CN111521684A - Wood bending strength field detection method - Google Patents
Wood bending strength field detection method Download PDFInfo
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- CN111521684A CN111521684A CN202010245040.8A CN202010245040A CN111521684A CN 111521684 A CN111521684 A CN 111521684A CN 202010245040 A CN202010245040 A CN 202010245040A CN 111521684 A CN111521684 A CN 111521684A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/04—Analysing solids
- G01N29/07—Analysing solids by measuring propagation velocity or propagation time of acoustic waves
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
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- Investigating Strength Of Materials By Application Of Mechanical Stress (AREA)
- Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)
Abstract
The invention discloses a field detection method for bending strength of wood, which comprises the following steps: 1. avoiding wood defects, and determining a set number of measuring points on the surface of the wood member to be measured according to every two measuring points as a group along the wood grain direction, wherein the distance L between every two adjacent measuring points of each group is not less than 500 mm; 2. drilling an inclined hole with the inclination of 20-30 degrees at each measuring point relative to the connecting line of each group of two measuring points, wherein the hole diameter is 6-8 mm, and the hole depth is 6-8 mm; the inclined holes at the two measuring points of each group are oppositely arranged; 3. placing an ultrasonic wood detector probe in the drill hole of each group of two measuring points for testing, and recording the ultrasonic sound time t; 4. testing each group of two measuring point connecting lines by adopting an impedance meter, wherein the drilling depth is not less than 30mm, and determining the mean value of an impedance curve in the drilling depth; 5. aFv when f is equal to2+ b, calculating the bending strength of the wood, wherein F is the bending strength of the wood, F and v are respectively an impedance curve mean value and an ultrasonic wave velocity mean value, and a and b are regression coefficients; wherein: and v is L/t.
Description
Technical Field
The invention relates to the technical field of civil engineering, in particular to a field detection method for bending strength of wood of new and existing wood structures.
Background
The wood is used as a low-carbon, environment-friendly and renewable building material and is widely applied to industrial and civil buildings and bridge structures, and meanwhile, the buildings and the bridges are also influenced by load, environmental temperature and humidity change, biological erosion and the like in a service period, so that damage of different degrees is generated; and therefore their safety needs to be assessed accordingly.
The determination of the wood strength grade has an important influence on the safety evaluation of the wood structure. At present, the wood strength grade is mainly determined according to the test result of the bending strength of a sample cleaning small test piece. The conventional sample cleaning small test piece testing method usually significantly weakens the section size of the wood member and causes serious damage, so that it is difficult to widely use in excellent historical protection buildings. In view of the above, a new technical measure is needed to realize an efficient nondestructive/micro-damage method for detecting the bending strength of wood.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a field detection method for the bending strength of the wood, which can obviously reduce the error caused by unstable excitation in the traditional stress wave detection technology, has small damage to the wood members and can obviously reduce the detection time of a single wood member.
The technical problem to be solved can be implemented by the following technical scheme.
A field detection method for bending strength of wood is characterized by comprising the following steps:
(1) the method comprises the following steps of avoiding wood defects, determining a set number of measuring points on the surface of a wood member to be detected according to every two measuring points as a group along the wood grain direction, wherein the distance L between every two adjacent measuring points of each group is not less than 500 mm;
(2) drilling a hole at each measuring point relative to a connecting line of each group of two measuring points, and drilling an inclined hole with the inclination of 20-30 degrees, wherein the hole diameter of the inclined hole is 6-8 mm, and the hole depth is 6-8 mm; the inclined holes at the two measuring points of each group are oppositely arranged;
(3) placing an ultrasonic wood detector probe in the drill holes of each group of two measuring points for testing, and recording the sound time t of ultrasonic waves;
(4) testing the connecting line of each group of two measuring points by adopting an impedance meter, wherein the drilling depth is not less than 30mm, and then determining the mean value of an impedance curve in the drilling depth;
(5) and calculating the bending strength of the wood according to the following formula:
f＝aFv2+b
wherein F is the bending strength (MPa) of the wood, F and v are respectively the mean value of an impedance curve (Resi) and the mean value of the ultrasonic wave velocity (km/s), and a and b are regression coefficients; wherein: and v is L/t.
In a preferred form of the present invention, when the wooden member is douglas fir, in the step (5), a is 0.003 and b is 35.4.
As a further improvement of the invention, the number of times of ultrasonic detection and impedance meter detection of each wood member is not less than 3.
As a further improvement of the technical scheme, the inclined hole is formed by drilling through a miniature electric drill.
In a preferred form of the invention, the inclination of the bore is preferably 25 °.
Compared with the prior art, the invention has the following beneficial effects:
the invention can obviously reduce the error caused by unstable excitation in the traditional stress wave detection technology. And the ultrasonic detection result is corrected according to the impedance curve average value, so that the detection precision of the ultrasonic detector can be obviously improved. In addition, the invention has little damage to the wood member, is very convenient to operate, can obviously reduce the detection time of a single wood member, and has good application prospect.
Drawings
FIG. 1 is a schematic view of ultrasonic testing in the method for testing bending strength of wood according to the present invention;
FIG. 2 is a schematic diagram of the resistance drilling method in the method for detecting bending strength of wood according to the present invention;
Detailed Description
The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.
The present embodiment is only for explaining the present invention, and it is not limited to the invention, and those skilled in the art can make modifications without inventive contribution to the present embodiment as needed after reading the present specification, but should be protected by patent laws within the scope of the claims of the present invention.
The invention relates to the field of civil engineering, in particular to a new and existing wood structure, and provides a field detection method for bending strength of wood with reference to fig. 1 and 2. The method comprises the following specific steps:
the embodiment provides a field micro-damage detection method for the bending strength of douglas fir, and particularly comprises an ultrasonic wood detector 1, miniature electric drills 21 and 22, an impedance meter 3 and a test wood member 4.
Every two measuring points are taken as a group, the ultrasonic probe measuring points 210 and 220 are determined on the surface of the cross grain of the douglas fir component, the distance L between every two adjacent measuring points is not less than 500mm (the positions between the two measuring points are selected to be free of wood defects such as decay, knots, twill, pith, cracks, worm damage and the like), and the measuring points are in a straight line along the wood grain direction (the direction of an arrow A in the figure).
And (3) drilling holes on the surfaces of the two measuring points by using miniature electric drills 21 and 22 in a direction of 20-30 degrees (which can be understood as a connecting line between the two points), wherein the diameter of the drilled hole is preferably 6-8 mm, and the depth of the drilled hole is preferably 6-8 mm. As shown in fig. 1, the two inclined holes are oppositely arranged.
And placing ultrasonic wood detector probes in the drill holes of two adjacent measuring points for testing, and recording the sound time t of ultrasonic waves.
The impedance meter 3 is used for testing near the measuring point (here, on a connecting line between two measuring points), the drilling depth is not smaller than 30mm, and then the average value of the impedance curve in the drilling depth is determined. The number of times of ultrasonic detection and impedance meter detection of each Douglas fir component is not less than 3.
The bending strength of the wood corresponding to the test result of the sample cleaning small test piece can be determined according to a linear regression equation of the product of the mean value of the impedance curve and the square of the mean value of the ultrasonic wave velocity (v ═ L/t), and the expression is
f＝aFv2+b (1)
In the formula, F is the bending strength of the wood, F and v are the mean value of the impedance curve and the mean value of the ultrasonic wave speed respectively, and a and b are regression coefficients.
Wherein when the member is Douglas fir, its expression is
f＝0.003Fv2+35.4 (2)
Wherein F is the flexural strength (MPa) of Douglas fir, and F and v are the mean value of the impedance curve (Resi) and the mean value of the ultrasonic wave velocity (km/s), respectively.
Claims (5)
1. The field detection method for the bending strength of the wood is characterized by comprising the following steps:
(1) the method comprises the following steps of avoiding wood defects, determining a set number of measuring points on the surface of a wood member to be detected according to every two measuring points as a group along the wood grain direction, wherein the distance L between every two adjacent measuring points of each group is not less than 500 mm;
(2) drilling a hole at each measuring point relative to a connecting line of each group of two measuring points, and drilling an inclined hole with the inclination of 20-30 degrees, wherein the hole diameter of the inclined hole is 6-8 mm, and the hole depth is 6-8 mm; the inclined holes at the two measuring points of each group are oppositely arranged;
(3) placing an ultrasonic wood detector probe in the drill holes of each group of two measuring points for testing, and recording the sound time t of ultrasonic waves;
(4) testing the connecting line of each group of two measuring points by adopting an impedance meter, wherein the drilling depth is not less than 30mm, and then determining the mean value of an impedance curve in the drilling depth;
(5) and calculating the bending strength of the wood according to the following formula:
f＝aFv2+b
wherein F is the bending strength (MPa) of the wood, F and v are respectively the mean value of an impedance curve (Resi) and the mean value of the ultrasonic wave velocity (km/s), and a and b are regression coefficients; wherein: and v is L/t.
2. The field detection method for the bending strength of the wood according to claim 1, wherein in the step (5), the value of a is 0.003, and the value of b is 35.4.
3. The field test method for bending strength of wood according to claim 1, wherein the number of times of ultrasonic testing and impedance meter testing for each wood member is not less than 3.
4. The field test method for the bending strength of the wood according to claim 1, wherein the inclined hole is drilled by a miniature electric drill.
5. The method of claim 1, wherein the inclination of the drilled hole is 25 °.
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| CN202010245040.8A CN111521684A (en) | 2020-03-31 | 2020-03-31 | Wood bending strength field detection method |
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| CN202010245040.8A CN111521684A (en) | 2020-03-31 | 2020-03-31 | Wood bending strength field detection method |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114384150A (en) * | 2020-10-06 | 2022-04-22 | 丰田自动车株式会社 | Measurement system, airborne mobile device, and measurement method |
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| CN110726584A (en) * | 2019-11-26 | 2020-01-24 | 上海市建筑科学研究院有限公司 | On-site micro-damage sampling detection method for tree species identification |
| CN110726586A (en) * | 2019-11-26 | 2020-01-24 | 上海市建筑科学研究院有限公司 | On-site micro-damage sampling detection method for wood strength |
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| CN110726584A (en) * | 2019-11-26 | 2020-01-24 | 上海市建筑科学研究院有限公司 | On-site micro-damage sampling detection method for tree species identification |
| CN110726586A (en) * | 2019-11-26 | 2020-01-24 | 上海市建筑科学研究院有限公司 | On-site micro-damage sampling detection method for wood strength |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114384150A (en) * | 2020-10-06 | 2022-04-22 | 丰田自动车株式会社 | Measurement system, airborne mobile device, and measurement method |
| CN114384150B (en) * | 2020-10-06 | 2024-04-09 | 丰田自动车株式会社 | Measurement system, air mobile device and measurement method |
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