Hamrock-Dowson EHL quick calculator

Inputs

Use operating-point values for load, entrainment speed, lubricant properties, elastic properties, and local radii of curvature.

Operating point

Normal load, F Applied load carried by the contact. Entrainment speed, u Mean entrainment speed used by the correlation.

Lubricant

Dynamic viscosity, eta0 Viscosity at inlet or operating temperature, Pa s. Pressure-viscosity coefficient, alpha Enter in GPa^-1; 10 GPa^-1 equals 10e-9 Pa^-1.

Elastic properties

Body 1 Young’s modulus GPa. Body 2 Young’s modulus GPa. Body 1 Poisson’s ratio Dimensionless. Body 2 Poisson’s ratio Dimensionless.

Radii of curvature

Body 1 radius in x, R_x1 mm, along the entrainment/minor-axis direction. Body 2 radius in x, R_x2 mm; use a very large value for a flat surface. Body 1 radius in y, R_y1 mm, perpendicular to entrainment. Body 2 radius in y, R_y2 mm; use a very large value for a flat surface.

Notes and assumptions

The Hamrock-Dowson correlations are quick screening equations for fully flooded, isothermal, Newtonian elastohydrodynamic contacts. They are useful for lubricant and surface-separation estimates, but they do not model starvation, shear thinning, thermal thinning, transient starts, contamination, or mixed-lubrication asperity contact.

The x radius is the radius in the entrainment direction. For this quick form, reduced R_x/R_y must be less than or equal to 1.
Use the minimum film thickness with a lambda-ratio calculation when screening surface separation against roughness.
Reference: Hamrock-Dowson EHL film-thickness correlation for elliptical contact.

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Hamrock-Dowson EHL quick calculator

Inputs

Notes and assumptions

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