Abstract
The lubricant viscosity is one parameter for optimizing drawing processes. The influence is due to the velocity depending friction behaviour between work piece and tool, as well as the effective process forces and resulting pressures in the lubricant. Because of the tribological size effect, the knowledge gained in macro processes cannot be transferred directly to micro forming processes. To understand the influence of the drawing speed, several parameters as the drawing radius and viscosity of lubricants are varied in this work. The resulting Stribeck curves show a varying effect of the different kinematic viscosities. High viscosity lubricant reduces the occurring friction significantly at low Stribeck numbers, but increases friction with rising Stribeck number extremely. Concluding the results, it can be stated that the hydrodynamic friction demands a relevant portion of the overall friction in micro forming process especially at high drawing velocities, which cannot be explained by the lubricant pocket model.
Highlights
In recent years, a continuous trend towards miniaturization while improving the functionality of products can be observed in many industrial sectors
Because of the tribological size effect, the knowledge gained in macro processes cannot be transferred directly to micro forming processes
An interesting alternative represent metallic micro components because they offer considerably different material properties and mass production by forming is relatively inexpensive. Due to these facts it seems very useful to scale down the size of existing forming processes as deep drawing, but this leads to new challenges e.g. size effects [3]
Summary
A continuous trend towards miniaturization while improving the functionality of products can be observed in many industrial sectors. An interesting alternative represent metallic micro components because they offer considerably different material properties and mass production by forming is relatively inexpensive Due to these facts it seems very useful to scale down the size of existing forming processes as deep drawing, but this leads to new challenges e.g. size effects [3]. Function of lubrication films are reducing friction and wear by transporting flakes out of the tooling, as well as transmission, cooling, damping, sealing and as corrosion protection In 2006, quantitative approaches were made by [9] with a mechanical-rheological model without considering viscosity of lubricant
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