The questions of design maintenance of a given fatigue longevity of rods of complex form during the intensification of load modes without changing of geometric, inertial and rigidity parameters of roads are considered. The study is conducted on the example of needles of circular machines with a small diameter of cylinder (automatic half-hose machines). An approach, based on the system of calculation of loads, loadings and resources under the criterion of fatigue strength, is proposed. The key link for the transition from the results of dynamic analysis to the determination of reliability indices is the dependence of limited longevity of needles on the cycles of load to fatigue failure with the use of statistical data on operating time to fatigue failure of the needles in production conditions. Since the random values of loads of the needles do not obey the normal law of distribution, the general description of density of distribution of amplitude of loads is presented. The influence of increase in speed parameters and constructive measures, aimed to reduce the corresponding loads at a current size of critical section of the needles, on the fatigue longevity is analyzed.
The purpose of the work was analytical research and computer modeling of the influence of shape and size of console beams of elastic plates in non-base configurations for the cam of the automatic half-hose machine under the conditions of flexibility, strength, and minimization of sizes. The scientific novelty of the work lies in the further development of the theory and methodology of designing the elements of knitting systems of the automatic half-hose machines based on regimes of loading, limitations in strength and dimensions, as well as requirements of the technological process. In order to increase the flexibility of the elastic plate, the symmetrical introduction of two console beams of trapezoidal shape was proposed. The influence exerted by the coefficient of the shape of console beams and their lengths on the magnitudes of deflections and stresses was analyzed, which allows making grounded and flexible decisions regarding the dimensions of the root and the end sections of the beams at the preliminary stage of design. The mathematical support was presented mainly in an explicit form, which simplified the analysis of the influence of controlled dimensions of the elastic plates on their flexibility and strength, as well as contributes to the comprehensive approach to the development of cams of different constructions with elastic plates and allows improving the quality and efficiency of design solutions of cams. The beam bending theory and the finite element method based on Code_Aster shared software were used. The model of the plate was represented by an ordered grid of finite nodal elements of the same size, without the use of elongated and flat elements. According to the results of simulation experiments, the distributions of deformations and stresses on the surface of the elastic plate of the cam were obtained, depending on its shape and size, which confirmed the validity of calculated recommendations.
Purpose: development of a methodology for operational assessment of the influence of innovative solutions to the technical and operational characteristics of individual mechanisms and systems on the reliability of the sock automatic machine on a posteriori information about failures in production.Methodology: the method of search, description, analogies and analysis of information is used to audit the set of possible solutions to the subject of research, the basics of reliability theory, methods for assessing reliability indicators based on experimental data, matrix theory, elements of numerical methods and methodology of a posteriori reliability analysis of structurally complex technical systems. Findings: the calculation algorithm and mathematical support for operational assessment of influence of technical and operational changes of one of mechanisms on reliability of the sock automatic machine as a whole in the conditions of uncertainty of the information about failures and sources of its receipt are presented. The advantages of the proposed approach in comparison with the traditional one are shown, which allows to reduce the design duration while ensuring the required quality and minimizing costs by limiting tests and calculations. A numerical estimate of the degree of influence on the reliability of the sock automatic machine of changes in the design of the knitting mechanism is obtained. It is shown that the increase in the average failure time to 24.82 hours, when changing the technical characteristics of the knitting mechanism leads to an increase in this indicator for the machine as a whole to 1.24 hours. Originality: it is the further development of the theory and methodology of reliability analysis of sock automatic machines at the stages of design or modernization in cases of controlled variety of options for innovative mechanisms with limited information about failures and while maintaining functional and structural relationships. Practical value: the method of modeling the reliability of the sock automatic machine according to the innovative solutions of its mechanisms is proposed, which minimizes the costs of additional tests and calculations. The results of the above concept of the analysis of the reliability of the machine confirmed the sufficient accuracy of the calculations at the stage before the design preparation, which allows it to be used for other knitting machines.
Актуальність теми досліджень. Використання зварювання в електричному полі високої напруги для виготовлення прецизійних приладів, наприклад, лазерних гіроскопів, що працюють у важких умовах (вібрації, удари, перепади температур тощо). Постановки проблеми. Сучасні знання про особливості утворення зварного з’єднання при використанні зварювання в електричному полі високої напруги не дозволяють повноцінно оптимізувати процес зварювання й отримувати зварні з’єднання необхідної якості. Аналіз останніх досліджень і публікацій. Отримання якісних зварних з’єднань зварюванням в електричному полі високої напруги пов’язано з величиною мікрошорсткості поверхні діелектрика, якістю її очищення, активізацією процесів поляризації діелектрика, електростатичною взаємодією та утворенням перехідного шару зі складних оксидів між матеріалами, що з’єднуються. Виділення недосліджених частин загальної проблеми. Отримання перехідного шару зі складних оксидів, посилення електростатичної взаємодії між матеріалами, що з’єднуються, підвищує міцність зварних з’єднань, однак експериментальних і теоретичних даних для керування цими процесом ще недостатньо. Постановка завдання. Дослідження факторів, що дозволять оптимізувати процеси утворення перехідного шару зі складних оксидів та електростатичної взаємодії між матеріалами, що з’єднуються. Викладення основного матеріалу. Досліджено вплив хімічного очищення діелектрика перед зварюванням на процеси утворення перехідного шару зі складних оксидів та електростатичної взаємодії між матеріалами, що з’єднуються. Висновки відповідно до статті. Встановлено, що хімічне комбіноване очищення діелектрика перед зварюванням дає змогу створити на діелектрику приповерхневий шар із кислотними властивостями і високоомну плівку, які посилюють окислювально-відновлювальну реакцію та електростатичну взаємодію між матеріалами, що з’єднуються.
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