Where does gall collide?

In tribology, galling is a severe form of adhesive wear in which two sliding solids, usually metals under high contact stress, locally weld together and then tear, so that material is dragged, smeared, and transferred from one surface to the other, roughening and eventually seizing the pair. Ling and Saibel's 1957 Thermal aspects of galling of dry metallic surfaces in sliding contact tied the onset of galling to frictional heating at the real contact spots. The referent is a surface-damage mechanism of sliding bodies, measured by the load or cycles at which galling starts, and it shares only the word "gall" with a plant swelling or with bile.[1]

Unit

The contact load or sliding conditions at which surfaces begin to seize and transfer material

Recovery means

Not applicable

Measured by

Assessed by threshold galling stress tests, friction traces, and surface examination of transferred material

In botany, a gall is an abnormal, often highly structured outgrowth of plant tissue produced when the plant's own development is hijacked by another organism (most often a gall-inducing insect, but also mites, nematodes, fungi, or bacteria), which redirects host growth into a shelter and food source for the inducer. Stone and Schönrogge's 2003 The adaptive significance of insect gall morphology argues that gall shape and structure are extended phenotypes of the inducer, shaped by selection for protection against enemies and the environment. The referent is a redirected plant growth controlled by a second organism, characterised by its structure and inducer, and it is unrelated to seizing metal or to bile beyond the shared word.[2]

Unit

The form and tissue organisation of the induced outgrowth and the identity of its inducer

Recovery means

Not applicable

Measured by

Characterised by gall morphology, internal anatomy, inducer species, and placement on the host