Tribological aspects must be taken into account for a sustainable design of new components and materials developed to obtain weight reduction and greater efficiency. Reducing friction and wear produces energy and material savings, both connected with several Sustainable Development Goals. To limit the time consuming expensive experimental tests on new materials and components, simulations can be performed for which reliable values of the friction coefficient are necessary. In this work, some basic aspects of the lubrication regimes are firstly reviewed with the related friction coefficient trends represented with the Stribeck and Lambda curves, also evidencing the reasons of the similarity between the two curves. Formulas and diagrams are then reported for the friction coefficient of full lubricated conformal pairs. For thrust bearings the friction coefficient f can be expressed as a function of the parameter m and is related to the Kingsbury number K. For tilting pads f is proportional to K the power of 0.5. For plain journal bearings f is a function of the dimensionless eccentricity ε and is related to the the Sommerfeld number S to powers ranging roughly from 0.5 to 0.8 depending on the ratio between the axial length and the diameter for S smaller than 0.1, and tending to 1 for higher values of S. The reported formulas and diagrams can be used for design purpose.
Friction Models for a Sustainable Design: Friction Coefficient in Lubricated Conformal Pairs
Ciulli E.
2023-01-01
Abstract
Tribological aspects must be taken into account for a sustainable design of new components and materials developed to obtain weight reduction and greater efficiency. Reducing friction and wear produces energy and material savings, both connected with several Sustainable Development Goals. To limit the time consuming expensive experimental tests on new materials and components, simulations can be performed for which reliable values of the friction coefficient are necessary. In this work, some basic aspects of the lubrication regimes are firstly reviewed with the related friction coefficient trends represented with the Stribeck and Lambda curves, also evidencing the reasons of the similarity between the two curves. Formulas and diagrams are then reported for the friction coefficient of full lubricated conformal pairs. For thrust bearings the friction coefficient f can be expressed as a function of the parameter m and is related to the Kingsbury number K. For tilting pads f is proportional to K the power of 0.5. For plain journal bearings f is a function of the dimensionless eccentricity ε and is related to the the Sommerfeld number S to powers ranging roughly from 0.5 to 0.8 depending on the ratio between the axial length and the diameter for S smaller than 0.1, and tending to 1 for higher values of S. The reported formulas and diagrams can be used for design purpose.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
