Some theoretical considerations for the direct drawing of section rod from round bar

Abstract

The maximum reduction of area obtainable, when directly drawing section from round bar, is calculated from a lower bound analysis; this reduction is less than that occurring when drawing round rod from round bar. Also it is shown, unlike the drawing of round section from round bar that there must be, for the section to be accurately formed, a minimum reduction in area. An upper bound solution to the problem of the prediction of draw stress ratio for the direct drawing of section is given some consideration and it is shown that the predicted values are higher than those for the drawing of round rod. A lower bound solution for the direct drawing of section is presented in detail and compared with the upper bound solution. Comparison is made also between both the lower and upper bound solutions and with published data on the drawing of round to round, since either of these new theories is applicable to the drawing of a symmetric section with an infinite number of sides. It is shown, that not only can the draw stress be calculated but that the equivalent die angle can be optimised for every relevant combination of the coefficient of friction and reduction of area.