Laser film internal friction instrument and material internal friction detection method

Abstract

The present invention discloses a laser thin film internal friction meter, comprising a laser displacement sensor, a base plate, a lower cover body fixed on the base plate, and an upper cover body matched with the lower cover body, a cavity is formed between the base plate, the lower cover body and the upper cover body, a sample fixing assembly, an excitation electrode, a heater and a shielding cover are arranged in the cavity, an optical window corresponding to the laser displacement sensor is provided on the lower cover body, the heater is located in the shielding cover, the shielding cover is used to cover the sample and the excitation electrode, the shielding cover is provided with a through hole corresponding to the laser displacement sensor, the excitation electrode faces the through hole, and the sample is located between the through hole and the excitation electrode. The laser thin film internal friction meter of the present invention has the advantages of high measurement accuracy, wide operating frequency, non-contact measurement to obtain material defect information, etc., and is very suitable for characterizing irradiation defects.

Description

Technical Field

[0001] The invention specifically relates to a laser film internal friction instrument for non-contact detection of material defects and a detection method using the laser film internal friction instrument. Background Art

[0002] As an advanced nondestructive testing technology, internal friction testing technology is sensitive to the microstructure of metal materials and has been applied in the microstructural research of irradiation defects in nuclear structural materials and the nondestructive testing of material aging. The measurement of internal friction spectrum is different from other nondestructive testing methods in that its frequency range completely covers the intrinsic frequency range of the slow transition process of defects, and the added stimulus signal is alternating stress (whose amplitude is much smaller than the yield stress of the material), and the response signal is strain. It is applicable to any object that can propagate elastic stress waves and has been proven to be one of the most effective means to study the defect relaxation process and microstructural changes.

[0003] Internal friction refers to the ability of a material to consume kinetic energy quickly or slowly when it is isolated from the outside world. Its physical essence is the dissipation of mechanical vibration energy caused by internal defects and atomic motion of the material. Therefore, by measuring the internal friction and elastic modulus changes of the material under certain external conditions (such as temperature, frequency, amplitude, etc.), the microscopic defect information of the material can be reflected, and microscopic defect parameters such as defect concentration and distribution, defect diffusion activation energy, and phase change dynamics can be obtained. Therefore, the internal friction technology is often called internal friction spectrum, or mechanical spectrum. The measurement frequency range of internal friction spectrum is 0.001Hz to kHz, which completely covers the intrinsic frequency range of the process of slow transition of defects (such as the transition process of point defects between adjacent equilibrium positions). In addition, the added stimulus signal is alternating stress (whose amplitude is much smaller than the yield stress of the material), and the response signal is strain. Therefore, it is applicable to any object that can transmit elastic stress waves, and has been proven to be one of the most effective non-destructive testing methods for studying defect relaxation processes and microstructural changes.

[0004] At present, the measurement methods of internal friction mainly adopt two modes: forced vibration and free decay. When measuring internal friction in the forced vibration mode, a sinusoidal signal σ=σ0sinωt generated by the ultra-low frequency signal generator is amplified and sent to the drive coil to drive the pendulum with a permanent magnet to twist, causing it to torsionally vibrate according to the sine wave law. At this time, the strain signal can be expressed as ε=ε0sin(ωt-φ). By comparing it with the excited sinusoidal signal, the phase difference φ of the two signals can be obtained, and the corresponding tanφ is the internal friction value Q -1 .

[0005] In the free decay mode, the internal friction measurement principle is as follows: the computer issues a command to twist the sample to the set maximum amplitude, and then the sample performs free decay motion and measures its vibration decay curve. Under the condition that the internal friction is independent of the amplitude, the value of δ can be calculated using the amplitude of multiple vibrations, that is, the value of δ is calculated using the relationship (1). n and A n+m are the amplitudes of the nth and n+mth vibrations respectively.

[0006]

[0007]

[0008] Thus, according to the free decay curve of the sample, According to the calculation formula (2), the internal friction value of the sample can be obtained.

[0009] Internal friction measurement technology is inseparable from the two measurement modes of forced vibration and free decay. At present, the development of internal friction test equipment is mainly focused on meeting the requirements of samples with different properties, shapes and sizes. After long-term practice and continuous exploration, relevant researchers at home and abroad have developed a series of internal friction measurement technologies that are both scientific and practical. They mainly include electrostatic excitation vibration method, optical microscopy magnification detection of strain amplitude, atomic force microscope cantilever beam detection of strain amplitude, etc. The above technologies still have the following problems when detecting surface defects of nuclear power materials damaged by irradiation: (1) The measurement accuracy of capacitive sensors is not enough. The laser displacement sensors sold on the market are either unable to be used at high and low temperatures, or require the amplitude of the sample to be as large as possible, which cannot meet the requirements of small amplitude detection. (2) Changing the measurement frequency is cumbersome. In order to improve the measurement accuracy, the thin film internal friction instrument adopts a cantilever beam sample clamping method to force the sample to vibrate at the resonant frequency to achieve the maximum amplitude, but this variable frequency measurement requires changing the clamping length, which cannot be achieved in a single variable temperature measurement. (3) The circuit design is complicated. To measure the weak vibration of the sample at the resonant frequency, the circuit design uses a high-frequency carrier to obtain the sample vibration capacitance change signal, which requires that the circuit design considers the interference of various distributed capacitances on the high-frequency signal, which also reduces the circuit stability and operability. (4) The variable temperature sample deforms and cannot work stably. The temperature rise during the test will cause the sample to deform. Since the excitation electrode or the collection electrode is very close to the far end of the sample, it is possible that the excitation electrode or the collection electrode will touch it, resulting in the inability to measure. The existence of the above problems has the potential to affect the accuracy of the quantitative data of the internal friction physical parameters.

[0010] There is no laser thin film internal friction instrument in the prior art that can be used to measure the elastic modulus, elastic modulus temperature coefficient, damping, etc. of the oxide film on the surface of the fuel cladding or ion irradiated materials, as well as material defect detection, including the study of defect types, concentrations and evolution mechanisms. Summary of the invention

[0011] In view of this, in order to overcome the defects of the prior art, an object of the present invention is to provide a laser thin film internal friction instrument.

[0012] In order to achieve the above object, the present invention adopts the following technical solutions:

[0013] A laser film internal friction instrument comprises a laser displacement sensor, a bottom plate, a lower cover fixed on the bottom plate, and an upper cover matched with the lower cover, wherein a cavity is formed between the bottom plate, the lower cover and the upper cover, wherein a sample fixing assembly, an excitation electrode, a heater and a shielding cover are arranged in the cavity, wherein an optical window corresponding to the laser displacement sensor is provided on the lower cover, wherein the heater is located in the shielding cover, wherein the shielding cover is used to cover the sample and the excitation electrode, wherein the shielding cover is provided with a through hole corresponding to the laser displacement sensor, wherein the excitation electrode faces the through hole, and wherein the sample is located between the through hole and the excitation electrode. The function of the excitation electrode is to drive the sample to vibrate, wherein a DC bias voltage and a variable frequency alternating voltage are applied between the sample to be tested and the excitation electrode, thereby forcing the sample to vibrate at a specific frequency, wherein a laser displacement sensor is used to collect the sample vibration signal, and obtain the waveform of the sample vibration, thereby obtaining parameters such as the damping and modulus of the material, and further obtaining information such as the microscopic defects of the material.

[0014] Preferably, the chamber is further provided with an excitation electrode moving assembly, including a slider, a screw rod driving the slider to move, and a motor driving the screw rod to rotate, the excitation electrode is fixed to the slider via a fixing plate, and the motor is fixed to the bottom plate. The moving assembly drives the excitation electrode to move, thereby adjusting the distance between the excitation electrode and the sample to be tested.

[0015] More preferably, a partition is provided in the cavity, the partition is fixed to the bottom plate by a fixing column, the shielding cover is fixed to the partition, and a slide groove for the fixed plate to move is provided on the partition. The excitation electrode moving assembly is located below the partition, and the shielding cover, the heater and the sample fixing assembly are located above the partition.

[0016] More preferably, an insulating ring is provided between the excitation electrode and the fixing plate.

[0017] Preferably, the sample fixing assembly includes a sample chuck, a support plate connected to the sample chuck, and a lifting mechanism for driving the support plate to move up and down, and the sample is fixed to the lower end of the sample chuck by a chuck screw. The lifting mechanism drives the support plate to move, thereby driving the up and down movement of the sample to be tested, and adjusting the position of the sample to be tested. In some embodiments, the sample chuck is also provided with a waist-shaped hole extending in the up and down direction of the sample chuck to adjust the position of the sample chuck fixed on the support plate.

[0018] Preferably, the heater is evenly distributed on the inner side of the shielding cover, and the heater extends along the axial direction of the shielding cover. The heater is in the shape of a rod, and is evenly distributed on the inner wall of the shielding cover, so that the temperature rise is more uniform, and it is irradiation heating, and the heating speed is fast. The shielding cover is used to prevent heat from radiating outside the device. In some embodiments, the laser film internal friction instrument can also add a water cooling system to control the temperature more accurately.

[0019] Preferably, the laser thin film internal friction instrument further comprises a lifting assembly for driving the upper cover body and the lower cover body to separate or fit together, and a vacuum pump group for evacuating the cavity.

[0020] More preferably, the bottom plate is provided with a vacuum valve for connecting with the vacuum pump group; the bottom plate is also provided with a shock absorbing component. The shock absorbing component can be provided under the bottom plate or between the cover body and the bottom plate.

[0021] Preferably, the laser displacement sensor is fixed on the bottom plate, and the laser displacement sensor, the optical window, the through hole and the excitation electrode are located on the same axis, so that the laser beam of the laser displacement sensor can hit the sample to be tested.

[0022] The sample to be tested is clamped and fixed in the vacuum chamber by the sample chuck. An excitation electrode is installed opposite the sample to drive the sample to vibrate. The heating system and water cooling system provide a high and low temperature environment around the sample. In order to prevent the influence of air damping on the amplitude and frequency of the high-frequency vibration of the sample, a vacuum unit is used to extract a high vacuum in the vacuum chamber during the test. The entire vacuum chamber is seismically isolated from the ground to eliminate the interference of mechanical vibration.

[0023] The present invention also provides a detection method using the laser thin film internal friction instrument as described above, which specifically comprises the following steps:

[0024] S1. Open the vacuum chamber: release the vacuum. When the vacuum state in the chamber changes to the atmospheric pressure state, start the lifting assembly to push the upper cover upward to open the chamber;

[0025] S2. Install the sample: Loosen the chuck screw, insert one end of the sample to be tested into the chuck gap, then tighten the screw to clamp the sample, and adjust the position of the excitation electrode;

[0026] S3. Vibration test: applying a bias voltage to the excitation electrode, and controlling the laser beam of the laser displacement sensor to irradiate the sample surface, and observing whether there is a vibration signal of the sample returned, and if there is a vibration signal, the vibration test is terminated; if there is no vibration signal, the position of the sample and the excitation electrode is adjusted until a vibration signal appears;

[0027] S4. Close the vacuum chamber: lift the assembly, move the upper cover down until it fits with the lower cover, the chamber is sealed, open the vacuum valve, start the vacuum pump group, and evacuate the chamber. -2 Pa and above high vacuum;

[0028] S5. Set parameters: set test temperature, test time, excitation amplitude, excitation frequency and other parameters, and start the measurement program;

[0029] S6: Testing: Collect vibration excitation signals and vibration signals, display vibration waveforms, calculate internal friction and elastic modulus values, obtain results and analyze them;

[0030] S7: Shut down the system: The test is finished, the test program is stopped, the bias power supply is adjusted to zero, and the control system is shut down.

[0031] Compared with the prior art, the present invention is beneficial in that the laser thin film internal friction instrument of the present invention has the advantages of high measurement accuracy, wide operating frequency, non-contact measurement to obtain material defect information, etc., and is very suitable for characterizing irradiation defects. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0033] Figure 1 is a stereogram of a laser thin film internal friction instrument in a preferred embodiment of the present invention;

[0034] Figure 2 It is a partial stereogram of the laser thin film internal friction instrument in the preferred embodiment of the present invention;

[0035] Figure 3 yes Figure 2 A top view of the

[0036] Figure 4 yes Figure 3 The cross-sectional view of AA in FIG.

[0037] Figure 5 yes Figure 2 A three-dimensional picture of the laser thin film internal friction instrument with the lower cover hidden;

[0038] Figure 6 yes Figure 5 A three-dimensional image of the laser thin film internal friction instrument behind the hidden partition;

[0039] Figure 7 This is a three-dimensional diagram of the shielding cover and heater in the laser thin film internal friction instrument;

[0040] Figure 8 It is a schematic diagram of the bending of a specimen under the action of a force perpendicular to the specimen axis;

[0041] Fig. 9 is a schematic diagram of the sample to be tested used in the calculation and analysis of Young's modulus in Example 3;

[0042] Fig.10 is a graph showing the results of the measurement of Young's modulus and internal friction of a stainless steel sheet with a variable cross section in Example 3;

[0043] In the attached drawings: laser displacement sensor-1, base plate-2, lower cover body-3, upper cover body-4, excitation electrode-5, heater-6, shielding cover-7, optical window-8, through hole-9, top hole-10, sample-11, slider-12, screw-13, motor-14, partition-15, fixing column-16, slide groove-17, fixing plate-18, sample chuck-19, support plate-20, lifting mechanism-21, chuck screw-22, lifting assembly-23, vacuum valve-24, waist round hole-25, frame-26. DETAILED DESCRIPTION

[0044] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0045] Example 1 Laser Thin Film Internal Friction Instrument

[0046] like Figure 1-7As shown, the laser thin film internal friction instrument of this embodiment includes a frame 26, a control system, a laser displacement sensor 1, a base plate 2, a lower cover body 3 fixed on the base plate 2, an upper cover body 4 matched with the lower cover body 3, a lifting component 23 for driving the upper cover body 4 to separate or fit with the lower cover body 3, and a vacuum pump group for evacuating the cavity. A cavity is formed between the base plate 2, the lower cover body 3 and the upper cover body 4. A sample 11 fixing component, an excitation electrode 5, a heater 6, a shielding cover 7 and a moving component for driving the excitation electrode 5 to move are arranged in the cavity. An optical window 8 corresponding to the laser displacement sensor 1 is opened on the lower cover body 3, the heater 6 is located in the shielding cover 7, the shielding cover 7 is used to cover the sample 11 and the excitation electrode 5, and a through hole 9 is opened in the shielding cover 7 corresponding to the laser displacement sensor 1. The excitation electrode 5 faces the through hole 9, and the sample 11 is located between the through hole 9 and the excitation electrode 5. A vacuum valve 24 for connecting to a vacuum pump group is provided on the bottom plate 2 ; a shock absorbing component is also provided on the bottom plate 2 , and the shock absorbing component can be arranged under the bottom plate 2 or between the lower cover 3 and the bottom plate 2 .

[0047] The laser displacement sensor using the laser Doppler effect not only has higher measurement accuracy (can reach 0.1nm displacement resolution), but the sensor can also be placed far away from the sample (non-contact, can generally be installed about 1m away from the sample), which facilitates the detection of defects in nuclear power materials caused by irradiation.

[0048] The function of the excitation electrode 5 is to drive the sample 11 to vibrate. By loading a DC bias and a variable frequency alternating voltage between the sample 11 to be tested and the excitation electrode, the sample 11 is forced to vibrate at a specific frequency. The laser displacement sensor 1 is used to collect the vibration signal of the sample 11, and the waveform of the vibration of the sample 11 is obtained, thereby obtaining parameters such as the damping and modulus of the material, and then obtaining the microscopic defect information of the material.

[0049] Among them, Figure 4 and 6 As shown, the excitation electrode moving assembly includes a slider 12, a lead screw 13 driving the slider 12 to move, and a motor 14 driving the lead screw 13 to rotate. The excitation electrode 5 is fixed to the slider 12 through a fixing plate 18. An insulating ring is provided between the excitation electrode 5 and the fixing plate 18. The motor 14 is fixed to the bottom plate 2. The excitation electrode 5 is driven to move by the moving assembly, so as to adjust the distance between the excitation electrode 5 and the sample to be tested 11.

[0050] like Figure 4-5 As shown, a partition 15 is provided in the cavity, the partition 15 is fixed to the bottom plate 2 through a fixing column 16, the shielding cover 7 is fixed to the partition 15, and a slide groove 17 is provided on the partition 15 for the movement of the fixing plate 18. The exciting electrode moving assembly is located below the partition 15, and the shielding cover 7, the heater 6 and the sample 11 fixing assembly are located above the partition 15.

[0051] like Figure 4-6 As shown, the fixing assembly of the sample 11 includes a sample chuck 19, a support plate 20 connected to the sample chuck 19, and a lifting mechanism 21 for driving the support plate 20 to move up and down. The sample 11 is fixed to the lower end of the sample chuck 19 by a chuck screw 22. The lifting mechanism 21 drives the support plate 20 to move, thereby driving the up and down movement of the sample to be tested 11 to adjust the position of the sample to be tested 11. In this embodiment, the sample chuck 19 is also provided with a waist-shaped hole 25 extending in the up and down direction of the sample chuck 19 to adjust the position of the sample chuck 19 fixed on the support plate 20. The top of the shielding cover 7 is also provided with a top hole 10 for the sample chuck to pass through.

[0052] like Figure 7 As shown, the heater 6 is evenly distributed on the inner side of the shielding cover 7, and the heater 6 extends along the axial direction of the shielding cover 7. The heater 6 is in the shape of a rod, and is evenly distributed on the inner wall of the shielding cover 7, so that the temperature rise is more uniform, and it is irradiation heating, and the heating speed is fast. The shielding cover 7 is used to prevent heat from radiating outside the device. In this embodiment, the laser thin film internal friction instrument also includes a water cooling system to control the temperature more accurately.

[0053] The laser displacement sensor 1 is fixed on the base plate 2. The laser displacement sensor 1, the optical window 8, the through hole 9 and the excitation electrode 5 are located on the same axis so that the laser beam of the laser displacement sensor 1 can hit the test sample 11 to measure the vibration of the sample 11.

[0054] In this embodiment, the sample 11 to be tested is clamped and fixed in the vacuum chamber by the sample chuck 19, and an excitation electrode 5 is installed opposite the sample 11 to drive the sample 11 to vibrate. The heating system and the water cooling system provide a high and low temperature environment around the sample 11. In order to prevent the influence of air damping on the high-frequency vibration amplitude and frequency of the sample 11, a vacuum unit is used to draw a high vacuum into the vacuum chamber during the test. The entire vacuum chamber is seismically isolated from the ground to eliminate the interference of mechanical vibration.

[0055] The laser thin film internal friction instrument of this embodiment can be used to measure the elastic modulus, elastic modulus temperature coefficient, damping, etc. of the oxide film on the surface of the fuel cladding or the ion irradiated material; material defect detection, including the study of defect types, concentrations and evolution mechanisms.

[0056] Embodiment 2 Detection method of laser film internal friction instrument

[0057] This embodiment provides a method for detecting material internal friction using the laser thin film internal friction instrument described in Embodiment 1, which specifically includes the following steps:

[0058] S1. Open the vacuum chamber: release the vacuum. When the vacuum state in the chamber changes to the atmospheric pressure state, start the lifting assembly to push the upper cover upward to open the chamber.

[0059] S2. Install the sample: Loosen the chuck screw, insert one end of the sample to be tested into the chuck gap, then tighten the screw to clamp the sample, and adjust the position of the excitation electrode.

[0060] S3. Vibration test: apply a bias voltage to the excitation electrode, and control the laser beam of the laser displacement sensor to irradiate the surface of the sample to observe whether there is a vibration signal returned from the sample. If there is a vibration signal, end the vibration test; if there is no vibration signal, adjust the position of the sample and the excitation electrode until a vibration signal appears.

[0061] S4. Close the vacuum chamber: lift the assembly, move the upper cover down until it fits with the lower cover, the chamber is sealed, open the vacuum valve, start the vacuum pump group, and evacuate the chamber. -2 Pa and above high vacuum.

[0062] S5. Set parameters: set test temperature, test time, excitation amplitude, excitation frequency and other parameters, and start the measurement program.

[0063] S6: Test: Collect vibration excitation signals and vibration signals, display vibration waveforms, calculate internal friction and elastic modulus values, obtain results and analyze them.

[0064] S7: Shut down the system: After the test is finished, stop the test program, adjust the bias power supply to zero, and shut down the control system. The control system may specifically include a displacement processor, a temperature controller, a data acquisition module, a calculation module, and the like.

[0065] The basic test principle is as follows: a DC bias and a variable frequency alternating voltage are loaded between the test sample and the excitation electrode to force the sample to vibrate at a specific frequency. A laser displacement sensor is used to collect the sample vibration signal to obtain the entire waveform of the sample vibration, thereby obtaining parameters such as the damping and modulus of the material. At the same time, parameters such as the heating current are controlled according to the collected temperature data, thereby obtaining information such as the microscopic defects of the material.

[0066] Example 3 Calculation and analysis of Young's modulus of laser film internal friction instrument test sample

[0067] The film internal friction tester uses a sheet sample with a thickness of 50-300μm, a width of 4-6mm, and a length of 15-50mm. Assuming that the sample is subjected to a force perpendicular to the sample axis, the sample undergoes elastic bending, as shown in the attached Figure 8 As shown in the figure, due to the stiffness of the sample, the bending deformation is restored to the equilibrium state, causing the sample to vibrate in the direction perpendicular to the axis.

[0068] The material obeys Hooke's law, and the transverse vibration equation of the specimen can be expressed as follows:

[0069]

[0070] In the above formula, A is the cross-sectional area of ​​the sample; ρ is the density of the sample; E is the Young's constant of the sample; I is the moment of inertia of the cross section of the sample relative to the neutral plane; g is the acceleration due to gravity.

[0071] Solving the above formula, we can get the calculation formula of Young's modulus of sheet specimen:

[0072]

[0073] Where, l is the length of the sample vibration; d is the thickness of the sample; f is the fundamental frequency (first-order resonance frequency) of the sample vibration.

[0074] For the single-end clamped specimens mentioned above, the clamp effect will have a certain impact on the measurement. In addition to introducing internal stress, the clamp effect mainly affects the measurement accuracy of the vibration part of the specimen's effective length. By differentiating the Young's modulus calculation formula, the error analysis formula of Young's modulus can be obtained:

[0075]

[0076] For a certain sample, when the temperature is constant, the density is a constant. The measurement error of density can be ignored; the thickness is averaged after multiple measurements, and the error is very small; the measurement of resonance frequency is converted from electrical signals, and the error is very small. Therefore, the measurement error of length has the most significant impact on the measurement results.

[0077] There are two ways to reduce or eliminate the effect of the error in the effective length of the specimen on the final measurement result:

[0078] (1) Use a specimen with a variable cross section, such as Fig. 9 shown.

[0079] a) The thickness of the sample remains unchanged and the width ratio W2 / W1 is changed

[0080] b) The width of the specimen remains constant and the thickness ratio H2 / H1 is changed.

[0081] like Fig.10 As shown in the figure, the Young's modulus of a stainless steel sheet (80 μm thick, measured in air) was measured using the variable cross-section method. As the ratio of the variable cross-section increases, the apparent internal friction becomes smaller and smaller, and the Young's modulus (vibration frequency) gradually increases, and finally tends to a stable value.

[0082] (2) Using different length measurements

[0083] As the length increases, the measured Young's modulus gradually increases and finally tends to a saturation value (true value). Because it is getting smaller and smaller, according to the error analysis formula, the error of the Young's modulus is also getting smaller and smaller.

[0084] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the contents of the present invention and implement them accordingly. They cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A laser thin film internal friction instrument, characterized in that: The laser displacement sensor comprises a bottom plate, a lower cover body fixed on the bottom plate, and an upper cover body matched with the lower cover body, wherein a cavity is formed between the bottom plate, the lower cover body and the upper cover body, wherein a sample fixing assembly, an excitation electrode, a heater and a shielding cover are arranged in the cavity, wherein an optical window corresponding to the laser displacement sensor is provided on the lower cover body, wherein the heater is located in the shielding cover, wherein the shielding cover is used to cover the sample and the excitation electrode, wherein a through hole is provided in the shielding cover corresponding to the laser displacement sensor, wherein the excitation electrode faces the through hole, and wherein the sample is located between the through hole and the excitation electrode; The sample fixing assembly includes a sample chuck, a support plate connected to the sample chuck, and a lifting mechanism for driving the support plate to move up and down, and the sample is fixed to the lower end of the sample chuck by a chuck screw; the laser thin film internal friction instrument also includes a lifting assembly for driving the upper cover body and the lower cover body to separate or fit together, and a vacuum pump group for evacuating the cavity; a vacuum valve for connecting to the vacuum pump group is also provided on the bottom plate; a shock absorbing assembly is also provided on the bottom plate; A DC bias and a variable frequency alternating voltage are applied between the sample to be tested and the excitation electrode, forcing the sample to vibrate at a specific frequency.

2. A laser thin film internal friction instrument according to claim 1, characterized in that: The cavity is also provided with an excitation electrode moving assembly, including a slider, a lead screw driving the slider to move, and a motor driving the lead screw to rotate. The excitation electrode is fixed to the slider via a fixing plate, and the motor is fixed to the bottom plate.

3. A laser thin film internal friction instrument according to claim 2, characterized in that: A partition is arranged in the cavity, the partition is fixed to the bottom plate through a fixing column, the shielding cover is fixed to the partition, and a sliding groove for the fixing plate to move is provided on the partition.

4. A laser thin film internal friction instrument according to claim 2, characterized in that: An insulating ring is arranged between the excitation electrode and the fixing plate.

5. The laser thin film internal friction instrument according to claim 1, characterized in that: The heaters are evenly distributed on the inner side of the shielding cover, and the heaters extend along the axial direction of the shielding cover.

6. The laser thin film internal friction instrument according to claim 1, characterized in that: The laser displacement sensor is fixed on the bottom plate, and the laser displacement sensor, the optical window, the through hole and the excitation electrode are located on the same axis.

7. A method for detecting material internal friction using a laser thin film internal friction instrument as claimed in claim 1, characterized in that: The steps include: S1. Open the vacuum chamber: release the vacuum, start the lifting assembly, push the upper cover upward, and open the chamber; S2. Install the sample: Loosen the chuck screw, insert one end of the sample to be tested into the gap of the sample chuck, and then tighten the chuck screw to clamp the sample; S3. Vibration test: applying a bias voltage to the excitation electrode, and controlling the laser beam of the laser displacement sensor to irradiate the sample surface, observing whether there is a vibration signal of the sample returned, and ending the vibration test if there is a vibration signal; if there is no vibration signal, the position of the sample and the excitation electrode is adjusted until a vibration signal appears; S4. Close the vacuum chamber: Start the lifting assembly, move the upper cover down until it fits with the lower cover, the chamber is sealed, open the vacuum valve, start the vacuum pump group, and evacuate the chamber; S5. Set parameters: set test parameters and start the test program; S6: Testing: Collect vibration signals, calculate internal friction and elastic modulus values, obtain results and analyze them; S7: Shut down the system: The test is finished, the test program is stopped, the bias power supply is adjusted to zero, and the control system is shut down.

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