RU2545348C2 - Method of laser-ultrasound quality control of soldered joints - Google Patents

Abstract

FIELD: instrumentation.

SUBSTANCE: scope of application: for laser-ultrasound quality control of the soldered joints. The essence of the invention is that using the pulse laser the optical pulses are generated, they are converted in the acoustic signal - series of ultrasound pulses creating the sounding ultrasound beam, the studied object is subjected to this beam action, the piezoreceiver receives the signals reflected from the studied object, they are analyzed, and based on the analysis results the object internal defects are estimated, at that the specified acoustic signal is formed as aperiodic sequence of ultrasound pulses with width from 5 to 20 ns with creation of the sounding ultrasound beam with diameter from 0.6 to 1.0 mm.

EFFECT: possibility of quality control of the soldered joints of thin cell double-wall steelworks.

4 dwg

Description

The invention relates to non-destructive testing methods and can be used to control soldered joints in thin cellular double-walled metal structures, for example, bodies and nozzles of liquid rocket engines (LRE).

The relevance of quality control of soldered joints in the designs of rocket engines and their nozzles is caused by an increasing increase in the specific impulse of the engines and, consequently, the working pressure in their interwall space, which increases the quality requirements of soldered joints. At the same time, the complexity of the control is determined by the specifics of the design, namely the fact that the connection of the outer and inner walls of the buildings is carried out “inside” the structure along the stiffeners.

A known method of acoustic quality control of soldered joints in one-sided honeycomb structures, presented in the copyright certificate [1] - SU 792136 A1, G01N 29/04, 12/30/1980, which consists in the fact that using the emitting piezoelectric element, ultrasonic vibrations are excited from the open part of the cells take reflected vibrations, analyze them and, based on the results of the analysis, judge the quality of the soldered joints of the structural elements of the cells, while the cells are completely filled with a liquid that has wettability with respect to the wall material to honeycombs. A significant drawback of this method is the need to fill the cells with liquid, which does not allow it to be used to control double-walled structures.

A known method for the acoustic quality control of soldered joints in one-sided honeycomb structures is presented in the patent [2] - RU 2069362 C1, G01N 29/16, 11/20/1996, in which ultrasonic vibrations in a controlled segment of the structure are excited from the open sections of the cells by means of a piezoelectric probe. take reflected vibrations, analyze them and judge the quality of the soldered joint based on the results of the analysis.

мкс, что соответствует продольному разрешению $$\Delta l=\left(0,6-3,0\right)$$

мм, диаметр зондирующего ультразвукового луча составляет более 4 мм, а глубина «мертвой зоны» составляет не менее (0,8 - 1,0) мм, что не позволяет в ряде случаев осуществлять точный контроль качества внутренних соединений конструкции.The disadvantage of the method presented in [2], as well as other known methods of acoustic (ultrasonic) control, based on the use of emitting piezoelectric elements, see, for example, [3] - SU 808930 A1, G01N 29/00, 02/28/1981; [4] SU 1345110 A1, G01N 29/04, 10/15/1987; [5] - RU 2047171 C1, G01N 29/20, 10.27.1995; [6] - RU 2196982 C2, G01N 29/00, 03.20.2001, is a low sensitivity and resolution due to the piezoelectric method of excitation of elastic vibrations. This is explained by the fact that the piezoelectric method of excitation of elastic vibrations has limited possibilities for the formation of sounding signals, in particular, the duration of the ultrasound pulse generated in this way is of the order of $$\Delta t=\left(0,\mathrm{one}-0,5\right)$$

μs, which corresponds to the longitudinal resolution $$\Delta l=\left(0,6-3,0\right)$$

mm, the diameter of the probe ultrasound beam is more than 4 mm, and the depth of the "dead zone" is at least (0.8 - 1.0) mm, which in some cases does not allow for accurate quality control of the internal connections of the structure.

Laser-ultrasonic control methods have great potential for generating sounding signals, for example, the laser-acoustic control method for solid materials selected as a prototype, presented in patent [7] - RU 2232983 C2, G01N 29/04, 07/20/2004.

The prototype method is as follows. Optical pulses are generated using a pulsed laser, converted into an acoustic signal - a periodic sequence of ultrasonic pulses forming a probing ultrasonic beam, the object under study is irradiated with this beam, the signals reflected from the object under study are received by the piezoelectric receiver, analyzed and the internal defects of the object are judged by the results of the analysis. In this case, a two-way distributed optical-acoustic transducer is used to generate probing ultrasonic pulses, and the reflected signals are received by a grating from local piezoelectric receivers located between the optical-acoustic transducer and the object under study.

The prototype method solves the general problem of creating a reliable way to control the mechanical (structural) properties of an object with a one-way access to it, which has high resolution and high sensitivity.

However, the prototype method does not provide a specific solution for the considered particular case of control of soldered joints in thin cellular double-walled metal structures, such as shells and nozzles of rocket engines.

The technical result to which the claimed invention is directed is to develop a method of laser-ultrasonic quality control of soldered joints for the case under consideration of thin cellular double-walled metal structures such as casings and LPRE nozzles, which makes it possible to identify such defects of soldered joints as non-solders and (or) non-solders. At the same time, the minimum size of the area that is not junctioning and (or) nepaya, which must be identified, is 1 mm ² . The disclosure of non-padded and non-padded ones can be of the order of several microns for non-padded, and several tens of microns for non-padded

The essence of the proposed method of laser-ultrasonic quality control of soldered joints is as follows. Optical pulses are generated using a pulsed laser, converted into an acoustic signal - a sequence of ultrasonic pulses forming a probing ultrasonic beam, the object under study is irradiated with this beam, the signals reflected from the object under investigation are received by the piezoelectric receiver, they are analyzed and the internal defects of the object are judged by the results of the analysis. Moreover, in contrast to the prototype, the specified acoustic signal is formed in the form of an aperiodic sequence of ultrasonic pulses with a duration of 5 to 20 ns with the formation of a probe ultrasound beam with a diameter in the range from 0.6 to 1.0 mm.

The invention and the possibility of its implementation are illustrated by the illustrative materials presented in FIG. 1 - 4, where:

in FIG. 1 is a structural diagram explaining the control of the claimed method;

in FIG. 2 is an example of an optical-acoustic image of a defect-free portion of a rocket engine nozzle;

in FIG. 3 is an example of an optical-acoustic image of a defective portion of a rocket engine nozzle;

in FIG. 4 is an example of a defective area after hydraulic testing and opening the inner wall of the LPRE nozzle.

The quality control of the soldered joints of the LRE when using the proposed method consists in finding nonspecial and non-solder joints at the junction points. The control circuit shown in FIG. 1, where the laser-ultrasonic inspection sensor 1 is docked to the inner wall 2 of the structure, the outer wall 3 of which is connected by soldering 4 to the vertices of the ribs of the inner wall 2. The laser-ultrasonic inspection sensor 1 is connected by a corresponding communication line to peripheral equipment, for example, visualization means (in FIG. . 1 not shown).

As the sensor 1 of laser-ultrasonic inspection, a laser-ultrasonic flaw detector can be used, similar, for example, to a laser-ultrasonic flaw detector, presented in the patent [8] - RU 2381496 C1, G01N 29/04, 02/10/2010.

In the process of quality control of the soldered joints, optical pulses are generated using a pulsed laser, which is part of the sensor 1 (not shown in Fig. 1), which are then converted into an acoustic signal — an aperiodic sequence of ultrasonic pulses with a duration of 5–20 ns forming a probe ultrasound beam diameter 0.6 ÷ 1.0 mm. The short duration (5 ÷ 20 ns) of ultrasonic pulses gives the effect of increasing the longitudinal spatial resolution of the control, reaching values of 5 ÷ 10 μm. The small diameter (0.6 ÷ 1.0 mm) of the probe beam gives the effect of increasing the sensitivity of control over the effective area of heterogeneity. The aperiodicity of ultrasonic pulses ensures the practical absence of a “dead zone” and the possibility of determining the acoustic impedance of an inhomogeneity.

The indicated probing ultrasonic beam is irradiated with the investigated section of the structure adjacent to the sensor 1. Inside the studied section, acoustic signals are reflected from the inner wall 2, from the cavity of the inner wall 2, from the top of the rib of the inner wall 2 and from the outer wall 3.

The reflected acoustic signals are received by a piezoelectric receiver, which is part of the sensor 1 (not shown in Fig. 1). The piezoelectric receiver generates electrical signals representing an optical-acoustic image of the investigated section of the structure.

The specified optical-acoustic image of the investigated section of the structure is visualized using appropriate visualization tools. This image is further analyzed and judged by the results of the analysis of the presence or absence of internal structural defects manifesting in the joints and (or) non-solders at the joints.

In FIG. Figure 2 shows a real-life example of an optical-acoustic image of a defect-free portion of an LRE nozzle. This image is characterized by the fact that in the regular zones there are no signals corresponding to reflections from the soldered joint. This indicates the high quality of the soldered joint, in which there are no joints.

In FIG. Figure 3 shows a real-life example of an optical-acoustic image of a defective section of a LRE nozzle. This image is characterized by the fact that it contains reflections from the vertices of the edges. This indicates the reflection of the acoustic signal from the free edge of the rib of the inner wall of the nozzle, which characterizes the presence of junction or discontinuity.

To prove the validity of the conclusions about the quality of the soldered joints made according to the results of the proposed method, hydraulic tests of a sample of the LRE nozzle were carried out, the purpose of which was to confirm the conformity of the defective sections identified using the claimed method with the real defective sections of the LRE nozzle detected as a result of hydraulic tests. To do this, after laser-ultrasonic testing, areas were identified with the alleged non-junction or discontinuity for hydraulic testing.

For the correct interpretation of the results of visual inspection of the sites of alleged non-jams opened after hydrotesting, it was necessary to paint the surfaces of the non-jars (discontinuities) formed during preliminary tests. To this end, penetrating paint used in color control was poured into the grooves of the nozzle cut-out, used for color control, followed by drying and fixing by holding in an oven.

Further, the following operations were carried out at the appropriate stand: pressure loading, five-minute exposure, pressure relief and external inspection of the nozzle cut with the control of the alleged places of the joints. The control was carried out by measuring the expansion of the bulges.

This operation was repeated with a stepwise increase in pressure by 100 kgf / cm ² until the nozzle notch was destroyed when the maximum pressure was reached. At the same time, the nozzle notch in the form of a large bulge and a rupture of the inner wall in the selected area of the alleged non-junction occurred.

After hydrotesting, the destroyed site was opened. The exposed section was examined using an MBS-2 microscope. A view of the exposed portion is shown in FIG. four.

When analyzing the destroyed area, the following was established. Between the grooves of the overflow from the high pressure side there were destruction of the soldered joint along four ribs formed during autonomous motor tests, as well as destruction of the soldered joint along seven ribs formed during hydrotesting, which confirmed the correct conclusions about the presence of defects in soldered joints made according to the results of the claimed way

Thus, the above shows that the claimed invention is feasible and ensures the achievement of the technical result, which consists in the development of a method of laser-ultrasonic quality control of soldered joints for thin cellular double-walled metal structures such as casings and LPRE nozzles.

Information sources

1. SU 792136 A1, G01N 29/04, publ. 12/30/1980.

2. RU 2069362 C1, G01N 29/16, publ. 11/20/1996.

3. SU 808930 A1, G01N 29/00, publ. 02/28/1981.

4 SU 1345110 A1, G01N 29/04, publ. 10/15/1987.

5. RU 2047171 C1, G01N 29/20, publ. 10/27/1995.

6. RU 2196982 C2, G01N 29/00, publ. 03/20/2001.

7. RU 2232983 C2, G01N 29/04, publ. 07/20/2004.

8. RU 2381496 C1, G01N 29/04, publ. 02/10/2010.

Claims (1)

The method of laser-ultrasonic quality control of soldered joints, which consists in generating optical pulses using a pulsed laser, converting them into an acoustic signal - a sequence of ultrasonic pulses forming a probing ultrasonic beam, irradiate the object under investigation with this beam, and receive signals reflected from the object under study by the piezoelectric receiver analyze them and according to the results of the analysis judge about the internal defects of the object, characterized in that the specified acoustic signal is formed in the form aperiodic sequence of ultrasonic pulses lasting from 5 to 20 ns with the formation of a probe ultrasound beam with a diameter in the range from 0.6 to 1.0 mm.

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