JP2009085732A - Friction material analyzing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique which enables the more accurate analysis of the constitution of a friction material in a friction material analyzing method. <P>SOLUTION: The friction material analyzing method has the acquiring step for acquiring the constitution data related to the constituent element of the friction material, which contains the material constituting the friction material and the gas present in the friction material, by passing the radiation light as the electromagnetic wave, which is generated when electrons are bent by a magnetic field, through a sample including the friction material and the output step for visually expressing the constituent element of the friction material on the basis of the constitution data acquired in the acquiring step. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a friction material analysis method.

As a technique for analyzing a material constituting a solid sample and voids contained in the material, a mercury intrusion method and a surface structure analysis method are known. In the mercury intrusion method, mercury is injected into the voids of the sample, and the voids of the solid sample are measured based on the pressure during the injection and the volume of the injected mercury. The surface structure analysis method analyzes reflected electrons, characteristic X-rays, and the like generated by irradiating the surface of a solid sample with a finely focused electron beam or X-ray (see, for example, Patent Document 1).
JP 2002-116159 A

  Friction materials are used for brakes and clutches of automobiles and industrial machines. The friction material plays an important role, for example, as an important safety part in automobiles. In recent years, in addition to frictional and vibrational characteristics that have been regarded as important in recent years, safety materials, responses to environmental problems, and responses to international standardization are being demanded. In order to meet such a demand, it is desired to establish a technique for accurately analyzing the components of the friction material. However, the friction material is composed of a very large number of materials, and further has a feature that a plurality of fine air holes (voids) are formed between the materials. As a result, it has been difficult to accurately analyze the friction material with the conventional analysis technique.

  For example, a mercury intrusion method and a surface structure analysis method are known as conventional techniques for analyzing voids existing in a solid sample. According to the mercury intrusion method, the amount of voids existing in the solid sample and the size of each void can be analyzed based on the pressure when the mercury is intruded into the voids and the volume of the mercury that is injected. However, according to such a method, it is only possible to analyze what percentage of the total volume of voids having a size of about several μm or more. That is, in the mercury intrusion method, it is not possible to obtain information on how the voids are three-dimensionally shaped and how the voids are distributed. Furthermore, in the mercury intrusion method, since mercury is injected from the outside of the solid sample, it is impossible to measure a closed gap that is not connected to the outside.

In addition, according to the surface structure analysis method, material components contained in a solid sample are analyzed by analyzing reflected electrons, characteristic X-rays, etc. generated by irradiating the surface of the solid sample with a finely focused electron beam or X-ray And its distribution can be specified. However, in the case of three-dimensional analysis of the components of the solid sample by the surface structure analysis method, the measurement is destructive, such as slicing the solid sample thinly. In addition, there is a limit to slicing a solid sample thinly, and there is a problem that the shape and distribution of the material are destroyed when thinly processing and accurate analysis cannot be performed.

Furthermore, CT (Computed Tomography) technology using X-rays is known. However, as described above, the friction material is composed of a large number of materials and has a plurality of fine voids between the materials, so in the conventional CT technology, details of the material and the state of the voids in the friction material are provided. Could not be identified.

  The present invention has been made in view of the above problems, and relates to a method for analyzing a friction material, and an object thereof is to provide a technique capable of analyzing the configuration of the friction material more accurately.

  In the present invention, the configuration of the friction material is visually reflected by allowing the emitted light as an electromagnetic wave generated when electrons are bent by a magnetic field to pass through the inside of the sample made of the friction material.

  More specifically, the present invention is a method for analyzing a friction material, in which radiated light as an electromagnetic wave generated when electrons are bent by a magnetic field is passed through a sample made of the friction material, Based on the configuration information acquired in the acquisition step, the acquisition step of acquiring the configuration information regarding the components of the friction material including the material constituting the friction material and the voids present in the friction material, And an output step for visually displaying the components of the friction material.

  According to the present invention, the resolution when visualizing the component is improved by passing the radiated light as the electromagnetic wave generated when the electrons are bent by the magnetic field through the sample made of the friction material. As a result, the configuration of the friction material can be analyzed in more detail than before. In addition, according to the present invention, since the sample can be analyzed without destroying the sample, a more accurate configuration of the friction material can be confirmed.

  In the acquisition step, information regarding the constituent elements of the friction material is acquired. More specifically, the configuration information is acquired by allowing the emitted light to pass through the inside of a sample made of a friction material. Synchrotron radiation means electromagnetic waves generated when high-energy electrons are bent by a magnetic field. The radiated light includes various wavelength regions from X-rays to infrared rays. In the present invention, it is preferable to use radiated light composed of short-wavelength X-rays. The configuration information refers to information about components including the type and size of the material constituting the friction material, and the size and position of the voids present in the friction material.

By using electromagnetic waves with high electron energy and short wavelength as synchrotron radiation, it is composed of a very large number of materials, and has a feature that fine voids are formed between the materials. The resolution in the analysis of the material can be increased. In addition, such irradiation of radiant light can be performed in an existing radiant light experiment facility. Examples of the existing synchrotron radiation experiment facility include Spring-8 (Super Photon ring-8) in Japan and APS (Advanced Photon Source) and ESRF (European Synchrotron Radiation Facility) in overseas.

  In the output step, the constituent elements of the friction material are visually displayed based on the configuration information. The visual projection means that the configuration of the friction material is projected two-dimensionally or three-dimensionally through a display device such as a display. According to the present invention, by using synchrotron radiation, it is possible to obtain more detailed information about the constituent elements of the friction material, and by visually projecting based on such detailed information, the configuration of the friction material It becomes possible to grasp the element more accurately.

  Here, in the present invention, in the output step, based on the configuration information acquired in the acquisition step, a two-dimensional image generation step that generates a two-dimensional image and a two-dimensional image generated in the two-dimensional image generation step A component of the friction material may be visually displayed by executing a three-dimensional image generation step of generating a three-dimensional image based on the image.

  By finally generating a three-dimensional image based on the configuration information acquired in the acquisition step, the friction material can be captured three-dimensionally. Note that generation of a two-dimensional image and generation of a three-dimensional image can be performed by an existing program. For example, as a program for generating a CT (Computed Tomography) image based on the configuration information acquired in the acquisition step, a program using the Filtered Back Projection method is exemplified.

  According to the present invention, it is possible to clarify the three-dimensional structure of components including voids in a friction material, the details of which have been unknown, and the correlation distribution between materials. This also makes it possible to elucidate the particle size and shape of the material contained in the molding pad that has not been clearly elucidated so far. Furthermore, it is possible to elucidate the relationship of influential factors in the manufacturing process of the friction material such as firing at the time of thermosetting the binder resin. As a result, it is possible to control the three-dimensional distribution of components including voids in the friction material, and it is also possible to control the friction performance by enabling control of the three-dimensional distribution.

  Further, in the conventional CT technique, a great deal of time is spent on analyzing the sample. However, according to the present invention, it is possible to greatly reduce the analysis time. As a result, the number of steps in the development process of the friction material can be greatly reduced, and the manufacturing cost of the friction material can be reduced.

  The present invention further includes an extraction step of analyzing the three-dimensional image generated in the three-dimensional generation step, extracting predetermined constituent elements constituting the friction material, and visually displaying the extracted constituent elements. It is good also as a structure.

  As described above, the friction material is formed of a component including many materials and fine voids formed between the materials. Therefore, there is a possibility that, for example, the particle diameter of each material, the arrangement position and the size of the gap, and the like cannot be sufficiently grasped only by projecting the friction material three-dimensionally. Therefore, in the present invention, by extracting predetermined constituent elements from the constituent elements constituting the friction material and visually projecting the extracted constituent elements, it is possible to more clearly confirm the particle size of the material, the arrangement position of the voids, and the like. I did it.

  The component can be extracted by extracting the linear absorption coefficient μ of the component corresponding to the material or void to be extracted. The shading of each pixel of the three-dimensional image corresponds to this linear absorption coefficient μ. The shading of each pixel corresponds to the component of the friction material. That is, the constituent elements of the friction material correspond to the linear absorption coefficient μ. Therefore, for example, by extracting only the pixel values corresponding to the gaps and visually displaying them, it is possible to three-dimensionally check how the gaps exist inside the friction material.

  The present invention may be a device or a program that realizes any of the functions described above. Furthermore, the present invention may be a computer-readable recording medium that records such a program.

  ADVANTAGE OF THE INVENTION According to this invention, the technique which can analyze the structure of a friction material more correctly can be provided regarding the analysis method of a friction material.

  Next, an embodiment of the method for analyzing a friction material according to the present invention will be described with reference to the drawings, taking actual experiments as an example.

<Analysis flow>
FIG. 1 shows a flow of a friction material analysis method according to the first embodiment. In step S01, the friction material is primarily processed into a predetermined size. Specifically, the friction material is cut into a 3 × 3 × 10 mm rectangular parallelepiped sample. Next, in step S02, the cut sample is subjected to fine processing. That is, the sample cut into a rectangular parallelepiped is processed into, for example, a cylindrical sample of φ0.6 × 10 mm. When the processing of the sample is completed, the process proceeds to step S03. However, the size of the sample is determined by the wavelength of the emitted light and the linear absorption coefficient of the component, and is not limited to this.

  In step S03, the sample is irradiated with radiated light. Next, in step S04, radiated light that passes through the sample is detected. The process of irradiating the emitted light in step S03 and the process of detecting the transmitted radiation in step S04 correspond to the obtaining step of the present invention. That is, the configuration information relating to the constituent elements of the sample (friction material) is acquired by detecting the transmitted radiation that is emitted and transmitted.

(Experimental facility)
In Example 1, SR (Synchrotron Radiation synchrotron radiation) was used for the analysis of the friction material. SR facilities in the hard X-ray wavelength region that can be used publicly in Japan include PF (Photon Factory: High Energy Accelerator Organization, Institute for Materials Structure Chemistry Synchrotron Radiation Experimental Facility), and Spring-8 (Super Photon ring-8: The official name is Japan Synchrotron Radiation Research Institute. In Example 1, Spring-8 capable of irradiating radiation having sufficient X-ray intensity was used.

  In Example 1, Spring-8 was used, but is not limited to this. Overseas, several so-called third generation synchrotron radiation experimental facilities with the same performance as Spring-8 are known. Here, FIG. 2 shows the performance comparison of the overseas third generation synchrotron radiation experiment facility. APS (Advanced Photon Source) and ESRF (European Synchrotron Radiation Facility) shown in FIG. 2 have the same functions as Spring-8. Therefore, these facilities may be used instead of Spring-8.

In Spring-8 used in Example 1, BL20B2 and BL47XU exist as beam lines capable of performing CT measurement. In Example 1, BL47XU was used. The performance of the beamline BL47XU is as follows. That is, in BL47XU, the light source is a vacuum sealed undulator (magnetic field cycle length: 32 mm, cycle number: 140 Hz, magnetic pole interval: 9.6 mm to 50 mm variable), fundamental energy region (5.9 to 18.9 keV). , The spectrometer is a double crystal spectrometer (Bragg angle movable range: 3 to 22 degrees), and the available X-ray energy is 5.2 to 37.7 keV (S
i111 crystal plane use).

  The characteristics of the X-ray (radiated light) at the sample position of the experimental hatch (exp hutch2) for micro CT in the beam line (BL47XU) used in Example 1 are as shown in FIG.

(Experimental device)
Next, the experimental apparatus (measuring apparatus for micro CT) used in Example 1 will be described in more detail. The measurement apparatus for micro CT (hereinafter simply referred to as CT apparatus) used in Example 1 is permanently installed in BL47XU in the facility Spring-8 used in Example 1. The CT apparatus used in Example 1 has a spatial resolution of about 1 μm, and includes a control unit having a light source, a spectroscope, a sample stage, a detector, a CPU, and a storage unit, and a display unit that displays measurement results and analysis results. Has been. The rotation accuracy of the rotating shaft of the sample stage is 0.2 μm or less. As the detector, a visible light changing type two-dimensional detector is used, and the spatial resolution of the single crystal phosphor is about 1 μm. The CT apparatus can also measure metals, rocks, polymers, etc. in addition to friction materials. The measurement time of the CT apparatus is about 30 minutes when measuring the sample. The storage unit provided in the CT apparatus can store measurement data, but the capacity of this storage unit is about 5 GB.

(Measurement condition)
Here, the details of the experimental conditions performed by the CT apparatus described above will be described. The sample used was a commercially available brake pad A and a commercially available brake pad B. These samples are processed into a cylindrical shape having a predetermined size by executing the above-described steps S01 and S02. The incident energy was 20 keV, and the undulator pole spacing, that is, the spacing between the magnets arranged to generate the emitted light was 10.56 mm. The detector was BM3 (× 20) + C4880-41S, the number of pixels was 2000 × 1312, and the pixel size was 0.47 μm / pixel. The number of projections was 1500. The distance between the sample and the detector was about 15 mm, and the exposure time was 300 msec. The total scan time required about 35 minutes.

When the detection of the radiated light passing through the sample is completed in step S04, an image is generated based on the detected data in step S05 (corresponding to the output step of the present invention). In the first embodiment, an img format image is generated based on measurement data measured by the detector of the CT apparatus. Next, a CT image conversion program converts the TIFF format CT image from the img format image. In Example 1, a program (program name: ct_manual.lzh) for converting an img image obtained by Spring-8 into a CT image was used. This program can be obtained from the URL http://www-bl20.spring8.or.jp/xct/index.html. This program uses the Filtered Back Projection method that is often used in CT experiments. Various techniques are known as a technique for generating a two-dimensional image based on the radiated light transmitted through the sample and a technique for generating a three-dimensional image based on the generated two-dimensional image. Therefore, the procedure for generating a CT image is not limited to the above. A CT image can be generated by appropriately applying an existing image generation technique.

  Here, FIG. 4 shows an example of the generated CT image. 4A is a CT image of pad A, and FIG. 4B is a CT image of pad B. The shading of each pixel corresponds to the linear absorption coefficient μ of the component, and the linear absorption coefficient μ corresponds to each component constituting the sample, that is, the density of the material and the contained element. That is, the linear absorption coefficient μ can be evaluated by the product of the mass absorption coefficient μ / ρ and the mass density ρ determined by the element and composition contained in each material. Therefore, by specifying the linear absorption coefficient for each material in advance, it is possible to specify the material and void corresponding to each pixel value.

4A and 4B is set in proportion to the value of the linear absorption coefficient μ. That is, the black and white gradation is set so that the larger the value of the linear absorption coefficient μ is, the more white the color is, and the smaller the value of the linear absorption coefficient μ is, the black the color is displayed. The black and white gradation can be determined according to the purpose of analysis and the size and type of the material contained in the sample. In Example 1, FIG. 4A is set to ⁸ bits (2 ⁸ = 256), and FIG.
Is set to ¹⁶ bits (2 ¹⁶ = 65536).

  Based on the above, when comparing the CT image of FIG. 4A with the CT image of FIG. 4B, the pad A shown in FIG. 4A has a larger particle size of the material constituting the friction material than the pad B shown in FIG. 4B. I can confirm that. When attention is paid to the particle diameter of the material constituting the friction material, the pad A shown in FIG. 4A is made of a material having a relatively isotropic particle shape, whereas the pad B shown in FIG. It can be seen that it is made of a relatively anisotropic material, in other words, a fibrous material. Further, when attention is paid to the voids included in the sample, it can be confirmed that voids exist in the region X shown in FIG. 4A, for example. Comparing the pad A shown in FIG. 4A with the pad B shown in FIG. 4B, it was confirmed that the voids included in the pad A had a higher void ratio and each void was larger.

According to the friction material analysis method of Example 1 described above, a CT image is generated based on the measurement data obtained as a result of irradiating predetermined radiation by the CT apparatus installed in Spring-8. By doing so, it is possible to identify in detail the material in the friction material and the state of the air gap, which has been difficult with the conventional CT technique. That is, the particle size and shape of the material contained in the molding pad, which has not been clearly clarified so far, can be clarified. Furthermore, it is possible to elucidate the relationship of influential factors in the manufacturing process of the friction material such as firing at the time of thermosetting the binder resin. As a result, it is possible to control the three-dimensional distribution of components including voids in the friction material, and it is also possible to control the friction performance by enabling control of the three-dimensional distribution. In addition, according to the method for analyzing a friction material of Example 1, it is possible to significantly reduce the analysis time. As a result, the number of steps in the development process of the friction material can be greatly reduced, and the manufacturing cost of the friction material can be reduced.

  Next, a method for analyzing the friction material of Example 2 will be described. FIG. 5 shows a flow of a friction material analysis method according to the second embodiment. First, the steps from Step S01 to Step S05 are executed in the same manner as in the method for analyzing the friction material of Example 1. Next, in step S06, the CT image generated in step S05 is analyzed.

  That is, in Example 1, the CT image of the sample made of the friction material was generated by executing the processing from Step S01 to Step S05. The generated CT images were confirmed to be different from each other by comparing two types of samples, such as pad A and pad B, for example. In contrast, the friction material analysis method according to the second embodiment analyzes the CT image generated in step S05 in more detail.

The detailed analysis of the CT image is performed by, for example, coordinates corresponding to the pixel values of the gaps formed between the materials constituting the friction material or between the friction materials, the pixel values of the region, or their statistical values (average values). Or deviation value) and the like. Such an analysis can be performed by an existing CT image analysis program. In Example 2, the image analysis program (program name: ImageJ) was used. The image analysis program (program name: ImageJ) is a URL
It can be obtained from http://rsb.info.nih.gov/ij/.

  Here, FIG. 6 shows an example of analysis by an analysis program (program name: ImageJ). FIG. 6 shows a histogram of pixel values of the region X in FIG. 4A. Thus, according to the analysis program (program name: ImageJ), for example, a histogram of pixel values in a predetermined area can be displayed. FIG. 7 shows the linear absorption coefficient μ of the material constituting the pad B. As shown in the figure, the pad B is composed of a plurality of materials such as a metal fiber 1, a metal powder 1, and an abrasive 1, and a linear absorption coefficient μ is set for each material. Therefore, it is possible to specify the material in the CT image by calculating the linear absorption coefficient μ for each material in advance and making this correspond to the pixel value in the CT image.

  Further, by creating a relative histogram of the CT image, it is possible to grasp the approximate value of the composition. Here, FIG. 8 shows the appearance frequency of the pixel values of the CT images of the pads A and B. In FIG. 8, the appearance frequency of the pad A is indicated by ◯. On the other hand, the appearance frequency of the pad B is indicated by □. In the example shown in FIG. 8, for pad B, a value obtained by changing 16 bits data to 8 bits data is used.

  Here, in the CT image analysis performed in step S06, a predetermined material constituting the sample may be extracted and displayed. Such processing corresponds to the extraction step of the present invention. Specifically, for example, specific materials, voids, and the like are extracted by performing binarization processing on the CT image obtained in step S05.

Such binarization processing can be performed by various existing programs. In the embodiment, a program (program name: Slice) was used. The program (program name: Slice) can be acquired by the URL http://www-bl20.spring8.or.jp/slice/. FIG. 9 shows an example in which the air gap distribution is analyzed by a program (program name: Slice). FIG. 9 shows only a portion of pixel values in a certain range extracted from the CT image of the pad A shown in FIG. 4A. Comparing FIG. 4A and FIG. 9, it can be confirmed that the portion where the pixel value is small in FIG. 4A is displayed. That is, it can be seen that a portion with a small pixel value is a gap.

  In the embodiment, the voids are extracted, but the particle diameter, distribution, etc. of the material constituting the friction material can be confirmed by the same procedure. By analyzing not only voids but also all materials, statistics such as the three-dimensional abundance, particle size distribution, and uniformity of components that make up friction materials, which were previously considered difficult, are quantified. Can be obtained. And based on these results, it is also possible to obtain such a statistical correlation between materials.

  The preferred embodiments of the present invention have been described above, but the friction material analysis method of the present invention is not limited to these, and can include combinations of these as much as possible. In this embodiment, CT images were generated and analyzed using an experimental device in the synchrotron radiation experimental facility. That is, CT images were generated and analyzed by causing the computer of the experimental apparatus to execute the predetermined program described above. However, the method of generating and analyzing the CT image is not limited to this. Measurement data obtained by the experimental apparatus may be stored in a portable recording medium or the like, and a CT image may be generated by causing a computer different from the experimental apparatus to execute the predetermined program. The computer may include a CPU, a memory, and a display as long as it can execute the predetermined program.

The flow of the analysis method of the friction material of Example 1 is shown. The performance comparison of the overseas third generation synchrotron radiation experiment facility is shown. The characteristic of the X-ray (radiation light) in the sample position of the experimental hatch (exp hutch2) for micro CT in BL47XU is shown. A CT image of pad A is shown. A CT image of pad B is shown. The flow of the analysis method of the friction material of Example 2 is shown. An example of analysis by an analysis program (program name: ImageJ) is shown. The linear absorption coefficient μ of the material constituting the pad B is shown. The frequency of appearance of pixel values of the CT images of pad A and pad B is shown. An example of analyzing the distribution of voids by a program (program name: Slice) is shown.

Explanation of symbols

X ... area

Claims (3)

A friction material analysis method,
By passing radiated light as an electromagnetic wave generated when electrons are bent in a magnetic field through a sample made of the friction material, a material constituting the friction material and a gap existing in the friction material, An acquisition step of acquiring configuration information relating to a component of the friction material including:
Based on the configuration information acquired in the acquisition step, an output step for visually copying the components of the friction material;
A method for analyzing a friction material. In the output step,
A two-dimensional image generation step of generating a two-dimensional image based on the configuration information acquired in the acquisition step;
The three-dimensional image generation step of generating a three-dimensional image based on the two-dimensional image generated in the two-dimensional image generation step is executed to visually project the components of the friction material. The analysis method of the friction material as described in 2.   3. The method according to claim 2, further comprising an extraction step of analyzing the three-dimensional image generated in the three-dimensional generation step, extracting a predetermined component constituting the friction material, and visually displaying the extracted component. Analysis method of friction material.

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