Zastavskyi K. Forming of the tool environment during magnetic abrasive processing in large magnetic gaps

In the dissertation work, a methodology for determining the forces acting on the part from the side of the magnetic tool (MAT) was developed, which allows establishing the features of the formation of the MAI in the process of magnetic abrasive processing (MAF). For the first time, the real magnitude of the force at MAF was determined, as well as the processes and manifestations that affect them in view of changes in technological factors, such as magnetic field induction, speed of movements during processing, type, shape and size of MAP particles and material of details. Recommendations on the intensification of the MAF process have been developed, taking into account the features of the formation of the MAT and the real magnitude of the force. The samples for the study were cylindrical square and triangular prisms with a height of 30 mm and a characteristic size of 8, 12, and 16 mm made of ferro-para- and diamagnetic materials, and a 1 mm-thick and 30-mm-high turbine blade made of a titanium alloy. The technique of measuring the effective torque on the shaft of the motor rotating the part and measuring the resistance force using a strain gauge was used to measure the force at MAF. Appropriate equipment was designed, which made it possible to taking into account the most required factors in this study. The ferromagnetic powders were used for the formation of MAI: fragmented Polymam-T with a grain size of 200/100 μm, 400/315 μm, and rounded Polymam-M 200/100 μm, 400/315 μm. It was established that the effective moment of friction when processing a ferromagnetic detail (according to sample data and technological conditions) is up to 1.4 Nm, when processing non-magnetic details - up to 0.9 Nm. It is shown that the effective moment of friction directly depends on the magnitude of magnetic induction, the speed of movement of parts in the working area and around its axis. It was determined that the resistance force during processing of cylindrical parts has a linear dependence on the magnitude of the magnetic induction and is 720 N/T for powder with a grain size of 200/100 μm and 960 N/T – for 400/315 μm. It is shown that the strength of resistance during processing of non-magnetic materials (aluminum, titanium and bronze) has no significant differences. It was established that the frontal resistance forces at MAF of ferromagnetic samples, as well as for non-magnetic samples, do not depend on the processing speed and vary in the range from 160 to 220 N, which is 1.2 – 1.5 times higher than for non-magnetic parts (80 - 180 N). In first time, it was determined that when processing paramagnetic parts, the increase in resistance with increasing diameter is not proportional to the increase in diameter (when the diameter increases by 2 times, there is a 1.5-fold increase in resistance), which is explained by the differences in the nature of processing with different structural elements of the MAT. On the other hand, the processing of ferromagnetic parts is characterized by a proportional increase in the resistance force due to the increase in the size of the parts. It has been confirmed that when processing thin parts such as a gas turbine blade at high processing speeds of 3-3.5 m/s, the phenomenon of a spindle-shaped formation of the MAI occurs, which is accompanied by a sharp (up to 25%) decrease in the resistance force. It was determined that bringing the processed surfaces of ferromagnetic parts closer to the working surfaces of the pole tips not only increases the resistance force by 20-70%, but also intensifies the cutting process by 20-30%. This occurs due to the interaction of the machined surfaces of the part with the compacted formations of the MAT. In view of this, it was proposed to take into account the presence of compacted zones of the MAT when developing the technological processes of the MAF. The work made it possible for the first time to investigate the influence of the rheological properties of the MAF in the conditions of a large magnetic gap on the force interaction processes occurring between the MAT and the real detail during MAF, taking into account the characteristics of the processed detail and magnetic abrasive powders. In the course of the work, theoretical assumptions were experimentally confirmed regarding the influence of the MAI characteristics and technological factors on the force interaction of the detail with the MAT at MAF in large magnetic gaps. The relationship between the forces arising between the processed part and the MAT and the material removal processes during the MAF is determined. The results of the work made it possible to clarify the mechanism of the formation of the MAT and the peculiarities of its interaction with the surfaces of parts of a complex shape in the conditions of large magnetic gaps of the ring type, which made it possible to expand the possibilities of the MAF method and increase its efficiency and productivity.