Gauge Length
In a tensile test this is the prescribed part of the cylindrical or prismatic portion of the test piece on which elongation is measured at any moment during the test.
In particular, a distinction should be made between the following:
~ The original gauge length, i.e. the gauge length before the test is started.
~ The final gauge length – The gauge length after the test is completed and the test piece has fractured. The broken pieces are carefully fitted together to lie in a straight line so that it can be measured.
Grain Flow
Elongation of the grain structure in the direction of cold working.
Grain Growth
Coarsening of the grain structure that occurs under certain conditions of heating. It is generally undesirable and is deleterious.
Grain Size
A measure of the area or volume of grains in polycrystalline material.
Grain size is reported in a number of ways
1. number of grains per unit of area or volume,
2. average diameter,
3. as a grain size number derived from area measurements and comparison with a standard chart.