CN100412520C - Amorphous alloy strain gauge - Google Patents

Abstract

The middle of amorphous alloy thin strip heaves to one side and forms arch bridge type magnetic pole of a kind of amorphous alloy strain gauge. The bridge of magnetic pole parallel winds along the body of amorphous alloy thin strip and the height of heave is h, 0<h<0.5mm.There are excitation loop and measure loop enlace on the pole side by side and the magnetic field intensity is 0.01-0.05A/mm of the excitation loop. The amorphous alloy strain gauge adheres strongly on surface to measuring material so it takes distortion with measuring work piece along the portrait at the same time. It arouses the change of iron core magnetism conductance and inductance value to finish the test of piece. It utilizes well soft magnetism characteristic and steady temperature capability of amorphous alloy, so it is fit for testing tiny force and displacement with high testing sensitivity. Its temperature error is small and testing circuit is easy to be used in abominable condition with long using life.

Description

Amorphous alloy strain gauge

Technical field

The present invention relates to a kind of device that is used for the measurement of mechanical stress, particularly a kind of amorphous alloy strain gauge.

Background technology

The technology of measurement stress and method have multiple, and close with amorphous alloy strain gauge is strain ga(u)ge, is called resistance strain gage again, and the principle of work of resistance strain gage is based on its strain effect.When using foil gauge to measure component stress or strain, resistance strain gage is pasted on tested component surface, foil gauge and part are out of shape together, because wire size and resistivity all change in the sheet, resistance value wiry also changes, and the variation of measuring resistance value by metering circuit (electric wire strain gauge) can be tried to achieve the size of strain or stress.Strain ga(u)ge is a common technology of measuring physical quantitys such as strain, loading, pulling force, pressure at present, but also have some shortcomings: conventional foil gauge is under big strain regime, the relation of resistance change rate and strain presents bigger non-linear, and semiconductor gauge is more remarkable.Conventional foil gauge output signal is less, and signal is connected lead will conscientiously be shielded..Foil gauge has the dimensions.So actual what measure is mean strain on a certain area, can not show the situation of stress gradient in the stress field fully.Be subjected to Temperature Influence bigger.Be not suitable for long-term work under rugged environment.

Summary of the invention

The technical problem to be solved in the present invention is at the deficiencies in the prior art, has proposed a kind of amorphous alloy strain gauge highly sensitive, that temperature error is little of measuring.

The technical problem to be solved in the present invention is achieved through the following technical solutions, a kind of amorphous alloy strain gauge, be characterized in: the middle part of amorphous alloy ribbon convexes to form arch-shaped magnetic pole to a side, the bridge floor of magnetic pole and amorphous alloy ribbon body be arranged in parallel, the height of magnetic pole projection is h, 0＜h＜0.5mm is wound with field coil side by side and measures coil on magnetic pole, the field coil magnetic field intensity is 0.01～0.05A/mm.

The technical problem to be solved in the present invention can also come by the following technical programs to realize that further the number of turn of field coil is 5～8 circles that the number of turn of measuring coil is 8～10 circles.

When using amorphous alloy strain gauge to measure stress, securely attached to the surface of measured material, its integral body is longitudinally deformed simultaneously with measured workpiece amorphous alloy strain gauge, thereby cause the variation of magnetic permeability in the iron core, cause inductance value to change, realize the detection of workpiece strain.Its principle of work is based on piezomagnetic effect, so-called piezomagnetic effect is meant, when magnetized measured material is subjected to stress, because magnetostrictive anisotropy, it is the parallel direction that positive material direction of magnetization turns to tension that tension will make λ s, also promptly increase (magnetic resistance reduces), and be difficult to magnetization, also promptly reduce (magnetic resistance increase) with the magnetic permeability of tension vertical direction with the tension vertical direction with the magnetic permeability of tension parallel direction; The situation of compressive stress is then opposite.Amorphous alloy is a kind of new material, because it has particular performances, that uses in sensor technology is more and more.The present invention utilizes good soft magnetic characteristic of amorphous alloy and stable temperature performance, compares with traditional strain ga(u)ge, and it has major advantage: (1) has higher measurement sensitivity, especially is fit to the measurement of little power or micro-displacement; (2) temperature error is little; (3) metering circuit is simple; (4) long service life can be worked under rugged surroundings.(5) simple in structure, easy to make.

Description of drawings

Accompanying drawing is a structure diagram of the present invention.

Embodiment

A kind of amorphous alloy strain gauge, the middle part of amorphous alloy ribbon 1 convexes to form arch-shaped magnetic pole 2 to a side, and the bridge floor of magnetic pole 2 and amorphous alloy ribbon 1 body be arranged in parallel, the height of magnetic pole 2 projectioies is h, 0＜h＜0.5mm, this value is the smaller the better, to reduce additional bending moment.On magnetic pole 2, be wound with field coil 4 side by side and measure coil 3.This moment, bossing was equivalent to iron-core coil.The concrete size of strainometer is mainly determined by the allowable stress of selected amorphous alloy material.The specification of the amorphous alloy ribbon that present domestic Antai Science and Technology Co., Ltd provided is: width 5～100mm, and thickness 0.03mm, length is cutting as required, and the user also can have special requirement made to order according to demand.When main measurement tension, can adopt relatively thinner amorphous alloy ribbon; When main measurement compressive stress, then can adopt thicker amorphous alloy ribbon.The user can pass through special customized, or increases the thickness of amorphous alloy ribbon by stack.

Strain gauge materials is selected

According to the magnetoelasticity theory, the pass between variation of the relative permeability of ferromagnetic material and the stress σ is

$\frac{\mathrm{\&Delta;\&mu;}}{\mathrm{\&mu;}}=\frac{2{\mathrm{\&lambda;}}_m}{B_m^2}\mathrm{\&sigma;\&mu;}$

In the formula, μ is the magnetic permeability of ferromagnetic material; B _mBe saturation induction density.By following formula as can be known, have higher measurement sensitivity in order to guarantee strainometer, selected amorphous alloy material should have bigger magnetostriction coefficient and magnetic permeability, less saturation induction density.In present technical three class amorphous alloys of being used widely, the material with above-mentioned characteristic surely belongs to the Fe base amorphous alloy of TM-M type.This material has very high electromechanical conversion efficiency, and through suitable annealing in process, its electromechanical conversion efficiency can also further improve.In addition, TM-M type amorphous alloy has good temperature stability and aging stability, and processibility is good, and low price is well suited for making strainometer.The Main physical performance of the Fe base amorphous alloy strip that present domestic Antai Science and Technology Co., Ltd produces is: saturation induction density Bs=1.56T; Curie temperature Tc=410 ℃; Saturation magnetostriction coefficient lambda s=27 * 10 ^-6Electricalresistivity=130 Ω μ-cm; Maximum permeability μ＞25 * 10 ⁴

The strainometer major parameter is determined

The major parameter of amorphous alloy strain gauge is field coil and the number of turn N that measures coil ₁, N ₂, the exciting current intensity I, magnetic field intensity H, wherein magnetic field intensity H has the greatest impact to the measurement sensitivity of strainometer.Determine that magnetic field intensity H will make amorphous alloy strain gauge be operated in the linearity range of maximum permeability and magnetization curve (B-H).The common magnetic field intensity H value that applies during core material, the excitation field intensity 0.01～0.05A/mm of amorphous alloy strain gauge.After magnetic field intensity H determines, can ask other parameters by following formula:

$N_1=\frac{\mathrm{Hl}}{I}$

In the formula, N _lBe the field coil number of turn; L is the amorphous alloy strain gauge projection length; I is an exciting current intensity.The number of turn of field coil is about 5～8 circles, and the number of turn of measuring coil is about 8～10 circles.But the dynamometry scope is (1～100) * 10 ⁴N.As field coil number of turn N _lAfter determining, the exciting current intensity I can be determined.

The magnetic circuit of amorphous alloy strain gauge is analyzed as follows.When amorphous alloy strain gauge was attached to the measured material surface securely, the two had just formed closed magnetic circuit.When the field coil feeding has the alternating current of certain frequency, just in field coil, produced alternating flux φ.According to magnetic circuit law, the instantaneous magnetic flux in the magnetic circuit is:

And $R_{\mathrm{AB}}=\frac{l_{\mathrm{AB}}}{{\mathrm{\&mu;}}_{\mathrm{AB}}\mathrm{hb}}$ $R_{\mathrm{CD}}=\frac{l_{\mathrm{CD}}}{{\mathrm{\&mu;}}_{\mathrm{CD}}\mathrm{ab}}$ $r_0=\frac{{\mathrm{\&delta;}}_0}{{\mathrm{\&mu;}}_{0}b{s}_0}$

In the formula, I---exciting current intensity; N _l---the field coil number of turn;

R _AB---the magnetic resistance of amorphous alloy strain gauge bossing;

R _CD---measured material surface C D section magnetic resistance;

r ₀---air-gap reluctance between strainometer and the measured material, if the two adheres to close and firm, air-gap reluctance can be ignored.

l _AB---the length of strainometer bossing; μ _AB---the amorphous alloy absolute permeability;

The thickness of h---amorphous alloy strain gauge;

B---the width of amorphous alloy strain gauge bossing;

l _CD---the length between measured material surface C D;

μ _CD---the absolute permeability of measured material;

α---the magnetic line of force is in the length of penetration on measured material surface;

δ ₀---the air gap thickness between amorphous alloy strain gauge and measured material surface;

μ ₀---air permeability;

s ₀---adhere to length between amorphous alloy strain gauge and measured material surface.

Know that according to Faraday's electromagnetic induction law the induced voltage of measuring in the coil is

$U=\frac{4\mathrm{\&pi;f}{\mathrm{IN}}_1{N}_2}{(\frac{l_{\mathrm{AB}}}{{\mathrm{\&mu;}}_{\mathrm{AB}}\mathrm{hb}}+\frac{l_{\mathrm{CD}}}{{\mathrm{\&mu;}}_{\mathrm{CD}}\mathrm{ab}}+\frac{{\mathrm{\&delta;}}_0}{{\mathrm{\&mu;}}_{0}b{s}_0})}$

F in the formula---exciting current frequency; M ₂---measure coil turn.

According to piezomagnetic effect, when there is stress on the measured material surface, for λ _s＞0 ferromagnetic material, when stress was tension, magnetic permeability μ improved, i.e. μ _ABBecome μ _AB+ Δ μ _AB, μ _CDBecome μ _CD+ Δ μ _CD, then magnetic resistance reduces; When stress is compressive stress, i.e. μ _ABBecome μ _AB-Δ μ _AB, μ _CDBecome μ _CD-Δ μ _CD, then magnetic resistance increases.The variation of magnetic resistance causes magnetic flux change, and the induced voltage U that measures in the coil also can change.

Because the magnetic permeability of amorphous alloy is much larger than the magnetic permeability of common ferromagnetic measurement, in addition, if can strict guarantee air gap thickness δ ₀Be zero, then following formula becomes

$U=\frac{4{\mathrm{\&mu;}}_{\mathrm{AB}}\mathrm{hb\&pi;fI}{N}_1{N}_2}{l_{\mathrm{AB}}}$

The surperficial magnetic characteristic of promptly measuring output induced voltage in the coil and measured material is irrelevant.

Bond quality counter stress measuring accuracy has very big influence between amorphous alloy strain gauge and the measured material.Adopt the method for pasting that amorphous alloy strain gauge is attached to tested component surface, simple, convenient, be convenient to execute-in-place, but want the choose reasonable cementing agent, in high quality faying face is handled.Selected cementing agent should have very high viscosity, should not produce bigger volumetric contraction again during curing, in addition, with the amorphous alloy strain gauge material, and all consistent with the thermal expansion between the tested construction material, otherwise produce non-homogeneous stress in the inner meeting of strainometer, influence measurement stability.With reference to the present normal metal bonding technology that adopts, earlier strainometer location for paste grinder buffing, use certain density sodium silicate solution cleaning and dipping number minute then, paste then.

Before measuring stress, demarcate the amorphous alloy strain gauge sensitivity coefficient, promptly the strainometer that same types of material is made only selects one of them to demarcate.

Claims (2)

1. amorphous alloy strain gauge, it is characterized in that: the middle part of amorphous alloy ribbon (1) convexes to form arch-shaped magnetic pole (2) to a side, the bridge floor of magnetic pole (2) and amorphous alloy ribbon (1) body be arranged in parallel, the height of magnetic pole (2) projection is h, 0＜h＜0.5mm, be wound with field coil (4) side by side and measure coil (3) on magnetic pole (2), field coil (4) magnetic field intensity is 0.01～2.05A/mm.

2. amorphous alloy strain gauge according to claim 1 is characterized in that: the number of turn of field coil (4) is 5～8 circles, and the number of turn of measuring coil (3) is 8～10 circles.

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