JP2019148535A - Wood inspection method - Google Patents

Abstract

To provide a wood inspection method capable of accurately identifying a deteriorated part of a wood.SOLUTION: A wood inspection method uses a high-frequency moisture meter 2 and is configured to arrange a high-frequency transmission unit 3 and a high-frequency reception unit 4 which are parallel each other at a distance in a fiber direction D of a wood 1 to be inspected and so that longitudinal directions of the high-frequency transmission unit 3 and the high-frequency reception unit 4 are generally vertical to the fiber direction D, generate an electromagnetic wave to measure an electrostatic capacitance of the wood 1 to be inspected, and determine a degree of deterioration of the wood 1 to be inspected based on the electrostatic capacitance. The wood inspection method determines that the wood 1 to be inspected is in a high hydrous/low density state when the electrostatic capacitance of the wood 1 to be inspected is equal to or greater than a preset upper limit, and determines that the wood 1 to be inspected is in a low hydrous/low density state when the electrostatic capacitance of the wood 1 to be inspected is equal to or lower than a preset lower limit.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a wood inspection method using a high-frequency moisture meter.

  Conventionally, there has been a method of measuring the moisture content of wood and determining that it is highly likely that the wood has been impregnated with water if the moisture content of the wood is abnormally high, and that the wood is decayed or deteriorated. Known (see Patent Document 1 and Patent Document 2). In addition, as a device for measuring the moisture content of wood, a pair of electrodes are arranged in parallel at a distance, and a high frequency that measures the moisture content of wood by detecting a change in capacitance by flowing a high frequency through the wood. A moisture meter is known (Non-Patent Document 1). As shown in FIG. 6, the moisture content of wood using such a high-frequency moisture meter is measured so that each electrode is substantially parallel to the fiber direction of the wood in order to eliminate the influence of the dielectric constant due to the wood fibers. They are arranged side by side and are measured so that the traveling direction of the high-frequency electromagnetic wave is substantially perpendicular to the fiber direction of the wood.

JP 2004-317373 A JP 2005-168362 A

Ketto Science Laboratory Wood Moisture Analyzer HM-520 Instruction Manual

  By the way, when the measurement is performed so that the traveling direction of the high-frequency electromagnetic wave is substantially perpendicular to the fiber direction of the wood as described above, the path of the lines of electric force between the pair of parallel electrodes is the end of the electrode. Since the part to be measured is a healthy part, when there is a deteriorated part adjacent to the measurement part, a part of the lines of electric force will pass through the deteriorated part. There is a risk of being affected by the degraded part. In addition, when measuring a position close to the end of the wood, the lines of electric force pass outside the wood, and the measurement accuracy may be reduced. Therefore, there is a problem that it becomes difficult to specify the range of decay or deterioration of wood and the deterioration of the judgment accuracy of wood decay or deterioration.

  In addition, since the conventional technology determines that the moisture content of the wood is abnormally high as decay or deterioration of the wood, even if the wood itself is decayed, if the wood is dry and the moisture content is not high Cannot judge decay or deterioration.

  Then, an object of this invention is to provide the wood inspection method which can pinpoint the degradation part of wood accurately.

  The wood inspection method of the present invention is a wood inspection method using a high-frequency moisture meter, wherein a high-frequency transmission unit and a high-frequency reception unit that are parallel to each other are spaced apart in the fiber direction of the inspected wood, and the high-frequency transmission unit and the high-frequency transmission unit An electromagnetic wave is generated by arranging the length direction of the high-frequency receiving unit to be substantially perpendicular to the fiber direction, and the capacitance of the inspected wood is measured, and the inspected based on the capacitance It is characterized by judging deterioration of wood.

  In the wood inspection method of the present invention, when the capacitance of the wood to be inspected is equal to or higher than a preset upper limit value, the wood to be inspected is determined to be in a high water content and low density state, and the wood to be inspected When the electrostatic capacity is less than or equal to a preset lower limit value, it is determined that the inspected wood is in a low water content and low density state.

  In the wood inspection method of the present invention, the wood to be inspected is a structural frame of a wooden building, and the high-frequency transmission unit and the high-frequency reception unit are arranged along a plate surface of a wall surface, a floor surface, or a ceiling surface. The capacitance of the wood to be inspected arranged on the back side of the plate is measured.

According to the wood inspection method of the present invention, the wood to be inspected is basically long in the fiber direction, so the high-frequency transmitter and the high-frequency receiver are arranged parallel to each other with a distance in the length direction of the wood to be inspected. It will be. At this time, considering the path of the high-frequency electric lines of force, the electric field lines bulge outwardly at the ends of the high-frequency transmitter and the high-frequency receiver, so that the electric lines of force bulge outward. A part of the line of force passes through the outside air beyond the side edge of the wood to be inspected, and an error occurs in the measurement of the capacitance of the wood to be inspected. Even when the position is measured, the width of the wood to be inspected does not change, so the error can be made constant. The lines of electric force bulge in the width direction of the wood to be inspected and do not bulge in the longitudinal direction of the wood to be inspected, so the boundary between the healthy part and the deteriorated part of the wood to be inspected is close. Even when the end of the wood to be inspected is close, the deterioration degree of the wood to be inspected can be determined with high accuracy, and the deteriorated part can be specified with high accuracy.
Further, since the deteriorated portion of the inspected wood is torn due to the decomposition of the fiber of the inspected wood by decaying fungi or the damage caused by white ants, the electromagnetic wave flowing through the fiber is attenuated at the location where the fiber is broken. Therefore, even when the moisture content of the inspected wood is low, it is possible to determine the number of tears in the fibers of the inspected wood, so that deterioration of the inspected wood can be determined.

  According to the wood inspection method of the present invention, not only when the capacitance of the wood to be inspected is not less than a preset upper limit value, but also when the capacitance of the wood to be inspected is not more than a preset lower limit value, Since it is determined that the inspected wood is in a low density state, deterioration of the inspected wood can be determined even when the inspected wood is dry.

  According to the wood inspection method of the present invention, pillars and beams that are the structural frame of a wooden building can be used as inspection object wood, and electromagnetic waves can pass through the wall, floor, or ceiling plate. The deterioration of the inspected wood inside can be determined without removing the plate. Especially in places where water such as column bases is likely to exist and deterioration of the inspected wood is likely to occur, the high-frequency electric lines of force do not swell in the lower end direction, so the degree of deterioration of the inspected wood can be accurately determined. can do.

The figure explaining the state which measures the high frequency electrostatic capacitance of the healthy part of to-be-inspected wood using the wood inspection method of this embodiment. The figure explaining the state which measures the high frequency electrostatic capacitance of the degradation part of to-be-inspected wood using the wood inspection method of this embodiment. The figure explaining the state which measures the high frequency electrostatic capacitance of to-be-inspected wood from the outdoor side or indoor side using the wood test | inspection method of this embodiment. The table | surface which shows the state which judges the deterioration of to-be-inspected wood based on the measurement result of a moisture content. The graph which shows the measurement result of an Example. The graph which shows the measurement result of a comparative example. The figure which shows an example of the inspection method of the conventional timber.

  Hereinafter, an embodiment of a wood inspection method according to the present invention will be described with reference to the drawings. The wood inspection method according to the present embodiment is a method for nondestructively determining the degree of deterioration of the inspected wood 1 such as a column member or a beam member as a structural frame of a wooden building. Note that the wood inspection method of the present invention is not limited to a structural frame of a wooden building, and includes a method for determining the degree of deterioration inside wood as a wood or material used in other structures.

  The high-frequency moisture meter 2 used for inspection includes a high-frequency transmitter 3 that transmits high-frequency electromagnetic waves and a high-frequency receiver 4 that receives the electromagnetic waves, and changes in the dielectric constant (high-frequency capacitance) of the wood 1 to be inspected. And the moisture content of the inspected wood 1 is measured. The high-frequency transmitter 3 and the high-frequency receiver 4 are arranged on the measurement surface of the high-frequency moisture meter 2 in parallel with each other at a predetermined distance. In order to specify the range of the deteriorated part of the inspected wood 1, it is preferable that the distance between the high-frequency transmitting unit 3 and the high-frequency receiving unit 4 is short, but in order to measure the deep position of the inspected wood 1, the high frequency It is advantageous that the distance between the transmitter 3 and the high-frequency receiver 4 is long. The distance between the high frequency transmission part 3 and the high frequency reception part 4 is about 50 mm, for example. Moreover, it is preferable that the length of the high frequency transmission part 3 and the high frequency reception part 4 is shorter than the width of the to-be-inspected wood 1, for example, 100 mm or less. Since the dielectric constant, the high frequency capacitance, and the moisture content are in a directly proportional relationship, the determination of deterioration of the inspected wood 1 to be described later is based on any value of the dielectric constant, the high frequency capacitance, and the moisture content. It may be determined.

  In addition, in consideration of the bulging of the electric field formed between the high-frequency transmitter 3 and the high-frequency receiver 4 to the side of the electric field lines 5, noise and interference from the periphery of the inspected wood 1 are avoided. For this purpose, it is preferable that the high-frequency transmitter 3 and the high-frequency receiver 4 are considerably shorter than the width of the inspected wood 1. It is because the noise etc. by the bulging part of the electric force line 5 passing the air outside the side edge of the to-be-inspected wood 1 can be reduced. Moreover, although the use frequency of the high frequency moisture meter 2 of this embodiment is 20 MHz, it is not limited to this. For example, the operating frequency of the high-frequency moisture meter 2 is 1 MHz to 300 MHz. A high-frequency moisture meter 2 having a frequency suitable for an application for measuring changes in dielectric constant and high-frequency capacitance of the inspected wood 1 can be used.

  The inspected wood 1 is a wood material such as a solid material or a laminated material. In the case of a material in which wood is laminated, the fiber direction D is a material in which the fiber direction D of all laminaes is substantially the long direction. In the present embodiment, the inspected wood 1 is a pillar material. The inspected wood 1 is not limited to the pillar material as described above, and may be other wood such as a beam material.

  In the wood inspection method, first, as shown in FIGS. 1 and 2, the high-frequency transmitter 3 and the high-frequency receiver 4 of the high-frequency moisture meter 2 are respectively disposed on the outside of the grid surface of the inspected wood 1. Arranged so as to be perpendicular to the direction D. In the present embodiment, since the inspected wood 1 is a pillar material standing vertically, the high-frequency transmitter 3 and the high-frequency receiver 4 are arranged so as to be arranged vertically with a distance therebetween. At this time, it is preferable that the high-frequency transmitter 3 and the high-frequency receiver 4 of the high-frequency moisture meter 2 are in direct contact with the surface of the wood 1 to be inspected because noise during measurement can be minimized.

  However, when the inspected wood 1 is contained in the wall, under the floor, behind the ceiling, or behind the shed, the high-frequency transmitter 3 and the plate surface of the wall surface, floor surface, ceiling surface, or roof surface, and A high frequency receiving unit 4 is arranged. Specifically, as shown in FIG. 3, the pillar material as the inspected wood 1 of the present embodiment has a gypsum board 6 stretched over the indoor side to form an inner wall surface. A ventilation layer 7, a wall base plywood 8, and a siding material 9 are laminated on the outdoor side. Therefore, when mainly measuring the indoor side portion of the inspected wood 1, the high frequency transmitting unit 3 and the high frequency receiving unit 4 are brought into contact with a wall cloth attached to the surface of the indoor gypsum board 6. Moreover, when measuring mainly the outdoor side part of the to-be-inspected wood 1, the high frequency transmission part 3 and the high frequency reception part 4 are made to contact the surface of the outdoor side siding material 9. FIG.

  And the high frequency electromagnetic wave is transmitted from the high frequency transmission part 3, and the dielectric constant (high frequency electrostatic capacitance) of the to-be-inspected wood 1 is measured by the high frequency receiving part 4 receiving the said electromagnetic wave. At this time, as shown in FIGS. 1 and 2, the high-frequency electric field lines 5 of the electric field between the high-frequency transmission unit 3 and the high-frequency reception unit 4 are at both ends of the high-frequency transmission unit 3 and the high-frequency reception unit 4. The electric field is disturbed and the electric lines of force 5 bulge outward. Therefore, depending on the width of the wood to be inspected 1, a part of the electric lines of force 5 pass through the outside air beyond the side edge of the wood to be inspected 1. In any measurement position, if the width of the inspected wood 1 is constant, the electric lines of force 5 passing through the outside beyond the side edge of the inspected wood 1 are also constant. The influence on the measurement of the electric capacity is constant, the correction becomes easy, and the judgment accuracy of the healthy part and the deteriorated part of the inspected wood 1 can be increased.

  Moreover, as shown in FIG. 3, when measuring from the indoor side, high frequency electromagnetic waves permeate | transmit the gypsum board 6 and the dielectric constant (high frequency electrostatic capacitance) of the to-be-inspected wood 1 is measured. When measuring from the outdoor side, the dielectric constant (high-frequency capacitance) of the inspected wood 1 is measured through the siding material 9, the wall base plywood 8 and the ventilation layer 7. As described above, the wood inspection method according to the present embodiment measures the degree of deterioration of the inspected wood 1 by measuring the dielectric constant and the high-frequency capacitance using the high-frequency moisture meter 2, so that each surface material is not removed. The deterioration of the inspected wood 1 can be determined.

  In addition, as shown in FIG. 2, in the deteriorated part of the inspected wood 1, the fibers (cell walls) of the inspected wood 1 are torn due to decomposition by decaying fungi or damage by white ants. Therefore, the electromagnetic wave flowing through the fiber is attenuated at the fiber tearing point T. Thereby, even when the moisture content of the wood to be inspected 1 is low, the number of fiber tear locations T of the wood to be inspected 1 can be determined, so that the deterioration of the wood to be inspected 1 can be determined.

  The dielectric constant (high-frequency capacitance) of the inspected wood 1 measured as described above is displayed as a moisture content on a display (not shown) of the high-frequency moisture meter 2. That is, the relationship between moisture and dielectric constant (high-frequency capacitance) is obtained in advance, and the moisture content is calculated by measuring the dielectric constant (high-frequency capacitance) that increases by containing water, and is not shown in the figure. It is shown on the display.

  When the moisture content is thus calculated, the deterioration of the inspected wood 1 is determined based on the moisture content. As shown in FIG. 4, the deterioration of the inspected wood 1 is deteriorated not only when the moisture content is higher than the normal range, but also when the moisture content is lower than the normal range. Is determined. For example, when the moisture content is equal to or higher than a preset upper limit value, it is determined that the fiber density of the inspected wood 1 is in a low density state. Specifically, in the present embodiment, when the moisture content is 18% or more, it is determined that the low density state is a high moisture content. In other words, it can be determined that the moisture content of the structural frame of the waterproofed building is an abnormal state that is not normally considered, and the fibers (cell walls) of the wood 1 to be inspected are caused by decaying fungi when the moisture content is abnormally high. There is a high possibility of being destroyed, or an ant path is formed inside the inspected wood 1 by being eaten by a pest such as a white ant, and also has a high water absorption such as white ant excrement and food waste. It is estimated that the moisture content is abnormally high because the kimono is attached to the ant road. Note that the upper limit value that defines the boundary between normal and abnormal moisture content of the inspected wood 1 is not limited to 18%, but changes depending on factors such as the material of the inspected wood 1 and the location of the inspected wood 1 It is what is done.

  For example, when the moisture content is equal to or lower than a preset lower limit value, it is determined that the fiber density of the inspected wood 1 is in a low density state. Specifically, in this embodiment, when the moisture content is 8% or less, the low density state is determined. That is, when the moisture content is abnormally low, fibers of the inspected wood 1 are destroyed by pests such as decaying fungi and white ants, creating a cavity in the interior, reducing the water retention capacity of the inspected wood 1 and then drying the surroundings. Along with this, the water is evaporated and the water content is estimated to be extremely low. Note that the lower limit value that defines the boundary between normal and abnormal moisture content of the inspected wood 1 is not limited to 8%, but changes depending on factors such as the material of the inspected wood 1 and the location of the inspected wood 1 It is what is done.

  In FIG. 4, the abnormality in which the inspected wood 1 becomes high or low in water content due to decay and the abnormality in which high or low water content due to ant damage are distinguished are described. In addition, ant damage may act in a complex manner, and the density of the inspected wood 1 may decrease. Moreover, as a result of the combined action of decay and ant damage and the density of the wood to be inspected 1 decreased, the water retention capacity of the wood to be inspected 1 may be reduced, and the moisture content may be reduced by subsequent drying. . The wood inspection method of the present embodiment measures the moisture content and discriminates between high moisture content and low moisture content, so that even when the to-be-inspected wood 1 deteriorates due to the combined action of decay and ant damage, The deterioration of the inspection wood 1 can be determined.

  As described above, since the lower limit is set as well as the upper limit of the normal range of the moisture content of the inspected wood 1, the deterioration of the inspected wood 1 is judged. Even if it is the case, degradation of the to-be-inspected wood 1 can be determined.

  In this embodiment, the deterioration of the inspected wood 1 is determined based on the moisture content of the inspected wood 1, but the high-frequency capacitance of the inspected wood 1 or the inspected wood that is directly proportional to the moisture content. The deterioration of the inspected wood 1 may be determined based on the dielectric constant of 1.

〔Example〕
Next, examples and comparative examples of the wood inspection method of the present invention will be described. A todomatsu specimen having a width of 105 mm, a depth of 105 mm, and a length of 250 mm in the fiber direction D and having a deteriorated portion in a range from one end in the length direction to 50 mm, a temperature of 20 ± 2 ° C., and a humidity of 65 ± A material was cured in a constant temperature and humidity room of 5% RH for 3 months or more, and a material with a severe deterioration of the deteriorated part (hereinafter, abrupt deterioration) and a material with a slight deterioration of the deteriorated part (hereinafter, a slight deterioration) were prepared.

  Further, as the high-frequency moisture meter 2, a concrete / mortar moisture meter HI-520-2, manufactured by Ketto Scientific Laboratory Co., Ltd. is used, and the high-frequency capacitance of the above-mentioned specimen is set in the D mode of the high-frequency moisture meter 2. Measured. In addition, D mode is a mode which displays the numerical value of 0 to 1999 which has a correlation with a high frequency capacitance instead of a moisture value. In the measurement, the high-frequency transmission unit 3 and the high-frequency reception unit 4 are arranged so as to be perpendicular to the fiber direction D with an interval in the fiber direction D, and 250 mm to 50 mm that are visually sound portions are measured every 50 mm. In addition, 0 mm to 50 mm, which is a visually deteriorated portion, was measured. The above measurement was carried out on a specimen with severe deterioration and a specimen with slight deterioration. As a result of the measurement, the value indicating the displayed high-frequency capacitance is as shown in FIG.

[Comparative example]
In addition, using the same severely deteriorated specimen and the slightly deteriorated specimen as in the example, in the D mode of the same high-frequency moisture meter 2 as in the example, the gap is spaced in the direction orthogonal to the fiber direction D. The high frequency transmission unit 3 and the high frequency reception unit 4 were arranged in parallel to the fiber direction D, and 250 mm to 0 mm were measured every 50 mm. As a result of the measurement, the value indicating the displayed high-frequency capacitance is as shown in FIG.

  First, the results of the slightly deteriorated specimen are examined. In both Examples and Comparative Examples, the value of the slightly deteriorated specimen hardly changes in capacitance between the healthy part and the deteriorated part. However, in the comparative example shown in FIG. 6, the capacitance slightly decreases in the range of 200 mm to 250 mm and 0 mm to 50 mm of the slightly deteriorated specimen. In the method of the comparative example, for example, when measuring the vicinity of the end as shown in FIG. 7B, the side end of the electric field lines 5 of the electric field swells, and some of the lines of electric force 5 are generated. Since it passes through the outside of the specimen, the dielectric constant of that portion is lowered, the apparent capacitance and moisture content are lowered, and it can be seen that it is a noise for judging deterioration. .

  Next, the result of the specimen with severe deterioration will be examined. The capacitance of the specimen with severe deterioration in the example hardly shows a decrease in the healthy part, but clearly decreases in the deteriorated part. On the other hand, the electrostatic capacity of the specimen with severe deterioration of the comparative example is slightly reduced in the healthy part of 50 mm to 100 mm, and further lowered in the deteriorated part of 0 mm to 50 mm. Thus, in the example, the boundary between the healthy part and the deteriorated part is clear and the deterioration range can be specified, whereas in the comparative example, the boundary between the healthy part and the deteriorated part becomes ambiguous and the deterioration range Cannot be specified sufficiently. As shown in FIG. 7A, in the comparative example, when measuring the healthy part near the deteriorated part, the side part of the electric force lines 5 of the electric field swells and some of the electric lines of force 5 deteriorate. Since the dielectric constant of the portion is lowered, the apparent capacitance and the moisture content are lowered, and it is a noise when specifying the deteriorated portion. Recognize.

  As described above, according to the wood inspection method of the present invention, it is possible to increase the accuracy of judgment between a healthy part and a deteriorated part, and in both cases where the moisture content of the inspected wood 1 is high and low. Deterioration judgment of the inspected wood 1 can be performed.

  It goes without saying that the embodiment of the present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the scope of the idea of the present invention.

  The wood inspection method according to the present invention is suitable, for example, as a non-destructive inspection method for a structural frame of a wooden building.

1 Wood to be inspected 2 High-frequency moisture meter 3 High-frequency transmitter 4 High-frequency receiver 6 Gypsum board (plate)
9 Siding board
D Fiber direction

Claims (3)

A wood inspection method using a high-frequency moisture meter,
A high-frequency transmission unit and a high-frequency reception unit that are parallel to each other are spaced apart in the fiber direction of the wood to be inspected, and are arranged so that the length directions of the high-frequency transmission unit and the high-frequency reception unit are substantially perpendicular to the fiber direction. To generate electromagnetic waves and measure the capacitance of the inspected wood,
A wood inspection method, wherein deterioration of the inspection wood is determined based on the capacitance. When the capacitance of the wood to be inspected is equal to or higher than a preset upper limit value, the wood to be inspected is determined to be in a high water content and low density state,
The wood inspection method according to claim 1, wherein when the capacitance of the wood to be inspected is equal to or less than a preset lower limit value, the wood to be inspected is determined to be in a low water content and low density state. . The inspected wood is a structural frame of a wooden building,
The high-frequency transmitter and the high-frequency receiver are arranged along the plate surface of the wall surface, floor surface, ceiling surface, or roof surface, and the capacitance of the inspected wood arranged on the back side of the plate body is measured. The wood inspection method according to claim 1, wherein the wood inspection method is performed.

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