Single screw extruders are known as good melt pumps with the high, stable pressure needed for part extrusion. However they have a particular disadvantage in achieving good mixing. In a vibration-induced polymer extruder (VIPE), a vibration force field (VFF) is introduced into the whole extrusion process by the axial vibration of screw, which affects the mixing process. It is well-known that the total shear strain (TSS) has been widely used to measure the effect of melt mixing in a laminar system. In this study, an analytic model for pulsating TSS was developed and the TSS distribution of the melt in the screw channel of the melt conveying section in a VIPE was calculated to further understand the time-dependent dynamic laminar mixing process. A comparison of the TSS distribution of melt in screw channel with and without vibration shows that the TSS of melt increases with the application of vibration and the larger the vibration frequency and amplitude are, the larger the TSS that the melt may experience while melt traveling through the melt conveying section, which is favorable for melt mixing. (C) 2008 Wiley Periodicals, Inc.