The statement is formulated and the solution of the problem of determining the time of corrosion destruction of an elastic homogeneous plate with a deep bilateral external recess is given. A plate of corrosive material is subjected to bilateral stretching in a corrosive environment in a direction perpendicular to the axis of the recesses. The well-known solution of the problem of the stress state of this plate, obtained by H. Neuber, is used. The following cases are considered: a) the effect of stress, which occurs in the plate when it is stretched, on the corrosion process is negligible; b) the effect of plate voltage on the corrosion process is significant. In both cases, the dependences of the change in the area of the narrowest cross-section of the plate on time are found. The time of complete corrosion wear and the time of corrosion cracking of the plate before its complete wear are also determined.

Analysis of methods for determining the hardness of the winding shows that all existing methods require a lot of labor and time. When measuring the layer-by-layer hardness, the known methods do not allow obtaining continuous values, and in the case of measuring the hardness of packages of complex shape (conical bobbins, cops, spinning cobs, etc.), it requires a calculation using cumbersome formulas. In this case, the main difficulties arise in determining the volume of the layers of the winding, which in the general case have a complex configuration, and due to defects in the winding may have an irregular shape. Obviously, the described technique is rather cumbersome, and a lot of measurements and calculations are required to obtain a graph of the change in the winding hardness along the package radius. The construction of a graph of the change in hardness along the generatrix using a special device is generally problematic, since placement of more than three sources on the device is impossible due to the size of the meters, and the construction of the curve by three points cannot be considered satisfactory. Winding hardness is one of the most important parameters, on which many technological properties of the package depend. Indeed, with an increase in the hardness of the winding, the amount of material in the same volume increases, which makes it possible to replace packages less often, both on the machine that forms them, and at the subsequent transition. As a result, the equipment useful time increases. It was found that the hardness of the winding is closely related to its rigidity, and hence to the stability during transportation. The hardness of the winding affects the permeability of the package when it is treated with solutions. In this case, a huge role is played not only by the average value of the hardness, but also by its distribution over the layers