Freting

J. Vižintin, M. Kalin

Kovine zlitine tehnologije 33 (1999) 55–59.

Abstract

Ena izmed oblik obrabe, ki znatno zmanjšuje trajnost strojnih delov, je tudi freting obraba. Freting je delovanje, ki povzroča poškodbo, ko se dve telesi v kontaktu relativno gibljeta z majhno amplitudo pomika v tangentni smeri. Obstajajo tri osnovne oblike fretinga poškodb, to so: freting korozija, freting obraba in freting utrujanje. Vendar se v zadnjih letih uporabljata za opis poškodb predvsem freting utrujanje in freting obraba, predvsem v povezavi z različnimi freting režimi, ki opisujejo ramerje med cono mirovanja in zdrsa v kontaktu in s tem definirano poškodbo. Freting obraba in freting utrujanje nastajata praktično v vseh strojih in lahko povzročita dokončno poškodbo tudi na sicer zelo zmogljivih komponentah. Znano je, da število freting poškodb, v nasprotju z drugimi oblikami obrabe, v zadnjih desetletjih ne upada, četudi je bila izvedena vrsta raziskav na tem področju. Seznam možnih poškodb pri različnih strojih je seveda zelo dolg, vendar ga lahko skrčimo na nekaj značilnih primerov, kot so ležaji, sklopke in različni spoji. Glavni vzroki za slabo poznanje fretinga, in s tem tudi njegovo odpravljanje, so v kompleksnosti samega procesa, različnih vplivih kontaktnih razmer, številnih materialih in okoliških razmerah. Sedaj potekajo glavne raziskave na področju izpopolnjevanja že obstoječih kriterijev pri določevanju poškodb freting utrujanja, njegovem modeliranju, napovedovanju in preprečevanju. Na drugi strani pa obstoji tudi obsežna raziskovalna aktivnost na področju freting obrabe in iskanju boljših meril za določitev prehoda med freting obrabo in freting utrujanjem.

One of the wear forms which significantly limits the operating life of various machine components and structures is also fretting wear. Fretting is the action which causes fretting damage when two contacting bodies are subjected to a relative oscillatory tangential motion of small displacement amplitude. There exist three main forms of fretting and related damages, i.e. fretting corrosion, fretting wear and fretting fatigue. However, in recent years fretting wear and fretting fatigue are mostly used for defining the fretting damage, primarily in connection with specific fretting regimes, which describe the relation between the slip and stick zones in the contact and thus the resultant wear form. Fretting wear and fretting fatigue are present in almost all machinery and are the cause of total failure of some otherwise robust components. Survey reveals that, unlike other forms of wear, the incidence of fretting problems in machinery has not declined over the past decades, inspite of many years of recognizing and studying fretting damage. The list of potential fretting damage situations is, of course, very long but can be reduced to the three characteristic situations: bearings, couplings, and joints. The main reasons for the lack of a more stringent definition of fretting and its better prevention are the complexity of the process itself, the effects of the prevailing contact conditions, the materials in contact and the surrounding environment. Investigations are nowadays oriented on the improvement of the already established criterias for the fretting fatigue damage, its modelling, prediction and consequently prevention. On the other hand, strong research activities are also in the field of fretting wear and finding better criterias to distinguish the transition between the fretting wear and fatigue.

Keywords: freting, mehanika, freting režimi, freting sheme, ležaji, keramika, fretting, mechanics, fretting regime, fretting maps, bearings, ceramics

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