The paper is devoted to studying the motion dynamics of stem and ear, as well as particular wheat grains. The purpose of this consideration is to establish parameters of the effect on the plant as a whole, and in particular on the ear, for the efficient extraction of grains from the ear. For this, a mathematical model of the interaction between the elements of the stem-ear-grain system and the conditions for the separation of grain from the ear is built. In a first approximation, a simple stem model consisting of absolutely rigid bodies interconnected by elastic bonds is taken as such a model. Stems with a given moment of inertia act as such bodies, and spiral springs act as elastic bonds.

This article examines the static and dynamic deformation of the stem of an ear of wheat and of the individual grain. The purpose of the article is to determine the factors of influence on the ear of wheat to isolate the grain. Two stages of grain ripening are considered: in the early stage, the grain is attached to the spike by the stem; in the second, there is no stem, and the grain is attached to the ear by the scales. The ear fluctuations are considered within the Euler–Bernoulli bar theory. The developed model divides the study of the dynamics of the stem of an ear and the dynamics of the grain into two stages. The first stage studies the dynamics of the plant as a whole, while the second stage studies the dynamics of an individual grain in a moving system associated with the ear in bending and vertical fluctuation forms. The model of the ear and the grain fluctuation uses the mechanical characteristics of elastic bonds and elastic bodies, which are determined by spring stiffness, elastic moduli, etc. The results show that in the vertical forms of grain fluctuation, the frequency of fluctuation is much higher than in the bending ones. This article presents the natural fluctuation frequencies of grain at full ripeness and in the early phases of maturation, at which point it is released from the ear.

Concrete on Portland cement and cement modified with expanding additives were studied. The authors present the results of study of the modified concrete with combined aggregate. Combined aggregate is a composition of natural granite and limestone crushed stone mixed with crushed concrete. Structure and properties of concrete with combined aggregate is insufficiently studied, which limits their use in civil engineering Recycling of building materials allows to expand the raw material base, to solve the problems of resource conservation and environmental protection. The regularities and causes of changes (reduction) indicators of the quality of concrete with combined aggregate. Studying of properties and laws of formation of structure of concrete at the same time is a method of control of their production. The valuation of properties of concrete with combined aggregates will allow to use them along with traditional concrete.

The article analyzes the change in the stress-strain state of ceramic brick samples when tested in compression, depending on the variable parameters - the type of sample and the method of surface preparation. The experiment showed that the friction forces arising in the “sample-plate test press” zone of contact have a significant effect on the deformation conditions of the samples and lead to an uneven distribution of the breaking load over the surface. This in turn leads to an overestimation of the strength characteristics of the lot, and, consequently, to errors in the calculations of the bearing capacity of the structures. A numerical analysis of the stress distribution also showed that for the samples aligned by grinding and with the help of a mortar; the effect of compression caused by friction forces can be traced. Thus, the results of the numerical experiment are in good agreement with the results of the full-scale experiment. To increase the reliability of the test results, it is necessary to reduce the influence of friction forces and provide conditions for the realization of uniaxial compression. In this regard, it is necessary to adjust the standard test method, namely to use the technical felt gaskets as a method of preparing the surface.