Low Pass Filter

A filter whose transmission band extends from an upper cutoff frequency down to DC.

Linear, non-linear

When the vibration levels are trended over time and the trend is a straight line, either rising or falling, the trend is referred to as linear because the amount of increase is the same for each equal increase in time. A non-linear increase would be the case where, as time progresses, the amplitude increases or decreases, at a larger and larger amount, each time frame. Projections can be made from linear trends, they cannot be made from none-linear trends.

Lines

Common term used to describe the filters of a Digital Spectrum Analyzer (e.g. 400 line analyzer).

Lateral coupling stiffness, radial

The ratio of force to displacement while the coupling is being deflected in a plane perpendicular to the coupling axis of rotation.

Lateral shaft offset

The lateral distance between the centerlines of two coupled shafts that are not parallel measured at the axial reference point of the driving machine shaft.

Limited-end-float coupling

A coupling designed to limit the movement of the coupled shaft ends with respect to each other where one shaft has no thrust bearing for centering. A limited-end-float design is commonly used in couplings for sleeve-bearing motors.

Low cycle fatigue

The regime characterized by high overstress (exceeding the yield limit) where life is usually below 103-104 cycles.

Low-speed coupling

A coupling designed to operate at a surface velocity below 2300 in./sec. For a low-speed coupling, V = D x rpdl9, where D is the maximum outside diameter of the coupling in inches.

Liquid Nitriding

A method of surface hardening in which molten nitrogen-bearing, fused-salt baths containing both cyanides and cyanates are exposed to parts at subcritical temperatures.

Liquid Nitrocarburizing

A nitrocarburizing process (where both carbon and nitrogen are absorbed into the surface) utilizing molten liquid salt baths below the lower critical temperature.