JPS6135349A - Inspecting method of ultrasonic diagnosing device - Google Patents

Abstract

PURPOSE:To inspect the deterioration state of a wood pole with high precision by attenuating an ultrasonic wave to a constant value when transmitting and re- ceiving the ultrasonic wave to and from the wood pole and measuring the propagation time of the ultrasonic wave. CONSTITUTION:The ultrasonic wave signal is transmitted from a transmission terminal 2a to a reception terminal 2b in a sectional direction of the wood pole 1. At this time, if there is a deteriorating part H, the ultrasonic wave signal passes through paths R1, R2, and R3, etc. Further, the ultrasonic wave signal is attenuated to the constant value and transmitted and its propagation time is measured and compared with the normal propagation time. At this time, a standard piece is used to calculate the frequency attenuation and propagation time of the ultrasonic wave previously, and a threshold value is so determined the propagation time is long. Then, the ultrasonic wave increases in propagation time above the threshold value regardless of the paths R1, R2, and R3 if there is the deteriorating part H. Therefore, the deterioration of the wood pole is inspected precisely because the ultrasonic wave signal is attenuated to the constant value.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for inspecting whether an ultrasonic device for inspecting decay of wooden poles is functioning normally and with high precision.

[Prior art]

BACKGROUND ART Conventionally, an ultrasonic device (Japanese Patent Application No. 5g-7/wo?j) has been provided that easily measures the internal decay of a wooden pole and creates a single image. The measurement principle of this device will be explained below. In Fig. S, 1 is a cross section of a wooden pole, H is a decayed part, 2a is a transmitting probe, 2b is a receiving probe, and 3 is an ultrasonic transmitting/receiving section. Here, first, the propagation time of the ultrasonic wave between diameters is measured in the healthy part and used as the reference propagation time. In the case of a water column whose lower end is buried underground, the decay form shown in Figure 6 is common, so the propagation time in a healthy part can be measured at about /m above the ground. In this figure, 4 is a wooden pillar and E is underground. Next, one of the probes is placed in position Po and the other is placed in contact with Po to measure the propagation time, but since there is a decayed part on the straight line connecting Po and Po', the ultrasonic waves cannot travel straight; The propagation time is longer than the standard propagation time because it bypasses the section. Therefore, it can be determined from the propagation time whether there is decay on the straight line between the probes. Furthermore, the more severe the degree of decay, the longer the propagation time.

In Figure 7, the horizontal axis is the ratio of the length of the decayed part to the diameter (referred to as the decay length ratio diagram), and the ratio to the standard propagation time (
The vertical axis shows the relationship between the two, with the propagation time ratio (goods) as the vertical axis. From this figure, the degree of decay can be determined by determining the propagation time ratio. Furthermore p 1−
p1', p2-p2'.

...P7-P7' and propagation time will be measured from now on.

P3 P3'e P4 P4'+ P5 P5'
The propagation time ratio was 709% between the two, making it clear that there was no decay. From the above results, it is possible to clarify the state of decay across the cross section of the wooden pillars.

Note that since the above measurements are performed point-symmetrically, it is not known where the decay is between the probes. Therefore, as shown in Figure 5, the central angle between the probes is set to θ°, and the propagation is Measure time. At this time, the ultrasonic waves propagate in an arc as shown by the arrow in FIG. This type of propagation occurs because wooden poles have an annual ring structure and have heartwood and sapwood that have different densities. The measurement is Po p4
1P4 Po'+ Po P4+ P4-Po
and measure times.

If there is no decay along the propagation route, it is about θ% of the standard propagation time mentioned above, and if there is decay like between +P4 and Po, the propagation time will be longer, so it is important to know approximately where it is. I can do it.

The measurement principle has been explained above, and the above measurement makes it possible to visualize the shape of internal decay and, along with this, calculate the area of the decayed part, thereby making it possible to quantify the degree of decay.

When a device for diagnosing the decay of wooden poles is configured based on the above-mentioned principles, in order to determine whether the device can be used as a diagnostic tool, it is necessary to All you have to do is create a reference piece and check whether it outputs correct results. In Figure 9, the shore is a pseudo-decayed area (
(artificially created cavities), and dry cracks occur naturally. The decay area ratio (ratio of decayed parts to the cross-sectional area) in the 9th position is 70%, (B) is 20%, (C1 is 3
0%.

[Problem that the invention seeks to solve]

In the above device inspection method, the characteristics of wood are:
The drying cracks shown in FIG. 2 occur, and since the specific surface area of a small piece such as the reference piece is large, not only does drying occur and the drying cracks progress, but a large number of minute cracks also occur. In addition to these characteristics, since wooden pillars are natural products, no two pillars can be made exactly the same. For this reason, wooden samples have the drawback of being significantly lacking in stability as reference pieces. However, when there are a large number of wooden pole decay diagnostic devices, there is no suitable method for checking their accuracy.

The present invention has been made in view of the above circumstances.

The purpose of the present invention is to provide a method that can easily and reproducibly check the accuracy of an ultrasonic diagnostic device.

[Means for solving problems]

The present invention is characterized in that when checking the accuracy of the apparatus, the accuracy is checked by defining the ultrasonic propagation time when the ultrasonic signal is attenuated by a certain value.

〔Example〕

FIG. 1 is a diagram showing an embodiment of the present invention, where 5 is a rod made of plastic such as acrylic whose end surfaces are parallel to each other, and 6 is an attenuator for attenuating the signal from the probe 2b.

To test the device, a certain amount of attenuation is applied to the ultrasonic signal using an attenuator 6, and the accuracy of the device is tested by checking whether or not a specified propagation time has been reached.

The reason why the accuracy test can be performed using the above method will be explained. The estimated path of ultrasonic propagation when there is a decayed part will be explained using Figure 1. If the ultrasonic waves travel in a straight line even inside a wooden pillar, the path R1 will be the shortest course. Further, considering the property that the ultrasonic propagation speed is faster in the circumferential direction and in the diametrical direction, a course such as the path R2 that curves slightly inward becomes the shortest. Moreover, since a smooth course is natural as a route, route R3 is considered in this case. Various routes are possible, but since the frequency of the ultrasonic waves used here is relatively low (j0KHz~), it does not propagate strongly in a straight line and propagates smoothly.
It is considered that this course is close to any of the courses R1 to R3 above. Here, the extension of propagation time due to the presence of rotten parts is R
Even if course 3 were taken, the length of the path would be at most 76 times the length of half the circumference, and there would be no change as shown in Figure 5. Therefore, the extension of propagation time due to the presence of decayed parts is not simply due to a longer path. That is, this is due to the large ultrasonic attenuation ability of the wooden pillar. Figure 3 shows the length 2 of the machine W1 and W2 selected from several ultrasonic devices using the method shown in Figure 1.
This shows the results of measuring the propagation time of 0-stroke acrylic. The horizontal axis shows the attenuation amount by the VC attenuator, and the vertical axis shows the propagation time. As is clear from Fig. 3, the propagation path length is
It can be seen that even if there is no change, the propagation time becomes extremely long when attenuation occurs. The same is true for wooden poles; in addition to the longer path, the resulting increase in attenuation greatly affects the length of propagation time. Note that the reason why the machine difference occurs in FIG. 3 is considered to be due to the size of the threshold value for signal detection in propagation time measurement. That is, Figure 1 shows the principle of measuring propagation time, in which a transmitted wave propagates while attenuating and becomes a received wave. The propagation time is expressed as the time from the start of transmission S until a signal reaching a certain threshold is received. Here, if the threshold value is set to Ll in FIG. 7, there is no difference in the propagation time whether the attenuation is large or small, but if it is set to L2, the propagation time becomes longer as the attenuation increases.

Decay diagnosis is performed by measuring the propagation time, but due to the above situation, the propagation time varies depending on the device, so accuracy cannot be confirmed.

If the propagation time at a certain level of attenuation is defined by the method shown in Fig. 1, the machine difference shown in Fig. 3 will not occur, and the accuracy of the diagnostic instrument described here will be determined.

Since it is possible to ensure a fixed propagation time even in objects with attenuation, there is no need to use an unstable reference piece as shown in FIG.

〔Effect of the invention〕

As explained above, according to the present invention, when performing an inspection such as checking the accuracy of a wooden pole decay diagnosis device, plastic such as acrylic can be used as a reference piece instead of using unstable wood. This method has the advantage that many devices can be tested easily and with good reproducibility.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention, and is an explanatory diagram showing an inspection method of an ultrasonic diagnostic device, and FIG. 3 is a diagram showing an estimated propagation path of ultrasound waves of a wooden pole with internal decay. Figure 3 is a graph showing the relationship between ultrasonic attenuation rate and propagation time, Figure 9 is a graph showing the measurement principle of ultrasonic propagation time, and Figure 5 is a method for diagnosing wood pole decay using an ultrasonic diagnostic device. Figure 6 is an explanatory diagram showing the decay form of wooden poles, Figure 7 is a graph showing the relationship between decay length ratio and propagation time ratio, and Figure 3 shows a method for diagnosing wooden pole decay. The explanatory drawings and FIGS. 9(C) to 9(C) all show examples of wooden reference pieces. 1... Wood pillar cross section, 2a... Ultrasonic transmitter, 2b... Ultrasonic receiver, 3... Ultrasonic transmitter/receiver. Figure 1 Figure 2 2〇１\, 〉, Mepa) R2 Go I'-R3

Claims (1)

[Claims] When checking the accuracy of an ultrasonic diagnostic device that uses ultrasonic waves to inspect wood poles for decay, the accuracy can be checked by specifying the ultrasonic propagation time when the ultrasonic signal is attenuated by a certain value. An inspection method for an ultrasonic diagnostic device characterized by the following.