Search Results (12)

Friction dampers based on the effects of dry friction are attractive to engineers because of their simple design, low manufacturing and maintenance costs, and high efficiency under heavy loads. This study proposes a new damper design based on an open shell with a deformable filler, with the shell cut along a cylindrical helical line. The key idea in developing the design was to use the bending effect of the shell in contact with the weakly compressible filler. Another idea was to use the frictional interaction between the filler and the open shell to obtain the required damping characteristics. The working hypothesis of this study was that, ceteris paribus, a change in the configuration of the shell cut would cause a change in the stiffness of the structure. To analyse the performance characteristics of the proposed damper and test the hypothesis put forward, a numerical model of the shell damper was built, and a boundary value problem was formulated and solved for the frictional interaction between the shell cut along the helical line and the weakly compressible filler, taking into account the dry friction forces between them. As a result, the strength, stiffness, and damping properties of the developed damper were investigated, and a comparative analysis of the new design with the prototype was carried out. It is predicted that the proposed friction damper will be used in the energy and construction industries, in particular in drilling shock absorbers for the oil and geothermal industries, as well as in earthquake-resistant structures. Full article

Optimization of drilling processes for oil and gas and geothermal wells requires the effective use of mechanical energy for the destruction of rocks. When constructing a well, an important indicator of the drilling stage is the mechanical speed. Therefore, when performing drilling operations, operators usually use blade bits of an aggressive design and often use forced drilling modes. Drill bits under forced operation modes generate a wide range of vibrations in the drilling tools; in turn, a drill string, being a long-dimensional deformable body, causes the development, amplification, and interconnection of vibrations of different types. Vibration loads reduce the technical and economic indicators of drilling, with destructive effects on drill string elements, and cause complications and emergencies. The authors initiated the creation of an informational and analytical database on emergency situations that occurred as a result of excessive vibrations of the drill string during the construction of deep wells in the deposits of the Dnipro–Donetsk Basin. For the first time, the suitability and effectiveness of using the Smart 4 controller (“Innova Power Solutions”, Calgary, Canada) for monitoring the vibration load of the drilling tool was tested in industrial conditions, while the controller was used as a separate element in the drill string. A special module was developed for the reliable installation of the Smart 4 controller, with a power battery in the layout of the lower part of the drill string. During the testing of the proposed device for measuring vibrations in the process of drilling an inclined well, verification of the registered data was carried out with the help of a high-cost telemetry system. The implementation of the proposed innovation will allow each operator to assess the significance of the impact of vibrations and shocks on the production process and, if necessary, adjust the drilling modes or apply vibration protection devices. In addition, service departments that operate and repair drilling equipment will be able to obtain an evidence base for resolving warranty disputes or claims. Full article

In this article, an analytical approach to the study of the behavior of functionally graded FG coatings under local load is developed. The method is suitable for coatings with a specific structure. We consider that the coating can be conditionally divided into two zones: a relatively rigid outer and a relatively compliant inner. The outer layer is modeled by a non-homogeneous plate that bends. We submit the inner substrate to the hypothesis of a non-homogeneous thin Winkler layer. The solution of the formulated boundary value problem is constructed in analytical form. Simulation examples for FG aluminum oxide coatings grown from aluminum sprayed on steel and from compact alloy D16T are considered. The distributions of equivalent stresses, safety factors and normalized equivalent stresses in the coatings are studied. It is noted that in a heterogeneous material, the location of the minimum of the safety factor does not always coincide with the location of the maximum of the equivalent stress. Full article

Today, pipelines are the safest and most economical way to transport petroleum products and one of the key components of modern energy infrastructure. Nevertheless, pipeline systems are associated with certain risks that can lead to environmental disasters. The idea of carrying out this study was initiated by the results of the survey of the overpasses of the long-used oil pipelines laid in the mountainous area of the Carpathian region. Defects such as a change in the shape of the pipe and local bulges in the area of oil pipeline support nodes were detected. The explanation of the described problem is separate from the typical algorithms of design calculations, which are offered to manufacturers by current directive documents. The desire to provide an explanation and quantitative assessment of the detected defects became the main motivation for writing the article. An analytical model of the interaction of the oil pipeline with the rigid support has been developed. Additional internal loads in the cross-section of the pipe and displacement of its middle surface, which arise as a result of such interaction, are determined. The method of determining the reaction in the intermediate support of the overpass of the oil pipeline has been developed, considering the properties of the soil base in the underground sections and the mounting gap in the support node. The analytical dependence was obtained to determine the additional hoop stresses that arise in the oil pipeline due to the contact of the pipe with the support. The unambiguous relationship between the maximum additional hoop stress and the reaction in the support node was established. The dependence of additional hoop stresses on the geometric characteristics of the pipes was analyzed. The obtained research results are tested on the real structure of the overpass of the Druzhba oil pipeline, built in the Carpathians. In general, a simple engineering technique has been developed that allows analyzing the behavior of the oil pipeline support node and provides the numerical correction to the traditional strength assessment formulas, which determine the equivalent stresses in the oil pipeline. Full article

The prospects of plasma electrolytic oxidation (PEO) technology applied for surface hardening of aluminum alloys are substantiated. The work aims to optimize the technological process of PEO for aluminum in flowing electrolyte. The design of the equipment and the technological process of the PEO for aluminum deformed alloy D16T in flowing silicate–alkaline electrolyte have been developed. Oxide coatings were formed according to various technological parameters of the PEO process. The properties of the oxide coatings were evaluated, respectively, by measurements of coating thickness, geometric dimensions of the samples, microhardness, wear tests, and optical and scanning electron microscopy. To study the influence of the technological parameters of the PEO process of forming oxide coatings on geometrical, physical, and mechanical properties, planning of the experiment was used. According to the results of the conducted experiments, a regression equation of the second order was obtained and the response surfaces were constructed. We determined the optimal values of the technological parameters of the PEO process: component concentration ratio (Na₂SiO₃/KOH), current density, flow rate, and electrolyte temperature, which provide the oxide coating with minimal wear and sufficiently high physical and mechanical properties and indicators of the accuracy of the shape of the parts. The research results showed that the properties of oxide coatings mainly depend on almost all constituent modes of the PEO process. Samples with Al₂O₃ oxide coating were tested during dry friction according to the “ring–ring” scheme. It was established that the temperature in the friction zone of aluminum samples with an oxide coating is lower compared to steel samples without a coating, and this indicates high frictional heat resistance of the oxide coating. Full article

The mechanism of the influence of crystal inhomogeneities on the magnetic and domain microstructures of functional materials based on yttrium iron garnet heterostructures is an important subject of investigation due to the aim to predict parameters for manufacturingpurposes. A study of the structural and magnetic characteristics of a set of yttrium iron garnet films grown on gadolinium–gallium garnet substrate is presented. High-resolution X-ray diffractometry, Mössbauer spectroscopy, MFM, as well as ion implantation simulation and X-ray diffraction simulation were used together to determine the features of the effect of Ne⁺ ion implantation with different dose rates on the samples. The simulation of ion implantation with E = 82 keV showed energy loss profiles of Ne ions with subsequent defect formation up to amorphization of near-surface layers at high doses. Implantation creates two magnetically non-equivalent types of tetrahedrally located Fe³⁺ ions, which leads to a rotation of the total magnetic moment relative to the film surface and a change in the width of the magnetic domain stripes. Full article

The results of a study of the contact interaction of an open shell and a chrome-plated shaft with elastomeric filler installed coaxially are presented. The considered contact system is a model of the original design of the shell damper of dry friction. The design feature is the following: the bearing link of the damper is a thin-walled cylindrical shell with a cut along the generatrix; the working body of the damper is elastomeric filler; a hollow chrome-plated shaft centers the damper elements and allows it to be used in technological processes with the presence of aggressive and abrasive-containing media. The mechanical-mathematical modeling of the behavior of the presented damper under the conditions of operational loads has been carried out. The idea of identifying the properties of a cut isotropic shell, which bends under the conditions of a nonaxisymmetric contact load, and a strongly orthotropic continuous shell is applied. As a result, dependences were obtained to determine the rigidity and the maximum allowable load of the damper. The effect of the coefficient of friction of the contact pairs elastomer-shell and elastomer-shaft on the damper performance properties has been studied. A technique for the quasi-static analysis of structural damping in non-mobile, non-conservative shell systems with deforming filler has been developed. The hysteresis loops of the damper under a nonmonotonic load are constructed, the dependence of the amount of dissipated energy on the cycle asymmetry coefficient is found. An analysis of the results obtained showed that the use of open shells in friction shock absorbers can significantly reduce their rigidity compared to solid shells and thereby reduce the resonant frequencies of the dynamic system. This circumstance makes such vibration isolators particularly attractive for use in superresonance vibrators as working modules of drilling shock absorbers and elastic hangers of sucker rods in oil and gas production. Full article

The issue of choosing the method for optimal surgical treatment of a broken fibula has been debatable for many years. At the same time, concomitant repair of tibiofibular syndesmosis injuries does not have a unified approach. It has been determined that osteosynthesis of broken shin bones with syndesmosis injury should combine stable fixation of the broken bone and should not limit the elastic properties of the syndesmosis. In case of a broken fibula, it is recommended to use a stable extracortical fixator and an elastic connection of the syndesmosis injury using a tightrope. An analytical model of the broken fibula, which is blocked with an extracortical fixator metal plate and elastically fixed with a tightrope, has been developed. The research object is the stress–strain state of the “broken fibula–extracortical titanium plate” composition under the action of tightrope tightening fixation. The main research result is an analytical dependence, which makes it possible to determine the permissible value of the tightrope tightening force for elastic fixation of the tibiofibular syndesmosis. The research results have been tested numerically, and the influence of the parameters of plate, bone and damage localization on the permissible value of the tightrope tightening force has been analyzed. By using the rational tightrope tightening force with stable–elastic fixation of the broken shin, it is possible to reduce the time before the start of loading on the injured extremity and accelerate the functional recovery of the patient. Full article

Today, an interdisciplinary approach to solving the problems of implantology is key to the effective use of intraosseous dental implantations. The functional properties of restoration structures for the dentition depend significantly on the mechanical stresses that occur in the structural elements and bone tissues in response to mastication loads. An orthopedic design with a bar fixation system connected to implants may be considered to restore an edentulous mandible using an overdenture. In this study, the problem of the mechanics of a complete overdenture based on a bar and four implants was formulated. A mathematical model of the interaction between the orthopedic structure and jawbone was developed, and a methodology was established for the analytical study of the stress state of the implants and adjacent bone tissue under the action of a chewing load. The novelty of the proposed model is that it operates with the minimum possible set of input data and provides adequate estimates of the most significant output parameters that are necessary for practical application. The obtained analytical results are illustrated by two examples of calculating the equivalent stresses in implants and the peri-implant tissue for real overdenture designs. To carry out the final assessment of the strength of the implants and bone, the prosthesis was loaded with mastication loads of different localization. In particular, the possibilities of loading the prosthesis in the area of the sixth and seventh teeth were investigated. Recommendations on the configuration of the distal cantilever of the overdenture and the acceptable level and distribution of the mastication load are presented. It was determined that, from a mechanical point of view, the considered orthopedic systems are capable of providing long-term success if they are used in accordance with established restrictions and recommendations. Full article

This paper studied the distribution of stresses near damage in the form of axial surface cracks in a pipeline reinforced with a spiral-wound composite coating. The authors applied the homogenization method to determine the effective elastic characteristics of a structurally anisotropic layered package. By means of the classical momentless theory of shells, it was established that the stress state of the coated intact pipe under the pressure of the pumped product depends on the parameters of the geometry of the capacity strip, as well as on the component composition of the heterogeneous coating. The finite element method was applied to solve the problem of plane deformation of a piecewise homogeneous ring with an internal crack perpendicular to the interface. This problem assumes the linearity of the materials and the ideal mechanical contact with the layers. The effect of the composite coating and the size of the damage on the magnitudes of the energy flow into the crack tip, and on the stress intensity factor, was studied in detail. Various variants of the coating were considered, namely, winding of the coating on an unloaded pipe and reinforcement of the pipe under repair pressure. Full article

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. Full article

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. Full article