Device and Method for Measuring Longitudinal and Transverse Wave Sound Velocities of Materials at High Temperatures Based on Laser Ultrasonics

Abstract

The present invention discloses a device and method for measuring the longitudinal and transverse wave sound velocities of materials based on laser ultrasound, which includes controlling a Nd:Yag pulsed laser to emit laser light. In an inert gas protection environment, different modal sound waves are excited through the thermoelastic / thermoablation effect and propagate inside the material to be measured, reflecting back and forth and propagating to the upper and lower surfaces. The incident laser point and the laser detection point are adjusted to the same axis, and the dual-wave mixing interferometer is moved to measure the received different modal sound waves multiple times in a linear scanning manner. The decomposition of laser ultrasound longitudinal and transverse wave modes is achieved through variational mode decomposition. Two sets of array data are obtained using the cross-correlation algorithm, and the material parameters to be measured are calculated by performing linear fitting on the results. The present invention realizes the separation and signal post-processing of different modal sound waves excited by laser ultrasound, and is applicable to the simultaneous measurement of longitudinal and transverse wave sound velocities; it can ignore the influence of the material's own thermal expansion at high temperatures and reduce the measurement uncertainty introduced by this influencing factor.

Description

Technical Field

[0001] The present invention relates to the technical field of shear wave velocity measurement, and particularly to a device and method for measuring longitudinal and shear wave velocities of materials at high temperatures based on laser ultrasound. Background Art

[0002] Inspection and testing are the key links and important supports for the safety guarantee of special equipment. The acoustic parameters of materials have a great influence on the accuracy of non-destructive testing results and change with temperature. For example, for martensitic heat-resistant steel P91, the sound velocity will decrease from 3300 m / s to 2500 m / s from 20 °C to 630 °C. As the core parameter in the calculation of the phased array ultrasonic focusing rule, a 5% change in the sound velocity will cause a 5% positioning error and a 10% quantification error. Accurately obtaining the key detection parameters of materials at different temperatures is an important basis for achieving accurate high-temperature detection.

[0003] Among them, the more common ones are traditional measurement methods based on ultrasonic waves. However, these methods face many challenges when applied to high-temperature environments: traditional ultrasonic transducers are easily damaged at high temperatures, limiting the measurement temperature range; the surface reflection characteristics of materials change greatly at high temperatures, affecting the accuracy of signal reception and processing; materials have the phenomenon of thermal expansion and contraction, and due to thermal expansion, there are thickness changes at high temperatures, and it is necessary to use the coefficient of thermal expansion of the material for thickness correction, and this coefficient is usually also an unknown quantity, introducing a large measurement uncertainty. To obtain the sound velocities of different modes of materials, such as longitudinal waves, shear waves, etc., different electromagnetic acoustic transducers need to be used for excitation. EMAT can only detect ferromagnetic materials, and the transducer needs to be close to the object to be measured, and the lift-off distance is limited. Moreover, the high-temperature environment easily leads to a decline in the performance of electronic devices, increasing the measurement error. At present, there is no mature method for measuring the acoustic parameters of high-temperature materials at home and abroad, which affects the detection accuracy of the thickness, defects, etc. of high-temperature special equipment and restricts its safe and stable operation. At the same time, there is a lack of a method for measuring the shear wave velocity of materials at high temperatures, which affects the traceability of the measured values of electromagnetic ultrasonic shear wave detection. Therefore, a device and method for measuring longitudinal and shear wave velocities of materials at high temperatures based on laser ultrasound are needed. Summary of the Invention

[0004] The object of the present invention is to provide a method for measuring longitudinal and shear wave velocities of materials at high temperatures based on laser ultrasound, to solve the problems of difficult measurement of material sound velocities in complex and extreme environments such as high temperatures and increased uncertainty introduced by thermal expansion, and to be applicable to the traceability of longitudinal and shear wave velocity values of materials, meeting the requirements of quality control of special equipment, instrument research and development, and calibration, etc.

[0005] To achieve the above object, the present invention is implemented according to the following technical solutions:

[0006] The present invention includes the following steps:

[0007] A controls the Nd:Yag pulsed laser to emit laser light, which is reflected by a mirror and then focused by a cylindrical lens to form a linear light spot, and is incident on the upper surface of the sample located in the heating furnace. In an inert gas protection environment, different modal acoustic waves are excited through the thermoelastic / thermo-erosion effect, and propagate through the interior of the measured material, reflecting back and forth between the upper and lower surfaces;

[0008] B The vibration information of different modal acoustic waves received is transmitted to the oscilloscope and the upper computer through signal demodulation;

[0009] C Adjust the incident laser spot and the laser detection point to the same axis, and move the two-wave mixing interferometer to measure the different modal acoustic waves received multiple times in a straight-line scanning manner;

[0010] D Realize the decomposition of laser ultrasonic longitudinal wave and transverse wave modes through variational mode decomposition;

[0011] E Use the cross-correlation algorithm to solve the flight times of the longitudinal wave and the transverse wave at different lateral offsets x i of the two-wave mixing interferometer respectively. Then, two sets of array data are obtained for the longitudinal wave and the transverse wave. By performing linear fitting on the results, the slopes of the obtained straight lines are the square of the longitudinal wave sound velocity and the transverse wave sound velocity v L 2 and v S 2 , -h 2 is the intercept, and the longitudinal wave sound velocity v L , the transverse wave sound velocity v S and the thickness h at this temperature can be calculated respectively.

[0012] Furthermore, the two-wave mixing interferometer is arranged on the same side or the opposite side of the Nd:Yag pulsed laser. When laser ultrasonic heterosided reception is adopted, the following relationships exist among the physical quantities:

[0013] x i 2 = v L 2 t Li 2 -h 2 (4)

[0014] For the measurement of the transverse wave sound velocity, there is a functional relationship:

[0015] x i 2 = v S 2 t Si 2 -h 2 (5)

[0016] When laser ultrasonic homosided reception is adopted, the following relationships exist among the physical quantities of the measured material:

[0017] x i 2 = v L 2 t Li 2 -4h 2 (8)

[0018] Similarly, for the measurement of the shear wave velocity, there is a functional relationship:

[0019] x i 2 = v S 2 t Si 2 -4h 2 (9)

[0020] The thickness of the material under test at a certain temperature is denoted as h. After each step movement, the lateral offset distance between the laser detection point and the incident laser is denoted as x i , the propagation path of the acoustic wave in the material under test is denoted as d i , the propagation time of the longitudinal wave in the material under test is denoted as t Li , the propagation time of the shear wave in the material under test is denoted as t Si , where i is a natural number.

[0021] Further, in step A, the working temperature is heated to 40°C - 650°C.

[0022] In another aspect, a device for measuring the high-temperature longitudinal and shear wave velocities of a material based on laser ultrasound includes a measurement chamber, a laser ultrasound system, and a host computer. A temperature control system is provided in the measurement chamber. The measurement chamber is provided with an inert gas inlet. The laser ultrasound system is arranged above the measurement chamber. The laser ultrasound system includes a Nd:Yag pulsed laser and a two-wave mixing interferometer. The two-wave mixing interferometer is arranged on an electric control translation stage for step movement to measure different modal acoustic waves received in a linear scanning manner multiple times; the control output end of the host computer is connected to the control input end of the electric control translation stage.

[0023] Further, an oscilloscope is provided at the output end of the two-wave mixing interferometer, and the output end of the two-wave mixing interferometer is connected to the input end of the oscilloscope.

[0024] Further, the temperature control system includes multiple layers of electric heating wires arranged in the measurement chamber.

[0025] Further, the two-wave mixing interferometer and the Nd:Yag pulsed laser are arranged on the same side or on different sides.

[0026] The beneficial effects of the present invention are:

[0027] The present invention relates to a device and method for measuring the longitudinal and transverse wave sound velocities of materials at high temperatures based on laser ultrasound. Compared with the prior art, the present invention has the following technical effects:

[0028] The present invention realizes the separation of different modal acoustic waves excited by laser ultrasound and the post-processing of signals, and is applicable to the simultaneous measurement of longitudinal and transverse wave sound velocities; the influence of the thermal expansion of the material itself at high temperatures can be ignored, reducing the measurement uncertainty introduced by this influencing factor. Description of the Drawings

[0029] Figure 1 It is a schematic structural diagram of a device for measuring the longitudinal and transverse wave sound velocities of materials at high temperatures based on laser ultrasound according to the present invention;

[0030] Figure 2 It is a schematic diagram of the excitation and reception measurement of different modal acoustic waves of laser ultrasound with opposite-side reception for measuring the longitudinal and transverse wave sound velocities of materials at high temperatures based on laser ultrasound according to the present invention;

[0031] Figure 3 It is a schematic diagram of the excitation and reception measurement of different modal acoustic waves of laser ultrasound with same-side reception for measuring the longitudinal and transverse wave sound velocities of materials at high temperatures based on laser ultrasound according to the present invention; Detailed Embodiments

[0032] The following and specific embodiments further describe the present invention. The illustrative embodiments and explanations of this invention are used to explain the present invention, but do not limit the present invention.

[0033] As Figure 1 shown, the measurement device includes a measurement chamber, a laser ultrasound system, and a host computer. A temperature control system is provided in the measurement chamber. The measurement chamber is provided with an inert gas inlet. The laser ultrasound system is arranged above the measurement chamber. The laser ultrasound system includes a Nd:Yag pulsed laser and a double-wave mixing interferometer. The double-wave mixing interferometer is arranged on an electric control translation stage for stepping movement to measure different modal acoustic waves received in a linear scanning manner multiple times. The control output end of the host computer is connected to the control input end of the electric control translation stage.

[0034] In this embodiment, a method for measuring the longitudinal and transverse wave sound velocities of materials at high temperatures based on laser ultrasound includes the following steps:

[0035] Step 1: Build a material sound velocity measurement system based on laser ultrasound under high-temperature conditions, including a heating furnace, an inert protective gas, a Nd:Yag pulsed laser, an electric control translation stage, a cylindrical lens, a double-wave mixing laser interferometer, an oscilloscope, and a host computer, etc.;

[0036] Step 2: Design the heating working temperature and keep it warm for a period of time, and fill argon or nitrogen as an inert protective gas to prevent the material under test from being oxidized;

[0037] Step 3: Heat to the working temperature of 40°C - 650°C in the inert protective gas, control the Nd:Yag pulsed laser to emit laser light, which is reflected by a mirror and then focused by a cylindrical lens to form a linear light spot, and is incident on the upper surface of the sample located in the heating furnace. Different modal acoustic waves are excited through the thermoelastic / thermo-erosion effect and propagate through the material under test, reflecting back and forth between the upper and lower surfaces;

[0038] Step 4: Receive the vibration information of different modal acoustic waves and transmit it to the oscilloscope and the upper computer through signal demodulation;

[0039] Step 5: Adjust the incident laser spot and the laser detection point to the same axis;

[0040] Step 6: Under the motion control of the upper computer, move the dual-wave mixing interferometer along a straight line with a fixed step size, gradually move away from the incident laser spot, that is, move the dual-wave mixing interferometer, and measure the different modal acoustic waves received multiple times in a straight-line scanning manner;

[0041] The thickness of the material under test at a certain temperature is denoted as h. After each step movement, the lateral offset distance between the laser detection point and the incident laser is denoted as x i , the propagation path of the acoustic wave in the material under test is denoted as d i , the propagation time of the longitudinal wave in the material under test is denoted as t Li , the propagation time of the shear wave in the material under test is denoted as t Si , where i is a natural number;

[0042] Step 7: Realize the decomposition of the laser ultrasonic longitudinal wave and shear wave modes through variational mode decomposition;

[0043] Step 8: Use the cross-correlation algorithm to solve the flight times of the longitudinal wave and the shear wave at different lateral offsets x i of the dual-wave mixing interferometer respectively. Then, two sets of array data are obtained for the longitudinal wave and the shear wave, which are (x i , t Li ) and (x i , t Si ). By performing linear fitting on the results, the slopes of the obtained straight lines are the squares of the longitudinal wave sound speed and the shear wave sound speed v L 2 and v S 2 , -h 2 is the intercept, and the longitudinal wave sound speed v L , the shear wave sound speed v S and the thickness h at this temperature can be calculated respectively.

[0044] Specifically, when using laser ultrasonic heterolateral reception, as Figure 2 shown:

[0045] Then there are the following relationships between the physical quantities:

[0046] d i = v L t Li (2)

[0047] d i 2 = x i 2 + h 2 (3)

[0048] Combining formulas (2) and (3), we get:

[0049] x i 2 = v L 2 t Li 2 - h 2 (4)

[0050] Similarly, for the measurement of the shear wave velocity, there is a functional relationship:

[0051] x i 2 = v S 2 t Si 2 - h 2 (5)

[0052] Then, for the two sets of array data measured in step eight, taking x as the ordinate and t as the abscissa, a rectangular coordinate system is established, and linear fitting is performed on several coordinate values, that is, several measurement results of the corresponding lateral offsets. The slopes of the obtained straight lines are the squares of the longitudinal wave velocity and the shear wave velocity v L 2 and v S 2 , - h 2 is the intercept, and thus the longitudinal wave velocity v L of the material, the shear wave velocity v S and the thickness h at this temperature can be calculated respectively.

[0053] Specifically, when using laser ultrasonic ipsilateral reception, as Figure 3 shown:

[0054] Then there are the following relationships between the physical quantities:

[0055] 2d i = v L t Li(6)

[0056]

[0057] Combining equations (6) and (7), we get:

[0058] x i 2 = v L 2 t Li 2 - 4h 2 (8)

[0059] Similarly, for the measurement of the shear wave velocity, there is a functional relationship:

[0060] x i 2 = v S 2 t Si 2 - 4h 2 (9)

[0061] Then, for the two sets of array data measured by the same - side reception, we can still use x as the ordinate and t as the abscissa to establish a rectangular coordinate system. By performing linear fitting on the measurement results of several corresponding lateral offsets, the slopes of the obtained straight lines are the squares of the longitudinal wave velocity and the shear wave velocity, v L 2 and v S 2 , - 4h 2 is the intercept, and then the longitudinal wave velocity v L and the shear wave velocity v S of the material and the thickness h at this temperature can be calculated respectively.

[0062] The above - mentioned are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for measuring the sound velocity of high-temperature longitudinal and transverse waves of materials based on laser ultrasound, characterized in that: The following steps are involved: A controls the Nd:Yag pulse laser to emit laser, which is reflected by the reflector and focused by the cylindrical mirror to form a linear spot, which is incident on the upper surface of the sample in the heating furnace. Under the protection of inert gas, different modes of sound waves are excited by the thermal elasticity / thermal erosion effect, and propagate through the inside of the material being tested, and propagate to the upper and lower surfaces through reciprocating reflection; The different modes of acoustic vibration information received by B are transmitted to the oscilloscope and the host computer through signal demodulation; C. Adjust the incident laser point and the laser detection point to the same axis, and move the dual-wave hybrid interferometer to measure the received sound waves of different modes multiple times in a linear scanning manner; D. Decomposition of laser ultrasonic longitudinal and shear wave modes is achieved through variational mode decomposition; E uses the cross-correlation algorithm to solve the longitudinal and transverse waves at different lateral offsets x of the dual-wave hybrid interferometer. i The flight time under the condition of , two sets of array data are obtained for longitudinal wave and transverse wave. By linear fitting the results, the slopes of the obtained straight lines are the squares of the longitudinal wave speed and the transverse wave speed, respectively. and , -h 2 As the intercept, the longitudinal wave speed of the material can be calculated respectively , shear wave speed and thickness h at a certain temperature; When laser ultrasound is received on the opposite side, the following relationship exists between the physical quantities: （4） For the measurement of shear wave sound velocity, there is a functional relationship: （5） When laser ultrasound is used for same-side reception, the following relationship exists between the physical quantities of the measured material: （8） Similarly, for the measurement of shear wave speed of sound, there is a functional relationship: （9） The thickness of the material under test at a certain temperature is recorded as h. After each step, the lateral offset distance between the laser detection point and the incident laser is recorded as x. i , the propagation path of the sound wave in the material being tested is denoted as d i , the propagation time of the longitudinal wave in the material being tested is recorded as t Li , the propagation time of the shear wave in the material being tested is recorded as t Si , where i is a natural number.

2. According to the method for measuring the high-temperature longitudinal and transverse wave speeds of materials based on laser ultrasound in claim 1, it is characterized in that: In step A, the heating working temperature is 40°C-650°C.

3. A laser ultrasound-based high-temperature longitudinal and transverse wave velocity measurement device for materials, used to perform a laser ultrasound-based high-temperature longitudinal and transverse wave velocity measurement method for materials according to any one of claims 1 to 2, characterized in that: The invention comprises a measuring room, a laser ultrasonic system and a host computer. The measuring room is provided with a temperature control system, the measuring room is provided with an inert gas inlet, the laser ultrasonic system is provided above the measuring room, the laser ultrasonic system comprises a Nd:Yag pulse laser and a double-wave mixing interferometer, the double-wave mixing interferometer is provided on an electrically controlled translation stage for stepping movement, and measures the received sound waves of different modes multiple times in a linear scanning manner; the control output end of the host computer is connected to the control input end of the electrically controlled translation stage.

4. According to claim 3, a laser ultrasound-based high-temperature longitudinal and transverse wave sound velocity measurement device for materials, characterized in that: An oscilloscope is provided at the output end of the dual-wave mixing interferometer, and the signal output end of the dual-wave mixing interferometer is connected to the signal input end of the oscilloscope.

5. According to claim 3, a laser ultrasound-based high-temperature longitudinal and transverse wave velocity measurement device for materials, characterized in that: The temperature control system comprises a multi-layer electric heating wire arranged in the measuring chamber.

6. According to claim 3, a laser ultrasound-based high-temperature longitudinal and transverse wave velocity measurement device for materials, characterized in that: The double-wave mixing interferometer is arranged on the same side or on the opposite side as the Nd:Yag pulse laser.

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