CN101692072A - Calculation method of sound field of circular arc-shaped linear ultrasonic phased array - Google Patents

Abstract

The invention provides a calculation method of the sound field of a circular arc-shaped linear ultrasonic phased array, comprising a beam control focusing algorithm, a sound field calculation method and the influence of structural parameters on sound field characteristics. The calculation method uses an angle method to show the position information of an energy converter array element so as to deduct the beam control focusing algorithm of a circular arc shape linear phased array energy converter; a circular array element is similar to a rectangular array element and is combined with coordinate conversion to calculate the sound field of the circular arc-shaped linear phased array; the method is performed with simulation verification respectively by Reily integration and non-paraxial approximation multi-Gaussian models, and the obtained result is very identical. In addition, the calculation method analyzes the influence of structural parameters on sound field characteristics and provides theoretical basis for designing and optimizing the energy converter.

Description

Calculation method of sound field of circular arc-shaped linear ultrasonic phased array

One, technical field

The present invention relates to is a kind of calculation method of sound field of circular arc-shaped linear ultrasonic phased array, and this method provides theoretical foundation for the array energy transducer of design and research special shape.

Two, technical background

In Ultrasonic Detection, generally adopt contact measurement method.When the testee surface configuration is on-plane surface, if adopt linear phase controlled array transducer to detect,, contact can not reduce detection sensitivity because matching, can't accurately locate defective.Under these circumstances, be necessary to develop the array energy transducer of special shape to satisfy complicated detection requirement.Because computer technology rapid development, modeling analysis and simulation calculation provide very effective method for developing and analyze transducer performance, can reflect the sound field characteristic of transducer more intuitively, and optimize the structural parameters of transducer.

The circular arc-shaped linear phase array transducer is a kind of curved surface linear phase controlled array transducer simple in structure, and each array element has identical radius-of-curvature, and the positional information of array element is represented easily.And the linear phase controlled array transducer of irregular surface can be approximated to be by a plurality of circular array unit and forms, and different is that circular arc array element has different radius-of-curvature.Therefore, the circular arc-shaped linear phase array transducer is the basis of research and design complicated shape phase array transducer, has important researching value.

Three, summary of the invention

The objective of the invention is in order to overcome when the object of detection of complex surface configuration, the deficiency that linear phase controlled array transducer exists, and a kind of calculation method of sound field of regular surfaces linear phase controlled array transducer is provided, for design with optimize transducer the theoretical reference foundation is provided.

The object of the present invention is achieved like this: it comprises the influence to the phased array sound field of focusing algorithm, calculation method of sound field and the array parameter of the control of circular arc-shaped linear ultrasonic phased array wave beam; The focusing algorithm of described circular arc-shaped linear ultrasonic phased array wave beam control adopts preset angle configuration to represent the positional information of array element, thereby derives the focusing law of wave beam control; Described calculation method of sound field adopts circular arc array element to be approximately the method that rectangle array element and coordinate transform combine, and at first calculates the sound field of single circular arc array element, and then according to Huygens' principle, the sound field of phase array transducer equals the stack of a plurality of array element sound fields; Described array parameter is mainly studied the influence to sound field of array number, array element width and array element distance to the influence of phased array sound field.

Four, description of drawings

Fig. 1 is a circular arc-shaped linear phase array transducer structural representation;

Fig. 2 is the result of calculation in different spatial linear array and circular arc-shaped linear array time delay;

Fig. 3 is a coordinate system transformation;

Fig. 4 is the geometric configuration of single circular arc array element;

Fig. 5 is two-dimensional acoustic field result of calculation (F=20, θ _s=0 °);

Fig. 6 is two-dimensional acoustic field result of calculation (F=20, θ _s=5 °);

Fig. 7 is the asynchronous focusing acoustic field figure of array number;

Fig. 8 is the asynchronous transducer acoustic field of array element width;

Fig. 9 is a transducer deflection focusing sound field;

Figure 10 is the influence of array element height to sound field.

Five, embodiment

For a more detailed description to the present invention for example below in conjunction with accompanying drawing:

In conjunction with Fig. 1, suppose that the circular arc-shaped linear phased array is formed by the linear phase controlled array distortion, according to isometric principle, the aperture D of linear array equals the arc length L of circular arc-shaped linear array

D＝L＝θ _c/180×π×R (1)

Wherein R is a radius-of-curvature, θ _cBe the pairing central angle of the arc length of circular arc-shaped linear array.

In conjunction with Fig. 1, the spacing of the width of circular arc array element and adjacent two array elements is used symbol a respectively _c, d _cExpression, their pairing central angles are defined as θ respectively _aAnd θ _d, the relational expression below satisfying

(N-1)θ _d+θ _a＝θ _c (2)

Wherein N is an array number.I the pairing central angle in array element center is

${\mathrm{\θ}}_i=\frac{{-\mathrm{\θ}}_c+{\mathrm{\θ}}_a}{2}+(i-1){\mathrm{\θ}}_d---\left(3\right)$

Under rectangular coordinate system, the centre coordinate of i array element is: x _i=Rsin θ _i, z _i=R-Rcos θ _i

In conjunction with Fig. 1, according to top condition, in the xoz plane, the computing formula of each array element time delay is

${\mathrm{\τ}}_i=(F-\sqrt{{({F\sin \mathrm{\θ}}_s-{R\sin \mathrm{\θ}}_i)}^2+{({F\cos \mathrm{\θ}}_s+{R\cos \mathrm{\θ}}_i-R)}^2})/c+t$

$=(F-\sqrt{{\mathrm{<figure-callout\; id="2"\; label="F"\; filenames="H2009101483361E0000012.png,H2009101483361E0000021.png"\; state="\{\{state\}\}">F</figure-callout>}}^2+2R^2(1-{\cos \mathrm{\&theta;}}_i)-2\mathrm{FR}\cos {\mathrm{\&theta;}}_s+2\mathrm{FR}\cos ({\mathrm{\&theta;}}_i+{\mathrm{\&theta;}}_s)}{}_{}{}_{})/c+t$

$=F(1-\sqrt{1+2\frac{R^2}{F^2}(1-\cos ){\mathrm{\&theta;}}_i-2\frac{R}{F}\cos {\mathrm{\&theta;}}_s+2\frac{R}{F}\cos ({\mathrm{\&theta;}}_i+{\mathrm{\&theta;}}_s)})/c+t---\left(4\right)$

τ wherein _iBe the time delay of i array element, F is a focal length, θ _sBe deflection angle, c is the speed of ultrasound wave in medium, θ _iIt is the angle between i array element center and the z axle.

When F＞＞during R, τ _i≈ F/c+t.

In conjunction with Fig. 1, the circular arc-shaped linear phase array transducer of forming with 8 circular array units is an example, according to top research method, works as θ _c=60 °, θ _a=4 °, θ _dIn the time of=8 °, the locus is calculated the time delay of linear phase controlled array and each array element of circular arc-shaped linear phased array respectively not simultaneously.

In conjunction with Fig. 2, when the shape of array element and position change, be different the time delay of each array element that calculates at the space point, and the focusing effect that is produced also is different; When the testee surface configuration changes, if still adopt traditional linear array transducer to detect, will influence actual focusing effect, therefore should study new focusing delay algorithm to adapt to different detection requirements according to the situation on testee surface.

Because each array element of circular arc-shaped linear phased array is in same plane, in order to study conveniently, when calculating the acoustic pressure that each array element produces at spatial point P place, the employing coordinate transform is transformed into a P under the new coordinate system and calculates.

In conjunction with Fig. 3, after translation and rotational transform, the new coordinate system (ξ of foundation _iO ' η _i).Wherein true origin o ' is i array element center, η _iAxle is the central axis of i array element.According to geometric relationship, some P conversion formula under new coordinate system is

$\left\{\begin{array}{c}{\mathrm{\&xi;}}_{\mathrm{pi}}=(x_p-x_i)\cos {\mathrm{\&theta;}}_i+(z_p-z_i)\sin {\mathrm{\&theta;}}_i\\ {\mathrm{\&eta;}}_{\mathrm{pi}}=-(x_p-x_i)\sin {\mathrm{\&theta;}}_i+(z_p-z_i)\cos {\mathrm{\&theta;}}_i\end{array}\right.---\left(5\right)$

(x wherein _i, z _i) be the centre coordinate of i array element at former coordinate system, (ξ _Pi, η _Pi) be that some P is at (ξ _iO ' η _i) coordinate under the coordinate system.

In conjunction with Fig. 4, single array element according to the chord length formula, obtains the width a of array element through after the coordinate transform _cWith array element distance d _cFor

a _c＝2Rsin(θ _a/2)，d _c＝2Rsin(θ _d/2)(6)

Work as θ _aWhen very little, sin (θ _a/ 2)～θ _a/ 2, a _c～R θ _a, that is: single circular arc array element can be approximated to be single rectangle array element.

With a radius of curvature R=20mm, central angle θ _c=60 ° of circular arc-shaped linear phased arrays are example, as the centre frequency f of transducer ₀=5MHz, array number N=8, θ _a=4 °, θ _d=7 °, focal length F=20mm, deflection angle is respectively θ _s=5 ° and θ _sThe two-dimensional acoustic field figure of the phase array transducer that=0 ° of employing rayleigh integral (RSI) and non-paraxial approximate (NMG) Model Calculation obtain.

In conjunction with Fig. 5 and Fig. 6, the two-dimensional acoustic field result of calculation that adopts RSI and two kinds of models of NMG to obtain is very identical.

In order to study circular arc-shaped linear phased array elements spacing d _cTo the influence of sound field characteristic, get array element width a _cBe fixed value, i.e. θ _aConstant, by changing array number N, observe the influence of array element distance to acoustic pressure and beam feature.

In conjunction with Fig. 7, with θ _a=3 ° is example, in the xoz plane, when wave beam in (0,20) when locating to focus on, along with the increase of array number N, the acoustic pressure of focusing place increases gradually, main lobe width narrows down, graing lobe is eliminated gradually.Therefore can eliminate graing lobe by increasing the method for array number, strengthen the energy of main lobe.

In conjunction with Fig. 8,, be θ by increasing array element width when array number fixedly the time _a, observe the influence of array element distance and array element width to beam feature and acoustic pressure.When N=10, θ _aWhen getting different values, satisfying θ _a＜θ _dSituation under, increase θ _aNot only can increase acoustic pressure but also can also change beam feature.

In conjunction with Fig. 9, when wave beam during in (5,0,20) point focusing, the sound field energy has obtained enhancing after the wave beam deflection focusing; Increase array element width, the sound field energy also is enhanced.

By last surface analysis, work as θ _dIn the time of＜6 °, can eliminate graing lobe substantially; Under the certain clear condition of array number, can increase the energy that array element width improves sound field.

According to top analysis result, the circular arc-shaped linear phase array transducer of forming with 10 array elements is an example, changes the value of array element height b, observes the change of sound field situation.

In conjunction with Figure 10, when b not simultaneously, adopt the two-dimensional acoustic field of this transducer of NMG Model Calculation; The array element height is also not obvious to the influence of sound field, can consider to select suitable value from the processing and fabricating aspect.

Claims (7)

1. circular arc-shaped linear ultrasonic phased array transducer acoustic field computing method, it comprises the influence to sound field of beam control focusing algorithm, calculation method of sound field and structural parameters.It is characterized in that: the circular arc-shaped linear ultrasonic phased array transducer is formed by a plurality of circular array are first, the position of each array element is not in same plane, in order to derive the focusing algorithm of wave beam control, must adopt new method to represent the position of transducer array element; According to Huygens' principle, when calculating the sound field of circular arc-shaped linear phase array transducer, at first calculate the sound field of single circular arc array element, superpose after postponing accordingly then; The analytical structure parameter comprises the influence to sound field of array element width, array element distance, array number and array element height.

2. method according to claim 1 is characterized in that, the circular arc-shaped linear ultrasonic phased array transducer is formed by the linear ultrasonic phased array transducer distortion.

3. method according to claim 1 is characterized in that: adopt preset angle configuration to represent the position of array element in the array energy transducer, promptly represent with the radius-of-curvature of circular arc-shaped linear phase array transducer and the angle of array element center and z axle.

4. method according to claim 1 is characterized in that: circular arc array element is approximately rectangle array element, and calculates the sound field of single array element in conjunction with coordinate transformation method in newly-established coordinate system.

5. method according to claim 1 is characterized in that: when calculating the sound field of single circular arc array element, each circular arc array element is approximately rectangle array element, and in conjunction with coordinate transformation method, calculates the distribution situation of the whole sound field of transducer.

6. method according to claim 4 is characterized in that: the center with each array element is an initial point, and the central axis of array element is set up new coordinate system for the z axle, with the space arbitrarily any coordinate conversion in new coordinate system, calculate.

7. method according to claim 1 is characterized in that: when analyzing array element width and array element distance to the influencing of circular arc-shaped linear phase array transducer sound field, mainly study the influence of these two pairing central angles of variable to sound field.

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