Frequency Range

The frequency range (bandwidth) over which a measurement is considered valid. Usually refers to upper frequency limit of analysis, considering zero as the lower analysis limit.

Fast Fourier Transform

A calculation method of converting a time waveform to a frequency display that shows the relationship of discrete frequencies and their amplitudes.

Flywheel effect (WR^2)

A measure of the potential of the coupling to resist change in speed. WR^2 is the product of the weight of the coupling times the square of the radius of gyration. The radius of gyration is the radius at which the mass of the part can be considered concentrated. W is the part weight in pounds; R is the radius of gyration in feet or inches; so WR^2 is expressed in lb-ft^2 or lb-in^2. For a cylinder (such as a coupling hub), WR^2 = W (Ro^2 - Ri^2'), where Ro is the outside radius and Ri is the inside radius.

Flex hub coupling

A coupling that has the external gear teeth on the hubs and internal teeth in the sleeves.

Flexing length

The axial distance between the effective flexing planes of a double-engagement coupling.

Floating shaft

Typically, a removable center member of a flexible coupling assembly that is composed of two standard half-couplings (single-engagement or single flexing) mounted on either end of a piece of shafting (solid or tubular) and is used to connect the driving and driven shafts of equipment, which are separated axially by greater than normal distances.

Flooded-mesh coupling

A continuously lubricated coupling in which the gear meshes are completely submerged in oil during normal operation.

Ferrite

A solid solution of one or more elements in body-centered cubic iron. Unless otherwise designated (for instance, as chromium ferrite), the solute is generally assumed to be carbon. On some equilibrium diagrams, there are two ferrite regions separated by an austenite area. The lower area is alpha ferrite; the upper, delta ferrite. If there is no designation, alpha ferrite is assumed.

Ferritizing Anneal

A treatment given as-cast gray or ductile (nodular) iron to produce an essentially ferritic matrix. For the term to be meaningful, the final microstructure desired or the time-temperature cycle used must be specified.

Finish Annealing

A subcritical annealing treatment applied to cold-worked low- or medium-carbon steel. Finish annealing, which is a compromise treatment, lowers residual stresses, thereby minimizing the risk of distortion in machining while retaining most of the benefits to machinability contributed by cold working. Compare with final annealing .