Material high-temperature longitudinal wave and transverse wave sound velocity measuring device and method based on laser ultrasound

Abstract

The invention discloses a material high-temperature longitudinal wave and transverse wave sound velocity measurement device and method based on laser ultrasound, and the method comprises the steps: controlling an Nd: Yag pulse laser to emit laser, exciting sound waves in different modes through a thermal elastic / thermal etching effect under the protection of inert gas, and transmitting the sound waves to the upper and lower surfaces through internal transmission and reciprocating reflection of a measured material; an incident laser point and a laser detection point are adjusted to be on the same axis, and the double-wave mixing interferometer is moved to measure received sound waves of different modes for multiple times in a linear scanning mode; laser ultrasonic longitudinal wave and transverse wave mode decomposition is realized through variational mode decomposition; and obtaining two groups of array data by using a cross-correlation algorithm, and performing linear fitting calculation on a result to obtain parameters of the to-be-tested material. Separation and signal post-processing of different modes of sound waves excited by laser ultrasound are achieved, and the method is suitable for simultaneous measurement of longitudinal wave and transverse wave sound velocities; the influence of thermal expansion of the material at high temperature can be neglected, and the measurement uncertainty introduced by the influence factor is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of shear wave sound velocity measurement, and in particular to a device and method for measuring the sound velocity of high-temperature longitudinal waves and shear waves of materials based on laser ultrasound. Background Art

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

[0003] Among them, the more common ones are traditional measurement methods based on ultrasound. 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 at high temperatures change greatly, affecting the accuracy of signal reception and processing; materials have the phenomenon of thermal expansion and contraction. At high temperatures, the thickness changes due to thermal expansion, and the thickness correction needs to be made using the thermal expansion coefficient of the material. However, this coefficient is usually an unknown quantity, which introduces a large measurement uncertainty. In order to obtain the sound velocity of materials in different modes, such as longitudinal waves and transverse waves, 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 being measured, with a limited lifting distance. Furthermore, high-temperature environments can easily lead to a decrease in the performance of electronic equipment, increasing measurement errors. At present, mature high-temperature material acoustic parameter measurement methods have not yet been established at home and abroad, which affects the detection accuracy of thickness, defects, etc. of high-temperature special equipment and restricts its safe and stable operation. At the same time, there is a lack of measurement methods for the high-temperature shear wave sound velocity of materials, which affects the traceability of electromagnetic ultrasonic shear wave detection values. Therefore, a device and method for measuring the high-temperature longitudinal and shear wave sound velocity of materials based on laser ultrasound is needed. Summary of the invention

[0004] The purpose of the present invention is to provide a method for measuring the sound velocity of high-temperature longitudinal and transverse waves of materials based on laser ultrasound, which can solve the problems of difficulty in measuring the sound velocity of materials in complex extreme environments such as high temperature, increased uncertainty due to thermal expansion, etc. The method is suitable for tracing the value of the sound velocity of high-temperature longitudinal and transverse waves of materials, and can meet the needs of special equipment quality control, instrument 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 comprises the following steps:

[0007] 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;

[0008] The different modes of acoustic vibration information received by B are transmitted to the oscilloscope and the host computer through signal demodulation;

[0009] 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;

[0010] D. Decomposition of laser ultrasonic longitudinal and shear wave modes is achieved through variational mode decomposition;

[0011] 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. L 2 and v S 2 , -h 2 As the intercept, the material longitudinal wave speed v can be calculated respectively L , shear wave speed v S and the thickness h at that temperature.

[0012] Furthermore, the dual-wave hybrid interferometer is arranged on the same side or on the opposite side as the Nd:Yag pulse laser. When laser ultrasound is received on the opposite sides, the following relationship exists between the physical quantities:

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

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

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

[0016] When laser ultrasound is used for same-side reception, the following relationship exists between 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 shear wave speed of sound, 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 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.

[0021] Furthermore, in step A, the heating working temperature is 40°C-650°C.

[0022] In another aspect, a laser ultrasound-based high-temperature longitudinal and transverse wave sound velocity measurement device for materials comprises a measuring chamber, a laser ultrasound system and a host computer, wherein a temperature control system is arranged in the measuring chamber, an inert gas inlet is arranged in the measuring chamber, the laser ultrasound system is arranged above the measuring chamber, the laser ultrasound system comprises a Nd:Yag pulse laser and a dual-wave mixing interferometer, the dual-wave mixing interferometer is arranged 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.

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

[0024] Furthermore, the temperature control system includes a multi-layer electric heating wire arranged in the measuring chamber.

[0025] Furthermore, the dual-wave mixing interferometer is arranged on the same side or on different sides as the Nd:Yag pulse laser.

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

[0027] The present invention is a device and method for measuring the sound velocity of high-temperature longitudinal and transverse waves of materials 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 modes of sound waves excited by laser ultrasound and signal post-processing, and is suitable for the simultaneous measurement of longitudinal and transverse wave sound velocities; the influence of thermal expansion of the material itself at high temperature can be ignored, and the measurement uncertainty introduced by this influencing factor can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic structural diagram of a device for measuring the sound velocity of high-temperature longitudinal and transverse waves of a material based on laser ultrasound according to the present invention;

[0030] Figure 2 It is a schematic diagram of laser ultrasound different mode sound wave excitation and receiving measurement based on the laser ultrasound of the present invention for high temperature longitudinal wave and transverse wave sound velocity measurement of materials with different reception modes;

[0031] Figure 3 It is a schematic diagram of the same-side receiving laser ultrasound sound wave excitation and receiving measurement of different modes of the material high-temperature longitudinal wave and transverse wave sound velocity measurement device based on laser ultrasound of the present invention; DETAILED DESCRIPTION

[0032] The present invention is further described below with specific examples. The illustrative examples and descriptions of the present invention are used to explain the present invention but are not intended to limit the present invention.

[0033] like Figure 1 As shown, the measuring device includes a measuring chamber, a laser ultrasonic system and a host computer, wherein the measuring chamber is provided with a temperature control system, the measuring chamber is provided with an inert gas inlet, the laser ultrasonic system is provided above the measuring chamber, the laser ultrasonic system includes a Nd:Yag pulse laser and a dual-wave mixing interferometer, the dual-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.

[0034] In this embodiment, a method for measuring the high-temperature longitudinal and shear wave sound velocities of a material based on laser ultrasound includes the following steps:

[0035] Step 1: Build a laser ultrasonic material sound velocity measurement system under high temperature conditions, including a heating furnace, an inert protective gas, a Nd:Yag pulse laser, an electrically controlled translation stage, a cylindrical lens, a dual-wave hybrid laser interferometer, an oscilloscope, and a host computer;

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

[0037] Step 3: Heat the working temperature to 40℃-650℃ in an inert protective gas, control 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, and stimulates different modes of sound waves through the thermoelastic / thermal erosion effect, and propagates through the inside of the material being tested, and propagates to the upper and lower surfaces through reciprocating reflection;

[0038] Step 4: The received acoustic vibration information of different modes is transmitted to the oscilloscope and the host computer through signal demodulation;

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

[0040] Step 6: Under the motion control of the host computer, the dual-wave hybrid interferometer is moved along a straight line with a fixed step length, gradually away from the incident laser point, that is, the dual-wave hybrid interferometer is moved to measure the received different mode sound waves multiple times in a linear scanning manner;

[0041] 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;

[0042] Step 7: Decomposition of laser ultrasonic longitudinal and shear wave modes is achieved through variational modal decomposition;

[0043] Step 8: Use the cross-correlation algorithm to solve the longitudinal and transverse waves at different lateral offsets x in the dual-wave hybrid interferometer. i Under the flight time, two sets of array data are obtained for the longitudinal wave and the transverse wave, respectively (x i , t Li ) and (x i , t Si ); By linear fitting the results, the slopes of the straight lines are the squares of the longitudinal wave speed and the transverse wave speed v L 2 and v S 2 , -h 2 As the intercept, the material longitudinal wave speed v can be calculated respectively L , shear wave speed v S and the thickness h at that temperature.

[0044] In particular, when laser ultrasound is used for opposite-side reception, such as Figure 2 As shown:

[0045] Then the following relationship exists 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 have:

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

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

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

[0052] Then, the two sets of array data measured in step 8 are used to establish a rectangular coordinate system with x as the ordinate and t as the abscissa, and a linear fit is performed on several coordinate values, i.e., several corresponding lateral offset measurement results. The slopes of the obtained straight lines are the squares of the longitudinal wave speed and the transverse wave speed v respectively. L 2 and v S 2 , -h 2 As the intercept, the material longitudinal wave speed v can be calculated respectively L , shear wave speed v S and the thickness h at that temperature.

[0053] In particular, when laser ultrasound is used for ipsilateral reception, such as Figure 3 As shown:

[0054] Then the following relationship exists between the physical quantities:

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

[0056]

[0057] Combining formulas (6) and (7), we have:

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

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

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

[0061] Then, the two sets of array data measured on the same side can still be used to establish a rectangular coordinate system with x as the ordinate and t as the abscissa. Linear fitting is performed on the measurement results of the corresponding lateral offset several times, and the slopes of the obtained straight lines are the squares of the longitudinal wave speed and the transverse wave speed v L 2 and v S 2 , -4h 2 is the intercept, and then the material longitudinal wave speed v is calculated respectively L , shear wave speed v S and the thickness h at that temperature.

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in 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. L 2 and v S 2 , -h 2 As the intercept, the material longitudinal wave speed v can be calculated respectively. L , shear wave speed v S and the thickness h at that temperature.

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: When laser ultrasound is received on the opposite side, the following relationship exists between the physical quantities: x i 2 =v L 2 t Li 2 -h 2 (4) For the measurement of shear wave sound velocity, there is a functional relationship: x i 2 =v S 2 t Si 2 -h 2 (5) When laser ultrasound is used for same-side reception, the following relationship exists between the physical quantities of the measured material: x i 2 =v L 2 t Li 2 -4h 2 (8) Similarly, for the measurement of shear wave speed of sound, there is a functional relationship: x i 2 =v S 2 t Si 2 -4h 2 (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.

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

4. 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 3, 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.

5. According to the laser ultrasound-based high-temperature longitudinal and transverse wave velocity measurement device of material according to claim 1, it is 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.

6. The laser ultrasound-based high-temperature longitudinal and transverse wave velocity measurement device for materials according to claim 1, characterized in that: The temperature control system comprises a multi-layer electric heating wire arranged in the measuring chamber.

7. The laser ultrasound-based high-temperature longitudinal and transverse wave velocity measurement device for materials according to claim 1, 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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