JP2008224605A - Measuring method and device of deformation behavior - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly-accurate measuring device for a deformation behavior, capable of acquiring data of a plurality of dislocations or the like by one-time test. <P>SOLUTION: This measuring device of the deformation behavior has characteristics wherein a test is performed by allowing particles P to adhere to the surface of a test piece S, and deformation between adhering specific particles is measured. Hereby, data of the plurality of dislocations or the like are acquired by one-time test in comparison with a method using a strain gage or a method by image analysis using marking by a pen, and the deformation behavior can be measured accurately. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method and apparatus for measuring deformation behavior during, for example, a mechanical test.

  Computer simulation technology using the finite element method has become an indispensable technology in the design and development of structures using various materials. In computer simulation using such a finite element method, it is necessary to input various material properties in order to perform calculations. One such material property is the Poisson's ratio.

  The Poisson's ratio is determined from the ratio of the longitudinal strain generated in the tensile direction of the test piece and the lateral strain generated in the tensile direction and the vertical direction. As a method for measuring strain, there are a method of attaching a strain gauge to a test piece, a method of measuring displacement of each part of the test piece during deformation, and the like. However, in the method using a strain gauge, it is difficult to stick the strain gauge straight in the direction of measuring strain, and there is a problem that the strain gauge is difficult to stick depending on the temperature and material.

  On the other hand, as a method for measuring the displacement by measuring the displacement, there are a method using image analysis, a method using a laser displacement meter, and the like, as in Patent Document 1 or Patent Document 2. In the method of Patent Document 1, markers are attached to a test piece with a pen or the like, and these markers are photographed during a tensile test, and the distance between the markers and the cross-sectional area of the marker portion are measured. In the method of Patent Document 2, the distance between the marked lines and the width of the test piece are measured using a laser displacement meter and a special jig.

The method of Patent Document 1 is effective when measuring strain at a macro level, but is not suitable for measuring strain at a micro level when analyzing a micro deformation. I understood. One reason is that in the conventional method using image analysis, a marker or a marked line drawn with a predetermined paint using a pen or the like has a relatively large width. This is because it becomes difficult to understand and the accuracy of image analysis is reduced. In addition, in such a marking method, when the deformation is increased, the marking is elongated and thinned, and the center is difficult to specify. As a result, the accuracy of the image analysis is lowered.
Further, the method of Patent Document 2 cannot be measured without a laser displacement meter and a special jig, and is not versatile.

Japanese Patent Laid-Open No. 2004-69460 JP-A-5-322556

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a measurement method capable of accurately measuring the deformation behavior of a test piece using a relatively simple means.

    The deformation behavior measuring method according to claim 1 is a method for measuring the deformation behavior of a test piece, in which a test is performed by attaching particles to the surface of the test piece, and a displacement between the attached specific particles is measured. It is characterized by that.

  In the deformation behavior measuring method according to the first aspect, the mark serving as a reference for measuring the displacement is formed of particles. As the particles, those having an appropriate particle diameter prepared from various materials such as metals, ceramics, and resins are adopted. Such particles have industrial uses, and many types of particles including ultrafine diameters are commercially available, and appropriate ones can be adopted from them. As a general material, when an optical detection means is used, a metal that is glossy and easy to image is suitable. Technology for producing fine particles has also been established, and it is possible to employ one having a much smaller size than marking with a pen or the like.

  Since the particles adhering to the test piece are rigid bodies independent of the test piece, even if the test piece is deformed, it is not deformed in conjunction with it. Therefore, there is no problem that it becomes difficult to specify the center because the marking extends and expands or deforms irregularly. Of course, it is also possible to prevent the marking function from being impaired due to thinning or fainting like a paint.

  In order to adhere the particles to the test piece, an appropriate adhesive may be applied to the test piece and the particles may be dropped from above. Such an operation is very simple, and the labor of the operation is greatly reduced as compared with the case where a strain gauge is attached.

The deformation behavior measuring method according to claim 2 is characterized in that, in the invention according to claim 1, particles having a diameter of 500 μm or less are used as the particles.
Accordingly, since the particle diameter is smaller than that of a general pen having a thin pen tip such as an oil-based magic that can be marked on a resin test piece or the like, variation in analysis data is reduced when analyzing the central portion of the marking. For this reason, when performing analysis of minute deformation such as measurement of Poisson's ratio and elastic modulus, errors during image analysis are reduced, and more accurate analysis can be performed.
In addition, because it can be finely marked, it is possible to measure displacement in various directions in a single test, or obtain data such as multiple strains by measuring the displacement between multiple particles in the same direction. it can.
The particles preferably have a particle diameter of 150 μm or less.

The method for measuring deformation behavior according to claim 3 is characterized in that, in the invention according to claim 1 or 2, an adhesive capable of adhering particles to a test piece at high or low temperature is used.
As a result, strain gauges do not have a strain gauge that fully corresponds to the thermal expansion coefficient of resin, etc., so if the temperature changes after attaching the strain gauge, the strain generated on the strain gauge differs from that on the test piece. However, in the method of the present application, there is no problem because the test piece follows the test piece even when the temperature changes after attaching the particles. Moreover, although there exists a problem that a strain gauge tends to peel at the time of a high temperature test, it is hard to peel by the method of this invention. Even if some particles are peeled off, there is no problem because there are many particles. In addition, although there is no restriction | limiting in test temperature, Preferably it is -40-80 degreeC.

The deformation behavior measuring method according to claim 4 is the test according to any one of claims 1 to 3, wherein the test is a tensile test and is obtained based on a measurement result of the particle displacement. The Poisson's ratio is measured from the ratio of the longitudinal strain and lateral strain of the piece.
As a result, the Poisson's ratio can be measured more easily than when a strain gauge is used. In addition, the Poisson's ratio can be measured with higher accuracy than when marking with a pen.

  A simulation method according to a fifth aspect is characterized in that a measurement result of the displacement between the particles measured by the measurement method according to any one of the first to fourth aspects is used. In the simulation method of the present invention, the measurement result (data) of the displacement between particles can be easily obtained in a short time compared to the case where a strain gauge is used, and the time required for the preprocessing stage until the simulation is performed. Can be shortened. Moreover, since the measurement accuracy is higher than the measurement method of marking using a pen, the deformation behavior can be simulated with higher accuracy.

  The deformation behavior measuring apparatus according to claim 6 is obtained by a testing machine that performs a mechanical test on a test piece, an imaging unit that images particles adhering to the surface of the test piece attached to the testing machine, and an imaging unit. It is characterized in that an image of the formed particles is analyzed, a deformation behavior of the test piece in the mechanical test is analyzed, and a displacement between specific particles is measured.

  According to the first to fourth aspects of the invention, the deformation behavior can be accurately measured using a relatively simple means.

Hereinafter, as a preferred embodiment of the present invention, a method for measuring deformation behavior will be described with reference to the drawings.
FIG. 1 shows the configuration of the deformation behavior measuring apparatus according to this embodiment. The test piece S is held by the holding mechanisms 10 and 12 of the tensile tester, and is arranged at a position facing the test piece S. And an analysis device 16 for acquiring an output image of the image pickup device 14 and performing image analysis. A digital camera or the like using a CCD can be suitably used as the imaging device 14, and a computer or the like equipped with image analysis software can be suitably used as the analysis device 16.

  The operation of the deformation behavior measuring apparatus configured as described above will be described. The imaging device 14 images the surface of the test piece S at a predetermined timing during the test, and sends the data to the analysis device 16. The analysis device 16 analyzes the image obtained in time series by the imaging device 14 using image analysis software, follows the movement trajectory of specific particles, and analyzes the momentary displacement. Image analysis may be performed during the test or after the test. If this analysis is performed on two particles, the movement of the two points before and after the tensile test can be seen, which indicates a two-point deformation of the specimen S to which these particles were attached. Therefore, if these two points are taken in the tensile test direction, the longitudinal strain of the material of the test piece S can be calculated, and if taken in the direction orthogonal to the tensile direction, the lateral strain can be calculated.

  The image analysis software determines the position of the center of the image that is approximately circular of the particles on the surface of the test piece S, and specifies the coordinates. In the method of the present invention, even if the test piece S is deformed, the particles are not deformed or thinned. Therefore, the imaging data is always clear, and high accuracy is maintained when specifying coordinates using image analysis software. The If the particle coordinates thus obtained are tracked in time series, the locus of particle displacement can be obtained.

  An example of the method of tracking is as follows. In the initial image, a particle to be noticed (target particle) is selected. For example, if the purpose of the measurement is the Poisson's ratio of the material, two particles that are separated from each other by an appropriate distance are selected. The target particles are selected from among a plurality of particles that are not too close to other particles so that image analysis can be easily performed.

  Next, the image obtained at the subsequent timing is similarly analyzed, and the coordinates of the target particle are measured. By repeating such steps in sequence, it is possible to measure the trajectory of a certain particle.

  In this method, it is basically assumed that the moving distance of one frame of particles is sufficiently small, so it is necessary to set the imaging timing interval to be sufficiently small. Moreover, you may devise when attaching particle | grains to the test piece S surface so that an image analysis may be performed easily. For example, a necessary number of particles may be arranged on the surface of the test piece S. In this way, by performing the tracking operation of the movement of the particles with the computer software, it is possible to save time and effort for a human to perform a complicated operation. Of course, it is also possible for the human to perform the tracking work while visually recognizing the image.

Next, the case where the deformation | transformation behavior of the resin-made tensile test piece S is measured using the apparatus of said embodiment is demonstrated.
First, as shown in FIG. 2A, particles P are adhered to a predetermined region of the test piece S. This can be carried out by first applying or spraying an adhesive on the surface and then dropping particles P such as metal from the top. At this time, it is desirable not to attach an excessive amount of particles so as to facilitate image analysis.

Next, the test piece S is attached to the gripping mechanisms 10 and 12 of the tensile tester, the state is adjusted at the test temperature, and the tensile test is started. During the tensile test, the imaging device 14 performs imaging of the surface to which particles are attached at a predetermined timing. As a result, for example, as shown in FIG. 2 (b), the particles P move with the deformation of the test piece S. The obtained image data is sent to the analysis device 16 and analyzed to track the movement of the focused particle (indicated by a black circle) as shown in FIG. Then, by converting these data into deformation data of the test piece S, the deformation behavior of the test piece S can be measured.
For example, when measuring the Poisson's ratio, the displacement in the tensile direction and the displacement in the direction perpendicular to the tensile direction are measured. From these data, the longitudinal strain in the tensile direction and the lateral strain in the direction perpendicular to the tensile direction are calculated, and the Poisson's ratio is obtained from the ratio.

The deformation behavior and Poisson's ratio were measured when Noblen AZ864E4 manufactured by Sumitomo Chemical Co., Ltd. was used as the material for the tensile test piece S made of resin.
(1) Test equipment tensile testing machine: Shimadzu Hydroshot HITS-T10
Particles: Cu-At 100-200 manufactured by Fukuda Metal Foil Industry Co., Ltd. (particle size 150 μm or less is 85% or more)
Adhesive: 3M spray paste 55 manufactured by Sumitomo 3M Limited
Camera: NIKON Digital SLR Camera D100
Image analysis software: MoveTr2D manufactured by Library Inc.
(2) Test condition test piece S: ASTM D-638-I
Tensile speed: 0.1mm / s
Test temperature: 23 ° C

FIG. 3 shows the relationship between the longitudinal strain generated in the tensile direction of the test piece S and the lateral strain generated in the direction perpendicular to the tensile direction. The Poisson's ratio, which is the ratio of longitudinal strain to lateral strain, was 0.42.

It is a figure which shows the measuring apparatus of the deformation behavior of embodiment of this invention. It is a figure explaining the measuring method of the deformation | transformation behavior of embodiment of this invention, (a) is a test piece, (b) is a state of the particle | grains before and behind a test, (c) is a figure which shows a displacement. . It is a figure which shows the relationship between the longitudinal strain and lateral strain of a resin-made tensile test piece.

Explanation of symbols

S Specimen P Particle

Claims (6)

  A method for measuring the deformation behavior of a test piece, comprising performing a test by attaching particles to the surface of the test piece, and measuring a displacement between the attached specific particles.   The method for measuring deformation behavior according to claim 1, wherein particles having a diameter of 500 μm or less are used as the particles.   The method for measuring deformation behavior according to claim 1 or 2, wherein an adhesive capable of adhering particles to the test piece at high or low temperature is used.   4. The Poisson's ratio according to claim 1, wherein the test is a tensile test, and a Poisson's ratio is measured from a ratio of a longitudinal strain and a lateral strain of a test piece obtained based on a measurement result of the displacement of the particles. The deformation | transformation behavior measuring method in any one.   5. A simulation method using a measurement result of displacement between the particles measured by the deformation behavior measuring method according to claim 1. A testing machine for performing a mechanical test on the test piece;
Imaging means for imaging particles adhering to the surface of the test piece attached to the test machine;
An apparatus for measuring deformation behavior, comprising: analyzing an image of a particle acquired by an imaging unit; analyzing a deformation behavior of a test piece during a mechanical test; and measuring a displacement between specific particles.

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