CN101846655A - Method for ultrasonically measuring interface rigidity in bonding structure - Google Patents

Abstract

The invention relates to a method for ultrasonically measuring the interface rigidity in a bonding structure, which belongs to the technical field of nondestructive testing. The method comprises the following steps of: determining a reflection coefficient by utilizing the reflection echo of the bonding interface; determining the rigidity coefficients of the bonding structure in a debonding area, a weakly bonding area and an ideal bonding area jointly by utilizing the reflection coefficient and resonant frequency; selecting the resonant frequency through the characteristics of multiple times of reflection echoes of the bonding interface; utilizing the resonant frequency as the central frequency of detecting advanced steel materials, an adhesive and the advanced steel materials; obtaining the reflection coefficient by making full use of the reflection echoes of the interface so as to obtain the rigidity coefficient of the interface, wherein under the resonant frequency, an ultrasonic echo signal changes continuously along with the change of the rigidity of the bonding interface, and the error of the rigidity through the ultrasonic measurement is less than 5 percent. The method solves the problem that the rigidity coefficient of the interface cannot be measured rapidly, accurately and in service.

Description

The ultrasonic wave measuring method of bonded structure median surface rigidity

Technical field

The invention belongs to the Non-Destructive Testing field, be specifically related to a kind of bonded structure interface rigidity ultrasonic wave measuring method.

Background technology

Bonded structure is widely used and studies in various fields such as Aeronautics and Astronautics, military project and machineries, adhesive linkage interface unsticking and boundary strength reduction in use are the key factors that influences bonded structure, also be the Non-Destructive Testing field, one of key factor that the bonding quality at adhesive linkage interface is detected and estimates.

Ultrasonic method can not directly be measured bonding strength, for the measurement of weak bonding strength difficulty more, but can measure the stiffness coefficient of glue-line, thickness, decay etc., and this tittle can reflect bonding interface mean intensity size under certain condition indirectly.Bonded structure also increases gradually in the use of mechanical field, and conventional steel are the critical material that is used to make vehicle structure in history always.In order to satisfy the demand that people are higher to vehicle safety, noise is littler, adopt the Heavy Type Steel Structure parts in the design usually, to meet anti-collision and durability standards.The result causes vehicle weight to strengthen, and the service efficiency of fuel is reduced.The Heavy Type Steel Structure parts adopt riveted joint and solder technology usually, have further strengthened the weight of vehicle.In order to address the above problem, it is bonding that numerous companies utilize advanced steel to carry out, and solved that the stress that riveted joint and welding produced is concentrated, the problems such as service efficiency reduction of fuel.As seen, the quality of the health status of bonded structure directly influences these durability of structures and overall security.In-service, owing to the reasons such as influence of bearing dissimilar loads, material behavior and environmental baseline, make the strength degradation of bonding interface, cause the rigidity of bonding interface to reduce, thus the destruction that makes bonded structure be in bad duty even cause total.Therefore, the size measurement to bonded structure interface rigidity coefficient seems very important.

Utilize the research of ultrasound examination bonded structure to obtain certain progress at present, confirmed that ultrasound wave is used for feasibility and development potentiality that the interface rigidity coefficient is measured.But all be the unsticking of bonding interface and intact bonding in all at present achievements in research, seldom part body has been studied weak bonded structure, in these researchs the stiffness coefficient at interface is not reasonably chosen.Scholars such as Michaloudaki were at International Journal of Adhesion ﹠ amp in 2005; The article that Adhesives delivers " Neutron imaging as a tool for the non-destructive evaluation of adhesive joints in aluminum ", the scholars such as Paul measure the interface rigidity coefficient in the article that article " characteristics of low-frequency of uniform thickness aluminium sheet bond ultrasonic reflection frequency spectrum " that applied acoustics in 2009 is delivered etc. is delivered accurately scholars such as article " Reconstructing the adhesion stiffnessdistribution in a laminated elastic plate:Exact and approximate inverse scattering solutions " that J.Acoust.Soc.Am in 2007 delivers and Wang Xiaomin.

These have been delivered or disclosed achievement in research also is to make full use of the interfacial characteristics that bonding interface is in intact bonding (desirable bonding) and interface unsticking, round trip echoes caused resonance frequency in interface are not optimized and choose.Purpose of the present invention is exactly to change more sensitive characteristics by the resonance frequency of selecting different frequency range and the reflection coefficient of bonding interface reflection echo, the bonded structure interface is in unsticking district, weak adhesion zone and desirable adhesion zone accurately measures.

Summary of the invention

The objective of the invention is accurately and to use as a servant the present situation of measuring for the size that solves advanced steel bonding interface rigidity, bonding health status and interface rigidity to advanced steel are assessed, and propose the bonding interface rigidity ultrasonic wave measuring method of a kind of advanced steel.

Technical scheme of the present invention specifically may further comprise the steps:

Step 1): the resonance frequency of determining to detect bonding interface

Stress when utilizing wave equation to obtain bonded structure medium wave propagation and displacement expression formula (1) and (2) obtain the expression formula (4) of reflection coefficient then according to the continuous condition of contact of bonding interface (3).

(a) displacement of bonding interface and stress expression formula:

$u=\left\{\begin{array}{c}{u}^{\left(1\right)}={\mathrm{Ie}}^{i(k_{1}x-\mathrm{\ωt})}+A_R{e}^{-i(k_{1}x+\mathrm{\ωt})}\\ u^{\left(2\right)}=A_T{e}^{i(k_{2}x-\mathrm{\ωt})}\end{array}\right.---\left(1\right)$

$\mathrm{\σ}=\left\{\begin{array}{c}{\mathrm{\σ}}_x^{\left(1\right)}=i({\mathrm{\λ}}_1+2{\mathrm{\μ}}_1)\·k_1[{\mathrm{Ie}}^{i(k_{1}x-\mathrm{\ωt})}-A_R{e}^{-i(k_{1}x+\mathrm{\ωt})}]\\ {\mathrm{\σ}}_x^{\left(2\right)}=i({\mathrm{\λ}}_2+2{\mathrm{\μ}}_2)\·k_2{A}_T{e}^{i(k_{2}x-\mathrm{\ωt})}\end{array}\right.---\left(2\right)$

(b) the condition of contact expression formula of bonding interface:

$\left.\begin{array}{c}{u}^{\left(1\right)}=u^{\left(2\right)}\\ {\mathrm{\σ}}_x^{\left(1\right)}={\mathrm{\σ}}_x^{\left(2\right)}\end{array}\right\}---\left(3\right)$

(c) obtain the reflection coefficient expression formula of interface primary event echo by above-mentioned equation:

${\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="HSA00000138420500011.png,HSA00000138420500012.png"\; state="\{\{state\}\}">R</figure-callout>}}_1=\frac{z_{2L}-z_{1L}}{z_{1L}+z_{2L}}---\left(4\right)$

Wherein, I, A _RAnd A _TBe amplitude;

F is a frequency; μ ₁, μ ₂, λ ₁And λ ₂Be respectively the Lame constant at solid and adhesive linkage place; z _1L=ρ ₁c _1L, z _2L=ρ ₂c _2L, z _1LAnd z _2LBe respectively the impedance of solid and adhesive linkage, ρ ₁And ρ ₂Be the density of solid and adhesive linkage, c _1LAnd c _2LBe respectively the longitudinal wave velocity of solid and adhesive linkage; R ₁Be reflection coefficient; u ⁽¹⁾And u ⁽²⁾Be respectively the displacement of solid and adhesive linkage medium wave propagation;

With

Stress for solid and adhesive linkage medium wave propagation.

It is (6) that bonding interface utilizes the condition of contact (5) of spring model to obtain reflection coefficient

${\mathrm{\&sigma;}}_x^{\left(1\right)}={\mathrm{\&sigma;}}_x^{\left(2\right)}=K_N(u^{\left(1\right)}-u^{\left(2\right)})---\left(5\right)$

${\mathrm{<figure-callout\; id="2"\; label="R"\; filenames="HSA00000138420500011.png,HSA00000138420500022.png"\; state="\{\{state\}\}">R</figure-callout>}}_2=\frac{z_{2L}-z_{1L}+2\mathrm{\&pi;fi}{z}_{2L}{z}_{1L}/K_N}{z_{2L}+z_{1L}-2\mathrm{\&pi;fi}{z}_{2L}{z}_{1L}/K_N}---\left(6\right)$

When there were round trip echoes in bonding interface, bonding interface utilized the condition of contact (5) of spring model to obtain the expression formula (7) of reflection coefficient.

$\left|{\mathrm{<figure-callout\; id="3"\; label="R"\; filenames="HSA00000138420500011.png,HSA00000138420500012.png"\; state="\{\{state\}\}">R</figure-callout>}}_3\right|=\left|\frac{\frac{z_{2L}-z_{1L}+2\mathrm{\&pi;fi}{z}_{1L}{z}_{2L}/K_N}{z_{2L}+z_{1L}-2\mathrm{\&pi;fi}{z}_{1L}{z}_{2L}/K_N}+\left(\frac{z_{2L}-z_{1L}+2\mathrm{\&pi;fi}{z}_{1L}{z}_{2L}/K_N}{z_{2L}+z_{1L}-2\mathrm{\&pi;fi}{z}_{1L}{z}_{2L}/K_N}\right)e^{-2i{k}_2\mathrm{<figure-callout\; id="1"\; label="d"\; filenames="HSA00000138420500011.png,HSA00000138420500012.png"\; state="\{\{state\}\}">d</figure-callout>}}}{1+\left(\frac{z_{2L}-z_{1L}+2\mathrm{\&pi;fi}{z}_{1L}{z}_{2L}/K_N}{z_{2L}+z_{1L}-2\mathrm{\&pi;fi}{z}_{1L}{z}_{2L}/K_N}\right)\left(\frac{z_{2L}-z_{1L}+2\mathrm{\&pi;fi}{z}_{1L}{z}_{2L}/K_N}{z_{2L}+z_{1L}-2\mathrm{\&pi;fi}{z}_{1L}{z}_{2L}/K_N}\right)e^{-2i{k}_{2}d}}\right|---\left(7\right)$

Wherein, K _NNormal stiffness coefficient for bonding interface; R ₂And R ₃Be respectively bonding interface once and reflection coefficient repeatedly; D is a thickness of adhibited layer; k ₂Be wave number.

To expression formula (7) minimizing, thereby obtain expression formula (8).

$\mathrm{fd}=\frac{c_{2L}(2n-1)}{4}\&times;{10}^3,n=\mathrm{1,2,3}...---\left(8\right)$

Wherein, n is the exponent number of resonance frequency, and after n was selected, the product of resonance frequency and thickness of adhibited layer was a constant, and d is a millimeter (mm) for thickness of adhibited layer unit.Bring the resonance frequency that to determine in the expression formula (8) that bonding interface rigidity detects into by the longitudinal wave velocity of adhesive linkage medium.

Step 2): produce the Gauss pulse ripple that centre frequency is adjustable by function generator 4, excitation frequency is the resonance frequency that step 1) obtains;

Step 3): pumping signal is imported stimulus sensor 2 into after power amplifier 3 carries out power amplification;

Step 4): stimulus sensor 2 Gauss pulse ripple signals import in the bonded structure 1 constantly to be propagated, and makes its repeatedly reflection in bonded structure 1;

Step 5): stimulus sensor 2 receives the signal after the Gauss pulse ripple repeatedly reflects in bonded structure 1, show on oscillograph 5, and store in the computing machine 6;

Step 6): utilize the one dimension analysis method of wavelet packet that the time-domain signal that receives is carried out denoising Processing, analyze the echo of Gauss pulse echo in bonding solid interface, bring in the expression formula (7) thickness of adhibited layer, resonance frequency and reflection coefficient are counter respectively, can draw the rigidity of bonding interface.

The present invention has the following advantages: 1) can carry out measuring fast and effectively to the size of bonded structure stiffness coefficient; 2) only need sensor installation in bonded structure, can the stiffness coefficient of bonded structure be detected, easy to detect, labour intensity is low.

Description of drawings

Fig. 1 is the pick-up unit schematic diagram;

Fig. 2 is the signal of sensor excitation in the bonded structure;

Fig. 3 be ripple at the adhesive linkage place variation diagram of reflex time repeatedly;

Fig. 4 is in the bonded structure of excitation frequency when being 5.5MHz, the waveform that receiving sensor 2 receives;

Fig. 5 is a bonding interface when having the primary event echo, the span of shear wave and compressional wave interface rigidity coefficient;

Among the figure: 1 is bonded structure steel plate-glue-line-steel plate, 2 for autoexcitation from receiving sensor, 3 is power amplifier, 4 is function generator, 5 is oscillograph, 6 is computing machine.

Embodiment

Below in conjunction with specific embodiment content of the present invention is described in further detail:

Device of the present invention comprises referring to Fig. 1: advanced steel-bonding agent-advanced steel 1, autoexcitation are from the sensor 2, power amplifier 3, function generator 4, oscillograph 5 and the computing machine 6 that receive.Wherein, sensor installation 2 on bonded structure 1, and sensor 2 links to each other with power amplifier 3, and power amplifier 3 and function generators 4 link to each other, and function generator 4 links to each other with oscillograph 5, and oscillograph 5 links to each other with computing machine 6.

The present invention utilizes ultrasound wave that the interface rigidity coefficient of bonded structure is measured, and step is as follows:

1) bonded structure that constitutes based on steel-epoxy resin-steel in this example, density is ρ ₁=7800kg/m ³, longitudinal wave velocity is c _1L=5850m/s, transverse wave speed are c _1T=3230m/s, epoxy resin density is ρ ₂=1300kg/m ³, longitudinal wave velocity is c _2L=2800m/s, transverse wave speed are c _2T=1100m/s, impedance is z _1L=ρ ₁c _1L, z _IT=ρ ₁c _1T, z _2L=ρ ₂c _2LAnd z _2T=ρ ₂c _2T, steel plate is 5mm, utilizes formula (4) and (6) to equate to carry out numerical evaluation, as shown in Figure 5, has provided the span of unsticking district, weak adhesion zone and desirable adhesion zone interface rigidity coefficient.

Utilize expression formula (8) to choose resonance frequency, the thickness of establishing adhesive linkage is unit 1, n=4, and the detection resonance frequency that can obtain bonded structure is 5.5MHz.

2) produce the Gauss pulse ripple by function generator 4, the frequency of selection is 5.5MHz, and wherein time domain waveform is shown in Figure 2.

3) pumping signal is amplified through power amplifier, is the Gauss pulse ripple of 5.5MHz by sensor 2 excitation frequency in bonded structure 1;

4) frequency is that the waveform that the Gauss pulse ripple of 5.5MHz receives in bonded structure is seen shown in Figure 4;

5) signal in the analysis chart 4 by technology such as digital filterings, is handled signal, draws the reflection coefficient at bonding interface place, and 2. signal with the ratio of signal amplitude 4. is among Fig. 4: The longitudinal wave velocity that 2. signal multiply by epoxy numerical value with the signal mistiming 3. divided by 2 thickness that obtain adhesive linkage is being:

Reflection coefficient, thickness of adhibited layer and resonance frequency 5.5MHz being brought into the rigidity that draws the interface in the reflection coefficient expression formula (7) of round trip echoes is: 3.05 * 10 ¹⁵N/m ³With 3 * 10 of reality ¹⁵N/m ³The error of comparing is: 1.7%, and satisfy and detect requirement.

And the desirable bonding interface normal stiffness coefficient in the document is: 1 * 10 ¹⁸N/m ³As seen, this method is higher to the rigidity accuracy of detection at interface.

Claims (1)

1. the ultrasonic wave measuring method of bonded structure median surface rigidity, it is characterized in that: this method may further comprise the steps:

Step 1): the resonance frequency of determining to detect bonding interface

Stress when utilizing wave equation to obtain bonded structure medium wave propagation and displacement expression formula (1) and (2) obtain the expression formula (4) of reflection coefficient then according to the continuous condition of contact of bonding interface (3):

(a) displacement of bonding interface and stress expression formula:

$u=\left\{\begin{array}{c}{u}^{\left(1\right)}=I{e}^{i(k_{1}x-\mathrm{\&omega;t})}+A_R{e}^{-i(k_{1}x+\mathrm{\&omega;t})}\\ u^{\left(2\right)}=A_T{e}^{i(k_{2}x-\mathrm{\&omega;t})}\end{array}\right.---\left(1\right)$

$\mathrm{\&sigma;}=\left\{\begin{array}{c}{\mathrm{\&sigma;}}_x^{\left(1\right)}=i({\mathrm{\&lambda;}}_1+2{\mathrm{\&mu;}}_1)\&CenterDot;k_1[I{e}^{i(k_{1}x-\mathrm{\&omega;t})}-A_R{e}^{-i(k_{1}x+\mathrm{\&omega;})t}\\ {\mathrm{\&sigma;}}_x^{\left(2\right)}=i({\mathrm{\&lambda;}}_2+2{\mathrm{\&mu;}}_2)\&CenterDot;k_2\&CenterDot;A_T{e}^{i(k_{2}x-\mathrm{\&omega;t})}\end{array}\right.---\left(2\right)$

(b) the condition of contact expression formula of bonding interface:

$\left.\begin{array}{c}{u}^{\left(1\right)}=u^{\left(2\right)}\\ {\mathrm{\&sigma;}}_x^{\left(1\right)}={\mathrm{\&sigma;}}_x^{\left(2\right)}\end{array}\right\}---\left(3\right)$

(c) obtain the reflection coefficient expression formula of interface primary event echo by above-mentioned equation:

$R_1=\frac{z_{2L}-z_{1L}}{z_{1L}+z_{2L}}---\left(4\right)$

Wherein, I, A _RAnd A _TBe amplitude;

F is a frequency; μ ₁, μ ₂, λ ₁And λ ₂Be respectively the Lame constant at solid and adhesive linkage place; z _1L=ρ ₁c _1L, z _2L=ρ ₂c _2L, z _1LAnd z _2LBe respectively the impedance of solid and adhesive linkage, ρ ₁And ρ ₂Be the density of solid and adhesive linkage, c _1LAnd c _2LBe respectively the longitudinal wave velocity of solid and adhesive linkage; R ₁Be reflection coefficient; u ⁽¹⁾And u ⁽²⁾Be respectively the displacement of solid and adhesive linkage medium wave propagation;

With

Stress for solid and adhesive linkage medium wave propagation;

It is (6) that bonding interface utilizes the condition of contact (5) of spring model to obtain reflection coefficient

${\mathrm{\&sigma;}}_x^{\left(1\right)}={\mathrm{\&sigma;}}_x^{\left(2\right)}=K_N(u^{\left(1\right)}-u^{\left(2\right)})---\left(5\right)$

$R_2=\frac{z_{2L}-z_{1L}+2\mathrm{\&pi;fi}{z}_{2L}{z}_{1L}/K_N}{z_{2L}+z_{1L}-2\mathrm{\&pi;fi}{z}_{2L}{z}_{1L}/K_N}---\left(6\right)$

When there were round trip echoes in bonding interface, bonding interface utilized the condition of contact (5) of spring model to obtain the expression formula (7) of reflection coefficient;

$\left|R_3\right|=\left|\frac{\frac{z_{2L}-z_{1L}+2\mathrm{\&pi;fi}{z}_{1L}{z}_{2L}/K_N}{z_{2L}-z_{1L}+2\mathrm{\&pi;fi}{z}_{1L}{z}_{2L}/K_N}+\left(\frac{z_{2L}-z_{1L}+2\mathrm{\&pi;fi}{z}_{1L}{z}_{2L}/K_N}{z_{2L}+z_{1L}-2\mathrm{\&pi;fi}{z}_{1L}{z}_{2L}/K_N}\right)e^{-2i{k}_{2}d}}{1+\left(\frac{z_{2L}-z_{1L}+2\mathrm{\&pi;fi}{z}_{1L}{z}_{2L}/K_N}{z_{2L}+z_{1L}-2\mathrm{\&pi;fi}{z}_{1L}{z}_{2L}/K_N}\right)\left(\frac{z_{2L}-z_{1L}+2\mathrm{\&pi;fi}{z}_{1L}{z}_{2L}/K_N}{z_{2L}+z_{1L}-2\mathrm{\&pi;fi}{z}_{1L}{z}_{2L}/K_N}\right)e^{-2i{k}_{2}d}}\right|---\left(7\right)$

Wherein, K _NNormal stiffness coefficient for bonding interface; R ₂And R ₃Be respectively bonding interface once and reflection coefficient repeatedly; D is a thickness of adhibited layer; k ₂Be wave number;

To expression formula (7) minimizing, thereby obtain expression formula (8):

$\mathrm{fd}=\frac{c_{2L}(2n-1)}{4}\&times;{10}^3,n=\mathrm{1,2,3}...---\left(8\right)$

Wherein, n is the exponent number of resonance frequency, and after n was selected, the product of resonance frequency and thickness of adhibited layer was a constant, and d is a millimeter for thickness of adhibited layer unit; Bring the resonance frequency that to determine in the expression formula (8) that bonding interface rigidity detects into by the longitudinal wave velocity of adhesive linkage medium;

Step 2): produce the Gauss pulse ripple that centre frequency is adjustable by function generator (4), excitation frequency is the resonance frequency that step 1) obtains;

Step 3): pumping signal is imported stimulus sensor (2) into after power amplifier (3) carries out power amplification;

Step 4): stimulus sensor (2) Gauss pulse ripple signal imports in the bonded structure (1) constantly to be propagated, and makes its repeatedly reflection in bonded structure (1);

Step 5): stimulus sensor (2) receives the signal after the Gauss pulse ripple repeatedly reflects in bonded structure (1), goes up at oscillograph (5) to show, and stores in the computing machine (6);

Step 6): utilize the one dimension analysis method of wavelet packet that the time-domain signal that receives is carried out denoising Processing, analyze the echo of Gauss pulse echo in bonding solid interface, bring in the expression formula (7) thickness of adhibited layer, resonance frequency and reflection coefficient are counter respectively, can draw the rigidity of bonding interface.

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