Global Bearing Defect

Relatively large damage on a bearing element.

Gear Mesh Frequency

The frequency generated by two or more gears meshing teeth together.

Gear coupling

A coupling that transmits torque and accommodates angular misalignment, parallel offset, and axial displacement by a relative rocking and sliding motion between mating, profiled gear teeth.

General-purpose coupling

A coupling that transmits power between the rotating shafts of two machines for general-purpose applications. Such applications will typically require couplings to transmit power at speeds not exceeding 3800 rpm between machines in which the first lateral critical speed is above the running speed range (stiff shaft machines). This coupling is often a standard type that can be selected from a catalogue.

Grid coupling

A coupling that consists of two flanged hubs with slots or grooves in the flanges, connected by a serpentine mechanical flexible element.

Grain Size

For metals, a measure of the areas or volumes of grains in a polycrystalline material, usually expressed as an average when the individual sizes are fairly uniform. In metals containing two or more phases, the grain size refers to that of the matrix unless otherwise specified. Grain sizes are reported in terms of number of grains per unit area or volume, average diameter, or as a grainsize number derived from area measurements.

Graphitization

Formation of graphite in iron or steel. Where graphite is formed during solidification, the phenomenon is called primary graphitization; where formed later by heat treatment, secondary graphitization.

Graphitizing

Annealing a ferrous alloy in such a way that some or all of the carbon is precipitated as graphite.

Grossmann Chart

A chart describing the ability of a quenching medium to extract heat from a hot steel work-piece in comparison to still water.

Guinier-Preston (G-P) Zone

A small precipitation domain in a supersaturated metallic solid solution. A G-P zone has no welldefined crystalline structure of its own and contains an abnormally high concentration of solute atoms. The formation of G-P zones constitutes the first stage of precipitation and is usually accompanied by a change in properties of the solid solution in which they occur.