RU2564043C2 - Method to determine material processability - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: parameters of acoustic emission signals are recorded, i.e. number of pulses of amplitude distribution mode corresponding to plastic deformation at turning operation. The root-mean-square value of the signal in the considered time interval (Urms) is calculated for the acoustic emission signal registered by the sensor. Amplitude-frequency representation of the acoustic emission signal is obtained by Fourier transformation, median frequency value (F_med) is determined. Their product (Urms×F_med) is used to evaluate the processability of the material.

EFFECT: reduced time and labour content of determining the material processability, determination of absolute, not relative, processability value.

3 dwg, 2 tbl

Description

The invention relates to the processing of materials by cutting and can be used in mechanical engineering for an accelerated automated assessment of the machinability of both traditionally used steels and alloys under changing cutting conditions, and new grades of alloys, deposited and composite materials, etc.

A known method for determining the optimal cutting speed (SU 1306649 A1, IPC B23B 25/06, filing date 11/18/1985), as one of the parameters characterizing the workability of the material.

The essence of the known method is as follows. The cutting speed is changed in a predetermined range and the vibroacoustic signal emitted by the cutting zone is simultaneously recorded, from which a growth outbreak signal is determined, which is determined by comparing the components of the vibroacoustic signal and growth particles on the cutting surface at the same time, the frequencies of the selected signal are determined, and the optimal signal take the speed at which the frequency of the allocated signal is minimal. The frequency of stalling is correlated with the wear rate of the cutting tool.

The main disadvantage of this method is that to determine the cutting speed at which the growth rate of the outgrowth, and hence the wear rate of the cutting tool, is minimal, it is necessary to carry out measurements in a wide range of cutting speeds, such that the desired value of the optimal cutting speed (minimum speed wear) obviously fell into this range. And this significantly increases the time required and the complexity.

There is also a method of evaluating the workability of materials (SU 1377675 A1, IPC G01N 3/58, filing date 12/19/1985), which consists in performing mechanical turning of the disks from the reference and test materials being processed at the same spindle speed, selected from the condition of not exceeding the value of tool wear for one cycle of processing the end face of the critical value, and as a parameter characterizing the workability of the material, determine the number of pulses of the mode of the amplitude distribution of acoustic signals th emission corresponding to plastic deformation when turning.

The method requires compliance with the relative constancy of the conditions for conducting research for a particular batch of materials and allows you to determine only the relative coefficient of machinability of materials of this batch in comparison with the reference, which significantly limits its widespread use in practice. In addition, the question remains: what material to choose as a reference for a given batch?

The objectives of the invention are: reducing the time and complexity of determining the workability of materials, determining not the relative, but the absolute value of workability.

The tasks are solved by the fact that in the method for evaluating the machinability of materials by cutting, which consists in recording the parameters of the acoustic emission signals — the number of pulses of the amplitude distribution mode corresponding to plastic deformation during turning, according to the invention, the mean square value of the signal in the considered time interval is calculated for the acoustic emission signal recorded by the sensor (Urms), using the Fourier transform get the amplitude-frequency representation of the acoustic signal emission, the median frequency (F _med ) is determined, and their work is used to judge the workability of the materials.

The technical result of the invention is expressed as follows. Due to the existence of a linear relationship between the workability of the material and the value of the product of the parameters of the acoustic emission signals (Urms × F _med ), it becomes possible to significantly reduce the complexity and time of the process of evaluating the workability of materials, and the scope of its application in practice is expanding. In addition, all necessary procedures of the invention can be automated.

The proposed method is implemented as follows. When turning, a broadband acoustic emission sensor (AE) is mounted on the tool holder, turning is performed, the received AE signal is processed in an automated mode - the average square value of the signal is calculated in the considered time interval, and the amplitude-frequency representation of the signal is calculated using the Fourier transform for which the value of the median frequency (F _med ). The value of the product Urms × F _{med of} these two parameters of AE signals allows us to unambiguously judge the workability of materials.

Example. For the experiment, 6 alloy steel samples were used as the processed material (table1)

Table 1 No.
p / p steel grade Designation of a sample one 18X1G1FR 2 2 20X1G1F 3 3 20X1G1R four four AC40X 5 5 40HGNM 6 6 20X1G1FR 9

To ensure rapid wear as a tool plate were selected HSS R6M5F3 _-0,1 square 13 mm, a clearance angle of 12 °, 4.5 mm thickness, mounted in the tool holder. Geometrical parameters of the plate installed in the holder: rake angle 0, rake angle 12 °, main and auxiliary angle in plan 45 °. The amount of wear was determined on an MBS-10 microscope (magnification-scale 4) with a MU500 eyepiece camera.

As a criterion for comparison, the calculated specific wear of RUI, μm / end face, was used.

RUI = h / N1000,

where N is the number of machined ends, the amount of wear (the maximum height of the chamfer wear of the cutter in the direction perpendicular to the cutting edge).

AE signal processing was carried out in Matlab. The rms value of the signal and the F _med value of the median frequency of the amplitude-frequency representation of the AE signals were calculated. Then, we plotted the dependences of the calculated specific wear of the RUI on the product Urms × F _med .

Processing by cutting was carried out at three turning speeds: 315, 400, 500 rpm, figure 1, figure 2, figure 3.

The results obtained are summarized in table 2 and are presented graphically for clarity. It can be seen that with a correlation coefficient of R ² close to unity, a linear relationship of RUI from Urms × F _{med is found} , which allows you to quickly determine the values of material workability for a given cutting speed. Machinability values for other cutting speeds can be obtained by approximating already known data.

table 2 Steel Number 5 Number 2 Number 3 Number 6 Number 4 Number 9 RUI (calculation, destiny, wear of turning) 5.50 4.00 3.25 1.88 1,50 1.30 Speed 315 rpm Urms, conv. 0.29 0.19 0.18 0.15 0.13 Fmed, kHz 146.28 138.27 117.30 111.87 115.45 108.17 Urms × Fmed 41.72 26.49 21.37 16.54 15.31 11.64 Speed 400 rpm Urms, conv. 0.44 0.32 0.28 0.16 0.15 0.12 Fmed, kHz 136.25 130.41 110.54 109.16 107.68 95.78 Urms × Fmed 60.37 41.20 30.74 17.58 15.91 11.91 Speed 500 rpm Urms, conv. 0.68 0.54 0.47 0.24 0.20 0.19 Fmed, kHz 104.09 99.31 90.78 85.79 85.72 86.06 Urms × Fmed 71.11 54.03 42.80 20,44 17.54 15.98

Claims (1)

A method for determining the machinability of materials by cutting, which consists in recording the parameters of acoustic emission signals - the number of pulses of the amplitude distribution mode corresponding to plastic deformation during turning, characterized in that for the acoustic emission signal recorded by the sensor, the mean square signal value in the considered time interval (Urms) is calculated, s using the Fourier transform get the amplitude-frequency representation of the acoustic emission signal, determine the value of m uniform frequency (F _med ), and by their product (Urms × F _med ) they judge the workability of the material.

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