Multibody Dynamic Modeling Of The Linear Moving Medium

The linear moving medium is widely used in daily life and industry, such asaxial-moving tethers, cables, belts, beams and fluid-conveying pipes. Due to thecombination of the mass-variability and the flexibility of the linear moving medium, itis so difficult for dynamic modeling that none is acknowledged so far. According to thissituation, the thesis presented is committing to the dynamic modeling method mainlyincludes:1. Brought forward the material coordinate to characterize the mass moving of themedium and presented an element method of the linear moving medium byadopting the arbitrary Lagrange-Euler description and absolute nodal coordinateformulation. This paper assumes the medium as Euler-Bernoulli beam whichfurthermore adopts the absolute nodal coordinate formulation to describe thegeometrical nonlinearity when the medium is undergoing large displacement androtation. The dynamic equations are established by D'Alembert's principle forthe mass variable system. Since the medium element is length-variable, dynamicmeshing is brought in for the purpose of controlling the length of the element,thus ensure the quality of the element. This paper designed and implemented anidentity-period pendulum with the length-variable tether which is calculated byboth the numerical method and the analytical method whose results are almostthe same that the developed element is validated to be correct and reliable.2. Built a dynamic model of the sliding joint on the one-dimensional flexiblemedium with the discontinuity of the axial slope. In this model, the joint is based on thesliding node whose correlative elements are length-variable, so as to implement themoving of the joint by changing the length of the correlative elements. The paperadopted the modeling of the linear moving medium to take account of the flexiblemedium and build the model of the sliding joint by supplement of the constraintsbetween the moving system and the moved-on system. The dynamic meshing is alsoapplied in this model to control the length of the element. Some numerical samples arecarried out which all yield good precision to ensure the correctness and the reliability ofthe developed element.3. Presented an element method of the fluid-conveying pipe with large amplitude displacement and rotation. The fluid-pipe element merged the pipe structure, which isassumed as Euler-Bernoulli beam, and the flowing liquid, which is assumed asone-dimensional incompressible frictionless fluid, by sharing their nodalcoordinates. With the fluid-pipe element, the paper studied on the tubularcantilever conveying fluid. The critical fluid velocity and flutter frequencycalculated by this paper is so consistent with that by earlier literatures that thefluid-pipe element is validated to be correct in condition of small deformation at least.The motion of the tubular cantilever conveying fluid with high speed is studiedand the influence of the gravity is also discussed. Both of them generatedinteresting results.