RU1623394C - Method of measuring temperature of contact interaction when cutting - Google Patents

Abstract

FIELD: test equipment. SUBSTANCE: cutting tool and item under treatment are connected to form electric circuit; in this case natural thermocouple is produced. Electric registering circuit is short-circuited during measurement process by means of low-ohmic shunt, and short-circuit current is measured in it. Temperature at contact area is determined from the value of short-circuit current. EFFECT: improved precision of measurement. I tbl

Description

 The invention relates to the study of the contact interaction of materials, for example metals, during friction and cutting, an important parameter of which is the contact temperature.

 The aim of the invention is to increase accuracy.

 The method is based on the known method of determining the temperature with the formation of the so-called natural thermocouple, when a cutting tool with a workpiece is included in the electrical circuit. The natural thermocouple in its classical form (when measuring its EMF with a voltmeter in idle mode) does not provide temperature information, because in contact interaction, static electrification of metals takes place. Consequently, the signal measured in this method is not only thermoEMF, but also any kind of EMF (by the definition of EMF, it is a force of a third-party, non-electric nature) and therefore it is called quasi-EMF.

 The described method uses the fact that the nonlinearity of the I – V characteristic of the transition resistance in the contact region of the materials under study disappears at a significant current through the contact. When measuring an electrical signal in the short circuit mode of an energy source that occurs during contact interaction during friction (cutting) of electrically conductive bodies, static electrification distorting the value of thermoEMF during measurement in idle mode disappears. The contact becomes linear, and the potential difference corresponding to such a state can be more reliably identified with thermoEMF.

где I_макс ток короткого замыкания;
ε термоЭДС;
R суммарная нагрузка цепи, включающая сопротивление амперметра и линейное переходное сопротивление контакта.For a linear circuit:
I _max

where I _max short circuit current;
ε thermoEMF;
R the total load of the circuit, including the resistance of the ammeter and the linear contact transition resistance.

Then
I _max ≈ ε ≈ θ where θ is the contact temperature.

To implement the method, close the investigated pair of parts with a low-resistance shunt and measure the short-circuit current I _max in the low-resistance circuit, which will be proportional to the desired temperature. The voltage drop across the model resistor manganin sheet with a nominal value of 1 mOhm included in the circuit was used as the measured signal. If it is necessary to determine the absolute temperature in one of the experiments, it is measured by any of the known methods.

 The specified method was tested when cutting metals with a cutter equipped with a T15K6 hard alloy without coolant. The table for various materials shows the short-circuit currents measured in a low-resistance circuit R ≈ 16 mΩ.

The temperature was determined in accordance with a known method according to the formula:
θ _x θ _st45 I _max / I _{max st. 45,} where θ _{x is the} desired temperature.

Claims (1)

 METHOD FOR DETERMINING THE TEMPERATURE OF CONTACT INTERACTION WHEN CUTTING, comprising connecting the cutting tool and the workpiece to an electrical recording circuit to form a natural thermocouple, characterized in that, in order to increase accuracy, the electrical recording circuit is short-circuited by a shunt and the short-circuit current established in it is measured, the current value which determine the temperature of the contact interaction.

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