Ukrainian Journal of Mechanical Engineering and Materials Science. – 2020. – Vol. 6, No. 2
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Науковий журнал
Засновник і видавець Національний університет «Львівська політехніка». Виходить двічі на рік з 2015 року.
Ukrainian Journal of Mechanical Engineering and Materials Science = Український журнал із машинобудування і матеріалознавства : науковий журнал / Lviv Politechnic National University ; editor-in-chief Oleksiy Lanets . – Lviv : Lviv Politechnic Publishing House, 2020. – Volume 6, number 2. – 62 p.
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Browsing Ukrainian Journal of Mechanical Engineering and Materials Science. – 2020. – Vol. 6, No. 2 by Author "Lviv Polytechnic National University"
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Item Features of repair welding of power hydrocylinder elements(Lviv Politechnic Publishing House, 2020) Dzyubyk, Andrij; Nazar, Ihor; Dzyubyk , Liudmyla; Lviv Polytechnic National UniversityAt present, the use of power hydraulic cylinders is an integral part of most industrial equipment. They provide translational and horizontal movements, replacement of goods, fixation, etc. These devices are necessary elements of the equipment where application of the corresponding level of effort is applied. Often hydraulic cylinders are created specialized to perform certain types of work. It should be noted that part of the elements of the power cylinder in the manufacture is combined with welding. Such integral connections provide rigidity of installation, tightness of a design, fatigue strength at multicycle loadings. Difficult operating conditions, significant workloads, the presence of various external factors often leads to the destruction of individual elements of the cylinder. At the same time, the cost of repairing equipment that involves replacement with new power devices is quite high. This causes the implementation of repair and restoration work carried out at specialized enterprises. However, in the case of repairs, there are often a number of problems that require prompt resolution in the production environment. These should include the provision of basic materials with similar physical and chemical properties, the establishment of welding modes, the selection of the necessary welding materials, the use of appropriate techniques for conducting the arc process, etc. Therefore the repaired welded design of the case of the power hydraulic cylinder needs additional studying for weldability of separate elements among themselves, formation of a zone of thermodeformation influence. In general, the repaired hydraulic cylinder should meet the installation operating requirements depending on the purpose. The design of the considered hydraulic cylinder of the press installation is rather technological from the point of view of maintenance of automation of welding process. It contains long welds of a simple ring configuration. At the same time, the significant linear dimensions and the presence of a cylindrical surface cause some complexity in the implementation of processes. The construction material of the power hydraulic cylinder is low-carbon low-alloy steels. The analysis of technological weldability indicates a tendency to crack due to the thermal cycle of welding. The simulation of welds of the power hydraulic cylinder is performed in the work. The number of rollers was taken into account when obtaining butt welds. A compa ative analysis of different electrode materials with different doping systems is done. The most applicable welding materials by chemical composition and properties of the weld metal are determined. According to the literature data and the results of comparative analysis, the optimal range of cooling rate of the main material of the hydraulic cylinder was established. The properties and structure of the zone of thermal influence of the butt welds of the power hydraulic cylinder have been studied. The magnitude of deformations and stresses caused by the thermal cycle of welding of the hell structure of the hydraulic cylinder liner is investigated. The admissible parameters of the zone of plastic deformations during butt welding are determined.Item Localization of steel fractures based on the fractal model of their metallographic images(Lviv Politechnic Publishing House, 2020) Zhuravel, Ihor; Mychuda, Łesia; Zhuravel, Yurii; Lviv Polytechnic National UniversityThere are a number of tasks that require assessment of the condition of the material and its mechanical characteristics. Such tasks may arise at the production stage, when there’s a need to control the content of various components of the material, strength, hardness, etc. Also similar tasks arise during exploitation of materials, which is especially relevant today, when most of the responsible products and structures in the field of nuclear energy, chemical industry, machine-building industry are on the verge of wearing down. Previously defectoscopy methods were mainly used to assess the reliability of such materials and products. These methods provided information on the presence or absence of a defect. But to prevent accidents, information about the pre-defective state of the material itself and the degree of its degradation is needed. Approaches involving methods and means of solid state physics, mechanics, chemistry, materials science and other scientific disciplines have become more informative for describing the state of degradation. However, these methods are quite laboursome and time consuming and cannot be applied to transient processes. Therefore, it is important to develop a method that would be based on the analysis of the microstructure of the material would allow to obtain its numerical mechanical characteristics. This approach would be used at the production stage of materials to determine their components and mechanical characteristics and at the stage of exploitation to determine the degree of degradation of the material. It is known that the fractal dimension of each microstructure of the material is an indicator of its qualitative characteristics. Thus, the numerical value of the fractal dimension establishes the relationship between the structure and the mechanical properties of the material. In this work the method of localization of fractures of heat resistant steels on the basis of fractal models of metallographic images is developed and its advantages in comparison with other known approaches are analyzed.Item Modellingand simulation of pneumatic system operation of mobile robot(Lviv Politechnic Publishing House, 2020) Korendiy, Vitaliy; Kachur, Oleksandr; Havrylchenko, Oleksandr; Lozynskyy, Vasyl; Lviv Polytechnic National UniversityProblem statement. Mobile robots are currently of significant interest among researchers and designers all over the world. One of the prospective drives of such robots is equipped by a pneumatically operated orthogonal system. The processes of development and improvement of orthogonal walking robots are significantly constrained because of the lack of an open-access comprehensive scientific and theoretical framework for calculating and designing of the energy efficient and environmental-friendly pneumatic walking drives. Purpose. The main purpose of this research consists in the kinematic analysis, motion modelling and pneumatic system simulation of the mobile robot with an orthogonal walking drive. Methodology. The research is carried out using the basic laws and principles of mechanics, pneumatics and automation. The numerical modelling of the robot motion is conducted in MathCad software. The computer simulation of the robot kinematics is performed using SolidWorks software. The operational characteristics of the robot’s pneumatic system are investigated in Festo FluidSim software. Findings (results) and originality (novelty). The improved design of the mobile robot equipped by the orthogonal walking drive and turning mechanism is thoroughly investigated. The motion equations of the orthogonal walking drive are deduced, and the graphical dependencies describing the trajectories (paths) of the robot’s feet and body are constructed. The pneumatically operated system ensuring the robot rectilinear and curvilinear locomotion is substantiated. Practical value. The proposed design of the walking robot can be used while developing industrial (production) prototypes of mobile robotic systems intended for performing various activities in the environments that are not suitable for using electric power. Scopes of further investigations. While carrying out further investigations, it is expedient to design the devices for changing the robot locomotion speed and controlling the lifting height of its feet.Item Simulation modelling of dynamic processes due discontinuous frictional treatment of the flat surfaces(Lviv Politechnic Publishing House, 2020) Gurey, Volodymyr; Korendiy, Vitaliy; Kuzio, Ihor; Lviv Polytechnic National UniversityFriction treatment refers to surface strengthening (hardening) methods using highly concentrated energy sources. In the course of this processing in the surface layers of the processed surfaces of parts the strengthened layer with nanocrystalline structure is formed. The formed layer has specific physical, mechanical, chemical properties, as well as improved performance properties, which are significantly different from the base metal. A highly concentrated energy source is formed in the contact area of the tool-part due to the high-speed friction (60–90 m/s) of the tool on the treatment surface. Frictional treatment of flat parts according to the kinematics of the process is similar to grinding. The strengthening process was carried out on an upgraded surface grinder. The tool is a metal disk made of stainless-steel. Transverse grooves are formed on the working surface of the tool to intensify the process of forming a strengthened (reinforced) layer with a nanocrystalline structure. The grooves form additional shock loads in the contact area of the tool-treatment surface of the part. These shock loads increase the shear deformation of the metal of the parts’ surface during treatment, which affects into formation the quality parameters of the parts’ surface and surface layer. To study the friction treatment process, the calculation scheme of the elastic system of the machine was developed. A simulation model for the study of dynamic processes that take place during the friction treatment of flat surfaces was built. This model gives possibility to determine the displacements and velocities of the machine table on which the part is fixed and the tool, and to determine their mutual displacement and also calculate the reaction of the machine table.