Compared with molding processes, polymer solid-phase forming has several advantages. Particularly, polymer forging is able to reduce cycle time for thick parts, process difficult-to-mold materials, and enhance mechanical performance through self-reinforcment. Although much research has been carried out in the past on solid-phase forming, little has been done on polymer forging. This can be partially attributed to the lack of fundamental understanding of the process, e.g., lack of understanding on instantaneous recovery and viscoelastic recovery and lack of a modeling and simulation capability. In the present study, upsetting experiments were conducted to study the forging behavior of nylon. The instantaneous elastic recovery and the time-dependent postrecovery were found to be significantly affected by upsetting speed and dwell time. The dimensional recovery behavior of upset samples was interpreted using the Burgers model. The stress-strain data from the upsetting experiment was used in a viscoplastic simulation of forging a cylindrical hole. The simulation result about load versus forging displacement agrees well with that from the forging experiment. (c) 2005 Wiley Periodicals, Inc.