Papers by Author: Di Li

Abstract: Feature recognition is the key technology in establishing auto body panel CAPP system. Hole features and draw boss features has been classified according to their forming and function properties in this paper. Recognition algorithms have been developed for hole feature and drawing boss feature, which can also distinguish two dimensional hole and three dimensional hole, and differentiate circle hole and non circle hole automatically. The algorithms can also recognize the drawing bosses and judge whether the boss has holes. Furthermore, the algorithms can give out the parameters of hole and drawing boss recognized, such as radius of circle hole, minimum radius of curvature of shaped hole’ boundaries, the parameters of hole in the drawing boss, the edges’ ID of the hole and the surfaces’ ID of the boss.

Abstract: The finite element method has been extensively used to predict forming difficulties of die forging problems. However, the analysis for die forging problems with finite element method can lose considerable accuracy due to severely distortional meshes. Based on the equality of elements, an automatically coupling algorithm has been proposed to analyze die forging problems, which converts the FE analysis into the EFG computation to preserve the accuracy in the region where meshes have been severely distorted and still employs the FE method to ensure high computational efficiency in the region where the quality of the FE meshes is acceptable. Numerical example shows that the present algorithms exploit the respective advantages of both the FE method whose computational efficiency is high and the EFG method which can throws out mesh distortions.

Abstract: The analysis for rigid plastic forming problems with finite element method can lose considerable accuracy due to severely distortional meshes. By measuring the mesh equality of elements, a coupling algorithm for rigid plastic problems have been proposed based on the interface element method, which converts the FE analysis into the EFG computation to preserve the accuracy in the region where meshes have been severely distorted. Numerical example shows that the present algorithms exploit the respective advantages of both the FE method whose computational efficiency is high and the EFG method which can throws out mesh distortions and be suitable for rigid plastic forming analysis.

Abstract: Feature recognition is the key technology in establishing auto body panel CAPP system. For regular parts, it has made great achievements in features recognition, which has laid a foundation for feature recognition for complex shape parts, such as auto body panels. This paper has classified holes feature into two-dimensional holes, three-dimensional holes and special holes according to its forming and function properties, and established process expression mode of holes feature on account of the requirement of CAPP system. Algorithms have been developed for holes feature recognition based on recognition rules making use of geometric features of holes’ boundary in UG software, two-dimensional holes and three-dimensional holes can be automatically distinguished, circle holes and non circle holes can also be differentiated automatically, further more, the algorithms can give radius of circle hole and minimum radius of curvature of shaped hole’ boundaries.

Abstract: The analysis for die forging forming problems with finite element method can lose considerable accuracy due to severely distortional meshes. The element-free Galerkin method is suitable for large deformation analysis and provides a higher rate of convergence than that of the conventional finite element methods. A rigid-plastic meshless method based on the element-free Galerkin method has been applied to die forging problems. The arc-tangent friction model is used to handle frictional contact and the penalty method is applied to impose the volumetric incompressibility conditions. By dividing all integration points set into the point subset of the rigid zones and the point subset of the plastic zones, nonsmoothness of the rigid-plastic constitutive relation can be eliminated. A die forging example has been analyzed to demonstrate the performance of the method.

Abstract: Based on the interface element method, a coupling algorithm for the large deformation problems has been proposed, which converts the FE analysis into the MLPG computation to preserve the accuracy in the region where meshes have been severely distorted. Numerical example shows that the present method exploits the respective advantages of both the FE method whose computational efficiency is high and the MLPG method which is suitable for large deformation.