An investigation into friction in dynamic plane upsetting

The evaluation of friction on the friction interface in plane-strain upsetting is developed. The distribution of friction shear stress is derived and found to be dependent on the ratio (called the F-coefficient) of the second derivative and the first derivative of the velocity in the x-direction. According to the value of the F-coefficient, friction conditions such as sticking, frictionless, and many kinds of function approximated to linear, exponential, and arc-tangent can be expressed easily. An optimal approach with velocity parameters is used to calculate the F-coefficient at various reductions in height in an experimental approach. It is shown that this method presents a good approach to evaluate friction in comparison with experimental data.