In order to better study the dynamic characteristics and the control strategy of parafoil systems,considering the effect of flap deflection as the control mechanism and regarding the parafoil and the payload as a rigi...In order to better study the dynamic characteristics and the control strategy of parafoil systems,considering the effect of flap deflection as the control mechanism and regarding the parafoil and the payload as a rigid body,a six degrees-of-freedom(DOF)dynamic model of a parafoil system including three DOF for translational motion and three DOF for rotational motion,is established according to the K rchhoff motion equation.Since the flexible winged paafoil system flying at low altitude is more susceptibleto winds,the motion characteristics of the parafoil system Wth and Wthout winds are simulated and analyzed.Furthermore,the ardropm test is used to further verify the model.The comparison results show that the simulation trajectory roughly overlaps with the actual flight track.The horzontnl velocity of the simulation model is in good accordance with the airdrop test,with a deviation less than0.5m/s,while its simulated vertical velocity fuctuates slightly under the infuence of the wind,and shows a similar trend to the ardrop test.It is concludedthat the established model can well describe the characteristics of the parafoil system.展开更多
For the first time detailed measurements of the DOS （density of states） for Ti3AIC2 and Ti3SiC2 are presented at temperatures between T = 10 and 100 K. For Ti3AIC2 a DFT （density functional theory） simulation of l...For the first time detailed measurements of the DOS （density of states） for Ti3AIC2 and Ti3SiC2 are presented at temperatures between T = 10 and 100 K. For Ti3AIC2 a DFT （density functional theory） simulation of lattice dynamics is compared to experimental data demonstrating a noticeable difference between the spectra especially below 40 meV. In the case of Ti3SiC2 the DFT model is augmented with MD （molecular dynamics） simulations resulting in the measured and simulated spectra resembling one another more closely but still having significant differences below 40 meV. Within the experimental spectra, there are features up to and including 20 meV which are unaccounted for by the simulation. Tracing individual atoms generated by the computer models suggests anharmonic motion of Si within the Ti3SiC2. The results presented could explain differences between calculated elastic moduli using DFT harmonic lattice dynamics simulations and results from recent experiments.展开更多
This study presented the specified steps of comprehensively analyzing the hydraulic-driven hammer system with the application of the Virtual Prototype Technology.By comparing the simulation results with experimental p...This study presented the specified steps of comprehensively analyzing the hydraulic-driven hammer system with the application of the Virtual Prototype Technology.By comparing the simulation results with experimental phenomena and data,the correctness of simulation analysis conclusion is verified.Meanwhile,by means of its perfect visualization,the internal work process which can not be seen before is simulated.The mechanism of some abnormal phenomena encountered during the experiment is explained.展开更多
The stowing and deploying experiment was conducted for three 700 mm long thin-walled tubes,and the structural behavior characteristics parameters were measured clearly,including strain,deformation and wrapping moment....The stowing and deploying experiment was conducted for three 700 mm long thin-walled tubes,and the structural behavior characteristics parameters were measured clearly,including strain,deformation and wrapping moment.3D finite element models(FEM)were built subsequently and explicit dynamic method was used to simulate the stowing and deploying of the lenticular carbon fiber reinforced polymer(CFRP)thin-walled tubular space boom,which was designed as four-ply(45°/-45°/45°/-45°)lay-up.The stress and energy during the wrapping process were got and compared with different wrapping angular velocity,the reasonable wrapping angular velocity and effective method were conformed,and structural behavior characteristics were obtained.The results were compared and discussed as well,and the results show that the numerical results by 0.628 rad/s velocity agree well with the measured values.In this paper,the numerical procedure and experimental results are valuable to the optimization design of CFRP thin-walled tubular space boom and future research.展开更多
基金The National Natural Science Foundation of China(No.61273138,61573197)the National Key Technology R&D Program(No.2015BAK06B04)+1 种基金the Key Fund of Tianjin(No.14JCZDJC39300)the Key Technologies R&D Program of Tianjin(No.14ZCZDSF00022)
文摘In order to better study the dynamic characteristics and the control strategy of parafoil systems,considering the effect of flap deflection as the control mechanism and regarding the parafoil and the payload as a rigid body,a six degrees-of-freedom(DOF)dynamic model of a parafoil system including three DOF for translational motion and three DOF for rotational motion,is established according to the K rchhoff motion equation.Since the flexible winged paafoil system flying at low altitude is more susceptibleto winds,the motion characteristics of the parafoil system Wth and Wthout winds are simulated and analyzed.Furthermore,the ardropm test is used to further verify the model.The comparison results show that the simulation trajectory roughly overlaps with the actual flight track.The horzontnl velocity of the simulation model is in good accordance with the airdrop test,with a deviation less than0.5m/s,while its simulated vertical velocity fuctuates slightly under the infuence of the wind,and shows a similar trend to the ardrop test.It is concludedthat the established model can well describe the characteristics of the parafoil system.
文摘For the first time detailed measurements of the DOS （density of states） for Ti3AIC2 and Ti3SiC2 are presented at temperatures between T = 10 and 100 K. For Ti3AIC2 a DFT （density functional theory） simulation of lattice dynamics is compared to experimental data demonstrating a noticeable difference between the spectra especially below 40 meV. In the case of Ti3SiC2 the DFT model is augmented with MD （molecular dynamics） simulations resulting in the measured and simulated spectra resembling one another more closely but still having significant differences below 40 meV. Within the experimental spectra, there are features up to and including 20 meV which are unaccounted for by the simulation. Tracing individual atoms generated by the computer models suggests anharmonic motion of Si within the Ti3SiC2. The results presented could explain differences between calculated elastic moduli using DFT harmonic lattice dynamics simulations and results from recent experiments.
文摘This study presented the specified steps of comprehensively analyzing the hydraulic-driven hammer system with the application of the Virtual Prototype Technology.By comparing the simulation results with experimental phenomena and data,the correctness of simulation analysis conclusion is verified.Meanwhile,by means of its perfect visualization,the internal work process which can not be seen before is simulated.The mechanism of some abnormal phenomena encountered during the experiment is explained.
基金the National Natural Science Foundation of China(No.50878128)the Shanghai Aerospace Foundation(No.HTJ10-15)
文摘The stowing and deploying experiment was conducted for three 700 mm long thin-walled tubes,and the structural behavior characteristics parameters were measured clearly,including strain,deformation and wrapping moment.3D finite element models(FEM)were built subsequently and explicit dynamic method was used to simulate the stowing and deploying of the lenticular carbon fiber reinforced polymer(CFRP)thin-walled tubular space boom,which was designed as four-ply(45°/-45°/45°/-45°)lay-up.The stress and energy during the wrapping process were got and compared with different wrapping angular velocity,the reasonable wrapping angular velocity and effective method were conformed,and structural behavior characteristics were obtained.The results were compared and discussed as well,and the results show that the numerical results by 0.628 rad/s velocity agree well with the measured values.In this paper,the numerical procedure and experimental results are valuable to the optimization design of CFRP thin-walled tubular space boom and future research.
