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弹体贯穿钢筋混凝土数值模拟   总被引:13,自引:0,他引:13  
详细描述了依据损伤原理建立的连续损伤模型,并对该模型进行了改进。在LS-DYNA程序用户自定义材料模型中加入改进的连续损伤模型,并对弹体侵彻钢筋混凝土的穿孔过程进行了数值模拟,其结果与实验结果相吻合,模型可以用于钢筋混凝土的动态破坏预报。  相似文献
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Based on the equations which describe the dynamic behavior of material under high-velocity and high-pressure shock, corresponding equations at shock front whose surface is general space curve surface were established. For concrete material, a normal expansion theory was proposed by which some deceleration about time history of the projectile can be analytically given. This normal expansion theory is not only suitable for spherical and cylindrical-nose projectile, but also suitable for other general nose projectile, for example conical nose or ogive-nose. And it is not only suitable for perpendicular shock but also for oblique shock.  相似文献
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IntroductionInengineering,thenonlinearityofshellstructureissometimesobvious.Itisverydifficulttosolvetheproblemofthenonlinearrandomvibration .Inthispaper,wetrytosolveitinthefrequencydomainbyanimprovedstatisticlinearizationmethod .Weconsideronlythegeometr…  相似文献
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本文在765~1766m/s速度范围内,对钨纤维体积分数为80%的增强锆(Zr)基块体金属玻璃复合材料长杆弹进行侵彻Q235钢靶的穿甲试验,对残余弹体进行宏、细观观测,研究弹体材料的失效破坏模式。穿甲试验表明,在大于1000m/s速度侵彻时,钨纤维非晶弹拥有头形自锐能力,表现出优秀的侵彻能力。弹材变形和破坏主要发生于弹体头部边缘层,呈局域化和尖锐化特点,而且边缘层厚度在整个高速穿甲过程中保持动态平衡。由于非晶基体作用,弹体材料易发生剪切断裂等破坏,通过流动形成质量侵蚀并导致弹体头部边缘层形成自锐。  相似文献
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Nonlinear controllability and attitude stabilization are studied for the underactuated nonholonomic dynamics of a rigid spacecraft with one variable-speed control moment gyro(VSCMG), which supplies only two internal torques.Nonlinear controllability theory is used to show that the dynamics are locally controllable from the equilibrium point and thus can be asymptotically stabilized to the equilibrium point via time-invariant piecewise continuous feedback laws or time-periodic continuous feedback laws. Specifically,when the total angular momentum of the spacecraft-VSCMG system is zero, any orientation can be a controllable equilibrium attitude. In this case, the attitude stabilization problem is addressed by designing a kinematic stabilizing law, which is implemented through a nonlinear proportional and derivative controller, using the generalized dynamic inverse(GDI)method. The steady-state instability inherent in the GDI controller is elegantly avoided by appropriately choosing control gains. In order to obtain the command gimbal rate and wheel acceleration from control torques, a simple steering logic is constructed to accommodate the requirements of attitude stabilization and singularity avoidance of the VSCMG. Illustrative numerical examples verify the efcacy of the proposed control strategy.  相似文献
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For an underactuated spacecraft using only one thruster,the attitude controllability with respect to the orbit frame is studied in the presence of periodical oscillation disturbance,which provides a preconditional guide on designing control law for underactuated attitude control system.Firstly,attitude dynamic model was established for an underactuated spacecraft,and attitude motion was described using the special orthogonal group(SO(3)).Secondly,Liouville theorem was used to confirm that the flow generated by the drift vector of the underactuated attitude control system is volume-preserving.Furthermore,according to Poincare’’s recurrence theorem,we draw conclusions that this drift field is weakly positively poisson stable(WPPS).Thirdly,the sufficient and necessary condition of controllability was obtained on the basis of lie algebra rank condition(LARC).Finally,the controllable conditions were analyzed and simulated in different cases of inertia matrix with the installed position of thruster.  相似文献
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An improved constrained (IC) steering law for single gimbal control moment gyros (SGCMGs) with deformed pyramid configuration (DPC) is proposed, First of all, the original system with five pyramid configuration (FPC) whose two adjacent gyros are in failure state is reconfigured as a degraded system with DPC. Then, the singular angular momentum hypersurfaces of the original and the degraded systems are plotted via the singular angular momentum equa- tion of SGCMGs. Based on singular surfaces, the differences between FPC and DPC in singularity and momentum envelope are obtained directly, which provide an important reference for steering law design of DPC. Finally, an IC steering law is designed and applied to DPC. The simulation results demonstrate that the IC steering law has advantages in simplicity of calculation, avoidance of singularity and exactness of output torque, which endow the degraded system with fine controllability in a restricted workspace.  相似文献
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Angular velocity stabilization control and attitude stabilization control for an underactuated spacecraft using only two single gimbal control moment gyros (SGCMGs) as actuators is investigated. First of all, the dynamic model of the underactuated spacecraft is established and the singularity of different configurations with the two SGCMGs is analyzed. Under the assumption that the gimbal axes of the two SGCMGs are installed in any direction, and that the total system angular momentum is not zero, a state feedback control law via Lyapunov method is designed to globally asymptotically stabilize the angular velocity of spacecraft. Under the assumption that the gimbal axes of the two SGCMGs are coaxially installed along anyone of the three principal axes of spacecraft inertia, and that the total system angular momentum is zero, a discontinuous state feedback control law is designed to stabilize three-axis attitude of spacecraft with respect to the inertial frame. Furthermore, the singularity escape of SGCMGs for the above two control problems is also studied. Simulation results demonstrate the validity of the control laws.  相似文献
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