Riccati discrete time transfer matrix method for elastic beam undergoing large overall motion

An efficient method for dynamics simulation for elastic beam with large overall spatial motion and nonlinear deformation, namely, the Riccati discrete time transfer matrix method (Riccati-DT-TMM), is proposed in this investigation. With finite segments, continuous deformation field of a beam can be decomposed into many rigid bodies connected by rotational springs. Discrete time transfer matrices of rigid bodies and rotational springs are used to analyze the dynamic characteristic of the beam, and the Riccati transform is used to improve the numerical stability of discrete time transfer matrix method of multibody system dynamics. A predictor-corrector method is used to improve the numerical accuracy of the Riccati-DT-TMM. Using the Riccati-DT-TMM in dynamics analysis, the global dynamics equations of the system are not needed and the computation time required increases linearly with the system’s number of degrees of freedom. Three numerical examples are given to validate the method for the dynamic simulation of a geometric nonlinear beam undergoing large overall motion.     

抽油杆减震器的碟形弹簧系统动力学仿真研究

弹性元件"增载压缩,卸载即恢复"的特性来储存能量和释放能量原理是防抽油杆疲劳断裂和脱扣的有效途径之一,但目前只有定性研究.定量研究抽油杆减震器中的蝶形弹簧组成的多体动力学系统,并建立了动力学方程.采用Fortran语言编程进行了动力学仿真,证明了抽油杆减震器可以有效地降低抽油杆作用于抽油机系统的附加动载荷,从而降低抽油机系统对抽油杆的位移激励,进而有效地避免抽油杆的脱扣和断裂.计算机仿真结果与现场试验结果相一致,定量研究为抽油杆减震器在工程中的应用提供了理论支持.     

An integrated system for computer aided design and analysis of multibody systems

An integrated system for design and analysis of multibody systems has been developed and is described in this paper. The use of the system is demonstrated through the example provided. The system consists of a commercially available CAD program and a multibody system analysis code developed at the Royal Institute of Technology in Stockholm, These tools are integrated using a relational database, the structure of which was developed at Luleå University of Technology, in order to get a complete system for design and analysis of multibody systems. The main gains from the integrated system are the possibilities of using calculated component data like mass and moment of inertia from the CAD program in the simulation models, the automatic formulation of input files for the analysis code, and finally the visualization of simulation results using the surface data of the solid models. The interactive structured query language (ISQL) of the database management system provides the possibility of examining the components of the multibody system during the design work and before any simulation is performed.     

基于多体动力学的深海开采装备虚拟样机设计及仿真

深海资源开发项目是我国根据《联合国海洋公约法》的规定在北太平洋克拉里昂一克林帕顿断裂带所拥有的7．5万Km^2的商业资源开采权。项目具有开发周期长、涉及装备多且复杂、开发费用高、涉及知识领域多和参加单位多等特点，采用虚拟样机技术进行开采装备设计和虚拟开采符合我国的国情，也是利用信息化技术改造我国传统装备设计水平和     

Designing waste rock barriers by advanced numerical modelling

Design of waste rock barriers forming safety berms for haul trucks requires knowledge of complex interactions which cannot readily be tested by physical means. An advanced numerical model based on non-smooth multi-domain mechanics is presented together with model calibration using limited full-scale experimental data. Waste rock is represented by spherical particles with rolling resistance, and an ultra-class haul truck is represented by a rigid multibody system interconnected with mechanical joints. The model components are first calibrated and then the calibrated model is used for simulating various collision scenarios with different approach conditions and safety berm geometries. Numerical predictions indicate that the width of the berm is most critical for efficiently stopping a runaway truck. The model can also predict if a certain berm geometry is capable of stopping a runaway truck. Results are summarised in a series of diagrams intended for use as design guidelines by practitioners and engineers.     

Advances in numerical computation based mechanical system design and simulation

This paper highlights the available numerical computation techniques in mechanical engineering field with focus on application of modeling and simulation within renewable energy conversion machines as a particular research case.The study makes special focus on simulation approaches based on finite elements and multibody dynamics that are currently focused within the research community.Developing the simulation model in a computer-aided design(CAD)tool is a precondition for a successful simulation-based mechanical system research.The article discusses and elaborates the methods implemented to integrate design data with other computer-aided engineering functions.The motivation is the fact that simulation-based research is useful for design optimization of mechanical systems that operate in harsh and unfriendly environment where conducting physical testing of prototypes is difficult.In addition,the manufacturing environment is benefiting from the developments in numerical computation techniques through machining simulation that significantly reduce the time-to-market and thus increase competitiveness.The study is also intended to explore the existing gaps of capabilities in current approaches in application of computational techniques in order to draw attention to future challenges and trends.     

Numerical and experimental investigations on new jar designs for high efficiency planetary ball milling

The internal shape of planetary ball mill jars was modified to increase the efficiency of the milling process. Four new jar designs are presented, where obstacles on the surface of a traditional cylindrical jar modify the ratio of normal-to-tangential transferred mechanical action, thus improving the comminution of the mill charge and reducing the process time. Multibody dynamics simulations, validated by operando video recordings of the process, were employed to investigate modified ball motion regimes promoting the increase of the number of high-energy impacts. Moreover, experimental grinding of calcium fluoride powder was performed to assess the effect of milling time and jar-to-plate velocity ratio, through the evaluation of size and microstrain of the end product deduced from X-ray diffraction line profile analysis.     

多体系统动力学软件技术

本文根据凯恩－休斯顿多体系统动力学理论,开发了一套计算机分析软件,重点描述了该软件的实现技术,最后给出了例题计算。     

On the optimal scaling of index three DAEs in multibody dynamics

We propose a preconditioning strategy for the governing equations of multibody systems in index-3 differential-algebraic form. The method eliminates the amplification of errors and the ill-conditioning which affect numerical solutions of high index differential algebraic equations for small time steps. We develop a new theoretical analysis of the perturbation problem and we apply it to the derivation of preconditioners for the Newmark family of integration schemes. The theoretical results are confirmed by numerical experiments.