CN101545755A - Ferromagnet magnetostrictive effect-based method for testing length of anchor rod - Google Patents

Abstract

The invention discloses a ferromagnet magnetostrictive effect-based method for testing the length of an anchor rod, which comprises the following steps that: a magnetostrictive waveguide sensor is arranged on the free end of an anchor rod to be tested; a static bias magnetic field is applied at the mounting position of the magnetostrictive waveguide sensor; an exciting pulse signal is applied to the magnetostrictive waveguide sensor to excite mechanical vibration on the free end of the anchor rod; the sizes of the exciting pulse signal, exciting frequency and the static bias magnetic field are set to excite waveguides mainly in a longitudinal mode in the anchor rod; a receiving unit converts an elastic wave signal in a member to be tested into an electrical signal by using an inverse magnetostrictive effect, and after signal amplification, filtration and rectification, signal averaging and A/D conversion treatment, the electrical signal enters a test signal processing unit to test the actual length of the anchor rod to be tested. The method can realize the excitation and detection of ultrasonic waves in the anchor rod. The test signal contains information on the length and defects of the anchor rod and the actual length of a measured anchor rod can be measured accurately through the processing and analysis of a waveguide reflected wave signal.

Description

A kind of method for testing length of anchor rod based on ferromagnet magnetostrictive effect

Technical field

The present invention relates to the ferrimagnet lossless detection method, be specifically related to a kind of method for testing length of anchor rod based on ferromagnet magnetostrictive effect.

Background technology

Anchor rod anchored technology since its safely and fast, characteristics such as low cost are widely used in the construction of underground structure (tunnel, cavern etc.) of railway, highway, Mineral Engineering etc. and side slope are nursed.In use, anchor pole causes potential safety hazard because failure phenomenons such as crackle, corrosion can appear in a variety of causes, needs regularly its health status to be assessed.The anchor rod anchored concealed work that belongs to, supervision and oversight difficulty comparatively because anchor pole embeds after anchoring in the rock stratum, is supervised unit and can't effectively be detected its physical length in the work progress.The length that anchor pole embeds rock is that can anchor pole bring into play one of key of its effectiveness, the accident and the economic loss that added by the influence of construction quality not have complete detection means to cause are more and more, and be therefore most important to the length of anchor pole and quality testing and appraisal.

At present both at home and abroad the length detection to anchor pole still rested on the lifting jack pull-out test stage, and this method is not only taken a lot of work but also time-consuming, and detection method is breakage, so only limit to inspect by random samples.The Geodynamik company of Sweden at first proposes to detect the anchor pole quality with the principle of ultrasonic energy loss, and this method shooting conditions harshness, decay are fast, poor repeatability and to detect the accuracy of rock-bolt length lower; The nineties, U.S. mining authority office develops the ultrasonic instrument that can detect anchor pole strain and extensibility, but it can't estimate the construction quality of anchor pole, and the accuracy of surveying rock-bolt length is lower; Chinese scholar is limited to the apply pulse stress wave mostly to the research that anchor pole detects, and also is in the exploratory stage at present, and test result is not satisfactory.All there is certain deficiency in actual applications in existing method, device and the patent of measuring about rock-bolt length.200710099588.0 1 kinds of detections of application number are embedded in the method for rock-bolt length in the different medium, introduce one with detected bolt diameter, material, free bolt that shape is identical, by the analogy of tested anchor pole and free bolt frequency signal peak value and the response of echo speed in frequency, calculate rock-bolt length.This method has been ignored the Frequency Response that detected anchor pole and free bolt environment difference cause and has been changed, and it is bigger to detect error.

Summary of the invention

The object of the present invention is to provide a kind of method for testing length of anchor rod based on ferromagnet magnetostrictive effect, this method can be measured rock-bolt length fast and accurately.

Principle of the present invention is the magnetostrictive effect and the back wash effect thereof of ferrimagnet.Ferromagnet (as metal Ne, Fe, ferrite etc.) will be because the change of magnetized state will produce the alternation mechanically deform, and this phenomenon is called magneto-striction phenomenon.Magnetostrictive excitation principle is quite complicated, and from the minimum viewpoint of free energy, when the magnetized state of magnetic material changed, for making the gross energy minimum of system, shape of himself and volume changed.Ferrimagnet is applied suitable alternating magnetic field, utilize magnetostrictive effect can produce ultrasound wave.Ultrasound wave produces repeatedly past interflection on the discontinuous interface in medium, and then the complicated interference of generation forms supersonic guide-wave with how much disperses; Opposite, the mechanically deform meeting changes magnetic field, makes the coil in magnetic field produce induction current, and this phenomenon is called magnetostrictive reaction.Utilize this magnetic of ferrimagnet-Li transduction efficiency can realize hyperacoustic excitation and detection in the anchor pole.Include information such as rock-bolt length, defective in the anchor pole in the guided wave echoed signal, the guided wave echoed signal is carried out suitable processing and analysis, can measure the physical length of tested anchor pole accurately.

The step of the technical solution used in the present invention is as follows:

(1) with the magnetic striction wave guide sensor ring around being installed in tested anchor pole free end, this sensor is selected the structure of coupling for use according to the work on the spot environment, need not closely contact or medium coupling;

(2) apply quiescent biasing magnetic field in the anchor pole free end scope greater than magnetic striction wave guide sensor installation site and make its magnetization, quiescent biasing magnetic field is produced by dc coil or permanent magnet, and its magnetic direction is parallel to the anchor pole axis direction;

(3) apply excitation pulse signal to the magnetic striction wave guide sensor, motivate the mechanical vibration that produce by magnetostrictive effect at the anchor pole free end, the size in excitation pulse signal, excitation frequency and quiescent biasing magnetic field is set, in anchor pole, motivates guided wave based on longitudinal mode;

(4) receiving element utilizes magnetostrictive reaction that the elastic wave conversion of signals in the detected member is electric signal, include rock-bolt length information in this signal, detected electric signal enters the detection signal processing unit after by signal amplification, filter rectification, signal averaging, A/D conversion process;

(5) utilize calculating formula $V=\frac{{2L}_1}{{\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="A200910098260E00111.png"\; state="\{\{state\}\}">T</figure-callout>}}_1}$ Obtain the propagation group velocity V of guided wave in tested anchor pole, wherein L ₁Be distance between center sensor and the anchor pole free end face, T ₁Be the time interval between echoed signal of the anchor rod anchored end of detection signal and the anchor pole free end face second trip echo signal;

(6) utilize calculating formula $L=\frac{\mathrm{<figure-callout\; id="2"\; label="VT"\; filenames="A200910098260E00081.png,A200910098260E00101.png"\; state="\{\{state\}\}">VT</figure-callout>}}{2}+{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="A200910098260E00111.png"\; state="\{\{state\}\}">L</figure-callout>}}_1$ Obtain tested anchor pole total length L, wherein T is an echo of the anchor rod anchored end face of detection signal time of arrival;

(7) rock-bolt length detection signal process software can carry out real-time data acquisition and data are checked, (5), (6) step are repeated n time, gets tested rock-bolt length arithmetic mean value L, and L is tested anchor pole physical length, direct generation examining report after the data analysis.

The beneficial effect that the present invention has is:

Utilize this magnetic of ferrimagnet-Li transduction efficiency can realize hyperacoustic excitation and detection in the anchor pole.Include information such as rock-bolt length, defective in the anchor pole in the guided wave echoed signal, the guided wave echoed signal is carried out suitable processing and analysis, can measure the physical length of tested anchor pole accurately.

Description of drawings

Fig. 1 is a detection schematic diagram of the present invention.

Fig. 2 is the present invention's anchor pole sketch to be detected.

Fig. 3 is the open magnetic striction wave guide sensor of the present invention.

Fig. 4 is a closed type magnetic striction wave guide sensor of the present invention.

Fig. 5 is a bias magnetic field schematic diagram of the present invention.

Fig. 6 is a magnetic striction wave guide sensor sketch of the present invention.

Fig. 7 is that the present invention is applied to the detection signal that rock-bolt length detects.

Fig. 8 is that the present invention is applied to rock-bolt length and detects and to excite guided wave group velocity curve.

Among the figure: 1. magnetic striction wave guide sensor; 2. quiescent biasing magnetic field; 3. master control PC; 4.ARM partitioned signal treatment circuit; 5. high frequency signal generator; 6. power amplifier; 7. detection signal prime amplifier; 8. current rectifying and wave filtering circuit; 9.A/D converter; 10. storage oscilloscope; 11. guided wave exciting unit; 12. guided wave receiving element; 13. detection signal processing unit; 14. detected anchor pole; 15. anchor pole free end; 16. anchor rod anchored end; 17. anchor pole free end end face; 18. anchor rod anchored end end face; 19. open magnetic striction wave guide sensor; 20. plugboard; 21. closed type magnetic striction wave guide sensor; 22. coil rack; 23. array magnet; 24. programmed switch; 25.ARM control program; 26. electromagnetic pulse signal; 27. echoed signal of anchor pole free end; 28. echoed signal of anchor rod anchored end; 29. anchor pole free end second trip echo signal; 30. L in the anchor pole (0,2) mode guided wave group velocity curve.

Embodiment

The present invention is further illustrated below in conjunction with accompanying drawing and example.

Detection schematic diagram of the present invention as shown in Figure 1.At first magnetic striction wave guide sensor 1 being installed in tested anchor pole free end 15,16 is anchor rod anchored end.This sensor need not to contact with tested anchor pole or be coupled, and measures the distance L between magnetic striction wave guide center sensor and the anchor pole free end face 17 ₁Apply suitable quiescent biasing magnetic field and make its magnetization in anchor pole free end 15 scopes greater than magnetic striction wave guide sensor installation site, quiescent biasing magnetic field 2 can be produced by dc coil or circumference array magnet 23, and the present invention adopts the dc coil biasing.ARM partitioned signal treatment circuit 4 is connected by the control end of communication cable with high frequency signal generator 5, and the output terminal of high frequency signal generator 5 connects the input end of power amplifier 6.The output terminal of power amplifier 6 is transported to magnetic striction wave guide sensor 1 by high frequency cable with excitation pulse signal.Magnetic striction wave guide sensor 1 utilizes magnetostrictive effect to encourage the longitudinal mode guided wave in tested anchor pole 14, as shown in Figure 2.Guided wave is propagated in anchor pole behind end face reflection and is utilized counter magnetostriction effect to receive by magnetic striction wave guide sensor 1, detection signal enters guided wave receiving element 12, successively through signal amplifier 7, current rectifying and wave filtering circuit 8, A/D converter 9, enter detection signal processing unit 13, the detection signal processing unit is made up of storage oscilloscope 10 and master control PC3.Signal processing software is according to calculating formula among the master control PC3 $V=\frac{{2L}_1}{{\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="A200910098260E00111.png"\; state="\{\{state\}\}">T</figure-callout>}}_1}$ Obtain the propagation group velocity V of guided wave in tested anchor pole, wherein L ₁Be distance between center sensor and the anchor pole free end face, T ₁Be the time interval between echoed signal 28 of the anchor rod anchored end of detection signal and the anchor pole free end face second trip echo signal 29.Utilize calculating formula $L=\frac{\mathrm{<figure-callout\; id="2"\; label="VT"\; filenames="A200910098260E00081.png,A200910098260E00101.png"\; state="\{\{state\}\}">VT</figure-callout>}}{2}+{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="A200910098260E00111.png"\; state="\{\{state\}\}">L</figure-callout>}}_1$ Obtain tested anchor pole total length L, promptly anchor pole free end face 17 is to the distance between the anchor rod anchored end face 18.Wherein T is an echo of the anchor rod anchored end face of detection signal time of arrival.The detection signal process software repeats above computation process 100 times automatically, gets tested rock-bolt length arithmetic mean L, and L is tested anchor pole physical length.Can directly generate examining report after the data analysis.

Figure 6 shows that the structure principle chart of magnetic striction wave guide sensor among the present invention.Drive coil and receiving coil adopt same coil, 21 two types of open magnetic striction wave guide sensor 19 and closed type magnetic striction wave guide sensors are arranged, as shown in Figure 3, Figure 4, wherein openly be made up of flat cable and plugboard 20, the closed type coil is made up of enameled wire and coil rack 22.Realize that by programmed switch 24 programmings guided wave excitation and detection signal receive.The magnetic striction wave guide sensor at work, ARM programmed control 25 is gating guided wave exciting unit 11 at first, motivates guided wave in tested anchor pole 14, as shown in Figure 2; Behind the certain hour t, ARM programmed control 25 gating guided wave receiving elements 12 carry out guided wave and receive.

To help to understand the present invention by following example, but not limit content of the present invention.

As shown in Figure 2, anchor pole 14 length to be measured are that 5000mm, internal diameter are that 20mm, external diameter are the common hollow grouting anchor of 30mm.Magnetic striction wave guide sensor 1 structure diagram as shown in Figure 6, guided wave excitation and receiving with same coil realization, this coil is made up of flat cable and plugboard 20, loop length is 50mm, diameter is 35mm, and the number of turn is 20 circles, directly is that the flat cable coiling of 0.5mm forms with line; Quiescent biasing magnetic field adopts dc coil to provide, and bias coil length is 100mm, diameter 40mm, and the number of turn is 1000 circles, directly is that the enamel-cover copper wire coiling of 1mm forms with line.Whole magnetic striction wave guide sensor is installed with anchor pole free end to be measured relatively axle center symmetric position, measure between center sensor and the anchor pole free end face distance L 1 be 150mm.To bias coil 2 power supplies, supply current is 3A with D.C. regulated power supply, anchor pole free end to be measured is carried out the static state magnetization handle.Utilizing ARM partitioned signal treatment circuit 4 and high frequency signal generator 5 that pumping signal is set is that 4, interval time are 500 times for 200ms, multiplicity for frequency for 100K, pulse number.Pumping signal is transferred to magnetic striction wave guide sensor 1 after amplifying through power amplifier 6, encourages the longitudinal mode guided wave by magnetostrictive effect in tested anchor pole 14.Guided wave is propagated in anchor pole behind end face reflection and is utilized counter magnetostriction effect to receive by magnetic striction wave guide sensor 1, detection signal enters guided wave receiving element 12, successively passes through signal amplifier 7, current rectifying and wave filtering circuit 8, A/D converter 9 enters detection signal processing unit 13.The detection signal that obtains as shown in Figure 7.Be denoted as electromagnetic pulse signal 26 among Fig. 7, echoed signal 27 of anchor pole free end, echoed signal 28 of anchor rod anchored end, anchor pole free end second trip echo signal 29. as shown in Figure 5, the time interval T between echoed signal of the anchor rod anchored end of detection signal and the anchor pole free end face second trip echo signal ₁Be 59 μ s, by calculating formula $V=\frac{{2L}_1}{{\mathrm{<figure-callout\; id="1"\; label="T"\; filenames="A200910098260E00111.png"\; state="\{\{state\}\}">T</figure-callout>}}_1}$ Calculating guided wave speed is 5084.7m/s, conforms to L in the anchor pole among Fig. 8 (0,2) mode guided wave group velocity curve 30; An echo of the anchor rod anchored end face of detection signal T time of arrival is 1960 μ s, utilizes calculating formula $L=\frac{\mathrm{<figure-callout\; id="2"\; label="VT"\; filenames="A200910098260E00081.png,A200910098260E00101.png"\; state="\{\{state\}\}">VT</figure-callout>}}{2}+{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="A200910098260E00111.png"\; state="\{\{state\}\}">L</figure-callout>}}_1$ Obtaining tested anchor pole total length L is 5.133m.Utilization detection signal analysis software repeats above computation process 100 times automatically, gets tested rock-bolt length arithmetic mean L, and obtaining tested anchor pole physical length is 5.102m, and error rate σ is 2.04%, meets request for utilization fully.

Claims (1)

1, a kind of method for testing length of anchor rod based on ferromagnet magnetostrictive effect is characterized in that comprising that the step of this method is as follows:

(1) with the magnetic striction wave guide sensor ring around being installed in tested anchor pole free end, this sensor is selected the structure of coupling for use according to the work on the spot environment, need not closely contact or medium coupling;

(2) apply quiescent biasing magnetic field in the anchor pole free end scope greater than magnetic striction wave guide sensor installation site and make its magnetization, quiescent biasing magnetic field is produced by dc coil or permanent magnet, and its magnetic direction is parallel to the anchor pole axis direction;

(3) apply excitation pulse signal to the magnetic striction wave guide sensor, motivate the mechanical vibration that produce by magnetostrictive effect at the anchor pole free end, the size in excitation pulse signal, excitation frequency and quiescent biasing magnetic field is set, in anchor pole, motivates guided wave based on longitudinal mode;

(4) receiving element utilizes magnetostrictive reaction that the elastic wave conversion of signals in the detected member is electric signal, include rock-bolt length information in this signal, detected electric signal enters the detection signal processing unit after by signal amplification, filter rectification, signal averaging, A/D conversion process;

(5) utilize calculating formula $V=\frac{2L_1}{T_1}$ Obtain the propagation group velocity V of guided wave in tested anchor pole, wherein L ₁Be distance between center sensor and the anchor pole free end face, T ₁Be the time interval between echoed signal of the anchor rod anchored end of detection signal and the anchor pole free end face second trip echo signal;

(6) utilize calculating formula $L=\frac{\mathrm{VT}}{2}+L_1$ Obtain tested anchor pole total length L, wherein T is an echo of the anchor rod anchored end face of detection signal time of arrival;

(7) rock-bolt length detection signal process software can carry out real-time data acquisition and data are checked, (5), (6) step are repeated n time, gets tested rock-bolt length arithmetic mean value L, and L is tested anchor pole physical length, direct generation examining report after the data analysis.

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