We study the process of nonmonotonic loading of the deformable filler in a cylindrical shell with regard for the Coulomb friction. A numerical-analytic description of the loop of structural damping is obtained by using applied models.In the contemporary industry, a significant role is played by vibrational processes. The operation of all machines and mechanisms without exception is directly connected with the appearance of vibrations. In most cases, vibrations decrease the strength, reliability, and durability of industrial machines, mechanisms, and structures and exert harmful influence on the health of the personnel. Thus, the problem of vibroinsulation proves to be quite urgent both from the viewpoint of engineering and for the labor protection.One of the ways used for the solution of the formulated problem is connected with the application of vibroprotecting devices, such as shock absorbers, dampers, dynamic vibration absorbers, etc. This is why the research and design works and theoretical investigations in the field of development of new means of vibroprotection and methods for their numerical analyses are of crucial importance.Note that new promising vibroinsulators were designed at the Pidstryhach Institute for Applied Problems in Mechanics and Mathematics on the basis of a new type of vibration-protecting devices based on the so-called shell elastic elements [6]. As the main distinctive feature of structures of this type, we can mention the application of thin-wall elements (shells, plates, and bars) as the principal bearing and actuating elements. From the viewpoint of design, these are deformable shell systems with dry friction. A comprehensive survey of works devoted to the investigation of dynamic systems with various laws of friction can be found in [9]. In the mechano-mathematical modeling of the behavior of elastic elements under (generally speaking, nonmonotonic) loading, we get a class of nonlinear nonconservative mixed contact problems of the frictional interaction of thin shells with deformable fillers. The general approaches to the formulation and solution of these problems developed for simplified one-dimensional models are described in [2]. The statements, methods, and solutions of some problems from this class and the results of experimental investigations can be found in [1,3,5,7,8]. Engineering methods for the numerical analysis of shell vibroinsulators were developed on the basis of the asymptotic analysis of the obtained solutions in [6].In the present work, we develop methods for the investigation of the stress-strain state, compliance, and damping ability of "cylindrical shell-deformable filler" systems used to model the main elastic element of vibration-protecting devices.Consider an elastic deformable cylinder (filler) of radius R and length 2a placed into a cylindrical shell with thickness h 0 (Fig. 1). The filler is compressed on the end faces by perfectly rigid pistons subjected to the action of an external load Q nonmonotonic as a function of time.

Drilling volumes should be increased in order to increase hydrocarbon production, but this is impossible without the usage of high-quality drilling tools made of modern structural materials. The study has to analyze the design, technological and operational methods to increase the performance of drilling tools made of various materials and has highlighted prospects of technological method applications. The scientific novelty of the study consists in the development of a new analytical model of PDC drill bit–well interaction. The developed model takes into account the drill bit manufacturing errors in the form of bit body–nipple axes misalignment on the drill bit strength. This result makes it possible to determine the permissible manufacturing errors to provide safe operation of the drill bit. It is established that there is an additional transverse force that presses the drill bit to the well wall in the rock due to manufacturing errors. It is determined that the magnitude of this clamping force can be significant. The material effect has been analyzed on additional clamping force. It is established that geometric imperfection of the drill bit causes the minimal effect for the elastic system of the pipe string, which includes a calibrator and is composed of drill pipes based on composite carbon fiber material, and the maximal effect—for steel drill pipes. Polycrystalline diamond compact (PDC) drill bit and well wall contact interaction during operation in non-standard mode is considered. Non-standard stresses are determined, and the strength of the blades is estimated for different values of drilling bit manufacturing error.

The paper proposes a new technology for fluid production intensification, in particular hydrocarbons, which is implemented via significant increasing of the local wellbore diameter in the interval, where the productive stratum is present. The proposed technology improves the well productivity by increasing the filtration surface area and opening new channels for filtering fluids into the well. The innovative, technical idea is to drill large diameter circular recesses in planes perpendicular to the well axis. After that, the rock mass located between the circular recesses are destroyed by applying static or dynamic axial loads. The required value of the axial force is provided by the weight of the standard drilling tool. As a result of the study, the analytical relations to specify the admissible radius of circular recesses and admissible thickness of rock mass between two adjacent circular recesses from the condition of safe operation are obtained. The numerical analysis carried out for typical reservoir rocks substantiated the possibility of well diameter local reaming twenty times. A special tool for circular recess drilling is developed and the principle of its operation is described. The advantage of the proposed approaches is the low energy consumption for well diameter reaming. Our technology will have special economic expediency for the intensification of production from hydrodynamically imperfect wells and under the condition of fluid filtration according to the expressed nonlinear law.

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The article has grounded the necessity to develop an empirical power dependence of cutting modes influence on part surface roughness obtained during thread grinding. The calculations were carried out for grinding of parts made of steel and hard alloy. There have been developed a relation of part material properties, grinding wheel options, lubricating and cooling liquid (constant for concrete conditions of thread grinding), depth of cutting (thickness of a grinded layer per path), revolutions of a part and a wheel, longitudinal feed refer to obtained roughness. It has been stated that components of the grinding mode contribute in roughness values in different way, in particular they are arranged in the ascending order as follows: grinding depth, rotation speed, and detail’s diameter.