General Observations

  • 格式:pdf
  • 大小:51.98 KB
  • 文档页数:2

General Observations
Calculating the coil stock width is mainly based on the following assumption: due to
deformation and constriction of material, see Fig. 11, in the bending area connected with it, there will be a lengthening of the latitude co-ordinate of the work-piece with given retention of
volume.
In order to produce an arc element with a defined opening angle, and a median length of arc
b, as necessary for the production of a profile required, you have to envisage a length element of the unformed material that corresponds to the median length of the arc of the finished profile, minus lengthening.
The value for the coil stock width of any profile required, results from the length of unfolding
of a finished profile minus the total of elongation’s that occurred in the bending areas.
Fig. 42 Constriction in bending areas
All methods divide the profile into straights and arc elements for calculation. The calculation of
the initial width according to methods 1 to 3 is done in two steps. First the theoretical lengthening is defined for each arc element of the profile, following the respective calculation rules of the chosen method. The total of those lengthened is subtracted from the length of the profile after unfolding. And the result will be the coil stock width required, as the total of those lengthened of all reference zones, is the dimension by which the latitude co-ordinate of the material will be increased due to the shaping process.
Fig. 43 Lengthening b in a bending area
A model depiction of the lengthened b in a bending zone is shown in Fig. 12. It is supposed that the dimensions of straight sections will not change during shaping. These reflections will lead to an inconsistent alteration of material thickness within the transition zone between straight and arc elements. Nevertheless this approach should be maintained provided the following points are taken into consideration. It is known from studies that the material thickness s of bending areas reaches its minimum at the vertex of the curve and will only
reach the original material thickness s
o far out at the adjacent side. We can assume that the
surfaces between the real and the imaginary course of the external borderline have the same dimension at each side of the transition in question. See also Fig 13.
Fig. 44 Transition from straight to arc
Thus, the transverse strain may be still defined on the basis of volume retention. The method according to S+B proceeds slightly different in detail.
It approaches the arc elements with straight elements following certain rules. In combination with further gauge values depending on the bending angle one obtains the production width necessary for the arc element. Using the S+B method, the coil stock width for a profile, results from the total of the defined production widths for arc and straight elements.。