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Author:Göös, Jussi
Title:Ruoripotkurilaitteen hitsatun rakenteen väsymismitoitus
Fatigue design of a welded azimuthing thruster structure
Publication type:Master's thesis
Publication year:2009
Pages:67 (+9)      Language:   fin
Department/School:Sovelletun mekaniikan laitos
Main subject:Lujuusoppi   (Kul-49)
Supervisor:Marquis, Gary
Instructor:Tervonen, Matti
OEVS:
Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark Aalto  5072   | Archive
Keywords:azimuthing thruster
fatigue
finite element method
hot spot stress
effective notch stress
durability
weld
ruoripotkurilaite
väsyminen
elementtimenetelmä
hot spot -jännitys
tehollinen lovijännitys
kestoikä
hitsi
Abstract (eng): The goal of this thesis was to assess the fatigue strength of the welded structure for a new generation of azimuthing thruster and to develop a suitable design methodology for the calculation of the fatigue strength of similar welded structures.

The azimuthing thruster for the thesis was modelled using the finite element method.
Loads affecting the azimuth thruster in varying operational situations were taken into account in the calculations.

FE results, measured load data and fatigue design methods for welded steel structures were combined and potential trouble spots in the thruster structure were identified.
Solutions to attain adequate fatigue strength were proposed.
The structural hot spot stress method and the effective notch stress method as defined by the International Institute of Welding were used to estimate the durability of the structures.
These verified procedures combine specific S-N curves with strict FE modelling requirements.

Regulations of the maritime classification societies and the effects of weld geometry and quality were taken into account during the assessment.
Design load spectra including cycles of various stress ranges were developed based on the expected service profile of the thruster.

The expected fatigue life, based on long-term, full-scale measurements from a large cruise ship was nearly six times higher compared to required service life of the structure.
The service life calculation was based on an upper-limit load profile that was developed based on empirical experience and a theoretical understanding of the thruster.
However, the results cannot be generalized.
Various types of vessels operating with corresponding load profiles will require further research, ship operation data, measurements, and results of analysis.
Abstract (fin): Tämän diplomityön tavoitteena oli tehdä uuden tuotesukupolven ruoripotkurilaitteen rakenteelle väsymistarkastelu ja etsiä sopiva mitoitusmenetelmä hitsatun rakenteen väsymiskestävyyden laskentaan.

Tarkastelun kohteena olevasta ruoripotkurilaitteesta oli tehty suuri elementtimalli.
Mallinnusmenetelmänä oli käytetty elementtimenetelmää.
Laskennassa oli huomioitu ruoripotkurilaitteeseen kohdistuvat kuormat erilaisissa operointitilanteissa.
Jännitystulosten pohjalta määritettiin ruoripotkurin teräsrakenteen kriittiset hitsausliitokset väsymiselle.

Väsymismitoitusmenetelmä, FE -tulokset, ja kuormitusprofiili kohdistettiin potentiaalisiin ongelmakohtiin.
Kestoiän laskennassa käytettiin International Institute of Weldingin mukaista rakenteelliseen hot spot -jännitykseen ja teholliseen lovijännitykseen perustuvaa väsymismitoitusmenetelmää.
Väsymismitoitusmenetelmän vaatiman tarkan FE -mallin avulla laskettiin rakenteen väsymiskestoikä käyttäen liitoskohtaisia SN-käyriä.
Laskennassa huomioitiin meriteollisuuden luokituslaitosten vaatimukset sekä hitsiliitosten laadun ja geometrian vaikutukset kestoikään.

Suuren risteilijäaluksen pitkäaikaisiin täysmittakaavamittauksiin perustuvalla kuormitusprofiililla saavutettiin lähes kuusinkertainen kestoikä vaadittuun verrattuna.
Kokemuksen ja teoreettisen ylärajaprofiilin tuottaman kestoiän perusteella tätä ei kuitenkaan voida pitää yleistettävänä tuloksena.
Eri alustyyppien operointeja vastaavien kuormitusprofiilien määritys vaatii vielä lisää tutkimusta, operointitietojen hankintaa, mittauksia ja tulosten analysointia.
ED:2010-02-03
INSSI record number: 38858
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