| 摘要 |
A method of forming an integral rivet in a sheet element including providing cooperating male and female dies and an interposed sheet element, moving the male die toward the female die to draw an outwardly directed hollow boss. Continuing movement of the male die toward the female die to thin an annular region in the lower portion of the hollow boss by compression which establishes metal flow substantially entirely in the direction of the upper portion of the hollow boss. Continuing relative closing movement of the male die with respect to the female die to establish an annular band of thinned material extending upwardly toward the upper portion of the hollow boss, whereby the upper portion of the hollow boss has a thickness substantially equal to the thickness of the remainder of the sheet element. The sheet element may be peripherally restrained around the area in which the boss is formed during boss formation. |
