JPH0566545B2 - - Google Patents

Description

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

[Conventional technology]

The applicant previously proposed a method for detecting defects in the center of wooden columns using relatively low-frequency ultrasound (patent application filed in 1983).
−59042) was proposed. Therefore, this method will be briefly explained below.

FIG. 7 shows a cross section of a wooden utility pole with a decayed part H in the center, and the positions at which the outer circumference is equally divided into 16 parts are designated as P ₁ , P ₂ , . . . P ₁₆ , respectively. First, the transmission probe is brought into contact with the position P ₁ and the reception probe is brought into contact with the position P ₂ to measure the propagation time. Next, the propagation time is measured again with the transmitting contact at the above position and only the receiving contact at position _P3 . As described above, the propagation time is measured while changing only the receiving probe to positions P ₄ , P ₅ , P ₆ and P ₇ while keeping the transmitting probe fixed in position. 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. 8, the receiving probe positions correspond to P ₁ , P ₂ , P ₃ , P ₄ , P ₅ , P ₆ , P ₇ and P ₈ from the smallest L. From this, it can be seen that the propagation time suddenly increases when moving from P ₅ to P ₆ . this is,
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 Fig. 8, the points in contact with the decayed part H are approximately P ₅ and P _6.
It is expressed as the midpoint F ₁ of the line connecting the midpoint Q ₁ and P ₁ .

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 as P ₄ , P ₅ , etc. Then, the point of inflection can be found as in FIG. 8, and the approximate point _F2 that is in contact with the decayed part H can be found. Similarly, P ₅ ,
If we measure from P ₇ , P ₉ , P _{11 ,} P ₁₃ , P ₁₅ as starting points, we will obtain F ₁ , F ₂ . It will be done.

[Problem that the invention seeks to solve]

The method described above is an effective diagnostic method for round wood, as is clear from comparing Figures 7 and 8, but this method is only a method for diagnosing rot for circular wooden columns. , it cannot be used for diagnosing internal defects in rectangular pillars, and it has been desired to develop a diagnostic method for rectangular pillars.

[Means for solving problems]

The method for diagnosing defects in a rectangular column according to the present invention involves measuring the ultrasonic propagation time between two pairs of opposite sides at several locations in one cross section of a rectangular column, and measuring the intersection of the measurement lines where the propagation time is the longest between each pair of opposite sides. A first process of finding the center of the defect from the center of the defect, fixing either the ultrasonic transmitter or the receiver near the midpoint of one side in the one cross section, and moving the ultrasonic transmitter or receiver from a position close to the probe in the adjacent section. Or move the other receiver further away one by one,
A second process of finding the external tangent from the point of rapid increase in propagation time to the internal defect, and connecting several tangent points that are stopped by drawing perpendicular lines from the defect center to each of the external tangents with a smooth curve. The present invention is characterized in that defect detection is performed by a third process that represents the defect shape.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 to 6.

FIG. 2 is a cross-section showing an example of a rectangular column with internal decay, and position symbols arranged at equal intervals on its outer circumference are shown for the purpose of the following explanation.

First, ultrasonic transmitters are brought into contact with positions M ₁ and M ₁ ', and the ultrasonic propagation time is measured. Next is M ₂ ~
Measure the propagation time between M ₂ ′ and sequentially from M ₃ to _{M 3} ′, M ₄
〜M ₄ ′, ...M ₇ 〜M ₇ ′ are measured. Also,
Measurements are made in the same manner for N ₁ to _{N 1} ′, N ₂ to _{N 2} ′, ...N ₇ to _{N 7} ′. The relationship between these positions and propagation time is shown in Figures 3a and 3b. from now,
It can be seen that the maximum decay occurs above M ₄ to M ₄ ′ and above N ₄ to _{N 4} ′, and the intersection of both lines is the center Q of decay. In other words, the ultrasonic waves cannot propagate through the decayed area and take a long detour, but they do not propagate through the decayed areas, but they do travel around M ₄ ~ M ₄ ' and N ₄ ~
This is because the circuit becomes the most distant at N ₄ ′. In addition, in the case of a column with no decayed parts as shown in Figure 5, the propagation time becomes shorter as the growth rings pass closer to the center, as shown in Figure 6, and the characteristics opposite to those in Figures 3a and b are obtained. show. Therefore, the presence of internal decay can be known from the characteristics a and b in FIG.

Next, one of the probes is placed, for example, at M ₄ , which indicates the maximum propagation time, and the other probe is placed at N ₇ ' to measure the propagation time. Next, leave M ₄ on one side as is, set N ₆ ′ on the other side, and measure.
When N ₅ ', N ₄ '...N ₁ ' are successively moved away from M ₄ , their propagation times become as shown in Fig. 4, and a sudden change in propagation time appears in the middle. This is because the straight line connecting the probes crosses the decayed area, and this is the outer tangent of the internal decay. Therefore, if we draw a perpendicular line from the center Q of the decay found earlier to this tangent, we can find the point of contact _J1 with the decayed part. Next, by fixing one probe at N ₄ ' and moving the other probe away from M ₇ ' sequentially, the contact point J ₂ with the decayed part can be found in the same way as in the previous case. Thereafter, by measuring each side using the same method, the points on the outer periphery of internal decay can be determined.
J ₃ and J ₄ are required. And these four points
By the smooth curve connecting J ₁ , J ₂ , J ₃ , and J ₄ ,
As shown in Figure 1, the approximate shape of the decayed shape is determined.

〔Effect of the invention〕

As explained above, the method for diagnosing defects in rectangular pillars according to the present invention includes a first process of finding the center of an internal defect from the propagation time of ultrasonic waves, a second process of finding the circumscribed line to the internal defect, and a second process of finding the circumscribed line to the internal defect. By the third process of drawing a perpendicular line from the center to each external tangent line and connecting the stopping points with a smooth curve, it is possible to easily detect defects such as decay inside the rectangular column, and also to detect decay caused by termites, etc. It can also be used for diagnosis, etc.

[Brief explanation of drawings]

1 to 6 are diagrams for explaining the present invention, in which FIG. 1 is a diagram showing the defect shape of a rectangular column obtained by the present invention, and FIG. 2 is a diagram showing the defect shape of a rectangular column that is the object of diagnosis. Diagrams representing the shape, Figure 3 a, b
are the two rectangular pillars with internal defects shown in Fig. 2, respectively.
A diagram showing the relationship between the ultrasonic propagation time between a pair of opposite sides and its measurement position, FIG.
Fig. 5 is a diagram showing the cross-sectional shape of a rectangular column without internal defects, and Fig. 6 is the relationship between the ultrasonic propagation time and its measurement position between two pairs of opposite sides of the rectangular column without internal defects in Fig. 5. Figures 7 to 9 are diagrams for explaining the diagnosis method for circular pillars previously proposed by the applicant, and Figure 7 shows the defect shape of the circular pillar that was the subject of diagnosis. 8 is a diagram showing the relationship between the distance between the probes and the ultrasonic propagation time, and FIG. 9 is a diagram showing the defect shape of a circular pillar determined by the present diagnostic method. M ₁ to _{M 7} , M ₁ ′ to _{M 7} ′, N ₁ to _{N 7} , N ₁ ′ to _{N 7} ′…
...Measurement point, H...Defect.

Claims (1)

[Claims] 1 In a method of diagnosing internal defects in a rectangular column using ultrasound, the ultrasonic propagation time between two pairs of opposite sides in one cross section of a rectangular column is measured at several points, and the propagation time is the longest between each pair of opposite sides. The first step is to find the center of the defect from the intersection of the measurement lines, and fix one of the ultrasonic transmitter or the receiver near the midpoint of one side in the one cross section, and measure the center of the defect from a position close to the probe on the adjacent side. A second process of sequentially moving the other of the ultrasonic transmitter or the receiver away and finding the external tangent to the internal defect from the point where the propagation time increases; and by drawing a perpendicular line from the center of the defect to each external tangent. A method for diagnosing a defect in a rectangular column, characterized in that defect detection is performed by a third process in which a number of contact points that stop at each other are connected with a smooth curve to represent the defect shape.