CN1851418A - Method for constituting sound-field model of submmersilbe linear focusing pulse supersonic sensor - Google Patents

Abstract

The invention relates to a water logging line focusing impulse ultrasound sensor sound field constructing method that has rectangle piezoelectricity wafer and semi-column sound lens that could be widely used in ultrasound no-harmful testing field. The invention builds the space sound field mould of the sensor that could gain sound pressure parameter, sound pressure distribution, theory focus, and acoustic beam divergence angle. The invention takes numerical simulation to the axial sound pressure and testifies the axial sound pressure.

Description

Method for constituting sound-field model of submmersilbe linear focusing pulse supersonic sensor

Technical field:

The present invention sets up a kind of submmersilbe linear focusing pulse supersonic sensor sound field mathematical model, tries to achieve the sound field technical parameter and has carried out verification experimental verification by numerical solution.For theoretical foundation has been established in this type sensor application in Non-Destructive Testing.

Background technology:

Sonac based on piezoelectric chip has a wide range of applications in the Non-Destructive Testing field, and the line focus sonac is more satisfactory selections in a lot of detection occasions.The line focus sonac also has different kinds, and in the document (the 1. Yang Si universe, Liu Yanhua, Li Jinglong, the programming of water immersion focusing probe beam axis sound field is calculated, measuring technology journal, Vol.13 No.2 1999, p76-79.2.H.Ogi，M.Hirao，and?T.Ohtani.Line-focusing?electromagnetic?acoustic?transducers?for?the?detection?of?slitdefects.IEEE?Transactions?on?Ultrasonics，Ferroelectrics，and?FrequencyControl，Vol.46，No.2，March?1999，p341-346。3. Yan Rong is bright, and Ultrasonic Detection is studied with focusing lows of spherical lens, acoustic technique, 1994 the 3rd phases, p124-127.4. what family is loyal, Qian Shengyou, and Zhang Fucheng, the research of Transducer with Sphere-cone Lens, piezoelectricity and acousto-optic, Vol.24, No.4,2002, p287-288) set forth the method for building up of sound-field model of several line focus sonacs and the computing method of parameters,acoustic.These methods all provide theoretical reference for the actual use of the sensor of the type.

Different among the present invention in employed line focus impulse ultrasound sensor construction and the document are mainly reflected on the geometry of piezoelectric chip and sound lens, thereby cause its sound field different with other line focus sonac.This sensor does not also have theoretical sound-field model can supply to use for reference so far.

Summary of the invention:

The objective of the invention is to the sensor of this class formation set up its sound-field model, and the method for value solving of model is provided at the reality that does not still have at present theoretical model.

Method of the present invention specifically comprises the steps:

Modelling mainly comprises:

1) design feature according to real sensor takes out its physical model, and wherein, piezoelectric chip and sound lens are the main bodys of physical model; Piezoelectric chip is adopted rectangular geometries simulation, and be planar rectangular with sound lens with a side, opposite side is that the columniform geometry of part is simulated;

2) set up two cover coordinate systems on physical model, a cover coordinate system is a rectangular coordinate system, and in the heart, the x axle is along the length of lens direction in the sound lens back side for initial point, and the y axle is along the lens height direction, and the z axle is perpendicular to lens tool back plane (xoy face); One cover is a cylindrical coordinate system, and the right cylinder geometric center of getting inner lens surfaces is as initial point, and r is the radius-of-curvature of lens, and θ is the projection of point on the yoz plane and the angle of z axle positive dirction on the lens curved surface;

3) piezoelectric chip is divided into series of rectangular infinitesimal ds ₁, each ds ₁Be used as a point sound source, outwards launch spherical wave;

4) effect with lens is equivalent to phase transformer, and the point on the sound lens curved surface is regarded as the secondary point source, also outwards launches spherical wave;

5) the sound lens curved surface is divided into a series of infinitesimal ds ₂, the acoustic pressure at space any point place equals the result of all these secondary infinitesimal emitting sound wave in this some stack, thereby has obtained the sound-field model P of this type sensor; Work as x=0, during y=0, the acoustic pressure that obtains on the sensor axis distributes; The acoustic pressure maximum point is a focal length on the axis; Obtain its acoustic beam angle α according to focal length;

The numerical solution of model comprises:

6) adopt numerical method that the sensor sound field is found the solution; The concrete practice is that lens are divided into enough little zone, with the integration in the superposition approximation sound-field model of zonule sound field.

The present invention not only can provide this type The Mathmatic Models of Instrument Transducers by above six steps, and has provided the numerical solution of sound field.By numerical simulation, obtained focal length and axis sound field and distributed its axis sound field.

Description of drawings:

Fig. 1 is modelling and solution procedure block diagram; Fig. 2 is a cylinder sound lens model,

Fig. 3 distributes for the theoretical axis sound field and actual measurement axis sound field distributes

Fig. 4 calculates synoptic diagram for the acoustic beam angle,

The 1-piezoelectric chip; The 2-sound lens; The 3-sensor

Embodiment:

Below in conjunction with drawings and Examples technical scheme of the present invention is further described.

1) sound-field model is set up

This type sensor adopts plane rectangle piezoelectric chip, by cylindrical curved surface sound lens focusing acoustic beam.Be different from common line focus sensor on this type sensor construction, do not have ready-made sound-field model can supply to use for reference.Because the acoustic pressure on the focusing probe beam axis distributes and focal length, can become to give birth to big influence with testing result to detection scheme.For this reason, the present invention has set up the sound field distributed model of this line focus pulse transducer, and has found the solution this sensor axis sound field with numerical method, has calculated the focal length of sensor theoretically.And carried out the actual test of sensor axis sound field.

Set up two cover coordinate systems as shown in Figure 2.One cover coordinate system is a rectangular coordinate system, and in the heart, the x axle is along the length of lens direction in the sound lens back side for initial point, and the y axle is along the lens height direction, and the z axle is perpendicular to lens tool back plane (xoy face); One cover is a cylindrical coordinate system, and the right cylinder geometric center of getting inner lens surfaces is as initial point, and r is the radius-of-curvature of lens, and θ is the projection of point on the yoz plane and the angle of z axle positive dirction on the lens curved surface.

Wafer is made up of a series of point sources, each point source outwards launch single-frequency+spherical wave P ₁, do not consider the mutual interference between the point source, and the time at the arrival sound lens back side (xoy face) is identical.Then

P ₁＝p ₀exp(jw ₀t) (1)

Wherein, p ₀It is original acoustical signal amplitude; w ₀It is the ultrasound wave centre frequency.

After acoustic beam arrived lens, because the sound path difference in the lens, the variation on the phase place appearred in sound wave, and this moment, the effect of lens was equivalent to phase transformer.Suppose that sound wave presses spherical wave decay in lens, then arrive the acoustic pressure P on the lens curved surface ₂For:

${\mathrm{<figure-callout\; id="2"\; label="P"\; filenames="A20061004054300072.png"\; state="\{\{state\}\}">P</figure-callout>}}_2=\frac{{\mathrm{<figure-callout\; id="0"\; label="p"\; filenames="A20061004054300072.png"\; state="\{\{state\}\}">p</figure-callout>}}_0\exp \left({\mathrm{jw}}_0(t-\frac{r(1-\cos \mathrm{\&theta;})}{c_1})\right)}{r(1-\cos \mathrm{\&theta;})}---\left(2\right)$

In the formula, r is the radius-of-curvature of lens; c ₁Be the velocity of sound in the lens material.

Point on the lens curved surface as the secondary point source, is outwards launched spherical wave, do not consider the mutual interference between them, then (x, y z) locate 1 M in space, by the sound wave P that a bit is transmitted into this point on the lens curved surface ₃For:

${\mathrm{<figure-callout\; id="3"\; label="P"\; filenames="A20061004054300082.png"\; state="\{\{state\}\}">P</figure-callout>}}_3=\frac{{\mathrm{<figure-callout\; id="0"\; label="p"\; filenames="A20061004054300072.png"\; state="\{\{state\}\}">p</figure-callout>}}_0\exp \left({\mathrm{jw}}_0(t-\frac{r(1-\cos \mathrm{\&theta;})}{c_1}-\frac{R}{c_2})\right)}{r(1-\cos \mathrm{\&theta;})R}---\left(3\right)$

Wherein,

$R=\sqrt{{(x-x_1)}^2+{(y-y_1)}^2+{(z-r(1-\cos \mathrm{\&theta;}))}^2},$ Point (x ₁, y ₁, r (1-cos θ)) and be the point on the lens curved surface.c ₂It is the velocity of sound (water intaking is medium in the test) in the space medium.

Any acoustic pressure of space can be regarded as the stack of point sources all on the lens curved surface in the acoustic pressure of this point radiation.For this reason, on lens curved surface, get an infinitesimal ds, ds=rdxd θ, then infinitesimal to the acoustical signal of some radiation in space is:

$\mathrm{dp}=\frac{{\mathrm{<figure-callout\; id="0"\; label="rp"\; filenames="A20061004054300072.png"\; state="\{\{state\}\}">rp</figure-callout>}}_0\exp ({\mathrm{jw}}_0(t-\frac{r(1-\cos \mathrm{\&theta;})}{c_1})-\frac{R}{c_2})}{r(1-\cos \mathrm{\&theta;})R}\mathrm{dxd\&theta;}---\left(4\right)$

Along the lens curved surface integration, just can obtain 1 M in space (acoustic pressure of z) locating is for x, y:

$P={\&Integral;}_{-b}^b{\&Integral;}_{-\arcsin (a/r)}^{\arcsin (a/r)}\frac{p_0}{(1-\cos \mathrm{\&theta;})R}$

$\&times;\exp \left({\mathrm{jw}}_0(t-\frac{r(1-\cos \mathrm{\&theta;})}{c_1}-\frac{R}{c_2})\right)\mathrm{dxd\&theta;}---\left(5\right)$

Formula (5) is exactly the sound field distribution mathematical model of line focus ultrasonic probe in the space.

2) sound field is found the solution

The exact solution that (5) formula of directly finding the solution obtains the sound field distribution is the comparison difficulty.Adopt approximate method to calculate this integration.Lens are divided into the M equal portions by length direction, again its direction by the θ angle are divided into the N equal portions.Then lens curved surface can be divided into M * N fritter, any acoustic pressure of space can be regarded the acoustic pressure stack of these fritters emissions as.As long as M and N are abundant, can satisfy computational accuracy and require.

Getting lens material is organic glass, and wherein the velocity of sound is 2700m/s, and the velocity of sound in the water is 1500m/s, and the radius-of-curvature of lens is 15mm, and lens are long to be 7mm, and wide is 7mm, and the ultrasound wave centre frequency is 5MHz.Calculate through programming, the acoustic pressure on its center line (z direction of principal axis) distributes as shown in Figure 3.This moment, the distance of maximum sound pressure correspondence was 31mm, and promptly the theoretical focal length of this probe is about 31mm.

Axis sound field to this type sensor in water has been carried out actual test, dotted line among result such as Fig. 3.

3) line focus sonac acoustic beam angle

The acoustic beam angle synoptic diagram of line focus sonac emission sound wave as shown in Figure 4.Among the figure, f is a sensor focal distance, and 2a is the sensor wafer width, and 2 α are focused beam angles.

According to sensor acoustic beam geometric representation, can get

$\mathrm{tg}\left(\mathrm{\&alpha;}\right)=\frac{a}{f}---\left(6\right)$

Then,

$\mathrm{\&alpha;}=\mathrm{arctg}\left(\frac{a}{f}\right)---\left(7\right)$

Claims (1)

1, a kind of immersion type line focus sound-field model of playing sonic transducer is set up process and method for solving mainly comprises following concrete steps:

Modelling mainly comprises:

1) design feature according to real sensor takes out its physical model, and wherein, piezoelectric chip and sound lens are the main bodys of physical model; Piezoelectric chip is adopted rectangular geometries simulation, and be planar rectangular with sound lens with a side, opposite side is that the columniform geometry of part is simulated;

2) set up two cover coordinate systems on physical model, a cover coordinate system is a rectangular coordinate system, and in the heart, the x axle is along the length of lens direction in the sound lens back side for initial point, and the y axle is along the lens height direction, and the z axle is perpendicular to lens tool back plane (xoy face); One cover coordinate system is a cylindrical coordinate system, and the right cylinder geometric center of getting inner lens surfaces is as initial point, and r is the radius-of-curvature of lens, and θ is the projection of point on the yoz plane and the angle of z axle positive dirction on the lens curved surface;

3) piezoelectric chip is divided into series of rectangular infinitesimal ds ₁, each ds ₁Be used as a point sound source, outwards launch spherical wave;

4) effect with lens is equivalent to phase transformer, and the point on the sound lens curved surface is regarded as the secondary point source, also outwards launches spherical wave;

5) the sound lens curved surface is divided into a series of infinitesimal ds ₂, the acoustic pressure at space any point place equals the result of all these secondary infinitesimal emitting sound wave in this some stack, thereby has obtained the sound-field model P of this type sensor; Work as x=0, during y=0, the acoustic pressure that obtains on the sensor axis distributes; The acoustic pressure maximum point is a focal length on the axis; Obtain its acoustic beam angle α according to focal length;

The numerical solution of model comprises:

6) adopt numerical method that the sensor sound field is found the solution; The concrete practice is that lens are divided into enough little zone, with the integration in the superposition approximation sound-field model of zonule sound field.

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