A method, device and medium for calibrating stress ultrasonic detection under protective paint layer

Abstract

The application discloses a kind of protective paint layer stress ultrasonic detection calibration method, the method includes the paint layer acoustic velocity of the ultrasonic longitudinal wave obtained by measurement in the paint layer thickness of the detected piece, in acoustic wedge block wedge block acoustic velocity, and the critical angle when ultrasonic longitudinal wave is obliquely incident from paint layer to the inside of the detected piece, the installation angle of stress detector on acoustic wedge block is calculated;According to the different paint layer thickness of the surface of the detected piece and the propagation acoustic time of the detected piece under different paint layer thickness of ultrasonic longitudinal wave, determine the paint layer influence coefficient;According to the compensation parameter formed by paint layer influence coefficient, the paint layer thickness of the detected piece and the paintless thickness of zero stress test piece, by stress detector with compensation parameter under the installation angle of acoustic wedge block, zero stress test piece and the detected piece are detected respectively, and the residual stress of the detected piece is obtained.The application solves the problem that the existing technology is extremely difficult to nondestructive testing of residual stress of steel structure under the protection of paint layer.

Description

Technical Field

[0001] This invention relates to the field of stress ultrasonic nondestructive testing technology, specifically to a method, apparatus, and medium for stress ultrasonic testing calibration under a protective paint layer. Background Technology

[0002] Currently, bridge deck stiffeners come in a wide variety of forms, with orthotropic plates, primarily U-ribs, being widely used in bridge engineering design. The main connection method between the bridge deck and the U-rib is welding. Under the high temperature of the welding heat source, the structure undergoes significant plastic deformation. After the weld cools, the structure cannot fully recover its original shape due to plastic deformation, resulting in residual stress. This residual stress has many adverse effects on the structure's strength, stability, and fatigue. Non-destructive testing and assessment of residual stress has become an urgent problem to be solved; however, non-destructive testing of residual stress in steel structures under paint protection is extremely difficult. Summary of the Invention

[0003] In view of this, the main objective of this application is to provide a method for ultrasonic testing and calibration of stress under protective paint layers, which helps to solve the problem that the paint layer on the steel surface makes it difficult to conduct non-destructive testing of residual stress inside the steel structure.

[0004] This application provides a method for ultrasonic testing and calibration of stress under a protective paint layer, comprising:

[0005] Based on the measured ultrasonic longitudinal wave velocity in the paint layer at the thickness of the paint layer of the test piece, the wedge velocity in the acoustic wedge, and the critical angle when the ultrasonic longitudinal wave obliquely enters the interior of the test piece from the paint layer, the installation angle of the stress detector on the acoustic wedge is calculated.

[0006] The paint layer influence coefficient is determined based on the different paint layer thicknesses on the surface of the inspected part and the propagation time of ultrasonic longitudinal waves on the inspected part under different paint layer thicknesses.

[0007] Based on the compensation parameters formed by the paint layer influence coefficient, the unpainted layer thickness of the zero-stress specimen, and the paint layer thickness of the test piece, the zero-stress specimen and the test piece are tested separately using a stress detector with compensation parameters at the installation angle of the acoustic wedge, and the residual stress of the test piece is obtained.

[0008] As shown above, the installation angle of the stress detector on the acoustic wedge is calculated to ensure that the incident angle of the ultrasonic longitudinal wave excited by the stress detector is just right to generate a critical refracted longitudinal wave inside the steel structure, ensuring that the ultrasonic longitudinal wave can propagate on the surface of the steel structure. To detect the residual stress in the steel structure, it is necessary to compensate for the propagation time of the ultrasonic longitudinal wave in the paint layer. By studying the influence of different paint layer thicknesses on the propagation time of the ultrasonic longitudinal wave, the coefficient of the paint layer's influence on the propagation time is obtained. According to the paint layer thickness on the surface of the tested part, the paint layer influence coefficient is input into the stress detector. The stress detector is then used to detect the residual stress inside the steel structure, which can not only obtain the true residual stress value of the steel structure under the protective paint, but also eliminate or reduce the error caused by zero stress calibration.

[0009] Optionally, based on the measured ultrasonic longitudinal wave velocity in the paint layer at the thickness of the paint layer on the test piece, the wedge velocity in the acoustic wedge, and the critical angle at which the ultrasonic longitudinal wave obliquely incident from the paint layer into the interior of the test piece, the installation angle of the stress detector on the acoustic wedge is calculated, including: measuring the ultrasonic longitudinal wave excited by the stress detector in the paint layer at the thickness of the paint layer on the test piece; calculating the incident angle of the ultrasonic longitudinal wave obliquely incident on the paint layer of the test piece surface using the law of refraction based on the measured paint layer velocity, the pre-observed wedge velocity, and the pre-observed critical angle at which a critical refracted longitudinal wave can be generated inside the test piece; and setting the installation angle of the stress detector on the acoustic wedge based on the incident angle.

[0010] As described above, the ultrasonic longitudinal wave is incident from the acoustic wedge into the paint layer, resulting in a first refraction. It is then incident from the paint layer into the steel structure, resulting in a second refraction. To ensure that the ultrasonic longitudinal wave can propagate inside the steel structure, the sound velocity in the paint layer needs to be measured, and the incident angle at which the critical refraction longitudinal wave can be generated inside the steel structure needs to be calculated. Based on the calculated incident angle, the tilt angles on both sides of the acoustic wedge are set, and the stress detector is installed on both sides of the acoustic wedge to ensure that the ultrasonic longitudinal wave excited by the transmitting transducer is obliquely incident from the acoustic wedge into the steel structure with the paint layer at a certain angle and can be received by the receiving transducer.

[0011] Optionally, the paint layer influence coefficient is determined based on the different paint layer thicknesses on the surface of the test piece and the propagation time of the ultrasonic longitudinal wave on the test piece under different paint layer thicknesses. This includes: detecting the propagation time of the ultrasonic longitudinal wave on the test piece under different paint layer thicknesses; and fitting the different paint layer thicknesses and their corresponding propagation times using the least squares method to obtain the paint layer influence coefficient of different paint layer thicknesses on the propagation time of the ultrasonic longitudinal wave.

[0012] Therefore, to detect residual stress inside a steel structure, it is necessary to compensate for the propagation time of ultrasonic longitudinal waves within the paint layer. Through experiments, the influence of paint layers of different thicknesses on the propagation time of ultrasonic longitudinal waves is first studied, thereby obtaining the coefficient of paint layer influence on propagation time, i.e., the paint layer influence coefficient. By using the paint layer influence coefficient, not only can the accuracy of stress detection under the paint layer be improved, but also the error caused by zero-stress calibration can be eliminated or reduced.

[0013] Optionally, based on the compensation parameters formed by the paint layer influence coefficient, the unpainted layer thickness of the zero-stress specimen, and the paint layer thickness of the tested specimen, the zero-stress specimen and the tested specimen are tested separately using a stress detector equipped with compensation parameters at the installation angle of the acoustic wedge, to obtain the residual stress of the tested specimen, including:

[0014] Based on the compensation parameters formed by the paint layer influence coefficient, the unpainted layer thickness of the zero-stress specimen, and the paint layer thickness of the tested specimen, the zero-stress specimen is tested by a stress detector with compensation parameters at the installation angle of the acoustic wedge, and the zero-stress acoustic time and stress detection coefficient are obtained.

[0015] Based on the compensation parameters formed by the paint layer influence coefficient, the unpainted layer thickness of the zero-stress specimen, and the paint layer thickness of the test piece, the test piece is tested by a stress detector with compensation parameters at the installation angle of the acoustic wedge block to obtain the stress acoustic time of the test piece.

[0016] The acoustic time difference is obtained based on the zero-stress acoustic time and the stress acoustic time of the inspected part;

[0017] The residual stress of the inspected part is obtained based on the compensation coefficient, acoustic time difference, and stress detection coefficient.

[0018] Therefore, by using a stress testing instrument that has been compensated for the paint layer, the pre-performed zero-stress calibration and stress detection coefficient calibration processes are more accurate, eliminating or reducing errors caused by the calibration process. Under the condition that the distance between the transmitting and receiving transducers in the stress testing instrument is fixed, the propagation time of the ultrasonic longitudinal wave corresponding to zero stress and the propagation time of the ultrasonic longitudinal wave corresponding to the stress in the tested part are measured. Based on the time difference between the two, the residual stress in the tested part is calculated according to the formula in the standard GB / T 32073-2015 for ultrasonic testing of residual stress.

[0019] Optionally, based on the compensation parameters formed by the paint layer influence coefficient, the unpainted layer thickness of the zero-stress specimen, and the paint layer thickness of the tested specimen, the zero-stress specimen is tested using a stress detector equipped with compensation parameters at the installation angle of the acoustic wedge to obtain the zero-stress acoustic time and stress detection coefficient, and the test also includes:

[0020] The paint layer influence coefficient and the unpainted layer thickness form the first compensation parameter, which is input into the stress detector. The compensation parameter includes the first compensation parameter.

[0021] Zero-stress test specimens are calibrated using a stress detector with a first compensation parameter at the installation angle of the acoustic wedge to obtain the zero-stress acoustic time.

[0022] The stress detection coefficient is obtained by performing a tensile test on a zero-stress specimen using a stress detector with a first compensation parameter at the installation angle of the acoustic wedge.

[0023] As described above, by using a stress detector with a first compensation parameter to perform zero-stress calibration and tensile tests on zero-stress specimens, the stress detector can more accurately detect residual stress.

[0024] Optionally, to obtain the zero-stress acoustic time by performing zero-stress calibration on the zero-stress specimen using a stress detector with a first compensation parameter at the installation angle of the acoustic wedge, the method further includes:

[0025] Adjust and set the stress detector with the first compensation parameter, and use the acoustic wedge block with the set installation angle to firmly couple the probe of the stress detector with the first compensation parameter into the calibration area of ​​the zero-stress specimen.

[0026] Zero-stress specimens are calibrated to zero stress, and the propagation time of ultrasonic critical refraction longitudinal waves corresponding to zero stress is recorded by a stress detector with the first compensation parameter to obtain the zero-stress acoustic time.

[0027] As described above, the size of the calibration area for the zero-stress specimen is related to the probe size and ultrasonic frequency. The length L of the detection area is the critical refraction longitudinal wave propagation distance, typically 5mm to 100mm. After adjusting the stress detector to normal operating conditions, set the detection parameters such as detection frequency, filter bandwidth, ultrasonic excitation voltage, ultrasonic receiving gain, probe spacing, and position according to the determined calibration area. After adjusting and setting the instrument, securely couple the probe within the calibration area of ​​the zero-stress specimen and perform zero-stress calibration. With the probe securely coupled within the calibration area of ​​the zero-stress specimen, record the ultrasonic critical refraction longitudinal wave propagation time corresponding to the zero stress measured by the stress detector. Using an instrument probe calibrated with the paint layer influence coefficient for zero-stress calibration can eliminate or reduce the influence of the paint layer, resulting in more accurate test results.

[0028] Optionally, the stress detection coefficient is obtained by performing a tensile test on the zero-stress specimen using a stress detector with a first compensation parameter at the installation angle of the acoustic wedge, and the method further includes:

[0029] Adjust and set the stress detector with the first compensation parameter, and use the acoustic wedge block with the set installation angle to firmly couple the probe of the stress detector with the first compensation parameter into the calibration area of ​​the zero-stress specimen.

[0030] Tensile tests were conducted on the zero-stress specimens to obtain the zero-stress acoustic time difference measured by a stress detector with the first compensation parameter and the tensile stress change measured by the tensile testing equipment.

[0031] The stress detection coefficient is obtained by linearly fitting the zero-stress acoustic time difference and tensile stress change.

[0032] As described above, within the elastic range of the material, record the zero-stress acoustic time difference of the stress detector and the tensile stress output of the tensile testing equipment. There should be no fewer than 10 measurement points and no fewer than 5 repeated tensile tests. Take the average value and plot the coordinate graph of the tensile stress value and the zero-stress acoustic time difference. Then, perform linear fitting on the data and obtain the reciprocal of the slope of the straight line, which is the stress detection coefficient.

[0033] Optionally, based on the compensation parameters formed by the paint layer influence coefficient, the unpainted layer thickness of the zero-stress specimen, and the paint layer thickness of the tested specimen, the tested specimen is tested using a stress detector equipped with compensation parameters at the installation angle of the acoustic wedge block to obtain the stress acoustic time of the tested specimen, which also includes:

[0034] The second compensation parameter, formed by the paint layer influence coefficient and the paint layer thickness of the inspected part, is input into the stress testing instrument. The compensation parameter includes the second compensation parameter.

[0035] By using a stress detector equipped with a second compensation parameter at the installation angle of the acoustic wedge, the propagation time of the ultrasonic longitudinal wave in the test piece is detected, and the stress acoustic time of the test piece is obtained.

[0036] As described above, after the thickness of the paint layer on the surface of the inspected part is detected by the instrument, the second compensation parameter formed by the paint layer influence coefficient and the paint layer thickness of the inspected part is input into the stress detector. The stress detector calibrated by the second compensation parameter is used to perform stress detection on the inspected part. The residual stress obtained is more realistic, and the influence of the paint layer on the sound time is also eliminated.

[0037] This application also provides an ultrasonic testing and calibration device for stress under protective paint layers, which includes:

[0038] The acoustic wedge setting module is used to calculate the installation angle of the stress detector on the acoustic wedge based on the measured ultrasonic longitudinal wave velocity in the paint layer at the thickness of the paint layer of the test piece, the wedge velocity in the acoustic wedge, and the critical angle when the ultrasonic longitudinal wave obliquely enters the interior of the test piece from the paint layer.

[0039] The compensation determination module is used to determine the paint layer influence coefficient based on the different paint layer thicknesses set on the surface of the inspected part and the propagation sound of ultrasonic longitudinal waves on the inspected part under different paint layer thicknesses.

[0040] The stress detection and analysis module is used to detect the residual stress of the test piece by using a stress detector equipped with compensation parameters at the installation angle of the acoustic wedge block, based on the paint layer influence coefficient, the unpainted layer thickness of the zero-stress specimen, and the paint layer thickness of the test piece.

[0041] As described above, the acoustic wedge setting module prevents ultrasonic longitudinal waves from propagating in the paint layer, ensuring that the stress detector can generate critical refracted longitudinal waves inside the steel structure, enabling the detection of residual stress within the steel structure. The compensation determination module compensates for the propagation time of ultrasonic longitudinal waves within the paint layer, making up for the influence of paint layer thickness on the time delay of the acoustoelastic method, and improving the detection accuracy of residual stress under the protective paint layer. The stress detection analysis module adds a paint layer influence coefficient, eliminating the influence of the paint layer on the sound wave propagation time for the detection of residual stress inside the steel structure.

[0042] This application also provides a computer-readable storage medium storing computer instructions, characterized in that the computer instructions are operated to perform the ultrasonic testing and calibration method for stress under protective coating as described in any of the preceding claims.

[0043] In summary, the ultrasonic testing and calibration method, apparatus, and medium for stress under protective paint layers provided in this application calculate the installation angle of the stress detector on the acoustic wedge to ensure that the incident angle of the ultrasonic longitudinal wave excited by the stress detector is just right to generate a critically refracted longitudinal wave inside the steel structure, thus ensuring that the ultrasonic longitudinal wave can propagate on the surface of the steel structure. To detect residual stress in the steel structure, it is necessary to compensate for the propagation time of the ultrasonic longitudinal wave within the paint layer. By studying the influence of different paint layer thicknesses on the propagation time of the ultrasonic longitudinal wave, a coefficient of paint layer influence on propagation time is obtained. Based on the paint layer thickness on the surface of the tested part, the paint layer influence coefficient is input into the stress detector. Using this stress detector to detect residual stress inside the steel structure, the true residual stress value of the steel structure under the protective paint can be obtained, and the error caused by zero-stress calibration can be eliminated or reduced. Attached Figure Description

[0044] The various technical features of the present invention and their relationships will be further explained below with reference to the accompanying drawings. The drawings are exemplary; some technical features are not shown to scale, and some drawings may omit technical features commonly used in the art to which this invention pertains that are not essential for understanding and implementing the invention, or may additionally show technical features that are not essential for understanding and implementing the invention. In other words, the combination of various technical features shown in the drawings is not intended to limit the invention. Furthermore, throughout this invention, the same reference numerals refer to the same things. Specific descriptions of the drawings are as follows:

[0045] Figure 1This is a flowchart of an ultrasonic testing and calibration method for stress under a protective paint layer according to this application;

[0046] Figure 2 This is a schematic diagram illustrating the method for setting the installation angle of the stress detector on the acoustic wedge block in this application;

[0047] Figure 3 This is an experimental schematic diagram for calculating the paint layer influence coefficient in this application;

[0048] Figure 4 This is a schematic diagram of curve fitting in this application;

[0049] Figure 5 This is a block diagram of an ultrasonic testing and calibration device for stress under a protective paint layer, as described in this application.

[0050] Explanation of icon numbers

[0051] 21.1 - Transmitting transducer probe in stress testing instrument; 21.2 - Receiving transducer probe in stress testing instrument; 22 - Acoustic wedge; 23 - Paint layer; 24 - Steel plate.

[0052] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0053] The preferred embodiments of this application will now be described in detail with reference to the accompanying drawings, so that the advantages and features of this application can be more easily understood by those skilled in the art, thereby providing a clearer and more definite definition of the scope of protection of this application.

[0054] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes said element.

[0055] The technical solutions of this application and how they solve the aforementioned technical problems will be described in detail below with specific embodiments. The specific embodiments described below can be combined with each other to form new embodiments. The same or similar ideas or processes described in one embodiment may not be repeated in other embodiments. The embodiments of this application will now be described with reference to the accompanying drawings.

[0056] [Example of Ultrasonic Testing and Calibration Method for Stress Under Protective Coating]

[0057] Figure 1 This is a flowchart of the ultrasonic testing and calibration method for the protective coating layer stress according to this application. Figure 1 As shown, the ultrasonic testing and calibration method for stress under protective paint layers includes:

[0058] S101: Based on the measured ultrasonic longitudinal wave velocity in the paint layer at the thickness of the paint layer of the test piece, the wedge velocity in the acoustic wedge, and the critical angle when the ultrasonic longitudinal wave obliquely enters the interior of the test piece from the paint layer, the installation angle of the stress detector on the acoustic wedge is calculated.

[0059] S102: Determine the paint layer influence coefficient based on the different paint layer thicknesses set on the surface of the inspected part and the propagation sound of ultrasonic longitudinal waves on the inspected part under different paint layer thicknesses.

[0060] S103: Based on the compensation parameters formed by the paint layer influence coefficient, the unpainted layer thickness of the zero-stress specimen, and the paint layer thickness of the test piece, the zero-stress specimen and the test piece are tested separately using a stress detector with compensation parameters at the installation angle of the acoustic wedge block to obtain the residual stress of the test piece.

[0061] Specifically, the installation angle of the stress detector on the acoustic wedge is calculated to ensure that the incident angle of the ultrasonic longitudinal wave excited by the stress detector is just right to generate a critical refracted longitudinal wave inside the steel structure, ensuring that the ultrasonic longitudinal wave can propagate on the surface of the steel structure. To detect the residual stress in the steel structure, it is necessary to compensate for the propagation time of the ultrasonic longitudinal wave in the paint layer. By studying the influence of different paint layer thicknesses on the propagation time of the ultrasonic longitudinal wave, the coefficient of the paint layer's influence on the propagation time is obtained. According to the paint layer thickness on the surface of the tested part, the paint layer influence coefficient is input into the stress detector. The stress detector is then used to detect the residual stress inside the steel structure, which can not only obtain the true residual stress value of the steel structure under the protective paint, but also eliminate or reduce the error caused by zero stress calibration.

[0062] Optionally, based on the measured ultrasonic longitudinal wave velocity in the paint layer at the thickness of the paint layer on the test piece, the wedge velocity in the acoustic wedge, and the critical angle at which the ultrasonic longitudinal wave obliquely incident from the paint layer into the interior of the test piece, the installation angle of the stress detector on the acoustic wedge is calculated, including: measuring the ultrasonic longitudinal wave excited by the stress detector in the paint layer at the thickness of the paint layer on the test piece; calculating the incident angle of the ultrasonic longitudinal wave obliquely incident on the paint layer of the test piece surface using the law of refraction based on the measured paint layer velocity, the pre-observed wedge velocity, and the pre-observed critical angle at which a critical refracted longitudinal wave can be generated inside the test piece; and setting the installation angle of the stress detector on the acoustic wedge based on the incident angle.

[0063] Specifically, the transmitting transducer in the stress detector excites ultrasonic longitudinal waves that are obliquely incident from the acoustic wedge into the paint layer at a certain angle. Reflection occurs; the reflection angle is the critical angle. The ultrasonic longitudinal waves, incident obliquely from the paint layer into the inspected part at the critical angle, generate critically refracted longitudinal waves, which can be received by the receiving transducer. To ensure that the ultrasonic longitudinal waves can propagate inside the steel structure, the sound velocity in the paint layer needs to be measured to calculate the incident angle that generates critically refracted longitudinal waves inside the steel structure. Based on the calculated incident angle, the tilt angles on both sides of the acoustic wedge are set, and the stress detector is installed on both sides of the acoustic wedge. This ensures that the ultrasonic longitudinal waves excited by the transmitting transducer are obliquely incident from the acoustic wedge into the painted steel structure at a certain angle and can be received by the receiving transducer.

[0064] Figure 2 This is a schematic diagram illustrating the method for setting the installation angle of the stress detector on the acoustic wedge block in this application. Figure 2 In the specific embodiment shown, the acoustic wedge 22 is made of plexiglass. The propagation speed of ultrasonic longitudinal waves in plexiglass is known. The propagation speed of ultrasonic longitudinal waves in the paint layer 23 needs to be measured because different types of paint layers have different densities, resulting in different propagation speeds of ultrasonic longitudinal waves within them. Based on the propagation speed of ultrasonic longitudinal waves in the steel plate 24 of the same material, the incident angle of the ultrasonic longitudinal waves from the paint layer 23 into the steel plate 24 can be calculated, which is the critical angle at which critical refracted longitudinal waves can be generated inside the steel plate 24. These conditions allow us to determine the incident angle of the ultrasonic longitudinal wave emitted onto the paint layer 23, and thus the tilt angles on both sides of the acoustic wedge 22 can be determined. The transmitting transducer probe 21.1 and the receiving transducer probe 21.2 in the stress detector are attached to the tilt angles on both sides of the acoustic wedge 22, ensuring that the ultrasonic longitudinal wave excited by the transmitting transducer probe 21.1 in the stress detector can reach the interior of the steel plate 24 after secondary refraction, and after a fixed sound path, the receiving transducer probe 21.2 in the stress detector can receive the signal.

[0065] Optionally, the paint layer influence coefficient is determined based on the different paint layer thicknesses on the surface of the test piece and the propagation time of the ultrasonic longitudinal wave on the test piece under different paint layer thicknesses. This includes: detecting the propagation time of the ultrasonic longitudinal wave on the test piece under different paint layer thicknesses; and fitting the different paint layer thicknesses and their corresponding propagation times using the least squares method to obtain the paint layer influence coefficient of different paint layer thicknesses on the propagation time of the ultrasonic longitudinal wave.

[0066] Specifically, to detect residual stress inside a steel structure, it is necessary to compensate for the propagation time of ultrasonic longitudinal waves within the paint layer. Through experiments, the influence of paint layers of different thicknesses on the propagation time of ultrasonic longitudinal waves is first studied, thereby obtaining the coefficient of paint layer influence on propagation time, i.e., the paint layer influence coefficient. By using the paint layer influence coefficient, not only can the accuracy of stress detection under the paint layer be improved, but also the error caused by zero-stress calibration can be eliminated or reduced.

[0067] Figure 3 This is an experimental schematic diagram of this application under different paint layer thicknesses. Figure 3 The top layer shows the sound wave propagation time measured on a steel plate surface without a paint layer. Figure 3 The intermediate layer refers to the sound wave propagation time measured when a paint layer with a thickness of n mm is applied to the surface of a steel plate. Figure 3 The lowest layer was a 2n mm thick paint layer on a steel plate. The sound wave propagation time was measured. Based on a series of experiments with different paint thicknesses, a series of data on different paint thicknesses and their corresponding sound wave propagation times were obtained. The least squares method was used to fit these data to obtain the paint layer influence coefficient α for different paint thicknesses, as shown below. Figure 4 The fitting function shown.

[0068] Optionally, based on the compensation parameters formed by the paint layer influence coefficient, the unpainted layer thickness of the zero-stress specimen, and the paint layer thickness of the tested specimen, the zero-stress specimen and the tested specimen are tested separately using a stress detector equipped with compensation parameters at the installation angle of the acoustic wedge, to obtain the residual stress of the tested specimen, including:

[0069] Based on the compensation parameters formed by the paint layer influence coefficient, the unpainted layer thickness of the zero-stress specimen, and the paint layer thickness of the tested specimen, the zero-stress specimen is tested by a stress detector with compensation parameters at the installation angle of the acoustic wedge, and the zero-stress acoustic time and stress detection coefficient are obtained.

[0070] Based on the compensation parameters formed by the paint layer influence coefficient, the unpainted layer thickness of the zero-stress specimen, and the paint layer thickness of the test piece, the test piece is tested by a stress detector with compensation parameters at the installation angle of the acoustic wedge block to obtain the stress acoustic time of the test piece.

[0071] The acoustic time difference is obtained based on the zero-stress acoustic time and the stress acoustic time of the inspected part;

[0072] The residual stress of the inspected part is obtained based on the compensation coefficient, acoustic time difference, and stress detection coefficient.

[0073] Specifically, by using a stress testing instrument that has been compensated for the paint layer, the pre-performed zero-stress calibration and stress detection coefficient calibration processes are more accurate, eliminating or reducing errors caused by the calibration process. Under the condition that the distance between the transmitting and receiving transducers in the stress testing instrument is fixed, the propagation time of the ultrasonic longitudinal wave corresponding to zero stress and the propagation time of the ultrasonic longitudinal wave corresponding to the stress in the tested part are measured. Based on the time difference between the two, the residual stress in the tested part is calculated according to the formula in the standard GB / T 32073-2015 for ultrasonic testing of residual stress.

[0074] Optionally, based on the compensation parameters formed by the paint layer influence coefficient, the unpainted layer thickness of the zero-stress specimen, and the paint layer thickness of the tested specimen, the zero-stress specimen is tested using a stress detector equipped with compensation parameters at the installation angle of the acoustic wedge to obtain the zero-stress acoustic time and stress detection coefficient, and the test also includes:

[0075] The paint layer influence coefficient and the unpainted layer thickness form the first compensation parameter, which is input into the stress detector. The compensation parameter includes the first compensation parameter.

[0076] Zero-stress test specimens are calibrated using a stress detector with a first compensation parameter at the installation angle of the acoustic wedge to obtain the zero-stress acoustic time.

[0077] The stress detection coefficient is obtained by performing a tensile test on a zero-stress specimen using a stress detector with a first compensation parameter at the installation angle of the acoustic wedge.

[0078] Specifically, by using a stress detector with a first compensation parameter to perform zero-stress calibration and tensile tests on zero-stress specimens, the stress detector can more accurately detect residual stress.

[0079] Optionally, to obtain the zero-stress acoustic time by performing zero-stress calibration on the zero-stress specimen using a stress detector with a first compensation parameter at the installation angle of the acoustic wedge, the method further includes:

[0080] Adjust and set the stress detector with the first compensation parameter, and use the acoustic wedge block with the set installation angle to firmly couple the probe of the stress detector with the first compensation parameter into the calibration area of ​​the zero-stress specimen.

[0081] Zero-stress specimens are calibrated to zero stress, and the propagation time of ultrasonic critical refraction longitudinal waves corresponding to zero stress is recorded by a stress detector with the first compensation parameter to obtain the zero-stress acoustic time.

[0082] Specifically, the size of the calibration area for the zero-stress specimen is related to the probe size and ultrasonic frequency. The length L of the detection area is the critical refraction longitudinal wave propagation distance, typically 5mm to 100mm. After adjusting the stress detector to normal operating conditions, set the detection parameters such as detection frequency, filter bandwidth, ultrasonic excitation voltage, ultrasonic receiving gain, probe spacing, and position according to the determined calibration area. After adjusting and setting the instrument, securely couple the probe within the calibration area of ​​the zero-stress specimen to perform zero-stress calibration. With the probe securely coupled within the calibration area of ​​the zero-stress specimen, record the ultrasonic critical refraction longitudinal wave propagation time corresponding to the zero stress measured by the stress detector. Using an instrument probe calibrated with the paint layer influence coefficient for zero-stress calibration can eliminate or reduce the influence of the paint layer, resulting in more accurate test results.

[0083] Optionally, the stress detection coefficient is obtained by performing a tensile test on the zero-stress specimen using a stress detector with a first compensation parameter at the installation angle of the acoustic wedge, and the method further includes:

[0084] Adjust and set the stress detector with the first compensation parameter, and use the acoustic wedge block with the set installation angle to firmly couple the probe of the stress detector with the first compensation parameter into the calibration area of ​​the zero-stress specimen.

[0085] Tensile tests were conducted on the zero-stress specimens to obtain the zero-stress acoustic time difference measured by a stress detector with the first compensation parameter and the tensile stress change measured by the tensile testing equipment.

[0086] The stress detection coefficient is obtained by linearly fitting the zero-stress acoustic time difference and tensile stress change.

[0087] Specifically, within the elastic range of the material, the zero-stress acoustic time difference of the stress detector and the tensile stress output of the tensile testing equipment are recorded. There are no fewer than 10 measurement points and the tensile test is repeated no fewer than 5 times. The average value is taken, and a coordinate graph of the tensile stress value and the zero-stress acoustic time difference is plotted. Then, the data is linearly fitted, and the reciprocal of the slope of the straight line is the stress detection coefficient.

[0088] Optionally, based on the compensation parameters formed by the paint layer influence coefficient, the unpainted layer thickness of the zero-stress specimen, and the paint layer thickness of the tested specimen, the tested specimen is tested using a stress detector equipped with compensation parameters at the installation angle of the acoustic wedge block to obtain the stress acoustic time of the tested specimen, which also includes:

[0089] The second compensation parameter, formed by the paint layer influence coefficient and the paint layer thickness of the inspected part, is input into the stress testing instrument. The compensation parameter includes the second compensation parameter.

[0090] By using a stress detector equipped with a second compensation parameter at the installation angle of the acoustic wedge, the propagation time of the ultrasonic longitudinal wave in the test piece is detected, and the stress acoustic time of the test piece is obtained.

[0091] Specifically, after the thickness of the paint layer on the surface of the test piece is detected by the instrument, the second compensation parameter formed by the paint layer influence coefficient and the paint layer thickness of the test piece is input into the stress tester. The stress tester calibrated by the second compensation parameter is used to perform stress test on the test piece. The residual stress obtained is more realistic, and the influence of the paint layer on the sound time is also eliminated.

[0092] In one specific embodiment, the paint layer influence coefficient α and the unpainted layer thickness h0 of the zero-stress specimen are used to form a first compensation parameter w0, which is then input into a stress detector. The zero-stress acoustic time t0 of the zero-stress specimen is detected using the stress detector equipped with the first compensation parameter w0, and the stress detection coefficient k is obtained through a tensile test. The paint layer influence coefficient α and the paint layer thickness h1 of the tested specimen are then input into a stress detector. The stress acoustic time t1 of the tested specimen is then detected using the stress detector equipped with the first compensation parameter w1. According to the formula in the standard GB / T32073-2015 for ultrasonic testing of residual stress, the residual stress σ=k*Δt=k*(t1-t0), and based on the influence of the compensation parameter, Δw=w1-w0. To eliminate the influence of the paint layer, the residual stress of the tested specimen is k*Δt*Δw.

[0093] [Example of an ultrasonic testing and calibration device for stress under protective paint layers]

[0094] Figure 5 This is a block diagram of the ultrasonic testing and calibration device for the protective coating layer stress of this application. Figure 5 As shown, an ultrasonic testing and calibration device for stress under a protective paint layer includes:

[0095] The acoustic wedge setting module 501 is used to calculate the installation angle of the stress detector on the acoustic wedge based on the measured ultrasonic longitudinal wave velocity in the paint layer at the thickness of the paint layer of the test piece, the wedge velocity in the acoustic wedge, and the critical angle when the ultrasonic longitudinal wave obliquely enters the interior of the test piece from the paint layer.

[0096] The compensation determination module 502 is used to determine the paint layer influence coefficient based on the different paint layer thicknesses set on the surface of the inspected part and the propagation sound of ultrasonic longitudinal waves on the inspected part under different paint layer thicknesses.

[0097] The stress detection and analysis module 503 is used to detect the zero-stress specimen and the test piece respectively by using a stress detector with compensation parameters at the installation angle of the acoustic wedge block, based on the paint layer influence coefficient, the unpainted layer thickness of the zero-stress specimen and the paint layer thickness of the test piece. The residual stress of the test piece is then obtained.

[0098] Specifically, the acoustic wedge setting module 501 prevents ultrasonic longitudinal waves from propagating in the paint layer, ensuring that the stress detector can generate critical refracted longitudinal waves inside the steel structure, enabling the detection of residual stress inside the steel structure; the compensation determination module 502 compensates for the propagation time of ultrasonic longitudinal waves in the paint layer, making up for the influence of paint layer thickness on the time delay of acoustoelastic detection, and improving the detection accuracy of residual stress under the protective paint layer; the stress detection analysis module 503 adds the paint layer influence coefficient and the paint layer thickness of the inspected part, eliminating the influence of the paint layer on the sound wave propagation time for the detection of residual stress inside the steel structure.

[0099] In summary, the ultrasonic testing and calibration method, apparatus, and medium for stress under protective paint layers provided in this application calculate the installation angle of the stress detector on the acoustic wedge to ensure that the incident angle of the ultrasonic longitudinal wave excited by the stress detector is just right to generate a critically refracted longitudinal wave inside the steel structure, thus ensuring that the ultrasonic longitudinal wave can propagate on the surface of the steel structure. To detect residual stress in the steel structure, it is necessary to compensate for the propagation time of the ultrasonic longitudinal wave within the paint layer. By studying the influence of different paint layer thicknesses on the propagation time of the ultrasonic longitudinal wave, a coefficient of paint layer influence on propagation time is obtained. Based on the paint layer thickness on the surface of the tested part, the paint layer influence coefficient is input into the stress detector. Using this stress detector to detect residual stress inside the steel structure, the true residual stress value of the steel structure under the protective paint can be obtained, and the error caused by zero-stress calibration can be eliminated or reduced.

[0100] This application also provides a computer-readable storage medium storing computer instructions, characterized in that the computer instructions are operated to perform the ultrasonic testing and calibration method for stress under protective coating as described in any of the preceding claims.

[0101] This application also provides a computer program product, which includes program instructions that, when executed by a computer, cause the computer to perform the ultrasonic testing and calibration method for stress under protective coating as described in any of the above claims.

[0102] This application also provides a computer device comprising: at least one processor; and a memory communicatively connected to the at least one processor; wherein the memory stores computer instructions executable by the at least one processor, and the at least one processor operates the computer instructions to perform the ultrasonic testing and calibration method for stress under protective coating as described in any of the preceding claims.

[0103] Unless otherwise defined, all technical and scientific terms used throughout this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In case of any inconsistency, the meaning as described herein or derived from the content described herein shall prevail. Furthermore, the terminology used in this description is for the purpose of describing embodiments of the invention only and is not intended to limit the invention.

[0104] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the technical concept of the present invention, all of which fall within the scope of protection of the present invention.

[0105] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A method for ultrasonic testing and calibration of stress under a protective paint layer, characterized in that, include: Based on the measured ultrasonic longitudinal wave velocity in the paint layer at the thickness of the paint layer of the test piece, the wedge velocity in the acoustic wedge, and the critical angle when the ultrasonic longitudinal wave obliquely enters the interior of the test piece from the paint layer, the installation angle of the stress detector on the acoustic wedge is calculated. The paint layer influence coefficient is determined based on the different paint layer thicknesses on the surface of the test piece and the propagation time of the ultrasonic longitudinal wave on the test piece under different paint layer thicknesses. Based on the compensation parameters formed by the paint layer influence coefficient, the unpainted layer thickness of the zero-stress specimen, and the paint layer thickness of the tested specimen, the zero-stress specimen and the tested specimen are tested separately using a stress detector equipped with the compensation parameters at the installation angle of the acoustic wedge to obtain the residual stress of the tested specimen. Specifically, this includes: testing the zero-stress specimen using a stress detector equipped with the compensation parameters at the installation angle of the acoustic wedge to obtain the zero-stress acoustic time and stress detection coefficient; testing the tested specimen using a stress detector equipped with the compensation parameters at the installation angle of the acoustic wedge to obtain the stress acoustic time of the tested specimen; obtaining the acoustic time difference based on the zero-stress acoustic time and the stress acoustic time of the tested specimen; and obtaining the residual stress of the tested specimen based on the compensation parameters, the acoustic time difference, and the stress detection coefficient.

2. The ultrasonic testing and calibration method for stress under protective paint layers as described in claim 1, characterized in that, The installation angle of the stress detector on the acoustic wedge is calculated based on the measured ultrasonic longitudinal wave velocity at the paint layer thickness of the inspected part, the wedge velocity in the acoustic wedge, and the critical angle at which the ultrasonic longitudinal wave obliquely enters the interior of the inspected part from the paint layer. This includes: The ultrasonic longitudinal wave excited by the stress detector is measured at the paint layer velocity of the tested workpiece at the paint layer thickness. Based on the measured sound velocity of the paint layer, the pre-observed sound velocity of the wedge, and the pre-observed critical angle that can generate critical refracted longitudinal waves inside the inspected part, the incident angle of the ultrasonic longitudinal wave obliquely incident on the paint layer on the surface of the inspected part is calculated by the law of refraction. The installation angle of the stress detector on the acoustic wedge is set according to the incident angle.

3. The ultrasonic testing and calibration method for stress under protective paint layers as described in claim 1, characterized in that, The determination of the paint layer influence coefficient based on different paint layer thicknesses on the surface of the inspected part and the propagation of ultrasonic longitudinal waves on the inspected part under different paint layer thicknesses includes: When detecting the propagation of ultrasonic longitudinal waves in the test piece under different paint layer thicknesses on the surface of the test piece; By fitting different paint layer thicknesses and their corresponding acoustic propagation times using the least squares method, the paint layer influence coefficient on the propagation time of the ultrasonic longitudinal wave by different paint layer thicknesses is obtained.

4. The ultrasonic testing and calibration method for stress under protective paint layers as described in claim 1, characterized in that, The method further includes: using a stress detector equipped with the compensation parameters, based on the paint layer influence coefficient, the unpainted layer thickness of the zero-stress specimen, and the paint layer thickness of the tested specimen, to test the zero-stress specimen at the installation angle of the acoustic wedge, thereby obtaining the zero-stress acoustic time and stress detection coefficient; and also includes: The first compensation parameter, formed by the paint layer influence coefficient and the unpainted layer thickness, is input into the stress detector, wherein the compensation parameter includes the first compensation parameter; The zero-stress specimen is calibrated using a stress detector equipped with the first compensation parameter at the installation angle of the acoustic wedge to obtain the zero-stress acoustic time. The stress detection coefficient is obtained by performing a tensile test on the zero-stress specimen using a stress detector equipped with the first compensation parameter at the installation angle of the acoustic wedge.

5. The ultrasonic testing and calibration method for stress under protective paint layers as described in claim 4, characterized in that, The step of calibrating the zero-stress specimen using a stress detector equipped with the first compensation parameter at the installation angle of the acoustic wedge to obtain zero-stress acoustic time also includes: Adjust and set the stress detector with the first compensation parameter, and use the acoustic wedge block with the set installation angle to stably couple the probe of the stress detector with the first compensation parameter to the calibration area of ​​the zero-stress specimen. The zero-stress specimen is calibrated to zero stress, and the ultrasonic critical refraction longitudinal wave propagation time corresponding to zero stress is recorded by the stress detector with the first compensation parameter to obtain the zero-stress acoustic time.

6. The ultrasonic testing and calibration method for stress under protective paint layers as described in claim 4, characterized in that, The step of performing a tensile test on the zero-stress specimen using a stress detector equipped with the first compensation parameter at the installation angle of the acoustic wedge to obtain the stress detection coefficient further includes: Adjust and set the stress detector with the first compensation parameter, and use the acoustic wedge block with the set installation angle to stably couple the probe of the stress detector with the first compensation parameter to the calibration area of ​​the zero-stress specimen. Tensile tests were performed on the zero-stress specimen to obtain the zero-stress acoustic time difference measured by a stress detector equipped with the first compensation parameter and the tensile stress change measured by a tensile testing device. The stress detection coefficient is obtained by linearly fitting the zero-stress acoustic time difference and the tensile stress change.

7. The ultrasonic testing and calibration method for stress under protective paint layers as described in claim 1, characterized in that, The method further includes, based on the compensation parameters formed by the paint layer influence coefficient, the unpainted layer thickness of the zero-stress specimen, and the paint layer thickness of the tested specimen, using a stress detector equipped with the compensation parameters at the installation angle of the acoustic wedge to test the tested specimen and obtain the stress sound of the tested specimen, as follows: The second compensation parameter, formed by the paint layer influence coefficient and the paint layer thickness of the tested part, is input into the stress testing instrument, wherein the compensation parameter includes the second compensation parameter; By using a stress detector equipped with the second compensation parameter at the installation angle of the acoustic wedge, the propagation time of the ultrasonic longitudinal wave in the test piece is detected, and the stress acoustic time of the test piece is obtained.

8. A device for ultrasonic testing and calibration of stress under a protective paint layer, characterized in that, include: The acoustic wedge setting module is used to calculate the installation angle of the stress detector on the acoustic wedge based on the measured ultrasonic longitudinal wave velocity in the paint layer at the thickness of the paint layer of the test piece, the wedge velocity in the acoustic wedge, and the critical angle when the ultrasonic longitudinal wave obliquely enters the interior of the test piece from the paint layer. The compensation determination module is used to determine the paint layer influence coefficient based on the different paint layer thicknesses on the surface of the test piece and the propagation sound of the ultrasonic longitudinal wave on the test piece under different paint layer thicknesses. The stress detection and analysis module is used to detect the zero-stress specimen and the test piece respectively by using a stress detector equipped with the compensation parameters formed by the paint layer influence coefficient, the unpainted layer thickness of the zero-stress specimen and the paint layer thickness of the test piece at the installation angle of the acoustic wedge, and to obtain the residual stress of the test piece. Specifically, the stress detection and analysis module is used to: 1) ...

9. A computer-readable storage medium storing computer instructions, characterized in that, The computer instructions are operated to perform the ultrasonic testing and calibration method for stress under the protective coating layer as described in any one of claims 1-7.

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