The ground penetrating radar(GPR) forward simulation all aims at the singular and regular models, such as sandwich model, round cavity, square cavity, and so on, which are comparably simple. But as to the forward of c...The ground penetrating radar(GPR) forward simulation all aims at the singular and regular models, such as sandwich model, round cavity, square cavity, and so on, which are comparably simple. But as to the forward of curl interface underground or “v” figure complex model, it is difficult to realize. So it is important to forward the complex geoelectricity model. This paper takes two Maxwell’s vorticity equations as departure point, makes use of the principles of Yee’s space grid model theory and the basic principle finite difference time domain method, and deduces a GPR forward system of equation of two dimensional spaces. The Mur super absorbed boundary condition is adopted to solve the super strong reflection on the interceptive boundary when there is the forward simulation. And a self-made program is used to process forward simulation to two typical geoelectricity model.展开更多
作为一种新型被动减振技术,颗粒阻尼已被应用于船舶、航空等领域。为进一步研究颗粒阻尼耗能机理,提高其减振性能,基于离散元(Discrete Element Method,DEM)-多体动力学(Multi Body Dynamic,MBD)耦合方法建立弹簧-颗粒阻尼减振系统模型...作为一种新型被动减振技术,颗粒阻尼已被应用于船舶、航空等领域。为进一步研究颗粒阻尼耗能机理,提高其减振性能,基于离散元(Discrete Element Method,DEM)-多体动力学(Multi Body Dynamic,MBD)耦合方法建立弹簧-颗粒阻尼减振系统模型,研究颗粒填充率及颗粒半径对系统减振效果的影响,并分析其耗能特性;通过试验验证DEM-MBD耦合仿真方法的准确性,等效阻尼比仿真值与试验值的平均误差为11.8%。研究结果表明:通过选择合适的填充比,可使弹簧-颗粒阻尼减振系统最大等效阻尼比比无颗粒时提高12.9倍。研究结果可为后续颗粒阻尼减振设计提供一定参考。展开更多
Shear-box test with strain measurement was used to study time-dependent stress and strain of in-plane shear(Mode Ⅱ) fracture process of rock and to reveal the mechanism of Mode Ⅱ fracture.Numerical results show that...Shear-box test with strain measurement was used to study time-dependent stress and strain of in-plane shear(Mode Ⅱ) fracture process of rock and to reveal the mechanism of Mode Ⅱ fracture.Numerical results show that the maximum shear stress τmax at the crack tip is much larger than the maximum tensile stress σ1 and the ratio of τmax/σ1 is about 5,which favors Mode Ⅱ fracture of rock.Test results indicate that the strain-time curve comprises three stages:the linear deformation stage,the micro-cracking stage and the macroscopic crack propagation.The strain in the direction of the original notch plane is negative,due to restraining effect of compressive loading applied to the original notch plane.Both σ1 and τmax are increased as the load increases,but the slope of τmax is larger than that of σ1 and the value of τmax is always larger than that of σ1.Therefore,τmax reaches its limited value at peak load before σ1 and results in Mode Ⅱ fracture of rock.Shear-box(i.e.compression-shear) test becomes a potential standard method for achieving the true Mode Ⅱ fracture and determining Mode Ⅱ fracture toughness of rock.展开更多
基金Project supported by China Postdoctoral Science Foundation （20100481488）, Key Fund Project of Advanced Research of the Weapon Equipment （9140A33040512JB3401）.
文摘The ground penetrating radar(GPR) forward simulation all aims at the singular and regular models, such as sandwich model, round cavity, square cavity, and so on, which are comparably simple. But as to the forward of curl interface underground or “v” figure complex model, it is difficult to realize. So it is important to forward the complex geoelectricity model. This paper takes two Maxwell’s vorticity equations as departure point, makes use of the principles of Yee’s space grid model theory and the basic principle finite difference time domain method, and deduces a GPR forward system of equation of two dimensional spaces. The Mur super absorbed boundary condition is adopted to solve the super strong reflection on the interceptive boundary when there is the forward simulation. And a self-made program is used to process forward simulation to two typical geoelectricity model.
文摘作为一种新型被动减振技术,颗粒阻尼已被应用于船舶、航空等领域。为进一步研究颗粒阻尼耗能机理,提高其减振性能,基于离散元(Discrete Element Method,DEM)-多体动力学(Multi Body Dynamic,MBD)耦合方法建立弹簧-颗粒阻尼减振系统模型,研究颗粒填充率及颗粒半径对系统减振效果的影响,并分析其耗能特性;通过试验验证DEM-MBD耦合仿真方法的准确性,等效阻尼比仿真值与试验值的平均误差为11.8%。研究结果表明:通过选择合适的填充比,可使弹簧-颗粒阻尼减振系统最大等效阻尼比比无颗粒时提高12.9倍。研究结果可为后续颗粒阻尼减振设计提供一定参考。
基金Project(50374073) supported by the National Natural Science Foundation of ChinaProject(1343-77239) supported by the GraduaEducation Innovation Project of Central South University,China
文摘Shear-box test with strain measurement was used to study time-dependent stress and strain of in-plane shear(Mode Ⅱ) fracture process of rock and to reveal the mechanism of Mode Ⅱ fracture.Numerical results show that the maximum shear stress τmax at the crack tip is much larger than the maximum tensile stress σ1 and the ratio of τmax/σ1 is about 5,which favors Mode Ⅱ fracture of rock.Test results indicate that the strain-time curve comprises three stages:the linear deformation stage,the micro-cracking stage and the macroscopic crack propagation.The strain in the direction of the original notch plane is negative,due to restraining effect of compressive loading applied to the original notch plane.Both σ1 and τmax are increased as the load increases,but the slope of τmax is larger than that of σ1 and the value of τmax is always larger than that of σ1.Therefore,τmax reaches its limited value at peak load before σ1 and results in Mode Ⅱ fracture of rock.Shear-box(i.e.compression-shear) test becomes a potential standard method for achieving the true Mode Ⅱ fracture and determining Mode Ⅱ fracture toughness of rock.
