Abstract
We report experimental measurements of friction between an aluminum alloy sliding over steel with various lubricant densities. Using the topography scans of the surfaces as input, we calculate the real contact area using the boundary element method and the dynamic friction coefficient by means of a simple mechanistic model. Partial lubrication of the surfaces is accounted for by a random deposition model of oil droplets. Our approach reproduces the qualitative trends of a decrease of the macroscopic friction coefficient with applied pressure, due to a larger fraction of the micro-contacts being lubricated for larger loads. This approach relates direct measurements of surface topography to realistic distributions of lubricant, suggesting possible model extensions towards quantitative predictions.
Highlights
Sheet metal forming of aluminum alloys is a well established production process in several industrial applications, from automotive and aerospace sectors to the production of daily life objects such as beverage cans, light reflectors or fuel tanks
We report experimental measurements of friction between an aluminum alloy sliding over steel with various lubricant densities
We have reported experimental data regarding the frictional sliding of aluminum sheets between steel pads. This process is fundamental for metal forming in industrial applications and friction must be controlled for a robust production process and to avoid defects in the final product
Summary
Sheet metal forming of aluminum alloys is a well established production process in several industrial applications, from automotive and aerospace sectors to the production of daily life objects such as beverage cans, light reflectors or fuel tanks. Friction is a system property that requires extensive experimental campaigns to understand the interaction between the sheet, the tool surface and the lubricant, depending on the normal load, the sliding velocity and the temperature. The resulting friction force at macroscopic level is the well-known Amontons-Coulomb (AC) law [9], stating that the force is proportional to the applied normal load and independent of the sliding velocity. This simple behavior has been connected by Bowden and Tabor to the linearity of the real contact area with the normal load [10]
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