On possibilities for the determination of the coefficient of friction in hydroforming of tubes

Tribology plays an important role in metal forming, especially in tube hydroforming. The tests available for the experimental determination of the coefficient of friction (COF) are unsatisfying. This is especially true for the case of friction within the forming zone, i.e. where the workpiece is deformed plastically. A new measuring principle is developed. It is based on upsetting a tube. The comparison of experimental results and FEM simulation yields the COF without any undesired interference with the forming process. First results for a variation of the lubricant show the feasibility of the method.