Absract The article presents the main results of the studies on the factors influencing the quality of paint and varnish coating of the car body while performing the emergency recovery repair. The relevance of scientific observations in the presented work is that the issues connected with the quality assessment of applying and drying of paint and varnish coating of the body are not studied to the full extent. It especially concerns the cars that need recovery repair after road accidents. The data presented in the article can be applied while assessing the technical state of the cars, injured as a result of break-down incidents; when training specialists in the automotive industry; with the color selection of paints and varnishes and further application on the body. The scientific work provides the contribution to the improvement of the efficiency indicators of the cars operation on the basis of defects testing of decorative protective coating of the body and the definition of the factors influencing the quality of paint and varnish coating during repair application. The scientific novelty of the article consists in obtaining the identification results of the most significant factors affecting the quality of the paint and varnish coating applied while repairing, aimed at the restoration of the critical state of the car body resulting from the traffic accident.

Formulas are presented for calculation of residual post-bending stresses that develop in pipe fittings. The formulas are derived as a result of solution of the elasto-plastic problem of the bending of a straight pipe.Residual stresses σ res (axial stresses) that develop in fittings after bending are defined as the sum of the stresses that are manifested in the fittings during bending σ bend and unloading σ unl (see Fig. 1):(1)The stresses that develop in a fitting during bending σ bend are determined from the following formulas: in the region of elastic deformations:(2) in the convex (tension) region when 0 ≤ y < y y ,in the concave (compression) region when -y y < y ≤ 0; and in the region of plastic deformations:in the convex (tension) region when y y ≤ y ≤ r out ,in the concave (compression) region when -r out ≤ y ≤ -y y , where y is the distance from the neutral axis to the layer under consideration in the cross section of the fitting, y y is the distance from the neutral axis to the region of plastic deformations in the cross section of the fitting (the coordinate of the boundary between elastic and plastic deformations)ξ y is the deformation for which the stresses are equal to the yield point at 20°(R e/20 ) (7) ξ y / = R E e 20 20 ; y y max out y r = ξ ξ ; bend / σ = −R e 20 bend / σ = R e 20 σ bend = − y R E 20 σ bend = y R E 20

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Formulas for calculating the optimal yield radius and optimal pressure of autofrettage of curved elements of pipelines obtained as a result of a solution of an elasto-plastic problem are presented. Formulas for calculating the optimal yield radius and optimal pressure of autofrettage of pipes as well as results of calculations using the proposed formulas and a comparison of the results with the actual values of the pressure of autofrettage of pipes are presented.

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