Flow Mechanics on Extrusion through a Square‐Entry Die

The relationships between the constants of the Herschel‐Bulkley (H‐B) equation describing plastic flow and the Benbow equation for extrusion through a square‐entry die were studied via computer simultions. These relationships are fundamental for characterizing the rheology of ceramic extrudates using the square‐entry rheometer and are difficult to obtain from experiments. Results showed that the apparent shear rate should be used instead of extrudate velocity in the Benbow equation, and the Benbow equation was modified accordingly. The exponent in the H‐B equation was exactly the same as the shear thinning exponent for the extrudate body in the modified Benbow equation. The die‐entry velocity factor was a function not only of the shear rate factor but also of the shear thinning exponent in the H‐B equation. The yield strength of the modified Benbow equation was zero when the yield strength in the H‐B equation was zero.