Stresses State and Mechanical Behaviors of the Green Body During Die Compaction and Ejection Process

doi:10.1007/s40195-020-01018-y

Abstract

Abstract:

Finite element simulations for metal powder compaction of a clutch plate were performed to examine the stresses during compaction, unloading, and ejection. To describe the mechanical behavior of compacted green body, a modified density-dependent Drucker-Prager Cap model was utilized to predict the stress and density distribution of the compacted clutch plate during loading and ejection stages. The results indicate that maximum tensile principal stress was a main driving force for the tensile crack initiation during ejection stage, and shear stress may be another driving force in both compaction and ejection stages for shear crack initiation. There were peak value of the stresses during ejection stage, and the stresses are in compressive state only during compaction stage. Therefore, the tensile crack initiation is not possible during compaction except shear crack. Hoop stress in the clutch plate is of less contribution to the crack initiation during compaction, unloading and ejection. Study of criteria of the crack initiation and fracture is necessary in order to obtain uniform density and crack-free components in the manufacturing of metal powder compaction.

Key words: Powder compaction, Finite element simulation, Stress history, Cap model, Green body

S. M. Wang, Y. Wang, Y. X. Wang, F. P. Liu, J. Cao. Stresses State and Mechanical Behaviors of the Green Body During Die Compaction and Ejection Process[J]. Acta Metallurgica Sinica (English Letters), 2020, 33(4): 605-614.

Figures/Tables 19

Fig. 1 a Schematic illustration of DPC model with constant material parameter, b modified density-dependent DPC model showing the shear failure and cap surface as well as associated material parameters

Fig. 2 Elastic properties as function of green density: a Young’s modulus E as function of green density, b Poisson ratio ν

Table 1 Material model parameter as function of relative density

Fig. 3 Part geometry and model setup in the simulation: a geometry of the clutch plate part, b mesh for evaluation of stress and density state

Fig. 4 Schematic illustration of the assembled tooling and its kinematics

Fig. 5 Green density distribution of compaction and ejection

Fig. 6 Seven regions of the measured average green density

Fig. 7 Density comparison between simulation and experimental measurement

Fig. 8 History of maximum principal stress in the clutch plate during compaction, unloading and ejection

Fig. 9 Maximum principal stress in the clutch plate during compaction and ejection

Fig. 10 History of radial stress in the clutch plate during compaction, unloading and ejection

Fig. 11 History of axial stress in the clutch plate during compaction, unloading and ejection

Fig. 12 History of hoop stress in the clutch plate during compaction, unloading and ejection

Fig. 13 History of shear stress in the clutch plate during compaction, unloading and ejection

Fig. 14 Distribution of radial direction stresses in the clutch plate during compaction and ejection

Fig. 15 Distribution of axial direction stresses in the clutch plate during compaction and ejection

Fig. 16 Distribution of hoop direction stresses in the clutch plate during compaction and ejection

Fig. 17 Distribution of shear direction stresses in the clutch plate during compaction and ejection

Fig. 18 Peak value of five direction stresses in the clutch plate during compaction, unloading, and ejection

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