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基于第一性原理提出了自动构建计算构型-自动提交计算任务-智能分析计算数据的固体界面摩擦性能自动化计算方法,并通过并发-并行同时计算约1 000个计算任务,实现了固体界面摩擦性能的高通量计算. 以石墨烯/石墨烯滑动体系为例,测试了高通量计算方法的可靠性. 结果表明:通过该方法计算的势能面与文献中使用传统方法计算的势能面一致,摩擦系数也与试验结果相符合,从而验证了该方法的可靠性. 该方法能够极大地节约科研人员使用第一性原理研究固体界面摩擦性能所需的时间. 相似文献
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计算固结系数的方法很多, 它们各有千秋, 但无论哪种都不能计算土体在任意固结时刻的固结系数。本文把几种计算方法的优点结合起来, 找到了-种计算任意固结时刻固结系数的新方法, 并用室内系列固结实验数据进行了计算。现场观测资料分析计算结果与之对比结果表明, 该方法行之有效。 相似文献
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炸药爆轰性质计算的氮当量公式及修正氮当量公式:炸药爆速的计算 总被引:1,自引:0,他引:1
在本文中,提出了炸药爆速计算的氮当量公式和修正氮当量公式及其计算方法,并进行实例计算。讨论了炸药的氮当量(修正氮当量)与爆热及爆容的关系,探讨了提高爆速的途径。本方法与其它计算方法对比表明,氮当量公式是简便,适用范围广、不需要生成热并有一定准确性的计算方法。修正氮当量公式不但具有上述优点,而且还是最准确的计算方法之一。 相似文献
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本文较详细地介绍了惩罚线性规划的数学原理,建立了确定杆系结构的极限载荷与载荷的最佳分布的数学模型。根据以上原理与模型对桁架、刚架与扳架作了实例计算。计算结果与使用其它方法之结果完全一致。本文介绍的方法具有计算数据准备工作简单,计算时间较少等优点,为杆系结构极限分析提供了一个有效的方法。 相似文献
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改进的直接部件模态综合法 总被引:1,自引:0,他引:1
Yee和Tsuei提出的直接部件模态综合法将自由界面模态综合法与频响函数相结合 ,简化了计算过程、减少了计算量 ,并便于与实验模态分析相结合。本文在其基础上利用矩阵级数展开的方法将被截断高阶模态的贡献用保留模态和系统物理特性矩阵精确表达 ,结合分块计算方法 ,进一步减少了计算量并有效地提高了计算精度 ,且确定了模态截断准则。数值算例表明其行之有效 相似文献
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In a previous publication, procedures that can be used with the absolute nodal coordinate formulation to solve the dynamic problems of flexible multibody systems were proposed. One of these procedures is based on the Cholesky decomposition. By utilizing the fact that the absolute nodal coordinate formulation leads to a constant mass matrix, a Cholesky decomposition is used to obtain a constant velocity transformation matrix. This velocity transformation is used to express the absolute nodal coordinates in terms of the generalized Cholesky coordinates. The inertia matrix associated with the Cholesky coordinates is the identity matrix, and therefore, an optimum sparse matrix structure can be obtained for the augmented multibody equations of motion. The implementation of a computer procedure based on the absolute nodal coordinate formulation and Cholesky coordinates is discussed in this paper. Numerical examples are presented in order to demonstrate the use of Cholesky coordinates in the simulation of the large deformations in flexible multibody applications. 相似文献
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多柔体系统是由柔性部件和运动副组成的力学系统,在航空、航天、车辆、机械与兵器等众多工程领域具有广泛的应用前景, 其典型的代表包括柔性机械臂、直升机旋翼、卫星的可展开天线、太阳帆航天器等. 近年来,随着工程技术的发展,多柔体系统动力学问题日益突出,尤其是含变长度柔性部件的多柔体系统,不仅涉及其动力学 建模与计算,还涉及其动力学优化设计. 事实上,部件柔性对多柔体系统的动力学行为影响很大,直接影响到优化结果,因此需要发展基于多柔体系统动力学的优化设计方法. 本文首先阐述了多柔体系统动力学优化的研究背景及意义,简要回顾了多柔体系统动力学建模的3类方法:浮动坐标方法、几何 精确方法和绝对节点坐标方法,并介绍了含变长度柔性部件的多柔体系统动力学建模方法. 系统概述了多柔体系统动力学响应优化、动力学特性优化和动力学灵敏度分析3个方面的研究进展,并从尺寸优化、形状优化和 拓扑优化 3 个方面综述了多柔体系统部件优化的研究进展. 本文最后提出了在多柔体系统动力学优化研究中值得关注的若干问题. 相似文献
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Computer Implementation of the Absolute Nodal Coordinate Formulation for Flexible Multibody Dynamics 总被引:8,自引:0,他引:8
Deformable components in multibody systems are subject to kinematic constraints that represent mechanical joints and specified motion trajectories. These constraints can, in general, be described using a set of nonlinear algebraic equations that depend on the system generalized coordinates and time. When the kinematic constraints are augmented to the differential equations of motion of the system, it is desirable to have a formulation that leads to a minimum number of non-zero coefficients for the unknown accelerations and constraint forces in order to be able to exploit efficient sparse matrix algorithms. This paper describes procedures for the computer implementation of the absolute nodal coordinate formulation' for flexible multibody applications. In the absolute nodal coordinate formulation, no infinitesimal or finite rotations are used as nodal coordinates. The configuration of the finite element is defined using global displacement coordinates and slopes. By using this mixed set of coordinates, beam and plate elements can be treated as isoparametric elements. As a consequence, the dynamic formulation of these widely used elements using the absolute nodal coordinate formulation leads to a constant mass matrix. It is the objective of this study to develop computational procedures that exploit this feature. In one of these procedures, an optimum sparse matrix structure is obtained for the deformable bodies using the QR decomposition. Using the fact that the element mass matrix is constant, a QR decomposition of a modified constant connectivity Jacobian matrix is obtained for the deformable body. A constant velocity transformation is used to obtain an identity generalized inertia matrix associated with the second derivatives of the generalized coordinates, thereby minimizing the number of non-zero entries of the coefficient matrix that appears in the augmented Lagrangian formulation of the equations of motion of the flexible multibody systems. An alternate computational procedure based on Cholesky decomposition is also presented in this paper. This alternate procedure, which has the same computational advantages as the one based on the QR decomposition, leads to a square velocity transformation matrix. The computational procedures proposed in this investigation can be used for the treatment of large deformation problems in flexible multibody systems. They have also the advantages of the algorithms based on the floating frame of reference formulations since they allow for easy addition of general nonlinear constraint and force functions. 相似文献
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多柔体系统动力学主要研究由多个具有运动学约束、存在大范围相对运动的柔性部件构成的动力学系统的建模、计算和控制.多柔体系统不仅具有柔体大变形导致的几何非线性,更具有大范围刚体运动引起的几何非线性,其非线性程度远高于计算结构力学所研究的几何非线性问题.本文基于李群局部标架(local frame of Lie group, LFLG),讨论如何发展一套新的多柔体系统动力学建模和计算方法体系, 具体内容包括:基于局部标架的梁、板壳单元,适用于长时间历程计算的多柔体系统碰撞动力学积分算法,结合区域分解技术的大规模多柔体系统动力学并行求解器, 以及若干验证性算例.上述基于李群局部标架的方法体系可在计算中消除刚体运动带来的几何非线性问题,使柔体系统的广义惯性力、广义弹性力及其雅可比矩阵满足刚体运动的不变性,使多柔体系统动力学与大变形结构力学相互统一,有望推动新一代多柔体系统动力学建模和计算软件的发展. 相似文献
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柔性多体系统动力学实验研究综述 总被引:4,自引:0,他引:4
介绍了国内外柔性多体系统动力学实验研究现状,分为三个方面,即理论模型验证实验、动力学特性的实验研究和其它实验.柔性多体系统动力学建模理论的发展经历了3个阶段:运动-弹性动力学(KED)方法、传统混合坐标方法和计及了动力刚化效应的各种非线性理论.关于这些理论的模型验证实验均在本文中作了重点介绍.文中还对柔性多体系统动力学性态的研究实验也作了介绍,包括系统模态特性和共振等非线性力学行为.关于机械臂控制和碰撞研究实验虽有提及,但不作为重点.随后,着重介绍了柔性体弹性振动位移的测量和阻尼因素的处理这两个在实验不可避免但又难以解决的问题,尤其是结构阻尼和大范围运动引起的空气阻力.最后指出了今后的研究方向.文中对一些较为重要的实验装置也着重予以介绍,并给出了部分实验图片及数据曲线,以给读者一个更好的理解和参考. 相似文献
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In this paper, nonlinear modeling for flexible multibody system with large deformation is investigated. Absolute nodal coordinates
are employed to describe the displacement, and variational motion equations of a flexible body are derived on the basis of
the geometric nonlinear theory, in which both the shear strain and the transverse normal strain are taken into account. By
separating the inner and the boundary nodal coordinates, the motion equations of a flexible multibody system are assembled.
The advantage of such formulation is that the constraint equations and the forward recursive equations become linear because
the absolute nodal coordinates are used. A spatial double pendulum connected to the ground with a spherical joint is simulated
to investigate the dynamic performance of flexible beams with large deformation. Finally, the resultant constant total energy
validates the present formulation.
The project supported by the National Natural Science Foundation of China (10472066, 10372057). The English text was polished
by Yunming Chen. 相似文献
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The modelling of flexible elements in mechanical systems has been investigated via several methods issuing from both the field of multi-body dynamics and the area of structural mechanics and vibration theory. As regards the multibody approach, recursive formulations in relative coordinates are quite suitable and efficient for a large variety of applications. Such a formalism is developed here for a general multibody system containing flexible plates and in such a way that its full symbolic generation is possible within the ROBOTRAN program [1]. 相似文献
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完全笛卡尔坐标描述的多体系统动力学 总被引:18,自引:0,他引:18
用完全笛卡尔坐标描述多体系统的运动学和动力学在提高计算效率方面有突出优点.导出用完全笛卡尔坐标表示的刚体及多体系统的动量和动量矩的解析式,给出与之对应的广义惯量矩阵概念,建立无力矩状态下用完全笛卡尔坐标描述的多体系统动力学的一阶微分方程组,用于多体航天器的姿态运动分析 相似文献
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柔性机械臂系统逆动力学及驱动规律的研究 总被引:1,自引:0,他引:1
研究了柔性机械臂系统的逆动力学问题及其联接铰驱规律。在柔性多体系统动力学单向递推组集建模方法的基础上,建立了树形及含闭环的柔性多体系统正逆动力学问题同时计算的等价公式。通过一空间机械臂的数值仿真,讨论了构件的柔性效应对系统的驱动力(矩)及实际运动规律的影响。 相似文献