阅读说明：本技术 一种非接触式桥梁腐蚀钢筋磁感应检测方法 (Non-contact type bridge corrosion steel bar magnetic induction detection method ) 是由 熊劲松 陈川 胥俊 张九林 张波 于 2019-11-14 设计创作，主要内容包括：本发明涉及一种非接触式桥梁腐蚀钢筋磁感应检测方法,属于桥梁检测领域。该方法包括以下步骤：1)涡流效应电磁参数的获取；2)磁场在空气中的传播的确定；3)数据传输与信号分析处理。本发明中,激励信号为具有一定占空比低频的脉冲方波,这种低频脉冲信号包含频率的信息量丰富、频谱宽、信号穿透力强；传统涡流检测传感器近场距离下,相比而言,脉冲涡流检测传感器具有更大的近场区域,就算传感器的提离高度比较大,依然在检测信号覆盖范围内。(The invention relates to a non-contact type bridge corrosion steel bar magnetic induction detection method, and belongs to the field of bridge detection. The method comprises the following steps: 1) acquiring eddy current effect electromagnetic parameters; 2) determination of the propagation of the magnetic field in air; 3) and data transmission and signal analysis processing. In the invention, the excitation signal is a pulse square wave with a certain duty ratio and low frequency, and the low-frequency pulse signal has rich information content of frequency, wide frequency spectrum and strong signal penetrating power; under the near-field distance of the traditional eddy current detection sensor, compared with the pulse eddy current detection sensor, the pulse eddy current detection sensor has a larger near-field area, and even if the lift-off height of the sensor is larger, the pulse eddy current detection sensor still remains in the coverage range of detection signals.)

1. A non-contact type bridge corrosion steel bar magnetic induction detection method is characterized by comprising the following steps: the method comprises the following steps:

1) acquiring eddy current effect electromagnetic parameters;

2) determination of the propagation of the magnetic field in air;

3) and data transmission and signal analysis processing.

2. The non-contact magnetic induction detection method for the corroded steel bar of the bridge as recited in claim 1, which is characterized in that: the step 1) is specifically as follows:

when an excitation signal generated by an excitation source is applied to two ends of an excitation coil L1, magnetic lines generated by an L1 inevitably cut the detected corrosion steel bar M and generate an eddy current i, and the eddy current consumes part of magnetic field energy, so that the magnetic lines reaching the L2 are reduced, and f is reduced; the larger the thickness A of M is, the larger the eddy current loss is, and the smaller the induced electromotive force E of the detection coil is; the size of E indirectly reflects the size of M, when the steel bar is corroded, the diameter of the steel bar is inevitably reduced, and the judgment on the corrosion degree of the steel bar is finished through the size judgment of E;

the relationship between E and h is represented by the following formula

E＝KUe^-d/h

Wherein d is the thickness of the corrosion steel bar; h is the vortex penetration depth; k is a proportionality constant.

3. The non-contact type magnetic induction detection method for the corroded steel bar of the bridge as recited in claim 2, which is characterized in that: the step 2) is specifically as follows:

in an infinite passive space; is filled with linear and isotropic uniform ideal media; a time-harmonic field; a uniform plane wave;

if a uniform plane wave is transmitted along the z-axis and the equiphase plane is the xy-plane, the electromagnetic intensity and the magnetic field intensity are not functions of x and y, that is

Due to the fact that

In the same way

Obtaining that the electric field intensity and the magnetic field intensity of the uniform plane wave are perpendicular to the propagation direction of the wave;

at this time

Provided that the electric field has only an x-component, i.e.

Solution to E_x(z)＝A₁e^-jkz+A₂e^jkz

First item

Second item

By

Wherein

In the same way, for

In an ideal medium, the electric field strength and the magnetic field strength of a uniform plane wave are perpendicular to each other and in phase.

4. The non-contact type magnetic induction detection method for the corroded steel bar of the bridge as recited in claim 3, which is characterized in that: the step 3) is specifically as follows:

the lower computer sends the collected data and the data analysis processing to the upper computer, and the upper computer background software realizes data recording; analyzing the data through Hilbert transform;

any one of the time sequences g (t) is changed into by Hilbert transform

In the formula, P is a Cauchy main value and takes the value of 1; hilbert transform of signal g (t)

the original signal amplitude and frequency are unchanged through Hilbert transform, and the phase is shifted by 90 degrees; and generating an analytic signal and analyzing the corrosion degree of the steel bars in the reinforced concrete.

Technical Field

The invention belongs to the field of bridge detection, and relates to a non-contact type bridge corrosion steel bar magnetic induction detection method.

Background

The methods for detecting the corrosion condition of the steel bar and the concrete reinforcement protection parameters can be divided into two main types of physics and electrochemistry, and the physical methods comprise appearance inspection, weighing, a resistance probe, acoustic emission, an expansion strain probe and the like. The principle of the resistance probe for detecting the corrosion of the steel bar is that the change quantity of the resistance value of the probe is measured by utilizing the characteristics that the length of the resistance probe is unchanged, the sectional area is uniformly reduced, and the resistance value is increased along with the change quantity, so that the diameter change quantity of the probe is calculated, and the corrosion depth is obtained. Acoustic emission is a physical phenomenon in which energy is rapidly released inside an object or material to generate transient elastic waves. Elastic waves generated by different signal sources can be distinguished, and the acquisition of acoustic emission signals can reflect the relevant characteristics of an acoustic emission source to a certain extent. And (3) corresponding the property of the acoustic emission source with a specific phenomenon, and analyzing the characteristics of the acquired acoustic emission signal so as to judge and evaluate the real-time state of the detected body. The optical fiber detection is based on the principle that photons propagate in the glass or organic fiber along the length direction, and when the strain, temperature and the like of the glass or fiber are changed, the physical properties (wavelength, frequency, polarization state, phase and the like) of light are changed along with the change of the strain, temperature and the like of the glass or fiber, so that the corrosion detection is carried out. The electrochemical detection is to calculate the corrosion rate or corrosion degree of the steel bar by measuring the electrochemical characteristic change (such as potential) of the electrolyte solution system of the reinforced concrete, and the common methods include a linear polarization method, an alternating current impedance spectroscopy method, a natural potential method and the like.

The physical detection method has the problems that the method can only be used for qualitative analysis of corrosion detection, is mainly used in a laboratory test stage, and has larger errors in actual engineering corrosion measurement. The electrochemical detection method has the advantages that due to the fact that signals need to be injected in the measuring process, on one hand, the bridge can be damaged to a certain degree, and on the other hand, under certain working conditions, the signals cannot be injected into the corrosion reinforcing steel bars. The invention aims to provide a non-contact type magnetic induction detection method for bridge corrosion reinforcing steel bars, which does not need to contact the surface of a bridge or a coupling agent, adopts a non-contact magnetic induction mode, and judges the corrosion degree of the reinforcing steel bars in bridge reinforced concrete by analyzing and processing signals collected by a detection coil.

Disclosure of Invention

In view of the above, the present invention provides a non-contact magnetic induction detection method for bridge corrosion steel bars, which adjusts the signal output of an excitation source to an excitation coil by using a non-contact magnetic induction method, and performs signal analysis and processing through the detection of a detection coil, so as to determine the corrosion degree of steel bars in bridge reinforced concrete.

In order to achieve the purpose, the invention provides the following technical scheme:

a non-contact type bridge corrosion steel bar magnetic induction detection method comprises the following steps:

1) acquiring eddy current effect electromagnetic parameters;

2) determination of the propagation of the magnetic field in air;

3) and data transmission and signal analysis processing.

Optionally, the step 1) specifically includes:

when an excitation signal generated by an excitation source is applied to two ends of an excitation coil L1, magnetic lines generated by an L1 inevitably cut the detected corrosion steel bar M and generate an eddy current i, and the eddy current consumes part of magnetic field energy, so that the magnetic lines reaching the L2 are reduced, and f is reduced; the larger the thickness A of M is, the larger the eddy current loss is, and the smaller the induced electromotive force E of the detection coil is; the size of E indirectly reflects the size of M, when the steel bar is corroded, the diameter of the steel bar is inevitably reduced, and the judgment on the corrosion degree of the steel bar is finished through the size judgment of E;

the relationship between E and h is represented by the following formula

E＝KUe^-d/h

Wherein d is the thickness of the corrosion steel bar; h is the vortex penetration depth; k is a proportionality constant.

Optionally, the step 2) specifically includes:

in an infinite passive space; is filled with linear and isotropic uniform ideal media; a time-harmonic field; a uniform plane wave;

if a uniform plane wave is transmitted along the z-axis and the equiphase plane is the xy-plane, the electromagnetic intensity and the magnetic field intensity are not functions of x and y, that is

Due to the fact that

To obtain

In the same way

To obtain H_Z＝0；

Obtaining that the electric field intensity and the magnetic field intensity of the uniform plane wave are perpendicular to the propagation direction of the wave;

at this time

Provided that the electric field has only an x-component, i.e.

Solution to E_x(z)＝A₁e^-jkz+A₂e^jkz

First item

Second item

ByTo obtain

Wherein

Referred to as the intrinsic impedance of the medium; in vacuum

In the same way, for

In an ideal medium, the electric field strength and the magnetic field strength of a uniform plane wave are perpendicular to each other and in phase.

Optionally, the step 3) specifically includes:

the lower computer sends the collected data and the data analysis processing to the upper computer, and the upper computer background software realizes data recording; analyzing the data through Hilbert transform;

any one of the time sequences g (t) is changed into by Hilbert transform

In the formula, P is a Cauchy main value and takes the value of 1; hilbert transform of signal g (t)

Is the convolution of the original signal g (t) with 1/(tt) in the time domain, which corresponds to the multiplication in the frequency domain, by converting it into the frequency domain:

represents a fourier variation;

the original signal amplitude and frequency are unchanged through Hilbert transform, and the phase is shifted by 90 degrees; and generating an analytic signal and analyzing the corrosion degree of the steel bars in the reinforced concrete.

The invention has the beneficial effects that:

(1) a coupling agent is not needed, and non-contact detection can be carried out;

(2) during detection, the probe does not need to be in contact with a workpiece, and the detection speed is high;

(3) can be used for high temperature detection and the like;

(4) the excitation signal is a pulse square wave with a certain duty ratio and low frequency, and the low-frequency pulse signal has rich information content of frequency, wide frequency spectrum and strong signal penetrating power;

(5) under the near-field distance of the traditional eddy current detection sensor, compared with the pulse eddy current detection sensor, the pulse eddy current detection sensor has a larger near-field area, and even if the lift-off height of the sensor is larger, the pulse eddy current detection sensor still remains in the coverage range of detection signals.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the means of the instrumentalities and combinations particularly pointed out hereinafter.

Drawings

For the purposes of promoting a better understanding of the objects, aspects and advantages of the invention, reference will now be made to the following detailed description taken in conjunction with the accompanying drawings in which:

fig. 1 is a working principle diagram of the present invention.

Detailed Description

The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present invention in a schematic way, and the features in the following embodiments and examples may be combined with each other without conflict.

Wherein the showings are for the purpose of illustrating the invention only and not for the purpose of limiting the same, and in which there is shown by way of illustration only and not in the drawings in which there is no intention to limit the invention thereto; to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product; it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.

The same or similar reference numerals in the drawings of the embodiments of the present invention correspond to the same or similar components; in the description of the present invention, it should be understood that if there is an orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "front", "rear", etc., based on the orientation or positional relationship shown in the drawings, it is only for convenience of description and simplification of description, but it is not an indication or suggestion that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes, and are not to be construed as limiting the present invention, and the specific meaning of the terms may be understood by those skilled in the art according to specific situations.

The invention can be realized by the following technical scheme: a non-contact type magnetic induction detection method for bridge corrosion steel bars comprises five parts, namely an excitation source (1), an excitation coil (2), an induction coil (3), a signal processing circuit (4) and an upper computer (5), wherein excitation signals with different frequencies, amplitudes and waveforms are generated through the excitation source. Then the exciting signal is input into the exciting coil, the exciting coil generates a magnetic field in the space under the action of the exciting source, the steel bar in the reinforced concrete generates an eddy current effect under the action of the space magnetic field, and simultaneously a magnetic field is generated, the magnetic field received in the induction coil is the common effect of the exciting coil and the magnetic field generated by the steel bar eddy current, the signal generated by the exciting coil is removed through the differential amplifying circuit, only the magnetic field generated by the steel bar eddy current effect in the reinforced concrete is left, the data is transmitted to the upper computer through the signal processing circuit, and the judgment of the corrosion degree of the steel bar in the reinforced concrete can be completed through the analysis and processing of the signal. The invention adopts a magnetic induction detection technology that an excitation source is a pulse square wave signal.

A non-contact type bridge corrosion steel bar magnetic induction detection method comprises the following steps:

1) acquiring eddy current effect electromagnetic parameters;

when an excitation signal generated by an excitation source is applied to two ends of the excitation coil L1, magnetic lines generated by the L1 inevitably cut the detected corrosion steel bar M (M can be regarded as a short-circuit coil), and eddy current i is generated in the corrosion steel bar M, and the eddy current consumes part of magnetic field energy, so that the magnetic lines reaching the L2 are reduced, and f is reduced. The larger the thickness a of M, the larger the eddy current loss, and the smaller the detection coil induced electromotive force E, as shown in fig. 1. Therefore, the size of E indirectly reflects the size of M, and the diameter of the steel bar is inevitably reduced after the steel bar is corroded, so that the corrosion degree of the steel bar can be judged by judging the size of E.

The relationship between E and h can be represented by the following formula

E＝KUe^-d/h

Wherein d is the thickness of the corrosion steel bar; h is the vortex penetration depth; k is a proportionality constant.

2) Determination of the propagation of the magnetic field in air;

in an infinite passive space; is filled with linear and isotropic uniform ideal media; a time-harmonic field; a uniform plane wave.

If a uniform plane wave is transmitted along the z-axis and the equiphase plane is the xy-plane, the electromagnetic intensity and the magnetic field intensity are not functions of x and y, that is

Due to the fact that

To obtain

In the same way

To obtain H_Z＝0

The electric field intensity and the magnetic field intensity of the uniform plane wave are perpendicular to the propagation direction of the wave, namely transverse electromagnetic wave (TEM wave)

At this time

Provided that the electric field has only an x-component, i.e.

Its solution is E_x(z)＝A₁e^-jkz+A₂e^jkz

First item

Second item

By

Can obtain the product

WhereinReferred to as the intrinsic impedance of the medium. In vacuum

In the same way, for

Therefore, in an ideal medium, the electric field strength and the magnetic field strength of a uniform plane wave are perpendicular to each other and in phase.

3) Data transmission and signal analysis processing

The lower computer sends the collected data and the data analysis processing to the upper computer, and the upper computer background software realizes data recording. The instantaneous frequency has no unique definition method, and the data can be analyzed through Hilbert transform.

Any one of the time sequences g (t) may be changed into by the Hilbert transform

Where P is the Cauchy principal value and can be simply taken as 1, the Hilbert transform of the signal g (t)Is the convolution of the original signal g (t) with 1/(tt) in the time domain, which is converted into the frequency domain, it can be seen that the convolution in the time domain is equivalent to a multiplication in the frequency domain:

representing the fourier variation. Therefore, the original signal amplitude and frequency can be unchanged and the phase can be shifted by 90 degrees through Hilbert transform. And further, an analytic signal can be generated, and the corrosion degree of the steel bar in the reinforced concrete can be analyzed.

Let the excitation source signal be pulse square wave, frequency be f, and current be I₁The square wave is led into an exciting coil with the turns of a and the diameter of d, and when the current is constant I₁At this time, a magnetic field intensity of

When the rising edge or the falling edge of the pulse signal arrives, the space magnetic field can be generated, so that an alternating magnetic field is formed, the corrosion reinforcing steel bars in the concrete can generate an eddy current effect in the alternating magnetic field, an induced electromotive force epsilon is generated, the current is i epsilon/R, and the current can also generate a reverse time-varying field B₂. At the moment, the induction coil is subjected to a magnetic field B₁And B₂By differential amplification of the magnetic field B generated by the excitation coil₁Is cancelled out by acquiring a signal in which only the magnetic field B is present in the induction coil₂The generated sensing signal. The induction signal is a voltage oscillation-attenuation curve, the peak value E of the induction signal of the detection coil is taken as a characteristic value, and if the steel bar is partially corroded at the moment, KUe is obtained according to the E^-d/hIt can be seen that as the diameter d of the steel bar is changed, the corresponding E is also changed, i.e. the conductive portion thereof is reduced. At the moment, the eddy current effect generated by the corrosion reinforcing steel bar is relatively weak, and the current is relatively small, so that the generated magnetic field B is generated₃Also smaller, B collected by the detection coil₂，B₃The collected data are sent to an upper computer by the electric signal, and data recording and analysis are realized by upper computer background software, so that the data acquisition and analysis can be completedAnd judging the corrosion degree of the steel bars in the reinforced concrete.

Finally, the above embodiments are only intended to illustrate the technical solutions of the present invention and not to limit the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions, and all of them should be covered by the claims of the present invention.