Found:

Stress neutral affix

PHONOLOGY/MORPHOLOGY: a term which refers to one of the most characteristic properties of Class II affixes: the property of not having any effect on the stress pattern of the base. EXAMPLE: if we add the affix -ness to the word prodúctive, the stress is unaffected (prodúctiveness).Stress neutral affixes are distinguished from stress shifting affixes.

LIT.	Chomsky, N. and M. Halle (1968) Siegel, D. (1974)