Combining with Jeffery equation and mechanics model of fixed point of Euler rigid body,the mechanism and method of short fiber radial orientation and characteristics of movement in tread extrusion process were studied.The influences of tension flow field and shear flow field in flow channel on short fiber orientation have been systemically analyzed.The extrusion die,which had a hinder dam by adopting such principle,was designed.The results show that the expansion ratio and expanding angle of cross section are the key factors to determine the radial orientation of short fiber.Mathematical model of short fiber radial orientation was established.The results also show that the best expansion ratio is 3-4,the expanding angle is 75°,obtaining the average orientation angle between 70°-80°,and the rationality of the radial oriented mechanism and the mathematical model are verified.
