Lubrificazione termoelastoidrodinamica e tribologia

The research topic includes numerical modeling and design of (lubricated) kinematic pairs as well as the integration of the pair components with the remaining machine elements.
The fields of application concern automotive (study of bearings for internal combustion engines), the generation of energy and power (study of bearings for turbomachinery) and biomechanics (study of prostheses).
The tools used to study the tribological problems at the hand are primarily numerical simulations, but in the near future experimental activities will be started.
Current research includes the development of methods and codes for the thermoelastohydrodynamic (TEHD) lubrication analysis, performed by means of numerical methods and especially the finite element method (FEM).
TEHD analysis is multidisciplinary as it studies the thermomechanical interaction between lubricating fluids and structures. Therefore, it requires the coupled simulation of both the hydrodynamic oil film in laminar, superlaminar, turbulent flow conditions, and the thermo-mechanical behavior of the members of the kinematic pair.
It allows an accurate estimate of the bearing capacity, friction, wear as well as mechanical and thermal stresses in kinematic pairs operating in hydrodynamic, elastohydrodynamic and mixed lubrication regime.
Figure 1 shows stress (von Mises) and deformation in the load cycle of a connecting rod for high-performance internal combustion engine calculated by means of elastohydrodynamic analysis . The preload of the bolts has been deliberately lightened to simulate the opening of the body and cap.
Figure 2 shows the trend of the pressure distributions in a bearing of a connecting rod during the load cycle calculated by means of elastohydrodynamic analysis .
Figure 3 shows the temperature distribution in the film thickness of a radial bearing calculated by termohydrodynamic analysis.

Publications

Stefani, F., e Rebora, A., 2001, “Elastohydrodynamic Analysis of a Connecting Rod Bearing for High Performance Engines”, Proc. of the 2nd World Tribology Congress (WTC 2001), Vienna, Austria, 3-7 settembre 2001, “Young Tribologist Award 2001”.
Stefani, F., e Rebora, A., 2002, “Finite Element Analysis of Dynamically Loaded Journal Bearings: Influence of the Bolt Preload,” ASME Journal of Tribology, 124, pp. 486-493.
Stefani, F., e Rebora, A., 2004, “A Nonlinear Structured Based  Elastohydrodynamic Analysis Method for Connecting Rod Big End Bearings of High Performance Engines”, ASME Journal of Tribology, 126, pp. 664-671.
Stefani, F., “FEM Applied to Hydrodynamic Bearing Design”, in “New Tribological Ways”, edito da Taher Ghrib, InTech, Open Access Publisher, Rijeka, Croatia, 2011, pp.451-476.
Stefani F., “Design and fast verification of pocket elliptical journal bearings”, Industrial Lubrication and Tribology, Emerald, Vol. 66, Number 3, 2014, pp. 393–401, “Highly Commended Paper 2014”.