Properties | School of Materials Science and Engineering

The strain point is the maximum temperature at which a glass can be used for structural applications without undergoing creep. SkiptoMainContent Search UNSWSydney Science Ourschools MaterialsScience&Engineering Engagewithus Highschoolstudentsandteachers Onlinetutorials Ceramics Glass Properties Properties Duetoitsamorphousstructure,aglassatroomtemperatureisessentiallyaveryviscousliquid.Viscousflowtakesplaceinglassbutsoslowastobeonageologicaltimescale. Theviscosityofglasschangeswithtemperature.Therearefourstandardtemperaturepointsthatareusedinglassworkingtodefinetheviscosity.Thesepointsareknownasstrain,annealing,softening,andworking. Thestrainpointisthemaximumtemperatureatwhichaglasscanbeusedforstructuralapplicationswithoutundergoingcreep. Themajorityofglassformingoperationsoccurbetweenthesofteningpointandtheworkingpoint.Atthesofteningpointtheglasswillyieldwithasmallamountofforcewhileattheworkingpointtheglasshastheviscosityofhoney. Theannealingpointisthetemperaturetowhichaglassmaybeheatedafterworkingtorelieveanyinternalstressesthataroseasaresultoftheformingprocess. Aswellasanincreaseinviscosity,glassundergoesathermalcontractionwhenitiscooleddown. Whencoolingathightemperaturestheglassundergoesarapiddecreaseinvolume.Glassatthisstagehasasoftrubberytexture.Atsomepointtheglasstransformstoahardbrittletextureandtheglasscontractsataslowerrate. ThetemperatureatwhichthistransformationoccursisknownastheGlassTransitionTemperature, Tg.