JPH075154A - Method for automatically deciding pass/fail of concrete product by knocking - Google Patents

Abstract

PURPOSE:To allow automatic decision of internal defect with high accuracy by processing the data of impact sound produced by knocking a concrete product at many points and setting a decision criterion for each product. CONSTITUTION:An ALC(Aerated Lightweight Concrete) product transferred on a conveyor 1 is knocked vertically by means of a hammer unit 4 provided, at the head of an air cylinder, with a hammer head 3 in order to knock the concrete product with constant force. A sound level meter 5 collects the sound and produces a sound pressure. An A/D converter 6 converts an analog AC voltage signal, corresponding to the sound pressure, into a digital signal which is fed to a personal computor 7. The personal computor 7 calculates the peak value of sound pressure at each knocking point, the sound level at nondefective part, the reference sound level, etc. Internal defect is then decided with reference to the reference sound level and the inspection results are displayed on a screen.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a judging method which makes it possible to automatically detect the presence or absence of internal defects such as concrete products such as ALC.

[0002]

2. Description of the Related Art In concrete products such as ALC products, quality defects such as cracks may occur after molding due to subtle differences in the raw materials and production conditions. When such an internal defect is present, a predetermined strength cannot be obtained, and it may be destroyed during use, which may be dangerous. Therefore, in order to control the quality, it is necessary to inspect the product after curing for cracks. Conventionally, as this type of product inspection method, a method in which a person hits the product and hears the difference in the magnitude of the hit and the timbre is mainly performed.

[0003]

In the conventional inspection method as described above, it is difficult to carry out a constant inspection because there is an individual difference in the discrimination by the human sensory evaluation and the degree of heat is required. In addition, there is a method of judging the presence or absence of a defect based on an absolute judgment standard in advance for all inspected products, such as a nondestructive inspection based on a difference in the frequency of impact sound generated at that time. However, when the surface condition of the lightly tapped portion and the size of the inspected product are various, the frequency value of the non-defective part greatly varies, and it is difficult to set an absolutely constant determination standard, and the inspection accuracy thereof also deteriorates. Therefore, an object of the present invention is to process the sound pressure data of impact sound when a large number of products are tapped as a test for the presence or absence of internal defects in concrete products, for example, products having air bubbles inside ALC products, and the judgment criteria are processed for each product. The purpose of the present invention is to provide a method capable of automatically determining the presence or absence of an internal defect with high accuracy.

[0004]

The present invention provides the following method in order to achieve the above objects. That is, a concrete product is tapped at multiple points with a hammer, the sound pressure peak value of the generated sound is measured, and an average value of a plurality of points having small sound pressure peak values is defined as a good part sound pressure. A method for automatically determining the quality of a concrete product by tapping sound is characterized in that the presence or absence of a defect in concrete can be determined by sound pressure, with a defect that exceeds a predetermined permissible width of part average value as a defect. The method described above was invented from various experiments, and the same product was tapped at multiple points, and the sound pressure of the impact sound generated at that time was set and the judgment standard was set for each product. Internal defects (cracks) could be reliably detected. Specifically, tap the same concrete product at multiple points with a hammer, measure the sound pressure peak value of the impact sound at each point generated at that time, and average the multiple points of the small sound pressure peak values at these multiple points. The value is defined as the good part sound pressure value, and the good part sound pressure value is 1.
A criterion is set to 5 times to 3.5 times, and those exceeding this criterion are judged to be defective. In other words, those exceeding a predetermined permissible width based on the average value of the product are defective. To do. In the first place, the difference in sound pressure between the defective part and the non-defective part shows that most of the striking force of the non-defective part is transmitted to the entire product and is absorbed, whereas the transmission of the striking force of the defective part is transmitted to the space part such as a crack. The sound pressure is blocked because of a small difference in absorption, and the sound pressure is reflected as a divided sound, resulting in a large difference in sound pressure between the two. Further, the sound of the defective portion is generated from the entire surface such as a crack, whereas the non-defective portion is generated only from the hit surface. The difference between the surface source and the point source of the sound source is also one of the causes of the difference in sound pressure between the two. The reason why the average value of a plurality of points having a small sound pressure peak value is set as the good part sound pressure value is as follows. That is, as described above, the defective portion is higher in sound pressure between the defective portion and the good portion,
Considering that the defects are partial and not in the whole area, and the value of the good part is not always constant in the ALC plate containing bubbles, the sound pressure of the good part is smaller when determining the reference value. The sound pressure representative value of the good part is an average value obtained by taking a plurality of points from a small sound pressure value of.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a schematic configuration diagram of an experimental apparatus according to an embodiment of the present invention. A traveling on the conveyor (1)
A hammer device (4) having a hammer head (3) attached to the tip of an air cylinder is used to strike the LC product (2) perpendicularly to the impact surface. The tapping sound is collected by a sound level meter (5) installed near the hammer device (4), and an analog AC voltage signal corresponding to the magnitude of sound pressure output from the noise section is converted into an analog / digital converter (6). Convert it into a digital signal and import it into a personal computer (7) (hereinafter referred to as a personal computer). The PC (7) calculates the sound pressure peak value of each hitting point, the sound pressure value of the non-defective part, the judgment sound pressure reference value, etc., and automatically judges the presence or absence of an internal defect based on the sound pressure level with the judgment reference value. Display the inspection result on the screen.

Now, for an ALC product having internal cracks at the corners of the product as shown in FIG. 2, the points d ₁ to d ₁₆ are tapped near the center in the thickness direction of the inspected product, The result of measuring the sound pressure peak of is shown in FIG. Crack part d
The sound pressure peak of the tapping sound generated from ₁ is much larger than that of the non-defective product without cracks, and the sound pressure peak ratio of both (hereinafter S
/ N ratio) is three times or more. Since this S / N ratio is large, it becomes possible to set a reference value between the defective portion and the non-defective portion, and it is possible to determine whether or not there is a striking point that emits sound pressure generated from this reference value. The presence or absence of can be determined.

The determination method will be described with reference to FIG.
First, a sound pressure value which is a non-defective part is obtained from sound pressure peak values at a large number of points obtained from one piece of the inspected product. As the method, the sound pressure of the defective portion is higher than that of the non-defective portion, and therefore, a plurality of points (half of all striking points in the embodiment) are taken from the one having a small value of the sound pressure peak at many points, and the averaged value is taken. Sound pressure value (hereinafter referred to as the good part value). A solid line (8) in FIG. 4 represents the good part value. Next, a determination standard is set at a location that is relatively several times, for example, 1.5 to 3.5 times (two times from the good part value in the embodiment) from this good part value. That is, a predetermined allowable width of the good part average value is set. A broken line 9 in FIG. 4 represents this allowable width. The allowable width (determination reference value) is compared with the sound pressure peak value at each point, and if there is a point having a value larger than the allowable width, it can be determined that the measurement position has an internal defect. Also in this embodiment, the sound pressure peak value at the point d ₁ where there is a crack is larger than the allowable width. In this way, by determining the allowable width for each inspected product and determining the presence / absence of a defect, it is possible to reliably determine the presence / absence of an internal defect without being affected by the variation in the allowable width due to the size of the inspected product.

FIGS. 5 and 6 show the types of defects that can be detected by the impact inspection of the present invention. (10) in the figure is ALC
Product, (11) indicates a reinforcing bar, and (12) indicates a fault. In any case, the present invention utilizes the difference in the sound pressure between the internal defect portion and the non-defective portion of the product, hits the same product multiple times, and measures the sound pressure at each point with a sound level meter. Let the computer calculate the peak pressure value. And 30% to 70% of the total sound pressure peak value
The value obtained by averaging the points with a small sound pressure peak value is defined as the good part value, and the allowable width is set at a place of 1.5 times to 3.5 times from the good part value. Let me calculate if there is it or not. In this way, by setting the allowable width for each inspected product and monitoring the sound pressure peak value at each point with the allowable width, it is possible to automatically determine the presence or absence of internal defects inside the product regardless of the size of the inspected product. .

[0009]

The present invention measures the sound pressure peak value of the sound generated by tapping a concrete product with a hammer at a number of points, and determines the average value of a plurality of points having a small sound pressure peak value as the sound pressure of the good part. The sound pressure is used to determine the presence or absence of defects inside the concrete, with defects exceeding the prescribed allowable width of the good part average value as defective parts, and the presence or absence of product defects is highly accurate regardless of the size of the inspected product. There is a feature that can be automatically determined by.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an experimental apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing an internal defect of one embodiment according to the present invention.
Diagram showing LC products and hit points

FIG. 3 is a diagram showing sound pressure peak values at various points when the ALC product shown in FIG. 2 is hit.

FIG. 4 is a diagram showing an internal defect determination method according to one embodiment of the present invention.

FIG. 5 is a perspective view showing types of defects that can be detected by the present invention.

FIG. 6 is a plan view showing a cut ALC product showing another kind of defects detectable by the present invention.

[Explanation of symbols]

 1 Roller conveyor 2 ALC product 3 Hammerhead 4 Hammer device 5 Sound level meter 6 Analog / digital converter 7 Personal computer 8 Sound pressure value of non-defective part 9 Judgment reference value

Claims (1)

[Claims] 1. A concrete product is tapped at multiple points with a hammer to measure a sound pressure peak value of a sound generated from the concrete product, and an average value of a plurality of points having a small sound pressure peak value is defined as a good part sound pressure, A method for automatically determining the quality of a concrete product by tapping sound, wherein the presence or absence of a defect inside concrete can be determined by sound pressure with a defect portion exceeding a predetermined permissible width of the good portion average value as a defect portion.