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Damage characterization of aluminum 2024 thin sheet for different stress triaxialities

Majzoobi G. H., Kashfi M., Bonora N., Iannitti G., Ruggiero A., Khademi E.

Archives of Civil and Mechanical Engineering

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2018

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Vol. 18, no. 3

702--712

EN

Due to its attractive mechanical properties, aluminum 2024 is widely used in aircraft manufacturing industries, especially as fiber metal laminates, such as GLARE. In the present work, a series of experiments for different stress triaxialities are used to study the ductile damage of Al 2024 considering continuum damage mechanics (CDM). Stress triaxiality is produced using notched specimens. The main objective of the present study is to predict the local equivalent plastic strain to fracture and introducing a relation which describes the effect of stress triaxiality factor (TF) on it in the medium range of stress triaxiality. Hence, a nonlinear damage model is utilized for Al 2024 and its parameters are determined by an experimental/numerical/optimization procedure using tensile test on plain specimens. The experiments showed that for large notch specimens (Al-NL) and medium notch samples (Al-NM) fracture started from the center of the notch root of the specimens, whereas for small notched specimens (Al-NS) the failure initiated from the notch root surface. Finite element simulations are performed using the presented nonlinear damage model and are compared with the experimental data. Results show that the proposed damage model can predict the damage evolution for different stress triaxialities.

2

Theoretical investigation on the static properties of the finite porous journal bearings

D'Agostino V., Guida D., Ruggiero A., Senatore A.

International Journal of Applied Mechanics and Engineering

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2004

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Vol. 9, no spec.

321-328

EN

A theoretical analysis is carried out to determine the analytical approximate description of the fluid film force of porous finite journal bearings. The investigation has been conducted assuming the Warner solution for the pressure field and the approximate analytical solution for the long porous journal bearings proposed by D'Agostino et al. (2004). The analytical approach for studying the behaviour of a system is more effective than a numerical one because of it allows to cover not only the individual case but the whole class to which the system belongs. Furthermore, the model proposed allows a quick analytical determination of the fluid film force for different values of the permeability coefficient, L/D ratio, eccentricity ratio. The results are in good agreement with those achieved by means of the FDM based solution.

3

An analytical solution for the pressure field in the long porous journal bearings

D'Agostino V., Guida D., Ruggiero A., Senatore A.

International Journal of Applied Mechanics and Engineering

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2004

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Vol. 9, no spec.

313-319

EN

Analytical solutions of the Reynolds equation for the porous journal bearings are not generally achievable and numerical methods must be involved. This paper presents an approximate mathematical model for the one-dimensional lubrication equation for the infinitely long porous journal bearing, obtaining a good agreement over the ranges of operating conditions of this tribological component.

4

On the hydrodynamic pressure field between piston top ring and cylinder liner in an internal combustion engine

Ruggiero A., Senatore A.

International Journal of Applied Mechanics and Engineering

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2002

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Vol. 7, Spec. is

87-92

EN

The lubrication of the piston ring is an important subject for many research activity, because of the interaction at the piston ring-cylinder interface provides substantial influence on the friction, wear, oil consumption and power loss in an internal combustion engine. This paper is a contribution on the analyses of the effect of oil viscosity, pressure drop, piston speed and minimum film thickness on the top ring friction force, taking into account the ring approach motion to the cylinder liner by solving with an approximate model the two-dimensional Reynolds equation.

5

Analytical fluid film force in the turbulent journal bearings

D'Agostino V., Guida D., Ruggiero A.

Applied Mechanics and Engineering

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1999

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Vol. 4, no spec.

25-31

EN

The aim of this paper is to illustrate a method to determine the analytical description of non-steady fluid film force and of the stiffness and damping coefficients for the "short" liquid-lubricated journal bearings in a fully developed turbulent flow regime. The equation goveming the distribution of pressure around the bearing has been solved analytically; the models has been developed assuming lubricant flow is isoviscous.