Instrument for determining static friction coefficient

FIELD: measuring engineering.

SUBSTANCE: instrument has platform pivotally connected with the base, box without bottom filled with plastic material, tie-rod device, bearing member which can be adjusted in height with spacers and guides mounted on the plate. The layer of material comprises particles. The box is connected with the platform through a damping link provided with arresting carrier.

EFFECT: enhanced accuracy of measurements.

2 dwg

 

The invention relates to measuring devices.

A known device for determining the coefficient of friction of rest, comprising a platform with a hinge mounted therein an inclined plane and a measurement scale (Shooters, L.P. Mechanics. - M.: Nauka, 1975, s).

The proposed device can be used to determine the ratio of the force of static friction of granular materials, the particles of which are rolling on inclined planes until the time of their slip. The scope of the proposed device is limited to the determination of the coefficient of friction of rest (or slow motion) between a smooth, flat bodies.

A known device (selected as a prototype) to determine the shear and friction coefficient, comprising a platform, a floating box with no bottom and pulling device (Zenkov R.L. Mechanics of bulk cargo. - M.: Mashinostroenie, 1964, p.39...47).

The proposed device provides a significant variation in measurement results due to the influence of random resistance to movement of the box - particles of the investigated material in the lower layer sliding surface, roll or rotate around the vertical axis at the initial moment of motion. And when you measure the placement of particles in the lower layer relative to the direction of the active ingredient is ment to be played.

The purpose of the invention is the improvement of measurement accuracy and repeatability of experiments.

The essence of the invention is that the device for determining the coefficient of friction of rest, including the platform on the box without the bottom and pulling device, wherein the platform is pivotally mounted on the frame for movement through a traction device and control on a scale of commencement of the slip of the box without the bottom surface of the platform, a box without the bottom filled with visco-plastic material with the ability to dive into it measured particle granular material and provided with a shock-absorbing element with restrictive leash, and regulation of immersion of the particles in a viscous plastic material is height adjustable reference circuit and guides, and support contour geometrically such a box without a bottom, and its inner portion for placement of particles of granular material has a smaller linear dimensions relative to the box without a bottom.

Figure 1 and 2 shows a schematic of the device.

Device for determining the coefficient of friction of rest contains the platform 1, pivotally mounted on the frame 2, scale 3, a box without a bottom 4, a filled plastic material 5, the pulling device 6, the control circuit 7, with the possibility of its regulation on high is through those strips 8 and the guides 9, placed on the plate 10. In the peripheral layer of plastic material 5 placed particles 11 of the bulk material, the box without the bottom 4 is connected with the platform 1 shock-absorbing element 12, for example made in the form of a spring with restrictive leash 13.

Device for determining the coefficient of friction of rest works as follows. Pre-open surface of plastic material 5 placed inside the box without a bottom 4, is heated, and the reference circuit 7 is filled in a single layer particles 11 of the bulk material. After heating the plastic material 5 a box without a bottom 4 impose a force on the support base 7 along the guide rails 9. Then the heated surface of plastic material 5 is allowed to cool down for complete relaxation of structural relations that provides reliable fixation of the particles 11. Next a box without a bottom 4 with particles 11 is placed on the surface of the platform 1, pivotally mounted on the frame 2 with the scale 3. Then the platform 1 by means of the traction device 6 slowly begin to raise. At the start of sliding of the box without the bottom 4 on the platform 1 fix the value of the friction angle on the scale 3. Shock-absorbing element 12 does not prevent the beginning of the slide of the box without the bottom 4 by choosing the backlash created weak (loose) restrictive leash. At the end of the sliding short is the KJV without the bottom 4 shock-absorbing element 12 dampens the energy of motion of the latter. The value of the coefficient of friction of rest (fTr) is determined by known its relationship with the friction angle (ϕTr)

fTr=tgϕTr.

After registration of the friction angle of the particles 11 are removed from the surface of the plastic material 5 and the experience is repeated in the same sequence. Heating of the plastic material 5 provides a reduction of its viscosity (the weakening of the structural relations) and facilitates the immersion of the particles 11 bulk materials. The amount of immersion of the particles 11 is determined from the conditions of their reliable fixation in a viscoplastic material 5, when eliminating their separation or offset at the start of the movement of the floating box 4 on the platform 1. As a viscoplastic material can be used wax, bitumen and other Guides 9 can accelerate the combination of working surfaces of the box without the bottom 4 and the reference circuit 7, when a viscoplastic material 5 saves softened state. The reference circuit 7 is made geometrically similar to the box without the bottom 4. The linear sizes of geometrically similar reference circuit 7 (the inner part, where is investigated granular material) must be less than the cross-section relative to the box without the bottom 4 so that all particles 11 are guaranteed to overlap the working surface of plastic material 5.

The device is for determining the coefficient of friction of rest allows measurement at arbitrary orientation of the particles of the bulk material in the boundary layer of plastic material and the given orientation. It extends it to allow the possibility. In particular, when searching for optimal parameters of the separation of the surfaces used in the separation of grains and impurities on the magnitude of the coefficients of friction. Separation efficiency on the magnitude of the coefficient of friction significantly depends on the location (orientation) asymmetric grains relative to the direction of sliding on the dividing surface. Fixation grains in a viscoplastic material provides certainty of experiments to study tribomechanically properties of bulk materials, thereby increasing measurement accuracy.

Device for determining the coefficient of friction of rest, including the platform on the box without the bottom and pulling device, wherein the platform is pivotally mounted on the frame for movement through a traction device and control on a scale of commencement of the slip of the box without the bottom surface of the platform, a box without the bottom filled with visco-plastic material with the ability to dive into it measured particle granular material and provided with a shock-absorbing element with restrictive leash, and regulation of immersion of the particles in a viscous plastic material is height adjustable reference circuit and guides the rich support contour geometrically similar to the box without a bottom, and its inner portion for placement of particles of granular material has a smaller linear dimensions relative to the box without a bottom.



 

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