JPH0444952B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an ultrasonic diagnostic method for diagnosing the shape and position of a defect inside an object using ultrasonic waves.

[Prior art]

An ultrasonic diagnostic method for relatively easily determining the location and shape of internal defects in materials with extremely high ultrasonic attenuation, such as wood and plastic, is disclosed in Japanese Patent Application No. 115255/1983 There was a method shown in ``Publication No. 5950''.

For example, this method will be explained using a case where a rotten part (defect part) of a wooden telephone pole is detected. As shown in Figure 1, pine wood, which is commonly used as utility poles, has decayed areas H that follow the growth rings. here,
If the ultrasonic propagation time is measured with the probe in contact with the positions P ₁ and P ₁ ', it will be approximately equal to the propagation time between diameters in a healthy area (for example, obtained when measuring at 1 m or more from the ground). On the other hand, when we measure the propagation time by touching the probes to P ₅ and P ₅ ', we find that there is a decayed area on the line connecting both probes, so the propagation of the ultrasonic wave goes around the decayed area. Therefore, the propagation time is longer than that for a healthy part, and the existence of a decayed part can be detected thereby.

However, the mode of decay in Japanese pine and other trees differs from that in cedar; as shown in Figure 2, the center of the tree is rotten, and in many cases, the rot is present even in areas 1 m or more from the ground. Therefore, in the conventional method, it was not possible to measure the ultrasonic propagation time in a healthy part, and the propagation time in a place where there was a decayed part was mistakenly taken as the value of the healthy part. Furthermore, in the case of the wooden pole shown in Figure 2, the ultrasonic propagation times between P ₁ and P ₁ ' and between P ₅ and P ₅ ' are almost equal, so the ultrasonic propagation time in the healthy part is incorrect. If the measurement is repeated, there is a drawback that it may be mistakenly determined that the part is completely healthy.

[Purpose of the invention]

This invention was made in view of the above circumstances, and even when there is a defect in the center of the object to be measured,
An object of the present invention is to provide an ultrasonic diagnostic method that can detect both the shape and position of a defective part using ultrasonic waves.

[Structure of the invention]

This invention utilizes ultrasonic waves that emit ultrasonic waves from one point on the outer periphery of the object to another point within the object, and detect defects within the object based on the ultrasonic propagation time between transmission and reception. In the diagnostic method, the position of one probe is fixed, and the ultrasonic propagation time is measured at multiple positions while the other probe is moved away from the probe along the outer periphery, and the distance between the probes is determined. This method is characterized by detecting the position and shape of a defect by finding an inflection point in a graph showing the relationship between ultrasonic propagation time and ultrasonic wave propagation time.

〔Example〕

FIG. 3 is an external view of a diagnostic device to which the method according to the present invention is applied. In this figure, 1 is an ultrasonic transmitter/receiver, and 2a and 2b are a transmitting probe and a receiving probe each using a normal Languevent type transducer. probe,
Reference numeral 3 denotes a transmitting/receiving unit; 2a and 2b respectively a transmitting contact and a receiving contact each using a normal Languevent type transducer; 3 an ultrasonic wave emitted from the transmitting probe 2a is received by the receiving probe 2b; A digital display that displays the ultrasonic propagation time until
5 is a digital display that displays the propagation time ratio of previous and subsequent measurements; 5 is an image display that displays the shape and position of a defect within the object to be measured; 6 is a minicomputer; and 7 is a power supply device. Note that liquid crystal displays are used for the digital displays 3 and 4 and the image display 5.

Next, the diagnosis method using this ultrasonic diagnostic device,
An example of detecting a rotten part (defective part) of a wooden telephone pole will be explained.

Figure 4 shows a wooden telephone pole with a rotten part in the center, and the positions where the outer circumference is divided into 16 equal parts are P ₁ ,
Let P ₂ ,...P ₁₆ . First, position the transmitting probe 2a.
At _P1 , the receiving probe 2b is brought into contact with position _P2 and the propagation time is measured. Next, the propagation time is measured again with the transmitting contact 2a at the above position and only the receiving contact 2b at position _P3 . As described above, transmitting probe 2a
position only the receiving probe 2b while keeping the position fixed.
Measure the propagation time while changing to P ₄ , P ₅ , P ₆ and P ₇ . At this time, the relationship between the straight line distance L between both probes and the propagation time T is shown in FIG.
In the plot in Fig. 5, the receiving probe positions are P ₁ , P ₂ , P ₃ , P ₄ , P ₅ ,
Corresponds to P ₆ , P ₇ and P ₈ . This shows that the propagation time suddenly increases when moving from P ₅ to P ₆ . This is because there is a decayed part H in the middle of the ultrasonic propagation path connecting P ₁ and P ₆ . Therefore, as shown in Figure 4, the point in contact with the decayed part is approximately the midpoint _F1 of the line connecting _Q1 and _P1 , the midpoint between _P5 and _P6 .
It is expressed as

Similarly to the above, with P ₃ as the transmitting probe 2a,
The propagation time is measured while changing the position of the receiving probe 2b from P ₄ to P ₅ . Then, the inflection point can be found as in FIG. 5, and the approximate point F ₂ that is in contact with the decayed part can be found. Similarly, P ₅ ,
If you measure from P ₇ , P ₉ , P ₁₁ , P ₁₃ , P ₁₅ as starting points, you will get F ₁ , F ₂ ..., F ₈ , so if you connect these with a straight line you will get the result shown in Figure 6. .

As can be seen from the comparison between FIG. 4 and FIG. 6, according to the present invention, the position and shape of the decayed part at the center of the wooden pillar can be detected by a relatively simple method.

It is not always necessary to place the transmitting probe at 8 locations, but it is known that in cases of central rot such as in Japanese pine trees, the rot occurs in an almost circular shape, so the number of approximate points F can be reduced to By approximating to a curve, the measurement time can be shortened.

〔Effect of the invention〕

As explained above, the method according to the present invention detects the position where the ultrasonic propagation path touches the defective part by finding the inflection point in the relationship between the distance between the ultrasonic probes and the propagation time. Therefore, both the position and shape of the defective portion can be detected, and as a result, imaging can be performed. Furthermore, the measurement of the propagation time is performed while changing the propagation distance by fixing one probe and moving the other probe in the circumferential direction of the utility pole. Even in the case of a utility pole made of a material such as Japanese pine in which rotten parts occur in a circular pattern around the axis, the presence of rotten parts can be reliably detected. Therefore, there is an advantage that repairs, replacements, etc. can be carried out accurately after a defective part is discovered. Furthermore, according to the present invention, relatively low-frequency ultrasound can be used, which provides the advantage that the diagnostic apparatus can be constructed easily and at low cost. As a result of the above, the method according to the present invention is extremely effective in detecting defects in wooden utility poles, trees, house pillars, etc., and in detecting "s" in castings.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of an object to be measured, such as cedar wood, which has a defect on its outer periphery, Figure 2 is a cross-sectional view of an object to be measured, such as a Japanese pine tree, which has a defect in its center, and Figure 3 is a cross-sectional view of an object to be measured, such as a Japanese pine tree, in which a defect occurs in the center. A perspective view showing the configuration of the diagnostic device, FIG. 4 is an explanatory diagram of a method for diagnosing a rotten part of a wooden utility pole using the device shown in FIG. 3, and FIG. 5 is a graph showing the relationship between the distance between probes and propagation time. , and FIG. 6 is a diagram showing a state in which the rotten part of the wooden pillar shown in FIG. 4 is imaged using the apparatus shown in FIG. 3. 1... Ultrasonic transmitting and receiving unit, 2a... Transmitting probe,
2b...Reception probe, 3, 4...Digital display, 5...Image display, 6...Mini computer.

Claims (1)

[Claims] 1 Set a measurement cross section in the object to be measured, emit ultrasonic waves inward from a part of the outer circumference of the measurement cross section, and transmit the emitted ultrasonic waves to the outer circumference of the measurement cross section. received at another point on the
In an ultrasonic diagnostic method for detecting defects in the object to be measured based on the ultrasonic propagation time between transmission and reception, the position of one probe is fixed at a point on the outer periphery of the measurement section, and the position of the other probe is fixed at a point on the outer circumference of the measurement cross section. By moving the probe along the outer periphery of the measurement section, the ultrasonic propagation time is measured at multiple positions while increasing the linear distance from the one probe, and the distance between the probes and the ultrasonic propagation are measured. An ultrasonic diagnostic method characterized by detecting the position and shape of the defect by finding an inflection point in a graph showing a relationship with time.