What is the difference between reciprocated and non-reciprocated sliding?

A general summary on tribonet.org of a recent published paper in Tribology International where Feng-Chun Hsia and coworkers systematically compare the friction and wear behavior of reciprocated and non-reciprocated contacts with surprisingly results.

What is the difference between reciprocated and non-reciprocated sliding?
Feng-Chun Hsia, Bart Weber
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