Instrumentation for tribological analysis of sheet metal forming operations

Friction is a subject of importance from many points of view. It controls the relative motion between two bodies in contact and most manufacturing methods based on engagement between a tool and a workpiece are dependent on the prevailing frictional conditions. The outcome in terms of part quality from manufacturing methods like sheet forming is directly connected to the frictional state.

The aim of the research addressed in this thesis was to develop instrumentation and measurement strategies for tribological studies with the ability to capture the actual conditions in sheet metal forming processes. The work constitutes two major parts: The development of an experimental platform for tribological analysis and the verification and evaluation of its capabilities by studies within specific areas.

The requirements for the novel instrumentation were determined by extracting and analyzing the fundamental mechanisms in sheet forming processes and through a review of the current state of art. The uniqueness of the developed platform is the possibility to cover a large process window in terms of velocity and pressure and also the possibility to explore the frictional outcome under dynamic process conditions, similar to those in forming operations.

A number of studies on different aspects of tribology proved a high sensitivity regarding friction dependent parameters and an accuracy and repeatability which enabled different influencing factors to be studied in depth. Complementary studies within this thesis work covered the importance of tool temperature and lubricants, the impact of the surface integrity and also the influence of the dynamics in terms of accelerated and decelerated conditions of the tool relative to the sheet in relation to the frictional outcome.