Steels_ Metallurgy and Applications, Third Edition

36 Steels: Metallurgy and Applications

Figure 1.36 Computer simulation of deep-drawing operations (After Miles 61)

significantly different from those encountered in the simple laboratory tests that
are used to construct the FLD. There has, therefore, been a move to eliminate
the empiricism involved in the approaches described above through the use of
finite element modelling. It is now possible to simulate a wide variety of different
forming processes by computer-aided engineering and Miles 61 has described the
use of this technique in drawing operations on low-carbon steel. This is illus-
trated in Figure 1.36 which shows the computer simulation of a deep-drawn cup.
The purpose of this particular experiment was to predict the tool forces required
to form the component, the hold-down pressure on the blank and the tearing
tendency of the sheet if the friction at the blank holder stopped the material
from drawing correctly. Using this approach, it is also possible to identify areas
of thinning and thickening in the sheet and where excessive compression might
lead to wrinkling.
The computer programs that have now been generated for this type of work
are extremely powerful and versatile and permit the analysis of a wide variety
of three-dimensional shapes. The effects of planar and normal isotropy can also
be accommodated.

Strip steel manufacture

The strip steels supplied for cold-forming applications may be divided into two
main groups, namely those for which the main requirement is the provision of a
defined minimum level of formability and those for which the main requirement is
a defined minimum level of strength with a more limited level of formability. The
former may be called mild steels whereas the latter may be called high-strength
steels though in a few cases there may be little difference in strength between
the two. Many of the steels available are covered by standards, including coated
steels, but some of the most recently developed materials are not yet covered. It
is also common, particularly with a formability requirement, for a specification
that is tighter than the standard specification to be agreed between a customer