RU2702537C1 - Method for rapid assessment of results of electron-beam thermal action on objects in a vacuum chamber - Google Patents

Abstract

FIELD: monitoring systems.

SUBSTANCE: invention relates to a method of monitoring structural, phase and chemical transformations in a near-surface layer of treated objects in vacuum chambers under the effect of electron-beam pulses and can be used to increase reliability and durability of wide range of parts of machines. Waveguide is connected to the processed object, it is taken outside the limits of the vacuum chamber through a vacuum input and a vibration sensor is fixed on the waveguide. Information is processed using a computer. Waveguide used is a flexible wire, the vibration sensor used is an accelerometer with a frequency characteristic covering the frequency range up to 100 kHz. During electron beam pulse action, dependences of current effective values of signals coming from accelerometer are recorded from time in two frequency ranges till moment of signal amplitude drop to level of background noise. As the frequency ranges the octave band with the highest effective signal amplitude value and the neighboring higher high frequency octave is selected, the time period "T" is determined, during which the signal amplitude exceeded the background value, calculating the effective value of signal "A" on entire period "T", estimating energy "U" of signal by formula: U=A²T (1) and the value "U" determine the electron-beam pulse energy adequacy and the results of phase transformations.

EFFECT: high accuracy of tuning equipment, which determines parameters of pulses of an electron beam acting on an object.

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Description

The invention relates to mechanical engineering, mainly to thermal and chemical-thermal treatment of metals and alloys in a vacuum chamber by pulsed electron beams, and can be used to monitor the resulting indicators of the processing process.

Attempts to establish monitoring of electron beam technologies began with the control of the electron beam welding process to improve the focusing of the electron beam (1. Copyright certificate No. 1468700, 1989; 2. RF patent No. 2183153, 2002; 3. RF patent No. 2519155, 2006). These methods do not have sufficient speed and are not intended to control the pulsed action on an object with an unfocused beam.

The prior art methods for monitoring phase transitions accompanying thermal exposure, consisting in the fact that the boundaries of phase transitions are determined using an acoustic emission sensor attached to the processed sample (RF patent No. 2433190, publ. 10.11.2011; 2. Vyunenko Yu.N. ., Chernyaeva EV Features of acoustic emission during martensitic transformations in the TiNi alloy. // Bulletin of the Tambov University. Series: Natural and Technical Sciences. Vol. 21, No. 31. 2016. S. 917-921).

The main disadvantage of this analogue is that the acoustic emission sensor is installed in the immediate vicinity of the processed sample. This method is difficult to use in a vacuum chamber when high-energy electron pulses are applied, since powerful electromagnetic interference occurs near the electron gun, which disable both the sensor itself and the equipment located nearby. In addition, the wires connected to the sensor are exposed to heat, pollute the environment and create difficulties for organizing their vacuum input and reliable operation of devices installed in the vacuum chamber.

The closest to the proposed method in terms of the number of common essential features and the technical result achieved - the prototype - is a method for monitoring phase transformations in an irradiated object when its temperature changes, which consists in connecting a waveguide to the workpiece that extends beyond the processing zone to which it is fixed sensor of vibro-acoustic (VA) vibrations, information from which is processed using a computer (Vorontsov V.B., Zhuravlev D.V. Communication of the structure of acoustic e-signals missions during crystallization of A1 with a mechanism for the formation of a solid phase from a melt. // Bulletin of Novgorod State University, No. 67. 2012. S. 8-13).

The main disadvantage of the known technical solution is that it is not intended for operation in a vacuum chamber under conditions of powerful electromagnetic interference. The waveguide, made in the form of a hollow cylindrical rod with a rectilinear axis, is designed to be installed inside its thermocouple in the working area and output the necessary wiring to the recording equipment, as well as for safe contact of the acoustic emission sensor with the high temperature zone. Using the described waveguide, it is impossible to bring the acoustic emission sensor out of the electromagnetic interference zone to a sufficient distance. This is due to the impossibility of bending it, the large diameter and rapid attenuation of high-frequency oscillations (acoustic emission involves recording oscillations in the frequency range from 50 to 1000 kHz) with increasing distance to the vibration source. The experiments showed that for reliable registration of oscillations during the operation of the electron gun, it is necessary to place the recording equipment at 2 meters or more from the processing zone.

The technical problem to be solved by the claimed invention is directed is the reduction of the influence of electromagnetic interference, simplification of the registration of vibration signals during irradiation of parts in a vacuum chamber with an electron gun, simplification of the procedure for comparing the volumes of transformations occurring in a part with a reference value for vibration signal parameters.

The technical result consists in increasing the accuracy of tuning the equipment, which determines the parameters of the pulses of the electron beam acting on the object, and ensuring the performance of electron-beam processing.

The stated technical result is achieved by the fact that in the method for monitoring structural, phase and chemical transformations in the surface layer of the processed objects in vacuum chambers under the influence of electron-beam pulses, which consists in attaching to the processed object a waveguide extending outside the vacuum chamber through a vacuum input, securing to the waveguide of the oscillation sensor and processing information from the latter using a computer, use a flexible wire as the waveguide, as yes The vibration sensor uses an accelerometer with a frequency response covering the frequency range up to 100 kHz, in the process of exposure to an electron beam pulse, the dependences of the current effective values of the signals coming from the accelerometer are recorded on time in two frequency ranges until the signal amplitude drops to the background noise level, as frequency ranges choose the octave band with the highest effective value of the signal amplitude, and the adjacent higher frequency octave, determine the time period “T”, during which the signal amplitude exceeded the background value, the effective value of the signal “A” is calculated over the entire period “T”, the energy “U” of the signal is estimated by the formula: U = A ² T (1), and by the value of “U »They judge the sufficiency of the electron-beam pulse energy and the results of the phase transformations that have occurred.

The essence of the claimed invention is illustrated by the following:

in FIG. 1 is a diagram of an apparatus for recording and analyzing vibroacoustic (VA) signals from an accelerometer arising after an electronic pulse is applied;

in FIG. 2 is an example of a VA signal that occurs after an electronic pulse is applied;

in FIG. 3 - an example of a change in the effective amplitude (averaging time 1 ms) in the frequency range 11-22 kHz with an indication of the time period “T” when the VA signal exceeded the background value, and the effective amplitude “A” for the entire period “T” when the aluminum plate was irradiated ;

in FIG. 4 - an example of a change in the indicator U (formula 1) in the frequency range 11-22 kHz when applying an electronic pulse with a different charging voltage to the aluminum plate.

In accordance with the invention, Fig. 1 shows a circuit that implements the hardware of the proposed method, where a waveguide 2 made of a flexible wire is in contact with the sample being processed 1, the opposite end of which is connected to a receiving plate 3 on which the vibration sensor 4 is mounted, made in the form an accelerometer, the output of which is connected to a preamplifier 5 connected to an analog amplifier 6, the output of which is equipped with an analog-to-digital converter (ADC) 7, the data of which is saved using computer 8 tsya for subsequent processing and outputting the image on a computer monitor 8.

In FIG. Figure 2 shows an example of a VA signal that has arisen as a result of applying an electronic pulse to the sample being processed 1. The example shows a short pulse 9, which has arisen as a result of electromagnetic interference at the moment of applying an electronic pulse, and a 1.2 ms time section corresponding to the delay of the VA signal to an electronic impulse. Over the next 36 ms, the main energy of the VA signal is released.

In FIG. Figure 3 shows an example of a graph of the change in effective amplitude (averaging time 1 ms) in the frequency range 11-22 kHz, indicating the time period “T” when the VA signal exceeded the background value, and the effective amplitude “A” for the entire period “T” when irradiating aluminum plates. According to these data, it is possible using formula (1) to calculate the value of U, proportional to the energy of the VA signal on the period "T".

In FIG. Figure 4 shows an example in the form of a graph of the dependence of the energy parameter “U”, calculated according to formula (1), on the charging voltage of the electron gun during irradiation of aluminum plates. The dots indicate the values of the “U” indicator in each individual experiment. Despite the noticeable scatter, there is a tendency to increase the parameter “U” with increasing charging voltage. The more energy is supplied to the surface of the plate, the greater the volume of aluminum passes into the liquid phase, which returns to solid state upon further cooling. The motion of phase boundaries in the process of changing aggregate states is accompanied by VA signals.

A method for the rapid assessment of the results of electron-beam thermal effects on objects in a vacuum chamber (not shown in Fig.) Is as follows: a waveguide 2 is connected to the object being processed 1, which extends beyond the vacuum chamber through a vacuum inlet, an oscillation sensor 4 is fixed on the waveguide, information from which it is processed using computer 8. As a waveguide 2, a flexible wire is used, an accelerometer with a frequency response spanning a clear range up to 100 kHz, in the process of performing a technological operation, the dependences of the current effective values of the signals coming from the accelerometer are recorded on time in two frequency ranges from the moment the electron-beam pulse is applied until the signal amplitude drops to the background noise level, and the frequency ranges are selected the octave band, where the largest effective values of the signal amplitude are present, and the adjacent higher octave, determine the time period “T” during which the signal amplitude and higher than the background value, calculating the effective value of "A" signal on all the period "T" evaluated energy "and" signal from the formula: U = A ² T, and the value «U» judged energy sufficiency of electron beam pulse and the results of the phase transformations.

The waveguide length must be sufficient to provide an acceptable level of electromagnetic interference. If necessary, the recording equipment can be placed behind the protective screen, which reduces the electromagnetic effect on the equipment. As a waveguide, for example, a copper wire with a diameter of 2-3 mm can be used, which is easy to seal when it is removed from the vacuum chamber and put behind a protective screen where the recording equipment is installed.

Practice has shown that with increasing waveguide length, relatively high-frequency oscillations decay faster. This is due to the fact that the logarithmic decrement of vibrations, which displays the rate of attenuation of free vibrations in one period, for most structural materials is practically independent of the frequency of these vibrations. But at the same propagation velocity of longitudinal waves during the movement of the vibrational energy from the source to the opposite end of the waveguide, the high-frequency components will perform as many times as many oscillation cycles, how many times their frequency is higher. If in the interval of 1.2 ms the component of oscillations at a frequency of 500 kHz performs 600 cycles of oscillation, then the component at 50 kHz will perform only 60 cycles. If the share of losses in each cycle is the same, then it is obvious that more energy will be stored at a lower frequency. For example, with the same initial oscillation amplitude at 500 kHz and 50 kHz and with the same ratio q = a _{i + 1} / a _i (the ratio of amplitudes at the end of a single cycle to the amplitude at the beginning of the cycle), the ratio of amplitudes at the opposite end of the waveguide will be q ⁵⁴⁰ . This means that at q = 0.9 on the receiving plate, the amplitude of the high-frequency component (500 kHz) will relate to the amplitude of the low-frequency component (50 kHz), as 10 ^-25 . Practice has also shown that at a large distance from the source of perturbations, the high-frequency components disappear or weaken in the spectrum of vibrations. The experiments also showed that if parallel recording of vibrations in the ranges of low (from 4 to 20 kHz) and high (up to 1 MHz) frequencies then builds their envelopes (the entire record is divided into small sections of time, for each section the effective value is determined , the set of effective values forms the envelope), then they turn out to be largely similar. This means that when vibrations are excited by sets of very short pulses, they form pulses at both high and low frequencies. Since at a long waveguide, vibrations at high frequencies cannot be distinguished from the background of interference, the control of the relatively low-frequency components of vibrations can be carried out by an accelerometer. Most industrial accelerometers have a resonant frequency of not more than 100 kHz (piezoelectric accelerometers from Bruhl and Kj Кr. Http://asm-tm.ru/wp-content/uploads/2014/08/8309.pdf). Their linear characteristic, which can be used for metrological purposes, is much narrower. For monitoring purposes, you can use the entire frequency range, but then it is permissible to give an estimate not in units of acceleration, but in increments relative to the previous measurement or reference value. These considerations and experimental data showed that it is enough to use an accelerometer with a frequency response of up to 100 kHz.

Example:

For the case of a streamlined process of electron beam processing, when a detailed analysis of the reaction occurring in the preform after its irradiation is not required, you can use a simple criterion for assessing the volume of transformations in the preform material. The present invention proposed a criterion that estimates the value of "U" according to the formula (1), which is proportional to the energy of the VA signal in the selected octave band during the time "T", during which the signal amplitude exceeded the background value. The amount of this energy indicates the volume of transformations in the workpiece material. In FIG. Figure 4 shows a graph of the dependence of the energy parameter “U” for the octave band 22-44 kHz, calculated by formula (1), on the charging voltage of the electron gun when irradiating aluminum plates. The dots indicate the values of the “U” indicator in each individual experiment. In this case, under the influence of the supplied energy, processes of melting, evaporation, cooling, and crystallization took place in the material. The presented averaged relationship in FIG. 4 after 17 kV is close to linear. However, when irradiating, for example, thin films, the amount of transformable material can be limited. In this case, a relationship similar to FIG. 4 will have a saturation level by which a rational charging voltage value can be determined. When the electron gun operates in the mode of supplying pulses in the form of a beam of streams from several electrodes, a significant scatter in the results is possible. Using the proposed method, you can quickly evaluate the integral result and make a decision on the repetition of the pulsed impact on the object.

The use of an additional higher octave is justified by the fact that the energy indices of a VA signal in a higher frequency octave are the higher, the more relatively short pulses are observed in the processes observed in the object. Such impulses usually prevail in the initial moments after electronic exposure. Their lack leads to a sluggish course of further transformations. For example, when irradiating aluminum plates at a charging voltage of 22 and 16 kV, the ratio between the “U” values for the octave 22-44 kHz was 10, and for the octave 11-22 kHz this ratio was 17. This suggests that at the supply stage of the working pulse, the melting and evaporation processes were hardly noticeable, which led to small volumes of the past transformations.

Based on the foregoing, we can conclude that the task is to reduce the influence of electromagnetic interference, simplify the procedure for recording vibration signals when parts are irradiated in a vacuum chamber using an electron gun, simplify the procedure for comparing the volumes of transformations occurring in a part with a reference value for vibration signal parameters - solved, and the claimed technical result is an increase in the accuracy of tuning the equipment that determines the parameters of the pulses of the electron beam acting on the object, and ensure Cross-sectional performance of electron-beam processing - achieved.

The analysis of the claimed technical solution for compliance with the conditions of patentability showed that the characteristics indicated in the independent claim are interrelated with each other with the formation of a stable set of necessary attributes unknown at the priority date from the prior art sufficient to obtain the required synergistic (over-total) technical result.

Thus, the above information indicates the fulfillment of the following set of conditions when using the claimed technical solution:

- an object embodying the claimed technical solution, when implemented, relates to electrophysical processing methods, in particular to electron beam processing in vacuum chambers;

- for the claimed object as described in the independent clause of the formula below, the possibility of its implementation using the means and methods described above and / or known from the prior art on the priority date is confirmed;

- the object embodying the claimed technical solution, when implemented, is able to ensure the achievement of the technical result perceived by the applicant.

Therefore, the claimed subject matter meets the patentability criteria of “novelty”, “inventive step” and “industrial applicability” under applicable law.

Claims (1)

A method for recording phase transformations in the surface layer of an object processed by electron-beam pulses in a vacuum chamber, including attaching a waveguide to the object being processed, outputting it outside the vacuum chamber through a vacuum input, attaching an oscillation sensor to the waveguide and processing the received information by a computer, characterized in that a flexible wire is used as a waveguide, and an accelerometer with a frequency response covering frequency range up to 100 kHz, while in the process of exposure to an electron beam pulse, the dependences of the current values of the signals coming from the accelerometer are recorded on time in two frequency ranges until the signal amplitude drops to the level of background noise, and the octave band with the largest the effective value of the signal amplitude and the adjacent higher-frequency octave, while determining the time period "T" during which the signal amplitude exceeds the background value, you calculate the effective value of the signal “A” over the entire period “T” and estimate the energy “U” of the signal according to the formula U = A ² T, the value of “U” of which judges the sufficiency of the energy of the electron beam pulse for phase transformations in the surface layer of the object.

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