機械專業(yè)外文翻譯--學習運用proengineer幾何模型建立有限元模型的過程-全文預(yù)覽
【正文】 onic databases can create traditional blueprints for manufacturing purposes, but can also transfer information electronically to puterized manufacturing processes and to finite element analysts. Potentially, this electronic transfer of information can save the analyst a significant amount of time in both steps 1 and 2. In addition , the mesh generation codes have also improved significantly in the last decade . Many different codes now have the capability of automatically generating shell meshes on general surfaces .and some have (or are close to having ) the ability to mesh generalshaped solids automatically with either tetrahedral or hexahedral elements. Because things are changing so quickly analysts and drafters may not have experience in how to best use these new tools .This study was undertaken to understand some of the mechanisms which would enhance the process of creating finite element models using today39。 and 2) axisymmetric structures, which may be adequately analyzed using a 2dimensional axisymmetric model representing the crosssection. In either recreating a geometry or using a solid geometry form Pro/ENGINEER, the analyst must know ahead of time what types of analyses are going to be required .This is dependent on the current state of mesh generation and analysis technology . for instance , current mesh generation technology only allows acceptable automatic mesh generation of general solid geometries using tetrahedral (tet) elements , even though hexahedral (hex) elements typically provide a better answer with fewer elements . Thus , if hex elements are required ,the analyst will have to modify the geometry provided from Pro/ENGINEER, to acmodate the nonautomatic mesh generation. In addition, tet elements tend to have problems even beyond their lower accuracy. Low order tet elements tend to exhibit shear locking and excessive stiffness, while higher order tet elements cannot be used in explicit analyses (dynamic analyses requiring very small time steps). So the analyst must choose the type of mesh generation based partly on the type of analysis. Another consideration is model size. Theredimensional models can very quickly bee too large to run either because of calculation time or memory size, both of which are limitations of the current generation of puters. A “small” 3dimensional mesh of 100x100x100 cells result in a model size of a million elements, while traditional finite element models to date have been less than 100,000 elements. Therefore, it is prudent wherever possible to model structures as 2dimensional, even when a 3dimensional calculation may yield more accurate results. This again may require modification of solid geometry provided from Pro/ENGINEER. A final consideration is that typically it takes much less time and effort for a drafter to “build” a Pro/ENGINEER model than it does for an analyst to “build” an analysis model. Therefore, it is reasonable (from an overall designtoanalysis process) to focus first on things which can be done in Pro/ENGINEER to facilitate the ana
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