Timmo Gavrilov

Введение фокусирует внимание читателя на проблеме первичной обработки сортиментов, предназначенных для реставрации памятников деревянной архитектуры (реставрационных сортиментов). Целью исследования является обоснование технологии первичной обработки реставрационных сортиментов и системы машин для её осуществления. Задачами исследования являются: анализ отличительных особенностей первичной обработки реставрационных сортиментов, учитывающих принципы идентичности материала исторических деревянных построек и технологии его обработки; разработка модели технологии первичной обработки реставрационных сортиментов; выполнение декомпозиции компонентов модели; построение блок-схемы технологии первичной обработки реставрационных сортиментов. Материалы и методы исследования. Объектом исследования является технология первичной обработки реставрационных сортиментов. Использованы аналитический обзор литературы в данной предметной области и методы математического моделирования на основе элементов теории множеств. Результаты. Приведён обзор существующих технологий первичной обработки сортиментов – окорки, сушки и антисептирования. Проанализированы требования, предъявляемые к лесоматериалам, применяемым при реставрации памятников деревянной архитектуры. Определены отличительные особенности их первичной обработки. Анализ существующих исследований показал, что в настоящее время отсутствует научно обоснованная технология первичной обработки реставрационных сортиментов, учитывающая их отличительные особенности. Лесозаготовительные организации для первичной обработки применяют технологии и системы машин для «обычных» сортиментов, что ведёт к большой трудоёмкости, высокой стоимости, низкой технико-экономической эффективности и вынужденному снижению качества реставрационных сортиментов. Обоснованы технологические операции первичной обработки реставрационных сортиментов и система машин для их осуществления. Выводы. Предложена технология первичной обработки реставрационных сортиментов, включающая: окорку сортиментов бензопилой с насадками в виде фрез на нижнем складе лесозаготовительных предприятий в период с марта по май; трелёвку сортиментов с нижнего склада лесозаготовительных предприятий на склады-навесы, а также загрузку, поворот и извлечение сортиментов на складах-навесах мини-трактором (мини-трелёвщиком) с прицепом и захватом; сушку сортиментов в штабелях на складах-навесах карусельного типа с предварительной обработкой сортиментов раствором хлорида натрия в период с мая по август; антисептирование сортиментов посредством нанесения кистью на их наружную поверхность пропиточного состава на основе смолы хвойных деревьев и модификаторов в период с августа по сентябрь. Результаты исследования вносят вклад в развитие научной основы для развития технологий первичной обработки реставрационных сортиментов. The introduction focuses the reader's attention on the issue of the primary processing of timber assortments intended for the restoration of wooden architectural monuments (restoration assortments). The aim of the study is to substantiate the technology for the primary processing of restoration assortments and the machine system for its implementation. The objectives of the study are as follows: analysis of the distinctive features of the restoration assortment primary processing that take into account the principles of the identity of the material of historical wooden buildings and the technology for its processing; development of the technology for the primary processing of...

Historic buildings wooden structures are subject to bio-deterioration during operation. The main cause of bio-deterioration is the activity of wood-destroying fungi and insects. In the process of bio-deterioration, voids and inhomogeneities are formed in wood, which reduce the load-bearing capacity of historical buildings wooden structures, which is an urgent problem. The aim of the study is to analyze the changes in the load-bearing capacity of the elements of historical buildings wooden structures depending on biodeterioration. To achieve the goal, the author used methods of physical and numerical modeling of material behavior in wooden structures with artificial bio-deterioration in the form of holes. The paper contains the results of testing of specimens and their finite element analysis. It is revealed that bio-deterioration of wooden structures elements in the form of voids and inhomogeneities reduces their load-bearing capacity. Thus, the load-bearing capacity of specimens with 8 holes decreased relative to specimens without holes by 38.69 %. The degree of degradation of load-bearing capacity depends on the size and localization of biodeterioration. With the increase of bio-deterioration of elements of wooden structures, their load-bearing capacity decreases nonlinearly, which is reflected in the proposed model.

This article considers the effect of constant and variable Poisson’s ratio on cracking in concrete and rock specimens under uniaxial compression using mechanical systems modeling methods. The article presents an analysis of the data confirming the increase in Poisson’s ratio under specimen loading. A system of equations for modeling the effect of Poisson’s ratio on cracking under uniaxial compression is proposed. The comparison showed that the model with a constant Poisson’s ratio predicts a thickness of the surface layer with cracks that is underestimated by approximately 10%. In practice, this means that the model with a constant Poisson’s ratio underestimates the risk of failure. A technique for analyzing random deviations of Poisson’s ratio from the variable mathematical expectation is proposed. The comparison showed that the model with a variable Poisson’s ratio leads to results that are more cautious, i.e., it does not potentially overestimate the safety factor. The model predicts an increase in uniaxial compression strength when using external reinforcement. An equation is proposed for determining the required wall thickness of a conditional reinforcement shell depending on the axial compressive stress. The study contributes to understanding the potential vulnerability of load-bearing structures and makes a certain contribution to increasing their reliability.

The practical realization of sustainable development concepts implies the application of new material processing technologies, among which wood as a renewable resource with a low carbon footprint occupies a special place. Researchers have developed many promising technologies for wood processing, but this paper discusses only one of them that fully meets the requirements of sustainable development. This is a fingerjointing technology for wood. The paper deals with compression tests of pine specimens with initial dimensions of 40×40×80 mm with and without finger joints. Experiments have shown that the finger joint reduces the peak load on the specimen by 11 %. The peak load is reduced caused stress concentration, which is consistent with numerical modelling results in existing studies. In addition, the finger-jointed specimen showed a disproportionate 22 % reduction in relative strain at the peak point. These changes mean a decrease in plastic properties and an increase in brittleness under the influence of the physical and mechanical properties of the adhesive in the gear joint. This paper proposes two versions of the equation for modelling the behavior of wood in load-displacement and stress-strain coordinates. The relevance and feasibility of such research is because finger joint technology minimizes wood waste and ensures sustainable wood management to sustainable development.

Compression tests of pine specimens of two types with initial dimensions of 40x40x80 mm and 40x40x80 mm with finger-joints are considered. Tests on similar specimens without finger-joints are also analyses for comparison. The experiments showed that the finger-joint in the investigated specimens reduced the peak load on the specimen as well as the load in the post-peak stage of plastic deformation. A methodology for modelling the load-displacement relationship taking into account the plastic deformation of wood with a finger-joint in the post-peak stage is proposed. The modelling results do not contradict the experimental data. The basic equation of the proposed mathematical model can be used in further studies to analyse the energy characteristics of the deformation process of wooden elements of building structures.

An experimental study and modeling of the behavior of wood during compression along the fibers was carried out. The nonlinear analytical dependence of the load on the strain was considered. Attention was focused on the post-peak stage of deformation in order to determine the load and displacement at which the transition to the stage of plastic deformation occurs. The work was aimed at substantiating the application of the energy criterion of brittle fracture as a criterion for the transition to the stage of plastic deformation. To achieve this goal, methods of mathematical modeling and analysis of test results were used. As an upshot, a simple and practical procedure was developed to predict the transition point to the above stage of plastic deformation. The simulation results were consistent with laboratory tests of samples and fragments of structures. The practical significance of this criterion lies in its possible use as an additional tool for analyzing the condition of some wooden structures. Energy criteria, including the one mentioned above, belong to fairly universal criteria. Accordingly, the research methodology can be adapted to analyze the behavior of, for example, composites under other types of loads in further studies.

The problems of the mechanical state of rocks and other brittle materials are studied from different sides in a large number of publications, the flow of which does not weaken with time, which is explained by the relevance and complexity of these problems. Quantitative values of strength and other characteristics of such materials can be obtained experimentally or using numerical and analytical models. This work is aimed at developing an analytical model for analyzing the state of brittle material on the example of sandstone under axial compression and axisymmetric proportional lateral pressure. The research uses methods of modeling mechanical systems based on the basic ideas of fracture mechanics. For axial compression with proportional lateral pressure, the equation of the load–strain curve is obtained, and the functions of residual life and damage are justified; effective stresses and effective modulus of elasticity are determined; a calculation algorithm and examples of its application are given. The results of the simulation are consistent with the experimental data known from the literature. The results obtained to a certain extent clarify the understanding of the mechanism of rock damage and destruction under axial compression with lateral pressure.

The efficiency of the process of grinding meat and bone feed depends on a number of design and technological parameters of the grinder operation. One of the most significant issues and at the same time the least studied one is the influence of the number of cycles of loading meat and bone feed with the working bodies of grinders on the particle size of the finished meat and bone feed. To study this issue, the authors proposed a method for modeling the process of grinding meat and bone feed using a stochastic B-model of cumulative damage, which is based on an understanding of the process under study at the macroscopic level and experimental data. The constructed B-model made it possible to determine the optimal number of cycles of loading meat and bone feed with the working bodies of the grinders, at which the required particle size of the finished meat and bone feed is 3...5 mm, and there is no unnecessary energy consumption of the grinding process. This number is equal to 12...18 cycles. The results obtained by the B-model are in good agreement with the experimental data. The constructed B-model of the grinding process of meat and bone feed will further help optimizing the operation of the cutting device and reducing energy consumption for the operation of the grinders as a whole.