Abstract
Current work is focused on the influence of friction in deep drawing process. Friction measurements were also conducted using a modified tribotester based on strip sliding between tools. Four different tool surfaces were tested under similar contact conditions regarding contact area, normal pressure, sliding speed, lubricant and surface characteristics to calculate the friction coefficient between the tool surface and a high strength low alloy steel sheet HSLA 380. The results showed that friction coefficient varies over a wide range with different lubricating conditions and different sliding velocities. For some sliding velocities, the coefficient of friction is stable and low, while for others it is unstable and higher. Results of the experiments reveal that this novel tribotester is a very useful tool to evaluate and compare the friction between steel sheet and tool surfaces in alloyed steel for cold working applications. The outcomes have only small dispersion within the different test series, which indicates a stable process with good repeatability. The test method enables comparison of different surface finishes and treatments, lubricants and coatings in terms of friction and galling under conditions similar to those found in sheet metal forming processes. The four different types of surfaces considered for this study were grinded, polished, nitrided and quenched/tempered. The main difference among the tested tools in this work was the surface roughness, which was found to have a strong influence on friction.
Highlights
Tribology is the science and technology for friction, lubrication and wear
Four different tool surfaces were tested under similar contact conditions regarding contact area, normal pressure, sliding speed, lubricant and surface characteristics to calculate the friction coefficient between the tool surface and a high strength low alloy steel sheet HSLA 380
The results showed that friction coefficient varies over a wide range with different lubricating conditions and different sliding velocities
Summary
Tribology is the science and technology for friction, lubrication and wear. Tri-. A modified strip drawing tribotester has been used to generate the movement between the tool and sheet The uniqueness with this device compared to existing tribotesters used within sheet forming applications is the ability to fully control the applied normal force and drawing velocity during experimentation to simulate true tribological conditions more accurately. This option makes it possible to combine very accurate control of the relative movement between the sheet and the tool with consistent load and pulling force measurement [1] [2]. Different tribological tests were carried out, which included the pin-on-disc machine and a developed modified strip drawing test, both aimed to simulate behaviour and to investigate the friction between sheet metal and tools during forming
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