulic fracturing.The new construction method was used to determine the field plan for fixed-length roof cutting.The roof formed a stable suspended structure and deformation of the main PLRR was improved after hydraulic fracturing.
文摘The forming of sheet metal in a desired and attractive shape is a process that requires an understanding of materials, mechanics and manufacturing principles. Manufacturing a consistent sheet metal component is challenging due to the nonlinear interactions of various material and process parameters. One of the major issues in the manufacturing of inconsistent?sheet metal?parts is springback. Springback is the elastic strain recovery in the material after the tooling is removed and the final shape of the product depends on the springback amount formed. In this study according to the result of simulation the inverted compensation method is adopted to optimize die surface design. Similarly, to predict and compensate the springback error this study presented an analytical approach of forming process in a stepwise modification of the automobile roof panel. Moreover, based on?Dynaform?and?finite element analysis of sheet metal stamping simulation the sprinback in automobile roof panel is predicted and compensated.?In addition, this study examines the significant requirements of the sheet metal forming precision of automobile body and the simulation of forming, stamping and springback of automobile roof panel is carried out, and the result of simulation also is analyzed.
文摘Based on the characteristics of membrane structures and the air influence factors,this paper presented a method to simulate the air aerodynamic force effects including the added air mass,the acoustic radiation damping and the pneumatic stiffness.The infinite air was modeled using the acoustic fluid element of commercial FE software and the finite element membrane roof models were coupled with fluid models.A comparison between the results obtained by FE computation and those obtained by the vibration experiment for a cable-membrane verified the validity of the method.Furthermore,applying the method to a flat membrane roof structure and using its wind tunnel test results,the analysis of nonlinear wind-induced dynamic responses for such geometrically nonlinear roofs,including the roof-air coupled model was performed.The result shows that the air has large influence on vibrating membrane roofs according to results of comparing the nodal time-history displacements,accelerations and stress of the two different cases.Meantime,numerical studies show that the method developed can successfully solve the nonlinear wind-induced dynamic response of the membrane roof with aerodynamic effects.
