METHOD OF DETERMINATION OF DYNAMIC COEFFICIENT OF EXTERNAL FRICTION WITH REFERENCE TO ROTATING SPHERICAL SURFACE Russian patent published in 2015 - IPC G01N19/02 

FIELD: test equipment.

SUBSTANCE: in the method for determination of dynamic coefficient of external friction two samples are used. The lower sample is made with convex spherical surface and is rotated around the vertical axis of this surface. The upper sample has thin walls, it has the shape of the regular geometrical figure, with the concave working surface to provide contact with the lower sample along the whole perimeter of the upper one. The upper sample by means of the hinged link able to rotate in any angular direction is connected to the support able to move in any direction. For determination of dynamic coefficient of external friction by change of coordinates of the support or the length of hinged link the upper sample is brought into the position in which the line passing through the centre of spherical surface and the centre of the place of contact of the upper sample with the lower one is perpendicular to the hinged link. Then the plane, tangential to spherical surface in the centre of contact of the upper sample with lower one is identified, the line of maximum slope in this plane is identified, the angle of its slope φ with reference to the horizon, the angle β between the line of the maximum slope and the direction of hinged link is determined, then the dynamic coefficient of external friction is determined by the formula $$m_{dyn}=\frac{tg\phi }{ctg\beta }.$$

EFFECT: possibility of determination of dynamic coefficient of external friction on the details with spherical surfaces in heavy duty durable assemblies, simplicity of implementation and possibility to be reduced to determination only of geometrical parameters.

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