| In the literature, the studies on powder compaction process modeling, simulation, and machine design are fragmented, and the behavior of the powdered material is oversimplified in the design process. Laboratory studies have shown that tooling profiles, including piston shape and the mold shape, are important factors affecting the quality of coal logs. However, no existing mathematical procedure can be used for analysis and design of these geometries.; The purpose of this study is to develop a practical and predictive compaction model, and to integrate the system model into the compaction machine design process. The axisymmetric nonlinear finite element model developed herein includes the log in the mold, the tooling (mold and pistons), and the friction at the interfaces between log and mold. Material characteristics of the logs were measured and derived from experimental data. An object-oriented procedure was developed to implement the mathematical model for computer simulation of the compaction process. The finite elements and their behavior were represented by Enhanced Entity Relationships (EER). The resulting computer code was used to determine the stress and the deformation of the coal log, pistons and the mold, and the coal-log density distribution during both compaction and ejection processes. The cause of capping and laminating which damage the coal log was studied, and a sensitivity analysis was performed for optimizing the design of the piston shape and the mold shape to avoid compaction defects.; Partial results of this study have been used in a 250-ton high speed hydraulic press. The machine was constructed for rapid manufacturing of high quality coal logs in a 5.4" (137 mm) diameter mold. The machine is able to generate pressure as high as 20,000 psi (138 MPa) in the mold, and the compaction piston moves as fast as 15" (381 mm) per second. The overall designs of the machine, including the mechanical structure, the hydraulic power and control system, are described. An integrated design synthesis procedure developed in the design process is also presented. Improvements to the tooling designs are recommended by using sensitivity-analysis results. |
