CN108896664A - The velocity of sound and attenuation coefficient integrated detection method in a kind of polymer - Google Patents

The velocity of sound and attenuation coefficient integrated detection method in a kind of polymer Download PDF

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Publication number
CN108896664A
CN108896664A CN201810573609.6A CN201810573609A CN108896664A CN 108896664 A CN108896664 A CN 108896664A CN 201810573609 A CN201810573609 A CN 201810573609A CN 108896664 A CN108896664 A CN 108896664A
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sample
attenuation coefficient
tested
sound
velocity
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CN108896664B (en
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赵朋
夏能
赵耀
张剑锋
黄俊业
傅建中
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Zhejiang University ZJU
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Zhejiang University ZJU
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/04—Analysing solids
    • G01N29/11—Analysing solids by measuring attenuation of acoustic waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
    • G01N29/04—Analysing solids
    • G01N29/07—Analysing solids by measuring propagation velocity or propagation time of acoustic waves
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/01—Indexing codes associated with the measuring variable
    • G01N2291/011—Velocity or travel time
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/01—Indexing codes associated with the measuring variable
    • G01N2291/015—Attenuation, scattering
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2291/00—Indexing codes associated with group G01N29/00
    • G01N2291/04—Wave modes and trajectories
    • G01N2291/044—Internal reflections (echoes), e.g. on walls or defects

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  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Or Analyzing Materials By The Use Of Ultrasonic Waves (AREA)
  • Length Measuring Devices Characterised By Use Of Acoustic Means (AREA)

Abstract

The invention discloses the velocities of sound in a kind of polymer and attenuation coefficient integrated detection method, which is characterized in that including：(1) ultrasonic probe face sample to be tested is emitted into ultrasonic wave；(2) acquire sample upper and lower surface reflection echo, seek the amplitude spectrum of reflection echo, the side of the sample face ultrasonic probe is defined as upper surface, back to side be lower surface；(3) according to the amplitude spectrum of obtained reflection echo, the attenuation coefficient of the ultrasonic propagation velocity of sample to be tested, the thickness of sample and sample is acquired.Detection method is easy to operate, and convenience of calculation, testing cost is cheap, does not destroy sample, it is easy to accomplish on-line monitoring can detect the velocity of sound, the attenuation coefficient, wall thickness of polymer parts simultaneously.

Description

The velocity of sound and attenuation coefficient integrated detection method in a kind of polymer
Technical field
The invention belongs to detection method technical field, it is integrated with attenuation coefficient to be specifically related to the velocity of sound in a kind of polymer Detection method.
Background technique
Polymer parts mostly use injection molding manner to form, ultrasonic wave wherein spread speed and attenuation coefficient be that its is microcosmic The important characteristic index of structure.The velocity of sound can characterize the crystallinity and the degree of orientation of polymer parts, attenuation coefficient and crystallization part Crystallite size tight association.It for the velocity of sound of polymer parts, is mainly measured at present using transit time method, i.e. measurement part Wall thickness and ultrasonic propagation time calculate the velocity of sound；For attenuation coefficient, presently mainly according to the amplitude knot of echo-signal Attenuation coefficient definition is closed to be calculated.These detection modes have the disadvantages that：
(1) transit time method needs the wall thickness of known tested polymer, and this method cannot be used for injection molding of polymers process On-line monitoring.
(2) attenuation coefficient being calculated according to echo-signal amplitude, it is numerous that and sound pressure amplitude few using information is disturbed factor, Computational accuracy is low.
Summary of the invention
The present invention is theoretical based on transonic aiming at the problem that existing detection mode, propose a kind of ultrasonic velocity with The integrated detection method of attenuation coefficient can be used for monitoring on-line, and precision is high.
The velocity of sound and attenuation coefficient integrated detection method, include the following steps in a kind of polymer：
(1) ultrasonic probe face sample to be tested is emitted into ultrasonic wave；
(2) reflection echo for acquiring sample upper and lower surface, seeks the amplitude spectrum of reflection echo, and the sample face ultrasound is visited Head side be defined as upper surface, back to side be lower surface；
(3) according to the amplitude spectrum of obtained reflection echo, the ultrasonic propagation velocity of sample to be tested, the thickness of sample are acquired And the attenuation coefficient of sample.
Preferably, being specifically included in step (3)：
(3-1) seeks logarithm to obtained amplitude spectrum H (f)；WhereinU1It (f) is upper surface reflection echo Frequency spectrum, U2It (f) is the frequency spectrum of lower surface reflection echo；
(3-2) seeks the logarithm of the amplitude spectrum of reflection echo and the relational graph of frequency f, and carries out linear fit to it and obtain Linear functional relation figure；Wherein, f is discrete frequency；
The vertical axis intercept D for the linear functional relation figure that (3-3) is sought seeks ultrasonic wave in test sample to be checked according to the following formula The spread speed c of product：
Z=ρ c
D=lnK
In above-mentioned formula：Z0The acoustic impedance of medium between sample to be tested upper surface and ultrasonic probe, Z are sample to be tested Acoustic impedance, ρ be sample to be tested density, c be ultrasonic wave sample to be tested spread speed；
(3-4), the thickness x of sample is calculated by time difference Δ t of upper and lower surface reflection echo, and expression formula is as follows：
X=c × Δ t/2
The slope k for the linear functional relation figure that (3-5) is sought, according to k=-2mx α ÷ fc, acquire attenuation coefficient α； Wherein m=0.115 is the coefficient that attenuation coefficient unit is converted into Np/cm by dB/cm, fcFor the centre frequency of ultrasonic probe.
In the present invention, the f is discrete frequency, specifically when receiving ultrasonic echo according to certain sample frequency fs And sampling number：2NIt is sampled, f is exactly 0-fsBetween discrete value, step-length fs/2N, that is to say, f indicates series of discrete Frequency：0, fs/2N, (fs/2N) * 2, (fs/2N) * 2*2 ..., fs。
The present invention can detect offline sample (part), preferably, the sample is offline sample, before detection The sample is placed in dielectric fluid, when detection, the ultrasonic probe is impregnated in the dielectric fluid, the Z0For dielectric fluid Acoustic impedance.
The dielectric fluid serves as couplant, for guaranteeing that ultrasonic wave can be efficiently entering sample.The couplant is Water or glycerol, machine oil etc..
It is contemplated that the present invention may be use with the detection of on-line sample, preferably, the sample is on-line sample, the ultrasound is visited Head is close to the die cavity side wall on the outside of on-line sample, the Z0For the acoustic impedance of the die cavity side wall.It is selectable, it can be visited in ultrasound The couplant is smeared between head and die cavity side wall, to improve detection accuracy.
It preferably, the sample to be tested is the polymer articles of surfacing, for example can be offline plastic part Or the online sample plastic parts etc. using injection molding.
To detect offline plastic part, and for adopting water as dielectric fluid, the above-mentioned velocity of sound based on transonic theory and The integrated detection method of attenuation coefficient, the principle is as follows：It, can be in plastics upper and lower surface when ultrasonic wave is propagated in plastic part Echo-signal is generated, the relationship between upper and lower surface echo-signal is determined by transmission function：
Wherein H (f) is transmission function (i.e. echo amplitude spectrum), U1It (f) is the frequency spectrum (U of upper surface echo1(f)=FT (u1 (t))), U2It (f) is the frequency spectrum of lower surface echo.H (f) is related with the density of medium, the velocity of sound, attenuation coefficient：
In formula：Z0For the acoustic impedance of water, Z is the acoustic impedance of plastic part, and Z=ρ c, ρ are the density of plastics, and c is ultrasonic wave Spread speed in the plastic.M=0.115 is the coefficient that attenuation coefficient unit is converted into Np/cm by dB/cm.X is plastic part Thickness, α are attenuation coefficient, fcFor the centre frequency of ultrasonic probe, f is discrete frequency (such as sampling frequency when acquisition data Rate is 50MHz, and sampling number is 128 points, this f, which is meant that, is averaged 0-50MHz the discrete frequency of equal part with 128 points Value).Φ1(f), Φ2(f) be respectively upper and lower surface reflection echo phase spectrum.Take logarithm can simultaneously transmission function both members ?：
Wherein | H (f) | it indicates to H (f) modulus；
When making f-ln | H (f) | when curve, lnK is vertical axis intercept, -2mxa ÷ fcFor slope.Therefore the upper of sample is obtained After the echo of lower surface, the logarithm of echo amplitude spectrum and the relational graph of frequency can be made, and linear fit is carried out to it and obtains line Property functional relation.K value is obtained by the fitting a straight line, and then ultrasonic propagation velocity c can be calculated, is reflected by upper and lower surface The time difference calculated wall thickness of echo, expression formula are as follows：
X=c × Δ t/2
X is plastic part wall thickness in formula, and Δ t is the time difference of upper and lower surface reflection echo.
The integrated detection method of the above-mentioned velocity of sound and attenuation coefficient based on transonic theory, should be known before detection The density of tested plastics.
Compared with prior art, the beneficial effects of the invention are as follows：
Detection method is easy to operate, and convenience of calculation, testing cost is cheap, does not destroy sample, it is easy to accomplish On-line monitoring, can detect the velocity of sound, the attenuation coefficient, wall thickness of polymer parts simultaneously.
Detailed description of the invention
Fig. 1 is ultrasound detection schematic diagram of the present invention.
Fig. 2 is reflection echo measured drawing of the present invention for PMMA detection.
Fig. 3 is the present invention for the logarithm of the echo amplitude spectrum of PMMA detection and the relational graph of frequency.
Specific embodiment
To be more clearly understood the present invention, below according to specific example and attached drawing of the invention, the present invention is carried out Further instruction.
As shown in Figure 1, being ultrasound detection schematic diagram of the invention, including ultrasonic probe 1, container 2, water 3, sample 4.
The supersonic detection method of plastic part, including：
Sample is placed in the container for filling water.
There is the impulse wave of certain centre frequency using the transmitting of water logging ultrasonic probe.Guarantee ultrasonic probe face sample when detection Product upper surface.
The reflection echo for receiving sample upper and lower surface is acquired using oscillograph.
The frequency spectrum of sample upper and lower surface reflection echo is calculated according to Fourier transformation.
The logarithm of reflection echo amplitude spectrum and the relational graph of frequency are made, and carries out linear fit.
It finds the vertical axis intercept of fitting a straight line and calculates K value.
Ultrasonic propagation velocity c is calculated according to K value.
According to velocity of sound c and the time difference calculated wall thickness of upper and lower surface reflection echo.
Attenuation coefficient is calculated according to wall thickness and the slope value of matched curve.
The reflection echo that Fig. 2 is PMMA surveys schematic diagram.First waveform is upper surface reflection echo, and second waveform is Lower surface reflection echo, the time difference between two waveforms are 3.28 μ s.The centre frequency of ultrasonic wave is 2.5MHz.
Fig. 3 is for the logarithm of the PMMA echo amplitude spectrum detected and the relational graph of frequency.By linear fit, obtain LnK=-0.1245, and known PMMA density is 1.18g/cm3, and then calculate ultrasonic wave spread speed in PMMA and be 2547m/s is 4.18mm according to the wall thickness that the time difference calculates PMMA, is surveyed with a thickness of 4.46mm, relative error 6.3%, Attenuation coefficient is 7.25dB/cm.Comparison shows that this method precision is higher.
The foregoing is merely an application example of the invention, the not restrictions to sample range is applicable in.It can apply The part that the present invention measures, there is no need and unable to exhaustive one by one, it is all within spirit of that invention and principle, done any repair Change, equivalent replacement, improve etc., it should be included within the scope of the present invention.

Claims (5)

1. the velocity of sound and attenuation coefficient integrated detection method in a kind of polymer, which is characterized in that include the following steps：
(1) ultrasonic probe face sample to be tested is emitted into ultrasonic wave；
(2) reflection echo for acquiring sample upper and lower surface, seeks the amplitude spectrum of reflection echo, the sample face ultrasonic probe Side is defined as upper surface, back to side be lower surface；
(3) according to the obtained amplitude spectrum of reflection echo, acquire the ultrasonic propagation velocity of sample to be tested, the thickness of sample and The attenuation coefficient of sample.
2. the velocity of sound and attenuation coefficient integrated detection method in polymer according to claim 1, which is characterized in that step (3) it in, specifically includes：
(3-1) seeks logarithm to obtained amplitude spectrum H (f)；WhereinU1It (f) is the frequency of upper surface reflection echo Spectrum, U2It (f) is the frequency spectrum of lower surface reflection echo；
(3-2) seeks the logarithm of the amplitude spectrum of reflection echo and the relational graph of frequency f, and carries out linear fit to it and obtain linearly Function relation figure；Wherein, f is discrete frequency；
The vertical axis intercept D for the linear functional relation figure that (3-3) is sought seeks ultrasonic wave in sample to be tested according to the following formula Spread speed c：
Z=ρ c
D=lnK
In above-mentioned formula：Z0The acoustic impedance of medium between sample to be tested upper surface and ultrasonic probe, Z are the sound of sample to be tested Impedance, ρ are the density of sample to be tested, and c is spread speed of the ultrasonic wave in sample to be tested；
(3-4), the thickness x of sample is calculated by time difference Δ t of upper and lower surface reflection echo, and expression formula is as follows：
X=c × Δ t/2
The slope k for the linear functional relation figure that (3-5) is sought, according to k=-2mx α ÷ fc, acquire attenuation coefficient α；Wherein m =0.115 is converted into the coefficient of Np/cm, f for attenuation coefficient unit by dB/cmcFor the centre frequency of ultrasonic probe.
3. the velocity of sound and attenuation coefficient integrated detection method in polymer according to claim 2, which is characterized in that described Sample is offline sample, and the sample is placed in dielectric fluid before detection, and when detection, the ultrasonic probe is impregnated in the medium In liquid, the Z0For the acoustic impedance of dielectric fluid.
4. the velocity of sound and attenuation coefficient integrated detection method in polymer according to claim 2, which is characterized in that described Sample is on-line sample, and the ultrasonic probe is close to the die cavity side wall on the outside of on-line sample, the Z0For the die cavity side wall Acoustic impedance.
5. the velocity of sound and attenuation coefficient integrated detection method in polymer according to claim 1 or 2, which is characterized in that The sample to be tested is the polymer articles of surfacing.
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Cited By (4)

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CN110824017A (en) * 2019-11-19 2020-02-21 南京大学 Soft material acoustic parameter measuring method
US11119031B2 (en) * 2017-08-14 2021-09-14 Quest Integrated, Llc Corrosion rate monitoring using ultrasound, and associated systems and methods
CN114216858A (en) * 2021-11-25 2022-03-22 长江存储科技有限责任公司 Detection method of thin film
CN114216859A (en) * 2021-11-25 2022-03-22 长江存储科技有限责任公司 Detection method of thin film

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CN104870994A (en) * 2012-12-17 2015-08-26 斯内克马公司 Method for characterising a part made of a composite material

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11119031B2 (en) * 2017-08-14 2021-09-14 Quest Integrated, Llc Corrosion rate monitoring using ultrasound, and associated systems and methods
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CN114216858A (en) * 2021-11-25 2022-03-22 长江存储科技有限责任公司 Detection method of thin film
CN114216859A (en) * 2021-11-25 2022-03-22 长江存储科技有限责任公司 Detection method of thin film
CN114216859B (en) * 2021-11-25 2023-11-10 长江存储科技有限责任公司 Method for detecting film
CN114216858B (en) * 2021-11-25 2023-11-17 长江存储科技有限责任公司 Method for detecting film

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