jagabian为负
在挤压模拟时，有时网格重划进行不下去，计算自动终止，提示信息为“Negative Jagabian.......”#s'Y(J O N请问怎样才能避免这种情况的发生? DEFORM uses the finite element method to solve problems of large deformation and AMG (Automatic Mesh Generator) to automatically provide an optimized remeshing capability. In most cases, the meshing and remeshing runs very smoothly. There are cases though, where a simulation will not continue due to a negative Jacobian (unacceptable mesh) at a step immediately after a remeshing operation. In most cases, these can be easily identified from one of the following areas: O;l2R1` ` i
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Ÿ A closed forging lap will usually lead to this problem. Look at your progressions carefully and see is there is a small area where a lap has formed and closed. If such a lap is detected and you would like to continue the simulation, you may try to 4V^&\C b a I
Using the Surface Patch feature in the Preprocessor under Objects Geometry can be useful. Folds will appear as short red lines that do not appear to highlight a single element. Be sure to view the object from multiple angles before deciding that a red mark is a fold, because surface patches from the far side of the object can be misleading. 4|vC/f wV@
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Modify the geometry to remove the lap, and continue the simulation. This will require remeshing and interpolation to maintain the strain, temperature and damage history
Ÿ If, for any reason, a node has penetrated one of the dies, the remeshing will become problematic. This can be evaluated by looking at the FEM MESH of all objects at the step just prior to remeshing. A node that is inside the die surface will move back to the die surface after remeshing and interpolation of boundary conditions, but an element that had an acceptable geometry can be highly distorted during this process.
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Ÿ If the user sets a problem with very large time steps, and little to no substepping criteria, this can lead to a problem resulting from a mesh distorting severely during the first step. Refer to time step definition criteria in the preprocessor section of this manual.
Ÿ If substepping is disabled in a 3D simulation, great care must be taken to use sufficiently small time steps. This means that any time a node displacement calculates a node position inside a rigid object, the node is pushed back to the die surface. This is not a bad assumption if the node displacements are small, however, if the node displacements are large this assumption may lose its validity. *E/mhF,Tl"o&v
These suggestions are intended as general guidelines and may not solve all of this class of problem. If all of these areas have been investigated and subsequent attempts to run your problem fail, we would recommend sending us a keyword file for further investigation. I had met the same problem during the calculation. Nevertheless, remeshing had never been successfully done once.
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