Indenter, test method, and test apparatus

Abstract

To clearly obtain a contact surface between an indenter and a test body.SOLUTION: An indenter formed of a transparent material for applying a load to a test body comprises a first part and a second part. The first part has a triangular pyramid shape, and a tip thereof is a portion that contacts the test body. The second part is located on a side opposite to the tip when viewed from a bottom surface of the first part. A cross-section in a direction perpendicular to a perpendicular line extending from the tip of the first part toward the bottom surface of the first part is circular. The bottom surface of the first part and a bottom surface of the second part are parallel. The perpendicular line passes through a center of the bottom surface of the second part. An area of the cross-section of the second part increases continuously from the side of the first part. A side surface of the second part forms an inclination angle of 45.0° or more and 80.0° or less with respect to a plane parallel to the bottom surface of the second part.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a technique for observing the surface of a test piece using an indenter. [Background technology]

[0002] Indentation testing has been proposed to measure the mechanical properties (e.g., hardness and elastic modulus) of various specimens, such as metals, ceramics, and polymeric materials. Indentation testing evaluates the mechanical properties (e.g., hardness and elastic modulus) of a specimen by pressing an indenter into the surface of the specimen.

[0003] One type of indentation test is a microindentation test, which optically observes the contact surface between an indenter and a test piece into which the indenter is pressed (see, for example, Patent Documents 1 to 4). Microindentation tests use an indenter made of a transparent material such as diamond or sapphire that transmits light of a specific wavelength. Commonly used indenter shapes include triangular pyramids (Berkovich type) and square pyramids (Vickers type). Here, to evaluate mechanical properties with high precision, it is necessary to clearly observe the contact surface between the indenter and the test piece. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-195357 [Patent Document 2] Utility Model Registration No. 3182252 [Patent Document 3] Japanese Patent Application Laid-Open No. 2015-175666 [Patent Document 4] Japanese Patent Application Laid-Open No. 2017-146294 Summary of the Invention [Problem to be solved by the invention]

[0005] However, with the techniques of Patent Documents 1 to 4, there is a possibility that the contact surface between the indenter and the test piece cannot be clearly observed. If one were to attempt to clearly observe the contact surface, it would be necessary to illuminate the indenter with a complex oblique lighting mechanism. In consideration of the above circumstances, an object of the present invention is to clearly observe the contact surface between the indenter and the test piece. [Means for solving the problem]

[0006] [1] An indenter made of a transparent material for applying a load to a test specimen, comprising a first portion and a second portion, wherein the first portion has a triangular pyramid shape and its tip is in contact with the test specimen, the second portion is located on the opposite side of the first portion from the tip when viewed from the bottom surface of the first portion, the cross section of the first portion in a direction perpendicular to a perpendicular line drawn from the tip to the bottom surface of the first portion is circular, the bottom surface of the first portion and the bottom surface of the second portion are parallel, the perpendicular line passes through the center of the bottom surface of the second portion, the area of the cross section of the second portion increases continuously from the first portion side, and the angle at which the side of the second portion is inclined with respect to a plane parallel to the bottom surface of the second portion is 45.0° or more and 80.0° or less.

[0007] [2] The indenter according to [1], wherein the transparent material is diamond and the angle is 50.0° or more and 60.0° or less.

[0008] [3] The indenter according to [1], wherein the transparent material is sapphire and the angle is 50.0° or more and 80.0° or less.

[0009] [4] A testing method in which the indenter of claim 1 is pressed into a test piece and light is irradiated onto the indenter, and an image of the contact surface where the indenter and the test piece come into contact is obtained via an objective lens.

[0010] [5] The test method according to [4], wherein light is irradiated onto the indenter from a direction parallel to the optical axis of the objective lens.

[0011] [6] A test method according to [4] or [5], wherein the indenter is fixed using a substrate, a refractive index adjustment plate is provided between the indenter and the substrate, and the refractive index of the refractive index adjustment plate is a value between the refractive index of the indenter and the refractive index of the substrate.

[0012] A testing device comprising an indenter according to any one of [1] to [3], a loading device that moves at least one of the test piece and the indenter toward the other in order to press the indenter into the test piece, an illumination device that irradiates the indenter with light, and a microscope including an objective lens for obtaining an image of the contact surface where the indenter and the test piece come into contact.

[0013] [8] The testing device of [7] further comprising a substrate for fixing the indenter and a refractive index adjustment plate provided between the indenter and the substrate, wherein the refractive index of the refractive index adjustment plate is a value between the refractive index of the indenter and the refractive index of the substrate. [Effects of the Invention]

[0014] According to the indenter, test method, and test device of the present invention, the contact surface between the indenter and the test piece can be clearly observed. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a configuration diagram of a test device used in a microindentation test according to an example of an embodiment. [Figure 2] FIG. 2 is a side view of an indenter according to an example embodiment. [Figure 3] FIG. 2 is a top view of an indenter according to an example embodiment. [Figure 4] FIG. 2 is an explanatory diagram for explaining a first portion. [Figure 5] FIG. 10 is a side view of an indenter according to another example of the embodiment. [Figure 6] FIG. 10 is a side view of an indenter according to another example of the embodiment. [Figure 7] FIG. 2 is a schematic diagram of an indenter according to an example. [Figure 8] 1A and 1B are a table and a diagram illustrating the shape of an indenter according to an example. [Figure 9] 1 is an optical microscope photograph (bright-field image) of an indenter according to an example taken from the side. [Figure 10] 1 is an optical microscope photograph (bright field image) of an indenter according to an example taken from the tip side. [Figure 11] 1A and 1B are diagrams and actual photographs illustrating the setup required to mount an indenter according to an embodiment on a microindenter. [Figure 12] 1 is an image of the contact surface of a test specimen (PP) photographed using an indenter according to an example. [Figure 13] 1 is an image of the contact surface of a test specimen (PMMA) photographed using an indenter according to an example. [Figure 14] 1 is an image of the contact surface of a test specimen (PP, PMMA) photographed using an indenter according to an example. [Figure 15] 1 is an image of the contact surface of a test specimen (PMMA) photographed using an indenter according to a comparative example. [Figure 16] 1 shows an optical microscope photograph (bright-field image) of an indenter according to an example taken from the side and an optical microscope photograph (bright-field image) of an indenter according to an example taken from the tip side. [Figure 17] 1 shows an optical microscope photograph (bright-field image) of an indenter according to a comparative example taken from the side and an optical microscope photograph (bright-field image) of an indenter taken from the tip side. [Figure 18] 1 shows images of the contact surface of a test specimen (PP) photographed using indenters according to an example and a comparative example. [Figure 19] 1 is an optical microscope photograph (bright-field image) of an indenter according to an example taken from the side. [Figure 20] 1 is an image of the contact surface of a test specimen (PP, PMMA) photographed using an indenter according to an example. [Figure 21] 1 shows an optical microscope photograph (bright-field image) of an indenter according to an example taken from the side, and an image of the contact surface of a test piece (PP) taken using the indenter. DETAILED DESCRIPTION OF THE INVENTION

[0016] The indenter according to this embodiment is an indenter used in an indentation test for evaluating the mechanical properties of a test specimen (for example, stress-strain curve, Mayer hardness, Young's modulus, yield value, etc.) Specifically, the indenter according to this embodiment is used in a microindentation test in which the indenter is pressed into the surface of a test specimen and the contact surface between the indenter and the test specimen is optically observed.

[0017] FIG. 1 is a configuration diagram of a test apparatus 90 used in a microindentation test. First, an overview of the test apparatus 90 will be described. As illustrated in FIG. 1, the test apparatus 90 is equipped with an indenter 100, a microscope 300, an illumination device 200, a loading device 400, and a measuring device 500. The indenter 100 is supported by a housing B. The housing B houses the loading device 400 and the measuring device 500. The test specimen S is placed in the housing B at a position facing the indenter 100.

[0018] The loading device 400 is a device for applying a load to the test piece S by moving the test piece S toward the indenter 100. When the test piece S is moved toward the indenter 100 by the loading device 400, a load is applied to the test piece S by the indenter 100. The loading device 400 is configured by, for example, a three-axis stage, a piezoelectric element, or a piezoelectric driving device. The measuring device 500 is a device for measuring the load value applied to the test piece S by the loading device 400.

[0019] The microscope 300 is a device for observing the contact surface between the indenter 100 and the test piece S. Specifically, the microscope 300 includes an objective lens 301 for obtaining an image of the contact surface and an imaging device (camera) 303 for capturing the image of the contact surface. The microscope 300 may also include an eyepiece (not shown) for viewing the image of the contact surface with the naked eye. For example, the mechanical properties of the test piece S are determined from the area of the contact surface determined by analyzing the image captured by the imaging device 303 and the load value measured by the measuring device 500. For example, the hardness of the test piece S can be determined by the ultra-microload hardness testing method (JIS Z2255:2003).

[0020] The illumination device 200 includes an optical element (for example, an LED: Light Emission Diode) that irradiates light of, for example, 400 to 750 nm. In this embodiment, an illumination device 200 that irradiates the indenter 100 with light from a direction parallel to the optical axis of the objective lens 301 (i.e., coaxial illumination) is preferably used. When the illumination device 200 irradiates the indenter 100 with light, an optical image of the contact surface is obtained.

[0021] The shape of the indenter 100 used in this embodiment will be described in detail below.

[0022] Specifically, the indenter 100 is made of a transparent material. In the present invention, a transparent material is a material that transmits 50% or more of light with a wavelength of 400 to 1500 nm. Specifically, transparent materials are materials commonly used for indenters in microindentation tests, such as diamond, sapphire, quartz glass, and optical glass (BK7). For light with a wavelength of 589.3 nm, the refractive index of diamond is 2.42, the refractive index of sapphire is 1.77, the refractive index of quartz glass is 1.46, and the refractive index of optical glass (BK7) is 1.52.

[0023] 2 and 3 are a side view and a top view of an indenter 100 according to an example of this embodiment. By using the indenter 100 of this embodiment, the contact surface between the indenter 100 and the test piece S can be clearly observed. In the following description, the direction in which the indenter 100 is pressed into the test piece S is referred to as the X direction, and the direction perpendicular to the X direction is referred to as the Y direction. In other words, the X direction is the direction in which the test piece S moves in FIG. 1. FIG. 2 is a view of the indenter 100 as viewed from the negative side of the Y direction, and FIG. 3 is a view of the indenter 100 as viewed from the positive side of the X direction. The indenter 100 and the objective lens 301 are arranged so that their optical axes coincide and the focal point of the microscope 300 coincides with the apex of the indenter 100.

[0024] The indenter 100 of this embodiment includes a first portion 10, a third portion 30, a second portion 20, and a fourth portion 40. From the positive side to the negative side in the X direction, the first portion 10, the third portion 30, the second portion 20, and the fourth portion 40 are located in this order. Note that the first portion 10, the third portion 30, the second portion 20, and the fourth portion 40 are formed continuously and integrally, and there is no boundary surface at the connection portion of each portion.

[0025] The first portion 10 has a triangular pyramid shape, which is a so-called Berkovich type. That is, the first portion 10 has a shape including a base 11, three side surfaces 13, and a vertex 15. The base 11 of the first portion 10 is an equilateral triangle, and each side surface 13 is an isosceles triangle. The vertex 15 is the tip of the first portion 10 (indenter), and is the part that comes into contact with the test piece S.

[0026] FIG. 4 is an explanatory diagram illustrating the first portion 10. The first portion 10 has a tip face angle α of 65.0 (±0.3)°, a tip ridge angle ψ of 76.9 (±0.3)°, an inclination angle β of 25.0 (±0.3)°, and an inter-ridge angle 2θ of 115.0 (±0.3)° (in accordance with ISO 14577-2 4.2.3.4). The first portion 10 is pressed into the test piece S from its vertex 15. The length L of each side of the bottom surface 11 (the base of the side surface 13) is determined appropriately depending on the type of test piece S (e.g., Mayer hardness), but is assumed to be, for example, 0.08 to 6.00 mm from the viewpoint of obtaining a clear contact surface. For example, the length L of each side of the bottom surface 11 needs to be about 0.08 mm when the test object is made of a hard material (e.g., silicon carbide, Mayer hardness: 16.3 GPa), and about 6.00 mm when the test object is made of a soft material (e.g., gel, Mayer hardness: 125 Pa). The height h0 of the first portion 10 is expected to be, for example, 0.02 to 1.73 mm. Note that in FIGS. 2 and 3, a perpendicular line P extending from the vertex 15 (tip) of the first portion 10 toward the bottom surface 11 of the first portion 10 is also shown. In other words, the perpendicular line P is the central axis of the indenter 100.

[0027] As illustrated in FIGS. 2 and 3, the second portion 20 has a circular cross section in a direction perpendicular to the perpendicular line P. Note that, since the cross section of the second portion 20 may not be perfectly circular in some manufacturing processes, the cross section may be approximately circular (for example, with a circularity of 0.84 or more, preferably 0.88 or more, and more preferably 0.90 or more). The circularity of the cross section of the second portion 20 can be determined using image analysis software (ImageJ) manufactured by the National Institutes of Health (NIH). Note that the circularity of the cross section of the second portion 20 is ideally 1, but may also be less than 1 due to manufacturing issues.

[0028] The second portion 20 is located on the opposite side of the apex 15 (tip) from the bottom surface 11 of the first portion 10. The area of the cross section of the second portion 20 increases continuously from the first portion 10 side along the perpendicular line P. In other words, the diameter of the cross section of the second portion 20 increases continuously from the first portion 10 side along the perpendicular line P. In this embodiment, the second portion 20 is exemplified as a truncated cone. As illustrated in FIG. 2, the side surface 25 of the second portion 20 has a shape that describes a straight line in side view.

[0029] The second portion 20 has a bottom surface 21, a top surface 23, and a side surface 25. The top surface 23 of the second portion 20 is positioned opposite the bottom surface 11 of the first portion 10. In other words, the first portion 10 and the bottom surface 21 of the second portion 20 are positioned on opposite sides of the top surface 23 of the second portion 20. The bottom surface 21 and the top surface 23 are circular and parallel to each other. The diameter of the top surface 23 is smaller than the diameter of the bottom surface 21. The cross-sectional area of the second portion 20 in a plane perpendicular to the X direction continuously increases from the top surface 23 side toward the bottom surface 21 side. As illustrated in FIG. 2 , the first portion 10 is positioned inside the top surface 23 of the second portion 20 when viewed from the positive side of the X direction.

[0030] The first part 10 and the second part 20 are arranged so that the bottom surface 11 of the first part 10 and the bottom surface 21 of the second part 20 are parallel to each other and a perpendicular line drawn from the vertex 15 of the first part 10 to the bottom surface 11 of the first part 10 passes through the center of the bottom surface 21 of the second part 20.

[0031] The inclination angle β2 of the side surface 25 of the second portion 20 with respect to a plane parallel to the bottom surface 21 of the second portion 20 is 45.0° or more and 80.0° or less. The inclination angle β2 may be specified as the angle between the side surface 25 and a plane parallel to the bottom surface 21 of the second portion 20, as designed when manufacturing the indenter 100. The inclination angle β2 is also the angle between the side surface 25 and a plane parallel to the bottom surface 21 of the second portion 20 when viewing the indenter 100 from a direction perpendicular to the perpendicular line P (the Y direction). The inclination angle β2 may also be determined by measuring an optical micrograph of the indenter captured with an optical microscope. FIG. 4 illustrates a configuration in which the shape of the second portion 20 is a truncated cone, and therefore the inclination angle β2 is constant over the entire length of the second portion 20 (the entire X direction). The inclination angle β2 within the above range allows the contact surface to be clearly observed. From the viewpoint of enabling clearer observation of the contact surface, the lower limit of the tilt angle β2 is preferably 50.0°, more preferably 53.0°, and even more preferably 55.0°, and the upper limit of the tilt angle β2 is preferably 75.0°, more preferably 68.0°, and even more preferably 65.0°. The range of the tilt angle β2 can be appropriately changed depending on the refractive index of the indenter 100. For example, when the indenter 100 is formed of a transparent material having a refractive index of 2.0 or more (e.g., diamond), the tilt angle β2 is preferably 50.0° or more and 60.0° or less, more preferably 53.0° or more and 58.0° or less. For example, when the indenter 100 is formed of a transparent material having a refractive index of less than 2.0 (e.g., sapphire), the tilt angle β2 is preferably 50.0° or more and 80.0° or less, more preferably 55.0° or more and 78.0° or less, and even more preferably 60.0° or more and 68.0° or less.

[0032] 2, the side surface 25 of the second portion 20 is inclined with respect to the perpendicular line P, and the inclination angle β2 can be said to be the angle at which the side surface 25 of the second portion 20 is inclined with respect to the perpendicular line P. In other words, the inclination angle β2 can be said to be the angle between the bottom surface 11 of the first portion 10 and the side surface 25 of the second portion 20.

[0033] The diameters of the bottom surface 21 and top surface 23 of the second portion 20 are not particularly limited as long as the inclination angle β2 is within the above range, but from the viewpoint of clearly observing the contact surface between the indenter 100 and the test piece S, it is preferably 0.16 to 18.00 mm. The diameter of the top surface 23 of the second portion 20 is not particularly limited, but from the viewpoint of clearly observing the contact surface between the indenter and the test piece S, it is preferably 0.10 to 9.80 mm.

[0034] Similarly, the height (distance in the X direction) of the second portion 20 is not particularly limited as long as the tilt angle β2 is within the above range, but from the viewpoint of clearly observing the contact surface between the indenter 100 and the test piece S, it is preferably 0.03 to 11.30 mm. Furthermore, the length (distance in the X direction) from the apex 15 of the first portion 10 to the bottom surface 21 of the second portion 20 is not particularly limited, but from the viewpoint of clearly observing the contact surface between the indenter 100 and the test piece S, it is preferably about 0.06 to 18.20 mm.

[0035] The second portion 20 is considered to function as an illumination device (ring light). The tilt angle β2 of the second portion 20 is the illumination angle as an illumination device, and the dimensions of the second portion 20 (the diameter and height of the bottom surface 21 and the top surface 23) affect the illuminance as an illumination device. Therefore, by including the second portion 20 in the indenter 100, the contact surface can be clearly observed.

[0036] FIG. 5 is a side view (side view corresponding to FIG. 2) of an indenter 100 according to another example of this embodiment. In FIG. 5, the shape of the second portion 20 is different from the shape of the second portion 20 in FIG. 4. While FIG. 4 illustrates a configuration in which the inclination angle β2 is constant over the entire length of the second portion 20, FIG. 5 illustrates a configuration in which the inclination angle β2 is not constant along the length of the second portion 20. That is, the side surface 25 of the second portion 20 is divided into multiple sections with different inclination angles β2. FIG. 5 illustrates a configuration in which the second portion 20 is divided into two sections 20A and 20B with different inclination angles β2. Section 20A and section 20B are located in this order from the positive side in the X direction (the first portion 10 side).

[0037] The inclination angle β2 of sections 20A and 20B can be any value within the above-mentioned range, but the inclination angle β2 of section 20B is larger than the inclination angle β2 of section 20B. Both sections 20A and 20B have a truncated cone shape. In other words, the bottom surface of section 20A is the top surface of section 20B.

[0038] The second portion 20 may include three or more sections with different inclination angles β2. When the second portion 20 includes two or more sections with different inclination angles β2, it is preferable that the inclination angle β2 of each section increases from the first portion 10 side. However, the present invention also includes a configuration in which the inclination angle β2 of each section of the second portion 20 decreases from the first portion 10 side.

[0039] FIG. 6 is a side view (side view corresponding to FIG. 2) of an indenter 100 according to yet another example of this embodiment. As illustrated in FIG. 6, the side surface 25 of the second portion 20 may have a curved shape in side view. Note that, similar to FIGS. 2 and 4, the cross-sectional area of the second portion 20 continuously increases from the first portion 10 side. In other words, the second portion 20 in FIG. 6 has a bell shape. In the example of FIG. 6, the inclination angle β2 (the angle between the side surface 25 and a plane parallel to the bottom surface 21 of the second portion 20) is the angle between the bottom surface 21 and a straight line connecting the outer edge of the bottom surface 21 of the second portion 20 to the outer edge of the top surface 23, in side view.

[0040] As can be understood from the above explanation, the shape of the second portion 20 is arbitrary as long as the diameter of the cross section of the second portion 20 increases continuously from the first portion 10 side and the inclination angle β2 is 45.0° or more and 80.0° or less.

[0041] The third portion 30 is a portion that connects the first portion 10 and the second portion 20 (a portion whose cross section is neither triangular nor circular). The third portion 30 does not exist to enable clear observation of the contact surface between the indenter 100 and the specimen S, but exists due to manufacturing issues when attaching the first portion 10 to the indenter 100. A typical Berkovich-type indenter 100 may also have a shape similar to the third portion 30. The shape of the third portion 30 is not particularly limited, as long as it does not hinder the acquisition of the contact surface and allows the first portion 10 and the second portion 20 to be formed continuously. The perpendicular line P can also be described as a line that passes through the center of the first portion 10, the center of the second portion 20, and the center of the third portion when viewed from the X direction.

[0042] The fourth portion 40 is cylindrical and is formed continuously from the bottom surface of the second portion 20. In other words, the diameter of the fourth portion 40 is the same as the diameter of the bottom surface of the second portion 20. The fourth portion 40 is a portion provided for installing the indenter 100 in the housing B. The bottom surface 41 of the fourth portion 40 is the surface of the fourth portion 40 opposite to the second portion 20, and can also be said to be the back surface of the indenter 100. The height (length in the X direction) of the fourth portion 40 is not particularly limited and is expected to be, for example, 0.00 to 10.00 mm. In other words, the fourth portion 40 may be omitted.

[0043] The three side surfaces 13 of the first portion 10 and the back surface of the indenter 100 (the bottom surface 41 of the fourth portion 40 in this embodiment) are optically polished surfaces because they need to transmit light. On the other hand, the side surface 25 of the second portion 20 is preferably a ground surface with fine irregularities on the surface. By making the side surface 25 of the second portion 20 a ground surface, the light emitted from the lighting device 200 can be scattered, resulting in a clearer contact surface. However, the side surface 25 of the second portion 20 may also be an optically polished surface. The side surface of the third portion 30 may be either an optically polished surface or a ground surface.

[0044] Because the first portion 10 to the fourth portion 40 are formed continuously and integrally from a transparent material, the boundary between the first portion 10 and the third portion 30 (the bottom surface 11 of the first portion 10) and the boundary between the second portion 20 and the third portion 30 (the top surface 23 of the second portion 20) cannot actually be visually confirmed. Therefore, in Figures 2 and 3, they are indicated by dashed lines. In other words, when the indenter 100 is divided into sections along a plane perpendicular to the X direction, the first portion 10 is the portion from which a triangular pyramid can be conceived, the second portion 20 is the portion with a circular cross section whose diameter continuously increases from the first portion 10 side, the third portion 30 is the portion located between the first portion 10 and the second portion 20 (the portion whose cross section is neither triangular nor circular), and the fourth portion 40 is the portion of the second portion 20 on the opposite side from the first portion 10 from which a cylinder can be conceived.

[0045] It should be noted that the third portion 30 and the fourth portion 40 are not essential to the present invention. For example, the present invention also encompasses an indenter 100 in which the first portion 10 and the second portion 20 are directly connected. Furthermore, the indenter 100 may include other portions in addition to the first portion 10, the second portion 20, the third portion 30, and the fourth portion 40. For example, other portions may be included between the second portion 20 and the fourth portion 40 (e.g., a portion where the side surface is inclined at an angle greater than 80.0°), between the second portion 20 and the third portion 30 (e.g., a portion where the side surface is inclined at an angle less than 45.0°), or between the first portion 10 and the third portion 30.

[0046] The indenter 100 described above is mounted on the testing apparatus 90 of FIG. 1. The lighting device 200 illuminates the indenter 100 (contact surface), allowing an optical image of the contact surface to be observed. While FIG. 1 illustrates a loading device 400 that moves the test piece S toward the indenter 100, a loading device 400 that moves the indenter 100 toward the test piece S may also be used. In a configuration in which the indenter 100 moves, the microscope 300 also moves in conjunction with the indenter 100. The loading device 400 may also be configured with a loading device that moves the test piece S toward the indenter 100 and a loading device that moves the indenter 100 toward the test piece S. As can be understood from the above description, the loading device 400 may have any configuration as long as it is possible to apply a load to the test piece S using the indenter 100 by moving at least one of the test piece S and the indenter 100 toward the other.

[0047] The indenter 100 is mounted on the housing B via a substrate. The indenter 100 is bonded to the substrate, for example, with an adhesive. The substrate, like the indenter, is made of a transparent material that transmits at least 50% of light with wavelengths of 400 to 1500 nm. The refractive index of the substrate is lower than that of the indenter. The thickness of the substrate is not particularly limited, but is, for example, 0.50 to 5.00 mm. The surface of the substrate may be coated with a film of an appropriate thickness to improve transmittance and provide anti-reflection properties.

[0048] (Refractive index adjustment plate) A refractive index adjusting plate may be inserted between the indenter and the substrate. It is preferable to use a refractive index adjusting plate, especially when the difference between the refractive index of the indenter and that of the substrate is large. The refractive index of the refractive index adjusting plate is a value between the refractive index of the indenter and that of the substrate. In other words, the refractive index of the refractive index adjusting plate is greater than that of the substrate and less than that of the indenter. By providing a refractive index adjusting plate between the indenter and the substrate, the contact surface between the indenter and the test piece can be observed more clearly. The refractive index adjusting plate, like the indenter, is made of a transparent material that transmits at least 50% of light with wavelengths of 400 to 1500 nm.

[0049] For example, when diamond (refractive index: 2.42) is used as an indenter and quartz glass (refractive index: 1.46) is used as a substrate, the refractive index adjustment plate can be made of BK7 (refractive index: 1.52), K5 (refractive index: 1.52), B270 / S1 (refractive index: 1.52), ZERODUR (refractive index: 1.54), SK11 (refractive index: 1.56), BAK4 (refractive index: 1.57), BaK1 (refractive index: 1.57), BAL35 (refractive index: 1.58), SK14 (Refractive Index: 1.60), SSK8 (Refractive Index: 1.62), F2 (Refractive Index: 1.62), BaSF1 (Refractive Index: 1.63), SF2 (Refractive Index: 1.65), LAK22 (Refractive Index: 1.65), BaH11 (Refractive Index: 1.67), BAF10 (Refractive Index: 1.67), SF5 (Refractive Index: 1.67), SF8 (Refractive Index: 1.69), LAK14 (Refractive Index: 1.70), SF15 (Refractive Index: 1.69), Refractive index: 1.70), BASF64 (Refractive index: 1.70), LAK8 (Refractive index: 1.71), SF18 (Refractive index: 1.72), SF10 (Refractive index: 1.73), TIH13 (Refractive index: 1.74), SF14 (Refractive index: 1.76), SF11 (Refractive index: 1.79), SF56 (Refractive index: 1.79), M100 (Refractive index: 1.8), LASF44 (Refractive index: 1.80), SF6 (Refractive index: 1.81), S Glasses such as F57 (refractive index: 1.85), LASF9 (refractive index: 1.85), SF66 (refractive index: 1.92), M130 (refractive index: 2.0), and LAH79 (refractive index: 2.00) can be used, as well as transparent ceramics such as sapphire (refractive index: 1.77), YAG (refractive index: 1.84), Y2O3 (refractive index: 1.92), polycrystalline alumina (refractive index: 2.1), and ZnSe (refractive index: 2.40). It is also possible to combine multiple different types of glass plates to create a refractive index adjustment plate.

[0050] Conventionally, in order to clearly observe the contact surface in a microindentation test, a complex oblique lighting device that illuminates from a direction tilted from the optical axis of the objective lens 301 was required. In contrast, in the test device 90 of this embodiment, by using the indenter 100 exemplified above, the contact surface can be clearly observed even with an illumination device that illuminates the indenter 100 by coaxial epi-illumination. However, a configuration in which an oblique lighting device is used as the illumination device 200 is also encompassed by the present invention.

[0051] The present invention can also be conceived as a testing method in which an indenter 100 is pressed into a test piece S, and an image of the contact surface between the indenter 100 and the test piece S is obtained via an objective lens 301 while irradiating the indenter 100 with light. The type of test piece S that is the subject of the present invention is not particularly limited, and may be inorganic materials such as metals and ceramics, polymeric materials such as resins, and food. [Example]

[0052] The present invention will be described in detail below based on examples, but the present invention is not limited to the examples.

[0053] The indenters according to Examples 1 to 4 were manufactured as follows.

[0054] Fig. 7 is a schematic diagram of an indenter (viewed from the same direction as Fig. 2). As illustrated in Fig. 7, the indenter includes a first portion (triangular pyramid), a second portion, a third portion, and a fourth portion (cylinder). The second portion in Examples 1 to 4 is a truncated cone.

[0055] As mentioned above, the first portion is a Berkovich type. Note that the third portion is not shown in Figure 7 for convenience, but it actually exists. β2 in Figure 7 is the inclination angle of the second portion (the angle at which the side of the second portion is inclined with respect to a plane parallel to the bottom surface of the second portion). h1 in Figure 7 is the height from the first portion to the second portion (the distance from the apex of the first portion to the bottom surface of the second portion), h2 is the height of the fourth portion, and H is the total height of the indenter (h1 + h2). Note that the side of the first portion and the bottom surface of the fourth portion of the indenter surface are optically polished, and the other portions are ground.

[0056] FIG. 8 shows a table illustrating the shapes of the indenters and a schematic diagram of the indenters for Examples 1 to 4. The indenters were manufactured using diamond (n = 2.42). The table in FIG. 8 shows the design dimensions (Φ, H, h1, h2) and angles (β, β2). FIG. 9 shows optical microscope photographs (bright-field images) of the indenters of Examples 1 to 4 taken from the side (direction perpendicular to the perpendicular line P). FIG. 10 shows optical microscope photographs (bright-field images) of the indenter of Example 2 taken from the tip side (direction parallel to the perpendicular line P).

[0057] The tilt angle β2 of the second portion (frustum of the cone) was measured by analyzing an optical microscope photograph of an actually manufactured indenter. The measured tilt angle β2 is shown in Figure 9. Specifically, the indenter was photographed using an optical microscope (Nikon: ECLIPS L150) to obtain an optical microscope photograph. To accurately measure the tilt angle β2 from an optical microscope image with a shallow depth of field, the indenter was fixed to the sample stage of the microscope so that the perpendicular line P drawn from the vertex 15 of the first portion 10 of the indenter to the bottom surface 11 of the first portion 10 was perpendicular to the optical axis of the optical microscope. The focal position was adjusted to the boundary between the first portion 10 and the third portion 30 (the bottom surface 11 of the first portion 10). The obtained optical microscope photograph was analyzed using the image analysis software ImageJ or the angle measurement function of Microsoft PowerPoint to determine the tilt angle β2. Note that the measured tilt angle β2 was approximately the designed tilt angle β2 ± 1.0°.

[0058] Next, the indenter was attached to a microscope indenter to observe the contact surface with the sample. Figure 11 shows a diagram and photographs illustrating the setup required to attach the indenter to the microscope indenter. The indenter was attached to a glass substrate (Edmund Optics Japan, synthetic quartz glass, diameter: φ 20 mm, thickness: t 2.0 mm, Young's modulus: 73 GPa, flatness: 1λ, coating: UV-VIS (250-700 nm)) using a UV-curable optical adhesive (Edmund Optics Japan, Norland Optical Adhesive NOA60). The indenter was mounted in the housing via the glass substrate. Since the refractive index of diamond (n = 2.42) is extremely large compared to that of quartz glass (n = 1.46), a three-stage structure was created in which a sapphire plate (manufactured by Edmund Optics Japan, diameter: φ 10 mm, thickness: t 1.0 mm, n = 1.77) with a refractive index intermediate between the two was sandwiched between the indenter and the glass substrate.

[0059] The contact surface was observed using a coaxial epi-illumination method with an illumination device (Sigma Koki, LED illumination device, SLA-100A) attached to the optical microscope (Sigma Koki, Microscope, OUCI-2, long working distance objective: PAL-10 (magnification: 10x, NA: 0.28)) of the microindenter. Images were captured using an industrial USB camera (Imaging Source, DFK23UP1300, 1 / 2-inch CMOS, 1280x1024 (113 fps)) and recorded on a PC along with the corresponding load, indentation depth, and time. The load measurement device for the microindenter was a precision electronic balance (Mettler Toledo, Built-in Weighing Module WMS410, minimum display: 0.1 mg, rating: 410 g). It is equipped with a non-contact precision displacement meter (manufactured by Mestec, capacitance type displacement meter: M-2218, sensor: CB2K-01, resolution (filter: 100 Hz): 3.0 nm, full scale: 2000 μm), and can also measure the indenter's pressing depth.

[0060] Then, an indenter press-fit test was performed using a microindenter to evaluate the influence of differences in indenter shape on the observed images. The test specimens were made of polypropylene (PP). Figure 12 shows images of the contact surface between the indenter and the test specimens in Examples 1 to 4. In Figure 12, the press-fit load was 1.0 N.

[0061] 12, clear images of the contact surface were obtained using the indenters of Examples 1 to 4. Particularly clear images of the contact surface were obtained using the indenters of Examples 2 and 3 (especially Example 2).

[0062] Figure 13 shows the results of examining the effect of a sapphire plate (n = 1.77) inserted to adjust the refractive index difference between the indenter (diamond) and the substrate (quartz glass). The test specimen was polymethyl methacrylate (acrylic resin, PMMA). Figure 13 shows images of the contact surface for Examples 2 to 4 when a sapphire plate was used (top row) and when a sapphire plate (refractive index adjusting plate) was not used (bottom row). It was confirmed that the contact surface became clearer when a sapphire plate was used for all Examples 2 to 4. In Figure 13, the indentation load was 1.0 N.

[0063] Next, Figure 14 shows the results of comparing images of the contact surface (with sapphire plate) taken for Examples 2 to 4 using two types of polymer (PP: polypropylene (thermoplastic resin), PMMA: polymethyl methacrylate (acrylic resin)) as test specimens. The top row in Figure 14 is an image of the contact surface for polymethyl methacrylate (indentation load = 1.0 N), and the bottom row is an image of the contact surface for polypropylene (indentation load = 0.2 N). It was confirmed that, for all of Examples 2 to 4, a clearer contact surface was obtained for both types of polymer.

[0064] FIG. 15 shows an image of the contact surface of a PMMA specimen taken using the indenter of Comparative Example 1 under the same conditions as in Comparative Example 1, using the coaxial epi-illumination method with the same equipment as in the above experiment. In FIG. 15, the indentation load is 1.0 N. An image of the contact surface of PMMA taken using the indenter of Example 2 under the same conditions as in Comparative Example 1 is also shown. Note that a sapphire plate was not used in either Comparative Example 1 or Example 2. The indenter of Comparative Example 1 was a Berkovich-type indenter (manufacturer: Tokyo Diamond Tool Manufacturing Co., Ltd.; indenter body material: diamond). As shown in FIG. 13, it was confirmed that the indenter of Example 2 provided a clearer contact surface than the indenter of Comparative Example 1.

[0065] FIG. 16 shows an optical microscope photograph (bright-field image) of the indenter according to Example 5 taken from the side and an optical microscope photograph (bright-field image) taken from the tip side. The indenter according to Example 5 was manufactured from sapphire. As with Examples 1 to 4, the second portion of the indenter according to Example 5 is a truncated cone, and the designed inclination angle β2 is 68.0°. FIG. 16 also shows the inclination angle β2 measured by analyzing the optical microscope photograph. The diameter of the top surface of the second portion was 1.32 mm.

[0066] 17 shows an optical microscope photograph (bright-field image) taken from the side and the tip of the indenter according to Comparative Example 2. The indenter according to Comparative Example 2 is a Berkovich-type indenter made of sapphire, as in Example 5.

[0067] 18 shows images of the contact surface of a test specimen (PP) taken using the indenters according to Example 5 and Comparative Example 2. The images were taken without using a refractive index adjustment plate and with an indentation load of 0.2 N. As can be seen from FIG. 18, it was confirmed that the indenter according to Example 5 provided a clearer contact surface than the indenter according to Comparative Example 2.

[0068] 19 is an optical microscope photograph (bright-field image) taken from the side of the indenter according to Example 6. The indenter according to Example 6 was made of diamond. As illustrated in FIG. 6, the indenter according to Example 6 has a curved side surface 25 of the second portion 20 in a side view.

[0069] Figure 20 shows an image of the contact surface of a test specimen (PP, PMMA) taken using the indenter of Example 6. The refractive index adjustment plate (thickness t 0.5 mm, diameter Φ 2.5 mm) is made of sapphire. As can be seen from Figure 20, it was confirmed that a clear contact surface was also obtained in Example 6.

[0070] 21 shows an optical microscope photograph (bright-field image) taken from the side of the indenter of Example 7, and an image of the contact surface of a test specimen (PP) taken using the indenter of Example 7. The indenter of Example 7 was made of sapphire, and the inclination angle β2 (design) was 76.0°. The contact surface was imaged at an indentation load of 0.2 N. It was confirmed that a clear contact surface was also obtained in Example 7.

[0071] The circularity of the cross section of the second portion in Examples 1-7 exemplified above (cross section in a direction perpendicular to the perpendicular line P passing through the tip of the indenter) was measured using image analysis software ImageJ and was found to be 0.89 or more.

[0072] As can be seen from the above explanation, the indenter according to the present invention, by being provided with a second portion in addition to a first portion, can obtain a good contact surface suitable for microindentation. With conventional indenters (normal Berkovich-type indenters), special oblique illumination was required to obtain a clear image of the contact surface (an image showing high contrast between the contact surface and the background). However, with this technology, a high contrast between the contact surface and the background can be easily achieved using a general-purpose coaxial epi-illumination device and an optical microscope. Using this technology, the contact surface can be clearly imaged using only coaxial epi-illumination. [Explanation of symbols]

[0073] 10: 1st part 11: Bottom 13: Side 15: Vertex 20 :Second part 21: Bottom 23:Top surface 25: Side 30: 3rd part 40: 4th part 41: Bottom 90: Test equipment 100: Indenter 200: Lighting equipment 300: Microscope 301: Objective lens 303: Imaging device 400: Loading device 500: Measuring equipment B: Housing S: Test piece

Claims

1. An indenter formed of a transparent material for applying a load to a test specimen, comprising a first portion and a second portion; the first portion has a triangular pyramid shape, and a tip of the first portion contacts the test piece; the second portion is located on the opposite side of the tip of the first portion from the bottom surface of the first portion, and has a circular cross section in a direction perpendicular to a perpendicular line drawn from the tip of the first portion toward the bottom surface of the first portion, a bottom surface of the first portion and a bottom surface of the second portion are parallel to each other; the perpendicular line passes through the center of the bottom surface of the second portion, the area of the second portion in the cross section increases continuously from the first portion side, The angle at which the side surface of the second portion is inclined with respect to a plane parallel to the bottom surface of the second portion is 45.0° or more and 80.0° or less. Indenter.

2. the transparent material is diamond; The angle is equal to or greater than 50.0° and equal to or less than 60.0°. The indenter of claim 1.

3. the transparent material is sapphire; The angle is equal to or greater than 50.0° and equal to or less than 80.0°. The indenter of claim 1.

4. The indenter of claim 1 is pressed into a test piece, and an image of the contact surface where the indenter and the test piece come into contact is obtained through an objective lens while the indenter is irradiated with light. Test method.

5. Light is irradiated onto the indenter in a direction parallel to the optical axis of the objective lens. The test method of claim 4.

6. The indenter is fixed using a substrate; a refractive index adjusting plate is provided between the indenter and the substrate; The refractive index of the refractive index adjusting plate is a value between the refractive index of the indenter and the refractive index of the substrate. The test method of claim 4.

7. The indenter of claim 1; a load device that moves at least one of the test piece and the indenter toward the other so as to press the indenter into the test piece; an illumination device that irradiates the indenter with light; and a microscope including an objective lens for obtaining an image of the contact surface where the indenter and the test piece come into contact. Test equipment.

8. a substrate for fixing the indenter; a refractive index adjusting plate provided between the indenter and the substrate, The refractive index of the refractive index adjusting plate is a value between the refractive index of the indenter and the refractive index of the substrate. The test device of claim 7.

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