JPH049467B2 - - Google Patents

Description

Detailed Description of the Invention A. Field of Industrial Application The present invention is an apparatus for measuring anisotropy such as the degree of fiber orientation of various materials such as sheets, plates, rods, blocks, etc. using high frequencies. Regarding.

Machine-made paper naturally has fibers that are oriented to some extent due to its manufacturing method. Instead of materials made of these single substances, composite materials made of fibers and substrates, such as plastics reinforced by mixing carbon fiber, are intentionally aligned in the direction of the fibers to increase tensile strength. There is. In this way, many materials have their component fibers or molecules aligned to some degree, either naturally or intentionally.
It is necessary to maintain a constant degree of orientation of the fibers in order to obtain uniformity of the product. Therefore, there is a high need for an apparatus that can inspect materials and quickly measure fiber orientation during the manufacturing process.

B. Prior art A method that has been used for a long time to measure orientation is to mechanically cut out strip-shaped test pieces in various directions from a sheet-like material to be tested, measure their tensile strength, and then cut out the test pieces. When the relationship between the direction and the tensile strength is expressed in polar coordinates, an elliptical or cocoon-shaped figure is obtained, and the degree of orientation is measured from the ratio of the major axis to the minor axis. This method is a destructive test and is very time consuming, so it can only be applied to sampling inspections of final products, and is only suitable for measuring semi-finished products in the middle of the process and feeding back the results to earlier processes. was not suitable. For this reason, a method using infrared polarization dichroism has been proposed for molecular orientation, but this method requires that the sample be not very thick and fairly transparent to the infrared light used. Yes, applicable materials are limited.
A method using microwave radio waves instead of infrared light was proposed as a method that could be applied to a wider range (Japanese Patent Laid-Open No. 59-224547). This method can also measure fiber orientation in fiber-containing materials.

The method proposed above utilizes the fact that the absorption of radio waves by a sample changes depending on the electric field method of the radio waves and the orientation method of molecules or fibers. Rather than measuring the sample itself, a sample is placed inside the cavity resonator, and changes in the Q value or resonance frequency of the cavity resonator depending on the orientation of the sample are measured. In this case, it is necessary to leave a gap in the cavity resonator to allow the sample to enter and exit, and since it is better for the resonator to have a higher Q value, the gap cannot be made too wide. For this reason, it is difficult to move the sample in and out, making it unsuitable for measurements during the process, and the mechanical structure for rotating the direction of the electric field of the radio waves with respect to the sample is also complicated. In other words, if the sample is a strip-shaped material, in order to non-destructively inspect it, the cavity resonator is divided into upper and lower parts, the sample strip is passed between them, and the upper and lower cavity resonators are rotated synchronously. Because it has to be structured, it becomes very complex structurally.

C. Problems to be Solved by the Invention In the previously proposed methods that utilize high frequencies, devices are distributed on both sides of the material to be measured, resulting in a complex structure, narrow entrances and exits for the sample, and a closed measurement space. However, it is better than using infrared light because it requires the radio waves to be able to pass through the sample, but there is a limit to the thickness of the sample, and even paper can only be 0.3 mm thick. There is a problem in that it is difficult to measure cardboard, etc. due to the limited degree of measurement, and it is impossible to measure general sheet materials, bars, blocks, etc. The present invention solves these problems when using high frequency radio waves.

D. Means for solving the problem: Inject a high-frequency radio wave onto the sample surface, detect the reflected radio wave on the same side of the sample, and rotate the electric field of the incident radio wave and the sample relative to each other to detect the reflected radio wave at that time. Changes in detection intensity are measured.

E. Effect The previously proposed method using high-frequency radio waves utilizes the fact that the absorption of radio waves differs depending on the orientation direction of molecules, fibers, etc. in the sample. By analogy with light, reflection occurs on the sample surface, part of it is reflected from the sample surface, part of it enters the sample, part of it is absorbed, and the rest is transmitted. Therefore, it is expected that the transmitted radio waves have information regarding orientation, but the reflected radio waves do not have information regarding orientation. However, experiments revealed that reflected microwave waves also contain information about fiber orientation. This is suitable for measuring the orientation of organic materials from 300 MHz to 100 GHz (wavelength 1 m to 0.3
This seems to be due to the fact that the wavelength of the radio wave (cm) and the thickness of the sample are about the same or longer. In any case, since the orientation of the fibers is measured using reflected waves, the apparatus can be placed all together on one side of the sample, resulting in a simple structure and the sample measurement space being an open space, making it easier to handle the sample. For example, operations such as heating the sample from one side and then measuring it, or applying moisture to the sample on the other hand and measuring it, are also possible, and features such as visual observation and orientation measurement can be achieved at the same time at the same location on the sample surface.

Embodiment FIG. 1 shows an embodiment of the present invention. A sample 1 is placed on a rotating table 2. A waveguide 3 has an open end facing the sample 1, and the open end serves as an electromagnetic horn 4. A coaxial waveguide converter 5 is flange-coupled to the end opposite to the open end of the waveguide 3, and the coaxial waveguide converter 5 and the oscillator 6 are connected by a coaxial cable 7. Another waveguide 8 is attached to the side of the waveguide 3, and slits are cut in the boundary wall between the two waveguides at 1/4 wavelength intervals in the tube axis direction. A directional coupler 10 is constructed, and the lower end of the waveguide 8 is a non-reflection end. Therefore, even if a wave traveling downward through the waveguide 3 is separated and enters the waveguide 8, it will be absorbed at the lower non-reflection end. The other waveguide 3
When the wave propagating to the information inside the waveguide 8 is divided into the waveguide 8, the information propagates inside the waveguide 8 to the detector 1 via the coaxial waveguide 11 and the coaxial cable 12 connected to the upper end of the waveguide 8.
3 and is detected. A stub 14 is installed near the electromagnetic horn connection part of the waveguide 3 so that its position in the tube axis direction can be adjusted.
is installed. The sample stage 2 is coated with non-reflective paint to absorb incident microwaves. A microwave is emitted from the horn 4 toward the sample stage 2 without a sample placed thereon, and the position of the stub 14 in the tube axis direction and the amount of protrusion into the tube are adjusted so that the detection output of the detector 13 is minimized. , the reflection from the tube end of the waveguide 3 is minimized. After making these adjustments, place sample 1 on sample stand 2.
When the sample table 2 is placed on the sample stage 2 and the sample stage 2 is rotated, and the relationship between its angular position and the output of the detector 13 is recorded in polar coordinate format, the relationship between the angle between the sample direction and the electric field direction of the incident microwave and the microwave reflectance can be obtained. is found. This is because the microwaves that are shunted into the waveguide 8 and detected by the detector 13 are only waves that travel upward in the waveguide 3, and the reflection at the end of the waveguide 3 is minimized. This is because what is actually detected by the detector 13 is mostly reflected waves from the sample. Note that the stub 14 for canceling tube end reflections can be omitted by simply attaching a horn to the open end of the waveguide 3.On the other hand, when it is desired to completely eliminate tube end reflections, a cavity for impedance matching is used to guide the wave. It may be inserted between the tube and the horn.

FIG. 2 shows another embodiment of the invention. In this embodiment, instead of rotating the sample 1 in the previous embodiment,
A rotary joint 15 is inserted in the middle of the waveguide 3, and the rotary joint 15 is rotated to rotate the direction of the electric field of the microwave incident on the sample 1. In this type, the sample is a strip-shaped material in the longitudinal direction. Since the measurement can be performed while the strip material is being fed, it is possible to measure it during the manufacturing process of the strip material.

In each of the above-mentioned embodiments, the reason why the non-reflective paint is applied to the sample stage 2 on the back of the sample is because the microwaves that have passed through the sample are reflected by hitting other objects, enter the detector 13, and are reflected from the sample. This is to increase the background level with respect to the waves and to prevent the S/N ratio of the signal with respect to the anisotropy of the sample from decreasing. The same effect can be obtained by making the sample stage metal so that it reflects microwaves well. In the case of a sample with oriented wood fibers, such as paper or wood, the direction of the electric field of the microwave is the direction in which the transmitted microwave is attenuated the most and the reflectance is low, so when measuring a thin sample, what is detected by the detector 13 is The wave reflected by the sample and the wave that passes through the sample, is reflected by the sample stage, passes through the sample again, and is attenuated twice by the sample; both carry information about the fiber orientation of the sample in the same phase. Therefore, the signals related to fiber orientation are strengthened, and the measurement sensitivity is improved.

In the embodiment shown in FIG. 3, a pulsed microwave oscillator is used as the microwave oscillator 6. Components corresponding to those in the embodiment shown in FIG. 1 are designated by the same reference numerals, and detailed description thereof will be omitted. The output of the detector 13 is applied in pulse form to a smoothing circuit 18 through a gate circuit 17, smoothed, and input to a recording device 19. The gate circuit 17 transfers the output pulse of the oscillator 6 to the delay circuit 2.
The delay circuit 20 is designed to be opened by a pulse signal delayed by 0, and the delay circuit 20 is set so that the timing at which the gate circuit 17 opens coincides with the timing at which the detection output of the reflected wave from the sample 1 is output from the detector 13.
delay time is set. Since the microwaves emitted from the electromagnetic horn 4 have a wide range of directions, simply preventing the waves transmitted through the sample from being reflected by other objects and entering the detector 13 will prevent the waves reflected from objects other than the sample from entering the detector 13. Unable to eliminate interference. However, in this embodiment, since the timing at which the gate circuit 17 is opened coincides with the timing at which the reflected waves from the sample are detected, the interference effect of the reflected waves from other objects can be significantly reduced.

FIG. 4 shows an embodiment having the configuration shown in FIG. Figure 4a uses a pine board with a thickness of 10 mm as a sample.
The frequency used is 3490.25MHz, the radial direction in the figure is the electric field direction of the microwave, the direction of the pine fiber is the y-axis direction, and the radial length indicates the relative value of the reflected wave detection output. The graph is almost elliptical, and the ratio of major axis to minor axis is
1.9:1.0. In the case of this example, transmitted microwaves cannot be detected when the wood board has a thickness of 10 mm, making it impossible to measure using conventional methods. Figure 4b is a sample of machine-made paper, with a working frequency of 3491.85MHz, y
The axial direction is the flow direction of the pulp suspension water, and the fibers are oriented in that direction, but the ratio of the major axis to the minor axis in the graph is
1.3:1.0, the degree of fiber orientation is lower than that of pine wood. Figure 4c shows a sample of a carbon-containing epoxy resin plate with a thickness of 5 mm, and the operating frequency is
At 3475.13MHz, the y-axis direction is the stretching direction of the resin, and it can be seen that the carbon fibers are significantly oriented. In this example as well, detection of transmitted microwaves is almost impossible.

Effects In the present invention, since high-frequency waves reflected from a sample are detected, the devices are arranged all together on one side of the sample. This is a very advantageous feature when measuring the anisotropy of materials such as materials, and the device structure is simple. In addition, since the sample can be measured in an open state rather than being introduced into a closed space such as a cavity resonator, it is easy to exchange the sample in and out, and there are no restrictions on the shape of the sample. However, it can be measured as is, making it suitable for non-destructive testing. Furthermore, since reflected waves are detected, it is possible to measure even thick materials or materials with high absorption in which almost no transmitted radio waves are detected. Furthermore, since the sample can be measured in an open space, it is possible to directly measure samples that are hot or humid and generate steam. Measurements such as tracking changes in sex can also be easily performed. Note that it is also possible to calculate the complex conductivity of the material from the detected output of the reflected wave.

[Brief explanation of drawings]

FIG. 1 is a side view of an apparatus according to an embodiment of the present invention, and FIG.
The figure is a side view of another embodiment, FIG. 3 is a side view and configuration block diagram of still another embodiment, and FIGS. 4 a, b, c
are graphs of actual measurement examples.

Claims (1)

[Claims] 1 Place the emitting end of the high-frequency radio wave toward the sample,
A means for detecting the reflected radio waves from the sample is provided by arranging a receiving end of the high-frequency radio waves reflected from the sample on the same side of the sample as the emitting end, and the sample is rotated around the direction of incidence of the incident radio waves. 1. An apparatus for measuring the orientation of fibers constituting a sample, comprising a mechanism or a mechanism for rotating the polarization direction of radio waves incident on the sample.