Ermittlung von Reibzahlen nach Vorbelastungen

Determination of friction coefficients on preloaded surfaces

 

Motivation

FE-simulation plays an important role in the design and development of forming processes. The optimization of simulation leads to a better approximation of the numerical procedures and reduce the costs for the development and improvement of products. Due to surface roughness and lubricant distribution on the workpiece surface the friction behavior in the workpiece-tool-interface varies in a wide range.

Objectives

The aim of this project is to determine friction coefficients of prestrained sheet surfaces in strip-drawing tests for the one- and multi-step deep drawing process. These coefficients can then be used to improve the quality of numerical friction modeling in FE-simulations and therefore to a more efficient process design in the development process.

Figure 1: Roughness in dependency of technical strain in the tensile test.
Figure 1: Roughness in dependency of technical strain in the tensile test.

Approach

In a first step load histories in the deep drawing process are determined. On the one hand this is done with FE-Simulations and on the other hand surface topographies and lubricant distribution on workpiece surfaces in the industrial environment are determined. These results leads to the development of tools expanding the tribology test procedure in the dtrip-drawing-test with a defined load history [Figure 2].

Variations of chosen load history parameters influencing the friction coefficient will result in a database of friction coefficients that can be included in FE-simulations. This database will be verified in the industrial environment by surface analysis and the determination of lubricant distribution.

Figure 2: Extension of the tribology test with a defined load history
Figure 2: Extension of the tribology test with a defined load history