2-DIMENSIONAL PLANAR FLOW OF A VISCOELASTIC PLASTIC MEDIUM

The present study is concerned with finite element simulation of the p lanar entry flow of a viscoelastic plastic medium exhibiting yield str ess. The numerical scheme is based on the Galerkin formulation. Flow e xperiments are carried out on a carbon black filled rubber compound. S teady-state pressure drops are measured on two sets of contraction or expansion dies having different lengths and a constant contraction or expansion ratio of 4:1 with entrance angles of 90, 45 and 15 degrees. The predicted and measured pressure drops are compared. The predicted results indicate that expansion flow has always a higher pressure drop than contraction flow. This prediction is in agreement with experimen tal data only at low flow rates, but not at high flow rates. The latte r disagreement is possibly an indication that the assumption of fully- developed flow in the upstream and downstream regions is not realistic at high flow rates, even for the large length-to-thickness ratio chan nels employed. The evolution of the velocity, shear stress, and normal stress fields in the contraction or expansion flow and the location o f pseudo-yield surfaces are also calculated.