Page 47 - Modern Steel Construction (April 2019)

Talking the Talk
Here is a glossary of common bending-rolling terms, taken from Design Guide 33.

Arc. Part of the circumference of a curve. stresses and deflections are in the plane of Rise. The distance, perpendicular to
The curved portion of a bend. curvature. the chord, between the mid-point of
a chord and an arc. Also known as the
Arc length. The curved distance along Incremental step bending. A cold-bending mid-ordinate.
a circumferential line. The length of the method that uses hydraulic rams to apply
curved portion of a member. bending forces at several discrete, closely Rotary-draw bending. A bending method
spaced locations along the member. where the member is clamped to a form
Bend radius. The radius of curvature, and bent by rotating it around a bend die.
measured to a reference point on the cross Induction bending. A hot-bending
section. method that utilizes an electric induction Slope. The angle of an inclined member
coil to heat a short section of the member designated using the vertical (rise) and
Center-to-center. The distance between before it is curved by force. horizontal (run) distances between two
tangent points of two adjoining bends. points. Also known as bevel or pitch.
Local buckling. A type of potential
Chord. The straight distance between two cross-sectional distortion that is caused Snap-through buckling. A type of instabil-
points on a curve.
by compression stresses in the member ity where the load-displacement diagram
Cold bending. Any bending process induced during the bending operation. descends after reaching a limit point and
where curvature is induced by load Local buckling can be in the form of a the structure abruptly transforms from
application at room temperature. single half-wave or a series of wrinkles one equilibrium state to another remote
along the entire bend length. Also known equilibrium state on the ascending, stable
Compound bend. A curve made up of as waving or wrinkling. portion of the curve.
two or more arcs in the same plane, joined
tangentially without reversal of curvature. Mandrel. A tool that can be inserted into Spiral. A three-dimensional curve with
a HSS member to support the walls and an arc in one plane and a constant slope
Degree of bend. The angle to which a minimize cross-sectional distortion during in a perpendicular plane. Also known
bend is formed. the bending process. as a helix or helical curve. The curving
Distortion. A deviation from the original Multi-axis bend. A bend with curvature process is often called sloped rolling or
cross-sectional shape. about more than one axis. Also known as a pitched rolling.
Ductility. The ability of the material to multi-plane bend. Springback. The deformation of a bent
deform without fracture. Normalizing. A thermal treatment where member immediately after a bending
Easy way. The orientation of a member the member is heated to a suitable tem- load is released, where a portion of the
curvature is lost.
where bending occurs about the weak perature above the upper transformation
principal axis. temperature, followed by cooling in still air Strake. A protruding fin that can be
at room temperature. connected to a structure to improve
Gag pressing. A cold-bending method aerodynamic stability.
that uses hydraulic rams to simultaneously Off-axis bend. A bending orientation
apply bending forces at discrete, widely- where the member is curved about a non- Synchronized incremental cold bending.
spaced, locations along the member. principal or non-geometric axis. A cold-bending process where syn-
Also known as point bending. Also known as conical rolling. chronized forces are applied at several
locations along the member.
Grip. An additional straight length at each Oil-canning. A form of local buckling that
end of a curved member required in the can cause collapse of the cross section due Tangent. A straight line, perpendicular to
bending operation. Also known as “hold to the combined effect of ovalization and the radius, that touches a curve at a single
and tail” or “lead and tail” to emphasize local buckling in a single half-wave. point. A straight member adjacent to a
the additional length is required at each Out-of-plane flexure. Bending of a curved curved segment.
end of the member. member where moment is applied in the Tangent point. The start or end point of
Hard way. The orientation of a member plane of curvature. The primary flexural a curve.
where bending occurs about the strong stresses and deflections are in perpendicu- Variable-radius bend. Parabolic, elliptical
principal axis. lar to the plane of curvature. and other noncircular bends with variable
Heat curving. A bending process that Ovality. The cross-sectional distortion of radii. Also known as multiradius and a
relies only on the application of heat in a round HSS where the deviation from the non-circular bends.
specific patterns to induce curvature. theoretical shape forms an oval. Vertically curved member. A member
Horizontally curved member. A member Pyramid roll bending. A cold-bending with curvature in the vertical plane.
with curvature in the horizontal plane. operation where a member is bent pro- Waving. See Local buckling.
gressively by repeatedly passing it through
Hot bending. Any bending process where a set of three adjustable rolls in a pyramid Wrinkling. See Local buckling.
curvature is induced by load application at arrangement.
an elevated temperature. Yield point. The curvature at which a
Reverse-compound bend. A curve made member will deform permanently during
In-plane flexure. Bending of a curved up of two or more arcs in the same plane, bending.
member where moment is applied about joined tangentially with reversal of curvature.
the axis of curvature. The primary flexural Also known as an S-curve or an offset bend.
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