EN
| BASICS | |
|---|---|
| ACTIVE COILS | Those coils which are free to deflect under load. |
| FREE LENGTH | The overall length of a spring in the unloaded position. |
| SOLID HEIGHT (CLOSED LENGTH) | Height of a compression spring when under sufficient load to bring all coils into contact with adjacent coils. |
| PITCH | The distance from center to center of the wire in adjacent active coils. |
| MEAN COIL DIAMETER | Outside spring diameter minus one wire diameter. |
| ENDS | The configuration of the end coils of a spring (see types below). |
| HOOKS / LOOPS | Open loops or ends of extension springs used for attachment and force application. |
| INITIAL TENSION | The force that keeps the coils of an extension spring closed and must be overcome before the coils start to open. |
| LOAD | The force applied to a spring that causes a deflection. |
| DEFLECTION | The motion of spring ends or arms under the application or removal of an external load. |
| HELIX | The spiral form (open or closed) of compression, extension and torsion springs. |
| TOTAL NUMBER OF COILS | The number of active coils plus the coils forming the ends. |
| ACTIVE COILS (n) | The number of coils that actually deflect and store energy. |
| SPRING INDEX (C) | The ratio of the mean coil diameter (D) to the wire diameter (d). C = D / d |
| SLENDERNESS RATIO (L/D) | The ratio of spring length (L) to mean coil diameter (D). |
| END TYPES (COMPRESSION SPRINGS) |
Open Ends, Not Ground |
| PERFORMANCE & PROPERTIES | |
|---|---|
| RATE (SPRING RATE) | Change in load per unit deflection. Typically expressed in pounds per inch. |
| ELASTIC LIMIT | Maximum stress to which a material may be subjected without producing permanent set. |
| ENDURANCE LIMIT | Maximum stress at which a material will operate indefinitely without failure for a given minimum stress. |
| FREQUENCY (NATURAL) | The lowest inherent rate of free vibration of a spring itself (usually in cycles per second) with ends restrained. |
| HYSTERESIS | The mechanical energy loss that always occurs under cyclic loading and unloading, proportional to the area between the loading and unloading load-deflection curves within the elastic range. |
| STRESS RANGE | The difference in operating stresses at minimum and maximum loads. |
| TORQUE | A twisting action in torsion springs which tends to produce rotation, equal to the load multiplied by the distance (or moment arm) from the load till the axis of the spring body. |
| MODULUS IN SHEAR (G) | Coefficient of stiffness for extension and compression springs. |
| MODULUS IN TENSION OR BENDING (E) | Coefficient of stiffness used for torsion and flat springs (Young's Modulus). |
| MATERIAL & PROCESS | |
|---|---|
| HEAT SETTING | Fixturing a spring at elevated temperature to minimize loss of load at operating temperature. |
| SHOT PEENING | A cold working process in which the material surface is peened to induce compressive stresses and thereby improve fatigue life. |
| STRESS RELIEVE | To subject springs to low-temperature heat treatment so as to relieve residual stresses. |
| RESIDUAL STRESS | Stresses induced by set removal, shot peening, cold working, forming or other means. |
| PASSIVATING | Acid treatment of stainless steel to remove contaminants and improve corrosion resistance. |
| 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. |
SET
Length loss in operation due to the high stress condition of the spring.
PRESET (REMOVE SET)
Full compression of a spring to solid state by manufacturer when needed to prevent length loss in operation.
SQUARENESS OF ENDS
Angular deviation between the axis of a compression spring and a normal to the plane of the ends.
PERMANENT SET
A material that does not return to its original condition upon release of load is said to have taken a "permanent set".
ANGULAR RELATIONSHIP OF ENDS
The relative position of the plane of the hooks or loops of extension springs to each other.
SQUARENESS UNDER LOAD
Same as squareness of ends, except with the spring under load.
Note: Terminology definitions follow recommended industry practices for spring design and manufacturing.