In this paper,multi_quadric equations interpolation is used to establish a widely covered and valuable speed field model,with which the crustal movement image is obtained.
Traditional five-axis tool path planning methods mostly focus on differential geometric characteristics between the cutter and the workpiece surface to increase the material removal rate(i.e.,by minimizing path length...Traditional five-axis tool path planning methods mostly focus on differential geometric characteristics between the cutter and the workpiece surface to increase the material removal rate(i.e.,by minimizing path length,improving curvature matching,maximizing local cutting width,etc.) . However,material removal rate is not only related to geometric conditions such as the local cutting width,but also constrained by feeding speed as well as the motion capacity of the five-axis machine. This research integrates machine tool kinematics and cutter-workpiece contact kinematics to present a general kinematical model for five-axis machining process. Major steps of the proposed method include:(1) to establish the forward kinematical relationship between the motion of the machine tool axes and the cutter contact point;(2) to establish a tool path optimization model for high material removal rate based on both differential geometrical property and the contact kinematics between the cutter and workpiece;(3) to convert cutter orientation and cutting direction optimization problem into a concave quadratic planning(QP) model. Tool path will finally be generated from the underlying optimal cutting direction field. Through solving the time-optimal trajectory generation problem and machining experiment,we demonstrate the validity and effectiveness of the proposed method.展开更多
The evolution of wake structure in a flow around an impulsively stopped sphere in an incompressible viscous fluid is investigated under the influence of a streamwise magnetic field at moderate Reynolds numbers.The res...The evolution of wake structure in a flow around an impulsively stopped sphere in an incompressible viscous fluid is investigated under the influence of a streamwise magnetic field at moderate Reynolds numbers.The research parameter range is 600≤Re≤1400 and 0≤N≤10,where Re and N are the Reynolds number and the interaction parameter,respectively.A vortex ring system is developed,which contains the primary and secondary vortex rings after stopping the sphere.The flow will keep axisymmetric before stopping the sphere for the purpose to investigate the instability of shedding vortex rings.Without the magnetic field,an azimuthal instability will develop on the secondary vortex ring when the Reynolds number is large enough,e.g.,Re=1200.It is caused by the centrifugal movement of the secondary vortex ring and this instability can be suppressed by the streamwise magnetic field.Furthermore,an obvious oscillation caused by the motion of the primary vortex ring on the drag force is found after stopping the sphere.The amplitude of such oscillation increases with enlarging the Reynolds number but decreases with enlarging the magnetic field intensity.展开更多
文摘In this paper,multi_quadric equations interpolation is used to establish a widely covered and valuable speed field model,with which the crustal movement image is obtained.
基金supported by the National Basic Research Program of China ("973" Program) (Grant No. 2011CB706800)the National Natural Science Foundation of China (Grant No. 50835004)the National Funds for Distinguished Young Scientists of China (Grant No. 51025518)
文摘Traditional five-axis tool path planning methods mostly focus on differential geometric characteristics between the cutter and the workpiece surface to increase the material removal rate(i.e.,by minimizing path length,improving curvature matching,maximizing local cutting width,etc.) . However,material removal rate is not only related to geometric conditions such as the local cutting width,but also constrained by feeding speed as well as the motion capacity of the five-axis machine. This research integrates machine tool kinematics and cutter-workpiece contact kinematics to present a general kinematical model for five-axis machining process. Major steps of the proposed method include:(1) to establish the forward kinematical relationship between the motion of the machine tool axes and the cutter contact point;(2) to establish a tool path optimization model for high material removal rate based on both differential geometrical property and the contact kinematics between the cutter and workpiece;(3) to convert cutter orientation and cutting direction optimization problem into a concave quadratic planning(QP) model. Tool path will finally be generated from the underlying optimal cutting direction field. Through solving the time-optimal trajectory generation problem and machining experiment,we demonstrate the validity and effectiveness of the proposed method.
基金the National Natural Science Foundation of China(Grant No.52006212)Basic Frontier Science Research Program of Chinese Academy of Sciences(Grant No.ZDBS-LY-JSC033)+1 种基金Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB22040201)China Postdoctoral Science Foundation(Grant No.2019M650815).
文摘The evolution of wake structure in a flow around an impulsively stopped sphere in an incompressible viscous fluid is investigated under the influence of a streamwise magnetic field at moderate Reynolds numbers.The research parameter range is 600≤Re≤1400 and 0≤N≤10,where Re and N are the Reynolds number and the interaction parameter,respectively.A vortex ring system is developed,which contains the primary and secondary vortex rings after stopping the sphere.The flow will keep axisymmetric before stopping the sphere for the purpose to investigate the instability of shedding vortex rings.Without the magnetic field,an azimuthal instability will develop on the secondary vortex ring when the Reynolds number is large enough,e.g.,Re=1200.It is caused by the centrifugal movement of the secondary vortex ring and this instability can be suppressed by the streamwise magnetic field.Furthermore,an obvious oscillation caused by the motion of the primary vortex ring on the drag force is found after stopping the sphere.The amplitude of such oscillation increases with enlarging the Reynolds number but decreases with enlarging the magnetic field intensity.
