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NAERINGSPH-Nærings-phd

Tooth flank fracture in spiral bevel gears - material properties and fracture mechanics

Alternativ tittel: Flankebrudd i spiralkoniske drev - materialegenskaper og bruddmekanismer

Tildelt: kr 1,6 mill.

Prosjektnummer:

270828

Prosjektperiode:

2017 - 2021

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Som et resultat av arbeidet som er gjort i denne oppgaven, kan vi forbedre design og materiale på store tannhjul for prodpulsjonsutstyr, for å redusere risiko for typiske overflateinitierte tannhjulsskade som pitting, slitasje og mikropitting. I denne oppgaven er det laget en materialmodell for overflate-herdet CrNiMo-stål, en numerisk beregningsmodell for spenningstilstand og et multiaksial utmattelseskriterium er foreslått og verifisert. Omfattende utmattingstesting har vært gjennomført under varierende lastpåkjenning og fullskala-testing for å utlede en materialmodell for seigherdet CrNiMo-stål og for å verifisere det foreslåtte multiaksiale utmattelseskriteriet.

Improved understanding of gear failure mode "tooth flank fracture" in regards to the relevant stress components, an accurate representation of the material properties of carburized CrNiMo steel in the high and very high cycle fatigue regime. A set of multiaxial fatigue criteria for the fatigue prediction under Hertzian contact and conventional multiaxial fatigue loading are proposed that enable the accurate failure prediction based on the local stresses and material properties. A simplified, standardizable tooth flank fracture model based on the Dang Van criterion was developed that enables an intuitive optimization of the gear geometry.

Due to detrimental effects of subsurface cracks and resulting tooth flank fractures on the lifetime of marine bevel gears, a revised material specification and failure model need to be developed. The current models for designing and calculating bevel gears against tooth flank fracture are incomplete in regards to critical material properties such as the material cleanliness or the forging ratio and inaccurate when predicting the crack initiation region or the lifetime before failure. On the basis of systematic material testing using tensile and roller test specimens and crack detection through acoustic noise emission a revised method for the calculation of tooth flank fracture in spiral bevel gears is to be developed. It is intended to use the test results as input to an updated ISO and DNV material specification and DNV class note. Supporting the project are industry partners of entire supply chain of the bevel gear production among which there are steel producers, forging companies, gear manufacturers and the classification society. This provides the unique opportunity to solve the complex task of changing the material specification for marine gear steels.

Budsjettformål:

NAERINGSPH-Nærings-phd