RU2758272C1 - Method for verification of device for measuring contact potential difference of metal parts of aviation equipment - Google Patents

Abstract

FIELD: aircraft engineering.

SUBSTANCE: invention relates to the field of non-destructive testing of metal parts of aircraft equipment during their manufacture, operation and repair. To verify the device for measuring the contact potential difference, a reference sample made of a conductive material that is the same as the material of the measuring electrode of the device sensor is used. The surface of the reference sample is processed according to the same technology as the surface treatment technology of the measuring electrode of the sensor. The distance from the measuring electrode to the end of the device sensor is 0.5 mm. Before verification, the surfaces of the measuring electrode of the device sensor and the reference sample are thoroughly cleaned, the charging level of the device battery is checked. For measurement, the device sensor is applied to the surface of the reference sample at an angle of 90°. Measurements are carried out in stationary environmental conditions. Based on the results of at least 10 measurements on the surface of the reference sample, the arithmetic mean of the contact potential difference and the average square deviation are calculated, the values of which are used to judge the serviceability and accuracy of the contact potential difference measurement device.

EFFECT: simplification of the verification procedure.

1 cl, 1 dwg

Description

The proposed invention relates to the field of non-destructive testing of metal parts (MD) of aviation equipment (AT) during their manufacture, operation and repair.

During the production, operation and repair of AT, it is important to control the surface condition of its MD. The surface condition of AT parts largely determines their operational properties. However, determining the state of the surface of the MD AT is a difficult task [1].

When determining the technical condition of the surface of metal aircraft parts by means of non-destructive testing in order to ensure the uniformity and accuracy of measurements, it is necessary to verify the devices used for non-destructive testing.

Known device for measuring the CRP MD AT, related to the means of measuring the method of CRP electrical type of non-destructive testing of machine parts. The CRP method is based on comparing the work function of the electron from the controlled object (CO), for example, a metal aircraft part, and the previously known work function of the output from the measuring electrode (IE) of the sensor of the CRP measuring device according to the formula [2]:

where U _to - KRP, V;

Ф _KO - work function of an electron from KO, J;

Ф _ИЭ - work function of the electron output from the ИЭ sensor of the device for measuring the CRP, J;

- единичный заряд электрона, Кл.

- unit charge of an electron, Cl.

The CRP method is very sensitive to the state of the KO surface. The cleanliness of the surfaces of the sensor IE of the device for measuring the CRP and KO affects the accuracy of measurements of the CRP especially strongly. Therefore, the measurements of the CRP should be preceded by a thorough cleaning of the surfaces of the KP and IE of the sensor of the device for measuring the CRP [3].

When measuring the CRP, there is a fluctuation of its values. Therefore, the results of measurements of the CRP MD should be processed by the methods of mathematical statistics.

To ensure the accuracy of the IFC measurements, the calibration of the IFC measuring device is required.

There are known methods for verifying measuring instruments, for example, methods [4-6], which consist in comparing the measured values of the calibrated measuring instrument with an exemplary measuring instrument. The disadvantage of verification methods [4-6] is the need for the use of exemplary certified measuring instruments, the certification of which was carried out immediately before verification.

A known method for determining the metrological characteristics of the same type of measuring instruments in the group [7], which consists in the formation of a group output signal of several measuring instruments processed by an electronic computer. The disadvantages of this method are high financial and time costs.

Closest to the proposed invention is a method for determining the errors of the meter KRP [8]. This method is implemented by a device containing a dynamic capacitor with plates, one of which is a measured sample, and the other is a reference, a resistor, an amplifier, a null indicator, a compensation voltage source, and a potential source that simulates the CRP. To implement the method, a potential is supplied to the reference sample from a potential source, which, together with the CRP, is compensated by the potential of the compensation voltage source. At the amplifier output, the residual uncompensated potential is measured with a zero indicator. The values of the measurement error at various values of the KPD value are determined by the formula:

U _p = ± (U _os / K⋅A),

where U _p is the error of the KRP meter;

U _oc - residual uncompensated potential;

K is the gain of the amplifier of the KRP meter;

A is the conversion factor of the dynamic capacitor of the KRP meter.

The method [8] can be used to verify the measuring device proposed in the prototype, but it is difficult to use it to verify devices of a different design, for example, the device for measuring the CRP [2].

The technical result of the claimed invention is the ability to calibrate devices for measuring the CRP MD of various designs in an effective, simple, inexpensive way that can be used in non-destructive testing during the production, operation and repair of AT.

The claimed technical result is achieved as follows. To verify the device for measuring the contact potential difference of metal parts of aviation technology, a reference sample is used made of a conductive material, which is the same as the material of the measuring electrode of the device sensor, the surface of the reference sample is processed according to the technology that is the same as the technology of processing the surface of the measuring electrode of the sensor, while the distance from the measuring electrode to the end of the sensor of the device for measuring the contact potential difference, which determines the distance from the electrode to the surface of the reference sample is 0.5 mm, thoroughly clean the surfaces of the measuring electrode of the device sensor and the reference sample before verification, check the battery charge level of the device; then the sensor of the device for measuring the contact potential difference is applied to the surface of the reference sample at an angle of 90 °, while measuring the contact potential difference on the reference sample is carried out under stationary environmental conditions; according to the results of at least 10 measurements on the surface of the reference sample, the arithmetic mean value of the contact potential difference and the standard deviation are calculated, the values of which are used to judge the serviceability and accuracy of the device for measuring the contact potential difference.

In the particular case for a nickel electrode, the arithmetic mean of the measured values of the contact potential difference on the reference sample is no more than 15 mV, and the standard deviation is no more than 5 mV.

Verification of the device for measuring CRP MD AT is carried out:

- before each use;

- if necessary, periodically (it is recommended not less than every 30 minutes) during long-term measurements of the CRP;

- when detecting abnormal measured values of the CRP on the surface of the KO.

Measurements of FOC on the surface of MD AT, as well as metrological support, must be carried out by a qualified performer.

Prior to use, the FPC measuring device shown in FIG. 1 is inspected visually for defects, primarily such as cracks and deformations. FIG. 1 numbers indicate:

1 - KO;

2 - dynamic capacitor;

3 - IE of the sensor of the KRP measuring device;

4 - oscillatory circuit;

5 - preamplifier;

6 - sensor;

7 - oscilloscope.

The dynamic capacitor (2) is formed by KO (1) and IE (3).

When examining the device for measuring the CRP, special attention should be paid to the visual inspection of the IE (3). If necessary, an additional light source and a magnifying glass should be used during the inspection.

Then it is necessary to measure the distance between the IE (3) and the end of the sensor body (6) applied to the KO (1), which should be 0.5 mm (Fig. 1). The distance from the end of the sensor body (6) applied to the KO (1) to the IE (3) can be determined with a depth gauge or a template.

Then it is necessary to verify the accuracy of measuring the CRP device [2]. When verifying the measurement accuracy, a reference sample is used (two samples can be used: the main one and the control one), made of the same material as the IE (3). The surface of the sample was processed using the same technology as the surface of the IE (3). When measuring the CRP between the IE (3) and the reference sample, which are made of the same material and processed using the same technology, the CRP will tend to zero, but it will not completely disappear, because the value of the CRP is influenced by many factors, for example, adsorption processes that are not the same on the surfaces of the IE (3) and the reference sample.

Before carrying out the verification, it is necessary to thoroughly clean and dry the surfaces of the KO (1) and IE (3) of the KRP measuring device. To ensure sufficient cleaning efficiency and reduce the drying time of surfaces, we suggest using petroleum ether or ethanol.

Before measuring the FOC, it is necessary to check the adequacy of the battery charge of the portable device for measuring the FOC, because due to insufficient battery charge, an off-design amplitude and frequency of oscillations of the IE (3), which forms a dynamic capacitor (2) with the surface of the KO (1), can occur. This can reduce the accuracy of the FOC measurements.

The sensor (6) on the surface of KO (1) should be installed strictly at an angle of 90 ° (Fig. 1). Otherwise, the skew of the sensor introduces errors in the results of measurements of the CRP.

The verification of the device for measuring the CRP and measuring the CRP MD AT must be carried out in laboratory conditions, because non-stationary environmental conditions, for example, changes in temperature and (or) humidity, significantly affect the accuracy of measurements of the CRP. Moreover, the simultaneous change in temperature and humidity of the environment when measuring the CRP on the surface of the MD AT enhances this negative effect on the measurement accuracy [9].

When carrying out verification, it is advisable to make at least 10 measurements of the CRP on the reference sample and, from the results of the measurements, find the arithmetic mean value of the CRP and its standard deviation [10].

Our experimental studies have shown that the criterion for the serviceability of a device for measuring CRP [2], having IE (3) made of pure nickel, is the arithmetic mean value of the measured CRP on a nickel reference sample processed according to the same technology as IE (3), which is no more than 15 mV. In this case, the standard deviation of the measured values of the CRP on the reference sample should be no more than 5 mV.

The root-mean-square deviation of the CRP values measured on the surface of the reference sample of more than 5 mV may indicate either unsatisfactory cleaning of the IE (3) and / or the reference sample, or non-observance of the stationarity of environmental conditions during measurements, or a malfunction of the CRP measuring device [2].

It is recommended to use the two already mentioned reference samples when checking the device for measuring the CRP [2] - the main one and the control one, made of the same material as the IE (3) of the device [2] and the surface of which is treated in the same way as the surface of the IE (3) device [2]. If, when checking the device [2] on the main nickel standard sample, the arithmetic mean value of the CRP measurements turns out to be more than 15 mV, it is necessary to re-verify the device [2] using another, control nickel standard sample, processed similarly to IE (3) and the main standard sample. This will allow you to detect possible defectiveness of the main reference sample. If the arithmetic mean value of the measured CRP on the control nickel standard sample turns out to be more than 15 mV, then the device for measuring the CRP [2] is faulty, but if it is less than 15 mV, then the main nickel standard sample is defective, which must be replaced.

In case of detection of malfunctions of the device for measuring the CRP during verification, it is necessary to restore its serviceable state before it is used for its intended purpose during non-destructive testing of MD AT.

Our proposed method for verifying the device for measuring the CRP is effective, simple and inexpensive. It can be used for non-destructive testing of MDs during their production, operation and AT repair.

Sources of information

1. Oleshko B.C. Preparation of military aircraft for repair: a textbook. - M .: Publishing house MAI, 2016 .-- 72 p. - ISBN 978-5-4316-0378-5.

2. Patent for invention RU 2717747 from 03/25/2020

3. Patent for invention RU 2488093 dated July 20, 2013

4. Copyright certificate SU 416641 dated 11/25/1974

5. Copyright certificate SU 507133 dated 07/05/1978.

6. Copyright certificate SU 1290217 from 15.02.1987

7. Patent for invention RU 2123190 from 10.12.1998

8. Copyright certificate SU 1255943 dated 09/07/1986

9. Yurov V.M., Oleshko V.S. The impact of the environment on the contact potential difference of metal machine parts // Eurasian Physical Technical Journal, 2019, volume 16, no 1 (31), pp. 99-108, DOI: 10.31489 / 2019No1 / 99-108.

10. Goncharenko V.I., Oleshko B.C. The method of contact potential difference in assessing the energy state of the surface of metal parts of aviation technology: monograph. - M .: Publishing house MAI, 2019 .-- 160 p. - ISBN 978-5-4316-0631-1.

Claims (2)

1. The method of verification of the device for measuring the contact potential difference of metal parts of aviation technology, which consists in the fact that for verification of the device for measuring the contact potential difference, a reference sample is used, made of a conductive material, the same as the material of the measuring electrode of the sensor of the device, the surface of the reference sample is processed according to the technology, identical with the surface treatment technology of the measuring electrode of the sensor, while the distance from the measuring electrode to the end of the sensor of the device for measuring the contact potential difference, which determines the distance from the electrode to the surface of the reference sample, is 0.5 mm, thoroughly clean the surfaces of the measuring electrode of the device sensor and the reference sample, check the battery level of the device; then the sensor of the device for measuring the contact potential difference is applied to the surface of the reference sample at an angle of 90 °, while measuring the contact potential difference on the reference sample is carried out under stationary environmental conditions; based on the results of at least 10 measurements on the surface of the reference sample, the arithmetic mean value of the contact potential difference and the standard deviation are calculated, the values of which are used to judge the serviceability and accuracy of the device for measuring the contact potential difference, while the device for measuring the contact potential difference contains a controlled object, a dynamic capacitor, an oscillatory circuit, a measuring electrode of a sensor of a device for measuring a contact potential difference, a preamplifier, a sensor, an oscilloscope. 2. The method of verification of the device for measuring the contact potential difference of metal parts of aviation equipment according to claim 1, characterized in that for the nickel electrode the arithmetic mean value of the measured values of the contact potential difference on the reference sample is no more than 15 mV, and the standard deviation is no more than 5 mV.

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