CN100370238C - Apparatus for measuring internal stress of ferromagnetic material - Google Patents

Abstract

The present invention belongs to the field of material stress non-destructive detection, and particularly relates to a non-destructive detection device for detecting remaining stress in ferromagnetic material by detecting the change of induction voltage in an induction coil of the ferromagnetic material. The present invention is composed of a T-shaped iron core and a concave iron core, wherein a core shaft of the T-shaped iron core is wound with an exciting coil which can generate an alternating magnetic field; two sets of induction coils which have the same turn numbers and are reversely connected in series are wound on the concave iron core, and the two sets of induction coils are symmetric with the core shaft of the T-shaped iron core; one side of an area surrounded by the T-shaped iron core and the concave iron core has a detection end, and the other side has a reference end; a sample which has stress and is to be detected is placed on the detection end, and a standard detection sample with the same material, which has no stress, is placed on the reference end. The size of the inner stress of the sample to be detected can be calculated or the change trend of the inner stress of the sample to be detected can be predicted by detecting voltages on both ends of the induction coils to find stress concentration parts; necessary measures are carried out on the parts to be damaged to release stress, and accidents caused by member damages can be avoided.

Description

A kind of device of measuring internal stress of ferromagnetic material

Technical field

The invention belongs to material stress Non-Destructive Testing field, be specifically related to a kind of variation, measure a kind of the cannot-harm-detection device of ferromagnetic material internal residual stress by induced voltage in the measurement ferromagnetic material inductive coil.

Background technology

The plant equipment that ferromagnetic material is formed, even reasonable in design, under rated load, to work, the stack of unrelieved stress and working stress will cause the secondary deformation of member and the redistribution of unrelieved stress, thereby reduce the serviceable life of member and equipment, serious even cause serious accident.For a long time, the research to ferromagnetic material fatigue damage in the military service process and Life Prediction method is subjected to various countries scholar's attention in the world always.Therefore, study that a kind of convenient and reliable that the ferromagnetic material member is carried out the method for Non-Destructive Testing is just very necessary.

In the detection of ferromagnetic material, a kind of lossless detection method of widespread use is an x-ray method, but because the X ray wavelength is longer, its investigation depth (10 μ m level) is restricted.Because sound can more go deep into ferromagnetic material inside, relevant supercritical ultrasonics technology is measured unrelieved stress and has been obtained very big development, especially shear-wave birefringence The Application of Technology recently.But the variation of ultrasonic velocity is very small, and it is measured the ferromagnetic material internal stress method and be not easy and realizes, and the structure of material is also very big to its measurement result influence.

The applied magnetics method is measured unrelieved stress and is mainly contained magnetic mnemonics and magnetosonic method.The magnetic property that the utilization of magnetic mnemonics is in the ferromagnetic metal in the magnetic field of the earth produces irreversible change in stress and distortion concentration zones, magnetic permeability transition appears at metal and air boundary, its surface produces stray field, measure this stray field just can can't harm, quick, convenient, determine structural stress of ferromagnetic metal and distortion concentration zones exactly, be section and position the most dangerous on the equipment, carry out the diagnosis in intensity and life-span.This technology has remedied the deficiency of traditional lossless detection method, but the magnetic memory principle does not also form complete tight theoretical system, and does not carry out the detection by quantitative of defective, and the China Metrology Accreditation of not passing through national metering mechanism.

Also has magnetosonic shooting method (Magnetomechanical Acoustic Emission, MAE), also be a kind of strip magnetic measurement method, thereby it utilize the rotation of reciprocating vibration and magnetization vector under the neticdomain wall outside magnetic field effect in the ferromagnetic material and produce stress wave and cause acoustic emission phenomenon.Because this acoustic emission (AE) signal intensity produces regular variation with the suffered stress of magnetical component, therefore can get the stressing conditions of primary member by measuring the AE signal.But when determining stress sign by the signal waveform contrast, reliability is relatively poor, and operation is also complicated.

Stress in ferrimagnet and fault of construction, and some other characteristic in the metal, also can be by in metal, setting up mM disodium hydrogen phosphate and analyzing the magnetic noise that in metalwork, produces by magnetic field and discern, this Detection Techniques have been used and have been called as " Barkhausen " phenomenon.When promptly the big magnetic field in being based upon hardware gradually changes, in magnetized a series of sudden changes of material and jump.Provided the discussion about barkhausen in people's such as cycle No. 02200764.4 patent, and designed a probe and be used for measuring stress, " Barkhausen noise " that cell winding carries can obtain by suitable method.Barkhausen noise intensity that certain part produces in metal depends in part on the micromechanism of the ess-strain and the metal of this part, has attempted to determine the stress in the hardware or the microcosmos structure characteristic of strain and defective and metalwork with barkhausen and Barkhausen noise.Use barkhausen and determine that the stress in the metalwork or the most systems of strain comprise a drive coil system and a sensing coil system.Drive coil is arranged in the testing process position near metalwork.And this coil is by periodically variable signal excitation in time, so that induce periodically variable in time magnetic field in metalwork.The result that Barkhausen noise produces in metalwork is experienced by sensing coil and is transported to and can handles in many ways in the circuit of noise.At last, treated Barkhausen noise is sent to display device.

Summary of the invention

The present invention is in order to solve in the existing measuring system, measure coarse shortcoming, designed a kind of sensor device of brand-new measurement ferromagnetic material internal stress, it determines the internal stress of ferromagnetic material by measuring connect with standard sample one side magnitude of voltage in two inductive coils of reversal connection of tested sample one side.

Principle of the present invention is as follows:

Ferrimagnet has domain structure, ferromagnetic material under the effect of stress, magnetic domain that it is inner and magnetic permeability, micromechanism such as magnetic resistance and parameter all change.Stress theory according to domain wall displacement ^[1], the initial susceptibility of ferromagnetic material is ${\mathrm{\χ}}_i\≅\frac{{\mathrm{\μ}}_0{M}_s^2}{{\mathrm{\λ}}_s\mathrm{\σ}},$ (μ ₀Be permeability of vacuum, M _sBe magnetization vector, λ _sBe the saturation magnetostriction coefficient, σ is a stress), visible magnetic susceptibility reduces along with the increase of stress.We also know ferromagnetic initial susceptibility χ _iWith initial permeability μ _iRelation be μ _i=1+ χ _iSo magnetic permeability also will reduce along with the increase of internal stress.Relation formula B=μ according to magnetic induction density and magnetic permeability ₀(H+M)=μ ₀(H+ χ _iH)=μ ₀(1+ χ _i) H=μ ₀μ _iH (B is a magnetic induction density, and H is a magnetic field intensity, and M is the magnetization) has so just set up the funtcional relationship of magnetic induction density and stress.Promptly $B\≅{\mathrm{\μ}}_0(1+\frac{{\mathrm{\μ}}_0{M}_s^2}{{\mathrm{\λ}}_s\mathrm{\σ}})H.$

Again because induced voltage $\mathrm{\ϵ}=\frac{\mathrm{d\Φ}}{\mathrm{dt}}=\frac{d(B\·S)}{\mathrm{dt}}$ (φ is a magnetic flux, S magnetic flux area), the transposition integration gets $B=\frac{1}{S}\∫\mathrm{\ϵ}\left(t\right)\mathrm{dt}$

Will $B\≅{\mathrm{\μ}}_0(1+\frac{{\mathrm{\μ}}_0{M}_s^2}{{\mathrm{\λ}}_s\mathrm{\σ}})H$ The substitution following formula can obtain the funtcional relationship between induced voltage and the stress,

${\mathrm{\μ}}_0(1+\frac{{\mathrm{\μ}}_0{M}_s^2}{{\mathrm{\λ}}_s\mathrm{\σ}})H=\frac{1}{S}\∫\mathrm{\ϵ}\left(t\right)\mathrm{dt}$

So can determine the size of the suffered stress of ferromagnetic material by the variation of measuring the ferromagnetic material induced voltage, ultimate principle of the present invention that Here it is.

The device of measurement internal stress of ferromagnetic material of the present invention is made up of T shape iron core and spill iron core, on the mandrel of T shape iron core, be wound with the drive coil that can produce alternating magnetic field, on the spill iron core mandrel of symmetrical T shape iron core be wound with the number of turn identical and the polyphone reversal connection two groups of inductive coils, zone one side that T shape iron core and spill iron core surround is a measuring junction, opposite side is a reference edge, measuring junction is placed the tested sample that contains stress, reference edge is placed the standard sample of the identical material do not contain stress, can calculate the size of tested sample internal stress or dope the variation tendency of tested sample internal stress by the magnitude of voltage of measuring the inductive coil two ends.

Different ferromagnetic material magnetic permeabilities is different with magnetic resistance, required exciting current also is different, under the situation of signal source amplitude and fixed-frequency, can be by adjusting the extended distance size between spill iron core and the T shape iron core, measure the internal stress of difformity and different types of ferromagnetic material, be that the spill iron core can freely slide along T shape iron core, the reference edge that is surrounded by spill iron core and T shape iron core and the openings of sizes of measuring junction also change thereupon, as a kind of preferred implementation, thereby the measurement mechanism that this patent provides a kind of spill iron core to move forward and backward along the mandrel of T shape iron core, the device that is measurement internal stress of ferromagnetic material of the present invention is made up of T shape iron core and spill iron core, spill iron core hollow and can moving forward and backward along the mandrel of T shape iron core.

In this patent, two groups of inductive coils both can be on two outshots of spill iron core, also can be on the arm with respect to the symmetrical spill iron core of T shape iron core mandrel.Identical and the inductive coil polyphone reversal connection of the number of turn is used for responding to the induced potential of sample and standard specimen respectively, can get rid of the interference of surrounding environment factor like this, can accurately draw the suffered stress situation of sample.The voltage at inductive coil two ends can also can connect surveying instruments such as oscillograph by the effective value of digital multimeter read-out voltage, or connects computing machine after filtering, conversion, is shown by computer screen, analyzes after the reading of data and handles.

In this patent, drive coil can provide signal through power amplifier by signal generator.The electric current that signal generator and power amplifier provide certain frequency and intensity for the drive coil of measurement mechanism, so that produce suitable variation magnetic field when detecting ferromagnetic component, the frequency of signal can not be high frequency, otherwise skin effect ^[2]Obviously, induction current concentrates on the tested sample surface, and investigation depth reduces, and low excessively amplitude and frequency then can't drive drive coil, causes detection sensitivity to worsen.Suitable range of choice is that its amplitude range is 50mv-100mv from the sine wave signal of signal generator output certain frequency and intensity, and frequency range is 30Hz-100Hz, and the output power of power amplifier can be 10W-100W.

Drive coil selects for use line directly to be the enameled wire of 0.5mm-1.0mm, twines the 150-300 circle.Under the effect of pumping signal, standard sample and tested sample and iron core measuring junction and the contacted part of reference edge all are magnetized.Two groups of inductive coils are selected the enameled wire of line footpath 0.1mm-0.35mm for use, have twined the 800-1500 circle, with the inductive coil reversal connection of contacting, as shown in Figure 3.Terminals all are under the situation of standard sample at measuring junction and reference edge, and c, the voltage between the f are zero.When measuring junction is the tested sample that contains stress, reference edge is when not containing the standard sample of stress, the voltage of two inductive coils is inequality, and its difference (being the voltage between c, f) is the induced voltage that ferromagnetic material member internal stress produces by this patent measurement mechanism.

Instrumentation plan as shown in Figure 1, when measuring junction is the tested sample that contains stress, reference edge is not when containing the standard sample of stress, the magnitude of voltage at c, f two ends is the inductive voltage value that stress produces, and can read its effective value by digital multimeter.

Apparatus of the present invention can be found the concentrated position of stress by the detection of its stress before the fission of member generation crackle, at the position that will be damaged, take measures necessary to make stress relief, avoid causing the accident because of the damage of member.

Description of drawings

Fig. 1: be the structural representation of the described measurement internal stress of this patent device;

(a) being front elevation, (b) is left view, (c) is vertical view, (d) is right view;

Fig. 2: be a concrete synoptic diagram of implementing of the described measurement internal stress of this patent device;

Fig. 3: be the connected mode synoptic diagram of two groups of inductive coils on this patent moving iron core;

Fig. 4: be the magnetic direction test synoptic diagram vertical with stress direction;

Fig. 5: be magnetic direction inductive voltage value and the stress value curve relation figure vertical with stress direction;

Fig. 6: be the magnetic direction test synoptic diagram parallel with stress direction;

Fig. 7: be magnetic direction inductive voltage value and the stress value curve relation figure parallel with stress direction.

Embodiment

Below in conjunction with the drawings and specific embodiments the present invention is described in further details.

As shown in Figure 1, opening 5, the outshot 31,33 of spill moving iron core, the arm 32 of spill moving iron core, pumping signal input end a, b that the each several part name is called the mandrel 11, drive coil 2, spill moving iron core 3, inductive coil 4 (wherein first group of inductive coil 41, second group of inductive coil 42) of T shape iron core 1, T shape iron core, is surrounded by T shape iron core 1 and spill moving iron core 3, induced voltage output terminal c, d, e, f.

The described device of this patent is made up of T shape iron core 1 and spill iron core 3, on the mandrel 11 of T shape iron core 1, be wound with the drive coil 2 that can produce alternating magnetic field, on spill iron core 3 mandrel 11 of symmetrical T shape iron core 1 be wound with the number of turn identical and the polyphone reversal connection two groups of inductive coils 41,42, zone one side that T shape iron core 1 and spill iron core 3 surround is a measuring junction, opposite side is a reference edge, measuring junction is placed the tested sample that contains stress, reference edge is placed the standard sample of the identical material do not contain stress, can calculate the size of tested sample internal stress or dope the variation tendency of tested sample internal stress by the magnitude of voltage of measuring the inductive coil two ends.

As a kind of embodiment of this patent, spill iron core 3 hollows can move forward and backward along the mandrel 11 of T shape iron core 1.Two groups of inductive coils 41,42 are on two outshots 31,33 of spill iron core 3 or on the arm 32 with respect to the symmetrical spill iron core of T shape iron core mandrel.

As shown in Figure 2, the electric current that signal generator and power amplifier provide certain frequency and intensity for the drive coil 2 of T shape iron core 1 is so that produce suitable variation magnetic field when test material.Under the effect of pumping signal, standard sample and tested sample and iron core measuring junction and the contacted part of reference edge all are magnetized.Be wrapped in identical two groups of inductive coils 41,42 of the number of turn on the spill iron core 3 and be used for responding to the induced potential of tested sample and standard sample respectively, two line of induction astragals footpath is identical, the series connection reversal connection.When measuring junction is the tested sample that contains stress, reference edge is when not containing the standard sample of stress, the voltage of two inductive coils is inequality, its difference is the induced voltage that stress produces, after signal amplification, filtering etc. are handled, through the A/D conversion, analog quantity is converted to digital quantity again, processing through single-chip microcomputer demonstrates voltage signal.

According to test as can be known, linear to the internal stress and the inductive voltage value of a certain definite material, can utilize computing machine to set up the stress of sample to be tested and the distributed data base of voltage.The measurement result and the magnitude of voltage in the database of sample to be tested are compared, can calculate corresponding stress value.

The T shape iron core of this patent and spill moving iron core are formed by the siliconized plate of high magnetic conductivity.Nominal thickness 0.35-0.50 (δ/mm).Maximum iron loss 3.10 (P _15/50/ W.kg ^-1), minimum magnetic strength 1.59 (B _50/T), solid density 7.65 (D/g.cm ^-3).

Signal generator adopts U.S. An Jielun (AGINENT) 33120A, and its lifting time is 100ns (an allusion quotation shape value), and is linear in 0.1% of peak value output, and precision is regulation output 1%, and flatness is (＜100KHz=± 1% (0.1dB).Signal generator produces pumping signal, output 37HZ, 50mv (peak value) sine wave.Through power amplifier, power amplifier is with Guangzhou magnificent AMP175 far away, and operation DC voltage is 25-32V, and output rating is 35W, and peak power output is 75W, voltage frequency response 10-50KHz, degree of distortion 0.7%, gain 30dB, input impedance 47K Ω.The excitation of power amplifier output is received a of drive coil as the input of this measurement, on the b terminal, as shown in Figure 1.

Drive coil selects for use line directly to be the enameled wire of 0.69mm, twines 200 circles.Under the effect of pumping signal, the contacted part of standard sample and tested sample and measuring junction and reference edge all is magnetized.Two inductive coils are selected the enameled wire of line footpath 0.15mm for use, have twined 1000 circles, and inductive coil is contacted.

In experiment, we adopt Tonghua Iron and Steel Co. to produce 20#, and the weldless steel tube of 3087 materials is as sample.Outer diameter of steel pipes 82mm, wall thickness 12mm, height 200mm.Use the CSS-44200 electronic universal experimental machine of Changchun experimental machine Research Institute to give steel pipe two ends imposed load, simulate suffered stress.

Read c as shown in Figure 1 at last, the magnitude of voltage at f two ends is inductive voltage value.Can adopt the effective value of digital multimeter read-out voltage.Digital multimeter adopts U.S. An Jielun (AGILENT) 34401A, accuracy: 0.04+0.02 accuracy specification ± (% of the %+ range of reading) (1.000000V-750.000V, 10Hz-20Hz24 hour).Inductive voltage value and stress value relation curve such as Fig. 5, shown in Figure 7.

In the experiment, press begins pressurization from OkN, and speed is 0.5kN/s, is added to release behind the 80kN always.Every increase 5kN keeps 30s, keeps finishing preceding 5 seconds record induced potential values.On the record of data, we convert KN to MPa

(1) magnetic direction is vertical with stress direction

Stress direction is vertical with the magnetizing field direction, tests synoptic diagram as shown in Figure 4, obtains the curve map of stress and induced voltage relation, as shown in Figure 5.From curve map as can be seen, under the magnetizing field situation vertical with stress, along with the increase of pressure, induced voltage is linear to rise.

(2) magnetic direction is parallel with stress direction

Test synoptic diagram as shown in Figure 6, the magnetizing field direction is vertical with stress direction.In this experiment, obtained sample 2 stress and induced voltage relation curve as shown in Figure 7.As can be seen from the figure, under the magnetizing field situation parallel with stress, along with the increase of stress, inductive voltage value reduces, and is linear decrease basically.The initial magnetization principle is confirmed.

[1] as if 197 pages of De Fuluo generation China " Physics of Magnetism " Electronic Industry Press front page in 1987

[2] the 2nd edition 473 pages of Zhao Kai Hua Chenxi scheme " electromagnetism " Higher Education Publishing House June in 1985

Claims (5)

1. device of measuring internal stress of ferromagnetic material, it is characterized in that: form by  shape iron core (1) and spill iron core (3), on the mandrel (11) of  shape iron core (1), be wound with the drive coil (2) that can produce alternating magnetic field, the mandrel (11) of going up symmetrical  shape iron core (1) at spill iron core (3) is wound with two groups of inductive coils (41 of the identical and polyphone reversal connection of the number of turn, 42), zone (5) one sides that  shape iron core (1) and spill iron core (3) surround are measuring junction, opposite side is a reference edge, measuring junction is placed the tested sample that contains stress, reference edge is placed the standard sample of the identical material do not contain stress, can calculate the size of tested sample internal stress or dope the variation tendency of tested sample internal stress by the magnitude of voltage of measuring the inductive coil two ends.

2. the device of measurement internal stress of ferromagnetic material as claimed in claim 1 is characterized in that: spill iron core (3) hollow can move forward and backward along the mandrel (11) of T shape iron core (1).

3. the device of measurement internal stress of ferromagnetic material as claimed in claim 1 or 2 is characterized in that: two groups of inductive coils (41,42) are on two outshots (31,33) of spill iron core (3) or on the arm (32) with respect to the symmetrical spill iron core of T shape iron core mandrel.

4. the device of measurement internal stress of ferromagnetic material as claimed in claim 1 or 2, it is characterized in that: drive coil (2) provides signal by signal generator through power amplifier, the sine wave signal of signal generator output certain frequency and intensity, its amplitude range is 50mv-100mv, and frequency range is 30Hz-100Hz.

5. the device of measurement internal stress of ferromagnetic material as claimed in claim 1 or 2, it is characterized in that: drive coil (2) selects for use line directly to be the enameled wire of 0.5mm-1.0mm, twine the 150-300 circle, two groups of inductive coils (41,42) are selected the enameled wire of line footpath 0.1mm-0.35mm for use, twine the 800-1500 circle.

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