CN102853791A - Method for scanning ultrasonic microscope and measuring thickness, sound velocity, density and attenuation of thin material simultaneously - Google Patents

Abstract

The invention discloses a method for scanning ultrasonic microscope and measuring thickness, sound velocity, density and attenuation of a thin material simultaneously. The method includes: 1) the thin material is placed on the surface of a base material, an ultrasonic probe is located right above the base material and the thin material, ultrasonic echo signals s1 (t) and s2 (t) of the base material and the thin material are obtained; 2) deconvolution based on the wiener filtering and autoregressive spectral extrapolation technique is performed on the s2 (t) to obtain a signal h1 (t), and an initial value of acoustic transition time is selected; 3) initial values of other variables are selected, reflection coefficient frequency spectrum of the thin material is matched to obtain optimal values of acoustic impedance, acoustic transition time and acoustic attenuation coefficient of the thin material; 4) deconvolution based on the wiener filtering and autoregressive spectral extrapolation technique is performed on s1 (t)+s2 (t); and 5) the thickness, the sound velocity, the density and the attenuation of the thin material are calculated. Four-variable high-accuracy simultaneous measurement of the thin material can be achieved, and the problem of convergence domain is solved when the frequency spectrum is matched.

Description

The scanning ultrasonic microscope is measured the method for layer material thickness, the velocity of sound, density and decay simultaneously

Technical field

The present invention relates to the layer material feature measurement field based on the scanning ultrasonic microscope, particularly a kind ofly scan the method that ultrasonic microscope is measured layer material thickness, the velocity of sound, density and decay simultaneously.

Background technology

Scanning ultrasonic microscope (SAM:Scanning Acoustic Microscope) is widely used in Non-Destructive Testing and the assessment of the Key Electron Device and precision mechanical part, also is widely used in the microscopic observation of biological tissue simultaneously.

At present, (high, wear-resisting, corrosion-resistant such as intensity, good heat dissipation etc.) all is widely used in fields such as chemical industry, machine-building, the energy, aviations the layer material such as film, coating because its unique character.The diamond thin that for example is attached to tool surface can improve the cutting ability of cutter effectively because of its high rigidity and chemical stability.Yet, in the process of the layer materials such as film, coating, must guarantee stability and the consistance of material behavior, therefore be necessary these layer materials are carried out the measurement of thickness and Young modulus etc.At present the nondestructive measurement of mechanical property mainly adopted ultrasonic method.

Ripe scanning ultrasonic microscope product is mainly used in the ultrasonic imaging aspect at present on the market, and is not deep for the application in the measurement of the geometry of material and mechanical property, especially the ultrasound wave of thickness, the velocity of sound, density and decay measured simultaneously.The research of this respect measuring method mainly concentrates on colleges and universities and research institute.

Utilize the earliest surface wave method that material behavior is measured abroad.Because the dispersion curve of surface wave is relevant with thickness, the velocity of sound of layer material, so the research of his-and-hers watches ground roll helps contrary thickness and the velocity of sound of separating layer material.But the limitation of this mode is to obtain simultaneously density and the decay of material, and the dispersion curve of surface wave just has preferably sensitivity at high band very, therefore the bandwidth of ultrasound emission receiver is put forward very high requirement.In recent years research, the especially research for layer material of material behavior are mainly concentrated on the mode of using ultrasonic spectrum.Because the ultrasonic echo of layer material because upper and lower surface echo and round trip echoes aliasing occurs in time domain, is difficult to differentiate and draw the parameter of wanting, so the ultrasonic spectrum analytic approach is the main method for layer material.

The researchist of Ohio State Univ-Columbus USA utilizes the mode of straight incident ultrasonic probe and the combination of oblique incidence ultrasonic probe to realize the measurement of thickness, the velocity of sound, density and the decay of thin layer aluminium sheet, but this equipment need to be used three ultrasonic probes and angle-adjusting mechanism, and whole measurement mechanism is comparatively complicated and heavy.

Dalian University of Technology has adopted at the Non-Destructive Testing center in recent years based on the thickness of vertical incidence reflection coefficient spectrum data fitting, the measurement of the velocity of sound, but must be under density and the known condition that decays.For density and the unknown material of decay, this mode can't be measured.

The German adopted the method for focusing probe to carry out the measurement of material thickness, the velocity of sound and density in recent years.Utilize the focus characteristics of focusing probe, respectively ultrasound wave is focused on upper surface and the lower surface of material, then obtain simultaneously thickness, the velocity of sound and density according to theoretical calculation formula.But the limitation of this method is only can't to measure for layer material to measure the material of the non-aliasing of time domain material equally.

The people such as France Hosten have proposed to measure in the mode of time domain and frequency-domain combined analysis thickness, the velocity of sound, density and the decay of plate.In time domain, utilize the thickness of determining plate with reference to the velocity of sound in the echoed signal of matrix and the water, utilize the velocity of sound of first surface echo and definite material of the transit time between the second surface echo of sample, by density and decay are determined in the frequency-domain analysis of sample first surface echo and second surface echo, also can carry out the optimization match by the reflection coefficient spectrum and come contrary solve density and decay at last.But the limitation of this method is that it is only applicable to the material of the non-aliasing of time-domain signal (being that thickness is thicker).For layer material, the time-domain signal aliasing causes thickness and the velocity of sound to measure.They have also adopted the method for traditional reflection coefficient Spectrum Fitting to come the contrary characteristic that solves layer material, be subjected to initial value to choose the restriction of quality but be based on the contrary solution procedure of least square method under then, initial value is chosen bad will causing and is converged to other extreme points.

The traditional experiment measuring that passes through sample reflection coefficient frequency spectrum and theoretical spectrum carry out least square fitting, can draw transit time, acoustic impedance and the attenuation coefficient of layer material.

The ultrasonic reflection coefficient spectrum theoretical expression that is immersed in the layer material in the water is:

$R_t\left(\mathrm{\&omega;}\right)=\frac{R_{01}(1-\exp \left(\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="120223155018.png,120223155021.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&omega;}\stackrel{\&OverBar;}{h}\right)\&CenterDot;\exp (-2\mathrm{\&omega;\&alpha;}\stackrel{\&OverBar;}{h}))}{1-R_{01}^2\&CenterDot;\exp \left(\mathrm{<figure-callout\; id="2"\; label="j"\; filenames="120223155018.png,120223155021.png"\; state="\{\{state\}\}">j</figure-callout>}2\mathrm{\&omega;}\stackrel{\&OverBar;}{h}\right)\&CenterDot;\exp (-2\mathrm{\&omega;\&alpha;}\stackrel{\&OverBar;}{h})}---\left(1\right)$

, wherein, R ₀₁=(Z _s-Z ₀)/(Z _s+ Z ₀), Z _s=ρ ₁c ₁And Z ₀=ρ ₀c ₀Be respectively the acoustic impedance of layer material and water, ρ ₁And ρ ₀Be the density of layer material and water, c ₁And c ₀Be the velocity of sound in layer material and the water,

Be the transit time of sound wave in layer material, α is the acoustic attenuation coefficient in the layer material.

The method that layer material reflection coefficient frequency spectrum is surveyed in experiment is: the echoed signal of difference witness mark material and the echoed signal s of specimen material ₁(t) and s ₂And be converted into corresponding spectrum H (t), ₁(ω) and H ₂(ω), reference material is generally matrix material, and namely thickness is much larger than the material of ultrasound wave wavelength, and generally selecting stainless steel is with reference to matrix material, its reflection R ₁Be about 0.936, be constant.And layer material is because the interference between the multiple reflection echo has caused its reflection coefficient frequency spectrum R _e(ω) vibration appears.If the whole transport function of ultrasound wave transceiver is H ₀(ω), then:

H ₁(ω)＝H ₀(ω)R ₁ (2)

H ₂(ω)＝H ₀(ω)R _e(ω) (3)

So the experiment value of the reflection coefficient frequency spectrum of layer material is: R _e(ω)=R ₁H ₂(ω)/H ₁(ω).The velocity of sound of water, acoustic impedance, density is as known quantity, so the theoretical expression of reflection coefficient frequency spectrum depends on acoustic impedance, transit time and the attenuation coefficient of layer material fully, can be worth by experiment R _e(ω) and R _tLeast square fitting (ω) draws the value of layer material acoustic impedance, transit time and attenuation coefficient.

Choose bad and cause convergence less than actual value but initial value appears in above-mentioned traditional least square fitting easily, contrary solution procedure failure.The domain of convergence of transit time is very narrow, and a given suitable initial value is extremely important when therefore carrying out least square fitting for layer material.

Learn that to sum up measurement is still a difficult problem when will satisfy simultaneously the thickness, density, the velocity of sound of layer material and decay, the whole bag of tricks all has deficiency.Therefore in conjunction with above domestic and international research background, measuring method is particularly necessary when introducing Deconvolution Technique and develop a kind of simple, thickness of being directed to layer material, density, the velocity of sound and decay.

Summary of the invention

The objective of the invention is to overcome the deficiencies in the prior art, propose a kind of scanning ultrasonic microscope that utilizes and measure simultaneously the method for thickness, density, the velocity of sound and the decay of layer material.

The scanning ultrasonic microscope is measured layer material thickness simultaneously, the velocity of sound, the method of density and decay, adopt the scanning ultrasonic microscope, the scanning ultrasonic microscope comprises ultrasonic probe, the 3 d-line motor, guide rail, matrix material, layer material, tank, electric machine controller, ultrasonic transmitter-receiver, computing machine, display, bottom of gullet is placed with matrix material, matrix material is provided with layer material, the matrix material top is provided with ultrasonic probe, the ultrasonic probe upper end links to each other with the 3 d-line motor, guide rail is provided with the 3 d-line motor, ultrasonic probe links to each other with ultrasonic transmitter-receiver, the 3 d-line motor links to each other with electric machine controller, computing machine respectively with electric machine controller, ultrasonic transmitter-receiver, display links to each other; The step of method is as follows:

1) layer material is positioned over substrate material surface, and places the tank that fills water, open the scanning ultrasonic microscope;

2) y-axis motor of the 3 d-line motor of adjusting scanning ultrasonic microscope is positioned at directly over the matrix material ultrasonic probe, measures the ultrasonic echo signal s of substrate material surface ₁(t);

3) search out the part that layer material stretches out substrate material surface, it is layer material upper and lower surface part fully under water, and the y-axis motor of regulating the 3 d-line motor of scanning ultrasonic microscope make ultrasonic probe be positioned at this part of layer material directly over, measure the ultrasonic echo signal s of layer material ₂(t);

4) with s ₁(t) be reference signal, to s ₂(t) carry out deconvolution based on Wiener filtering and autoregressive spectrum extrapolation technique, obtain signal h ₁(t);

5) record h ₁(t) the separation delta t between per two peak-to-peak values in the signal ₁, and with Δ t ₁/ 2 are set as the initial value of the sound wave transit time of layer material (5)

6) choose again the initial value α of the acoustic attenuation coefficient of layer material ₀Initial value Z with acoustic impedance _S0, by layer material being carried out the least square fitting of reflection coefficient frequency spectrum, draw the optimal value Z of acoustic impedance, sound wave transit time and the acoustic attenuation coefficient of layer material _s,

And α.

7) with s ₁(t) be reference signal, to s ₁(t)+s ₂(t) carry out deconvolution based on Wiener filtering and autoregressive spectrum extrapolation technique, obtain signal h ₂(t) and record h ₂(t) the separation delta t between the first two peak-to-peak value in the signal ₂

8) thickness that calculates layer material is h=c ₀Δ t ₂/ 2, c wherein ₀Be the speed of underwater acoustic wave, the velocity of sound of layer material is Density is ρ=Z _s/ c ₁, attenuation coefficient is α.

Described step 6) be:

The initial value Z of acoustic impedance, sound wave transit time and the acoustic attenuation coefficient of selected layer material _S0,

And α ₀Afterwards, the ultrasonic reflection coefficient frequency spectrum R of the theory of computation _t(ω); Then with s ₂(t) frequency spectrum of signal is divided by s ₁(t) frequency spectrum of signal multiply by the value R of matrix reflection coefficient again ₀, obtain the experiment value R of the reflection coefficient frequency spectrum of layer material _e(ω); Get objective function

Wherein n is the number of sampled point in the reflection coefficient spectral bandwidth; From three initial value Z _S0,

And α ₀Begin, utilize the minimum value f of the optimization function f of Gauss-Newton method searching _Min, draw the optimal value Z of acoustic impedance, sound wave transit time and the acoustic attenuation coefficient of layer material _s,

And α.

The beneficial effect that the present invention compared with prior art has:

Measure when 1) being applicable to the thickness, the velocity of sound, density of layer material and four variablees of decay.Although simultaneously detect thickness, the velocity of sound, density and decay that prior art has, but the layer material for the time domain waveform aliasing is helpless, although what have can measure layer material, measure when can not reach this four variablees of thickness, the velocity of sound, density and decay;

2) introduce Deconvolution Technique so that the initial value of thickness, the velocity of sound is chosen very accurately, avoided when using that least square fitting is contrary asks four variablees the convergence problem that cause because initial value chooses bad.

Description of drawings

Fig. 1 measures matrix echoed signal synoptic diagram with the scanning ultrasonic microscope;

Fig. 2 is immersed in sample echoed signal synoptic diagram in the water with scanning ultrasonic microscope measurement;

Fig. 3 carries out result after the deconvolution take the matrix material echo as reference signal to the layer material echo;

Fig. 4 is reflection coefficient Spectrum Fitting empirical curve and the theoretical curves afterwards of layer material;

Fig. 5 is matrix material echoed signal and the signal of layer material echoed signal after the time domain stack;

Fig. 6 carries out result after the deconvolution take the matrix material echo as reference signal to the signal after the stack of layer material echo and matrix material echo.

Embodiment

The scanning ultrasonic microscope is measured layer material thickness simultaneously, the velocity of sound, the method of density and decay, adopt the scanning ultrasonic microscope, the scanning ultrasonic microscope comprises ultrasonic probe 1,3 d-line motor 2, guide rail 3, matrix material 4, layer material 5, tank 6, electric machine controller 7, ultrasonic transmitter-receiver 8, computing machine 9, display 10, tank 6 bottoms are placed with matrix material 4, matrix material 4 is provided with layer material 5, matrix material 4 tops are provided with ultrasonic probe 1, ultrasonic probe 1 upper end links to each other with 3 d-line motor 2, guide rail 3 is provided with 3 d-line motor 2, ultrasonic probe 1 links to each other with ultrasonic transmitter-receiver 8,3 d-line motor 2 links to each other with electric machine controller 7, computing machine 9 respectively with electric machine controller 7, ultrasonic transmitter-receiver 8, display 10 links to each other; The step that it is characterized in that method is as follows:

1) layer material 5 is positioned over matrix material 4 surfaces, and places the tank 6 that fills water, open the scanning ultrasonic microscope;

2) y-axis motor of the 3 d-line motor 2 of adjusting scanning ultrasonic microscope is positioned at directly over the matrix material 4 ultrasonic probe 1, measures the ultrasonic echo signal s on matrix material 4 surfaces ₁(t), with s ₁(t) conduct is with reference to signal, and this signal is relevant with the characteristic of whole ultrasound measurement system;

3) search out the part that layer material 5 stretches out matrix material 4 surfaces, be layer material 5 upper and lower surfaces parts fully under water, and the y-axis motor of regulating the 3 d-line motor 2 of scanning ultrasonic microscope make ultrasonic probe 1 be positioned at layer material 5 these parts directly over, measure the ultrasonic echo signal s of layer material 5 ₂(t), this signal is sample signal, and is not only relevant with the characteristic of whole ultrasound measurement system, also relevant with the character of sample itself;

4) with s ₁(t) be reference signal, to s ₂(t) carry out deconvolution based on Wiener filtering and autoregressive spectrum extrapolation technique, obtain signal h ₁(t), specific practice is as follows:

With s ₁(t) and s ₂(t) carry out respectively Fourier transform and obtain S ₁(ω) and S ₂(ω), obtain deconvolution frequency spectrum afterwards according to Wiener filtering:

$H\left(\mathrm{\&omega;}\right)=\frac{S_2\left(\mathrm{\&omega;}\right)\&CenterDot;{\mathrm{<figure-callout\; id="1"\; label="S"\; filenames="120223155021.png"\; state="\{\{state\}\}">S</figure-callout>}}_1^{*}\left(\mathrm{\&omega;}\right)}{{\left|S_1\left(\mathrm{\&omega;}\right)\right|}^2+S_n\left(\mathrm{\&omega;}\right)/S_H\left(\mathrm{\&omega;}\right)}---\left(4\right)$

, S wherein ₁ ^*(ω) be S ₁Conjugate complex number spectrum (ω), S _n(ω) and S _H(ω) be respectively the power spectral density function of noise signal n (t) and the required signal h (t) that obtains, usually S _n(ω)/S _H(ω) get

Then H (ω) is added rectangular window and choose one section the highest frequency spectrum of its signal to noise ratio (S/N ratio) and discretize (starting point of ω and terminal point index value are respectively m and n), this section frequency spectrum is carried out the autoregressive spectrum extrapolation, obtain remaining frequency range (1 to m according to the Burg algorithm, n+1 is to N, and N is the Nyquist frequency) estimated value of upper H (ω):

Deconvolution Signal spectrum H after the value formation of H (ω) is widened in the estimated value that will be obtained by autoregressive spectrum extrapolation and the rectangular window ' (ω) (ω) is carried out signal h after inverse Fourier transform obtains deconvolution to H ' ₁(t);

5) h ₁(t) be the signal of a series of one-tenth " spike " shape in the signal, representing successively upper surface echo, lower surface echo and inner multiple reflection echo after ultrasound wave incides layer material, record h ₁(t) the separation delta t between per two peak-to-peak values in the signal ₁, and with Δ t ₁/ 2 are set as the initial value of the sound wave transit time of layer material 5 , because used deconvolution can be carried out good differentiation with the time domain aliasing signal, therefore can make reasonable initial estimation to the transit time of layer material;

6) because attenuation coefficient and acoustic impedance only have an extreme point in domain of convergence, so the convergence result is not affected by initial value, choose again the initial value α of the acoustic attenuation coefficient of layer material 5 ₀Initial value Z with acoustic impedance _S0, by layer material 5 being carried out the least square fitting of reflection coefficient frequency spectrum, draw the optimal value Z of acoustic impedance, sound wave transit time and the acoustic attenuation coefficient of layer material 5 _s,

And α.

7) with similar step 4) in method, with s ₁(t) be reference signal, to s ₁(t)+s ₂(t) carry out deconvolution based on Wiener filtering and autoregressive spectrum extrapolation technique, obtain signal h ₂(t) and record h ₂(t) the separation delta t between the first two peak-to-peak value in the signal ₂

8) thickness that calculates layer material 5 is h=c ₀Δ t ₂/ 2, c wherein ₀Be the speed of underwater acoustic wave, the velocity of sound of layer material 5 is

Density is ρ=Z _s/ c ₁, attenuation coefficient is α.

Described step 6) be:

The initial value Z of acoustic impedance, sound wave transit time and the acoustic attenuation coefficient of selected layer material 5 _S0,

And α ₀Afterwards, according to the ultrasonic reflection coefficient frequency spectrum R of formula (1) theory of computation _t(ω); Then with s ₂(t) frequency spectrum of signal is divided by s ₁(t) frequency spectrum of signal multiply by the value R of matrix reflection coefficient again ₀, obtain the experiment value R of the reflection coefficient frequency spectrum of layer material 5 _e(ω); Get objective function Wherein n is the number of sampled point in the reflection coefficient spectral bandwidth; From three initial value Z _S0,

And α ₀Begin, utilize the minimum value f of the optimization function f of Gauss-Newton method searching _Min, draw the optimal value Z of acoustic impedance, sound wave transit time and the acoustic attenuation coefficient of layer material 5 _s,

And α.

Below in conjunction with embodiment the present invention is further specified.

1) aluminium sheet is elected to be tested layer material, its basic parameter is as shown in table 1.It is positioned over the surface of stainless steel base material, and places the tank that fills water, structure is as shown in Figure 1 placed sample, then opens the scanning ultrasonic microscope;

Table 1: the actual value of the thickness of aluminium sheet, the velocity of sound, density and decay

2) as shown in Figure 1, the y-axis motor of regulating the three-dimensional motor of scanning ultrasonic microscope is positioned at directly over the stainless steel base material ultrasonic probe, measures the ultrasonic echo signal s of stainless steel base material surface ₁(t), with s ₁(t) conduct is with reference to signal, and this signal is relevant with the characteristic of whole ultrasound measurement system;

3) as shown in Figure 2, search out the part that aluminium sheet stretches out stainless steel-based surface, be upper and lower surface part fully under water, and the y-axis motor of regulating the three-dimensional motor of scanning ultrasonic microscope is positioned at directly over it ultrasonic probe, measures the ultrasonic echo signal s of aluminium sheet ₂(t), this signal is sample signal, and is not only relevant with the characteristic of whole ultrasound measurement system, also relevant with the character of sample itself;

4) with s ₁(t) be reference signal, to s ₂(t) carry out deconvolution based on Wiener filtering and autoregressive spectrum extrapolation technique, obtain signal h ₁(t), specific practice is as follows:

With s ₁(t) and s ₂(t) carry out respectively Fourier transform and obtain S ₁(ω) and S ₂(ω), obtain deconvolution frequency spectrum afterwards according to Wiener filtering:

$H\left(\mathrm{\&omega;}\right)=\frac{S_2\left(\mathrm{\&omega;}\right)\&CenterDot;{\mathrm{<figure-callout\; id="1"\; label="S"\; filenames="120223155021.png"\; state="\{\{state\}\}">S</figure-callout>}}_1^{*}\left(\mathrm{\&omega;}\right)}{{\left|S_1\left(\mathrm{\&omega;}\right)\right|}^2+S_n\left(\mathrm{\&omega;}\right)/S_H\left(\mathrm{\&omega;}\right)}---\left(7\right)$

, S wherein ₁ ^*(ω) be S ₁Conjugate complex number spectrum (ω), S _n(ω) and S _H(ω) be respectively the power spectral density function of noise signal n (t) and the required signal h (t) that obtains, usually S _n(ω)/S _H(ω) get

Then H (ω) is added rectangular window and choose one section the highest frequency spectrum of its signal to noise ratio (S/N ratio) and discretize (starting point of ω and terminal point index value are respectively m and n), this section frequency spectrum is carried out the autoregressive spectrum extrapolation, obtain remaining frequency range (1 to m according to the Burg algorithm, n+1 is to N, and N is the Nyquist frequency) estimated value of upper H (ω):

Deconvolution Signal spectrum H after the value formation of H (ω) is widened in the estimated value that will be obtained by autoregressive spectrum extrapolation and the rectangular window ' (ω) (ω) is carried out signal h after inverse Fourier transform obtains deconvolution to H ' ₁(t), the h that obtains ₁(t) signal as shown in Figure 3;

5) h ₁(t) be the signal of a series of one-tenth " spike " shape in the signal, representing successively upper surface echo, lower surface echo and inner multiple reflection echo after ultrasound wave incides aluminium sheet.Record h ₁(t) the separation delta t between per two peak-to-peak values in the signal ₁, know Δ t by Fig. 3 ₁=0.159 μ s.With Δ t ₁/ 2=0.0795 μ s is set as the initial value of the sound wave transit time of aluminium sheet Because used deconvolution can be carried out good differentiation with the time domain aliasing signal, therefore can make reasonable initial estimation to the transit time of layer material;

6) because attenuation coefficient and acoustic impedance only have an extreme point in domain of convergence, so the convergence result is not affected by initial value, choose again the initial value α of the acoustic attenuation coefficient of aluminium sheet ₀=0.08 and the initial value Z of acoustic impedance _S0=7.4 * 10 ⁷, calculate theoretical ultrasonic reflection coefficient frequency spectrum R according to formula (1) _t(ω); Then with s ₂(t) spectrum H of signal ₂(ω) divided by s ₁(t) spectrum H of signal ₁(ω) multiply by again the value R of matrix reflection coefficient ₁, obtain the experiment value R of the reflection coefficient frequency spectrum of aluminium sheet _e(ω), as shown in phantom in Figure 4; Get objective function

Wherein n is the number of sampled point in the reflection coefficient spectral bandwidth; From three initial value Z _S0,

And α ₀Z is constantly updated in beginning _s,

The value of α is also utilized the minimum value f of the optimization function f that Gauss-Newton method seeks _Min, draw the optimal value Z of acoustic impedance, sound wave transit time and the acoustic attenuation coefficient of aluminium sheet _s=1.665 * 10 ⁷,

And α=0.0047, theoretical ultrasonic reflection coefficient frequency spectrum is shown in solid line among Fig. 4 at this moment.

7) with s ₁(t) be reference signal, use and step 4) in same method to s ₁(t)+s ₂(t) (as shown in Figure 5) carry out the deconvolution based on Wiener filtering and autoregressive spectrum extrapolation technique, obtain signal h ₂(t) (as shown in the figure) and record h ₂(t) the separation delta t between the first two peak-to-peak value in the signal ₂=0.65 μ s;

8) thickness that calculates aluminium sheet is h=c ₀Δ t ₂/ 2=481 μ m, wherein c ₀=1480 μ m/ μ s are the speed of underwater acoustic wave, and the velocity of sound of aluminium sheet is

Density is ρ ₁=Z _s/ c ₁=2652kg/m ³, attenuation coefficient is α=0.0047, and is as shown in table 2, the error of thickness, the velocity of sound, density and attenuation coefficient measured value is followed successively by: 5.0%, 1.1%, 1.8%, 2.1%.

Table 2: the measured value of aluminium plate thickness, the velocity of sound, density and decay and relative error

Claims (2)

1. a scanning ultrasonic microscope is measured layer material thickness simultaneously, the velocity of sound, the method of density and decay, adopt the scanning ultrasonic microscope, the scanning ultrasonic microscope comprises ultrasonic probe (1), 3 d-line motor (2), guide rail (3), matrix material (4), layer material (5), tank (6), electric machine controller (7), ultrasonic transmitter-receiver (8), computing machine (9), display (10), tank (6) bottom is placed with matrix material (4), matrix material (4) is provided with layer material (5), matrix material (4) top is provided with ultrasonic probe (1), ultrasonic probe (1) upper end links to each other with 3 d-line motor (2), guide rail (3) is provided with 3 d-line motor (2), ultrasonic probe (1) links to each other with ultrasonic transmitter-receiver (8), 3 d-line motor (2) links to each other with electric machine controller (7), computing machine (9) respectively with electric machine controller (7), ultrasonic transmitter-receiver (8), display (10) links to each other; The step that it is characterized in that method is as follows:

1) layer material (5) is positioned over matrix material (4) surface, and places the tank (6) that fills water, open the scanning ultrasonic microscope;

2) y-axis motor of the 3 d-line motor (2) of adjusting scanning ultrasonic microscope is positioned at directly over the matrix material (4) ultrasonic probe (1), measures the ultrasonic echo signal s on matrix material (4) surface ₁(t);

3) search out the part that layer material (5) stretches out matrix material (4) surface, it is layer material (5) upper and lower surface part fully under water, and the y-axis motor of regulating the 3 d-line motor (2) of scanning ultrasonic microscope make ultrasonic probe (1) be positioned at this part of layer material (5) directly over, measure the ultrasonic echo signal s of layer material (5) ₂(t);

4) with s ₁(t) be reference signal, to s ₂(t) carry out deconvolution based on Wiener filtering and autoregressive spectrum extrapolation technique, obtain signal h ₁(t);

5) record h ₁(t) the separation delta t between per two peak-to-peak values in the signal ₁, and with Δ t ₁/ 2 are set as the initial value of the sound wave transit time of layer material (5)

6) choose again the initial value α of the acoustic attenuation coefficient of layer material (5) ₀Initial value Z with acoustic impedance _S0, by layer material (5) being carried out the least square fitting of reflection coefficient frequency spectrum, draw the optimal value Z of acoustic impedance, sound wave transit time and the acoustic attenuation coefficient of layer material (5) _s,

And α.

7) with s ₁(t) be reference signal, to s ₁(t)+s ₂(t) carry out deconvolution based on Wiener filtering and autoregressive spectrum extrapolation technique, obtain signal h ₂(t) and record h ₂(t) the separation delta t between the first two peak-to-peak value in the signal ₂

8) thickness that calculates layer material (5) is h=c ₀Δ t ₂/ 2, c wherein ₀Be the speed of underwater acoustic wave, the velocity of sound of layer material (5) is

Density is ρ=Z _s/ c ₁, attenuation coefficient is α.

2. described a kind of method that ultrasonic microscope is measured layer material thickness, the velocity of sound, density and decay simultaneously that scans according to claim 1 is characterized in that described step 6) be:

The initial value Z of acoustic impedance, sound wave transit time and the acoustic attenuation coefficient of selected layer material (5) _S0,

And α ₀Afterwards, the ultrasonic reflection coefficient frequency spectrum R of the theory of computation _t(ω); Then with s ₂(t) frequency spectrum of signal is divided by s ₁(t) frequency spectrum of signal multiply by the value R of matrix reflection coefficient again ₀, obtain the experiment value R of the reflection coefficient frequency spectrum of layer material (5) _e(ω); Get objective function

Wherein n is the number of sampled point in the reflection coefficient spectral bandwidth; From three initial value Z _S0,

And α ₀Begin, utilize the minimum value f of the optimization function f of Gauss-Newton method searching _Min, draw the optimal value Z of acoustic impedance, sound wave transit time and the acoustic attenuation coefficient of layer material (5) _s,

And α.

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