JP6818263B2 - Fracture surface analysis device and fracture surface analysis method - Google Patents

Description

The present invention relates to a fracture surface analysis device and a fracture surface analysis method for analyzing a fracture surface of an object to be analyzed when elucidating the cause of fracture of an industrial product or the like.

In the past, when elucidating the cause of fracture of an object to be analyzed such as an industrial product, a skilled person visually judged the fracture surface, but anyone can easily elucidate the cause of fracture without requiring skill. It is desired. Therefore, as disclosed in Patent Document 1 below, the fractal dimension of the fracture surface image at the fractured portion of the material is calculated, and the stress intensity factor range and the mechanical load of the fractured portion are calculated from the calculation result and the characteristic data related to the material. Alternatively, a material fracture surface analyzer for estimating the chemical load has been proposed. In this material fracture surface analysis device, it is possible to estimate what kind of stress was applied and how much from the image data of the fracture surface image of the material.

Japanese Unexamined Patent Publication No. 2000-266613

However, in the case of the fractal dimension, the same value of the fractal dimension may be calculated even if the fracture surface properties are different. Therefore, in the conventional device using the fractal dimension, when the fractal dimension of the fracture surface image is collated with the characteristic data, an erroneous estimation result may be derived. That is, there is a possibility that the fracture surface properties of the material cannot be accurately identified.

The present invention has been made in view of such a problem, and its main purpose is to allow anyone to easily and accurately analyze the fracture surface of the object to be analyzed without requiring skill. The purpose of the present invention is to provide an analysis device and a fracture surface analysis method.

The fracture surface analysis apparatus according to the present invention for achieving the above object has a measuring means for measuring the shading of all or a part of the fracture surface of the object to be analyzed, and the shading measurement position of the fracture surface. A shading difference calculating means for calculating a shading difference between a shading and a shading at another position, a creating means for creating a recurrence plot using the calculation result by the shading difference calculating means, and the recurrence created by the creating means. It is characterized by including a similarity calculation means for calculating the similarity between the lens plot and the reference recurrence plot created based on the shade of the reference fracture surface set in advance by the normalized cross-correlation function.

Further, in the fracture surface analysis apparatus according to the present invention, the measuring means measures the shading of a part of the fracture surface of the object to be analyzed, and a straight line connecting a position with the fracture surface and a position different from the fracture surface. It is characterized by measuring the upper shade.

Further, in the fracture surface analysis apparatus according to the present invention, the straight lines are a plurality of straight lines arranged in parallel with each other, and the recurrence plot is created in each of the straight lines, and the recurrence plot and the recurrence plot are used for each straight line. It is characterized in that the similarity with the reference Recurrence plot is calculated by a normalized cross-correlation function.

According to the fracture surface analysis apparatus according to the present invention, a recurrence plot created by a shading difference calculating means and a creating means based on the shading of the fracture surface of the object to be analyzed, and a preset reference fracture surface. Since the similarity with the reference recurrence plot created based on the shading of is calculated by the similarity calculation means, the fracture surface of the object to be analyzed can be easily analyzed. Recurrence plots are always different for different fracture surface properties. Therefore, by calculating the similarity between the recurrence plot of the fracture surface of the object to be analyzed and the reference recurrence plot, the fracture surface of the object to be analyzed can be accurately analyzed.

Further, according to the fracture surface analysis apparatus according to the present invention, the density on a straight line connecting arbitrary two points on the fracture surface of the object to be analyzed is measured, so that the density can be easily measured.

Further, according to the fracture surface analysis apparatus according to the present invention, the similarity between the recurrence plot and the reference recurrence plot is calculated by the normalized cross-correlation function for each of the plurality of straight lines, so that the fracture surface of the object to be analyzed The analysis can be performed more accurately.

It is a schematic block diagram of one Example of the fracture surface analysis apparatus of this invention. It is a figure which shows an example of the black-and-white image acquired by the imaging means of the fracture surface analysis apparatus of FIG. It is a graph which shows the shading data of a predetermined place of a black-and-white image. It is a figure which shows the state which creates the recurrence plot created by the fracture surface analysis apparatus of FIG. 1, and is the explanatory view which shows the state which the shading data is arranged. It is a figure which shows the state which creates the recurrence plot created by the fracture surface analysis apparatus of FIG. 1, and is the explanatory view which shows the state which a predetermined part is colored from the state of FIG.

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

FIG. 1 is a schematic configuration diagram of an embodiment of the fracture surface analysis apparatus of the present invention. The fracture surface analysis device 1 of this embodiment is an apparatus that analyzes the fracture surface of the object to be analyzed 2 when clarifying the cause of fracture of the object to be analyzed 2 such as an industrial product. The object 2 to be analyzed is not particularly limited, but is, for example, a metal spring. As shown in FIG. 1, the fracture surface analysis device 1 includes an imaging means 3, a measuring means 4, a shading difference calculating means 5, a creating means 6, and a similarity calculating means 7.

The imaging means 3 is a means for imaging the fracture surface of the object to be analyzed 2, and an electron microscope is preferable in this embodiment. This is because it is suitable for imaging a fine pattern of the fracture surface of the object 2 to be analyzed. The imaging means 3 is not limited to the electron microscope, and may be any one capable of acquiring an image of the fracture surface of the object 2 to be analyzed. For example, a camera that captures the object 2 to be analyzed and acquires an image may be used.

The measuring means 4 is a means for measuring the shading of all or a part of the fracture surface of the object to be analyzed. In this embodiment, the measuring means 4 is on a straight line connecting a position where the fracture surface of the object to be analyzed 2 is present and a position different from the fractured surface. Measure the shade of. That is, the shading of a plurality of positions on a straight line is measured. This straight line may be a plurality of straight lines arranged parallel to each other. The measuring means 4 of this embodiment measures the shading of all or part of the image of the fracture surface of the object to be analyzed 2 captured by the imaging means 3, and is an image of the fracture surface of the object to be analyzed 2. The shading on the straight line is measured.

The shading difference calculation means 5 is a means for calculating the shading difference between the shading at that position and the shading at other positions for each of the shading measurement positions of the fracture surface of the object 2 to be analyzed. Specifically, the shading difference between the shading of a certain measurement position and the shading of all other measuring positions is calculated. And this is done for each of all measurement positions. The shading difference calculating means 5 of this embodiment calculates the shading difference for each of the shading measurement positions of the image of the fracture surface of the object 2 to be analyzed imaged by the imaging means 3, and measures on the straight line. The shading difference is calculated for each position. When there are a plurality of these straight lines, the shading difference is calculated for each straight line.

The creating means 6 is a means for creating a recurrence plot using the calculation result by the shading difference calculating means 5. With this creation means 6, a recurrence plot can be drawn using the shade difference, and the characteristics of the data indicating the shade can be visualized. When there are a plurality of straight lines, a recurrence plot is created for each straight line.

The similarity calculation means 7 is a means for calculating the similarity between the recurrence plot created by the creation means 6 and the reference recurrence plot by a normalized cross-correlation function. Here, the reference recurrence plot is created based on the shade of the reference fracture surface set in advance, and is stored in the storage means 8. In this embodiment, the reference recurrence plot is created based on the shading of the image of the reference fracture surface. In the illustrated example, the result calculated by the similarity calculation means 7 is stored in the storage means 9. When there are a plurality of straight lines, the similarity between the recurrence plot created by the creating means 6 and the reference recurrence plot is calculated by the normalized cross-correlation function for each straight line.

Next, a fracture surface analysis method using the fracture surface analysis device 1 of this embodiment will be described. FIG. 2 is a diagram showing an example of a black-and-white image acquired by the imaging means of the fracture surface analysis apparatus of this embodiment, and FIG. 3 is a graph showing shading data of a predetermined portion of the black-and-white image. 4 to 5 are explanatory views showing the creation state of an example of the recurrence plot created by the fracture surface analysis apparatus of this embodiment in chronological order.

In this embodiment, first, the imaging means 3 acquires a black-and-white image 10 of the fracture surface of the object 2 to be analyzed. At this time, a black-and-white image of the entire fracture surface of the object to be analyzed 2 may be acquired, but in this embodiment, a black-and-white image 10 of the fracture surface of the object to be analyzed 2 where the most characteristic appears is acquired. Will be done.

Next, the measuring means 4 measures the shading of all or part of the acquired black-and-white image 10. In this embodiment, in the substantially central portion of the acquired black-and-white image 10 in the vertical direction, the shading on the straight line 11 connecting the left end portion and the right end portion of the black-and-white image 10 is measured. This shading measurement is performed by a conventionally known method.

Numerical data representing the shading read from the black-and-white image 10 of the fracture surface of the object 2 to be analyzed are arranged as (x ₁ , x ₂ , x ₃ , ..., X _N ). Here, in the numerical data, black of the black-and-white image 10 is set to 0, and white is set to 255. The numerical data is the time-series data of the recurrence plot described later, but in the case of this embodiment, it is the shading data at each measurement position of the black-and-white image 10 regardless of the time. FIG. 3 is a graph of shading data, which corresponds to shading measured from a black-and-white image. Using this data, the calculation is performed as shown below, and the result of the calculation is color-coded to form a recurrence plot. In this embodiment, the case where the shading of the measurement positions at 21 points (x ₁ to x ₂₁ ) on the straight line 11 is as follows will be described.

In order to investigate the relationship between these data, the shading difference calculation means 5 is used to determine the shading at that position and the shading at other positions for each of the shading measurement positions of the straight line 11 of the black-and-white image 10. The shade difference is calculated. For this, the Euclidean norm of the shading data | x _i − x _j | is used. Specifically, the difference between the reference value and the other values is calculated with each of x ₁ to x ₂₁ as a reference. The absolute value is used for the difference.

When x ₁ is used as a reference, the value obtained by subtracting two data in order to investigate the relationship between x ₁ and x ₁ , x ₂ and x ₁ , x ₃ and x ₁ , ..., X ₂₁ and x _1. When x ₁ − x ₁ , x ₂ − x ₁ , x ₃ − x ₁ , ..., X ₂₁ − x ₁ are obtained,

And is expressed by the following equation (1).

When referenced to an x _{2, x 1} and _x 2, _{x 2} and _x 2, _{x 3} and _x 2, _..., in order to examine the relationship between _{x 21} and _{x 2,} and subtracting the two data values When x ₁ − x ₂ , x ₂ − x ₂ , x ₃ − x ₂ , ..., X ₂₁ −x ₂ are obtained,

And is expressed by the following equation (2). However, it is an absolute value.

When x ₃ is used as a reference, the value obtained by subtracting two data to examine the relationship between x ₁ and x ₃ , x ₂ and x ₃ , x ₃ and x ₃ , ..., X ₂₁ and x ₃ When x ₁ −x ₃ , x ₂ − x ₃ , x ₃ − x ₃ , ..., X ₂₁ −x ₃ are obtained,

And is expressed by the following equation (3). However, it is an absolute value. In the same manner as these, when the calculation is performed with each of x ₄ to x ₂₁ as a reference, it is expressed by the following equations (4) to (21).

Next, the creation means 6 creates a recurrence plot using the calculation result by the shade difference calculation means 5. The horizontal axis of the recurrence plot is the number of data, that is, the positions of the black-and-white images 10 are drawn side by side from left to right. The vertical axis of the recurrence plot is the number of data, that is, the positions of the black-and-white images 10 are drawn side by side from bottom to top. Therefore, as shown in FIG. 4, the equation (1) is arranged at the lowermost side of the horizontal axis, and the equations (2) to (21) are sequentially arranged on the lowermost side.

Here, as shown in FIG. 5, if it is equal to or more than a preset threshold value, it is colored. In this embodiment, the threshold value is set to 6, and 6 or more parts are colored. In FIG. 5, the colored portion 12 is shown surrounded by a solid line.

This is the recurrence plot to be obtained. As shown in FIG. 5, in the recurrence plot, the upper left portion and the lower right portion are symmetrical with respect to the upward-sloping diagonal line passing through the origin. The values on the diagonal line rising to the right are all the same value (zero in this embodiment).

Then, the similarity calculation means 7 calculates the similarity between the recurrence plot created by the creation means 6 and the preset reference recurrence plot by the normalized cross-correlation function. The reference recurrence plot is created based on the shade of the black-and-white image of the reference fracture surface set in advance, and is created in the same manner as the recurrence plot described above for the fracture surface of the object 2 to be analyzed. The reference fracture surface is a fracture surface of the same material as the object 2 to be analyzed, and in this embodiment, it is a fracture surface showing dimples, river patterns, striations, and grain boundary cracks.

To create a reference recurrence plot, first, the shading on a straight line connecting the left end and the right end of the black and white image is measured at the substantially central portion of the black and white image of the reference fracture surface in the vertical direction. Then, in the same manner as the recurrence plot of the object 2 to be analyzed, the shading difference between the shading at that position and the shading at other positions is calculated for each of the shading measurement positions of the reference fracture surface, and the calculated shading difference is calculated. A reference recurrence plot is created using it. As shown in FIG. 1, the reference recurrence plot is stored in the storage means 8 in advance before the fracture surface of the object to be analyzed 2 is analyzed.

The similarity between the reference recurrence plot and the recurrence plot of the fracture surface of the object 2 to be analyzed is calculated by the normalized cross-correlation function shown in the following equation (22). The closer the calculation result is to 1, the more similar the two are. The similarity calculated in this way is displayed on a display means such as a display, stored in the storage means 9, or printed out in a predetermined format.

Note that T (i, j) represents the time-series data of the fracture surface of the object 2 to be analyzed, and I (i, j) represents the time-series data of the reference fracture surface. Here, the number of black-and-white shading data obtained from the image of the fracture surface of the object 2 to be analyzed is the same as the number of pixels in the image width direction. In this embodiment, the number of pixels in the width direction of the image is unified to 640 pixels. This data becomes T (i, j) in the formula for the normalized cross-correlation function. Further, the number of black-and-white shading data obtained from the image of the reference fracture surface is the same as the number of pixels in the image width direction, and in this embodiment, the number of pixels in the width direction of the image is unified to 640 pixels. There is. This data becomes I (i, j) in the formula for the normalized cross-correlation function. Actually, since the fracture surface of the object 2 to be analyzed and the reference fracture surface each obtain black-and-white shading data on a straight line in the horizontal direction of the image, i of T (i, j) and I (i, j) is With only 1, j changes from 0 to 255.

In the case of this embodiment, the similarity between the recurrence plot of the fracture surface of the object 2 to be analyzed and the recurrence plot of the reference fracture surface is calculated by the normalized cross-correlation function. Therefore, it is possible to automatically identify the fracture surface, which requires appropriate knowledge and experience, and it is possible to easily analyze the fracture surface even if the person is not an expert.

Further, in the case of this embodiment, the recurrence plots corresponding to the fracture surface of the object 2 to be analyzed and the reference fracture surface are compared with each other. In the comparison using the fractal dimension, the same value may be calculated even if the fracture surface properties are different, but in the case of this embodiment using the recurrence plot, such a problem does not occur. Therefore, according to this embodiment, the fracture surface of the object to be analyzed 2 can be accurately analyzed.

Further, in the case of this embodiment, the shading on the straight line 11 connecting the left end portion and the right end portion of the black-and-white image 10 of the fracture surface of the object 2 to be analyzed is measured. Therefore, the shading can be easily measured as compared with the case where all the shading of the image region is measured. As a result, the recurrence plot is created by using a small amount of black-and-white information, so that the processing speed can be increased.

The fracture surface analysis apparatus of the present invention is not limited to the configuration of the above embodiment, and can be appropriately modified. For example, in the above embodiment, the shading of the black-and-white image 10 of the fracture surface of the object 2 to be analyzed is measured by measuring the shading on one straight line, but the shading is not limited to this, and a plurality of straight lines are measured. It may be done by measuring the shading on each straight line of. In this case, a plurality of straight lines, each along the left-right direction of the black-and-white image 10, are arranged in parallel with each other, and a recurrence plot is created for each straight line as described above. Then, the similarity between each of the created plurality of recurrence plots and the above-mentioned reference recurrence plot is calculated by the normalized cross-correlation function, and the fracture surface of the object 2 to be analyzed is identified. Since the similarity is calculated for each straight line in this way, the fracture surface of the object 2 to be analyzed can be identified more accurately.

Further, in the above embodiment, the shading on the straight line 11 along the left-right direction of the black-and-white image 10 was measured, but the shading on the straight line along the vertical direction of the black-and-white image 10 may be measured. Typically, at a substantially central portion in the left-right direction of the black-and-white image 10, the shading on a straight line connecting the upper end portion and the lower end portion of the black-and-white image 10 is measured. In this case, the straight line may be one line or a plurality of straight lines. In the case of a plurality, each is arranged parallel to each other. Further, in the above embodiment, the shading on the straight line 11 which is a part of the black-and-white image 10 of the fracture surface of the object 2 to be analyzed was measured, but the shading of all the black-and-white images 10 may be measured. Further, in the above embodiment, the shading of the black-and-white image 10 of the fracture surface of the object to be analyzed 2 is measured, but the present invention is not limited to this, and the shading may be measured directly from the fracture surface of the object to be analyzed 2. ..

The present invention is suitably applied to an apparatus and method for analyzing a fracture surface of an object to be analyzed such as an industrial product.

1 Fracture surface analysis device 2 Object to be analyzed 4 Measuring means 5 Shading difference calculation means 6 Creation means 7 Similarity calculation means 11 Straight line

Claims (3)

A measuring means for measuring the shading of all or part of the fracture surface of the object to be analyzed,
For each of the shading measurement positions of the fracture surface, a shading difference calculating means for calculating the shading difference between the shading at that position and the shading at another position,
A means for creating a recurrence plot using the calculation result by the above-mentioned shade difference calculation means, and a means for creating a recurrence plot.
A similarity calculation means for calculating the similarity between the recurrence plot created by the creation means and the reference recurrence plot created based on the shade of the reference fracture surface set in advance by the normalized cross-correlation function. A fracture surface analysis device characterized by being provided. The measuring means measures the shading of a part of the fracture surface of the object to be analyzed, and measures the shading on a straight line connecting a position where the fracture surface is present and a position different from the fractured surface. Item 1. The fracture surface analysis apparatus according to Item 1. The straight lines are a plurality of straight lines arranged in parallel with each other.
Create the recurrence plot on each of the straight lines
The fracture surface analysis apparatus according to claim 2, wherein the similarity between the recurrence plot and the reference recurrence plot is calculated by a normalized cross-correlation function for each of the straight lines.

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