Procjena cjelovitosti i radnog vijeka posude pod tlakom

master's thesis

• Title (english): Structural integrity assessment and life prediction of pressure vessel
• Author: Marko Vračarić
• Mentor: Ivica Skozrit (mentor)
• Granter: University of Zagreb; Faculty of Mechanical Engineering and Naval Architecture; Zagreb
• Defense date and country: 2017-12-08, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Mechanical Engineering; General Mechanical Engineering (Construction)

Abstract

U diplomskom radu opisane su teorijske osnove mehanike loma prema kojima se procjenjuje cjelovitost i životni vijek konstrukcijske komponente. Procjena cjelovitosti za tlačnu opremu opisana je normom API 579. Verifikacija analize zamora provedena je na ploči s kružnim provrtom, a za debelostjenu i tankostjenu posudu pod tlakom uspoređen je broj ciklusa do iniciranja pukotine. X-FEM formulacija i singularni konačni elementi verificirani su na vlačno opterećenoj ploči sa središnjom pukotinom i ploči s centralnom polueliptičnom pukotinom, pri čemu su proračunati koeficijenti intenzivnosti naprezanja. Koeficijent intenzivnosti naprezanja opisuje polje naprezanja oko vrha pukotine za linearno-elastično ponašanje materijala, a J-integral za elastoplastično. Za posudu pod tlakom uspoređeni su sljedeći slučajevi: uzdužna unutarnja, uzdužna vanjska, cirkularna unutarnja i crikularna vanjska polueliptična pukotina. Parametre mehanike loma moguće je odrediti shell-to-solid podmodeliranjem uz pravilno odabranu veličinu podmodela. Najveće opterećenje posude pod tlakom određeno je graničnim tlakom ili plastičnim kolapsom. Određivanje J-integrala računa se GE/EPRI metodom i metodom referentnog naprezanja. Uslijed prirasta opterećenja ili rasta pukotine, dijagramom procjene loma (FAD) i dijagramom razvoja pukotine (CDF) može se analizirati cjelovitost posude pod tlakom. Stabilan rast pukotine unutar posude pod tlakom opisan je Parisovim modelom za linearno-elastično ponašanje materijala i Dowling-Begleyevim modelom za elastoplastično.

Abstract (english)

In graduate thesis are described theoretical bases of fracture mechanics which enable life assessment and structural integrity assessment for structural components. The structural integrity assessment is described by API 579 design codes and standards for pressurized equipment. Fatigue analysis verification is obtained on the circular bore plate and the number of cycle to initiate the crack are compared for thick-walled and thin-walled pressure vessel. X-FEM formulation and singular finite elements are verified on the finite-width plate with centar crack and semi-elliptical centar crack under tensile load, stress intensity factors included. The stress intensity factor describes a stress field around the crack tip for linear-elastic material behaviours and the J-integral for elastic-plastic material behaviours. The following cases are compared for the pressure vessel: longitudinal inner and outer, circular inner and outer semi-elliptical cracks. Fracture mechanics parameters can be determined by shell-to-solid sub-modelling with a properly selected sub-model size. Maximal load of pressure vessel is defined by limit load or plastic collapse. J-integral is calculated by

GE/EPRI method or reference stress method. Failure assessment diagram (FAD) and crack driving diagram (CDF) can be used for pressure vessel structural integrity assessment due to crack growth or load increase. Stable crack growth inside the pressure vessel is described by

the Paris model for linear-elastic material behaviours and Dowling-Begley’s model for elastic-plastic material behaviours.

• Keywords: mehanika loma.; metoda konačnih elemenata.; koeficijent intenzivnosti naprezanja.; J-integral.; granično opterećenje.; plastični kolaps.; GE/EPRI metoda.; metoda referentnog naprezanja.; procjena cjelovitosti posude pod tlakom
• Keywords (english): fracture mechanics.; finite element method.; stress intensity factor.; J-integral.; limit load.; plastic collapse.; GE/EPRI method.; reference stress method.; structural integrity assessment of pressure vessel
• Language: croatian
• URN:NBN: urn:nbn:hr:235:366043
• Study programme: Title: Mechanical Engineering; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra inženjer/inženjerka strojarstva (magistar/magistra inženjer/inženjerka strojarstva)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2019-05-22 21:02:42