Determination of completion time of thermal preparation stage of a furrow opener disc being reconditioned by electrocontact heating

Abstract

The possibilities of transition from a rod (one-dimensional) mathematical model of the heating of forming electrode in the system “electrode - part - heat dissipating mass” presented in the form of a boundary inverse problem of thermal conductivity to a direct problem are shown having an analytical solution in adiabatic approximation over a short time interval, to determine the time of completion of the first stage (stage of thermal preparation of the part for plastic deformation) of the process of reconditioning the cutting edge of the disc of a seed drill by means of electromechanical deformation. Innovative design of electric power supply and realization of push-to-electrode force is proposed including flat current-conducting rod rectangular section (copper rail) the thickness of which is significantly smaller than the width bolted to a similar electroceramic rod (forming electrode; the second electrode is the repairable disc), the lower inclined surface of which forms a linear electrical contact with the conical part of the retractable disc when the installation is started. After application to the upper inclined surface of the electrode through a layer of heat-insulating ceramic having the required electrical and mechanical strength of the specified force, the linear contact passes into a flat electric contact. After the short-circuited application of electric voltage in the disc, there are complex mutually related thermal, electrical and thermomechanical processes that are difficult to be described mathematically with sufficient precision and implemented by modern microprocessor technology. The substantiated simplifications make it possible to obtain a calculation formula for calculating the time of completion of the stage of thermal preparation of worn disc on the basis of an approximate-analytical solution of the boundary inverse heat conduction problem.