JP5935180B2 - Indentation test method and indentation test apparatus - Google Patents

Description

  The present invention relates to a novel indentation test method. The present invention also relates to a novel indentation test apparatus using the above indentation test method.

  Tensile tests used for investigating properties such as deformation of metal materials are common as objective evaluation methods. However, it is necessary to cut out test specimens from samples and the like. It is difficult to apply to other materials and living tissues.

  On the other hand, the indentation test that is generally used for measuring the hardness of materials similarly enables minimally invasive measurement because it is not necessary to cut out a test piece. In this indentation test, it is known that Hertz's elastic contact theory has high reliability for metal materials (for example, see Non-Patent Document 1).

  In addition, there are several examples in which the indentation test is used for measuring the compositional relationship of soft materials with large deformations such as biological soft tissues (for example, see Non-Patent Documents 2 to 5).

  However, in the measurement of the compositional relationship of soft materials with large deformation such as living soft tissue by the indentation test described above, the high reliability of Hertz's elastic contact theory is shown by Toshiyuki Sawa, but it is within the range of minute deformation. In addition, Osamu Takatani et al. Applied to soft biological tissues is a technique based on N value which is essentially equivalent to Hertz's elastic contact theory. In addition, the method of Yoshiki Arima, who identifies from the energy loss in the loading / unloading process together with the N value, assumes a semi-infinite body as well as Hertz's elastic contact theory, and does not consider the effect of thickness. . Regarding this thickness, there is a research report of N.E.WATERS, but it shows the effect, and has not yet been evaluated in association with the stress-strain relationship. Furthermore, although there is a report on application to polymer materials by Tatsuya Ishibashi and others focusing on irreversible behavior, there is a problem that application to soft materials with high reversibility is difficult.

  Regarding this difficult problem, Sakuma et al. Devised a method that can measure the Young's modulus useful for constitutive relations of soft materials with large deformation without being affected by the thickness from the indentation test by extending Hertz's elastic contact theory. (Refer to Patent Document 1; hereinafter referred to as “prior application”).

  Sakuma et al.'S earlier application evaluated the relationship between the indentation load and indentation amount obtained from the indentation test using a formula based on Hertz's elastic contact theory, and used various Young soft materials obtained from this theory. Can be expressed by objective numerical data.

  However, since it is a method that can express a wide range of soft materials of extremely various shapes with objective numerical data, the device made in accordance with the prior application of Sakuma et al. There was a difficulty in realizing a test system that required high-precision numerical data related to a wide range of materials.

  The inventor has disclosed technical contents related to the present invention (see Patent Document 2 and Non-Patent Documents 6 to 13).

International Publication No. WO / 2010/084840 Pamphlet JP2011-137667A

T. Sawa, Practical Material Mechanics, (2007), pp.258-279, Nikkei Business Publications, Inc. (in Japanese) O. Takatani, T. Akatsuka, The Clinical Measurement Method of Hardness of Organism, Journal of the Society of Instrument and Control Engineers, Vol.14, No.3, (1975), pp.281-291. (In Japanese) Y. Arima, T. Yano, Basic Study on Objectification of Palpation, Japanese Journal of Medical Electronics and Biological Engineering, Vol.36, No.4, (1998), pp.321-336. (In Japanese) N. E. Waters, The Indentation of Thin Rubber Sheets by Spherical indentors, British Journal of Applied Physics, Vol. 16, Issue 4, (1965), pp.557-563. T. Ishibashi, S. Shimoda, T Furukawa, I. Nitta and H. Yoshida, The Measuring Method about Young's Modulus of Plastics Using the Indenting Hardness Test by a Spherical Indenter, Transactions of the Japan Society of Mechanical Engineers, Series A, Vol .53, No.495, (1987), pp.2193-2202. (In Japanese) M. Tani, A. Sakuma, M. Ogasawara, M. Shinomiya, Minimally Invasive Evaluation of Mechanical Behavior of Biological Soft Tissue using Indentation Testing, No.08-53, (2009), pp.183-184. M. Tani, A. Sakuma, Measurement of Thickness and Young ’s Modulus of Soft Materials by using Spherical Indentation Testing, No. 58, (2009), pp. 365-366. A. Sakuma, M. Tani, Spherical Indentation Technique for Low-invasive Measurement for Young ’s Modulus of Human Soft Tissue, No.09-3, (2009), pp.784-785. M. Tani and A. Sakuma, Evaluation of Thickness and Young's Modulus of Soft Materials by using Spherical Indentation Testing, Transactions of the Japan Society of Mechanical Engineers, Series A, Vol.75, No.755, (2009), pp.901 -908. (In Japanese) A. Sakuma, Softness Evaluation of Human Skin by Spherical Indentation imitating Palpation, The 36th Annual Meeting of Japan Cosmetic Science Society, Vol.36, (2011), p.79. (In Japanese) A. Sakuma, K. Tanabe, K. Kawagoe and M. Ogasawara, Evaluation of Thin Soft Tissues by Indentation System imitating Palpation, JSME Annual Meeting, Vol.2011, No.11-1 (DVD-ROM edition), p.J022054 , (2011). (In Japanese) A. Sakuma, Y. Zhang, Development of Softness Measurement System imitating Palpation, Chemical Engineering, Vol.57, No.1, p.66-70, (2012). (In Japanese) K. Tanabe, A. Sakuma, K. Kawagoe, T. Shimpo, Evaluation of Mechanical Behaviors of Human Artery by Cylinder Pinching Method, No.11-47, (CD-ROM edition), p.8D45, (2012). in Japanese)

  As described above, the indentation test method and indentation test apparatus for measuring flexibility are difficult to calculate numerical data related to flexibility with high accuracy in a flexibility measurement system that requires extremely wide range of numerical data. This is a problem to be solved.

  Therefore, from the indentation test method and indentation test equipment for measuring flexibility, a wide range of numerical data is measured according to the flexibility and shape of the sample, and a wide range of numerical data of samples of extremely diverse shapes is obtained. Development of a method and apparatus capable of calculating with high accuracy is desired.

The present invention has been made in view of such problems, and an object thereof is to provide a novel indentation test method.
Another object of the present invention is to provide a novel indentation test apparatus using the above indentation test method.

  In order to solve the above-mentioned problems and achieve the object of the present invention, the indentation test method of the present invention uses an indentation load acting on the indenter and an indentation amount of the indenter in the indentation test method in which an indenter is pushed into a sample. The softness coefficient of the sample is calculated together with the calculation of the reference point of the indentation amount at which the sample and the indenter are in contact with each other.

Here, although not necessarily limited, the Young's modulus E of the sample is preferably in the range of 10 Pa to 100 MPa.
Although not limited, the shape of the indenter is preferably a spherical shape, a flat end, or a cylindrical shape.
Although not limited, the diameter of the spherical or cylindrical indenter is preferably in the range of 1 × 10 ⁻⁸ to 1 m.
Although not limited, it is preferable that at least one of the calculated reference points / coefficients is multiplied by a weighting coefficient.

  The indentation test apparatus of the present invention is an indentation test apparatus that indents an indenter into a sample, a measurement unit for an indentation load acting on the indenter to be pushed in, a measurement unit for an indentation amount of the indenter, and a flexibility coefficient of the sample. A reference point / coefficient calculation unit that performs the calculation together with calculation of the reference point of the indentation amount at which the sample and the indenter contact, and a Young's modulus calculation that calculates the Young's modulus of the sample using the calculated flexibility coefficient It has the part.

Here, although not necessarily limited, the Young's modulus E of the sample is preferably in the range of 10 Pa to 100 MPa.
Although not limited, the shape of the indenter is preferably a spherical shape, a flat end, or a cylindrical shape.
Although not limited, the diameter of the spherical or cylindrical indenter is preferably in the range of 1 × 10 ⁻⁸ to 1 m.
Although not limited, it is preferable that at least one of the calculated reference points / coefficients is multiplied by a weighting coefficient.

  The present invention has the following effects.

  In the indentation test method of the present invention, an indenter is indented into a sample.In the indentation test method, the indentation load acting on the indenter and the indentation amount of the indenter are used to calculate the softness coefficient of the sample. Since it carries out together with calculation of the reference point of the indentation amount which the said indenter contacts, a novel indentation test method can be provided.

  The indentation test apparatus of the present invention is an indentation test apparatus that indents an indenter into a sample, a measurement unit for an indentation load acting on the indenter to be pushed in, a measurement unit for an indentation amount of the indenter, and a flexibility coefficient of the sample. A reference point / coefficient calculation unit that performs the calculation together with calculation of the reference point of the indentation amount at which the sample and the indenter contact, and a Young's modulus calculation that calculates the Young's modulus of the sample using the calculated flexibility coefficient Therefore, a new indentation test apparatus can be provided.

It is a figure which shows the contact state of a spherical indenter and a plane sample. It is a figure which shows the relationship between the load obtained from experiment and calculation, and pushing amount. It is a figure which shows the reference point of the pushing amount in the relationship between a load and pushing amount. It is a figure which shows the reference point of the pushing amount and load in the relationship between a load and pushing amount. It is a figure which shows the reference point and thickness coefficient of the pushing amount in the relationship between a load and pushing amount. It is a figure which shows the indentation test of a ball | bowl indenter and a flat sample. It is a figure which shows the indentation test of a flat end indenter and a spherical sample. It is a figure which shows the indentation test of a cylindrical indenter and a cylindrical sample. It is a figure which shows the outline of an indentation testing machine. It is a figure which shows the structure of an indentation test apparatus.

  Hereinafter, embodiments for carrying out the invention relating to the indentation test method and the indentation test apparatus will be described.

  In the indentation test method, an indenter is pushed into the sample. In the indentation test method, the indentation load acting on the indenter and the indentation amount of the indenter are used to calculate the flexibility coefficient of the sample. This is a method that is carried out in conjunction with the calculation of the reference point of the indentation amount to be contacted.

  The indentation test apparatus pushes an indenter into a sample.In the indentation test apparatus, a measurement unit for an indentation load acting on the indenter to be pushed in, a measurement unit for an indentation amount of the indenter, and calculation of a flexibility coefficient of the sample, A reference point / coefficient calculation unit that is implemented in conjunction with calculation of the reference point of the indentation amount at which the sample and the indenter contact each other, and a Young's modulus calculation unit that calculates the Young's modulus of the sample using the calculated flexibility coefficient Device.

The indentation test evaluation method will be described. First, a method for calculating the Young's modulus of a sample in an indentation test in which an indenter is pushed into the sample will be described.
When pressing a sufficiently hard ball indenter against a semi-infinite sample with a flat surface, using Hertz's elastic contact theory, the relationship between indentation load F and indentation amount δ shown in Fig. 1 is expressed as follows: The

  However, the coefficient A has the following relationship, and is hereinafter referred to as “softness coefficient”.

  Here, φ, E, and ν are the diameter of the ball indenter, the Young's modulus (hereinafter also referred to as “Young's modulus”), and the Poisson's ratio (hereinafter also referred to as “Poisson ratio”) of the sample, respectively.

  When the relationship between the load F and the indentation amount δ is obtained from the indentation test as indicated by the x mark in FIG. 2, the softness coefficient A at this time is the coefficient A of the formula (Equation 1) so as to match this x mark. It can be obtained by determining the least square method or the like.

  As a method of determining the coefficient A of the equation (Equation 1) from the indentation test, for example, when considering the nonlinear least square method, when the experimental data indicated by x in FIG. 2 is represented by yi (i = 0 to n), the basic to be solved Let the equation be the equation (Formula 1).

Further, an error ri between F (A) and the experimental data yi using the expression (Equation 1) as a function is expressed as follows.

The correction amount ΔA of the coefficient A that minimizes the error ri as a whole is expressed as follows.

Here, the partial differentiation of the error ri by the coefficient A is expressed as follows.

  By repeatedly using the correction amount ΔA of the equation (Equation 4), the flexibility coefficient A that gives the equation (Equation 1) that is closest to the experimental data represented by the thick line in FIG. 2 can be obtained.

Furthermore, as shown in FIG. 3, in the relationship between the load F obtained from the indentation test and the indentation amount δ, when the contact point δ ₀ between the sample and the indenter does not satisfy δ ₀ = 0, the indentation load F and the indentation amount shown in FIG. The relationship of δ is expressed as follows using the contact point δ ₀ between the sample and the indenter as a reference point of the indentation amount and using the flexibility coefficient A of the equation (Equation 2).

Further, an error ri between F (A, δ ₀ ) and the experimental data yi using the formula (Equation 6) as a function is expressed as follows.

The coefficient A that minimizes the error ri as a whole and the correction amounts ΔA and Δδ ₀ of the reference point δ ₀ are expressed as follows.

Here, the partial differentiation of the error ri by the coefficient A and the partial differentiation of the error ri by the reference point δ ₀ are expressed as follows.

By repeatedly using the correction amounts ΔA and Δδ ₀ in this equation (Equation 8), the flexibility coefficient A that gives the equation (Equation 6) that is closest to the experimental data and the reference point δ ₀ of the indentation amount are combined with high accuracy. Can be requested.

Here, equation (9), in the soft of factor A and the amount of pushing by the reference point [delta] ₀ correction using equation (10), such as by the magnitude relation of the reference point [delta] ₀ of soft of coefficients A and depression depth In some cases, the correction is insufficient and the accuracy of the obtained numerical data is low.

  Therefore, for the purpose of obtaining numerical data with high accuracy, a method is considered in which the values to be obtained are multiplied by respective weighting factors in advance in accordance with the magnitude relationship of the values to be corrected.

As shown in FIG. 3, when the contact point δ ₀ between the sample and the indenter does not satisfy δ ₀ = 0 in the relationship between the load F obtained from the indentation test and the indentation amount δ, the indentation load F and the indentation amount δ shown in FIG. Using the contact point δ ₀ between the sample and the indenter as a reference point for the indentation amount, and using the flexibility coefficient A in the equation (Equation 2), the reference point δ ₀ and the coefficient A are set to the respective weighting factors kd and ka. Substituting the multiplied relationship kdδ ₀ ', kaA', it is expressed as follows.

Further, an error ri between F (A ′, δ ₀ ′) and the experimental data yi using the expression (Equation 11) as a function is expressed as follows.

The coefficient A ′ that minimizes the error ri as a whole and the correction amounts ΔA ′ and Δδ ₀ ′ of the reference point δ ₀ ′ are expressed as follows.

Here, the partial differentiation of the error ri by the coefficient A ′ and the partial differentiation of the error ri by the reference point δ ₀ ′ are expressed as follows.

By repeatedly using the correction amounts ΔA ′ and Δδ ₀ ′ of this equation (Equation 13), the flexibility coefficient A ′ that gives the equation (Equation 11) that is closest to the experimental data and the reference point δ ₀ ′ of the indentation amount are obtained. Further, the softness coefficient A and the indentation reference point δ ₀ can be obtained by multiplying the weight coefficients ka and kd, respectively.

Here, there are cases where the correction may be insufficient due to the magnitude relationship between the softness factor A and the reference point δ ₀ of the indentation amount, etc.The flexibility coefficient A and the indentation amount using the equations (Equation 9) and (Equation 10) For the correction of the reference point δ _0, the softness coefficient A and the indentation reference point δ ₀ according to the equations (Equation 14) and (Equation 15) using the weighting factors ka and kd corresponding to the magnitude relationship of the values to be corrected, etc. In this correction, it is possible to eliminate the influence that the correction becomes insufficient due to the magnitude relationship between the softness coefficient A and the reference point δ ₀ of the indentation amount.

In addition, for the purpose of obtaining numerical data with high accuracy, the method of obtaining the value to be obtained by multiplying each value by a weighting factor in advance, corresponding to the magnitude relationship of the value to be corrected, etc. is performed by using the softness coefficient A and the indentation amount reference point δ _It can be used other than when ₀ is requested.

As shown in FIG. 4, when the relationship between the load F obtained from the indentation test and the indentation amount δ does not become the load F value F ₀ = 0 at the contact point δ ₀ between the sample and the indenter due to the influence of the weight of the indenter, etc. The relationship between the indentation load F and the indentation amount δ shown in FIG. 4 uses the softness coefficient A in the equation (Equation 2) with the load F value F ₀ at the contact point δ ₀ between the sample and the indenter as the reference point of the load. Thus, the reference points F ₀ , Δ ₀ and the coefficient A are replaced with the relations kfF ₀ ′, kdδ ₀ ′, kaA ′ obtained by multiplying the respective coefficients kf, kd, ka, and are expressed as follows.

Further, an error ri between F (A ′, Δ ₀ ′, F ₀ ′) and the experimental data yi using the expression (Equation 16) as a function is expressed as follows.

The coefficient A ′ that minimizes the error ri as a whole and the correction amounts ΔA ′, Δδ ₀ ′, ΔF ₀ ′ of the reference points δ ₀ ′, F ₀ ′ are expressed as follows.

Here, the polarization by the respective coefficients of the error ri A 'partial differential by the reference point [delta] ₀ error ri' partial differential by the formula (Equation 14) is expressed by equation (15), the reference point F ₀ of the error ri ' Differentiation is expressed as follows.

By repeatedly using the correction amounts ΔA ', Δδ ₀ ', ΔF ₀ 'in this equation (Equation 18), the softness coefficient A' that gives the equation (Equation 16) closest to the experimental data and the reference point for the indentation amount δ ₀ ′, F ₀ ′ can be obtained, and the weight coefficient ka, kd, kf can be multiplied to obtain the softness coefficient A, the indentation reference point δ ₀ , and the load reference point F _0. .

Alternatively, as shown in FIG. 5, in the relationship between the load F obtained from the indentation test and the indentation amount δ, the increase in the load F with respect to the indentation amount δ is raised to the 1.5th power of the indentation amount δ due to the small thickness of the sample. When it is not proportional, the relationship between the indentation load F and the indentation amount δ shown in FIG. 5 is that the coefficient B is the thickness coefficient, the flexibility coefficient A of the equation (Equation 2) is used, the coefficient B, the reference point δ _0, and the coefficient Substituting the relations kbB ′, kdδ ₀ ′, and kaA ′ by multiplying A by the respective weighting factors kb, kd, and ka, they are expressed as follows.

Further, an error ri between F (A ′, Δ ₀ ′, B ′) having the function of Expression (Equation 20) and the experimental data yi is expressed as follows.

The coefficients A ′, the reference points Δ ₀ ′, and the correction amounts ΔA ′, Δδ ₀ ′, ΔB ′ for minimizing the error ri as a whole are expressed as follows.

Here, the partial differentiation of the error ri by the coefficient A ′, the partial differentiation of the error ri by the reference point δ ₀ ′, and the partial differentiation of the error ri by the reference point B ′ are expressed as follows.

By repeatedly using the correction amounts ΔA ′, Δδ ₀ ′, ΔB ′ of this equation (Equation 22), the flexibility coefficient A ′ that gives the equation (Equation 20) closest to the experimental data and the reference point δ of the indentation amount ₀ ′ and thickness coefficient B ′ can be obtained, and the weight coefficient ka, kd, and kb can be multiplied to obtain the softness coefficient A, the indentation reference point δ ₀ , and the thickness coefficient B.

In any of the above methods, by using the obtained coefficient A, the Young's modulus E can be obtained from the following equation (Equation 2).

  Although the indentation test has been described above by using the indentation test in which a ball indenter is indented against a sample having a flat surface as shown in FIG. 6, the indentation test is performed on a spherical sample shown in FIG. A push-in test for pushing a flat end indenter or a push-in test for pushing a cylindrical indenter into a cylindrical sample shown in FIG. 8 can be used.

  Further, in order to obtain the relationship between the load F and the indentation amount δ from the indentation test, the above description has been made using the least square method. However, as the obtaining method, a method such as a quadratic programming method or a non-linear programming method can be used.

  As shown above, the method of calculating the softness coefficient together with other reference points from the indentation test can reduce the influence of the sample size relationship and the error in the test results, so that all of the multiple numerical data can be increased. It can be used as a method for obtaining with accuracy. Also, when obtaining multiple numerical data with different magnitude relationships from the indentation test, the method of multiplying the weighting factor according to the magnitude relationship of the multiple numeric values to be obtained can negate the influence of the magnitude relationship of the numeric data to be obtained. It can be used as a method for obtaining all of a plurality of numerical data with high accuracy.

  Next, an indentation test apparatus for obtaining flexibility according to the present invention will be described. For example, when the indentation tester shown in FIG. 9 is used, the softness can be obtained according to the present invention. An actuator 1 is attached to the indentation tester, and a stage 2 is attached to the actuator 1. A load shaft 4 is attached to the stage 2 and the position of the load shaft 4 is controlled by operating the actuator 1 with a personal computer (PC). The load acting on the ball indenter 5 attached to the tip of the load shaft 4 is acquired from the load cell 3 attached to the load shaft 4, and the pushing amount is the amount of movement of the stage 2 to which the load shaft 4 is attached. get.

  As shown in FIG. 10, the indentation test system 17 calculates the Young's modulus from the load value F sent from the load cell 10 of the indentation tester 16 and the indentation amount δ obtained from the potentiometer 9 of the actuator 8. The movement of the indentation tester 16 is also controlled by the indentation position / indentation amount control unit 15. At this time, the indentation reference point and the softness coefficient are calculated in the reference point / coefficient calculation unit 12 from the sent load value F and indentation amount δ, and the calculated indentation reference point and softness coefficient are calculated. Based on the above, the Young's modulus is calculated by the Young's modulus calculator 13. All of the data handled by the CPU unit 11 is recorded in the storage device unit 14.

  Next, a test method for obtaining softness according to the present invention will be described. In the test method, a ball indenter is pushed into the object to be inspected, and the relationship between the push-in amount and the reaction force when pushed in is mathematically processed. As described above, as a test apparatus using this push-in, a device including a mechanism for pushing an indenter into a sample, a part for measuring a reaction force, and a part for calculating (FIG. 10) is used.

  The indenter used for the indentation test is not limited to a sufficiently hard indenter. In addition, as the indenter used for the indentation test, a soft indenter having a known hardness can be employed.

  The indenter used for the indentation test is not limited to the ball indenter. In addition, as the indenter used for the indentation test, a flat end indenter, a cylindrical indenter, or the like can be employed.

  The shape of the sample for measuring the flexibility is not limited to a sample having a flat surface. In addition, a spherical shape, a cylindrical shape, or the like can be adopted as the shape of the sample for measuring the softness.

  The application of the present invention is not limited to measuring the softness of a sample. In addition, as an application of the present invention, evaluation of the internal structure of a sample can be employed. Evaluation of the internal structure of the sample includes foreign substances in the polymer material, foreign substances in food, breast cancer, cirrhosis, and the like.

According to the present invention, the following effects can be obtained.
An indentation test apparatus that measures the softness of a sample can be provided.
The indentation test apparatus according to the present invention can measure and evaluate a wide range of softness of various shapes of soft materials with an objective numerical value called Young's modulus with high accuracy, and is expected to be applied in various fields because of its simplicity. .
Since this effect is based on the invention for obtaining a plurality of numerical data with high accuracy, it can also be used in an indentation test apparatus for measuring the thickness of a sample obtained from the thickness coefficient.
Since this effect is based on the invention for improving the accuracy of the numerical data to be obtained, it can be used in an indentation test apparatus for evaluating the internal structure of the sample.

  It is to be noted that the present invention is not limited to the embodiment for carrying out the above-described invention, and various other configurations can be adopted without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Actuator, 2 ... Stage, 3 ... Load cell, 4 ... Load axis, 5 ... Indenter, 6 ... Sample, 7 ... Table, 8 ... Actuator, 9 ... Potentiometer, 10 ... Load cell , 11 CPU unit, 12 Reference point / coefficient calculation unit, 13 Young's modulus calculation unit, 14 Storage unit, 15 Push position / push amount control unit, 16 Push test machine , 17 ... Indentation test system

Claims (8)

In the indentation test method in which an indenter is pushed into the sample,
Obtaining the indentation load acting on the indenter and the indentation amount of the indenter ;
Based on Hertz's theory of elasticity, the indentation load was expressed as a function of the indentation amount, and the softness coefficient, which was a coefficient, and the reference point of the indentation amount at which the sample and the indenter contacted were obtained as parameters, and obtained in the obtaining step. Calculating the softness coefficient and the reference point by fitting the indentation load and the indentation amount with the function;
Indentation test method, characterized in that it comprises a. In the function, the reference point of the indentation amount and the softness coefficient are expressed by multiplying each by a weighting coefficient ,
2. The indentation test method according to claim 1 , wherein, in the calculating step, the weighting factor is determined based on a reference point of the indentation amount and a magnitude relationship of correction in the repetitive calculation during fitting of the flexibility factor . In the function, the indentation load reference point multiplied by a weighting factor is further included as a parameter,
3. The indentation test method according to claim 2 , wherein in the calculating step, a reference point of the indentation load and a weighting factor thereof are further calculated . In the function, the sample thickness coefficient multiplied by the weight coefficient is further included as a parameter,
3. The indentation test method according to claim 2 , wherein a thickness coefficient of the sample and a weight coefficient thereof are further calculated in the calculating step . In an indentation testing device that pushes an indenter into a sample,
A measuring unit for indentation load acting on the indenter to be indented;
A measurement unit for the indentation amount of the indenter;
Based on the Hertz's theory of elasticity, the indentation load is expressed as a function of the indentation amount. The softness coefficient, which is a coefficient, and the reference point of the indentation amount at which the sample and the indenter contact are used as parameters. A reference point / coefficient calculation unit for calculating the softness coefficient and the reference point by fitting the acquired indentation load and the indentation amount measured by the indentation amount measurement unit with the function ;
An indentation test apparatus, comprising: a Young's modulus calculator that calculates the Young's modulus of the sample using the calculated flexibility coefficient. In the function, the reference point of the indentation amount and the softness coefficient are expressed by multiplying each by a weighting coefficient ,
The indentation test apparatus according to claim 5 , wherein the calculation unit calculates the weighting coefficient based on a magnitude relationship of correction in the repetitive calculation during fitting of the indentation amount reference point and the softness coefficient . In the function, the indentation load reference point multiplied by a weighting factor is further included as a parameter,
The indentation test apparatus according to claim 6 , wherein the calculation unit further calculates a reference point of the indentation load and a weighting factor thereof . In the function, the sample thickness coefficient multiplied by the weight coefficient is further included as a parameter,
The indentation test apparatus according to claim 6 , wherein in the calculating step, a thickness coefficient of the sample and a weighting coefficient thereof are further calculated .

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