CN110081826A - Heat-barrier coating ceramic layer thickness measure new method based on Terahertz Technology - Google Patents
Heat-barrier coating ceramic layer thickness measure new method based on Terahertz Technology Download PDFInfo
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- CN110081826A CN110081826A CN201910353966.6A CN201910353966A CN110081826A CN 110081826 A CN110081826 A CN 110081826A CN 201910353966 A CN201910353966 A CN 201910353966A CN 110081826 A CN110081826 A CN 110081826A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
- G01B11/06—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material
- G01B11/0616—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material of coating
- G01B11/0625—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material of coating with measurement of absorption or reflection
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Abstract
The invention discloses a kind of method using THz wave measurement heat-barrier coating ceramic layer thickness, the terahertz signal for obtaining vertical incidence signal using reflective terahertz time-domain spectroscopy device and being reflected from sample surfaces；The peak value of incoming signal and sample reflection signal is obtained respectively and calculates the energy ratio of incidence wave and back wave；By means of the refractive index of wave impedance substance for calculation；The delay time at the first two peak is extracted from sample reflection signal, and then calculates ceramic layer thickness.Method proposed by the present invention is not necessarily to make standard specimen and establishes complicated theoretical model, and a kind of easy to operate, quick, lossless detection mode can be provided for the thickness of heat-barrier coating ceramic layer.
Description
Technical field
The present invention relates to Terahertz field of non destructive testing, specially a kind of to measure heat-barrier coating ceramic layer using THz wave
The method of thickness.
Background technique
Aero-engine is known as " jewel on industrial imperial crown ", is the important symbol for embodying National Core Competence.Mesh
The temperature of preceding gas turbine is excessively high, in order to protect part not to be corroded oxidation, is deposited on aero-engine base using thermal barrier coating
Achieve the purpose that protect basis material on body material.The typical structure of thermal barrier coating is as shown in Figure 1, comprising: from top to bottom successively
The ceramic layer 1 ' of arrangement, metal bonding coating 2 ', alloy substrate layer 3 '.
The ceramic layer of thermal barrier coating can be thinning with the increase of blade of aviation engine active time, leads to heat insulation
It reduces, and then the temperature of blade base is caused to increase, therefore it is also one of the main reason for thermal barrier coating fails that ceramic layer is thinning.
In consideration of it, the non-destructive testing of thermal barrier coating thickness is detected with assessment to blade of aviation engine health status and life appraisal, into
And ensure that the flight safety of military aircraft has important strategic importance, it is current critical issue urgently to be resolved.
Common Thickness sensitivity and appraisal procedure have electrochemical impedance spectroscopy, ultrasonic pachymetry, x-ray fluorescence in industry at present
Thickness measuring method, vortex thickness measuring method, optical coherence tomography thickness measuring, sound emission thickness measuring, Microwave thickaess measuring, THz wave thickness measuring etc..Its
Middle many methods all have some limitations, such as electrochemical impedance spectroscopy and fluorescence spectrum are chiefly used in thermal barrier coating failure mechanism
Research；Conventional ultrasonic method needs couplant, is not easy to detect automatically；Acoustic-emission belongs to dynamic testing method, therefore detects
It is to need to apply load；Optical coherence tomography method is too weak to the penetration capacity of material；Microwave method can measure oxide
Thickness, but need cosine measurement spinelle and porosity；The X-ray that can solve the above problem there are certain risk,
It has some limitations.
Emerging Terahertz (1THz=1012Hz frequency range) is typically referred in the electromagenetic wave radiation of 0.1THz~10THz,
It is highly suitable for the detection of thermal barrier coating thickness, can be carried out in the case where not contacting test specimen by Terahertz Technology
Not damaged and ionization non-destructive testing, the especially detection to nonmetallic materials such as ceramics, composite materials.Terahertz emission is one
Kind very safe electromagnetic radiation, frequency are that the photon energy of the electromagnetic wave of 1THz only has 4emV, be X-ray million/
One, it is minimum to the harm of human body, it can be used for non-destructive testing；Subpicosecond, femtosecond can be obtained using terahertz time-domain spectral technology
Temporal resolution, and by sampling and measuring technology, it the interference of background radiation noise always, signal-to-noise ratio can effectively can reach
To 1010；THz wave wavelength is longer, is influenced very little by material grains scattering.
Thickness detecting method based on Terahertz Technology mainly has two major classes: the first kind be for substance refraction coefficient not
In the case where knowing, a series of standard specimen of different-thickness is made first, then selects suitable data characteristics, and application is effective
Data fitting method, establish the quantitative detection model of substance thickness, the thickness measure applied to test specimen to be measured；However it is this kind of
The difficult point of method is the production of standard specimen, as long as producing standard specimen identical with test block ingredient to be checked establishes standard
True ground Quantitative Analysis Model realizes the detection of substance thickness, however in practical applications, it is very tired for accurately making test specimen
Difficult thing；Second class method is the thickness detecting method (side disclosed in 108519059 A of patent CN based on physical model
Method), the interaction principle of substance and THz wave first establishes the theoretical model of substance and THz wave interaction, so
Afterwards by means of the continuous iteration of optimization algorithm, the final detection for realizing substance thickness.The advantage of such method is tried without standard
The detection of substance thickness can be realized in part, but the accuracy requirement of the theoretical model for being established is very high, however resonable
By in modeling process, to consider in the foundation of theoretical model be also to compare by various factors in practice like clockwork
Difficult, that is, it establishes extremely difficult with the practical completely the same model of situation completely.This patent proposes one kind in view of the above problems
New thickness detecting method, without making standard specimen, and the interaction model without establishing substance and THz wave
Realize Thickness sensitivity.
Summary of the invention
Technical problem to be solved by the present invention lies in overcome defect of the existing technology, from Theory of Electromagnetic Field model
It sets out, is based on THz wave reflection and projectile energy relationship, propose a kind of utilization THz wave measurement heat-barrier coating ceramic layer
Thickness can be realized without making standard specimen, and the interaction model without establishing substance and THz wave in the method for thickness
Degree detection, being able to solve iterate currently based on the thermal barrier coating THICKNESS CALCULATION method of model causes calculating slower
The problem of.
For the present invention according to law of conservation of energy, obtaining THz wave in the projectile energy of surface ceramii layer is the terahertz penetrated
Hereby wave energy and the sum of the THz wave energy being reflected back.The wave resistance of medium is derived according to back wave and incidence wave energy ratio
It is anti-, the mean refractive index of test specimen can be calculated, finally extracts THz wave at different medium reflection signal reflex peak
Delay time can directly obtain the thickness of thermal barrier coating.
The present invention is to realize goal of the invention, and what is proposed a kind of utilizes THz wave measurement heat-barrier coating ceramic layer thickness
Method, comprising the following steps:
Step 1. measures polished metal surface and thermal barrier coating to be detected too using terahertz time-domain spectroscopy system respectively
Hertz reflection signal, respectively as reference signal and sample signal；
Step 2. obtains the amplitude of the peak value of reference signal and sample signal, and calculate the reflected energy of terahertz signal with
Projectile energy ratio, and find out according to the relationship between energy ratio and ceramic layer wave impedance η the refractive index n of ceramic layer；
Step 3. obtains the delay time Δ t in sample signal between first peak and second peak, is believed according to Terahertz
Communication process number in ceramic layer, its available thickness d
Wherein: c is the light velocity.
The step 2 comprises the steps of:
Step 2.1, the reflected energy and projectile energy ratio of terahertz wave signal are calculated first
Wherein Enr、EniRespectively indicate THz wave projectile energy and thermal barrier coating surface THz wave reflected energy, Ir、
IiRespectively indicate the peak value at first peak of sample signal and the peak value of incoming signal；
Step 2.2, when the ceramic layer of THz wave vertical irradiation to thermal barrier coating, the wave resistance of the ceramic layer of thermal barrier coating
Anti- η is
Wherein η1=376.73 Ω are air wave impedance.
Step 2.3, according to Maxwell's Theory of Electromagnetic Field, the refractive index n of the ceramic layer of thermal barrier coating is
Wherein μ0And ε0For permeability of free space and dielectric constant, εkAnd μkFor ceramic layer relative dielectric constant and relatively
Magnetic conductivity.
Propagation law in the present invention for electromagnetic wave in medium (such as: ceramics), using medium wave impedance as bridge,
The refractive index of medium can directly be calculated.In the calculation method, it is mainly in view of in frequency electromagnetic waves, medium
Imaginary part is far smaller than real part in complex wave impedance, therefore complex wave impedance approximation is done real number processing in engineering calculation.Thermal barrier coating
Ceramic layer belongs to non-ferromagnetic substance, therefore relative permeability is approximately 1H/m,.The medium weaker for dispersive power is (such as this
The ceramic layer of the thermal barrier coating of patent), the influence of dispersion refractive index can be ignored, can directly calculate its average folding in this way
Penetrate rate.
Compared with existing detection method, the invention has the following advantages that
(1) when calculating test specimen to be measured and surveying refractive index, by means of the energy for calculating reflected terahertz hereby wave and incident THz wave
Amount obtains the refractive index of ceramic layer than deriving the wave impedance of ceramic layer, avoids production standard specimen, it is particularly possible to solve
The certainly extremely difficult situation of production of standard specimen in practice；
(2) thickness of test specimen to be measured is only obtained by one-shot measurement, detection process is simple；
(3) methods herein, which overcomes, needs the complicated derivation of equation and optimization algorithm to carry out in 108519059 A of patent CN
The drawbacks of iteration, calculating speed is fast, and testing result is no longer limited by the accuracy of theoretical model.
Therefore this patent mentions for the thickness measure of ceramic layer during thermal barrier coating preparation process and thermal barrier coating service
A kind of accurate, simple, quick, lossless new detection method is supplied, it is only necessary to detect Terahertz incoming signal and time to be measured
The Thickness sensitivity of thermal barrier coating can be realized in reflection signal, establishes quantitative detection model without making standard specimen, without establishing
Complicated theoretical model, and do not need the iteration that time-consuming is carried out using optimization algorithm, detection speed is fast, and this method can be with
It is generalized to the Thickness sensitivity of other nonferromagnetic substances.
Detailed description of the invention
Fig. 1 is thermal insulation layer construction schematic diagram.
Fig. 2 is the incident waveform and reflection configuration time-domain diagram that THz wave is radiated at thermal barrier coating.Wherein: figure (a) is too
Hertz wave incident waveform figure is (b) THz wave reflectogram.
Fig. 3 reflects on heat-barrier coating ceramic layer for THz wave and transmission potential relational graph.
Fig. 4 is the thickness chart of test specimen heat-barrier coating ceramic layer.
Specific embodiment
Below in conjunction with embodiment and attached drawing, invention is further described in detail.Obviously described example is this
One kind of invention example, instead of all the embodiments, those having ordinary skill in the art is in the premise for not making creative work
Under every other embodiment obtained, shall fall within the protection scope of the present invention.
Embodiment:
Using terahertz time-domain spectroscopy system (such as: Picometrix, T-Ray 5000) obtain THz wave vertically shine
The incoming signal on thermal barrier coating is penetrated, as shown in Fig. 2 (a)；System transmitting THz wave vertical irradiation is reused in thermal boundary
The reflection signal of coating is as sample signal, as shown in Fig. 2 (b).
1) the reflection coefficient Γ of heat-barrier coating ceramic layer||It can be indicated with following model
Wherein η is ceramic layer wave impedance, η1It is air wave impedance, η1=376.73 Ω.
The incoming signal of the wave of Terahertz and reflection signal schematic representation as shown in figure 3, by Maxwell's Theory of Electromagnetic Field,
The energy of available incidence wave
Wherein EniFor the energy of incidence wave, EiFor the electric field strength of incidence wave, A is that incidence wave is vertically beaten on ceramic layer
Area.
The ENERGY E n of back waverIt is expressed as follows
THz wave is as follows in the ratio between the reflection signal of thermal barrier coating ceramics and incoming signal energy
Formula (1), which is brought into formula (4), to be had
The ratio between reflected energy of the terahertz signal on heat-barrier coating ceramic layer and projectile energy approximate can use terahertz
The ratio between signal and incoming signal square are hereby reflected, i.e.,
Wherein IrFor the amplitude of first posivtive spike in Fig. 2 (b), IiFor the amplitude of first posivtive spike in Fig. 2 (a).
The wave impedance η of heat-barrier coating ceramic layer is calculated according to formula (5) and formula (6)
2) in Theory of Electromagnetic Field, wave impedance has following representation
Wherein η is expressed as the wave impedance of ceramic layer, and μ and ε are respectively the magnetic conductivity and relative dielectric constant of ceramic layer, μ0With
ε0For permeability of free space and dielectric constant, μkAnd εkFor ceramic layer relative permeability and relative dielectric constant.
The relative dielectric constant of ceramic layer is derived according to formula (7)
The refractive index of heat-barrier coating ceramic layer is
Again for non-ferromagnetic substance, relative permeability μk≈ 1, thus obtain
Merge to obtain thermal barrier coating refractive index n by formula (7) and formula (8)
3) first peak is Terahertz incoming signal in surface ceramii layer reflection signal in Fig. 2 (b), and second peak is too
For hertz incoming signal in the reflection signal of ceramic layer bottom, the peak delay time of two reflection peaks is Δ t.Thermal barrier coating ceramics
The computation model of thickness degree is as follows
Wherein d is the thickness of heat-barrier coating ceramic layer, and c is the light velocity.
The foundation above process can calculate the thickness of some point of heat-barrier coating ceramic layer, then pass through terahertz time-domain
Spectroscopic system (such as: point by point scanning Picometrix, T-Ray 5000) is carried out to entire thermal barrier coating, obtains thermal barrier coating examination
The terahertz time-domain of all positions of part reflects signal.Then it repeats the above steps, calculates the thickness information of entire thermal barrier coating.
Finally the thickness information of heat-barrier coating ceramic layer is clearly shown using 3-D graphic, as shown in Figure 4.
The present invention extracts amplitude information from incoming signal and sample signal and derives reflected energy and incident wave energy
Than and then calculating the refractive index of heat-barrier coating ceramic layer, prolonging for second peak and first peak then being extracted from sample signal
When the time, finally according to these information calculate heat-barrier coating ceramic layer thickness.
Method proposed by the present invention is not necessarily to make standard specimen and establishes complicated theoretical model, can make pottery for thermal barrier coating
The thickness of enamel coating provides a kind of easy to operate, quick detection mode.
The present invention can non-contactly carry out heat-barrier coating ceramic layer Thickness sensitivity, and analyze the uniformity of thickness distribution,
It can be provided for the damage check during the thickness measure of the preparation process ceramic layer of thermal barrier coating and thermal barrier coating service
Lossless, accurate detection mode.
Claims (2)
1. a kind of method using THz wave measurement heat-barrier coating ceramic layer thickness, the steps include:
Step 1. obtains the terahertz signal and thermal barrier coating to be detected of vertical incidence using terahertz time-domain spectroscopy system respectively
Terahertz reflect signal, respectively as reference signal and sample signal；
The peak I of step 2. acquisition reference signal and sample signalr、Ii, and calculate the reflected energy and incident energy of terahertz signal
Ratio is measured, and finds out the refractive index n of ceramic layer according to the relationship between energy ratio and ceramic layer wave impedance η；
Step 3: obtaining the delay time Δ t in sample signal between first peak and second peak, existed according to terahertz signal
Communication process in ceramic layer, its available thickness d
Wherein: c is the light velocity.
2. utilizing the method for THz wave measurement heat-barrier coating ceramic layer thickness according to claim 1, which is characterized in that institute
Step 2 is stated to comprise the steps of:
Step 2.1 calculates the reflected energy and projectile energy ratio of terahertz wave signal first
Wherein Enr、EniRespectively indicate THz wave projectile energy and thermal barrier coating surface THz wave reflected energy, Ir、IiRespectively
Indicate the peak value at first peak of sample signal and the peak value of incoming signal；
When the ceramic layer of THz wave vertical irradiation to thermal barrier coating, the wave impedance η of the ceramic layer of thermal barrier coating is step 2.2
Wherein η1=376.73 Ω are air wave impedance；
Step 2.3 is according to Maxwell's Theory of Electromagnetic Field, the refractive index n of the ceramic layer of thermal barrier coating
Wherein: μ0And ε0Respectively permeability of free space and dielectric constant, εkAnd μkRespectively ceramic layer relative dielectric constant and
Relative permeability.
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| CN110823110A (en) * | 2019-11-13 | 2020-02-21 | 华太极光光电技术有限公司 | Method, system and equipment for determining electric parameters of reflecting material medium |
| CN112162295A (en) * | 2020-09-23 | 2021-01-01 | 青岛青源峰达太赫兹科技有限公司 | Terahertz thickness detection optimization method based on time-frequency analysis |
| CN113721233A (en) * | 2021-08-30 | 2021-11-30 | 中国航发沈阳黎明航空发动机有限责任公司 | Three-dimensional optical measurement method for thermal barrier coating thickness of guide blade of multi-connected turbine |
| CN114111604A (en) * | 2021-12-31 | 2022-03-01 | 西安交通大学 | Terahertz thickness measurement method for thermal barrier coating ceramic layer without reference sample |
| CN114427838A (en) * | 2022-01-10 | 2022-05-03 | 首都师范大学 | Method and system for predicting and evaluating thickness of medium based on reflection terahertz spectrum |
| CN115435696A (en) * | 2022-07-12 | 2022-12-06 | 福州大学 | Method for detecting thickness of shaft sleeve self-lubricating coating based on terahertz time-domain spectroscopy |
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| CN113721233B (en) * | 2021-08-30 | 2023-09-19 | 中国航发沈阳黎明航空发动机有限责任公司 | Three-dimensional optical measurement method for thickness of thermal barrier coating of multi-body turbine guide vane |
| CN114111604A (en) * | 2021-12-31 | 2022-03-01 | 西安交通大学 | Terahertz thickness measurement method for thermal barrier coating ceramic layer without reference sample |
| CN114427838A (en) * | 2022-01-10 | 2022-05-03 | 首都师范大学 | Method and system for predicting and evaluating thickness of medium based on reflection terahertz spectrum |
| CN115435696A (en) * | 2022-07-12 | 2022-12-06 | 福州大学 | Method for detecting thickness of shaft sleeve self-lubricating coating based on terahertz time-domain spectroscopy |
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