Vibrations in engineering and technology

Matviychuk Viktor – Doctor of Technical Sciences, Full Professor, Head of the Department of Electric Power Engineering, Electrical Engineering and Electromechanics, Vinnitsa National Agrarian University (3 Solnechna St., Vinnitsa, 21008, Ukraine, email: vamatv50@gmail.com)

Kolisnyk Mykola – Assistant Professor, Department of Electric Power Engineering, Electrical Engineering and Electromechanics, Vinnitsa National Agrarian University (3, Solnechna str., Vinnitsa, 21008, Ukraine, email: kolisnik30@gmail.com).

Andrii Shtuts – Assistant Professor, Department of Electric Power Engineering, Electrical Engineering and Electromechanics, Vinnitsa National Agrarian University (3, Solnechna str., Vinnitsa, 21008, Ukraine, email: shtuts1989@gmail.com).

The analysis of construction of curves of limiting deformations of metals is carried out in the work. It is established that traditional test methods, such as deposition and stretching of cylindrical specimens, do not ensure the constancy of the stress state, and therefore contribute to the history of deformation in the construction of curves. During deposition, there is an increase in the stress state due to the curvature of the lateral surface of the sample (barrel formation), which is caused by friction at the ends. And when stretched, the stress index also increases, as a result of the formation of the neck due to the loss of resistance to deformation. Therefore, measures were considered to ensure reliable results in the construction of curves of boundary deformations, excluding the influence of the history of deformation. When settling, such measures include the use of plastic, softer than the sample material, foil at the ends of the samples and the gradual removal of the edges of the hole at their ends by grinding or deposition without foil. In addition, the experimental-calculation method was considered, which involves the construction of ways of deformation and correction of the limit deformation using the criterion of deformability. When stretching, in the case of neck formation, the increase in deformation linearly depends on the ratio of the radius of curvature of the neck to its diameter. The equation by which the experimental-calculation method can take into account the influence of the neck on the increase of ultimate deformations is given. To experimentally determine the ultimate tensile deformation, a method of rolling cylindrical specimens on a wedge with rolls whose radii increase during rolling is proposed, which eliminates the appearance of the neck. Boundary strain curves can be constructed with sufficient accuracy for torsion and deposition test specimens, and tensile strain values are obtained using approximated dependences tested for different metals.

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