In this study,the dynamic stress concentration factors(DSCF)around a straight-wall arch tunnel(SWAT)were solved analytically utilizing the complex variable function methods and Duhamel’s integral.The effects of wavel...In this study,the dynamic stress concentration factors(DSCF)around a straight-wall arch tunnel(SWAT)were solved analytically utilizing the complex variable function methods and Duhamel’s integral.The effects of wavelength,incident angle,and blasting rising time on the DSCF distribution were analyzed.Theoretical results pointed out dynamic disturbances resulting in compressive stress concentration in the vertical direction and tensile stress in the incident direction.As the wavelength and rising time increased,there was a tendency for the amplitude of stress concentration to initially rise and then converge.Moreover,a series of 3D FEM models were established to evaluate the effect of different initial stress states on the dynamic failure of the tunnel surrounding rock.The results indicated that the failure of the surrounding rock was significantly influenced by the direction of the static maximum principal stress and the direction of the dynamic disturbance.Under the coupling of static and blasting loading,damage around the tunnel was more prone to occur in the dynamic and static stress concentration coincidence zone.Finally,the damage modes of rock tunnel under static stress and blasting disturbance from different directions were summarized and a proposed support system was presented.The results reveal the mechanisms of deep-buried rock tunnel destruction and dynamically triggered rockburst.展开更多
Tensile tests with small deformation amounts of 0.5%,1%,3%and 5%were performed at room temperature on as cast Mg-1%Al alloy.Microstructures of the Mg-1%Al alloys before and after deformation were observed by optical m...Tensile tests with small deformation amounts of 0.5%,1%,3%and 5%were performed at room temperature on as cast Mg-1%Al alloy.Microstructures of the Mg-1%Al alloys before and after deformation were observed by optical microscopy(OM) and transmission electron microscopy(TEM).The strain amplitude dependent and temperature dependent damping capacities of the as-cast and deformed Mg-1%Al alloys were investigated by dynamic mechanical analysis(DMA).The mechanism of deformation on damping capacity of Mg-1%Al alloy was discussed.The results show that the as-cast Mg-1%Al alloy has high damping value at high strain.When the tensile elongation is higher than 3%,the damping values of this alloy in high strain region are significantly decreased at room temperature.But the large amount of dislocations produced by tensile deformation are activated by heat,and then increase the damping value at high temperature.展开更多
The whole analysis process of pneumatic stressed membrane structure contains nine states and seven analysis processes.The zero-stress state is the corner-stone of analysis and design of pneumatic stressed structure,an...The whole analysis process of pneumatic stressed membrane structure contains nine states and seven analysis processes.The zero-stress state is the corner-stone of analysis and design of pneumatic stressed structure,and has significant impact on the pre-stressed state and load state.According to the logical model of the whole numerical analysis process of pneumatic stressed structure,a numerical analysis method to solve the zero-stress state from the elasticized equilibrium state was firstly proposed,called linear compatibility matrix M-P inverse method.Firstly,the pneumatic membrane stressed structure was transferred into grid structure by using membrane link to simulate membrane surface.Secondly,on the basis of equilibrium matrix theory of pin joint structure and small deformation assumption,compatibility equation of system was established.Thirdly,the unstressed length and elongation of links were calculated from the tension and material parameters of elasticized equilibrium state.Finally,using compatibility matrix M-P inverse,the nodal displacement was calculated by solving compatibility equation,the configuration of zero-stress state could be obtained through reverse superposition,and the stress was released.According to the algorithm,the program was coded with MATLAB.The correctness and efficiency of this method were verified by several numerical examples,and it could be found that one elasticized equilibrium state corresponded to one configuration of the zero-stress state.The work has theoretical significance and practical guidance value for pneumatic membrane structural design.展开更多
基金Project(12072376)supported by the National Natural Science Foundation of ChinaPoject(10533220215858)supported by the Fundamental Research Funds for the Central Universities,China。
文摘In this study,the dynamic stress concentration factors(DSCF)around a straight-wall arch tunnel(SWAT)were solved analytically utilizing the complex variable function methods and Duhamel’s integral.The effects of wavelength,incident angle,and blasting rising time on the DSCF distribution were analyzed.Theoretical results pointed out dynamic disturbances resulting in compressive stress concentration in the vertical direction and tensile stress in the incident direction.As the wavelength and rising time increased,there was a tendency for the amplitude of stress concentration to initially rise and then converge.Moreover,a series of 3D FEM models were established to evaluate the effect of different initial stress states on the dynamic failure of the tunnel surrounding rock.The results indicated that the failure of the surrounding rock was significantly influenced by the direction of the static maximum principal stress and the direction of the dynamic disturbance.Under the coupling of static and blasting loading,damage around the tunnel was more prone to occur in the dynamic and static stress concentration coincidence zone.Finally,the damage modes of rock tunnel under static stress and blasting disturbance from different directions were summarized and a proposed support system was presented.The results reveal the mechanisms of deep-buried rock tunnel destruction and dynamically triggered rockburst.
基金Project(50801017)supported by the National Natural Science Foundation of ChinaProject(20080440843)supported by China Postdoctoral Science FoundationProject(HIT.NSRIF.2009028)supported by Natural Scientific Research Innovation Foundation in Harbin Institute of Technology,China
文摘Tensile tests with small deformation amounts of 0.5%,1%,3%and 5%were performed at room temperature on as cast Mg-1%Al alloy.Microstructures of the Mg-1%Al alloys before and after deformation were observed by optical microscopy(OM) and transmission electron microscopy(TEM).The strain amplitude dependent and temperature dependent damping capacities of the as-cast and deformed Mg-1%Al alloys were investigated by dynamic mechanical analysis(DMA).The mechanism of deformation on damping capacity of Mg-1%Al alloy was discussed.The results show that the as-cast Mg-1%Al alloy has high damping value at high strain.When the tensile elongation is higher than 3%,the damping values of this alloy in high strain region are significantly decreased at room temperature.But the large amount of dislocations produced by tensile deformation are activated by heat,and then increase the damping value at high temperature.
基金supported by the National Natural Science Foundation of China (Grant Nos. 50878128, 50808122)
文摘The whole analysis process of pneumatic stressed membrane structure contains nine states and seven analysis processes.The zero-stress state is the corner-stone of analysis and design of pneumatic stressed structure,and has significant impact on the pre-stressed state and load state.According to the logical model of the whole numerical analysis process of pneumatic stressed structure,a numerical analysis method to solve the zero-stress state from the elasticized equilibrium state was firstly proposed,called linear compatibility matrix M-P inverse method.Firstly,the pneumatic membrane stressed structure was transferred into grid structure by using membrane link to simulate membrane surface.Secondly,on the basis of equilibrium matrix theory of pin joint structure and small deformation assumption,compatibility equation of system was established.Thirdly,the unstressed length and elongation of links were calculated from the tension and material parameters of elasticized equilibrium state.Finally,using compatibility matrix M-P inverse,the nodal displacement was calculated by solving compatibility equation,the configuration of zero-stress state could be obtained through reverse superposition,and the stress was released.According to the algorithm,the program was coded with MATLAB.The correctness and efficiency of this method were verified by several numerical examples,and it could be found that one elasticized equilibrium state corresponded to one configuration of the zero-stress state.The work has theoretical significance and practical guidance value for pneumatic membrane structural design.
