Adaptive refinement of all-hexahedral elements for three-dimensional metal forming analysis

In many 3-D forging simulations, the master-grid method or uniform-grid method is adopted as an effect tool for hexahedral element mesh generation, because the method is robust and reliable to construct the intermediate mesh during forging simulation. However, almost equal-sized element mesh is employed regardless of the local characteristics of the deforming region. In order to overcome this drawback, a new refinement technique for hexahedral element mesh is proposed by selecting the element regions to be refined and iteratively inserting the zero-thickness element layers into the necessary interfaces of elements. To generate refined mesh adaptive to the gradient of physical property or to the complexity of geometry, the desired mesh density is obtained from the ZZ–ZZ posteriori error analysis. In the course of expanding and smoothing the refined mesh to ensure the desired mesh density, the weighting factor based on mesh density of neighbor entities is introduced to the conventional Laplacian smoothing method. Comparative simulations of the selected forging processes have shown that the proposed refinement technique is effective from the viewpoint of computational economy of computations and accuracy.