Improving the quality of products created by additive technologies on the basis of tig welding

В роботі розглядаються питання отримання мінімальної хвилястості поверхонь, що формуються аддитивним процесом аргонно-дугового зварювання. Відомо, що геометричні параметри валика розплаву, що пошарово формує відтво-рювану заготовку, визначаються як енергетичними, так і кінематичними характеристиками процесу. При цьому викладання валиків відбувається з оптимальним перекриттям, завдяки чому вдається досягти максимальної щільності моделі, однак з одночасним виникненням певної хвилястості, обумовленої термодинамічними явищами у ванні розплаву. Запропонована модель формування валику наплаву, завдяки якій встановлено раціональні умови викладання шарів. Наведено експериментальні дослідження процесу аргонно-дугового відтворення моделей заданої форми, отримано регресійні рівняння для визначення контрольованого параметру хвилястості. Показано, що на параметр хвилястості випливають динамічні явища та хвильові процеси, які розвиваються під дією системи сил під час формування валику наплаву. Покращення якості виробів вбачається в оптимізації способів формування валиків, забезпеченням динамічної сталості руху робочої головки, забезпеченням відповідного перекриття траєкторій руху по шарам викладання на величину 0,5 е, забезпеченням динамічної сталості руху робочої головки, встановленням раціональної довжини дуги, а також підтриманням режиму динамічної сталості горіння дуги Побудовано поверхні відгуків цільових функцій в площинах параметрів впливу, які дозволяються наглядно проілюструвати залежність контрольованих геометричних параметрів шва від окремих параметрів впливу.The paper deals with the issues of obtaining the minimum waviness of surfaces formed by additive processes of TIG welding. It is known that the geometric parameters of the melt bead, which form a reproducible workpiece layer by layer, are determined by both the energy and kinematic characteristics of the process. In this case, the laying of the rollers occurs with optimal overlap, as a result of which it is possible to achieve the maximum density of the model, however, with the simultaneous appearance of a certain waviness due to thermodynamic phenomena in the melt bath. The proposed model of the formation of a bead of melt, the use of which made it possible to establish the rational conditions for laying out the layers. Experimental studies of the process of argon-arc surfacing of models of a given, regression equations for determining the controlled waviness parameter are obtained. It is shown that the waviness parameter is influenced by dynamic phenomena and wave processes that develop under the action of a system of forces during the formation of a melt bead. An improvement in the quality of products is seen in the optimization of the methods of forming the rollers, in ensuring the dynamic stability of the movement of the working head, ensuring the appropriate overlap of the trajectories of movement along the layers of the layout by an amount of 0.5e, establishing a rational arc length, and maintaining the dynamic stability of the arc burning. The response surfaces of the objective functions in the planes of the process parameters are constructed, which provide a clear illus-tration of the dependence of the controlled geometric parameters on the welding modes.В работе рассматриваются вопросы получения минимальной волнистости поверхностей, формируемой аддитивными процессами аргонно-дуговой сварки. Известно, что геометрические параметры валика расплава, которыми послойно формируется воспроизводимая заготовка, определяются как энергетическими, так и кинематическими характеристиками процесса. При этом выкладка валиков происходит с оптимальным перекрытием, в следствие чего удается достичь максимальной плотности модели, однако с одновременным возникновением определенной волнистости, обусловленной термодинамическими явлениями в ванне расплава. Предложенная модель формирования валика расплава, использование которой позволило установить рациональны условия выкладки слоев. Приведены экспериментальные исследования процесса аргонно-дуговой наплавки моделей заданной формы, получены регрессионные уравнения для определения контролируемого параметра волнистости. Показано, что на параметр волнистости влияют динамические явления и волновые процессы, которые развиваются под действием системы сил при формировании валика расплава. Улучшение качества изделий видится в оптимизации способов формирования валиков, в обеспечении динамической устойчивости движения рабочей головки, обеспечением соответствующего перекрытия траекторий движения по слоям выкладки на величину 0,5е, установлением рациональной длины дуги, а также поддержанием режима динамической устойчивости горения дуги. Построено поверхности отклика целевых функций в плоскостях параметров процесса, которые дают наглядную иллюстрацию зависимости контролируемых геометрических параметров от режимов сварки

Construction Of Gas Discharge Fields With Surfaces Of Space Vehicles Using The Chemography Method

The results of conceptual studies of the intensity of vacuum gas evolution of materials used in spacecraft by chemography are presented. This method is based on the fact that the mass of emitted volatile substances actively condensed on the cooled surfaces of the detector plates can be accurately measured at any distance from the surface under study, which makes it possible to predict the intensity of contamination of the optical surfaces of the spacecraft in real operating conditions

About the Possibility of Application of Laser Vacuum Welding for the Integration of Elements of Heat-protective Structures From Powder Materials

The results of studying the process of laser vacuum welding of elements of heat-shielding panels made of heat-resistant dispersion-strengthened powder materials Ni-20Cr-6Al-Ti-Y2O3 of increased strength are presented. Such materials can be used to create ultralight heat-shielding panels, which are systems integrated on the surface of aircraft from typical modules of a cellular structure. Technical solutions of heat-insulating modules are considered, which are a cellular (honeycomb) structure consisting of two plates with a thickness of 0.1 to 0.14 mm, inside which there is a thin honeycomb filler. It is shown that the small thickness of the plates and the complexity of integrating the elements into a single system significantly impair the formation of a strong connection of such elements and do not allow the direct use of the known methods of diffusion welding or vacuum brazing. It has been established that laser welding of elements of heat-shielding structures in vacuum provides satisfactory strength of the structure of the heat-shielding element as a whole. Local heating at certain points prevents deformation of the parts to be joined during the welding process. The use of a pulsed Nd:Yag laser with a power of 400–500 W, operating in the frequency range of 50–200 Hz, allows welding with or without a filler powder. It was found that the use of filler additives practically does not affect the mechanical properties of the welded joint, however, it reduces the melt zone, while increasing the density of the welded joint. Based on the results obtained, it was concluded that it is possible to use laser vacuum welding for the integration of thin elements of heat-shielding modules. It is shown that a satisfactory joint strength is achieved by ensuring high cleanliness of the surfaces of elements before welding, maintaining a high vacuum (less than 10–2 Pa) and rational thermal loading of the surfaces of the elements to be integrated. The use of the proposed process makes it possible to obtain a stronger and denser seam in comparison with the known methods of soldering multicomponent powder dispersion-strengthened material

Estimation of Damage Development and the TIME of Failure of Cutting Inserts Made of Hard Alloys and Superhard Composites by Chemography Methods

The results of theoretical and experimental studies aimed at identifying hidden defects in the structure of hard alloys and superhard composites used in the manufacture of cutting tools in order to control and predict gradual and sudden failures of cutting inserts.Damage control of cutting inserts is carried out by microscopic analysis. Deeper damage to the structure can be detected using the method of chemographic imaging. The proposed method is based on obtaining photographs of the oxidative reactions of materials of ultra-low concentrations occurring on the surface of solids under thermobaric loading.Before the moment of a sharp release of the energy of destruction, chemical processes of ultra-low concentrations are activated. Chemography allows to fix the zones where the incipient microcracks and microdefects are ready to actively develop, which can lead to the onset of macrodamage and failure to work.The chemographic image of the plate obtained as a result of the study is compared with the reference sample, as a result of which it is possible to assess the initial defect state of the material and predict the further period of the plate's operation.The criterion for the existing defects and imperfections in the structure is the change in the blackness index of the chemographic image, the minimum value of which indicates a minimum of structural defects and internal defects in the material under study.The results allow to propose a new method for controlling the surface of cutting plates, which can be easily implemented in any machine shop, which makes its application very promisin

Forming a Defective Surface Layer When Cutting Parts Made From Carbon-carbon and Carbon-polymeric Composites

We report results of theoretical and experimental research aimed at establishing the mechanisms for the formation of a defective layer at the machined surfaces made from carbon composite materials, specifically those from carbon-carbon and carbon-polymeric groups. Possessing a set of unique physical and mechanical properties, the latter are increasingly applied in aviation and space technologies. However, since the properties of a material are predetermined not only by the components applied but also by the processes to obtain products (laying of reinforcing fibers, orientation of threads), conducting mechanical tests of samples-witnesses is a compulsory stage in the operations performed.Based on the generalization of statistical and theoretical-analytical information, we have developed a model of the emergence and propagation of cracks in a quasi-fragile material, particularly the carbon-carbon and carbon-polymeric composites, caused by the action of a cutting wedge. It is shown that the stresses that occur in a surface layer predetermine the intensity of crack growth while a direction of microcracks propagation is due to the applied force load. Therefore, control over the direction of force action, as well as the application of certain technical means, including a hydroabrasive jet, could enable the localization of microcracks in small quantities at the surface of the formed edge.The established regularities in the formation of a defective layer at machining (including the hydroabrasive cutting) have made it possible to identify ways to improve the quality of a sample and to reduce the layer thickness to 0.05 mm. The derived dependences of the destruction zone parameters on the stresses that occur at cutting allowed us to obtain the rational sequence of machining transitions, at which the defective surface layer is the smallest.The results obtained provide a possibility to significantly increase the accuracy of mechanical tests of carbon composite materials, thereby reducing the variance in the measurements of controlled parameters by 30‒40 %.The results have been actually implemented industrailly, and are of interest for the further research aimed at the hybridization of processes, as well as the development of technologies based on a functional-oriented approach