UNIAXIAL COMPRESSION OF A HARD WHEAT FLOUR DOUGH: DATA ANALYSIS USING THE UPPER CONVECTED MAXWELL MODEL

The behavior of a hard wheat flour dough has been measured in lubricated uniaxial compression experiments at compressional rates (crosshead speeds) of 0.2, 2 and 20 cm/min. The appropriate differential equation, derived for an upper convected Maxwell model, while taking into account the changing strain rate during the compression at constant crosshead speed, was solved numerically. With a single choice of model parameters (a viscosity and a relaxation time) there was surprisingly good agreement between the experimental and calculated results. Best fits were obtained, however, when the parameters were allowed to vary with crosshead speed, reflecting the broad relaxation time distribution known to exist in doughs.