Підвищення зносостійкості і мастильної здатності циліндричних напрямних ковзання комбінованою обробкою
Вантажиться...
Дата
2024
Автори
Назва журналу
Номер ISSN
Назва тому
Видавець
Хмельницький національний університет
Анотація
У результаті виконання дисертаційної роботи було розв’язано актуальну науково-прикладну задачу підвищення зносостійкості і мастильної здатності циліндричних напрямних ковзання шляхом створення ефективного маслоутримувального профілю і зміцнення робочих поверхонь плазмовим напиленням. Метою роботи було створення аналітичних та комп'ютерних моделей зносостійкості і мастильної здатності пар тертя циліндричних напрямних ковзання та вибір і обґрунтування технологічних способів підвищення їх довговічності. Для напрямних ковзання запропонований профіль маслоутримувальних канавок із змінною глибиною від максимальної в центрі несучої поверхні до нуля на границі поверхні тертя. Наведений розрахунок зносоконтактних параметрів та моделювання зносу напрямних ковзання з маслоутримувальними
канавками змінної глибини круглого і трикутного профілю. На основі прийнятих припущень у загальному вигляді представлено рішення для визначення кута контакту у циліндричній напрямній ковзання з перекосом осей циліндрів у вигляді трансцендентного рівняння. На основі побудованої скінчено-елементної моделі спряження «клапан-напрямна» проведений аналіз впливу визначальних трибологічних факторів: швидкості ковзання в контакті, температури, кута перекосу, коефіцієнт тертя на контактні напруження як для кожної деталі пари тертя, так і в процесі контактної взаємодії.
Запропонований спеціальний інструмент і технологія отримання маслоутримувального профілю на внутрішній поверхні напрямної клапана.
Результати випробувань на знос напрямних втулок із спіральними маслоутримувальними канавками підтвердили їх ефективність за критерієм зносостійкості. За допомогою Solid-моделі проаналізований вплив зміни геометрії з мастильними канавками отвору напрямної на показники максимальних і середніх напружень в контакті «напрямна-клапан». Визначено скільки циклів здатна витримати контактна поверхня напрямної у кожному з режимів. Показана ефективність використання покриттів з самофлюсуючих порошків на основі
нікелю для підвищення зносостійкості важко навантажених деталей. Мікроструктурний аналіз дозволив визначити структуру та фазовий склад напиленого порошку та запропонувати шляхи підвищення його твердості та зносостійкості.
As a result of the dissertation work, the current scientific and applied problem of As a result of the dissertation work, the current scientific and applied problem of increasing the wear resistance and lubricity of cylindrical sliding guides was solved by creating an effective oil-retaining profile and strengthening the working surfaces by plasma spraying. The purpose of the work was to create analytical and computer models of the wear resistance and lubricity of friction pairs of cylindrical sliding guides and to select and justify technological methods for increasing their durability. Analysis of modern research has shown that technological methods of surface engineering are becoming an alternative to constructive changes made to increase the efficiency of cylindrical sliding guides of technological and transport machines, including for valve mechanism parts. For sliding guides, a profile of oil-retaining grooves with a variable depth from maximum in the center of the bearing surface to zero at the boundary of the friction surface is proposed. It has been established that such a profile has optimal oilretaining capacity and minimal leakage of lubricant. The calculation of wear-contact parameters and modeling of wear of sliding guides with oil-retaining grooves of variable depth of a round and triangular profile are presented. It is established that the solution of the problems of skew in the sliding support is based on the assumption that each section in terms of stiffness characteristics is in a state of plane deformation, and the continuity of the transition functions from section to section is ensured by the geometric continuity of the shaft and sleeve along the axis of the cylinders. Based on the assumptions made, the solution is presented in general form for determining the contact angle in the form of a transcendental equation. Based on the constructed finite element model of the "valve-guide" coupling, an analysis of the influence of the determining tribological factors: sliding speed in contact, temperature, skew angle, friction coefficient on contact stresses both for each part of the friction pair and in the process of contact interaction is carried out. A special tool and technology for obtaining an oil-retaining profile on the inner surface of the valve guide is proposed, which increases the oil capacity of the surface, and therefore, improves the lubrication conditions in the friction pair "valveguide". The results of wear tests of guide bushings with spiral oil-retaining grooves confirmed their effectiveness according to the wear resistance criterion. The wear value of bushings with grooves for the entire time range of tests is on average 20 % less than the wear value of bushings without grooves. Using the Solid model, the influence of changing the geometry with lubricating grooves of the guide hole on the indicators of maximum and average stresses in the "guide-valve" contact was analyzed. It was determined how many cycles the contact surface of the guide can withstand in each of the modes. It was obtained that due to the reduction in the value of maximum stresses by 16.7 %, the actual resource of the guide with grooves increased by more than 6 times. The effectiveness of using self-fluxing nickel-based powder coatings to increase the wear resistance of heavily loaded parts is shown. For plasma spraying, based on the planning of a factorial experiment, optimal technological parameters were established according to the microhardness criterion: current strength 244 A, spraying distance 100 mm and powder consumption 0.48 g/s. Microstructural analysis allowed us to determine the structure and phase composition of the sprayed powder and suggest ways to increase its hardness and wear resistance. The positive effect of introducing 5 % ferrosilicon into the main powder during plasma spraying has been proven, which contributes to the formation of pores in the surface layer as lubricating reservoirs to increase the oil capacity of the surface and reduce friction and wear. The practical significance of the results obtained lies in the recommendation for use at motor transport and repair enterprises of the methods proposed in the work for the restoration and increase of the durability of the valve mechanism parts of internal combustion engines.
As a result of the dissertation work, the current scientific and applied problem of As a result of the dissertation work, the current scientific and applied problem of increasing the wear resistance and lubricity of cylindrical sliding guides was solved by creating an effective oil-retaining profile and strengthening the working surfaces by plasma spraying. The purpose of the work was to create analytical and computer models of the wear resistance and lubricity of friction pairs of cylindrical sliding guides and to select and justify technological methods for increasing their durability. Analysis of modern research has shown that technological methods of surface engineering are becoming an alternative to constructive changes made to increase the efficiency of cylindrical sliding guides of technological and transport machines, including for valve mechanism parts. For sliding guides, a profile of oil-retaining grooves with a variable depth from maximum in the center of the bearing surface to zero at the boundary of the friction surface is proposed. It has been established that such a profile has optimal oilretaining capacity and minimal leakage of lubricant. The calculation of wear-contact parameters and modeling of wear of sliding guides with oil-retaining grooves of variable depth of a round and triangular profile are presented. It is established that the solution of the problems of skew in the sliding support is based on the assumption that each section in terms of stiffness characteristics is in a state of plane deformation, and the continuity of the transition functions from section to section is ensured by the geometric continuity of the shaft and sleeve along the axis of the cylinders. Based on the assumptions made, the solution is presented in general form for determining the contact angle in the form of a transcendental equation. Based on the constructed finite element model of the "valve-guide" coupling, an analysis of the influence of the determining tribological factors: sliding speed in contact, temperature, skew angle, friction coefficient on contact stresses both for each part of the friction pair and in the process of contact interaction is carried out. A special tool and technology for obtaining an oil-retaining profile on the inner surface of the valve guide is proposed, which increases the oil capacity of the surface, and therefore, improves the lubrication conditions in the friction pair "valveguide". The results of wear tests of guide bushings with spiral oil-retaining grooves confirmed their effectiveness according to the wear resistance criterion. The wear value of bushings with grooves for the entire time range of tests is on average 20 % less than the wear value of bushings without grooves. Using the Solid model, the influence of changing the geometry with lubricating grooves of the guide hole on the indicators of maximum and average stresses in the "guide-valve" contact was analyzed. It was determined how many cycles the contact surface of the guide can withstand in each of the modes. It was obtained that due to the reduction in the value of maximum stresses by 16.7 %, the actual resource of the guide with grooves increased by more than 6 times. The effectiveness of using self-fluxing nickel-based powder coatings to increase the wear resistance of heavily loaded parts is shown. For plasma spraying, based on the planning of a factorial experiment, optimal technological parameters were established according to the microhardness criterion: current strength 244 A, spraying distance 100 mm and powder consumption 0.48 g/s. Microstructural analysis allowed us to determine the structure and phase composition of the sprayed powder and suggest ways to increase its hardness and wear resistance. The positive effect of introducing 5 % ferrosilicon into the main powder during plasma spraying has been proven, which contributes to the formation of pores in the surface layer as lubricating reservoirs to increase the oil capacity of the surface and reduce friction and wear. The practical significance of the results obtained lies in the recommendation for use at motor transport and repair enterprises of the methods proposed in the work for the restoration and increase of the durability of the valve mechanism parts of internal combustion engines.
Опис
Ключові слова
напрямна ковзання, маслоутримувальний профіль, зносоконтактна задача, перекос осей, коефіцієнт тертя, комп`ютерне моделювання, контактні напруження, клапанний механізм, плазмове напилення, мікротвердість, покриття, знос, мікроструктура, sliding guide, oil retaining profile, wear-contact problem, axis misalignment, friction coefficient, computer modeling, contact stresses, valve mechanism, plasma spraying, coating, microhardness, wear, microstructure
Бібліографічний опис
Вичавка А. А. Підвищення зносостійкості і мастильної здатності циліндричних напрямних ковзання комбінованою обробкою : дис. ... канд. техн. наук : 05.02.04. Хмельницький, 2024. 230с.