| A |
| Anisotropy (Earring) - Variations
in one or more physical or mechanical properties with
direction. |
|
| B |
| Blank - The piece of sheet metal,
produced in cutting dies, that is to be subjected to
further press operations. A blank may have a specific
shape developed to facilitate forming or to eliminate
a trimming operation subsequent to forming. |
| Blank Development - The
process of determining the optimum size and shape of
a blank
for a specific part to minimize scrap. |
| Blank Gridding (Circle
Grid Analysis) - Imprinting a metal blank
with a pattern on the sheet surface, such pattern to
be used for subsequent strain measurement and interpretation. |
| Blank Holder - That part of a forming
die which holds the blank by pressure against a mating
surface of the die to control metal flow and prevent
wrinkling. The blank holder is sometimes referred to
as “hold down” or binder area. Pressure is
applied by mechanical means, springs, air, or fluid cushions. |
| Blank Holder Pressure - The pressure
exerted by the blank holder against the blank. This is
normally adjustable to control metal flow during drawing. |
| Blanking - The act of cutting a
blank. |
|
| C |
| Clamping Pressure - Pressure applied
to a limited area of the sheet surface, usually at the
periphery, to control or limit metal flow during forming. |
| Coining - A process
of cold forming metals in which the metal is shaped between
two dies
in such a manner as to fill the depression of both dies
in relief by displacement of the material. |
| Cold Working - The deformation
of metal significantly below its recrystallization temperature
such that work hardening occurs. |
| Cupping - A press forming operation
in which a cup shaped part is produced from sheet metal.
Cupping is often the first operation in the production
of a complex deep drawn part. |
| Cut-Off Die - Sometimes called
a trimming die. The cut-off die can be the last die in
a set of transfer dies which cuts the part loose from
scrap. It can also be a die which cuts straight-sided
blanks from a coil for later use in a draw die. |
|
| D |
| Deep Drawing - A drawing operation
where a part is produced from a blank by the action of
a punch in which the sheet is pulled into a die cavity
and the flange of the blank is compressed in the circumferential
direction. The area directly under the punch remains
undeformed. |
| Developed Blank - A flat blank
with a shape that will produce a finished part with the
desired configuration and a minimum of trimming operations. |
| Die - (a) A complete
set of stations (tool) used in a press for any operation
or series of
operations, such as forming, impressing, piercing and
cutting. The upper member(s) are attached to the slide(s)
of the press and the lower member is clamped or bolted
to the bed or bolster with the die members being so shaped
as to cut or form the material placed between them when
the press makes a stroke. |
| Die Clearance - The
space on each side, between punch and die that metal
fills during the
process and is typically tight to the punch. |
| Die Coating - Hard metal incorporated
into the working surface of a die to protect the working
surface or to separate the sheet metal surface from direct
contact
with the basic die material. Hard chromium plating is
an example. |
| Die Entry Radius - The radius at
the edge of the die over which metal is drawn. |
| Drawability - The ability of a
sheet to form cup-shaped parts by the action of a punch
under conditions that cause the flange or a portion of
the flange to be drawn into the die cavity. |
| Draw Bead - A ridge constructed
around a portion of a die cavity to partially restrain
metal flow. A groove in the mating blank holder allows
die closing. Sometimes called die bead. |
|
| E |
| Embossing - Displacing
of a minor amount of metal without noticeable reduction
in sheet
metal thickness. |
| Etching - Production of designs,
including grids, on metal surface by a corrosive reagent
or electrolytic action. |
| Extruded Hole - A hole formed
by a punch which first cleanly cuts a hole and then is
pushed farther through to form a flange with an enlargement
of the original hole. This may be a two-step operation. |
|
| F |
| First Draw - The
first drawing operation in a series (often called the “cup”)
usually performed on a flat blank. |
| Flanging - A bending
operation in which a narrow strip at the edge of a sheet
is bent
down (up) along a straight or curved line. It is used
for edge strengthening, appearance, rigidity and the
removal of sheared edges. A flange is often used as a
fastening surface. |
| Flow Curve - A graphical representation
of the relationship between load and deformation during
plastic deformation. |
| Formability - The ability of sheet
metal to be changed into a useful shape. |
|
| G |
| Gridding (Circle Grid Analysis)
- Imprinting an array of repetitive geometrical patterns
on a sheet prior to forming for subsequent determination
of deformation. Imprinting techniques include eletrochemical
marking, photoprinting, ink stamping and lithographing. |
|
| H |
| Hardness Test - A
test to measure a particular material’s resistance
to indentation. Tests for sheet metal include Rockwell,
Rockwell Superficial,
Tukon and Vickers. |
|
| I |
| Ironing - Forming between dies
whose side wall clearance is less than the sheet metal
thickness, such that a thinning action occurs. This usually
takes place in the side walls of deep drawn parts where
the inflow of metal from the flange tends to thicken
or wrinkle; subsequent ironing produces a more uniform
wall thickness. |
| Isotropy - A term indicating equal
physical or mechanical properties in all directions. |
|
| L |
| Lock Bead - A ridge constructed
around a die cavity to completely restrict metal flow
into the die. |
| Lubricant - Any substance interposed
between two surfaces in relative motion for the purpose
of reducing the friction and/or wear between them. |
| Luder’s Lines or Luder’s
Bands - The surface strain markings (associated with
discontinuous yielding) that occur as a result of deformation
operations such as press forming. Luder’s lines
or bands are also referred to as stretcher strains. |
|
| M |
| Microhardness Test - An indentation
test using diamond indenters at very low loads, usually
in the range of 1 to 1,000 grams. |
|
| N |
| Necking - Localized thinning that
occurs during sheet metal forming prior to fracture.
The onset of localized necking is dependent upon the
stress state which is affected by geometrical factors. |
| “n” Value - A
term commonly referred to as work hardening exponent
derived from the relationship between
true stress and true strain. Also called work strengthening
exponent. |
|
| P |
| Piercing - Creating a hole in the
metal with a punch. |
| Progressive Die - A
die planned to accomplish a sequence of operations as
the strip or
sheet of material is advanced from station to station
manually or mechanically. |
| Progressive Forming - Sequential
metalworking at consecutive stations, either with a single
die or with separate dies. |
| Punch - The member
of a tool that forces the metal into the die during blanking,
coining,
drawing, embossing, forging, stretching or similar operations. |
| Punch Nose Radius - The shape of
the punch end, contacting the material being formed to
allow proper material flow or movement. |
|
| R |
| Reverse Redrawing - An operation
after the first drawing operation in which the part is
turned inside out by inverting and redrawing, usually
in another die, to a small diameter. |
|
| S |
| Shear Burr - A
raised edge resulting from metal flow induced by blanking,
cutting or punching. |
| Shearing - A cutting operation
in which the work metal is placed between a stationary
lower blade and movable upper blade and severed by bringing
the blades together. Cutting occurs by a combination
of metal penetration and actual fracture of metal. |
| Springback - Elastic recovery of
a portion of the deformation produced during forming.
It results in a difference in shape between the part
and the die. |
| Stamping - A general term to denote
all pressworking. In a more specific sense, stamping
is used to imprint letters, numerals, and trademarks
in sheet metal, machined parts, forgings, and castings.
A tool called a “stamp” with the letter or
number raised on its surface, is hammered or forced into
the metal leaving a depression on the surface in the
form of a letter or number. |
| Strain Lines - Surface defects
in the form of shallow line type depressions appearing
in sheet metals after stretching the surface a few percent
of unit area or length. |
| Surface Hardness - The hardness
of that portion of the material very near the surface
as measured by microhardness or superficial hardness
testers. |
| Surface Roughness - The
fine irregularities in the surface texture which result
from the production process. Consideration as vertical
deviations from the
nominal or average plane of the surface. |
| Surface Texture - Repetitive
or random deviations from the nominal surface which form
the pattern of the surface. Includes roughness, waviness
and flaws. |
| Swift Cup Test - A
test for deep drawability using circular blanks of various
diameters which are drawn into a flat or hemispherical
bottomed cup. Drawability is assessed by the Limiting
Drawing Ratio. |
|
| T |
| Tearing - Failure and localized separation of a sheet
metal. |
| Tensile Ratio - The ratio of the
tensile strength to yield strength. It is the inverse
of the yield ratio. |
| Tensile Strength or Ultimate
Tensile Strength - The strength calculated at the maximum load,
in a tensile test, by dividing the maximum load by the
original cross-sectional area. |
| Total Elongation - A parameter
measured in a tensile test used as a measure of ductility. |
|
| W |
| Work Hardening - An increase in
hardness and strength caused by plastic deformation at
temperatures lower than the recrystallization temperature.
Sometimes referred to as strain hardening. |
|
| Y |
| Yield Point Elongation
- The extension
associated with discontinuous yielding which occurs at
approximately constant load following the onset of plastic
flow. It
is associated with the propagation of Luder’s lines
or bands. |
| Yield Ratio - The ratio of the
yield strength to the tensile strength. It is the inverse
of the tensile ratio. |
| Yield Stress - A stress at which
a steel exhibits the first meas-urable permanent plastic
deformation. |
| Young’s Modulus or Elastic
Modulus - A measure of the rigidity of a metal. It is
the ratio of stress, within proportional limit, to corresponding
strain. Young’s
Modulus specifically is the modulus obtained in tension
or compression. |
