For the sake of ensuring the energy security of Ukraine, the trouble-free operation of the oil transportation system becomes of strategic importance. The problem is exacerbated in connection with the long service life of individual objects of the system, which leads to degradation of the properties of the pipe material due to corrosive and erosion processes, which is enhanced by the effect of time-varying loads. Today, in world practice, various methods are used to strengthen defective sections of pipelines: installation of steel, plastic and fiberglass couplings, winding of an elastic composite tape, the use of reinforcing composite couplings, etc. To study the effect of microcracks, corrosion and erosion defects on the Druzhba oil pipeline of OJSC Ukrtransnafta with an installed bandage, full-scale tests of a defective section of a pipe (material - 17GS steel) reinforced with bandages made of a similar material using a UI1 / 200 GK installation were carried out. As a result of research, the pressure of its destruction was determined. During the tests, strain gauging was used to determine pipe deformations. Comparison of the values of stresses obtained experimentally and analytically confirmed that the use of bands on defective sections of the pipeline is an effective means for extending their service life. For a more accurate and detailed analysis of the reliability and durability of oil pipelines, a study of the defective parts (break point) cut from the pipeline was carried out. As a result of the studies carried out on the models - "cutouts", corrosion defects with a depth of up to 5 mm were registered, which is about 55% of the loss of metal, however, the pipe was not destroyed by these defects, but by a defect of the "crack" type. To obtain the profile of the defect from the model - "cutout", scanning was carried out using a sensor fixed on a mobile tripod connected to a computer via an ADC. At the next stage of research, the assessment of the residual resource was carried out using the analysis of full-scale kinetic curves of damage to hazardous sections of the oil pipeline through experimental studies of models - "cutouts". A fatigue curve has been constructed, which can later be used to predict the fatigue life of such elements.
Purpose. Development of a method for simulating the screwing torque/moment and researching the design of double-shoulder threaded joints while preserving their geometric parameters. Determination of the optimal length of the additional shoulder pin part for the developed drill collar (DC) of NC50, NC55 type of various standard sizes. Establishing the dependence between the pin part length of the additional shoulder and other geometric parameters of the double-shoulder joint of the DC for further use when developing other standard sizes of similar design threads. Methodology. The development of design and the method for simulating the screwing torque of double-shoulder threaded joints was carried out using the finite element method and parametric modeling. Finding. A method for simulating the screwing torque of threaded joints was proposed and developed, which made it possible to improve the model of their automated design. The optimal lengths of the pin part of the additional shoulder of the developed design of double-shoulder threads of the NC50, NC55 types were determined. For planning threaded joints of similar design with the above-mentioned types of threads, a dimensionless coefficient was derived and its value was calculated. A nomogram was built to determine the length of the joint additional shoulder pin part due to the value of this coefficient. Originality. The model of automated design for double-shoulder threaded joints of drill string parts has been improved. This model preserves their geometric parameters and enables modeling a wide range of standard sizes of similar joints. Practical value. The optimal geometric parameters of the developed structures of double-shoulder threaded joints of the drill string elements were determined. A nomogram was built to determine the length of the additional shoulder pin part of the joint by the value of the dimensionless coefficient.
The study has been conducted by means of physical, mathematical and computer modeling integrated method use. To prove the adequacy of the results obtained the experimental procedure on the existing equipment and laboratory facilities has been applied. The method of carrying out asymmetric stress cycles with mean stress of stretching to symmetric using the proposed piecewise – linear equations for evaluating the material sensitivity to asymmetry of the cycle has also been improved. It has enabled pipe column element durability under the condition of typical asymmetric low-amplitude loading calculation.
A significant number of computer programs exist today for various engineering calculations, research and development of equipment elements. The SolidWorks software has become widespread for such work, which allows you to minimize time, facilitate the performance of the necessary work, as well as analyze the strength, stiffness, stability and endurance of products of a wide range of complexity and purpose. The program uses the finite element method, which has both a number of advantages and certain disadvantages. To investigate the possibilities of such a program, a model of a threaded connection of sucker rods has been built. Simulation of make-up torque for threaded connections remains problematic when modeling in SolidWorks Simulation. There are several ways to simulate the make-up moment during the study of the stress-strain state of threaded connections. To solve problems in an axisymmetric setting, the optimal method is to overlap the ends of the nipple and coupling by the required amount. The use of an axisymmetric model in the process of simulation does not impair the results obtained in comparison with 3D models. But it speeds up the calculation process, allows you to build a fine mesh of finite elements and get more accurate results. The paper presents an algorithm for calculating the tension of the threaded connections of sucker rods, which can be applied to threaded connections of drill string elements with some adjustments. The only difference will be in the formula for determining the make-up moment, from which the value of the pre-tightening force and the areas of dangerous sections are derived. Also, in the work, a simulation study was carried out using the selected method using the example of a threaded connection of sucker rods with a diameter of 19 mm. A diagram of displacements and distribution of equivalent stresses in a threaded connection was obtained and the possibility of determining specific parameters at certain points of the model under study was shown with subsequent automated construction of their graphical dependencies.
Based on the field data, numerous failures of the downhole equipment of sucker rod pumping units occur, especially of the sucker rod strings. They are subject to corrosion, wear and alternating loads. The stress-strain state of the threaded connection elements is determined by the nature of the distribution of loads along the threads, which is uneven and depends on many factors. Despite this, the development of new designs of sucker rod connections and measures to improve the efficiency of operation and their research is an urgent task. In addition to the threaded connections of the sucker rods, there were a number of threadless designs that were not used in the fields, but they passed certain tests. The article presents these connection designs and discusses their advantages and disadvantages in comparison with standard threaded connections. Simulation modeling of a standard connection of sucker rods made it possible to investigate its stress-strain state and identify hazardous areas (stress concentrators). The stress-strain state of the threaded connection of the sucker rods has been investigated, the design of this connection has been improved and it has been established that, in comparison with the standard threaded connection of the sucker rods, the investigated has certain advantages. It was found that with an increase in the number of protrusions and depressions in a threaded joint, stresses decrease, which are concentrated in dangerous sections and along the contact planes. Convex contact planes also reduce stress, especially at the joint surface. Research has shown that the stresses generated in a threadless sucker rod joint are less than the stresses generated in a standard sucker rod and sleeve joint. Although the difference between these stresses is insignificant, attention should be paid to changing the geometric parameters of the threadless connection of the sucker rods, thereby reducing the maximum stresses.
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