Abstract
There are 6 different types of equations that have been formulated to measure friction through the bending under tension test, however, there is no work to show whether these calculations actually represent what is happening in a sheet metal stamping process. This paper aims to make a direct comparison between the bending under tension test and the sheet metal forming of a test piece to see if the friction coefficient reported by the test is able to predict friction in a real part. Several sources of information were used such as computer simulations, bending under tension test with different sensors and sheet metal forming tests of a cylindrical geometry to evaluate the friction. The results indicate that the equations already developed are not able to accurately predict the friction at the sheet interface and, therefore, a new equation was developed for this that is simpler to measure and presented satisfactory results.
Highlights
The bending under tension (BUT) test is currently the most commonly used test to simulate and isolate the friction generated in a stamping process
Since the aim of this study is to measure the friction coefficient in sheet metal stamping through the bending under tension test, a stamping test was performed to measure the parameters that would be later compared with a numerical simulation to find the friction coefficient that governs the process
This study aimed to propose a new equation for the calculation of the coefficient of friction from the BUT test and in this regard, some conclusions can be made
Summary
The bending under tension (BUT) test is currently the most commonly used test to simulate and isolate the friction generated in a stamping process. Sniekers and Smits[1] were the first to introduce the idea of measuring torque to calculate friction, and for this purpose, they proposed a mathematical formulation that included torque in calculating the coefficient of friction. They only made a few measurements to find the friction value without worrying about whether it was correct. Nanayakkara et al.[2] were the first researchers to compare three types of equations used to calculate friction in the BUT test, and to do so, used the results to calculate friction for different pin sizes. BUT test was used to measure friction when the pin is chromed or only machined with Teflon lubricant, grease and without lubrication and the results were correlated only, that is, only the variation between values was investigated, not caring if the value itself was correct
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