Simulation of PTFE sintering: thermal stresses and deformation behavior

A finite element model has been used to study the sintering process of polytetra-fluoroethylene (PTFE) cylinders in order to predict residual thermal stresses; bothsolid (rods) and hollow (billets) blocks were studied. The simulation of the processwas performed considering three separate stages: thermal, deformation, and stressanalysis. For each stage, relevant material properties were determined experimen-tally. In particular, the deformation behavior of PTFE was thoroughly investigated bymeans of thermo-mechanical analysis (TMA). It is shown that experimental resultscan be explained considering deformation recovery and orientation effects. Predic-tions of the model are compared with experimental measurements performed on realPTFE-sintered cylinders. Temperature and deformation distributions determinedwith the model agree well with experimental data. Fair agreement between predictedand experimentally measured residual stresses is obtained, and the influence of cyl-inder size and applied cooling rate on residual stresses is correctly predicted.