A method for testing the distance between a nanoindentation testing indenter and a sample

Abstract

The application discloses a kind of nanoindentation test indenter and sample distance test method, belong to material mechanics property test technical field, utilize double microscope nanoindentation test experimental device to test, including main microscope, tilting microscope, nanoindentation indenter connecting rod, nanoindentation indenter and image processing system, tilting microscope and main microscope are connected with image processing system, by the cooperation of two microscopes of tilting and vertical sample platform, can be completed in the case where microscope position is not moved and is not refocused whole nanoindentation work plane selection, distance measurement and test process monitoring;The scheme is based on high, low temperature environment nanoindentation test demand, realizes the efficient, accurate acquisition of its distance with sample plane in the process of indenter pressing down, and then optimizes the application of contact / non-contact heat conduction method in high, low temperature nanoindentation test, improves overall test efficiency and experimental success rate.

Description

Technical Field

[0001] This invention belongs to the field of material mechanical property testing technology, specifically relating to a method for testing the distance between the indenter and the sample in nanoindentation testing. Background Technology

[0002] Nanoindentation testing is one of the most microscopic techniques currently available for simulating and observing the mechanical deformation behavior of materials through physical simulation experiments. It has been widely applied in materials science, electronic engineering, biomedical engineering, and geotechnical mechanics. Nanoindentation testing can be used to test the mechanical properties of materials within extremely small size ranges and obtain their elastic and plastic characteristic parameters. With the development and maturation of nanoindentation testing, its application boundaries are gradually expanding. Recently, there have been many studies applying nanoindentation testing to the surface performance testing of materials under extremely high and low temperature environments. For example, invention patent application CN116929913A discloses a dual-indenter, dual-microscope nanoindentation / scratch experimental mechanism and method for hydrates.

[0003] For nanoindentation testing in extremely high and low temperature environments, precise temperature control of the indenter is one of the main technical challenges limiting its application. High temperature stability is required during nanoindentation testing to minimize the impact of thermal drift. This drift includes mechanical thermal expansion / contraction and changes in electrical properties due to temperature variations. Contacting the indenter with the surface of the sample being tested (at low / high temperatures) and achieving temperature equilibrium through contact or non-contact heat conduction, thereby eliminating the influence of thermal drift on the temperature test, is a simple and efficient method for indenter and sample temperature control.

[0004] However, applying this method for indenter temperature control requires real-time acquisition of the distance between the indenter and the sample to prevent the indenter from being too far from the sample or completely pressed into the sample, affecting the efficiency of heat conduction between the indenter and the sample, or starting the experiment before complete temperature equilibrium is achieved. Current nanoindentation experimental devices can only calibrate the indenter position after the indenter is pressed in and the hardness curve data is obtained, and cannot determine the distance between the indenter and the sample in real time during the experiment. To address this technical deficiency, there is an urgent need to propose a method that can determine the distance between the indenter and the sample in real time during the experiment. Summary of the Invention

[0005] This invention addresses the difficulty in controlling the distance between the indenter and the sample during contact-type heat conduction in high-temperature / low-temperature nanoindentation testing. It proposes a method for measuring the distance between the indenter and the sample in nanoindentation testing, which analyzes the distance between the sample and the indenter based on post-processing of images monitored by a tilting microscope. This method is applicable to nanoindentation experiments that require pre-treatment for both contact and non-contact heat conduction.

[0006] The technical solution of this invention is as follows: A method for testing the distance between the indenter and the sample in nanoindentation testing, using a dual-microscope nanoindentation testing experimental device, including a main microscope, a tilting microscope, a nanoindentation indenter connecting rod, a nanoindentation indenter, and an image processing system. The nanoindentation indenter is mounted on the nanoindentation indenter connecting rod. The tilting microscope can observe the nanoindentation indenter and the sample surface. Its tilt angle with the horizontal plane is set as β; for ease of calculation, its value is determined according to the experimental observation requirements. The main microscope is vertically positioned directly above the sample stage to select the target working plane for nanoindentation and scratch experiments. Both the tilting microscope and the main microscope are connected to the image processing system to achieve real-time acquisition of microscope images and synchronous data processing to display the distance between the indenter and the sample. Furthermore, the nanoindentation indenter connecting rod, the tilting microscope, and the main microscope are all equipped with precision electrically controlled moving devices on the x, y, and z axes, which can move accurately in three-dimensional space to meet the needs of nanoindentation testing.

[0007] Specifically, the following steps are included:

[0008] Step S1: Mark the location of the nano-indentation indenter on the upper surface of the nano-indentation indenter connecting rod to facilitate moving the nano-indentation indenter to a suitable position after the working plane is selected.

[0009] Acquire and record the thickness (H) of the nanoindentation indenter connecting rod. p ), length of nano-indentation indenter (L) p ), distance from the nano-indentation indenter to the tip of the nano-indentation indenter connecting rod (d) p The above parameters are all structural parameters of the equipment, which can be obtained through prior measurement or by consulting the equipment design drawings.

[0010] Step S2: Adjust the nanoindentation indenter connecting rod to any height above the area to be tested, and measure the distance (z0) between the upper part of the nanoindentation indenter connecting rod and the sample plane at this time as the test equilibrium height; use the main microscope to select the working plane for the nanoindentation test, and fix the position of the main microscope after selection; keep the vertical height unchanged, extend the nanoindentation indenter connecting rod into the sample chamber to the working plane selected by the main microscope, and fine adjust the position of the nanoindentation indenter to make it located at the selected test position.

[0011] Then, move and adjust the position and focal length of the tilt microscope so that both the nanoindentation indenter rod and the sample are within the field of view of the tilt microscope. Fine-tune the position of the tilt microscope so that the upper part of the end face of the nanoindentation indenter rod (point a) is exactly at the upper edge of the observation area of ​​the tilt microscope. Use this position as the equilibrium position to fix the tilt microscope. Acquire the microscope monitoring image at this time and measure the vertical height H from the lower part of the end face of the nanoindentation indenter rod (point b) to the upper edge of the microscope observation area (point a).p ', combined with the thickness H of the nano-indentation indenter connecting rod p Calculate the scale α between the displayed image and the actual physical size.

[0012] Step S3: Control the nanoindentation indenter to move downwards and perform real-time analysis on the image observed in the tilting microscope. Extract the distance d from the upper end face of the nanoindentation indenter connecting rod to the upper edge of the entire observation area of ​​the microscope. a At this time, the distance d between the tip of the nanoindentation indenter and the sample surface is... z The following formula can be used to calculate:

[0013] d z =z0-H p -L p -αd a

[0014] The critical d for contact between the nanoindentation indenter and the sample surface can be calculated using the above formula. a0 Value (i.e., d) z d when the value is 0 a (value), when observed in a tilting microscope d a The value is close to the critical value d a0 For experiments requiring contact-type heat conduction, the z-axis knob of the nanoindentation indenter can be finely adjusted to bring the sample into contact with the indenter. For experiments requiring non-contact heat conduction, the indenter position can be kept unchanged, and data from the temperature sensor at the tip of the indenter can be obtained to evaluate the heat conduction efficiency at the indenter. Then, it can be considered whether the distance between the indenter and the sample needs to be adjusted.

[0015] Compared with the prior art, the advantages and positive effects of the present invention are as follows:

[0016] This scheme, employing two microscopes with tilted and vertical sample stages, allows for the selection of the working plane, distance measurement, and monitoring of the entire nanoindentation process without moving the microscopes or refocusing. It enables the acquisition of the indenter-sample distance based on images observed through the tilted microscope, significantly simplifying experimental operations and improving efficiency. The proposed indenter-sample distance measurement method is designed for high and low temperature nanoindentation testing, achieving efficient and accurate acquisition of the distance between the indenter and the sample plane during indentation. This optimizes the application of contact / non-contact heat conduction methods in high and low temperature nanoindentation testing, improving overall testing efficiency and experimental success rate. Attached Figure Description

[0017] Figure 1 This is a schematic diagram showing the positional relationship between the main microscope, the tilting microscope, and the nanoindentation indenter connecting rod in a nanoindentation testing experiment.

[0018] Figure 2This is a schematic front view of the nanoindentation testing experimental setup.

[0019] Figure 3 This is a side view of the nanoindentation testing experimental setup.

[0020] Figure 4 This is a schematic diagram of the observation range of the tilt microscope when the nanoindentation indenter connecting rod is in its initial state according to an embodiment of the present invention; wherein, the left is the initial state of the tilt microscope, and the right is the observation image of the tilt microscope;

[0021] Figure 5 This is a schematic diagram of the observation range of the tilt microscope during the pressing of the nano-indentation indenter connecting rod in an embodiment of the present invention; wherein, the left side shows the tilt microscope pressing state, and the right side shows the tilt microscope observation image;

[0022] Figure 6 This is a schematic diagram of the observation range of a tilting microscope when the nanoindentation indenter is in contact with the sample according to an embodiment of the present invention; the left side shows the contact state between the tilting microscope and the sample, and the right side shows the image observed by the tilting microscope;

[0023] The components include: 1. Main microscope; 2. Tilt microscope; 3. Nanoindentation indenter linkage; 4. Nanoindentation indenter; 5. Sample. Detailed Implementation

[0024] To better understand the above-described objects, features, and advantages of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and embodiments. Many specific details are set forth in the following description to provide a thorough understanding of the present invention; however, the present invention may be practiced in other ways than those described herein, and therefore, the present invention is not limited to the specific embodiments disclosed below.

[0025] To address the challenge of determining the indenter's indentation parameters in non-contact and contact heat transfer schemes during low-temperature and high-temperature nanoindentation testing, conventional nanoindentation testing, lacking an observation system, relies solely on the test curve feedback after indentation to calibrate the indenter's position; the position remains undetermined before indentation. This embodiment proposes a method for measuring the distance between the indenter and the sample in nanoindentation testing.

[0026] Specifically, this embodiment utilizes a dual-microscope nanoindentation testing experimental setup for testing, such as... Figure 2 and Figure 3As shown, the system includes a main microscope 1, a tilting microscope 2, a nanoindentation indenter connecting rod 3, a nanoindentation indenter 4, and an image processing system. The nanoindentation indenter 4 is mounted on the nanoindentation indenter connecting rod 3. The tilting microscope can observe the nanoindentation indenter and the sample surface. Its tilt angle with the horizontal plane is set to β. The main microscope 1 is vertically positioned directly above the sample stage to select the target working plane for nanoindentation and scratch experiments. Both the tilting microscope 2 and the main microscope 1 are connected to the image processing system to achieve real-time acquisition of microscope images and synchronous data processing to display the distance between the indenter and the sample.

[0027] like Figure 2 and Figure 3 As shown, for ease of calculation, the value of β is determined according to the experimental observation requirements, such as selecting tilt angles of 60 degrees, 45 degrees, etc. In this embodiment, 45 degrees is preferred. In addition, the nanoindentation indenter connecting rod 3, tilting microscope 2 and main microscope 1 are all equipped with position adjustment knobs in three directions of x, y and z axes, which can be precisely moved in three-dimensional space for selecting the nanoindentation working surface, realizing the nanoindentation process and determining the indenter position, so as to meet the needs of nanoindentation testing.

[0028] like Figure 1 As shown, the positional relationship between the main microscope 1, tilting microscope 2, nanoindentation indenter connecting rod 3, nanoindentation indenter 4, and the sample plane 5 is illustrated. An enlarged view of the area surrounding the nanoindentation indenter 4 is also shown. Figure 4 As shown, the specific testing process is as follows:

[0029] Step S1: Before the experiment begins, adjust the nanoindentation indenter rod 3 to a fixed height and record the distance z0 between its upper part and the sample plane at this time; after selecting the working plane to be tested using the main microscope 1, fix the position of the main microscope 1 unchanged; keep the vertical height of the nanoindentation indenter rod 3 unchanged, move it into the sample chamber to the selected working plane, and use the position adjustment knob to fine-tune the test position.

[0030] In the embodiments described in this invention, after the position of the nanoindentation indenter connecting rod 3 is fixed, the position and focal length of the tilting microscope 2 are adjusted so that both the nanoindentation indenter connecting rod 3 and the sample 5 appear within the observation range of the tilting microscope 2; the microscope position is finely adjusted so that, in the initial state, the upper edge of the end face of the nanoindentation indenter connecting rod 3 is exactly at the upper edge of the microscope's observation (point a), such as... Figure 4 As shown in the figure. Using this position as the equilibrium position, fix the tilted microscope. Acquire the microscope monitoring image at this time, and measure the vertical height (H) from the lower part of the nanoindentation indenter connecting rod end face to the upper edge of the microscope observation area in the microscope measurement image at this time. p '), based on the actual nanoindentation indenter thickness (H) pThis yields the scale between the image and the actual size, as shown in formula (1):

[0031]

[0032] In the embodiments described in this invention, reference is made to Figure 5 In the case where the adjustment knob controls the downward movement of the nanoindentation indenter 4, the image observed in the tilting microscope 2 is analyzed in real time, and the distance d from the upper end face of the nanoindentation indenter connecting rod 3 to the upper edge of the entire observation area of ​​the microscope is extracted simultaneously. a At this time, the distance d between the tip of the nano-indentation indenter 4 and the sample surface is... z It can be calculated using the following formula (2):

[0033] d z =z0-H p -L p -αd a (2)

[0034] In the embodiments described in this invention, the feature distance d a It can be obtained from the following formula (3):

[0035]

[0036] A schematic diagram of the nanoindentation indenter 4 pressing down onto the sample surface is shown in the image. Figure 6 At this time d z The value is 0, and the critical feature distance d a0 The value can be calculated using the following formula (3):

[0037]

[0038] When d was tested in tilting microscope 2 a The value is close to the critical value d a0 If the experiment requires contact-type heat conduction temperature control, the z-axis displacement knob of the pressure head linkage can be finely adjusted to make the sample contact the pressure head; if the experiment requires non-contact heat conduction, the pressure head position can be kept unchanged, the temperature change data obtained by the temperature sensor at the tip of the pressure head can be analyzed, the heat conduction efficiency between the pressure head and the sample can be evaluated, and then it can be considered whether the distance between the pressure head and the sample needs to be further adjusted.

[0039] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments for application in other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for measuring the distance between the indenter and the sample in nanoindentation testing, using a dual-microscope nanoindentation testing experimental apparatus, comprising a main microscope, a tilting microscope, a nanoindentation indenter connecting rod, and a nanoindentation indenter, wherein the nanoindentation indenter is mounted on the nanoindentation indenter connecting rod, the tilting microscope is used to observe the nanoindentation indenter and the sample surface, and its tilt angle with the horizontal plane is β, and the main microscope is vertically positioned directly above the sample stage to select the target working plane for nanoindentation and scratch experiments; characterized in that... The dual-microscope nanoindentation testing experimental device also includes an image processing system. Both the tilting microscope and the main microscope are connected to the image processing system to achieve real-time acquisition of microscope images and synchronous data processing to display the distance between the indenter and the sample. The testing method specifically includes the following steps: Step S1, Test Preparation: Mark the location of the nano-indenter on the upper surface of the nano-indenter connecting rod, and obtain and record the thickness H of the nano-indenter connecting rod. p Length L of the nano-indentation indenter p d is the distance d between the nano-indentation indenter and the tip of the nano-indentation indenter connecting rod. p ; Step S2: Adjust the nanoindentation indenter connecting rod to any height above the area to be tested, and measure the distance z0 between the upper part of the nanoindentation indenter connecting rod and the sample plane at this time. Use this distance as the test equilibrium height. Combine the image displayed by the tilting microscope with the actual size to determine the scale α between the displayed image and the real physical size. Step S3: Control the nanoindentation indenter to move downwards, perform real-time analysis on the image observed in the tilting microscope, and extract the distance d from the upper end face of the nanoindentation indenter connecting rod to the upper edge of the entire observation area of ​​the microscope. a At this time, the distance d between the tip of the nanoindentation indenter and the sample surface is... z It is expressed as follows: Then we have: Define d z d when the value is 0 a The value is the critical value d for the nanoindentation indenter to contact the sample surface. a0 Based on observations of d in a tilting microscope a Is the value close to the critical value d? a0 Then, the choice between contact-type or non-contact heat conduction is determined based on the distance between the indenter and the sample. In step S2, after fixing the position of the nanoindentation indenter connecting rod, the position and focal length of the tilting microscope are adjusted so that both the nanoindentation indenter connecting rod and the sample appear within the observation range of the tilting microscope. The position of the tilting microscope is finely adjusted so that, in the initial state, the upper edge of the end face of the nanoindentation indenter connecting rod is exactly at the upper edge a of the observation area of ​​the tilting microscope. Using this position as the equilibrium position, the tilting microscope is fixed, and the monitoring image of the tilting microscope is acquired. The vertical height H of the lower part b of the end face of the nanoindentation indenter connecting rod in the measurement image of the tilting microscope is measured from the upper edge a of the observation area of ​​the tilting microscope. p ', and then based on the actual nano-indentation indenter connecting rod thickness H p This yields the scale between the image and the actual size: Where α is the scale between the displayed image and the actual physical size, and β is the angle between the tilting microscope and the horizontal plane.

2. The method for measuring the distance between the indenter and the sample in nanoindentation testing according to claim 1, characterized in that: In step S3, when d is tested in the tilting microscope a The value is close to the critical value d a0 If the experiment requires contact-type heat conduction temperature control, the nanoindentation head linkage is finely adjusted to make the sample contact the indenter; if the experiment requires non-contact heat conduction, the position of the nanoindentation head is kept unchanged, the temperature change data obtained by the temperature sensor at the tip of the nanoindentation head is analyzed, the heat conduction efficiency between the nanoindentation head and the sample is evaluated, and then it is considered whether the distance between the nanoindentation head and the sample needs to be further adjusted.

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