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Общие методики
Technique of the roughness testing
The developer is FSUE VNIIMS
1. Purpose and range of application
This document is concerned with a measurement technique of roughness parameters of hard-to-reach surfaces (for example, holes of small diameters, slots, grooves, counter drafts, members of large-sized articles etc) and surfaces of the composite shape (clutch prongs and slots, concave spheric surfaces, threads, cog-wheels etc) articles while handling, maintenance and repairing with the help of imprints from polymeric composition replica casting materials such as "Kompar-P".
Applying of "Kompar-P" generally allows to get imprints from the surfaces that have roughness parameters Ra in range 0,04…10 microns, with an aberration from a parameter value on the surface no more than 20 %.
2. Measuring of a surface roughness with the help of imprints
Measuring of a surface roughness with the help of imprints consists of two stages:
- Manufacture of imprint from a measured surface;
- Measuring of roughness parameters of an imprint.
2.1. Manufacture of imprint from a measured surface
2.1.1. Properties of replica casting material
Used composite replica casting material "Kompar-P" is intended for getting solid imprintк from a metal, glass and other surfaces from compatible materials for consequent instrumental control and visual inspection of roughness parameters of a surface on obtained imprint.
"Kompar-P" refers to the composites of chemical curing manufactured from mixture of nonvolatile dimethylmethacrylates with inorganic filler. "Kompar-P" is produced as two pastes (the catalyzer - accelerate paste A and basic - peroxide paste B) of different colors, that are polymerized after their mixturing in the ratio 1:1 on volume basis. "Kompar-P" does not irritate the skin, it is not toxic, and it is flammable. Polymerization of the mixture of pastes runs with heat evolution.
The consistence of got casted mass allows making imprints from the surfaces located under different angles to horizon.
In connection with that obtained imprint may be stored for a long time (3-4 years) without modification of geometrical parameters, at quantity production of the same type details it is possible to use imprint as a model detail for visual comparison with an inspected surface or another imprint.
2.1.2. The procedure of imprint manufacturing
To carry out preparation of a measured surface and casted material, and then to receive an imprint from an inspected surface according to the Application Guide of composite replica casting material "Kompar-P".
After removal of an imprint to clear a measured surface according to The Application Guide of casted material.
2.2. Measuring of roughness parameter of the surface of an imprint
According to the directions for use of the article for measuring of a surface roughness to measure on an imprint roughness parameter that is given in engineering specifications on a measured surface (Ra, Rz or Rmax). Then after having selected an amount and a disposition of leases of measurings on a surface according to МИ 41-88 "GSI. The method of application of execution of measurings of parameters of a surface roughness in accordance with GOST 2789-73 by means of units profile method". The results depend on the given inaccuracy of measurements.
In a case when the inaccuracy imported by use of imprint, particular for general cases in 20 %, is reasonable to make an inference about magnitude of roughness parameter of inspected surface according to the results of measurements of the imprint or to deposit in allowance for magnitude of +20 % (as at copying there is a diminution of altitudes of irregularities at the expense of effect онедоощупыванияп at the bottom of troughs). It is necessary to make sure that roughness parameter R of inspected surface does not exceed the value given in engineering documents".
In a case when an error estimation imported by use imprintка, particular for general cases in 20 % as the estimation осверхуп, is unacceptable, it is necessary to define it for a concrete case in view of a material of a measured surface, a method of handling, a range of measured parameter.
3. Estimation of reproducibility of roughness parameters
at manufacture of imprint from polymeric
composites such as "Kompar-P".
For estimation of reproducibility of roughness parameters at use of imprint for a concrete case it is necessary to make a sample of a surface available for monitoring by an article. Thus the sample should be carried out from the same material as a measured detail (article), the surface is treated on the same technique and should have roughness parameters applicable to requirements of the engineering specifications of a measured detail (article). Then from a manufactured sample of a surface to make imprints under the method of application explained below.
3.1. Applied machinery and instruments:
a unit with limits of measuring of parameters of a grain, the given in a delineation on a measured surface;
- glass laminas a size (70?5) х (70?5) mm in accordance with GOST 111;
- a stop watch under technical specifications 25.1894-90;
- glass spreading rods plastic under technical specifications 64-2-150-82;
- two sided adhesive laminat MP 1060.00.00
- Ethanol in accordance with GOST 5962;
Framework from a board with width (1,5?0,5) mm in accordance with GOST 7933. Size of an exterior contour 30x22 mm, 20x12 mm on interior.
3.2. The method of estimation of reproducibility
3.2.1. From laminate to excise a rectangular plate a size 30x22 mm, and in it to excise a strip 20x2 mm on a fulcrum of a plate (see fig. 1).
Fig.1. A plate from laminate with the carved strip.
Beforehand having deleted on the one hand the defensive polymeric film, an obtained plate to paste on a surface of a detail, thus, having confined a band of measuring.
Further according to the use specification of a unit to measure the given roughness parameter R (Ra, Rz, Rmax) of surface of a detail in a band of measuring. To repeate the measurement 10 times, uniformly locating leases of measuring in a band of measuring.
To compute average arithmetical parameter value R, in a micron, of a surface of a detail, which one accept for real parameter value R of a detail:
Where Ri - magnitude of parameter R of a surface of a detail at that measuring, a micron;
n=10 - an amount of measurings.
3.2.2. From a surface of the plate pasted on a surface of a detail to remove the stayed defensive polymeric film, and on the formed sticking stratum to paste a cardboard framework. Then on a surface, restricted by a framework to plot casted a mass got according to Guide on its applying, from above densely to cover a glass lamina. In 20 mines to remove a glass lamina and to take out obtained imprint.
To make 3 imprints in band of measuring. If it is necessary to delete a framework and a plate, to wipe a surface of a detail by ethanol, then to paste new and to go on peeling imprints. Final imprints to sustain under normal climatic requirements in accordance with GOST 15150 during 24 hours.
According to the use specification of a unit to measure roughness parameter R of the surface of imprints. To repeat measurement 10 times, uniformly arranging leases of measuring in band of measuring.
3.2.3. To compute an average arithmetical parameter of rougness Rсл, in a micron, for each imprint, which one accepts for magnitude of roughness parameter R of an imprint.
Where Riсл - magnitude of parameter R of a surface of an imprint at that measuring, in micron;
n=10 - an amount of measurements on each imprint.
Then under the formula:
To calculate the relative error imported by manufacture of imprint  R, in %, for the given concrete surface.
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