Method and device for testing deformation of micro-nano indentation contact area

Abstract

The present application relates to a kind of micro-nano indentation contact area deformation test method and device, belong to material microscopic mechanical property testing technical field, its surface to be tested sample is coated with speckle, and directly contact with speckle is used to transparent indenter, the nanometer speckle between indenter and sample is observed by optical microscope, the three-dimensional deformation behavior information of contact area in the process of micro-nano indentation test is obtained, the phenomenon such as crack, extrusion, slip band generation in the existing micro-nano indentation test can be in-situ characterization, and the three-dimensional process model of the deformation behavior of material under indenter is constructed, the method is strong in operability, solve the problem that existing in-situ observation means cannot directly characterize the deformation of contact area in the process of block sample indentation test, improve the understanding of the micro-nano contact mechanical behavior of various materials.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of material micro-mechanical property testing, in particular to a deformation characterization test of a direct contact area between an indenter and a test piece in a indentation test, and specifically relates to a micro-nano indentation contact area deformation test method and device for. BACKGROUND

[0002] The micro-nano indentation test technology is based on real-time acquisition of the load and depth of the indenter pressed into the sample, and then obtains the hardness, elastic modulus and other parameters of the material from the load-depth curve, in combination with the deformation of the material in the indentation area, to study the performance and microstructure evolution law of the material under the action of load, with the characteristics of high resolution of test parameters, simple and convenient sample preparation, and rich types of test parameters, gradually becoming one of the mainstream means for testing the micro-mechanical properties of materials.

[0003] However, the contact area between the indenter and the test piece in the micro-nano indentation test process is micron-scale. In order to obtain the deformation behavior of the material during the test, the existing scanning electron microscope is used to observe the test area, which can only observe the periphery of the contact area between the indenter and the test piece at a certain angle with the indenter, and the material deformation behavior cannot be observed in real time, and the deformation process of the material under the indenter cannot be constructed, and the material deformation in the contact area of the indentation cannot be characterized.

[0004] Therefore, a method for real-time reflecting the deformation process and strain distribution of the micro-nano indentation contact area is needed, which will greatly improve the understanding of the deformation behavior of the material under the action of the indenter, and can directly characterize the different behaviors of different materials under the action of the load, increase the information acquisition dimension of the micro-nano indentation test, and have great significance for the further development of the micro-nano indentation test technology. SUMMARY

[0005] The purpose of the present application is to provide a micro-nano indentation contact area deformation test method, which synchronously acquires the deformation information of the material in the indentation test process, and draws a strain distribution map of the contact area, and then tests and characterizes the deformation of the micro-nano indentation contact area.

[0006] The purpose of the present application is achieved by the following technical solutions:

[0007] A micro-nano indentation contact area deformation test method, comprising the following steps:

[0008] Step 1: coating the surface of the test piece with nano speckle;

[0009] Step 2: fixing the test piece coated with nano speckle on the stage of the driven indentation tester, and making the test piece located directly below the transparent indenter;

[0010] Step three, adjust the optical microscope so that the objective lens can observe the lower tip of the light-transmitting indenter, at this time the initial position of the light-transmitting indenter;

[0011] Step four, move away the light-transmitting indenter, adjust the position of the sample to be tested in the vertical direction so that the objective lens can observe the surface of the sample to be tested, adjust the position of the sample to be tested in the horizontal direction, set the indentation area as the area in the field of view of the objective lens, take the original speckle image N0 in the indentation area, and move the light-transmitting indenter back to the initial position;

[0012] Step five, set m a short time holding segment with a length of t During the indentation test, after starting the test, the lower tip of the light-transmitting indenter and the contact area of the sample to be tested are scanned layer by layer in each short time holding segment by using the optical microscope, and the nanospeckle plane images N1 to N m are generated and obtained. i The first speckle image is N i .

[0013] Step six, obtain the nanospeckle plane images N1 to N m of the contact area, and a deformation distribution diagram compared with the original speckle image N0, the distribution diagram has m .

[0014] Step seven, process the deformation distribution diagram through the area function of the light-transmitting indenter, and obtain a three-dimensional deformation distribution diagram conforming to the actual situation of the indentation.

[0015] As a more preferred technical scheme of the present application, the area function of the light-transmitting indenter is measured by an atomic force microscope and fitted, and the expression form of the fitting result is A ( h c ) = C 0 h c 2 + C 1 h c + C 2 h c 1 / 2 + C 3 h c 1 / 4 + ··· + C 8 h c 1 / 128 , which means that in the case that the light-transmitting indenter is vertically placed, the cross-sectional area at the position of h c from the tip of the indenter is A .h c )。

[0016] As a better technical scheme of the application: in step four, the optical microscope light path is focused on the point below the light-transmitting indenter tip, and the focal length is gradually changed to collect images layer by layer upwards until the light-transmitting indenter is separated from the test piece, and the images collected step by step are spliced to obtain the nanospeck planar images N1 to N m .

[0017] The application also aims to provide a micro-nano indentation contact area deformation testing device, which comprises a light-transmitting indenter 2 that can move in a horizontal plane, an optical microscope, a test piece 3, a carrier table 4 that can move in a three-dimensional space, a nanospeck planar image acquisition module, a digital speck processing module and a three-dimensional deformation distribution map acquisition module; the light-transmitting indenter 2 is placed below the objective lens 1 of the optical microscope, the test piece 3 coated with nanospecks is fixed above the carrier table 4, and during the indentation process of the light-transmitting indenter 2 and the test piece 3, the objective lens 1 of the optical microscope passes through the transparent light-transmitting indenter 2 from above to perform layer-by-layer scanning on the contact area between the tip below the light-transmitting indenter and the test piece by using the optical microscope in each short-time holding section; the nanospeck planar image acquisition module is used to generate and acquire nanospeck planar images N1 to N m of the contact area; the digital speck processing module is used to process the acquired nanospeck planar images N1 to N m of the contact area into deformation distribution maps compared with the original speck image N0, and the deformation distribution maps have a total of m ; and the three-dimensional deformation distribution map acquisition module is used to post-process the deformation distribution maps through the area function of the light-transmitting indenter.

[0018] The beneficial effects are as follows:

[0019] The application provides a testing method, which can directly test and characterize the deformation behavior of a material under the action of an indenter during an indentation test, the indenter and the specks are directly contacted after the surface of a test piece is coated with nanospecks, the contact area between the indenter and the test piece in the micro-nano indentation test can be directly observed, the deformation information of the material in the indentation test can be synchronously acquired, the strain distribution map of the contact area can be drawn during the indentation test, the deformation of the micro-nano indentation contact area is further tested and characterized, a technical method is provided for obtaining the deformation information of the material in the micro-nano indentation test, the characterization range of the indentation test technology is expanded, and the practicability is high. BRIEF DESCRIPTION OF DRAWINGS

[0020] The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the application and together with the description serve to explain the application. In the drawings:

[0021] Figure 1 A schematic diagram of the surface coated nano-speck test piece of the present application;

[0022] Figure 2 A schematic diagram of the structure of the test device used in the present application;

[0023] Figure 2 B a schematic diagram of the relationship between the micro-nano indentation indenter and the test piece of the present application;

[0024] Figure 3 A schematic diagram of the optical microscope observation results during the indentation loading process of the present application;

[0025] Figure 4 A schematic diagram of the effect of converting the nano-speck planar image into a three-dimensional image of the present application;

[0026] Figure 5 A schematic diagram of the corresponding relationship of any point when converting the nano-speck planar image into a three-dimensional image of the present application;

[0027] Figure 6 A schematic diagram of the structure of the test device used in the present application, including a light-transmitting indenter 2 that can move in the horizontal plane, an optical microscope, a test piece 3 to be tested, and a stage 4 that moves in the three-dimensional space. DETAILED DESCRIPTION

[0028] The detailed content of the present application and its specific embodiments will be further described below in conjunction with the drawings.

[0029] The present application provides a test device for the deformation of the contact area of a micro-nano indentation, including a light-transmitting indenter 2 that can move in the horizontal plane, an optical microscope, a test piece 3 to be tested, a stage 4 that moves in the three-dimensional space, a nano-speck planar image acquisition module, a digital speck processing module, and a three-dimensional deformation distribution graph acquisition module; the light-transmitting indenter 2 is placed below the objective lens 1 of the optical microscope, the nano-speck test piece 3 to be tested is fixed above the stage 4, and during the indentation process of the light-transmitting indenter 2 and the test piece 3 to be tested, the objective lens 1 of the optical microscope passes through the transparent light-transmitting indenter 2 from above to perform layer-by-layer scanning on the contact area between the tip below the light-transmitting indenter and the test piece using the optical microscope in each short time holding section; the nano-speck planar image acquisition module is used to generate and acquire the nano-speck planar images N1 to N m of the contact area; the digital speck processing module is used to process the acquired nano-speck planar images N1 to N mThe deformation distribution map compared to the original speckle image N0, this distribution map has a total of m The three-dimensional deformation distribution map acquisition module is used to post-process the deformation distribution map using the area function of the light-transmitting pressure head.

[0030] The testing method based on the aforementioned micro / nano indentation contact area deformation testing device constructs a three-dimensional process model of the material deformation behavior beneath the indenter in the contact area between the indenter and the specimen during indentation loading. (See also...) Figures 1 to 6 As shown, the procedure includes the following steps:

[0031] Step 1: Clean the surface of the test piece 3 thoroughly, and then apply a nano-speckled coating to its surface, such as... Figure 1 As shown;

[0032] Step 2: Fix the test piece 3, coated with speckle pattern, onto the stage 4 of the lower-drive indenter. Adjust the spatial position of the stage 4 so that the test piece 3 is directly below the light-transmitting indenter 2. Figure 1 As shown;

[0033] Step 3: Adjust the relative position between the objective lens 1 and the light-transmitting pressure head 2 of the optical microscope so that the central part of the light-transmitting pressure head 2 can be observed through the objective lens 1 of the optical microscope. Adjust the focal length of the optical microscope so that the lower tip of the light-transmitting pressure head 2 can be observed through the objective lens 1. This is the initial position of the light-transmitting pressure head 2.

[0034] Step 4: Remove the light-transmitting indenter 2, adjust the position of the test piece 3 in the vertical direction so that the surface of the test piece 3 can be observed through the objective lens 1 of the optical microscope, adjust the position of the test piece 3 in the horizontal plane, set the indentation area in the field of view of the microscope, take a speckle image N0 in the indentation area, move the stage 4 down by a few micrometers, and move the light-transmitting indenter 2 back to the initial position.

[0035] Step 5: Perform an indentation test on the test piece 3. The positional relationship between the light-transmitting indenter 2 and the test piece 3 during the indentation process is as follows: Figure 2 As shown, A is the left view and B is the top view. The settings were configured before the indentation test. m Each duration is t During the short-time load holding period of the test, the contact area was scanned layer by layer using an optical microscope within each short-time load holding period to generate and acquire nano-speckled planar images N1 to N of the area in close contact with the indenter. m , among which, the i N speckle images i ;

[0036] Step Six: Compare the original speckle image N0 obtained in Step Four with the image obtained in Step Five during the indentation test. m Zhang's spotted images N1 to Nm Import digital speckle processing software, according to the speckle image difference between adjacent short time load holding segments, obtain the deformation distribution diagram of the contact area between the test piece 3 and the transparent indenter 2 at different short time load holding segments in the micro / nano indentation test process compared with the initial state N0, the distribution diagram has m ;

[0037] Step seven, according to the area function of the transparent indenter 2 used, post-process the m deformation cloud diagram obtained in step six, so that it is processed from a planar digital speckle picture to a three-dimensional deformation distribution diagram of the actual composite indentation through the area function of the indenter used, as shown in Figure 4 . The area function of the transparent indenter 2 can be measured by an atomic force microscope and fitted, and the expression form of the fitting result is A ( h c ) = C 0 h c 2 + C 1 h c + C 2 h c 1 / 2 + C 3 h c 1 / 4 + ··· + C 8 h c 1 / 128 , which means that the cross-sectional area at the position of h c from the tip of the indenter is A ( h c ), since the test piece 3 is closely attached to the transparent indenter 2 in the contact area during the indentation process, the fitting result of the area function of the indenter can be used to process the planar digital speckle picture into a three-dimensional deformation distribution diagram, as shown in Figure 5 .

[0038] Example 1

[0039] Step one, nano speckle coating is obtained by nano speckle coating on the surface of the test piece 3 with a smooth surface in a gas phase deposition manner, which is randomly distributed on the surface of the test piece and firmly bonded thereto;

[0040] Step two, the test piece 3 coated with nano speckles is adhered to the top of the stage 4 with paraffin, and the stage 4 is moved in space so that the test piece 3 is directly below the transparent indenter 2;

[0041] Step 3: Adjust the relative position between the objective lens 1 and the light-transmitting pressure head 2 of the optical microscope, including their coaxiality and vertical distance, so that the central part of the light-transmitting pressure head 2 can be observed through the objective lens 1 of the optical microscope. Further adjust the focal length of the optical microscope so that the lower tip of the light-transmitting pressure head 2 can be observed through the objective lens 1. Since a Vickers pressure head is used, during the process of adjusting the focal length from top to bottom, the focus should be gradually focused along the four edges below the Vickers pressure head to the intersection point in the field of view of the microscope. This point is the lower tip of the light-transmitting pressure head 2.

[0042] Step 4: To determine the indentation area, move the light-transmitting indenter 2 horizontally from its current position A to a more distant position B to prevent interference when adjusting the position of the test piece 3 later. Adjust the position of the test piece 3 in the vertical direction so that the surface of the test piece 3 can be observed through the objective lens 1 of the optical microscope. At this time, the surface of the test piece 3 and the lower tip of the light-transmitting indenter 2 are roughly on the same horizontal plane. Adjust the position of the test piece 3 in the horizontal plane and observe the surface of the test piece 3 through the objective lens 1 of the optical microscope. The center of the observation position is the subsequent indentation position. Take a speckle image N0 in the indentation area. Move the stage 4 downward by 5 μm and move the light-transmitting indenter 2 back to the initial position A.

[0043] Step 5: Drive the stage 4 to carry the test piece 3 and move it vertically upwards to perform the indentation test. The positional relationship between the light-transmitting indenter 2 and the test piece 3 during the indentation process is as follows: Figure 2 As shown, equal time intervals are set during the indentation process. m Each duration is t In the holding section, after each indentation is inserted into the holding section, the driving optical microscope acquires images of the contact area between the light-transmitting indenter 2 and the test piece 3. Due to the small depth of field of the optical microscope, in order to obtain clear images, the contact area needs to be scanned layer by layer. Since the position of the light-transmitting indenter 2 is fixed during the indentation test in this invention, in each holding section, a layer-by-layer scan can be performed starting from the lower tip of the light-transmitting indenter 2 and moving upwards to generate and acquire nano-speckle plane images N1 to N2 of the area in close contact with the indenter. m , among which, the i N speckle images i ,like Figure 3 As shown, the arrows indicate increasing indentation depth;

[0044] Step Six: Compare the original speckle image N0 obtained in Step Four with the image obtained in Step Five during the indentation test. m Zhang's spotted images N1 to N mImport digital speckle processing software Glare, according to the difference between adjacent short time preservation segments, obtain the deformation distribution diagram of the contact area between the tested piece 3 and the transparent indenter 2 in the micro-nano indentation test process compared with the initial state N0, the distribution diagram has m ;

[0045] Step seven, according to the area function of the adopted transparent indenter 2, the m deformation cloud diagram obtained in step six is post-processed, so that it is processed from a plane digital speckle picture to a three-dimensional deformation distribution diagram of the actual situation of the composite indentation through the area function of the adopted indenter, as shown in Figure 4 A is a plane digital speckle picture, and B is a three-dimensional speckle picture. The specific conversion process is that, taking the used indenter as an ideal indenter as an example, the area function is A h c h c 2 As shown in Figure 5 , the coordinates of the i th point in the j th plane digital speckle picture are 3, 4, then x j =3, y j =4, since each horizontal cross section of the Vickers indenter is a square, then Figure 5 OM length is 7, so the area of the horizontal cross section of the j th point is A h c h c ≈1.999837, so in the converted three-dimensional deformation distribution diagram, the coordinates of the point are 3, 4, 1.999837. j

[0046] The micro-nano indentation contact area deformation test method of the application can realize real-time observation of the contact area between the indenter and the sample during the indentation loading process, coat the sample surface with nano speckles, and perform indentation test on the surface by using a transparent indenter, in-situ observation of the nano speckles between the indenter and the sample by using an optical microscope, acquisition of three-dimensional deformation behavior information of the contact area in the micro-nano indentation test process, in-situ characterization of phenomena such as cracks, extrusion, and slip band generation in the existing micro-nano indentation test,

[0047] The application can also directly observe the contact area between the transparent indenter 2 and the tested piece 3 by using the objective lens 1 of the optical microscope, and without coating the tested piece 3 with speckles, the original surface deformation process of the tested piece 3 can be observed. ​​​​​

[0048] In the description of the application, it should be understood that the terms "upper", "lower", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the application.

[0049] Although the embodiments of the application have been shown and described above, it should be understood that the above-described embodiments are exemplary and cannot be understood as a limitation on the application, and those of ordinary skill in the art can make changes, modifications, replacements and variations to the above-described embodiments within the scope of the application.

Claims

1. A method of testing micro- and nano- indentation contact area deformation, characterized in that, The method comprises the following steps: Step one, coating the surface of the test piece with nano speckle; Step two, fixing the test piece coated with nano speckle on the stage of the driving indentation tester, and making the test piece located directly below the transparent indenter; Step three, adjusting the optical microscope so that the objective lens can observe the lower tip of the transparent indenter, which is the initial position of the transparent indenter at this time; Step four, moving away the transparent indenter, adjusting the position of the test piece in the vertical direction so that the objective lens can observe the surface of the test sample, adjusting the position of the test piece in the horizontal direction, setting the indentation area as the area in the field of view of the objective lens as the indentation area, shooting the original speckle image N0 in the indentation area, and moving the transparent indenter back to the initial position; Step five, set m short time holding segments with time t in the indentation test process, after starting the test, use optical microscope to scan the contact area between the tip under the transparent indenter and the test piece layer by layer in each short time holding segment, generate and obtain nanoscale speckle planar images N1 to Nm of the contact area m , wherein the i-th speckle picture is N i ; Step six, acquire the nanospeck planar image N1 to N of the contact area m The deformation distribution map compared with the original speckle image N0, the distribution map has m in common; Step seven, processing the deformation distribution map through the area function of the transparent indenter to obtain a three-dimensional deformation distribution map conforming to the actual situation of the indentation.

2. The method for testing deformation of the micro / nano indentation contact area as described in claim 1, characterized in that: The area function of the light-transparent indenter is measured using an atomic force microscope and fitted, the fitted result being expressed as A(h c ) = C0h c 2 +C1h c +C2h c 1 / 2 +C3h c 1 / 4 +···+C8h c 1 / 128 , which means that the cross-sectional area at the position h c from the tip of the light-transparent indenter when the indenter is vertically placed is A(h c ).

3. The method for testing deformation of the micro / nano indentation contact area as described in claim 1, characterized in that: The step four takes the tip under the transparent pressure head as the initial point, focuses the optical microscope light path at the point position, and gradually changes the focal length, layer by layer upward collection, until the transparent pressure head and the test piece are separated, and the images collected step by step are spliced to obtain the nanoscale speckle planar image N1 to N m .

4. A device for testing micro- and nano- indentation contact area deformation, characterized by: The device comprises a transparent indenter 2 that can move in a horizontal plane, an optical microscope, a test piece 3, a stage 4 that can move in a three-dimensional space, a nanometer speckle plane image acquisition module, a digital speckle processing module, and a three-dimensional deformation distribution acquisition module; the transparent indenter 2 is placed below the objective lens 1 of the optical microscope, the test piece 3 coated with nanometer speckles is fixed above the stage 4, and during the indentation process of the transparent indenter 2 and the test piece 3, the objective lens 1 of the optical microscope passes through the transparent indenter 2 from above to perform layer-by-layer scanning on the contact area between the tip below the transparent indenter and the test piece by using the optical microscope in each short time loading section; the nanometer speckle plane image acquisition module is used to generate and acquire nanometer speckle plane images N1 to N m of the contact area; the digital speckle processing module is used to process the acquired nanometer speckle plane images N1 to N m of the contact area compared with the original speckle image N0, and the deformation distribution has a total of m; and the three-dimensional deformation distribution acquisition module is used to post-process the deformation distribution through the area function of the transparent indenter.

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