An experimental study is accomplished to investigate the fracture phenomenon in a non Newtonian viscoplastic material trhougth and abrupt expansion with axial symmetry. A visualization was then performed using a simple technique, with addition of small spherical particles to the test fluid. Aqueous solutions of carbopol 676 at three different concentrations were prepared and submited to creeping flow, with Reynolds number at the larger tube below than 0,1. Three expansion ratios, namely, 2,0 6,0 and 12,5, were studied in this narrow range of laminar flow. Pressure losses ar the expansion plane were determined from experimental measurement of everall pressure differentials along the tubing, for three different flow rates. The generalized Newtonian fluid model was used to describe the mechanical behavior of the material, with the viscosity of the Herschel-Bulkley type, which involves three rheological parameters the yield stress (T0), consistency index (K) and the behaviour index (n).