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10 FINITE ELEMENT ANALYSIS
Igor Kokcharov 袋鼠的英语怎么说
摊手10.1 FINITE ELEMENT METHOD
The theories of elasticity, plasticity, plates and other analytical theories can be ud to solve many engineering problems. Frequently, practical engineering problems cannot be solved analytically due to complexity of the structure's geometry and boundary conditions. The simple examples given in A, B and C can be solved to obtain inner stress and displacements with analytical methods. More complicated geometries such as the propeller in example D is usually treated with a numerical method such as finite element method (FEM).
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FEM is applied in the following manner:
1. Identify the problem, sketch the structure and loads.
2. Create the geometry with the FE package solid modeler or a CAD system.
3. Mesh the model. 四人斗地主两副牌玩法
4. Apply boundary conditions (constraints and loads) on the model. 对话吧
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5. Solve numerical equations.
6. Evaluate the results.
吃什么补肺养肺Steps 1, 2, 3, 4 are known as preprocessing, the solution of equations in step 5 is the processor and step 6 is considered postprocessing.
The FE model is normally subdivided into finite elements of a specific and simple shape. A typical 3D finite element may be a brick or a wedge with nodes reprenting the vertices. The displacement of the element is determined by nodal displacements and simple polynomial shape functions that describe the assigned shape of the element. The strains and stress are calculated by the unknown nodal displacements. Once the nodal displacements are known, element stress and strains can be calculated.
The most difficult and lengthy step of FEM is the preprocessing, or creating the finite element model. This step includes defining and generating the mesh and applying the correct loading and displacement boundary conditions. Automatic meshing is not always simple, especially in very small features or at the edges and corners. It can be difficult to apply boundary conditions that correspond to the real situation. However, FEM solvers that process the equations in step 5 work automatically and can be rather fast depending on the number of nodes. Powerful and robust visualization tools can allow for a very thorough analysis in step 6.
