JPS59204741A - Automatic hardness measuring device - Google Patents

Abstract

PURPOSE:To avoid personal errors and accidental erros and to enhance the number of measurements per unit time to a large extent, by providing a testing machine, which can form an indentation, an image sensor connected to a microscope, a digital image processing part, an indentation-size measuring part, and a hardness operating part, thereby implementing automation. CONSTITUTION:A testing machine 14 is provided with a specified indentor 12 for Vickers hardness, Brinell hardness, or the like. An indentation 13, is formed in the surface of a test piece 10 with a specified load. The image of the indentation 13 is magnified by a microscope 16 and picked up by an image sensor 18. An optical image data 19 of the indentation 13 is converted from analog to digital data by an AD converter part 20 at a gray gradation level (b). A digital image processing part 26 processes and analyzes a digital imge signal 22, locates points P1 and P2 where a gray gradation level curve 26' changes steeoly, and extracts the points as the edge of the indentation 13. A indentation-size measuring part 28 measures the size of the diagonal line of the indentation 13. A hardness operating part 30 divides the compressing load of the indentor 12 by the surface area of the indentation based on the size of the indentation 13 and outpts the result to a printer 31 as a Vickers or Brinell hardness.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic measuring device for hardness, and in particular, for measuring hardness such as Vickers hardness and Brinell hardness, an indentation is formed by pressing the surface of a test piece with an indenter, and the surface area of the indentation is measured by measuring the hardness of the indenter. The present invention relates to a device for automatically measuring hardness, which converts a hardness value from a pressing load.

Vickers hardness and Brinell hardness are often used to determine the mechanical properties of metal 8 materials as they are easily measurable properties. For example, Vickers hardness has a facing angle of 136°.
An indenter made of a square pyramid made of diamond is pressed against the surface of a test piece, and this pressing load is considered to be the value calculated by the surface area of the indentation made by pressing. For this measurement,
It is necessary to perform the work of pressing an indenter against the surface of the test piece under a predetermined load to form an indentation, the work of measuring the size of the indentation, and the work of calculating the hardness based on the measured value and the pressing load.

However, among the three tasks mentioned above, the task of measuring the size of the indentation is carried out by the measurer using a microscope at a magnification of 100 to 4
1ζ An extremely manual process that relies on the human eye by looking at the indentation magnified 00 times, placing the cursor on the diagonal vertices of the roughly square indentation in the field, and measuring the distance between them. Met. For this reason, since there are individual differences in the way the cursor is aligned by the measurer, it is necessary to have the same person measure a series of test pieces to avoid individual errors, which is one of the so-called systematic errors. There was an inconvenience. Even so, it was still difficult to avoid random errors caused by fatigue of the measurer or temporary fluctuations in sensation. In addition, it takes several minutes to measure the value of one melon compared to manually measuring each piece in this way, which is inefficient as it does not allow for a large number of measurements per unit time. There was a point.

The present invention has been made in view of these conventional problems, and provides a device that automates what was conventionally measured manually one by one by human eyes, and eliminates individual errors, Alternatively, the purpose is to eliminate random errors caused by human fatigue or carelessness, and to dramatically increase the number of measurements per unit time.

The present invention provides an automatic hardness measurement device that includes: a testing machine capable of pressing an indenter against the surface of a test piece with a predetermined load to form an indentation; an imaging device connected to a microscope provided in the testing machine; An A/D converter converts the optical image information of the indentation captured by the imager into an analog/digital converter, and a point where the digital image signal from the A/D converter changes rapidly is detected as an indentation. an indentation size measuring unit that measures the size of the indentation from the position of the indentation end obtained by the digital image processing unit; The above object is achieved by comprising: a hardness calculation section that calculates and outputs hardness based on the size and the pressing load of the indenter.

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

In this example, as shown in FIG.
A testing machine 14 capable of forming an indentation 13, an imaging device 18 connected to a microscope 16 provided for the test 114, and optical image information 1 of the indentation 13 imaged on the imaging device 18.
9 to analog/digital conversion at a counter level of 256 gradations, for example, and the A/D converter 20
A digital image processing unit 26 that extracts the point where the digital image signal 22 from the indentation 13 suddenly changes as the edge of the indentation 13, and measures the size of the indentation from the position of the indentation edge obtained by the digital image processing unit 26. The indentation size measurement unit 28 determines fiJ! based on the size of the indentation 13 measured by the indentation size measurement unit 28 and the pressing load of the indenter 12. The hardness calculation unit 30 mainly includes a hardness calculation unit 30 that calculates the hardness and outputs it to a printer 31 or the like.

In addition, in Fig. 1, 11 is an auto stage, 15 is
This is a control unit that controls the image pickup device 18 and the autostage 11.

The testing machine 14 is equipped with an indenter 12 such as Gockers or Brinell, which is determined according to the type of hardness to be determined, and forms an indentation 13 on the surface of the test piece 1o with a predetermined load, The same thing as before can be used.

The above imaging 11118 was taken at a magnification of 100 to 40 times using a microscope 16.
The image of the indentation 13 magnified 0 times is captured two-dimensionally as shown in the photograph in FIG. 2, and an ITV (industrial television camera) or the like can be used.

In addition, Fig. 2 shows that the steel material corroded by nital solution,
An indenter 12 with a load of 10 kg was stamped using a Vickers testing machine 14. This is an original image of the impression 13 taken on a monitor.

The A/D converter 2o converts the optical image information 19 of the impression 13 captured by the image pickup device 18 into analog/digital data at a rebuttal level.
Convert to digital. Here, the "rebuttal level" refers to the gray brightness from black to white at each pixel, which is converted into a numerical value in minute steps and converted into an absolute value. Specifically, this legal system level is preferably divided equally into 64 or more gradations, preferably about 256 gradations, from black to white. This occurs when the matrix structure is exposed by etching, or when there are scratches or corroded areas.
This is done in consideration of correctly identifying 3 and 3. In the past, the measurer could accurately identify these items with his or her own eyes, but this is necessary when automation is used. That is, if we simply set the brightness and darkness thresholds directly on the optical image information 19 of the IC indentation 13 projected on the imager 18, binarize it, and then extract the bright (or dark) indentation part, There is no problem with a test piece with low noise such as a standard sample, but as shown in Fig. 2, if there is a part of the matrix structure-vJ scratch or corrosion area that is as bright as the indentation 13, as shown in Fig. 3. As shown in FIG. This causes an error in the measurement, and in some cases, as in the case of the upper vertex of the indentation 13 in Figure 3, it may not be closed and the measurement may not be too high. .

Therefore, in the present invention, in order to prevent this, the digital image is converted from analog to digital at the legal level and the brightness of each pixel e is replaced with a numerical value.
3゜The digital image processing unit 26 converts the digital image signal 22 into an analog/digital converted FA at the legal system level.
Process and analyze the points P1 and P2 where the resulting legal level curve 26' changes rapidly, as shown in Figure 4.
l! Search along IA and extract the edge of the indentation 13. FIG. 4(B') is a schematic trace of FIG. 4(A), in which the vertical axis of the diagram represents the legal system level and the horizontal axis represents the position. In addition, at this time, elements other than the end of the indentation 13,
For example, noise caused by Q-trix tissues or wounds can cause
It is desirable to eliminate this as much as possible by approximating the end of the impression 13 to a straight line. Specifically, "changed rapidly."
In order to make this identification more reliable, for example, find the envelope that touches the curve of the part of the legal level curve 26'' that includes the inflection point, and apply the same curve 26' to a 1-bus filter. (Conceivable methods include cutting the high-frequency noise component with a filter, or finding the average rate of change within a certain section of the curve 26' and smoothing the noise component as a result.In this case,
Taking it one step further, for example, the average rate of change between b units along measurement axis A is 10 or more, and the average rate of change between the same <20 units is 8 or more. It would be even better if the noise could be removed most efficiently depending on the nature of the test, such as by making a judgment such as 4. Figure 5 shows that J
Extract U P1 and P2 and show how they are connected.

The indentation size measuring section 28 measures the size of the indentation, for example, the size of its diagonal line, from the position of the end of the indentation 13 as shown in FIG. 6, thus determined.

The hardness sieve part 30 divides the pressing load of the indenter 12 by the surface area of the indentation based on the determined size of the indentation 13.
The hardness is outputted to a printer 31 or the like as Vickers or Brinell hardness. The Vickers hardness of 1-1v when the size of the diagonal line is measured in this way can be obtained by the following formula, where the pressing load is P1, the surface area of the indentation is S, and the length of the diagonal line of the indentation is put.

Nv=P/5 =2Psin68°/β2 =1.854P/J221kg/mm2] However, in the present invention, C is 1llil constant + 1'llll A in order when measuring the I is of the indentation 13. It is possible to directly determine the surface area S by moving from the top to the bottom and integrating from the position of the entire end of the indentation 13. By doing this, the surface area S, which conventionally had to be estimated by calculation from the size of the diagonal, can be actually measured, and a more reliable hardness can be obtained.

It should be noted that the Vickers hardness of tempered steel having a strength of approximately 60 kg/- was measured 20 times using the device according to the present invention under conditions of m 10 kg r/'vj before pressing, which is the same as the Vickers hardness measured using the conventional method. A graph comparing the Vickers hardness measured 20 times is shown in Fig. 7. As shown in the figure, high reliability with little variation was observed.

As explained above, according to this explanation, it is now possible to automate what was conventionally done by relying on the human's mouth and measuring by moving the cursor one by one. In addition to reducing stress and stress, it is also possible to dramatically increase the number of measurements per hour.
This makes it possible to eliminate personal errors caused by improper cursor movement, accidental errors caused by fatigue, or carelessness. Furthermore, the optical image information of the indentation imaged by the '&1 image machine must be processed at the legal level. This has the advantage that the discrimination between noise elements such as matrix tissue and scars that have been present and the edges of the impression can be made without errors and accurate Sclerosis values can be obtained.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of the present invention; a block diagram partially including a schematic front view of the apparatus, FIGS. 2 to 4 (A>, and FIGS. 5 and 6). is a photograph showing the metallographic structure of the test piece (
Figure 2 is an image of the indentation when an indenter with a load of 10 kg was pressed on a corroded steel specimen using a Pinkers tester. Figure 4 (A) shows the normal level of the indentation and test piece after 1 bit of the binarization process. The schematic trace diagram, Figure 2, extracts the Q part to be measured by gray level processing,
Figure 6 is an overall view of the extracted indentation, and Figure 7 is a comparison of the variation in hardness measured using the device according to the present invention with that of the conventional method. There is a hole diagram. 10... Test piece, 12... Indenter, 13
...Indentation, 14...Testing machine, 16.
...Microscope, 18...Image machine, one...
・Light'i-image information, 20...A/D Himobe, 2
2...Digital i! iii self-issue number, 26...digital image processing section, 28...indentation size measuring section, 3o...hard 1 sad bean section. Agent Takaya Theory (1 idiot) Figure 1 16 18 Figure 2 Figure 3 Figure 4 (A) Figure 4 (B) 8 Figure 5 Figure 6

Claims (1)

[Claims] (1) A testing machine capable of pressing an indenter onto the surface of a test piece with a predetermined load to form an indentation; an imaging machine connected to a microscope equipped with the testing machine;
An A/D converter converts the 1-hour optical image of the impression produced by the imager into an analog/digital converter, and the digital image signal from the A/D converter rapidly changes. a digital image processing section that extracts the end of the indentation; an indentation size measuring section that measures the size of the indentation from the position of the end of the indentation obtained by the digital image processing section; An automatic or dynamic hardness measuring device comprising: a hardness calculation unit that calculates and outputs hardness based on the size of the measured indentation and the pressing load of the indenter;