Active
coils (n)
Those coils which are free to deflect under load. |
Open
ends, ground
Open ends, not ground followed by and end grinding operation. |
Angular
relationship of ends
The relative position of the plane of the hooks or loops of
extension springs to each other. |
Passivating
Acid treatment of stainless to remove contaminants and improve
corrosion resistance |
Buckling
Bowing or lateral deflection of compression springs when compressed,
related to the slenderness ratio (L/D). |
Permanent
set
A material that is deflected so far that its elastic properties
have been exceeded and it does not return to its original condition
upon release of load is said to have taken permanent set. |
Closed
ends
See Squared Ends. |
Pitch
(P)
The distance from center to center of the wire in adjacent active
coils (recommended practice is to specify number of active coils
rather than pitch). |
Closed
and ground ends
See Squared and Ground Ends. |
Preset
The process of compressing a spring to solid height to remove
any permanent deformation due to exceeding the elastic limit
of the material, with an apparent increase in the elastic limit |
Closed
length
See Solid Height. |
Rate
(R)
Change in load per unit deflection, generally given in pounds
per inch. |
Close-wound
Coiled with adjacent coils touching. |
Relative
position
See Angular relationship of ends. |
Coils
per inch
See Pitch. |
Remove
Set
See Preset |
Deflection
(F)
Motion of spring ends or arms under the application or removal
of an external load (P). |
Residual
stress
Stresses induced by set removal, shot peening, cold working,
forming or other means. These stresses may or may not be beneficial,
depending on the application. |
Direction
of coiling - or Helix
Right or left hand as in screw system. Should be optional, unless
specifically required. |
Set
Permanent distortion which occurs when a spring is stressed
beyond the elastic limit of the material. |
Elastic
limit
Maximum stress to which a material may be subjected without
permanent set. |
Shotpeen
Hurtling small steel shot against springs to clean surface and
trap beneficial surface stresses, thereby increasing fatigue
life. |
Endurance
limit
Maximum stress at which any given material will operate indefinitely
without failure. |
Slenderness
ratio
Ratio of spring length (L) to mean coil diameter (D). |
Free
angle
Angle between the arms of torsion spring when the spring is
not loaded. |
Solid
Height (H)
Length of compression spring when under sufficient load to bring
all cold into contact with adjacent coils. |
Free
length (L)
The overall length of a spring in the unloaded position. |
Spring
Index
D/d, ratio of mean diameter to wire diameter. Best ratio is
between 7 and 13. Troublesome if less than 4 or over 16. |
Gradient
See Rate (R). |
Squared
and ground ends
End finish for compression springs where pitch of the end coils
is reduced so that the end coils touch and the end is then ground
to provide a flat end. |
Helix
The spirul form (open or closed) of compression, extension,
and torsion springs. |
Squared
ends
Angular deviation between the axis of a compression spring and
a normal to the plane of the ends. |
Hooks
Open loops or ends of extension springs. |
Squareness
of ends
Angular deviation between the axis of a compression spring and
a normal to the place of the ends. |
Hydrogen
embrittlement
Hydrogen absorbed in electroplating or pickling of carbon steels,
tending to make the spring material brittle and susceptible
to cracking and failure, particularly under sustained loads. |
Squareness
under load
As in Squareness of ends, except with the spring under load. |
Hysteresis
The mechanical energy loss that always occurs under cyclic loading
and unloading of a spring, proportional to the area between
the loading and unloading load-deflection curves within the
elastic range of a spring. |
Stress
relieve
Low-temperature heat treatment to relieve residual stresses
induced during coiling or forming so that springs will be more
stable, more capable of withstanding higher stresses and have
longer fatigue life. |
>Index
See Spring Index. |
Torque
(M)
A twisting action in torsion springs which tends to produce
rotation, equal to the laod multiplied by the distance (or moment
arm) from the load to the axis of the spring body. Usually expressed
in inch-oz., inch-pounds or foot-pounds. |
Initial
Tension
The force tending to keep the coils of an extension spring closed
which must be overcome before the coils start to open. A design
consideration generally specified only as a refrence dimension. |
|
Load
(P)
The force applied to a spring that causes a deflection (F). |
|
Loops
Coil-like wire shapes at the ends of extension springs that
provide for attachment and force application. |
|
Mean
coil diameter (D).
Outside spring diameter (O.D.) minus one wire diameter (d). |
|
Modulus
in shear or torsion (G).
Coefficient of stiffness used for extension and compression
springs. |
|
Modulus
in tension or bending (E).
Coefficient of stiffness used for torsion and flat springs (Young's
Modulus). |
|
Moment
(M)
See Torque. |
|
Open
ends, not ground
Ends of a compression spring with a constant pitch for each
coil. |
|
