METHOD OF DETERMINING STATIC AND DYNAMIC COEFFICIENT OF EXTERNAL FRICTION Russian patent published in 2015 - IPC G01N19/02 

FIELD: testing technology.

SUBSTANCE: to determine the static and dynamic coefficients of external friction two samples are used: the basic and the movable. The basic sample is made with a concave spherical or cylindrical working surface which has a horizontal axis, and the ability of its rotation about this axis is provided. The movable sample is made with a flat or convex supporting surface with a radius not less than the radius of the working surface of the basic sample, it is mounted in the lower part of the working surface of the basic sample and the basic sample is rotated about the axis, measuring the angle between the line connecting the centre of the supporting surface of the movable sample with the axis of rotation of the working surface and the vertical passing through the axis of rotation, the angle φ₁ is measured, in which the movable sample slides, and the angle φ₂ in which sliding ends, the static coefficient of external friction m_st=tgφ₁ is determined, and the dynamic coefficient of external friction $$m_{dyn}=k\frac{\left(\cos {\phi }_1-\cos {\phi }_2\right)}{\left(\sin {\phi }_2-\sin {\phi }_1\right)},$$ where $$k=\frac{\left(R-l\right)}{R},$$ R is the radius of the working surface of the basic sample, l is the distance between the centre of gravity of the movable sample and the working surface of the basic sample.

EFFECT: possibility of determining in a single experiment of static and dynamic coefficients of external friction.

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