No abstract

No abstract

Abstract. The use of ultrasonic energy is a promising way to improve the efficiency of the grinding process. However, the analytical study of local temperatures during ultrasonic grinding was not performed. In the process of research, physical and mathematical models have been developed for calculating the temperature field during grinding, taking into account the change of the kinematics of microcutting by abrasive grains and the change of the mechanical characteristics of the workpiece material when ultrasonic vibrations are applied. The models take into account that the parameters, characterizing the workpiece material resistance to dispersing, and the thermophysical properties of abrasive grain, workpiece, chips and external environment, depend on the temperature. The modeling was performed on the basis of a simultaneous solution of the thermal conductivity differential equations, written for each interacting object. For equation calculation the finite-element method was used. The methodology and software for the temperature field calculation have been developed. The temperature modeling results are shown. The effect of the vibration amplitude and phase on the local temperatures in the area of abrasive grain, chips and workpiece contact, including the grain and the workpiece contact time, has been determined. The factors affecting the local temperatures have been determined. During ultrasonic activation the workpiece temperature is lowered by 10 %, and the local temperatures in the abrasive grain, workpiece and chips contact area are lowered by 30 %.

No abstract

The paper is devoted to theoretical studies of the feasibility to determine the clearance size in the friction units of an internal combustion engine by the magnitude of the electromotive force (EMF) that arises in them. The effect of the contact area of the friction pairs and the clearance between them on the electrical resistance in the contact, and, accordingly, on the magnitude of the emerging EMF was theoretically confirmed. As a result of the theoretical studies, the relationship of the influence of changing clearances on the magnitude of the EMF arising in them was established. To confirm the theoretical calculations, bench studies of the UMZ-417 engine were carried out to determine the magnitude of the EMF arising in its friction pairs depending on the change in the crankshaft rotation speed, followed by micrometry of the parts. The study was carried out using the designed current collector. The obtained theoretical and experimental results confirm the feasibility of determining the condition of friction units by the magnitude of the EMF generated in them and with sufficient accuracy to determine the dynamics of the clearance size between rubbing parts.