Vol.3, No 13, 2003 pp. 707-714
UDC 620.1 539.388.1
MODELLING OF A MATERIAL DEGRADATION
AND DAMAGE MECHANICS IN MACHINE STRUCTURES
UNDER SERVICE LOADING
Jozef Čačko
Institute of Materials and Machine Mechanics, Slovak Academy of Sciences
Račianska 75, SK-831 02 Bratislava 3, Slovak Republic
E-mail: ummscac@savba.sk
Problems of fatigue life estimation of materials and structures are discussed
in the paper. Service loading is assumed as a continuous loading process
with possible discontinuous events, which are caused by various operating
manoeuvres. The damage mechanics in a material is due to a cumulative degradation
process, which corresponds to formation of closed hysteresis loops in the
stress-strain diagram. The damaging process is then represented either
by rain-flow matrices or by a fatigue damage function. The fatigue damage
function is derived using some hypothesis of a fatigue failure criterion.
The method enables a very effective estimation of a service life and/or
reliable evaluation of residual life of any complicated machine structures
under various types of loading and environmental conditions. This approach
creates a good basis for CAD/CAE technologies and for powerful expert systems
in structural and machine engineering.
MODELIRANJE DEGRADACIJE MATERIJALA I MEHANIKA
OŠTEĆENJA KOD MAŠINSKIH STRUKTURA
PRI SERVISNOM OPTEREĆENJU
U ovom radu razmotreni su problemi procene trajanja materijala i struktura
pri zamoru. Pod servisnim opterećenjem podrazumeva se kontinuirani proces
opterećivanja uz moguče slučajeve diskontinuiranja, koji su uzrokovani
raznim radnim manevrima. Mehanika oštećenja u materijalu postoji usled
kumulativnog procesa degradacije, koji odgovara stvaranju zatvorenih histerezijskih
petlji u dijagramu napon-dilatacija. Proces oštećenja je tada prikazan
ili preko "kišovitih" matrica, ili preko funkcije oštećenja zamorom. Funkcija
oštećenja zamorom izvodi se korišćenjem neke hipoteze kriterijuma loma
usled zamora. Metod omogućava veoma efikasnu procenu servisnog trajanja
i/ili pouzdanu procenu zaostalog trajanja ma kojih komplikovanih mašinskih
struktura pri različitim vrstama opterećenja i uslovima okoline. Ovaj pristup
pruža dobru osnovu za CAD/CAE tehnologije i za moćne stručne sisteme u
tehnici konstrukcija i mašina.
