Laser-driven high-strain-rate micro / nano impact indentation test method

Abstract

The application relates to a laser-driven high-strain-rate micro-nano impact indentation testing method, and belongs to the field of precision testing. The method comprises the following steps: (1) determining the laser impact position of an elastic body surface, and laying an absorbing layer at the corresponding position; (2) laying a transparent constraint layer on the surface of the absorbing layer, and constructing an impact component composed of a pressure head, an elastic body, an absorbing layer and a constraint layer; (3) adjusting the position of the impact component so that the impact component is located on the laser focal plane, and meanwhile, the laser spot, the pressure head and the sample impact area are coaxial; (4) adjusting the position of the sample so that the distance between the sample and the pressure head tip is 0-1 mm; (5) adjusting the parameters of the laser and the high-speed camera, synchronously starting the laser and the high-speed camera, and performing laser-driven high-strain-rate micro-nano impact indentation testing, and meanwhile, the pressure head pressing-in and pressing-out processes are photographed in real time, and the speed characteristics are measured. The application is realized by comprehensively combining the laser impact and elastic deformation mechanisms, is used for testing in the microscale, and has a high strain rate.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of precision testing, in particular to a test method for generating high-strain-rate micro / nano-impact indentation by laser-induced plasma and driving elastic deformation to impact the material with a pressure head. Compared with conventional impact test methods such as Hopkinson pressure bar and pendulum impact, the method is an impact test at the microscale, which has the advantages of high flux, high strain rate and high safety factor. BACKGROUND

[0002] High-strain-rate and high-speed impact often leads to rapid changes in internal temperature, stress and other parameters of materials. In the fields of trans-atmospheric hypersonic vehicles, aircraft engines, gas turbines and nuclear power equipment, the core components of equipment are often subjected to high-speed impact, which is one of the important causes of performance weakening or even failure and damage of key components of equipment. Therefore, studying the micro-deformation and damage mechanism of materials under high-strain-rate impact load is the prerequisite for optimizing material design, improving material performance and ensuring equipment safety, and is also a frontier scientific problem to be solved in the field.

[0003] Compared with mechanical property tests of materials under quasi-static conditions, the parameters obtained under high-speed impact conditions have better ability to describe the performance of materials under actual working conditions. Unfortunately, although several impact test methods have been developed, they have different limitations in terms of upper limit of strain rate, test scale, test flux and safety. For example, Hopkinson pressure bar, laser-driven flyer technology, pendulum impact and ballistic impact methods are usually performed on macro-scale samples (a few millimeters to a few hundred millimeters) and require high impact speed (hundreds of meters per second) to generate high strain rate. The strain rate provided by the test results is generally less than 10 4 s -1 The electromagnetic / piezoelectric-driven micro / nano-impact indentation test method has the advantages of high flux, safety and microscale, but its strain rate is usually less than 10 3 s -1 , and it needs to be combined with high-precision and high-sampling-frequency sensing and acquisition equipment and complex data post-processing procedures to complete the test. Laser impact, as a fast, direct energy transfer method, has been widely used in metal processing and surface strengthening fields. The test method proposed in the present application combines laser impact and elastic deformation mechanisms, effectively solves the problems of low strain rate and macro-scale test scale faced by conventional test methods, and provides a new method for studying the micro-deformation and damage mechanism of materials under high-strain-rate impact load. SUMMARY

[0004] The application aims to provide a laser-driven high-strain-rate micro-nano impact indentation testing method, and solves the problems in the prior art.

[0005] The above object of the application is achieved by the following technical scheme:

[0006] The laser-driven high-strain-rate micro-nano impact indentation testing method comprises the following steps:

[0007] (1) determining the laser impact position on the surface of the elastic body, and laying an absorbing layer at the corresponding position;

[0008] (2) placing a transparent constraint layer on the surface of the absorbing layer, and constructing an impact component composed of a pressure head, an elastic body, an absorbing layer and a constraint layer;

[0009] (3) adjusting the position of the impact component so that it is located on the laser focal plane, and the laser spot, the pressure head and the sample impact position are coaxial;

[0010] (4) adjusting the position of the sample so that the distance between the sample and the tip of the pressure head is 0-1 mm;

[0011] (5) adjusting the parameters of the laser and the high-speed camera, starting the laser and the high-speed camera synchronously, and performing high-strain-rate micro-nano impact indentation testing based on laser driving, while photographing the pressure head in the process of pressing in and pressing out in real time and measuring the speed characteristics.

[0012] The laser ablates the absorbing layer and generates plasma with high temperature and high pressure, the expansion of the plasma is constrained by the constraint layer and the elastic body, so that a high-intensity shock wave is transmitted to the elastic body, and the elastic body is impacted to produce elastic deformation, the pressure head is driven to impact the test material through the conversion of elastic potential energy to kinetic energy, and the high-strain-rate impact indentation testing is completed.

[0013] The pressure head in step (2) comprises a standard Berkovich diamond pressure head, a standard Vickers diamond pressure head and a cylindrical diamond pressure head with different diameters, the pressure head is composed of a diamond tip and a base, the diameter of the base is 0-5 mm, the height is 1-2 mm, and the weight is 0.001-0.2 g.

[0014] The elastic body material in step (2) is a metal elastic sheet.

[0015] The constraint layer in step (2) is a transparent acrylic plate with a thickness of 1-10 mm or BK-7 glass with high impact impedance.

[0016] The pressing and ejecting process in the step (5) includes plasma generation, elastic deformation of the elastomer, pressing head pressing and ejecting.

[0017] The connecting mode between the pressing head and the elastomer includes adhesion using special metal adhesive, welding and mechanical connection.

[0018] The thickness of the absorbing layer is in the range of 50-200 mu m.

[0019] The strain rate range that can be realized by the laser-driven high-strain-rate micro-nano impact indentation test method is 10 3 -10 6 s -1 .

[0020] The laser-driven high-strain-rate micro-nano impact indentation test method has the beneficial effects that by comprehensively considering the laser impact and the elastic deformation mechanism, a microscale, high-strain-rate, safe and efficient micro-nano impact indentation test method is obtained, the problems of macroscopic test, low strain rate, low test throughput and low safety factor faced by conventional test methods such as Hopkinson pressure bar, pendulum and ballistic impact are effectively solved, and a new method is provided for the research on the micro-deformation and damage mechanism of materials under high-strain-rate impact load. BRIEF DESCRIPTION OF DRAWINGS

[0021] The drawings described herein are used to provide further understanding of the present application, and constitute a part of the present application, the schematic examples of the present application and the description thereof are used to explain the present application, and do not constitute improper limitation on the present application.

[0022] Figure 1 It is a schematic diagram of laser-driven high-strain-rate micro-nano impact indentation test;

[0023] Figure 2 It is the strain rate when the laser energy is 1400 mJ and the Vickers indenter is used to impact the amorphous alloy;

[0024] Figure 3 After the laser energy is 1400 mJ and the Vickers indenter is used to impact the amorphous alloy, the residual surface morphology and cross-section profile curve diagram of the sample are shown;

[0025] Figure 4 After the laser energy is 1400 mJ and the Vickers indenter is used to impact the amorphous alloy, the residual surface morphology and cross-section profile curve diagram of the sample are shown.

[0026] Figure 5 After the laser energy is 1400 mJ and the Vickers indenter is used to impact the amorphous alloy, the residual surface morphology and cross-section profile curve diagram of the sample are shown.

[0027] In the figure, 101-test sample; 102-elastic body before and after deformation; 103-laser energy absorption layer; 104-BK-7 glass or acrylic plate with high impact resistance; 105-diamond indenter; 106-laser; 107-high-speed camera; 108-indenter diamond tip; 109-indenter base. DETAILED DESCRIPTION

[0028] The detailed content of the present application and its specific implementation will be further illustrated below in combination with the drawings. Referring to Figures 1 to 5 The laser-driven high-strain-rate micro / nano indentation impact test method of the present application, as shown, comprises the following steps:

[0029] (1) Determine the laser impact position on the surface of the elastic body, and lay the absorption layer at the corresponding position;

[0030] (2) Place a transparent constraint layer on the surface of the absorption layer to construct an impact component composed of an indenter, an elastic body, an absorption layer, and a constraint layer;

[0031] (3) Adjust the position of the impact component to be located at the laser focal plane while making the laser spot, the indenter, and the sample impact position coaxial;

[0032] (4) Adjust the position of the sample to make the distance between the sample and the indenter tip 0-1 mm;

[0033] (5) Adjust the parameters of the laser and the high-speed camera, start the laser and the high-speed camera synchronously, and perform high-strain-rate micro / nano impact indentation test based on laser driving, while real-time shooting the indenter pressing-in and pressing-out process and measuring the speed characteristics.

[0034] The laser ablates the absorption layer and generates high-temperature and high-pressure plasma, the plasma expansion is constrained by the constraint layer and the elastic body, which makes the high-intensity shock wave transmit to the elastic body and impact the elastic body to make the elastic body produce elastic deformation, and through the conversion of elastic potential energy to kinetic energy, the indenter impacts the test material, thereby completing the high-strain-rate impact indentation test.

[0035] The indenter in step (2) includes a standard Berkovich diamond indenter, a standard Vickers diamond indenter, and a cylindrical diamond indenter with different diameters, and the indenter is composed of a diamond tip and a base, the base has a diameter of 0-5 mm, a height of 1-2 mm, and a weight of 0.001-0.2 g.

[0036] The elastic body material in step (2) is a metal elastic sheet.

[0037] The constraint layer in step (2) is a transparent acrylic plate with a thickness of 1-10 mm or BK-7 glass with high impact resistance.

[0038] The pressing and ejecting process in the step (5) includes plasma generation, elastic deformation of the elastomer, pressing of the indenter and ejecting.

[0039] The connecting mode between the indenter and the elastomer includes adhesion using special metal adhesive, welding and mechanical connection.

[0040] The thickness of the absorbing layer is in the range of 50-200 microns.

[0041] The strain rate range that can be achieved by the laser-driven high-strain-rate micro-nano impact indentation test method is 10 3 -10 6 s -1 .

[0042] Embodiment:

[0043] Referring to Figure 1 , it is a schematic diagram of laser-driven high-strain-rate micro-nano impact indentation test. First, the laser impact position on the surface of the elastomer is determined, and the absorbing layer is laid on the corresponding position. The absorbing layer is a black double-sided adhesive tape with double-sided adhesion, and the thickness is 90 microns. A transparent constraint layer is laid on the surface of the absorbing layer to construct an impact component composed of a diamond indenter, an elastomer, an absorbing layer and a constraint layer. The position of the impact component is adjusted so that it is located on the laser focal plane and the laser spot, the indenter and the sample impact position are coaxial. The position of the sample is adjusted so that the distance between the sample and the tip of the indenter is 0-1 mm. The parameters of the laser and the high-speed camera are adjusted, and the laser and the high-speed camera are started synchronously to perform high-strain-rate micro-nano impact indentation test based on laser driving, and the pressing and ejecting process of the indenter is photographed in real time and the speed characteristics are measured. The mechanism of the present application is that the laser (106) ablates the absorbing layer (103) and generates high-temperature and high-pressure plasma. The expansion of the plasma is constrained by the constraint layer (104) and the elastomer (102), so that the high-intensity shock wave is transmitted to the elastomer (102) and then impacts the elastomer (102) to make the elastomer (102) produce elastic deformation. Through the conversion of elastic potential energy to kinetic energy, the indenter (105) impacts the test material (101) to complete the high-strain-rate impact indentation test.

[0044] Referring to Figure 2 , it is the strain rate when the glass indenter impacts amorphous alloy when the laser energy is 1400 mJ. It can be seen that the strain rate level is 10 5 s -1 >10 4 s -1 , compared with the conventional impact test method, the strain rate obtained by the present method is increased by one order of magnitude.

[0045] Referring to Figure 3 ,Figure 4 and Figure 5 The residual surface morphology of the samples obtained after laser-driven micro / nano impact indentation test of amorphous alloy, 1050 aluminum alloy and high-entropy alloy after strengthening by spraying, using a Brinell or a Vickers indenter, with a laser energy of 1400 mJ, is shown in FIGS. 8 and 9. It can be seen that the residual surface morphology of the samples is obviously different from that under quasi-static indentation test.

[0046] As can be seen from the example results, the laser-driven micro / nano impact indentation test method based on the present application effectively solves the problems of low strain rate and macroscopic test scale faced by conventional test methods by combining laser impact and elastic deformation mechanisms, and provides a new method for studying the micro-deformation and damage mechanism of materials under high-strain-rate impact load.

[0047] The above only describes the preferred examples of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made to the present application shall be included in the protection scope of the present application.

Claims

1. A method of laser-driven high-strain-rate micro / nano impact indentation testing, characterized in that, The method comprises the following steps: (1) determining the laser impact position on the elastomer surface and laying the absorbing layer at the corresponding position; (2) placing the transparent constraint layer on the surface of the absorbing layer to build the impact component composed of the indenter, the elastomer, the absorbing layer and the constraint layer; (3) adjusting the position of the impact component to be located at the laser focal plane while making the laser spot, the indenter and the sample impact position coaxial; (4) adjusting the position of the sample to make the distance between the sample and the tip of the indenter 0-1 mm; (5) adjusting the parameters of the laser and the high-speed camera, starting the laser and the high-speed camera synchronously, and performing the high-strain-rate micro / nano-impact indentation test based on laser driving, while photographing the process of the indenter pressing in and pressing out and measuring the speed characteristics in real time; The mechanism is that the laser ablates the absorbing layer and generates plasma with high temperature and high pressure, the expansion of the plasma is constrained by the constraint layer and the elastomer, so that the high-intensity shock wave is transmitted to the elastomer and the elastomer is impacted to produce elastic deformation, the elastic potential energy is converted into kinetic energy to drive the indenter to impact the test material, so as to complete the high-strain-rate impact indentation test; The indenter in step (2) comprises a standard Berkovich diamond indenter, a standard Vickers diamond indenter and a cylindrical diamond indenter with different diameters, the indenter is composed of a diamond tip and a base, the diameter of the base is 0-5 mm, the height is 1-2 mm, and the weight is 0.001-0.2 g; The elastomer material in step (2) is a metal spring piece; The constraint layer in step (2) is a transparent acrylic plate with a thickness of 1-10 mm or BK-7 glass with high impact impedance; The pressing in and pressing out process in step (5) includes plasma generation, elastic deformation of the elastomer, pressing in and pressing out of the indenter; the measured speed includes the elastic deformation speed, the impact speed of the indenter and the rebound speed.

2. The method of claim 1, wherein the laser-driven high-strain-rate micro- nanoindentation test method is characterized by: The connection mode between the indenter and the elastomer includes using metal adhesive, welding and mechanical connection.

3. The method of claim 1, wherein the laser-driven high-strain-rate micro- nano-impact indentation test method is characterized by: The thickness of the absorbing layer is in the range of 50-200 μm.

4. The method of claim 1, wherein the laser-driven high-strain-rate micro- nano-impact indentation test method is characterized by: The method achieves a strain rate range of 10 3 -10 6 s -1 .

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