The temperature of the holes of the bearing rings when grinding with a precast textured wheel

The problem of reducing the thermal stress of the grinding process of bearing rings has been viewed. The possibility of reducing the temperature of the treated surface based on the use of precast textured grinding wheels has been presented. Experimental models of pulse, contact, average temperature, velocities and rates of their change in the function of grinding time are found.

Influence of Grain Shape in Grinding Wheels on the Machining Quality of Bearing Rings

The quality of grinding of bearing races is related to their performance and durability. The aim of this work is to establish how the machining quality of bearing rings depends on the characteristics of grinding wheels, in particular, on such a parameter as the shape of abrasive grains. Several batches of experimental grinding wheels were made, containing grains of different shapes (from isometric to lamellar varieties). Quantitatively, the shape of the grains was estimated by the shape factor parameter (SF), which is equal to the ratio of the diameters of inscribed and circumscribed circles in the contours of the used grains. The shape factor was determined using a scanner or a digital microscope and a special computer program. The tests were carried out on circular, plunge, and finishing grinding, using coolant, on a SIW 4E machine in a bearing factory. The machining quality of the bearing rings was assessed by studying the microstructure, microhardness and roughness of their bearing races. The durability of grinding wheels was determined by the number of machined rings before maximum tool wear. It has been established that by a differentiated approach to the choice of grain shapes in the wheel, it is possible to significantly increase its operational capabilities: increase the microhardness of the ground surfaces, reduce the roughness of processing, and increase the durability of grinding wheels.

Improving the Thermal Fatigue Strength of Hot-Working Tools by Laser Treatment

A method for increasing the thermal fatigue strength of a tool used in hot forming of bearing rings by applying circular laser tracks to the working surfaces is considered. Laser treatment is carried out with a power of 2.0...2.5 kW by applying on the end face working surface of the tool in the direction from the center to the periphery of the circular tracks with a common center coinciding with the center of the circumference of the end face; the tool is rotated at a constant angular rate, the spot diameter ds for each track is selected according to the dependence ds,i+1/ds,i = 0.85...0.90, and the laser radiation spots of adjacent tracks have a common point of contact. The results of pilot testing are presented, which confirmed the high technical and economic efficiency of the use of laser quenching for ejectors and punches. A tool made by machining, for example, an ejector of an AMP-70 automatic press, is subjected to volume quenching and tempering. The ejector material was steel 3Kh3M3F, quenching temperature in oil – 1030...1050 °С, tempering temperature – 580...610 °С. After volume quenching, additional machining is carried out, usually grinding, in order to remove the decarbonized layer of material formed during heat treatment and to give the working surface the required roughness class. The final stage in the tool manufacturing is the quenching of its working surface by laser treatment. Pilot testing showed that the use of laser treatment made it possible to increase the durability of ejectors of various types by 2 ... 3 times, of deforming punches – by 2.2 times.

DEVELOPMENT OF METHODS OF RELIABILITY ASSESSMENT FOR TURRET BALL BEARING RING OF A BMP-2 INFANTRY FIGHTING VEHICLE

A large part of BMP-2 Infantry Fighting Vehicles needs to replace turret ball bearing rings. Under realization of replacement of spare parts and components made in Russia with domestic ones, KNVO "Fort" MVO Ministry of Internal Affairs of Ukraine made an experimental batch of balls for turret ball bearing rings of infantry fighting vehicles BMP type. As a result of modernization of a turret ball bearing ring, steel balls were replaced with balls made of composite material. A turret ball bearing is a large radial thrust bearing, cages of which are turret races. A stabile lower race is fixed by means of screws to a top of the vehicle‟s hull. Above the fixed race there is a movable upper race to which the turret is bolted. A method for assessing the reliability of turret ball bearing rings of military armored vehicles was developed. The results of tests of turret ball bearing rings of BMP-2 infantry fighting vehicle tower are given. The reliability of turret ball bearing rings of armored vehicles was assessed taking into account the damage to the balls. The main types of damage to the balls: non-compliance of balls average diameter and non-compliance of the spherical shape of the ball to the requirements of operating documentation. The impact of the probability of no-failure operation of the balls on the durability of the ball bearing is determined. It is necessary to take into account the presence of damage to the balls when determining the durability of the ball bearing. To validate the adequacy of the method, it is necessary to increase the test time of the ball bearing by conducting tests during its operation.

Effect of conjugated system extension on structural features and electron-density distribution in charge–transfer difluoroborates

A comparative structural study of two related donor–acceptor pyridine-based BF2 complexes, namely, 3-(dimethylamino)-1,1-difluoro-1H-pyrido[1,2-c][1,3,5,2]oxadiazaborinin-9-ium-1-uide, C8H10BF2N3O (1), and 3-{(1E,3E)-4-[4-(dimethylamino)phenyl]buta-1,3-dien-1-yl}-1,1-difluoro-1H-pyrido[1,2-c][1,3,5,2]oxadiazaborinin-9-ium-1-uide, C18H18BF2N3O (2), containing a dimethylamino group and either the shortest (in 1) or the longest (in 2) charge-transfer path known until now in this family of compounds, is presented. Single-crystal X-ray diffraction analysis supported by computational investigations shed more light on these systems, indicating, among other aspects, the predominance of C—H...F contacts in 1, the formation of antiparallel dimers held together by π–π interactions in both compounds, and the involvement of fused BF2-bearing rings in the charge-transfer process.

Working in of roller ends and bars of cylindrical roller bearings at combined radial and axial loads

The paper investigates the influence of the process of running-in the ends of rollers and sides of cylindrical roller bearings on the conditions of hydrodynamic contact of these parts: the formation of an oil film and friction. For this purpose, the results of finite element modeling of the stress-strain state of the bearing parts in contact: the inner ring, the side flange and a fragment of the axle of the wheelset, and the multi-mass simulation of the dynamics of the bearing operation are used. The influence of the yaw angle of the roller on the size and shape of the contact area on the side is investigated. The dependences for calculating the thickness of the oil film in the contact between the ends of the rollers and the flanges of the bearing rings are being refined, which now make it possible to take into account the misaligned position of these parts during their force interaction. The results are illustrated using the example of a roller bearing of standard size 232926.

Experimental Determination of Heat Transfer using a Polymer Solution Shower during Induction Hardening*

Heat treatment simulation of inductive surface hardening of large bearing rings is a challenging multi-physical task. Besides the determination of material and process parameters of induction heating, the quenching process must be modelled to obtain realistic results concerning surface hardening depth as well as information about residual stresses and distortions of the bearing rings. A common method to model quenching processes is to determine heat transfer coefficients for the specific process depending on component surface temperature. This method was used to characterize the shower cooling process using an aqueous polymer solution of a modified polyalkylene glycol (PAG) type. A specifically designed test set-up allowed to determine the heat transfer coefficients for different distances between shower and hot specimen as well as for different impingement angles of the fluid relative to gravitation. Additionally, the calculated heat transfer coefficients were checked and corrected by FEM simulations.

Analytical Modeling of Cutting Forces and Technological Parameters Interrelation when Grinding Shafts' Ends by a Grinding Wheel End on Circular Grinding Machines

Abrasive processing remains one of most demanded for hardened steels parts. Grinding of end surfaces of machines parts has become widespread due to the fact that it allows processing heat-treated surfaces more efficiently than turning and also correcting the surface geometry. This processing type is used almost mainly for finish processing operations of shafts ends, bearing rings, gears, etc. However, there is still no mathematical model for this processing type, which would satisfy most of the main technological parameters. In this article a mathematical model of the cutting force when grinding the shaft end by the grinding wheel end on circular grinding machines is obtained. Processing schemes for this grinding type are given and the calculated graph of the cutting force according to the obtained mathematical model is shown.