CN105548364A - Higher-order nonlinear parameter characterization method for bonding strength of thermal barrier coating - Google Patents

Abstract

The objective of the invention is to provide a transmission longitudinal wave higher-order nonlinear parameter characterization method for the bonding strength of a thermal barrier coating. The method is used for detecting the bonding strength of a coating and can be widely applied to fields like aviation. The transmission longitudinal wave higher-order nonlinear parameter characterization method comprises the following steps: determining the parameters of excitation signals according to the propagation distance of transmission longitudinal waves and the acoustic velocity of a to-be-detected material; emitting a pulse string signal via a high-power ultrasonic transmitting-receiving instrument, allowing the transmission longitudinal waves to be incident into the thermal barrier coating and allowing the longitudinal wave to interact with the coating at the bonding interface of the coating and a matrix so as to produce a higher harmonic signal; and during an experiment, recording the nonlinear parameters of the coating in different states and comparing the recorded nonlinear parameters with a standard curve so as to predict the bonding strength of the coating.

Description

The high-order nonlinear parameter characterization method of thermal barrier coating bond strength

One, technical field

The invention belongs to ultrasonic non-destructive inspection techniques and anchoring strength of coating field, be specifically related to the transmission-type compressional wave limited amplitude method of thermal barrier coating bond strength, is a bond strength utilizing multiple nonlinear parameter to detect coating.

Two, background technology

Thermal barrier coating bond strength compressional wave high-order nonlinear parameter characterization method is a kind of ultrasonic non-destructive inspection techniques of real-time detection thermal barrier coating bond strength.Utilize in ultrasonic propagation process, the interaction of sound wave and combination interface, cause the phenomenons such as hyperacoustic scattering or reflection, create harmonic signal, sound wave is occurred non-linear.The method is all widely used in fields such as Aero-Space, and the fatigue damage as aircraft engine turbine detects, the detection of the fatigue damages such as the wheel hub of automobile or train, and the detection of the mechanical component such as axle and web member envelope.

Thermal barrier coating bond strength compressional wave high-order nonlinear parameter characterization method uses the ultrasound wave that frequency range is 1MHz-20MHz, detects all trend of change with the bond strength change of thermal barrier coating such as Received signal strength fundamental voltage amplitude and higher hamonic wave amplitude, second order nonlinear coefficient and third-order nonlinear optical coefficient.

Research in recent years shows, the nonlinear effect of the damage of surface coating and the bonding interface situation between coating and matrix material and ultrasonic signal is closely related.Along with surface coating is inner and the generation of bonding interface damage between coating and matrix material and evolution, the ultrasound wave of single-frequency when propagating, because the non-linear of material will produce high-frequency harmonic, the high-order harmonic wave of the integer multiple frequencies such as namely 2 times, 3 times.Researcher's many uses second order classical nonlinear factor research sound wave non-linear phenomena in the application of nonlinear theory at present, in 1755, Euler proposes the concept of nonlinear acoustics, and Lagrange (1760), Stokes (1848) and Rayleigh (1910) etc. have studied nonlinear acoustics theory.The distinct nonlinear method of Lamb wave that utilizes of Deng characterizes layered structure surface nature.Guo Yi utilizes the second harmonic technology to carry out ultrasonic nonodestruction evaluation to solid propellant rocket interface bond quality, the two non-linear ultrasonic that utilizes of tax state is evaluated coating for metal surfaces damage, only a few studies person uses third-order nonlinear optical coefficient, the second nonlinear that KoenE-AVanDenAbeele propagates in media as well to elasticity pulsating wave and high-order nonlinear phenomenon and second order nonlinear coefficient and Higher-order nonlinear coefficient are to the earlier damage of assessment material, M.Amura and Yan Hongjuan utilizes second order and third-order nonlinear optical coefficient to evaluate the fatigue lifetime to metal material, the relation to the ultrasonic second order in measuring process and third-order nonlinear optical coefficient such as GangRen is analyzed.Generally speaking non-linear ultrasonic theoretical research at present concentrates on nonlinear wave equations, and nonlinear wave equations only derives second order nonlinear coefficient, there is no the derivation to Higher-order nonlinear coefficient, especially the patent not yet finding to use third-order non-linear ultrasound examination to characterize anchoring strength of coating and document, for this problem, propose and utilize second order nonlinear coefficient and third-order nonlinear optical coefficient to evaluate the bond strength of coating simultaneously, the research tool of anchoring strength of coating is had very important significance.

Three, summary of the invention

The object of the invention is to provide a kind of compressional wave high-order nonlinear characterizing method of thermal barrier coating bond strength, for high-order nonlinear ultrasound parameter variation tendency in on-line checkingi thermal barrier coating bond strength experimentation.

The characterizing method of the compressional wave high-order nonlinear parameter of thermal barrier coating bond strength of the present invention comprises: utilize ultrasound non-linear system to receive and dispatch instrument launching and receiving ultrasonic signal, transmission-type compressional wave limited amplitude method principle is utilized to be incided by ultrasound wave in thermal barrier coating test specimen, the combination interface place of compressional wave and thermal barrier coating and matrix interacts and creates higher harmonic component, utilizes higher hamonic wave amplitude and second order, the ultrasonic coefficient of third-order non-linear to detect the size with characterizing coating bond strength.

Four, accompanying drawing explanation

Fig. 1 anchoring strength of coating detection method process flow diagram;

Fig. 2 transmission-type compressional wave limited amplitude method principle.

Five, embodiment

Fig. 1 is anchoring strength of coating non-linear ultrasonic detection system schematic diagram, and each several part is thermal barrier coating test specimen, ultrasonic transducer, high-power ultrasonic transmitting-receiving instrument, computing machine, oscillograph.According to the thickness determination excitation signal cycle number of tested coating and matrix, frequency and amplitude etc.Thermal barrier coating is arranged on the position as place in Fig. 1, transducer is arranged on Fig. 1 transducer position, connected nonlinearity ultrasonic testing system.

In Fig. 2 when ultrasound wave is propagated in coating and matrix combination interface, the relation of the primary stress of non-linear non-individual body and strain is caused to be expressed as by the anharmonicity of potential energy between atomic force:

$\mathrm{\σ}=E(\mathrm{\ϵ}+\frac{1}{2}{\mathrm{\β}}_1{\mathrm{\ϵ}}^2+\frac{1}{3}{\mathrm{\β}}_2{\mathrm{\ϵ}}^3...)---\left(1\right)$

In formula, β _n(n=1,2,3) are nonlinear factor.

In order to explain generation ofharmonic, assuming that incident wave is ultrasonic longitudinal wave frequently of itemizing, sound wave, through after test specimen, is received receive MUT at the other end.If ignore decay, then one-dimensional wave equation is:

$\mathrm{\ρ}\frac{{\∂}^{2}u}{\∂t^2}=\frac{\∂\mathrm{\σ}}{\∂x}---\left(2\right)$

In formula, ρ is Media density, and x is propagation distance, and t is the time, and u is the displacement being positioned at x place particle in medium.Simultaneous (1), (2) formula, utilize the relation of particle displacement and strain, and ignore the higher order term in (1) formula more than three rank, obtains the ultrasonic wave equation of one-dimensional nonlinear

$c^2\·\frac{{\∂}^{2}u}{\∂t^2}=\frac{{\∂}^{2}u}{\∂x^2}+{\mathrm{\β}}_1\frac{\∂u}{\∂x}\·\frac{{\∂}^{2}u}{\∂x^2}+{\mathrm{\β}}_2{\left(\frac{\∂u}{\∂x}\right)}^2\·\frac{{\∂}^{2}u}{\∂x^2}---\left(3\right)$

In formula, c is the velocity of wave in medium.

Utilize perturbation method to obtain approximate solution.By a series of for u (x, t) generate power series:

u(x,t)＝u ₀(x,t)+xu ₁(x,t)+···+x ⁿu _n(x,t)(4)

Application perturbation method, and in the process of separating, ignore exponent number be greater than the high-order of three in a small amount, the approximate solution of (3) can be obtained:

$\begin{array}{c}u(x,t)=A\cos (kx-\mathrm{\ω}t)-\frac{{\mathrm{\β}}_1}{5}{k}^2{A}^{2}x\cos 2(kx-\mathrm{\ω}t)\\ +\frac{{\mathrm{\β}}_2}{24}{k}^3{A}^{3}x\[\cos 3(kx-\mathrm{\ω}t)+3\cos (kx-\mathrm{\ω}t)\]\end{array}---\left(5\right)$

First-harmonic A can be obtained from formula (5) ₁with the amplitude of second harmonic, third harmonic:

A ₁＝A(6)

$A_2=\frac{1}{8}\left({A_1}^2{k}^2{\mathrm{\β}}_{1}x\right)---\left(7\right)$

$A_3=\frac{1}{24}\left({A_1}^3{k}^3{\mathrm{\β}}_{2}x\right)---\left(8\right)$

Nonlinear factor β is can be derived from by formula (7) ₁for

${\mathrm{\β}}_1=\frac{8}{k^{2}x}\frac{A_2}{A_1^2}---\left(9\right)$

Formula (8) can obtain nonlinear factor β ₂for

${\mathrm{\β}}_2=\frac{24}{k^{3}x}\frac{A_3}{A_1^3}---\left(10\right)$

The difference of thermal barrier coating bond strength can affect the generation efficiency of secondary in transmission signal, third harmonic, and the nonlinear factor obtained by formula (9) and (10) reflects the distortion degree of ultrasound wave through waveform when material and combination interface thereof.Therefore non-linear ultrasonic detection technique can be applied to the detection of thermal insulation layer construction interface bond strength.

Claims (7)

1. the compressional wave high-order nonlinear parameter characterization method of an anchoring strength of coating, it is characterized in that: use high frequency ultrasound transmitting-receiving instrument to produce pulsating wave string signal, excitation centre frequency is the ultrasonic longitudinal wave transducer of f, use the ultrasonic longitudinal wave receive MUT acoustic signals that centre frequency is 2f, draw the nonlinear parameter of different coating and the relation curve of actual bond strength, for detecting the bond strength of coating.

2. the compressional wave high-order nonlinear parameter characterization method of anchoring strength of coating according to claim 1, is characterized in that: the non-linear anharmonicity mainly due to atomic force potential energy, crystal grain dislocation, fine damage (as: crackle of remaining silent, microcosmic delamination crack, pseudocaustics method, bond strength etc.), the contact interface of coating and separate out equal.Change when propagating when the junction of ultrasound wave in coating and substrate two kinds of different mediums and cause hyperacoustic non-linear, namely occurred the composition of higher hamonic wave in Received signal strength, therefore can utilize the size of ultrasound non-linear parameter characterization anchoring strength of coating.

3. the compressional wave high-order nonlinear Parametric Representation method of anchoring strength of coating according to claim 1, it is characterized in that: utilize high frequency ultrasound to receive and dispatch instrument launching and receiving signal, take train of impulses as pumping signal, the quantity of train of impulses is relevant with speed in tested propagation distance of tearing open in material with sound wave.

4. the compressional wave high-order nonlinear Parametric Representation method of anchoring strength of coating according to claim 1, it is characterized in that: the wave form distortion utilizing ultrasonic pulse signal string to produce in coating and substrate combination interface are propagated obtains nonlinear factor, transmission-type compressional wave limited amplitude method is adopted to the non-linear ultrasonic effect of the bond strength of coating.

5. the compressional wave high-order nonlinear parameter characterization method of anchoring strength of coating according to claim 1, it is characterized in that: docking is received acoustic signals and carried out spectrum analysis, obtain first-harmonic and the high-order harmonic wave amplitude of Received signal strength, calculate Amplitude Ration and second order, the third-order nonlinear optical coefficient of higher hamonic wave and first-harmonic.

6. the compressional wave high-order nonlinear parameter characterization method of anchoring strength of coating according to claim 1, it is characterized in that: utilize cupping machine to carry out stretching experiment to test specimen, every minor tick uses the bond strength state of non-linear ultrasonic systems axiol-ogy coating after fixing drawing stress, obtain higher hamonic wave and fundamental voltage amplitude ratio, second order nonlinear coefficient and the third-order nonlinear optical coefficient variation tendency with anchoring strength of coating.

7. the compressional wave high-order nonlinear parameter characterization method of anchoring strength of coating according to claim 1, it is characterized in that: utilize second order nonlinear coefficient and third-order nonlinear optical coefficient with the variation tendency of anchoring strength of coating, data fitting is carried out to nonlinear factor and bond strength, obtain fitting function, under the condition of Non-Destructive Testing, just can carry out quantitative predication to bond strength when recording nonlinear factor.