CN116263427A - Nondestructive testing method for steel fiber orientation - Google Patents
Nondestructive testing method for steel fiber orientation Download PDFInfo
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- CN116263427A CN116263427A CN202211594308.4A CN202211594308A CN116263427A CN 116263427 A CN116263427 A CN 116263427A CN 202211594308 A CN202211594308 A CN 202211594308A CN 116263427 A CN116263427 A CN 116263427A
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Abstract
本发明涉及一种钢纤维朝向的无损检测方法，将PCB线圈与电感传感器连接，将电感传感器与单片机连接，单片机与上位机连接；标定PCB线圈电感初始值L0；对所检测的钢纤维混凝土结构进行区块划分；将PCB线圈静置于不同检测区块，PCB线圈贴近钢纤维混凝土表面，在同一区块，每隔一定角度，旋转一次PCB线圈，待电感值无明显波动时，记录所测数据；PC上位机读取PCB线圈电感信号并记录，并与电感初始值L0作差，得到电感变化值，比较不同区块所测电感值，绘制电感信号图，通过识别电感值变化最大的方向来判断钢纤维的优先朝向。本发明将电磁感应原理应用到钢纤维混凝土结构钢纤维朝向的无损识别中，能够很好的对钢纤维混凝土构件质量进行控制。
The invention relates to a nondestructive detection method of steel fiber orientation, which comprises connecting a PCB coil with an inductance sensor, connecting the inductance sensor with a single-chip microcomputer, and connecting the single-chip microcomputer with a host computer; calibrating the initial value L0 of the inductance of the PCB coil; The structure is divided into blocks; the PCB coil is placed statically in different detection blocks, and the PCB coil is close to the surface of the steel fiber concrete. In the same block, rotate the PCB coil once at a certain angle. When there is no obvious fluctuation in the inductance value, record the Measured data; the PC host computer reads the inductance signal of the PCB coil and records it, and makes a difference with the initial value of the inductance L 0 to obtain the inductance change value, compare the inductance values measured in different blocks, draw the inductance signal map, and identify the largest change in the inductance value to judge the preferential orientation of steel fibers. The invention applies the principle of electromagnetic induction to the non-destructive identification of the steel fiber orientation of the steel fiber concrete structure, and can well control the quality of the steel fiber concrete components.
Description
Technical Field
The invention belongs to the field of steel fiber reinforced concrete detection, and particularly relates to a nondestructive detection method for steel fiber orientation.
Background
Steel Fiber Reinforced Concrete (SFRC) is a widely used building material in modern civil and construction engineering. When the steel fiber is added into the concrete matrix, the development of concrete cracks of the matrix can be blocked, and compared with common concrete, the mechanical properties of the concrete matrix are obviously improved. The mechanical properties of steel fiber concrete depend not only on the fiber content, but also on the direction of the steel fibers in the concrete relative to the direction of the applied stress. Measuring these parameters, in particular in situ measurements, is therefore one of the most important targets.
The current methods applied to steel fiber concrete detection can be divided into destructive detection and nondestructive detection. The most common method of destructive testing to obtain fiber content is to crush the sample and then manually count/weigh the fibers therein. The fiber direction is then evaluated by counting the number of fibers of the broken/cut surface in different directions. However, any destructive method is difficult to apply to quality control of in-situ steel fiber concrete products. Nondestructive testing methods also suffer from problems such as the difficulty of using x-ray methods on a job site due to their high cost. The resistance method is also greatly affected by the difference in contact surface conditions. With the development of electronic equipment and digital processing technology, some nondestructive testing methods based on the electrical characteristics of steel fiber concrete are to be applied to quality control of steel fiber concrete.
In order to obtain better mechanical properties of the steel fiber concrete, fiber orientation is performed by a method of applying an externally applied magnetic field. Forcing the fibers to orient along the direction of the prevailing tensile stress within the structural member will result in an effective increase in the structural use efficiency of the material. The method enables the steel fiber concrete structure to cover longer spans, achieves higher bearing capacity (or even greater lateral load resistance in the earthquake-resistant structure) with reduced cross-sectional dimensions, and also reduces the structural burden of self-bearing. Therefore, for directional steel fiber concrete, the quality control of the internal steel fiber orientation is important.
At present, a method for simply and rapidly judging the orientation of steel fibers in concrete is not available.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a nondestructive testing method based on the orientation of steel fibers of an electromagnetic induction steel fiber concrete structure. The values of the inductances measured in all directions are compared, so that the preferential direction of the fibers in the steel fiber concrete is judged, and the quality control of the steel fiber concrete is realized.
The technical scheme adopted for solving the technical problems is as follows:
a nondestructive testing method for steel fiber orientation comprises connecting PCB coil with inductance sensor, and connectingThe inductance sensor is connected with the singlechip, and the singlechip is connected with the upper computer; calibrating initial value L of inductance of PCB coil 0 The method comprises the steps of carrying out a first treatment on the surface of the Dividing the detected steel fiber reinforced concrete structure into blocks; the PCB coils are placed in different detection blocks in a static mode, the PCB coils are close to the surface of the steel fiber concrete, the PCB coils are rotated once at certain angles in the same block, and the detected data are recorded when the inductance value does not obviously fluctuate; the upper computer reads and records the inductance signal of the PCB coil and compares the inductance signal with an inductance initial value L 0 And (3) taking difference to obtain inductance variation values, comparing the inductance values measured by different blocks, drawing an inductance signal diagram, and judging the preferential orientation of the steel fiber by identifying the direction with the largest inductance value variation.
Further, the PCB coil is rectangular.
Further, the size and the excitation frequency of the PCB coil are selected according to the field detection object.
Further, the PCB coil is rotated every 10 to 30 degrees.
Further, the PCB coil is placed at a place far away from the metal substance to perform an inductance initial value L 0 Is defined by the calibration of (a).
The invention has the advantages and positive effects that:
the invention applies the electromagnetic induction principle to the nondestructive identification of the steel fiber direction of the steel fiber concrete structure, can well control the quality of the steel fiber concrete member, is a nondestructive detection method, has the characteristics of convenience and rapidness, and overcomes the economic waste caused by the traditional broken detection.
Drawings
FIG. 1 is a schematic diagram of the vortex operation;
FIG. 2 is a schematic diagram of a test apparatus;
FIG. 3 is a diagram of an LC resonance circuit;
FIG. 4 is a schematic view of steel fiber concrete orientation detection;
FIG. 5 is a schematic diagram of an inductance signal;
fig. 6 is a schematic diagram of a PCB rectangular coil.
Detailed Description
The invention will be described in detail below with reference to the drawings in connection with embodiments. It is noted that all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs unless otherwise indicated.
As shown in fig. 1, pulsed eddy currents will generate an ac magnetic field for ac current flowing through the PCB coil (inductor). If a conductive material, such as a metal object, is brought into the vicinity of the coil, this magnetic field will induce eddy currents at the surface of the object. These eddy currents produce a magnetic field that is opposite to the original magnetic field produced by the primary coil. Thereby affecting the resistance and inductance of the primary coil.
Inductance sensor theory of operation: the PCB rectangular coil is connected with the inductance digital sensor through a lead to form a complete monitoring circuit. Inductive sensors implement inductive sensing by measuring inductance and impedance of the LC network. The inside of the sensor comprises a monolithic integrated inductance sensing chip, and only one external inductance and one resonant capacitor are needed to form a resonant circuit to work.
Fig. 3 is a diagram of an LC resonance circuit, L representing the inductance of the PCB coil, rs being the equivalent series resistance of the inductance, C being the external resonance capacitance. The inductance sensor has a high frequency oscillator inside, which continuously outputs a scan signal, and when the external LC network resonates, the impedance of the LC resonant circuit is at a maximum value, and the voltage at the output pin reaches a maximum value. By keeping the output pins at a certain maximum voltage, the LC network remains resonant at all times. When the parallel circuit resonates, its resonant frequency is about:
at resonance, the internal timer counter of the inductive sensor completes the resonance frequency f 0 The inductance L to be measured can be calculated by measuring and knowing the capacitance C. When the PCB rectangular coil rotates along the center point, the long side direction of the PCB rectangular coil is opposite to the steelThe included angle of the fibers changes, and the inductance of the rectangular coil of the PCB is measured to change. When the long side direction of the rectangular coil is consistent with the preferential direction of the steel fiber, the inductance change is the largest. Because the rectangular PCB coil is in a uniaxially symmetric pattern, the inductance signal schematic diagram is also in a uniaxially symmetric pattern.
Because the detection ranges of the PCB rectangular coils with different sizes are different, the detection distance and the detection area are increased along with the increase of the coil size. For steel fiber concrete structures with different thicknesses, the size of the PCB coil can be designed by itself so as to meet the actual requirements of engineering.
As shown in fig. 2, the selected PCB coil is connected to an inductance sensor through a wire, the inductance sensor is connected to a single chip microcomputer through an AD interface, the single chip microcomputer controls the inductance sensor to operate to obtain an inductance L, and the measured inductance value is sent to an upper computer for display through serial communication to obtain an L-t relation curve.
As shown in fig. 4, the steel fiber concrete is divided into areas according to the detection range of the PCB coil, the areas of the areas corresponding to the different PCB coils are different, and the larger the size of the PCB coil is, the larger the area of the corresponding divided area is, as shown in fig. 4. And (3) the PCB rectangular coil is pressed close to the surface of the steel fiber concrete, rotates once every 15 degrees, stands for a period of time, and calculates an average value of 500 data points after the inductance fluctuation range is smaller than 5% when the inductance value measured by the PC end does not obviously fluctuate, so that the final inductance value is obtained, namely, one detection is completed, and each area is detected for one circle.
And reading and recording the inductance signals of the PCB coil through upper computer software, comparing the inductance values measured in different areas, and processing the data to finish drawing an inductance signal diagram, as shown in fig. 5. And judging the preferential direction of the steel fiber by identifying the direction in which the inductance value changes the most.
Taking the steel fiber concrete slab of fig. 4 as an example: the size of the concrete cover plate is 500mm multiplied by 300mm multiplied by 30mm, the area of the divided area is 100mm multiplied by 100mm, 15 areas are provided, and each area PCB coil is measured once every 15 degrees of rotation around the center point, and one circle of measurement is performed.
The inductance change value of the steel fiber concrete in each area is as follows:
ΔL θ ＝L 0 -L θ
L 0 -inductance value of PCB rectangular coil placed in air
L θ -inductance value of the coil when the long side direction of the rectangular coil of the PCB is at an angle θ ° to the x-axis
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (5)
1. A nondestructive testing method for the orientation of steel fibers is characterized in that,
connecting the PCB coil with the inductance sensor, connecting the inductance sensor with the singlechip, and connecting the singlechip with the upper computer;
calibrating initial value L of inductance of PCB coil 0 ；
Dividing the detected steel fiber reinforced concrete structure into blocks;
the PCB coils are placed in different detection blocks in a static mode, the PCB coils are close to the surface of the steel fiber concrete, the PCB coils are rotated once at certain angles in the same block, and the detected data are recorded when the inductance value does not obviously fluctuate;
the upper computer reads and records the inductance signal of the PCB coil and compares the inductance signal with an inductance initial value L 0 And (3) taking difference to obtain inductance variation values, comparing the inductance values measured by different blocks, drawing an inductance signal diagram, and judging the preferential orientation of the steel fiber by identifying the direction with the largest inductance value variation.
2. The method of claim 1, wherein the PCB coil is rectangular.
3. The nondestructive testing method of steel fiber orientation according to claim 2, wherein the suitable PCB coil size, shape, excitation frequency are selected based on the field test object.
4. A nondestructive testing method for steel fiber orientation according to claim 3 wherein the PCB coil is rotated every 10-30 °.
5. The nondestructive inspection method for steel fiber orientation according to claim 4, wherein the calibration of the initial value L0 of the inductance is performed by placing the PCB coil at a position far from the metal substance.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211594308.4A CN116263427A (en) | 2022-12-13 | 2022-12-13 | Nondestructive testing method for steel fiber orientation |
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| CN202211594308.4A CN116263427A (en) | 2022-12-13 | 2022-12-13 | Nondestructive testing method for steel fiber orientation |
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| CN116263427A true CN116263427A (en) | 2023-06-16 |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN118937408A (en) * | 2024-07-23 | 2024-11-12 | 国网山东省电力公司物资公司 | High detection accuracy nondestructive testing method and related device for concrete poles |
| CN120334341A (en) * | 2025-06-12 | 2025-07-18 | 河北工业大学 | A detection device and method for steel fiber content and orientation in steel fiber concrete |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| ES107609A1 (en) * | 1928-05-14 | 1928-07-01 | Guerenu Aizpurua Eusebio | A system of heating and heating the water for the bathroom simultaneously or independently of that, with an economic kitchen. |
| CN113109393A (en) * | 2021-04-29 | 2021-07-13 | 太原理工大学 | Device and method for nondestructive testing of steel fiber content and distribution in steel fiber concrete |
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2022
- 2022-12-13 CN CN202211594308.4A patent/CN116263427A/en active Pending
Patent Citations (2)
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| ES107609A1 (en) * | 1928-05-14 | 1928-07-01 | Guerenu Aizpurua Eusebio | A system of heating and heating the water for the bathroom simultaneously or independently of that, with an economic kitchen. |
| CN113109393A (en) * | 2021-04-29 | 2021-07-13 | 太原理工大学 | Device and method for nondestructive testing of steel fiber content and distribution in steel fiber concrete |
Non-Patent Citations (1)
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| 宋贺月 等: "钢纤维在混凝土基体中空间分布的研究方法评述", 《材料科学与工程学报》, vol. 33, no. 5, 20 October 2015 (2015-10-20), pages 768 - 775 * |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN118937408A (en) * | 2024-07-23 | 2024-11-12 | 国网山东省电力公司物资公司 | High detection accuracy nondestructive testing method and related device for concrete poles |
| CN118937408B (en) * | 2024-07-23 | 2025-06-03 | 国网山东省电力公司物资公司 | High detection accuracy nondestructive testing method and related device for concrete poles |
| CN120334341A (en) * | 2025-06-12 | 2025-07-18 | 河北工业大学 | A detection device and method for steel fiber content and orientation in steel fiber concrete |
| CN120334341B (en) * | 2025-06-12 | 2025-09-09 | 河北工业大学 | A device and method for detecting steel fiber content and orientation in steel fiber concrete |
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