Extrusion pressure theory formula about the large caliber and thick wall pipe was derived by a new mechanics model and compared with formulas derived by other mechanical models. This theory formula could reflect the functional relation between extrusion pressure and extruded height, while others could not. The computer simulation and productive practice indicate that the theory formula derived by continuous upsetting extrusion mechanics model coincide with simulation result and fit productive practice well. Continuous upsetting extrusion mechanics model accords with actual stress condition in vertical extrusion of the large caliber thick wall pipe.
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