Yusuke Imayoshi, Shuji Ohsaki, Hideya Nakamura, Satoru Watano
Department of Chemical Engineering, Osaka Metropolitan University
Purpose.
Recently, extensive numerical studies of the tableting process using a finite element method (FEM) have been conducted to understand the detailed capping mechanism. In our previous study, a combined novel model using both the DPC and Perzyna models, which incorporates a visco-plastic behavior considering the compression speed, was proposed [1]. In this study, FEM simulations using the DPC-Perzyna model under the industrial tableting speed (< 40 mm/s) were performed to further understand the effect of the compression speed on the capping occurrence.
Methods.
The DPC-Perzyna model parameters were determined from the high-speed tableting experiment using a tableting simulator (CRUX033L, Kikusui Seisakusho Ltd., Japan). Tableting process was simulated to investigate the effect of compression speed on the relative density and various stress distributions inside tablet. Furthermore, the effect of relationship between tablet strength and residual stress inside tablet on the capping occurrence was evaluated.
Results.
The simulation results demonstrated that the compression speed affected the stress and relative density distributions. In addition, the tablet obtained at the high compression speed had a large stress gradient, resulting in a non-uniform stress distribution. Moreover, by considering fracture mechanics, capping tendency was successfully predicted based on the relationship between residual stress and critical stress (Fig. 1).
Conclusions.
Numerical analysis of the high-speed tableting process using DPC-Perzyna model was conducted to clarify the effects of tableting speed and stress distribution on capping.

Reference.
[1] S. Oshaki et al., Int. J. Pharm., 575, 118936 (2020)