JP2010014404A - Indentation type hardness tester - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an indentation type hardness tester accurately performing the detection of the contact origin of a penetrator and a sample in a nanometer order, eliminating the effect on a hardness test by the elastic displacement of the spring for supporting the penetrator and enabling the attachment and detachment of the sample and the on-the-spot observation of the surface of the sample. <P>SOLUTION: The indentation type hardness tester has not only a structure for measuring the load applied to the sample 13 and the indentation displacement of the penetrator 12 using a load detector 14 and a displacement detector 16 while pushing the penetrator 12 into the sample 13 using the elongation of a piezoelectric actuator 11 by fixing the separable penetrator 12 to the piezoelectric actuator 11 and the load detector 14 of a monolithic structure but also a structure forming an electric circuit between the penetrator 12 and the sample 13 and detecting the weak current flowing across the penetrator 12 and the sample 13 by a surface detector 17. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present technology relates to an indentation-type hardness tester in a minute load region (for example, see Non-Patent Document 1). In particular, for a thin film material having a thickness of 1 micrometer or less, an indentation-type hardness is intended to obtain mechanical properties such as hardness and Young's modulus of the thin film material from a load-displacement curve composed of an indenter indentation load and displacement. It relates to the testing machine.

The conventional indentation type hardness tester has a hardness tester that indents the indenter by controlling the electromagnetic force applied to the movable iron core in proportion to the current passed through the solenoid coil (hereinafter referred to as load control type hardness). (For example, refer to Patent Document 1).
Further, there is a hardness tester (hereinafter referred to as a displacement control type hardness tester) that pushes the indenter by controlling the displacement caused by the voltage applied to the piezoelectric actuator fixed to the tester frame (see, for example, Patent Document 2). ).

  Hereinafter, a conventional indentation-type hardness tester will be described with reference to FIGS. FIG. 4 shows an apparatus configuration of a conventional load control type hardness tester. In the figure, reference numeral 41 denotes an indenter, which is supported by a spring mechanism 43 together with a movable iron core 42 fixed on the top thereof.

  When a step-like current signal emitted from the current controller 44 flows through the solenoid coil 45, an electromagnetic force proportional to the current signal is applied downward to the movable iron core 42. This electromagnetic force pushes the indenter 41 into the sample 46 while elastically displacing the spring mechanism 43. The displacement of the indenter 41 is measured by the displacement detector 47 and taken into the load-displacement correlation detector 48 together with the electromagnetic force calculated from the current signal. FIG. 5 is a waveform diagram illustrating the response h of the displacement detector 47 to the step current ΔI flowing through the solenoid coil 45. Reference numeral 49 denotes a triaxial stage, which is used for facilitating the replacement of the sample 46 and the observation of the surface pushing position.

FIG. 6 shows an apparatus configuration of a conventional displacement control type hardness tester. In the figure, 61 is an indenter, which is fixed to a frame 63 together with a piezoelectric actuator 62. When the stepped voltage signal is applied and the piezoelectric actuator 62 extends, the indenter 61 is displaced downward and pushed into the sample 64. The displacement of the indenter 61 is detected by the displacement detector 65, and the load applied to the sample 64 is detected by the load detector 66 and taken into the load-displacement correlation detector 67. FIG. 7 is a waveform diagram illustrating the response P of the load detector with respect to the step voltage ΔV applied to the piezoelectric actuator.
Moriyasu Kanari, Ikuo Ihara, Monthly Tribology, November 2006, pp. 37-39 Japanese Patent Publication No. 6-48236 Japanese Patent Publication No. 2551931

  The problems of the conventional hardness tester described above will be shown in turn. First, there are two problems in the load control type hardness tester. First, it is known that a measurement error called a correction length Δhc increases depending on a decrease in hardness of the sample 46 (for example, Non-Patent Document 1 or Non-Patent Document 2). In particular, in measurement of an organic sample having an indentation hardness HIT of 10 GPa or less, it becomes a fatal measurement error. The main reason why the correction length increases depending on the decrease in the hardness of the sample is the contact origin detection method in the contact between the indenter 41 and the sample surface in the load control type hardness tester. The contact origin detection of the load control type hardness tester is detected by a decrease in the indenter approach speed. In the case of a soft organic material, the indenter is already constant in the sample while the approach speed of the indenter 41 is sufficiently reduced. The amount is pushed in. This undetected indentation displacement of the indenter is referred to as a damage length ΔhD. FIG. 8 shows the relationship between the surface contact position, the surface detection position, and the damage length on the load-displacement curve measured with a load control type hardness tester.

  The second problem of the conventional load control type hardness tester is the influence that the load-displacement characteristic caused by the elastic displacement of the spring mechanism 43 has on the measurement result. When the indenter is pushed in, a force for elastically displacing the spring mechanism 43 is required. The load-displacement characteristic of this spring mechanism is comparable to the load-displacement characteristic of organic materials and the like, and shows the measurement limit of the load control type hardness tester for these materials. FIG. 9 is a load-displacement curve (Non-patent Document 3, mark “◯”) obtained with an organic thin film (copper phthalocyanine) obtained with a conventional displacement-controlled hardness tester. On this curve, the spring load-displacement characteristic of the Roverval mechanism with a spring constant k of 300 N / m is superimposed.

  The problem with the conventional displacement control type hardness tester is that the sample 64 is fixed on the load detector 66. The weight of the sample 64 is limited to be less than or equal to the weight of the load detector, and it is necessary to separate the sample pan 68 from the load detector for attachment / detachment. Further, since it is impossible to combine the moving means of the sample 64 such as a three-axis stage, there is a problem that the sample surface cannot be observed in situ and the pushing position cannot be determined. For the above reasons, the displacement control type hardness tester is hardly used in the industry.

The present invention is intended to solve the problem of such a conventional hardness tester, accurately detecting the contact origin of the indenter and the sample on the order of nanometers, and supporting the indenter. The object is to eliminate the influence of the elastic displacement of the spring on the hardness test, and to enable sample mounting / removal and in-situ observation of the sample surface.
T. Sawa, and K. Tanaka, Journal of Materials Research, 16, pp. 3084-3096 (2001). M. Kanari, H. Kawamata, T. Wakanatsu, and I. Ihara, Applied Physics Letters, 90, 061921 (2007).

  In order to achieve the above object, the present invention provides a load detector in which a separable indenter is fixed to a monolithic piezoelectric actuator and a load detector, and the indenter is pushed into the sample using the extension of the piezoelectric actuator. And a displacement detector to measure the load applied to the sample and the indentation displacement of the indenter.

  The second solution is a structure in which a weak current flowing between the indenter and the sample can be detected by forming an electric circuit between the indenter and the sample.

  The operation of the first solving means is as follows. In other words, since the indenter is driven using the extension of the piezoelectric actuator, the effect of measuring the elastic displacement of the spring mechanism is eliminated. In addition, since the contact origin of the indenter and the sample is detected with a resolution of 1 milligram or less using the load applied to the indenter, the effect of eliminating the damage length ΔhD due to undetected indentation is exhibited. Furthermore, since the sample can be fixed on the stage and moved in the three-axis direction, in-situ observation of the sample surface is possible, the indentation position of the indenter can be determined, and the weight of the sample is not limited, and Demonstrates the effect of easy sample attachment and removal.

  In addition, the action of the second solving means is that an electrical circuit is formed between the indenter and the sample surface, so that in the case of a conductive sample, the contact origin is accurately determined using a weak current signal generated at the time of contact. The effect of being able to be detected is demonstrated.

  As described above, the indentation-type hardness tester of the present invention can accurately detect contact between an indenter and a sample, has no restrictions on the size and weight of the sample, and can perform in-situ observation of the sample surface. Can provide.

  Embodiments of the present invention will be described below with reference to FIGS.

  In FIG. 1, the eleven piezoelectric actuators are integrated with the load detector 14. The twelve indenters are fixed to the tip of the piezoelectric actuator 11 so as to be removable. The sample 13 is detachably fixed on the three-axis stage 18. The displacement detector 16 is fixed to the frame 19, and the displacement detection target 15 is fixed to the indenter 12. The load detector 14 and the displacement detector 16 are connected to the load-displacement correlation detector 10. The surface detector 17 is connected by wiring so as to form an electric circuit between the indenter 12 and the sample 13.

  Hereinafter, the operation of the above configuration will be described first with respect to the load process. The sample 13 is moved to a specified position just below the indenter 12 by the triaxial stage 18 with a positioning accuracy of about 1 micrometer. By fixing the sample 13 on the three-axis stage 18, the weight of the sample 13 is not limited, and in-situ observation of the sample surface using an optical microscope or the like and positioning of the push-in position are possible. With the start of the hardness test, the piezoelectric actuator 11 is applied and extended so that the voltage increases stepwise, and the indenter 11 attached to the tip and the displacement detection target 15 are displaced downward. The displacement of the indenter 12 accompanying the increase in voltage is used by detecting the gap between the displacement detection target 15 and the displacement detector 16. When the indenter 12 comes into contact with the sample 13, it can be detected by a load signal from a load detector 14 that is integrated with the piezoelectric actuator 11. Furthermore, when the sample is a conductor, a weak current flowing between the indenter 12 and the sample 13 at the time of contact can be detected by the surface detector 17 to detect contact. During the hardness test, the load and displacement signal of the indenter 12 detected by the load detector 14 and the displacement detector 16 are taken into the load-displacement correlation detector 10. After the contact between the indenter 12 and the sample 13, the piezoelectric actuator 11 continues to be loaded so that the voltage increases stepwise until the load applied to the sample reaches the specified maximum load. FIG. 2 shows an image of the voltage applied to the piezoelectric actuator 12 and the load detected by the load detector 14 at this time.

  After reaching the maximum load, the piezoelectric actuator 11 is continuously applied with the same voltage for a predetermined period of time, and its elongation is maintained to maintain the load. In the unloading process after holding the load, the hardness test is finished after the load is reduced to the specified minimum load by the reverse operation of the loading process. In addition, when the hardness test is performed at the same location on the sample surface, the above loading process and unloading process are repeated.

  FIG. 3 shows a load-displacement curve obtained when a hardness test is performed on a polyethylene material using the indentation hardness tester invented. In the figure, the white circle (◯) represents the first loading-unloading process, and the black circle (●) represents the load-unloading when the same location on the sample surface is pushed in again. Represents the process. The unloading process at the second indentation traces the unloading process at the first indentation, and the pseudoelastic hysteresis peculiar to the polymer material is obtained between the curves of the second indentation and the unloading process. Therefore, it can be seen that the hardness tester invented performs a reasonable hardness test.

  Conventional indentation hardness testers have been used to evaluate mechanical properties such as hardness and Young's modulus of ceramic materials and metal materials. The indentation hardness tester of the present invention is naturally used for these conventional applications, but it can be expected to develop applications for materials for which it has been difficult to detect the contact origin of the surface.

  As shown in Non-Patent Document 3, in the hardness test of an organic material having a hardness of 10 GPa or less, accurate detection of contact between the indenter and the sample surface is required. In recent years, organic semiconductor films such as EL (Electro Luminessence) displays have been put into practical use and research and development. However, in order to estimate the bending strength of organic semiconductor thin films, the mechanical properties are measured. There is a need to. Since the indentation type hardness tester of the present invention can accurately detect contact on the nanometer order, it can be expected to be used particularly in the field of these organic semiconductor films. Similarly, there is a high possibility that the application can be expanded to evaluate mechanical properties of very soft biological materials such as cells and human tissues. As described above, the indentation hardness tester of the present invention is used as an advanced measurement / analysis instrument in the field of science and technology that is expected to be developed in the future. Is expensive.

The block diagram which shows embodiment of the hardness tester of this invention Waveform diagram showing voltage-load response of the hardness tester of the present invention Load-displacement curve diagram showing an embodiment of the present invention Configuration diagram of a conventional load control hardness tester Waveform diagram showing solenoid current-displacement response of a conventional load-controlled hardness tester Configuration diagram of a conventional displacement control type hardness tester Waveform diagram showing voltage-load response of a conventional displacement control type hardness tester Image of damage length of a conventional load-controlled hardness tester Load-displacement curve diagram by spring mechanism of conventional load control type hardness tester

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Load-displacement correlation detector 11 Piezoelectric actuator 12 Indenter 13 Sample 14 Load detector 15 Displacement detection target 16 Displacement detector 17 Surface detector 18 Triaxial stage 19 Frame

Claims (4)

  An indentation driving piezoelectric actuator and a load detector fixed to the top of a separable indenter, and a displacement detector fixed to a tester frame. Displacement of the indenter is controlled using the piezoelectric actuator, and a sample Measure the amount of displacement of the indenter and the indentation load using the displacement detector and the load detector, and obtain a load-displacement curve consisting of the indenter indentation load and displacement. An indentation type hardness tester characterized by measuring mechanical properties such as hardness and Young's modulus of a sample.   2. The hardness test according to claim 1, wherein the origin of contact when the sample surface and the indenter are in contact is detected with a load resolution of 1 milligram or less using an indentation load signal of a load detector connected to the indenter. Machine.   When the sample is a conductor or semiconductor (hereinafter referred to as a conductor), the contact origin when the sample surface contacts the indenter is detected using a current signal flowing in the electric circuit formed between the sample and the indenter. The hardness tester according to claim 1, wherein:   The sample fixed on the three-axis stage can be moved between a position immediately below the indenter and a surface observation means such as a microscope, thereby enabling in-situ observation of the sample surface and positioning of the indenter pushing position. Hardness tester.

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