Page 449 - 04. Subyek Engineering Materials - Manufacturing, Engineering and Technology SI 6th Edition - Serope Kalpakjian, Stephen Schmid (2009)
P. 449

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                                                         Section 16.13
                                                                      Design Considerations in Sheet metal Forming










                            (b                                (C)         §


             a bend.


              FIGURE l6.57  Application of notches to avoid tearing and Wrinkling in right-angle bending
              operations. Source: Courtesy of Society of Manufacturing Engineers.


                       Poor               Good
                                                                   Poor




                     ux  ur



                                                                   Béllel'







                                 (H)                                (bl

             FIGURE l6.S8  Stress concentrations near bends. (a) Use ofa crescent or ear for a hole near
                     (b) Reduction of severity of tab  in flange. Source: Courtesy of Society of
             Manufacturing Engineers.
                                                                         Bef O re


                             Sharp                      Sharp
                             radius                     radius           After



                               (a)                        (D)

             FIGURE |6.59 Application of (a) scoring or (b) embossing to obtain a sharp inner radius in
             bending. Unless properly designed, these features can lead to fracture. Source: Courtesy of
             Society of Manufacturing Engineers.


              because of strain hardenin s  and can fracture leadin to a stress concentration that
                                                           g
                                                     ,
             propagates the crack into the rest of the sheet.
             Roll Forming.  In general, the process should be designed so as to control spring-
             back. Also, it is not difficult to include perforating rolls in the forming line, so that
             periodic holes, notches, or embossings can be located on the roll-formed shape.
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