ARTICLES

Applying of new composite replication materials for precision testing of parameters of defects on surfaces of details.

SUE GosNIIMedpolymer: Matyushin G.A., Belichenko A.S., Matyushin T.G.
OAO "NII IZMERENIY": Kayner G.B. .

This article concentrates on using of new composites for precision monitoring parameters of defects on surfaces of details.

The technique of parameters of quality of a surface with the help composite replica casting materials is known for a long time. There are some kinds of materials, all of them consist of a filling material and reactive connecting, which one is cured as a result of processes of polyfunctional condensation or polymerization. Now polysiloxanes, calibration epoxies and ethers of acrylic and methacrylic acids are used as connecting. Materials on the basis of these ones have a series of deficiencies: polysiloxanes have a large cure time more than 30 minutes, a low exactitude of copying and hardness; calibration epoxies have a large cure time and the considerable adhesion to a surface of a detail. Materials on the basis of methacrylic ester (methyl metacrylate) as connecting and polymethyl methacrylate (PMMA) in powder form as a filling material, such materials emit Taylor Hobson corporations (Great Britain), Flexbar (USA) and others. These replica casting materials well reproduce a microrelief of a surface in range of parameter of roughness Ra from 0,2 up to 4,0 microns, however imprintки from surfaces with Ra less than 0,2 and more 4,0 microns, have a low exactitude that is stipulated by large shrinkage at polymerization of a methyl metacrylate (up to 25 %). Other essential deficiency is, that the methyl metacrylate is inflammable and the toxic fluid having a high dissolving capacity that does not allow to use a material for deriving imprints from a surface of some paint coatings.

SUE GosNIIMedpolymer has elaborated new composite replica casting a material "Kompar", permitting to receive high-precision imprints from surfaces of details from different materials.

The designed composition allows to avoid the majority of the deficiencies, intrinsic to other replica casting materials, and allows to change a structure of the material "Kompar" over a wide range under concrete application depending on nature of a material of a detail, pecularities of its surface, the shape and the construction.

New replica casting material is a mixture of dymethilmethacrylates: nonvolatile, low-toxic fluid that have a low dissolving capacity; a filling material is a mixture of silicon dioxides with particle size 8-40 nm. New material is emitted as two pastes, mixture of which is cured within 20 minutes. It has higher, as contrasted to other materials, resolution capability: it reproduces a microrelief of a surface in range of roughnesses Ra from 0,04 up to 10,00 microns with an aberration no more than 10 %, and it also allows to reproduce local defects in range height/depth from 0,2 microns. Imprint has high hardness (not less than 200 МPа), that allows to measure parameters of its microrelief and defects on a surface by contact methods. Stability of geometrical parameters of imprints allows to store obtained imprints not less than 3 years, using them as model.

The given material may be used for measurement of local defects on surfaces of details, such as cracks. imprints, obtained with the help of new material, ensure measurement of parameters of cracks with width of a deployment from 0,5 microns. Thus for the first time were obtained imprints an internal surface of cracks and the estimation of depth of cracks is realized. Besides applying of new material has ensured measurement of the smallest surface defects (including in hard-to-reach places); quality control of coverage's: a galvanizer, a spraying, oxidation; measurement of parameters of a roughness in accordance with GOST 2789-73 and ISO 4287 including on curvilinear surfaces; measurement of geometrical parameters and roughness of threads. Hardness and stability of geometrical parameters imprintкs allow to apply "Kompar" in monitoring and observation of stages of development of defects or a wear at storage, maintenance, overload tests of essential parts.

To decide a problem of objective monitoring of depth of cracks and to analyze a condition of their internal surface in OAO "NII IZMERENIY" the technique of high-precision measurement of parameters of a relief of imprints obtained with the help of a material "Kompar" is designed. Applying of this technique for the first time has allowed to measure depth of cracks and to estimate a condition of their internal surface.

The material has passed trials in Department of measurement of geometrical magnitudes ВНИИМС, and test data have shown, that the mean error of copying of a surface with parameter Ra=0,025 a micron has compounded 17,5 %, and with parameter Ra=3,2 a micron - 2,8 %. Under totals of trials the certificate of conformity is obtained, and the material recorded in the Register of the System of certification of means of measurements under ?020010163.

According to our reckoning, "Kompar" in a combination to measuring techniques of parameters of a relief of reprints the series of actual problems of a nondestructive check will allow to decide capabilities of a material: detection of defects on vanes of turbines, monitoring of standard samples for a capillary non-destructive testing, measurement of geometrical parameters of threads, such as screw pitch, an angle of inclination of a lateral face of the profile of inside threads, roughnesses of generatrix surfaces, monitoring of a flowing wear of bearing boxs, definition of parameters of quality of handling of curvilinear surfaces and others. Besides according to our opinion this material may find applying as locking in threaded and landing connections.