JP2014105998A - Indentation test method and indentation test device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an indentation test method and an indentation device that can efficiently measure a physical property value with sufficient accuracy, even for a thin test object such as a sheet and a film.SOLUTION: An indentation test method measuring an indentation amount and an indentation load by pushing an indenter to a sample, includes a movable step in which the indenter and the sample are made close to each other by a first actuator 15, and an indentation step in which the indentation amount and the indentation load are measured while pushing the indenter to the sample with a second actuator 16. The second actuator 16 is more movable on a fine pitch compared to the first actuator 15.

Description

  The present invention relates to an indentation test method and an indentation test apparatus, and enables measurement of physical properties with sufficient accuracy even for thin sheets, films, and the like.

  Conventionally, a tensile test has been performed as a test for examining physical properties such as deformation of various materials such as metals. Although the tensile test is generally used as an objective evaluation method, it is necessary to prepare a test piece, and thus it is difficult to apply depending on the test object.

  On the other hand, since the indentation test does not require preparation of a test piece, minimally invasive measurement is possible.

  It has been known that Hertz's elastic contact theory can be applied to this indentation test (Non-Patent Document 1). Therefore, the indentation test can sufficiently measure the physical property value even for a test object to which the tensile test cannot be applied.

  Patent Document 1 proposes a method for measuring the Young's modulus of a soft material that is largely deformed by pressing, without being affected by the thickness of the test object, by extending the Hertz elastic contact theory. Patent Document 2 proposes a method for measuring viscoelasticity by an indentation test. Further, Patent Document 3 proposes a method for measuring physical property values of biological tissues such as muscles.

  Here, the indentation test measures a physical property value of a sample by pressing an indenter against the sample. Regarding such a pressing mechanism, Patent Document 4 proposes a method of applying a constant load in a wide frequency band by using two types of actuators having different frequency characteristics in parallel in a processing apparatus. .

International Publication No. WO2010 / 084840 Pamphlet JP2011-137667A JP 2011-257321 A Japanese Patent No. 4966394

T. Sawa, Practical Material Mechanics, (2007), pp.258-279, Nikkei Business Publications, Inc. (in Japanese)

  By the way, in the conventional indentation test, there existed a problem which cannot measure a physical-property value with sufficient precision about thin test objects, such as a sheet | seat and a film. In addition, this type of test naturally requires an efficient test.

  The present invention has been made in consideration of the above-mentioned problems, and an indentation test method and an indentation capable of efficiently measuring physical property values with sufficient accuracy even for thin test objects such as sheets and films. Providing test equipment.

(1) In the indentation test method in which an indenter is pushed into a sample and the indentation amount and indentation load are measured.
A movable step of bringing the indenter and the sample closer by a first actuator;
A pressing step for measuring the pressing amount and the pressing load while pressing the indenter into the sample by a second actuator, and the second actuator is movable at a fine pitch as compared with the first actuator. It is a possible actuator.

  According to (1), after the ball indenter is brought close to the sample at a high speed, the indenter can be pushed in at a fine pitch to measure the pushing amount and the pushing load, thereby increasing the pushing load accompanying the pushing. Even if it becomes remarkable, a physical property value can be measured with sufficient accuracy in a short time. Therefore, it is possible to accurately and efficiently measure the physical property value of a thin test object such as a sheet or a film.

  (2) In (1), the second actuator is an actuator based on a voice coil motor.

  According to (2), with a more specific configuration, it is possible to efficiently and accurately measure physical property values even for thin test objects such as sheets and films.

  (3) In (1) or (2), there is provided a physical property value calculating step of calculating a physical property value of the sample from the indentation amount measured in the indentation step and the indentation load.

  According to (3), the physical property value can be calculated without separately processing the indentation amount and the indentation load.

  (4) In (3), the physical property value is Young's modulus.

  According to (4), the physical property value by Young's modulus can be measured.

(5) In an indentation test device that measures an indentation amount and an indentation load by pushing an indenter into a sample.
A push-in amount detecting unit for detecting the push-in amount;
An indentation load measuring unit for measuring an indentation load by the indenter; and
A first actuator for bringing the indenter and the sample closer;
A second actuator for pushing the indenter into the sample,
The second actuator is an actuator that is movable with a finer pitch than the first actuator.

  According to (5), after the ball indenter is brought close to the sample at a high speed, the indenter can be pushed in with a fine pitch to measure the pushing amount and the pushing load, thereby increasing the pushing load accompanying the pushing. Even if it becomes remarkable, a physical-property value can fully be measured in a short time. Therefore, it is possible to accurately and efficiently measure the physical property value of a thin test object such as a sheet or a film.

  (6) In (5), the second actuator is an actuator based on a voice coil motor.

  According to (6), a physical property value can be measured with high accuracy even for a thin test object such as a sheet or a film with a more specific configuration.

  (7) In (5) or (6), a Young's modulus calculation unit that calculates a Young's modulus of the sample from the indentation amount and indentation load is provided.

  According to (7), the physical property value by Young's modulus can be measured.

  According to the present invention, a physical property value can be efficiently measured with sufficient accuracy even for a thin test object such as a sheet or a film.

It is a figure where it uses for description of the evaluation method of the physical-property value which concerns on this invention. It is a characteristic curve figure which shows the relationship between indentation amount and indentation load. It is a characteristic curve figure in case there exists distance until a ball indenter contacts a sample. It is a side view which shows the structure of the main-body part which concerns on the structure of the vertical actuator for coarse movement, and the vertical actuator for fine movement. It is a figure which shows the whole structure of an indentation test apparatus. It is a figure with which it uses for description of the process sequence of a control part.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a diagram for explaining an evaluation method according to the first embodiment of the present invention. When a sufficiently hard ball indenter 2 is pushed into the semi-infinite body sample 1, the relationship between the push load F and the push amount δ related to the push of the ball indenter 2 is expressed by the following equation according to Hertz's elastic contact theory. .

  Here, φ is the diameter of the ball indenter 2, E is the Young's modulus of the sample 1, and ν is the Poisson's ratio of the sample 1. A is a coefficient, and is hereinafter referred to as a softness coefficient as appropriate.

  Thus, if the indentation amount δ is varied and the indentation load F is measured, a characteristic curve as shown in FIG. 2 can be obtained. Therefore, for example, the softness coefficient A can be obtained by the least square method or the like using the measured value (indicated by the symbol X), and further, the Young's modulus E can be obtained by the following equation obtained by modifying the equation (2). .

  When the ball indenter 2 is pushed toward the sample 1 and has a distance until the ball indenter 2 actually contacts the sample 1, the characteristic curve shown in FIG. 3 is used instead of the characteristic curve shown in FIG. Is obtained. Therefore, in this case, by subtracting the pushing amount δ0 when the ball indenter 2 contacts the sample 1 from the pushing amount δ, the pushing amount δ can be corrected to obtain the softness coefficient A and the Young's modulus E.

  However, when the thickness of the sample 1 is reduced, an increase in indentation load accompanying indentation becomes significant, and the expression (1) based on Hertz's elastic contact theory cannot be applied with high accuracy. In this case, the relationship between the indentation load F and the indentation amount δ can be expressed with high accuracy by applying the following equation.

  Here, B is a coefficient representing the influence of the thinness of the sample on the load. Therefore, even in such a thin sample, the coefficient B representing the influence on the load is obtained from the measurement result of the indentation load F and the indentation amount δ as described above with respect to the expressions (1) and (2), and the softness is determined. The thickness coefficient A and Young's modulus E can be obtained.

  By the way, in this embodiment, the indentation load F and the indentation amount δ are accurately determined by measuring the indentation load F and the indentation amount δ by measuring the indentation load F and the indentation amount δ in this manner. It is necessary to measure. In particular, when the thickness of the sample is thin, the indentation load F greatly changes with a small amount of indentation δ, so that it is necessary to measure the indentation amount δ in a minute amount with high accuracy.

  For this purpose, it is necessary to control and measure the pushing amount δ with high resolution. However, if the indentation amount δ is simply measured by being changed by a minute amount, as described above with reference to FIG. 3, after the indentation of the ball indenter 2 toward the sample 1 is started, the ball indenter 2 is actually applied to the sample 1. If there is a distance until contact is made, the measurement takes time, and the efficiency is significantly degraded.

  Therefore, in this embodiment, a coarse motion vertical actuator (first actuator) that is a coarse motion actuator and a fine motion actuator that is movable at a fine pitch compared to the coarse motion vertical actuator. The ball indenter 2 is configured to be movable by two types of actuators (second actuator), and the indentation test is executed by switching the driving of the two types of actuators.

  That is, FIG. 4 is a view showing the main body in the indentation test apparatus according to this embodiment. The main body 11 is provided with a table 12 on which the sample 1 is placed, and an arm 13 is provided above the table 12 so as to hold the ball indenter 2. In the main body 11, a horizontal actuator 14 is provided on the arm 13, and as indicated by an arrow A, the ball indenter 2 is moved in the in-plane direction (X and Y directions) of the table 12 by the horizontal actuator 14. Thus, the indentation test apparatus is configured to test various portions of the sample 1 by moving the ball indenter 2 in the horizontal direction by driving the horizontal actuator 14.

  The main body 11 is further provided with a stage 17 that is movable in the vertical direction as indicated by an arrow B through a coarse movement vertical actuator 15 and a fine movement vertical actuator 16 in this order. The stage 17 is provided with a ball indenter 2 through a load cell 18 and a load shaft 19 in this order. Here, the coarse motion vertical actuator 15 is a movable mechanism using, for example, a ball nut, and is configured to be able to move the stage 17 up and down at high speed by rotating a motor. On the other hand, the fine movement vertical actuator 16 is constituted by a voice coil motor, for example, and is configured to be able to move the stage 17 in the vertical direction with a fine pitch with high accuracy. In this embodiment, the fine movement vertical actuator 16 is configured to have a yoke having a sufficient length, thereby ensuring a sufficient movable distance in the vertical direction. Accordingly, the indentation test apparatus, as shown by the arrow C, moves the ball indenter 2 close to the sample 1 at a high speed by the coarse movement vertical actuator 15 and then drives the fine movement vertical actuator 16 with a fine pitch and with high accuracy. 1 so that it can be pushed in. Further, the load cell 18 can detect the indentation load caused by the indentation.

  FIG. 5 is a diagram showing the overall configuration of the indentation test apparatus. Further, the main body 11 is provided with a horizontal position detection unit 21 for detecting the position of the ball indenter 2 in the horizontal direction. The horizontal position detection unit 21 includes, for example, a potentiometer and a peripheral circuit that is used to drive the potentiometer. The main body 11 is provided with a coarse movement vertical position detection unit 22 for detecting the position of the ball indenter 2 in the vertical direction by the coarse movement vertical actuator 15. Here, the coarse movement vertical position detection unit 22 includes, for example, a potentiometer and a peripheral circuit for driving the potentiometer. The main body 11 is provided with a fine movement vertical position detection unit 23 for detecting the position of the ball indenter 2 in the vertical direction by the fine movement vertical actuator 16. Here, the fine movement vertical position detection unit 23 is configured by an optical position detection mechanism using, for example, a laser, and is configured so as to be able to measure the pushing amount with high accuracy. Based on the control, the push-in amount can be controlled with high precision and fine pitch.

  The indentation test apparatus 31 is configured by connecting the main body 11 to a control unit 32. Here, the control unit 32 is a part that controls the operation of the main body unit 11 and processes the measurement result of the main body unit 11. The control unit 32 is configured by a computer, for example, and each functional block illustrated in FIG. 5 is configured by executing a program related to the indentation test apparatus 31.

  In the control unit 32, the pushing start position control unit 33 is a functional block that is used to drive the coarse movement vertical actuator 15. In this embodiment, the coarse movement vertical actuator 15 is moved by the operator's operation to move the coarse indenter 2 to the sample 1. After the ball indenter 2 is brought close to the sample 1 and stopped until just before contact, the coarse motion vertical actuator 15 is held at the stop position. It should be noted that at the timing of stopping the driving of the coarse motion vertical actuator 15 immediately before the contact of the ball indenter 2, the ball indenter 2 is moved up and down in advance and the indentation load is measured by the load cell 18 to obtain automatically. Alternatively, it may be set by inputting the sample thickness or the like by the operator.

  The pushing amount control unit 34 is a functional block for driving the vertical actuator 16 for fine movement, and pushes the ball indenter 2 held immediately before contacting the sample 1 by the pushing start position control unit 33 into the sample 1. In this pressing, for example, the pressing amount is monitored by the vertical position detecting unit 23 for fine movement, and the pitch set by the operator is used, and further, the pitch according to the thickness of the sample input in advance is executed. .

  The coefficient calculation unit 35 calculates a softness coefficient A and a coefficient B representing the influence of the thinness of the sample on the load based on the pressing amount detected by the fine movement vertical position detection unit 23 and the load detected by the load cell 18. The Young's modulus calculator 36 calculates the Young's modulus E using the calculation result of the coefficient calculator 35. The storage unit 37 records and holds the calculated Young's modulus E together with the measured indentation amount, indentation load, and the like. In addition to these functional blocks, the control unit 32 includes a functional block that receives an operator input, a functional block that drives the horizontal actuator 14, and the like.

  FIG. 6 is a flowchart showing a processing procedure of the control unit 32 using these functional blocks. In the indentation test apparatus 31, the setting of a measurement position etc. is received from an operator by the start of the processing program concerning an indentation test apparatus, and the horizontal actuator 14 etc. are moved (step SP1, SP2). Subsequently, in response to an instruction to start measurement by the operator, the coarse motion vertical actuator 15 is driven to move the ball indenter 2 to the vicinity of the surface of the sample 1 (steps SP3 and SP4). Subsequently, the indentation load is measured by the load cell 18 while pushing the ball indenter 2 into the sample 1 at a constant pitch by the fine movement vertical actuator 16 (step SP5), and the coefficient A is calculated from the measurement result of the indentation load and the corresponding indentation amount. , B are calculated (step SP6), and the Young's modulus at a predetermined indentation amount is calculated using the calculated coefficients A, B (step SP7).

  According to the above configuration, the ball indenter 2 can be moved by two types of actuators, which are the coarse actuator vertical actuator that is the first actuator and the fine actuator vertical actuator that is movable at a finer pitch than the first actuator. Even if the increase in indentation load due to indentation becomes significant by switching the drive of these two types of actuators and executing the indentation test, the physical property values can be sufficiently obtained in a short time. It can be measured. Thereby, a physical property value can be measured accurately and efficiently even for a thin test object such as a sheet or a film.

  In addition, since the second actuator is an actuator based on a voice coil motor, a physical property value can be accurately measured even for a thin test object such as a sheet or a film with a more specific configuration.

  Further, by providing a physical property value calculating step for calculating the physical property value of the sample from the measured indentation amount and indentation load, the physical property value can be calculated without separately processing the indentation amount and the indentation load.

  Further, since the physical property value is the Young's modulus, the physical property value based on the Young's modulus can be measured.

[Other Embodiments]
As mentioned above, although the specific structure suitable for implementation of this invention was explained in full detail, this invention can change the structure of the above-mentioned embodiment variously in the range which does not deviate from the meaning of this invention.

  That is, in the above-described embodiment, the case where the Young's modulus is obtained by the indentation amount and the indentation load is described. However, the present invention is not limited to this, and is widely applied to, for example, measuring viscoelasticity by indentation indentation. Time can be shortened, and measurement accuracy can be improved.

  In the above-described embodiment, the case where the ball indenter is brought close to the vicinity of the sample by the first actuator has been described. However, the present invention is not limited to this, and the second actuator is used together with the first actuator. A ball indenter may be brought close to the vicinity.

  In the above-described embodiment, the case where the ball indenter is moved with respect to the sample has been described. However, the present invention is not limited to this, and the point is that the sample and the ball indenter are brought close to each other and the ball indenter is pushed into the sample. The table side may be moved by the first and / or second actuator.

  In the above-described embodiment, the case where the ball indenter is moved in the vertical direction by the first and second actuators on the assumption that the sample is placed on the table has been described, but the present invention is not limited to this. The present invention can be widely applied to the case where the indentation test is performed by moving in the horizontal direction.

  In the above-described embodiment, the case where the indentation test is performed using the spherical indenter is described. However, the present invention is not limited to this, and indenters having various shapes such as a cylindrical indenter are used. It can be widely applied to indentation tests using

DESCRIPTION OF SYMBOLS 1 Sample 2 Ball | bowl indenter 11 Main-body part 12 Table 13 Arm 14 Horizontal actuator 15 Coarse movement vertical actuator 16 Fine movement vertical actuator 17 Stage 18 Load cell 19 Load axis 21 Horizontal position detection part 22 Coarse movement vertical position detection part 23 Fine movement vertical position detection Unit 31 indentation test device 32 control unit 33 indentation start position control unit 34 indentation amount control unit 35 coefficient calculation unit 36 Young's modulus calculation unit

Claims (7)

In the indentation test method of pushing the indenter into the sample and measuring the indentation amount and indentation load,
A movable step of bringing the indenter and the sample closer by a first actuator;
A pressing step for measuring the pressing amount and the pressing load while pressing the indenter into the sample by a second actuator;
The indentation test method, wherein the second actuator is an actuator movable with a finer pitch than the first actuator. The indentation test method according to claim 1, wherein the second actuator is an actuator based on a voice coil motor. The indentation test method according to claim 1, further comprising a physical property value calculation step of calculating a physical property value of the sample from the indentation amount and the indentation load measured in the indentation step. The indentation test method according to claim 3, wherein the physical property value is Young's modulus. In the indentation test device that measures the indentation amount and indentation load by pushing the indenter into the sample,
A push-in amount detecting unit for detecting the push-in amount;
An indentation load measuring unit for measuring an indentation load by the indenter; and
A first actuator for bringing the indenter and the sample closer;
A second actuator for pushing the indenter into the sample,
The indentation test apparatus, wherein the second actuator is an actuator movable with a fine pitch as compared with the first actuator. The indentation test method according to claim 5, wherein the second actuator is an actuator based on a voice coil motor. The indentation test apparatus according to claim 5, further comprising a Young's modulus calculator that calculates a Young's modulus of the sample from the indentation amount and the indentation load.

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