Binder/blankholder

The upper and lower holding surfaces which control metal flow around a shape to be formed in a draw operation, also known as a binder ring or ring.

Blank

A flat, precut metal shape ready for subsequent press operation.  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; the resultant flat pattern.

Blankholder

The part of the draw die which holds the workpiece against the draw ring to control metal flow.  Also called binder, binder ring, or ring.

Deep drawing

The drawing of deeply recessed parts from sheet material through plastic flow of the material when the depth of the recess equals or exceeds the minimum part width.  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.

Die

A complete tool consisting of a pair or combination of pairs of mating members for producing work in presses, including all supporting and actuating parts of the tool.  A complete tool used in any press for any operation or series of operations such as forming, flanging, piercing, or cutting.  The upper member or members are attached to the slide or slides of the press and the lower member is clamped or bolted to the bed or bolster with the die members being shaped to cut or form the material placed between them when the press makes a stroke.

DQSK steel

Drawing Quality Special Killed Steel, a highly formable grade of mild steel usually aluminum deoxidized and sometimes referred to as DQAK (Drawing Quality Aluminum Killed).

Drawbead

A ridge constructed around a portion of a die cavity to control metal flow.  A groove in the mating blank holder allows die closing.

Drawing

A sheet metal deformation process in which plastic flow results in a positive strain in one direction in the plane of the sheet surface and a negative strain at 90 degrees.  The process of cold forming a flat precut metal blank into a hollow vessel without excessive wrinkling, thinning, or fracturing.

Elastic limit

The maximum stress to which a material may be subjected, and yet return to its original shape and dimensions on removal of the stress.

Elongation

The amount of permanent extension in a tensile test specimen.

Engineering strain

The unit elongation given by the change in length divided by the original length.  Preferably called nominal strain.

Engineering stress

The unit force obtained when the applied load is divided by the original cross-sectional area.  Preferably called nominal stress.

Forming Limit Diagram (FLD)

An empirical curve showing the biaxial strain levels beyond which failure may occur in sheet metal forming.  The strains are given in terms of major and minor strains measured from deformed circles, previously printed onto the undeformed sheet.

Hardness

The ability of a material to resist permanent penetration by a much harder body.

High strength steel (HSS)

By Auto/Steel partnership definition, any sheet steel product whose initial yield strength is specified 30 KSI or higher. These include bake hardenable steels.

Lock beads

Draw beads designed to allow no metal flow.

Lubricant

Any substance interposed between two surfaces in relative motion for the purpose of reducing friction and/or wear between them.  Any surface which has the specific property of reducing friction between two surfaces in contact.

Major strain

Largest principal strain in the sheet surface.  Often measured from the major axis of the ellipse resulting from the deformation of a circular grid.

Metal clearance

Depending on the stock thickness being used to make the part in the die, it is the running clearance on the bottom of the press stroke between flange steels or male and female form steels.

Minor Strain

The principal strain in the sheet surface in the direction perpendicular to the major strain.  Often measured from the minor axis of the ellipse resulting from deformation of a circular grid.

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 geometric factors.

n value

The work-hardening exponent derived from the relationship between true stress and true strain , given by .  It is a measure of stretchability.  Often called the work strengthening exponent.

Plastic strain ratio (  value)

A measure of the normal plastic anistrophy as defined by the ratio of the true width strain to the true thickness strain in a tensile test.  The average plastic strain ratio ( r bar) is determined from tensile samples taken in at least three directions from the sheet rolling direction, usually at 0, 45 and 90 degrees. is calculated as follows:

value

The ratio of true width strain to a true thickness strain in a uniaxial tension test where the tensile sample is cut parallel to the rolling direction.  It is a measure of deep drawability.

Tensile strength

The maximum stress that a material is capable of withstanding without breaking under a gradually and uniformly applied load.  The strength calculated at the maximum load, in a tensile test, by dividing the maximum load by the original cross-sectional area.  The ultimate strength of a material, measured in pounds per square inch in tension on the original cross section tested, which, if exceeded, causes sectional deformation leading to ultimate rupture.

Thickness strain

Thickness strain is the change in thickness of the material due to forming.  Thickness strain or metal thin-out can be measured using an ultrasonic thickness gauge. It is necessary to do some circle grid analysis to determine the location of the thickness strain on the forming limit diagram, but then this technique can be used as a quick non-destructive test.  Since this variable can be most closely linked to breakage it will provide the primary comparison to setting the level of critical process variables.

Work-hardening

An increase in hardness and strength caused by plastic deformation.

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 strength

The stress at which a steel exhibits a specified deviation from the proportionality of stress to strain.  Generally, the yield strength is the measure of the stress at which a steel sample will begin to permanently deform under a tensile stress.

Yield stress

A stress at which a steel exhibits the first measurable permanent plastic deformation.