Effect of geometrical and process parameters on coefficient of friction in deep drawing process at the flange and the radius regions

Abstract

In the deep drawing process analyses, generally a single friction coefficient is taken into account for the flange and radius regions of the dies. In fact, friction coefficients between these regions and sheet metal are different from each other. Using of a single friction coefficient for different regions would lead to performing of unreal analyses. In this study, coefficient of friction which is one of the most important parameters affects the deep drawing process for flange and radius regions were determined experimentally. A new friction test apparatus which could determine the friction coefficients for both the flange and the radius regions with only a single experiment was designed and manufactured. Hence, the time and the cost have been reduced. After the tests, it was shown that the friction coefficients are considerably different from each other. By the help of the determined friction coefficients for flange and radius regions contacting to sheet metal, it is concluded that deep drawing analyses can yield more accurate results; thus, time, labor force, and money consumption because of trial-and-error process can be eliminated during die design and process analyses. For this purpose, case studies were experimentally and numerically conducted by using the obtained friction coefficients for flange and radius regions so as to validate the results. Moreover, effect of die radius, surface roughness of the tools, drawing speed, blank holder force, and lubrication type on dynamic coefficient friction between flange and radius regions of the tools and sheet metal were investigated by using ANOVA analysis method. According to the results, lubricant type was found to be an effective parameter for the flange and radius regions. On the other hand, the next effective parameter was surface roughness of the tools and the die radius for radius region, the blank holder force, and drawing speed have small effect for both flange and radius regions. The suitability of separately using of coefficients of friction for the flange and radius regions was verified to obtain closer results to the process.