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There
are
other
formulas
that
are
used
to
obtain
this
bend
allowance
also.
Some
are
fairly
accurate
some
are
not.
One
in
particular
also
helps
to
show
that
the
material
indeed
stretches.
It
is
called
the
Neutral
line
theory.
The
neutral
line
is
an
imaginary
line
that
passes
somewhere
close
to
the
middle
of
the
material.
It
is
the
area
where
the
material
neither
stretches
nor
compresses
in
the
bend.
If
the
material
did
not
stretch
at
all
then
the
neutral
line
would
be
at
50%
of
the
material.
I
believe
that
there
is
more
stretching
than
compressing
occurring
due
to
the
fact
that
the
neutral
line
is
closer
to
the
inside
of
the
bend.
Mild
cold
roll
steel
would
be
about
45
percent
of
the
material
thickness
if
you
are
air
bending
and
43
percent
for
bottom
bending.
The
next
three
pages
show
you
how
to
use
the
neutral
line
to
figure
bend
allowance.
In
this
manual
we
will
use
the
empirical
formula
to
obtain
the
bend
allowance.
Page:
19
NEUTRAL LINE THEORY
Note: 43% is usually used for CRS.
Neutral line is closer to the inside bend.
Neutral Line theory
