Vol.2, No 9, 1999 pp. 895-901
UDC: 620.1'36 531
CRACK GROWTH RESISTANCE
OF CREEP DAMAGED MATERIAL
Biljana Grujić1, Stojan Sedmak2, Zijah Burzić3, Aleksandar Sedmak4
1 Lola Corporation, Lola Export, Bul. Revolucije 84, 11000 Belgrade, Yugoslavia
e-mail: sedmak@elab.tmf.bg.ac.yu, asedmak@EUnet.yu
2 Faculty of Technology & Metallurgy, Karnegijeva 4, 11000 Belgrade, Yugoslavia
3 Military Technical Institute, Niška bb, 11132 Žarkovo, Yugoslavia
4 Faculty of Mechanical Engineering, 27. Marta 80, 11000 Belgrade, Yugoslavia
Abstract. In this paper crack growth resistance of creep damaged material in thermoelectrically power plant "Kostolac A" was investigated. This was done by testing and comparison of impact, static and fatigue crack growth properties of virgin and serviced material (low-alloy steel marked 12?1M? according to GOST 10500-63), imposed to creeping during 175000 service hours. In order to obtain complete range of crack growth properties for both materials, following temperatures were selected for impact and static testing: 20oC, 400oC, 520oC, 540oC (operating temperature) and 560oC. The impact testing was done by the instrumented Charpy machine, enabling separate evaluation of crack initiation and crack growth energies. The static testing was performed by standard method of J integral measurement. The fatigue testing was done by evaluating the dependence of crack growth rate on the stress intensity factor amplitude. Furthermore, characterization of materials was done by fractographic examination. According to all these examinations crack growth resistance of creep damaged material was evaluated.
Keywords: creep, instrumented Charpy testing, J integral, fatigue, fractography
OTPORNOST PREMA RASTU PRSLINE
PUZANJEM OŠTEĆENOG MATERIJALA
U radu je istraživana otpornost prema rastu prslina puzanjem oštećenog materijala u termoelektrani "Kostolac A". To je izvedeno ispitivanjem i poređenjem udarnih, statičkih i zamornih osobina rasta prsline novog materijala i materijala izloženog puzanju tokom 175000 radnih sati (niskolegirani čelik 12?1 M? prema GOST 10500-63). Da bi se dobio puni opseg osobina rasta prslina za oba materijala za udarno i statičko ispitivanje izabrane su temperature 20oC, 400oC, 520oC, 540oC (radna temperatura) and 560oC. Udarno ispitivanje je izvedeno na instrumentiranom Charpy-jevom klatnu, koje omogućava razdvajanje energija stvaranja i rasta prsline. Statička ispitivanja su izvedena standardnim postupkom za merenje J integrala. Zamorna ispitivanja su izvedena ocenom zavisnosti brzine rasta prsline i amplitude faktora intenziteta napona. Prema ovim ispitivanjima otpornost prema rastu prsline puzanjem oštećenog materijala je ocenjena.