Abstract: Based on dissipation mechanism of shearing power, a theoretical model for vibrating shear flow was formulated and new method for calculating the dynamic viscosity of polymer melts was proposed in this paper. Using the method，the dynamic viscosity of Maxwell fluid in simple vibrating shear
flow was found in accordance with results using a traditional method. The prediction ability of the method was discussed based on the superposition of vibrating shear flow onto the steady flow. The limi-tations of the model for the superposed flows were found and the causes were analyzed.Results of rhco-ogical experiments showed a good agreement with the theoretical prediction in a bound of small amplituck.

Key words: viscous dissipation, dynamic viscosity, viscoclastic fluid, vibration shear-flow field