CN104765062A - Ballastless track board disengaging nondestructive detection method based on elastic waves - Google Patents

Abstract

The invention discloses a ballastless track board disengaging nondestructive detection method based on elastic waves. By means of confirming a function relationship between shock excitation elastic wave frequency and disengaging surface elastic wave reflectance, a function relationship between the shock excitation elastic wave frequency and packing layer elastic wave reflectance is confirmed, the shock excitation elastic wave frequency which can make the ratio of the disengaging surface elastic wave reflectance to the packing layer elastic wave reflectance obtain the maximum value is found, shock excitation elastic wave with the frequency is directly stimulated, so that a disengaging surface reflected signal is in a state easiest to identify, and the disengaging judgment accuracy of a ballastless track board is greatly improved. On the basis, a judging standard whether the disengaging exits is provided at the same time. The invention further discloses a ballastless track board disengaging rate detection method based on the elastic waves.

Description

Fragment-free track slab based on elastic wave comes to nothing lossless detection method

Technical field

The present invention relates to safety detection technology field, be specifically related to fragment-free track slab Method of Void.

Background technology

Non-fragment orbit eliminates sleeper and the railway roadbed of traditional Ballast track, adopts the direct supporting rail of prefabricated armoured concrete slab, and between top board and base, fill CA mortar or self-compacting concrete bed course, is a kind of slab track structure of brand-new comprehensive support.It has the following advantages: stability, ride comfort are good; Building height is low, from heavy and light, can reduce bridge second phase load and reduce tunnel clearance; Track deformation is slow, good endurance; Do not need repairing or few maintenance and the advantage such as maintenance cost is low.The requirement of non-fragment orbit to construction material and basic civil engineering is all very high, and therefore primary construction expense is higher than Ballast track, but its good stability, long service life.Therefore, in special line for passenger trains, adopt platy ballastless track structure to become prevailing model and the inexorable trend of present high speed railway construction.

The plate-type ballastless track of current employing has three kinds of versions:

CRTS I type: be made up of parts such as concrete bed, CA screed, track plates, convex blocking platforms, the effect of convex blocking platform is that horizontal and vertical movement occurs prevention unit track plates;

CRTS II type: compared with I type, the structure of its track plates is continuous print, does not have convex blocking platform.The long 6450mm of on-gauge plate, wide 2550mm, the thickness 200mm of CRTS II type fragment-free track slab, concrete design strength is C55.Track plates landscape configuration 60 deformed bars, longitudinally configuration 6 is by 20 finish rolling deformed bars. and the longitudinal direction for track plates connects, and configures one deck reinforced mesh respectively at the upper and lower layer of vertical, horizontal reinforcing bar, and insulation processing is all done in all reinforcing bar point of crossing;

CRTS III type: General structure scheme is the Novel unit platy ballastless track structure of shouldered, primarily of part compositions such as the self-compacting concrete (self-leveling concrete packed layer) of rail, fastener, precast track plate, arrangement of reinforcement, limiting block platform, intermediate isolating layer (geotextile) and reinforced concrete footings.The long 5350mm of on-gauge plate, wide 2500mm, thickness 190 ~ 210mm, concrete design strength is generally C60.

These three kinds of plate-type ballastless track plates have a common feature, namely as shown in Figure 1, arrange packed layer 1 (also claiming adjustment layer) between top board 2 (also claiming track plates) and base plate 3 (also claiming base).This packed layer mainly plays following effect:

(1) fill adjustment: comprehensively, supporting rail guidance tape equably, and be convenient to the height adjusting track, improve maintainability when operating efficiency and infrastructure distortion;

(2) load power transmission: bear the vertical force that transmitted by track plates and horizontal force in length and breadth, and disperseed to pass to base and stop means.

The state of packed layer directly affects the life-span of track plates and the driving safety of train.Due to the aspects such as effect of construction quality, train load and temperature, between top board and packed layer, there will be mutual disengaging (that is the phenomenon of coming to nothing), the stress of structure is worsened.Time serious, also may there is warping phenomenon in track plates, further the traffic safety of harm train.As the structural representation that Fig. 1 and packed layer 1 come to nothing with top board 2.As Fig. 2 and packed layer 1 breakage cause the structural representation come to nothing.

At present, following a few class can be roughly divided into about the detection technique of coming to nothing:

(1) based on far infrared imaging: the uncontinuity of main test material heat conductivility, utilizes the temperature variation that insolation produces, usually by inferring the presence or absence of coming to nothing to the temperature imaging of body structure surface.

(2) based on electromagnetic wave (concrete radar): main test material lures the uncontinuity of electrical property (conductance), the reflection of electromagnetic wave on different medium face of launching is utilized to infer the presence or absence of coming to nothing.

(3) based on mechanical wave or mechanical vibration such as vibration, ultrasound wave, elastic waves: these three kinds of methods are all the uncontinuities utilizing characteristic of material mechanics, infer the presence or absence of coming to nothing respectively by the change of mode of oscillation, the presence or absence etc. of reflected signal.Specifically comprise again:

Based on methods such as vibrations: the method utilizes the modes such as hammering to bring out the free vibration of track plates, the presence or absence of coming to nothing is inferred in the change of the static mode utilizing the change of interlaminar bonding condition (boundary condition) to cause.When occurring coming to nothing, the bond area of track plates and packed layer declines to causing to retrain and reduces, and then reducing appears in the natural frequency of vibration of track plates;

Method based on ultrasound wave and elastic wave: the acoustic impedance in face of coming to nothing will well below sound position, and therefore, namely the ultrasound wave excited or elastic wave can produce reflection on the face of coming to nothing.

Said method, when detecting track plates and coming to nothing, due to the characteristic of track plates, makes the applicability of often kind of method be greatly limited.Wherein, based on the method for far infrared, electromagnetic microwave and induced vibration, due to the relation of test medium essence, it is made to be difficult to be applied in track plates vacant analysis.

What the method based on far infrared imaging can detect comes to nothing the degree of depth generally within 10cm, and need in the morning and detect (temperature Change is now the fastest) at dusk, therefore the detection (due to the relation be open to traffic, the detection of line upper plate can only 1 o'clock to 4 o'clock night) of track plates cannot be applicable to.

Detection method based on electromagnetism radar is very large by the impact of metal medium, and gather in track plates a large amount of reinforcing bars and presstressed reinforcing steel, and have the impact of rail.Therefore, electromagnetism radar is difficult to the detection being applicable to track plates.

Method based on vibration needs the free vibration of ductor.Because the quality of plate is comparatively large, therefore, the free vibration bringing out plate needs larger energy.Particularly track plates on line, due to the constraint of rail, makes bringing out of track plates more difficult.

Comparatively speaking, the method for testing based on acoustic impedance change being representative with ultrasound wave, impact elasticity ripple, has feasibility in theory.

But also there is following problem in supercritical ultrasonics technology:

(1) need during test to pop one's head in and to be coupled with the couplant such as tested surface butter, testing efficiency is low.

(2) excitation signal energy is low, signal frequency is high (generally at hundreds of more than KHz), and in track plates, decay is fast, detects the degree of depth more shallow.Meanwhile, affect larger by aggregate, reinforcing bar in concrete.

(3) velocity of wave that ultrasound wave is propagated in track plates changes greatly, generally at 4.5 ~ 5.5km/s.

(4) rectilinearity of the spectral response curve of popping one's head in is poor, is difficult to carry out frequency-domain analysis.

To sum up, utilizing elastic wave test fragment-free track slab to come to nothing is more satisfactory method.But because the acoustic impedance of packed layer (CA mortar or self-compacting concrete) will lower than the acoustic impedance of track plates, therefore, the impact elasticity ripple excited, when running into packed layer, also can produce reflection.The reflected signal of packed layer and the reflected signal in face of coming to nothing mix, for the identification of face reflection of coming to nothing brings very large difficulty.In addition, whether, be also problem demanding prompt solution if how to be come to nothing to fragment-free track slab by reflected signal and rationally judging.

Summary of the invention

Namely object of the present invention is to overcome the deficiencies in the prior art, provides a kind of fragment-free track slab based on elastic wave to come to nothing lossless detection method.The method, by optimizing excited frequency, improves the recognition capability of the face reflected signal that comes to nothing, and this method also judges by coming to nothing that threshold realizes whether coming to nothing to fragment-free track slab rationally judging simultaneously.

Another object of the present invention is to provide a kind of fragment-free track slab based on elastic wave to come to nothing rate detection method.

Object of the present invention is achieved through the following technical solutions:

Fragment-free track slab based on elastic wave comes to nothing lossless detection method, comprises the steps:

A. the funtcional relationship determined exciting elastic wave frequency and come to nothing between surface elastic wave reflection rate;

B. the funtcional relationship between exciting elastic wave frequency and packed layer elastic wave reflex rate is determined;

C. according to the funtcional relationship that steps A and step B obtain, draw based on exciting elastic wave frequency and x-Y axial coordinate figure, find out the exciting elastic wave frequency that each crest is corresponding;

D. each crest of reduction is corresponding value, obtains the judgement threshold of coming to nothing under the exciting elastic wave frequency that each crest is corresponding;

E. utilize exciting device to carry out exciting to the measuring point on top board, produce a kind of exciting elastic wave possessed in frequency described in step C, D;

F. measuring point elastic wave reflex rate is obtained according to exciting elastic wave and reflection elastic wave, as be greater than the judgement threshold of coming to nothing that exciting elasticity wave frequency is corresponding, then come to nothing in this measuring point place.

Further, in described steps A, determine exciting elastic wave frequency and the method for the funtcional relationship between surface elastic wave reflection rate of coming to nothing as follows:

By $R_V=2\left|\cos \right(\frac{2H\·f_S\·\mathrm{\π}}{V_p}\left)\right|$

φ＝4πf _SH/V _p＝2πf _ST

Obtain: R _v=2|cos (φ/2) |;

When φ is 2N π, the face reflected signal of coming to nothing is the strongest, and surface elastic wave reflection rate of coming to nothing is the highest, is 200%;

When φ is (2N+1) π, the face reflected signal of coming to nothing is the most weak, and surface elastic wave reflection rate of coming to nothing is minimum, is 0;

Wherein: R _vfor surface elastic wave reflection rate of coming to nothing, φ is the phase differential of top board reflected signal and accumulation signal, f _sfor exciting elastic wave frequency, N is integer, and T is the reciprocal time of elastic wave in top board, T=2H/V _p, H is the thickness of top board, V _pfor the velocity of wave of top board Elastic Wave.

Further, in described step B, determine that the method for the funtcional relationship between exciting elastic wave frequency and packed layer elastic wave reflex rate is as follows:

$R_F=\sqrt{1-\frac{4{z_1}^2{z_2}^2}{4{z_1}^2{z_2}^2{\cos }^2\left(k_{2}L\right)+{({z_1}^2+{z_2}^2)}^2{\sin }^2\left(k_{2}L\right)}}$

z ₁＝ρ ₁·V _p1

z ₂＝ρ ₂·V _p2

Wherein, R _ffor packed layer elastic wave reflex rate, f _sfor exciting elastic wave frequency, k ₂=2 π f _s/ V _p2, ρ ₁for the density of top board, ρ ₂for packed layer density, V _p1for the velocity of wave of top board Elastic Wave, V _p2for the velocity of wave of packed layer Elastic Wave, L is the thickness of packed layer, z ₁for the mechanical impedance of elastic wave in top board, z ₂for the mechanical impedance of elastic wave in packed layer.

Further, in described step D, come to nothing and judge that the defining method of threshold is as follows:

κ＝1+(η-1)ψ；

Wherein, κ is judgement threshold of coming to nothing, and ψ is the reduction coefficient under the exciting elastic wave frequency that crest is corresponding, and η is that crest is corresponding value.

Further, in described step e, exciting device is configured as follows:

$f_s=\frac{1.25}{T_c};$

Wherein, f _sexciting elastic wave frequency, T _cfor the duration of contact of exciting device and top board;

$T_c=4.53{\left[\frac{({\mathrm{\δ}}_1+{\mathrm{\δ}}_2)m_1}{\sqrt{R_1{v}_0}}\right]}^{2/5};$

${\mathrm{\δ}}_1=\frac{1-{{\mathrm{\μ}}_1}^2}{E_1\mathrm{\π}};$

${\mathrm{\δ}}_2=\frac{1-{{\mathrm{\μ}}_2}^2}{E_2\mathrm{\π}};$

Wherein, E ₁for exciting device hits the elastic modulus of spheroid, E ₂for concrete elastic modulus, μ ₁the Poisson ratio of the material of spheroid is hit, μ for forming exciting device ₂for concrete Poisson ratio, m ₁for the quality of exciting device, R ₁for exciting device hits the radius-of-curvature of spheroid, v ₀for speed when exciting device and top board collide.

Another object of the present invention is achieved through the following technical solutions:

Fragment-free track slab based on elastic wave comes to nothing rate detection method, comprises the steps:

A. grid division on top board, each grid is a measuring point;

B. adopt any one fragment-free track slab based on elastic wave above-mentioned to come to nothing lossless detection method, respectively each measuring point is detected;

C. calculate the ratio that the measuring point come to nothing accounts for all measuring points, this ratio is fragment-free track slab and comes to nothing rate.

Advantage of the present invention and beneficial effect are:

1. the present invention is by the funtcional relationship determining exciting elastic wave frequency and come to nothing between surface elastic wave reflection rate, determines the funtcional relationship between exciting elastic wave frequency and packed layer elastic wave reflex rate, finds and can make obtain the exciting elastic wave frequency of maximal value, directly excite the exciting elastic wave possessing this frequency, the face reflected signal that so can make to come to nothing is in the state be the most easily identified, greatly improves fragment-free track slab and to come to nothing the accuracy judged.

2. the present invention is corresponding by each crest of reduction value, obtains the judgement threshold of coming to nothing under the exciting elastic wave frequency that each crest is corresponding, judging that threshold judges whether measuring point place comes to nothing, can obtain rationally judged result accurately by coming to nothing.

3. by the present invention fragment-free track slab come to nothing and detects, testing result with take off plate and verify that situation is consistent.

Accompanying drawing explanation

In order to be illustrated more clearly in embodiments of the invention, be briefly described to the accompanying drawing used required for describing in the embodiment of the present invention below.Apparent, the accompanying drawing in the following describes is only some embodiments recorded in the present invention, to those skilled in the art, when not paying creative work, according to accompanying drawing below, can also obtain other accompanying drawing.

Fig. 1 is the structural representation that packed layer and top board come to nothing;

Fig. 2 is that packed layer breakage causes the structural representation come to nothing;

Fig. 3 is the elastic wave frequency domain reflection characteristic in face of coming to nothing;

Fig. 4 is the repeatedly repeated reflection principle schematic of packed layer;

Fig. 5 is the elastic wave frequency domain reflection characteristic of packed layer;

Fig. 6 be based on exciting elastic wave frequency and x-Y axial coordinate figure;

Wherein, the parts title that Reference numeral is corresponding is as follows:

1-packed layer, 2-top board, 3-base plate.

Embodiment

In order to make those skilled in the art understand the present invention better, below in conjunction with the accompanying drawing in the embodiment of the present invention, clear, complete description is carried out to the technical scheme in the embodiment of the present invention.Apparent, embodiment described below is only the part in the embodiment of the present invention, instead of all.Based on the embodiment that the present invention records, other all embodiment that those skilled in the art obtain when not paying creative work, all in the scope of protection of the invention.

Embodiment 1:

The present embodiment is for CRTS II type fragment-free track slab (lower abbreviation II type) and CRTS III type fragment-free track slab (lower abbreviation III type), and the present invention will be described.Nature, the present invention also can be used for the vacant analysis that other possesses the fragment-free track slab of similar structures.

The parameter of various fragment-free track slab packed layer

Fragment-free track slab based on elastic wave comes to nothing lossless detection method, comprises the steps:

A. the funtcional relationship determined exciting elastic wave frequency and come to nothing between surface elastic wave reflection rate;

B. the funtcional relationship between exciting elastic wave frequency and packed layer elastic wave reflex rate is determined;

C. according to the funtcional relationship that steps A and step B obtain, draw based on exciting elastic wave frequency and x-Y axial coordinate figure, find out the exciting elastic wave frequency that each crest is corresponding;

D. each crest of reduction is corresponding value, obtains the judgement threshold of coming to nothing under the exciting elastic wave frequency that each crest is corresponding;

E. utilize exciting device to carry out exciting to the measuring point on top board, produce a kind of exciting elastic wave possessed in frequency described in step C, D;

F. measuring point elastic wave reflex rate is obtained according to exciting elastic wave and reflection elastic wave, as be greater than the judgement threshold of coming to nothing that exciting elasticity wave frequency is corresponding, then come to nothing in this measuring point place.

In described steps A, determine exciting elastic wave frequency and the method for the funtcional relationship between surface elastic wave reflection rate of coming to nothing as follows:

By $R_V=2\left|\cos \right(\frac{2H\·f_S\·\mathrm{\π}}{V_p}\left)\right|$

φ＝4πf _SH/V _p＝2πf _ST

Obtain: R _v=2|cos (φ/2) |;

When φ is 2N π, the face reflected signal of coming to nothing is the strongest, and surface elastic wave reflection rate of coming to nothing is the highest, is 200%;

When φ is (2N+1) π, the face reflected signal of coming to nothing is the most weak, and surface elastic wave reflection rate of coming to nothing is minimum, is 0;

Wherein: R _vfor surface elastic wave reflection rate of coming to nothing, φ is the phase differential of top board reflected signal and accumulation signal, f _sfor exciting elastic wave frequency, N is integer, and T is the reciprocal time of elastic wave in top board, T=2H/V _p, H is the thickness of top board, V _pfor the velocity of wave of top board Elastic Wave.

Below it will be appreciated by those skilled in the art that, its principle is specifically described.

For the reflection in the face of coming to nothing, although reflectivity itself is with incoming signal frequency, it doesn't matter, is total reflection (namely incident signal all reflects).But in the test of reality, the impact of residual vibration during owing to exciting, to test the signal that obtains be reflected signal and the superposing of residual accumulation signal.Therefore, between incoming signal from reflected signal, phase differential is different, can make to test the signal obtained and occur to strengthen or weaken.

Incoming signal x _s(t) be:

x _s(t)＝Asin(2πf _st)

A represents the amplitude of incoming signal.

The time T that it reflects in top board (namely one back and forth) is by top plate thickness H and wherein Elastic Wave Velocity V _pdetermine:

T＝2H/V _p

Consider that the reflection of coming to nothing is same-phase total reflection, therefore, the reflected signal x received _rt () is equivalent to incoming signal a phase delay φ:

Therefore, signal x (t) received after the T moment is:

x(t)＝x _s(t)+x _R(t)＝Asin(2πf _st)+Asin(2πf _st+φ)

So, when φ is 2N π (N is integer), that is

$f_s=\frac{N}{T}={\mathrm{Nf}}_R$

X _s(t) and x _rt () Downward addition, x (t) is now the strongest.F _rfor reflected signal frequency.

But when if φ is (2N+1) π (N is integer), that is

$f_s=\frac{2N+1}{2T}=\frac{2N+1}{2}{f}_R$

X _s(t) and x _rt () reverse superposition, x (t) is now the most weak.

Therefore, f is worked as _swith f _ridentical, or f _sf _rintegral multiple time, reflected signal and residual accumulation signal in-phase stacking, now test the reflected signal that obtains the strongest, if do not considered decay, levels off to 2 times of incoming signals, i.e. maximum reflectivity R in theory _v=2, also referred to as longitudinal resonance.And f _sfor f _r0.5 times, 1.5 times, 2.5 ... times time, test the reflected signal that obtains the most weak, level off to 0 in theory.

Come to nothing face elastic wave frequency domain reflection characteristic as shown in Figure 3.

Because top plate thickness H is generally 0.2m, V _pgeneral at 4.0 ~ 4.4km/s, the exciting elastic wave frequency when face reflected signal that can come to nothing is the strongest.

Exciting elastic wave frequency (KHz) when the face reflected signal of coming to nothing is the strongest

In step B, determine that the method for the funtcional relationship between exciting elastic wave frequency and packed layer elastic wave reflex rate is as follows:

$R_F=\sqrt{1-\frac{4{z_1}^2{z_2}^2}{4{z_1}^2{z_2}^2{\cos }^2\left(k_{2}L\right)+{({z_1}^2+{z_2}^2)}^2{\sin }^2\left(k_{2}L\right)}}$

z ₁＝ρ ₁·V _p1

z ₂＝ρ ₂·V _p2

Wherein, R _ffor packed layer elastic wave reflex rate, f _sfor exciting elastic wave frequency, k ₂=2 π f _s/ V _p2, ρ ₁for the density of top board, ρ ₂for packed layer density, V _p1(be equal to above-mentioned V _p) be the velocity of wave of top board Elastic Wave, V _p2for the velocity of wave of packed layer Elastic Wave, L is the thickness of packed layer, z ₁for the mechanical impedance of elastic wave in top board, z ₂for the mechanical impedance of elastic wave in packed layer.

Below it will be appreciated by those skilled in the art that, its principle is specifically described.

For the reflected signal in packed layer 1, due to the existence of interlayer, can there is continuous reflection in incoming signal, makes the phase place of its reflected signal not single, but the superposition of multiple phase signal.The repeatedly repeated reflection principle of packed layer 1 as shown in Figure 4.In Fig. 4, arrow represents the bang path of signal.

Work as x _safter (t) incidence, reflected signal x _rft () can be expressed as the superposition of multiple signal:

Wherein, R _ffor packed layer elastic wave reflex rate;

T _ffor transmitance, have:

Wherein, phase delay for:

D (being equal to above-mentioned L) and V _pD(be equal to above-mentioned V _p2) be respectively thickness and the packed layer Elastic Wave velocity of wave of packed layer.For II template, be 0.03m and 2200m/s respectively; For III template, be then 0.10m and 3400m/s respectively.Through calculating, can obtain:

For II template,

For III template,

Due to phase delay existence, make the reflected signal x of packed layer _rfthe reflectivity R of (t) _fcan be expressed as follows with the relation of exciting elastic wave frequency:

$R_F=\sqrt{1-\frac{4{z_1}^2{z_2}^2}{4{z_1}^2{z_2}^2{\cos }^2\left(k_{2}L\right)+{({z_1}^2+{z_2}^2)}^2{\sin }^2\left(k_{2}L\right)}}$

Different exciting elastic wave frequency f can be obtained thus _swith reflectivity R _frelation, as shown in Figure 5.

From the reflected signal of packed layer, identify that the key of face reflected signal of coming to nothing just is, the ratio η of how to make to come to nothing surface elastic wave reflection rate and packed layer elastic wave reflex rate maximizes.

$\mathrm{\η}=\frac{R_V}{R_F}$

After completing steps A and step B, according to the funtcional relationship that steps A and step B obtain, draw based on exciting elastic wave frequency and x-Y axial coordinate figure, find out the exciting elastic wave frequency that each crest is corresponding.

Based on exciting elastic wave frequency and x-Y axial coordinate figure as shown in Figure 6.In Fig. 6, be worth higher, show that the exciting elastic wave of this frequency is more conducive to detection and comes to nothing.Can find out, work as f _stime near 11.5KHz, 21KHz, 31KHz etc., be conducive to the detection of coming to nothing most.

Because above-mentioned surface elastic wave reflection rate and the packed layer elastic wave reflex rate of coming to nothing is theoretical value, consider the decay of exciting elastic wave, and the impact of the face area that comes to nothing, therefore, this theoretical value is bigger than normal compared with actual value, needs in addition reduction to obtain judgement threshold of coming to nothing.

κ＝1+(η-1)ψ

Wherein, κ is judgement threshold of coming to nothing, and ψ is the reduction coefficient under the exciting elastic wave frequency that crest is corresponding.

ψ by carrying out demonstration test to the fragment-free track slab of known position of coming to nothing, carries out contrast draw detecting obtain actual come to nothing surface elastic wave reflection rate and packed layer elastic wave reflex rate of surface elastic wave reflection rate and packed layer elastic wave reflex rate and the theory calculated of coming to nothing.

For II template, ψ desirable 0.3 ~ 0.4;

For III template, ψ desirable 0.20 ~ 0.25.

Different coming to nothing of exciting elastic wave frequency judges threshold κ

Excited frequency (KHz)	II type	III type
			11.5	1.7～2.0	2.7～3.2
21	1.4～1.5	2.4～2.8

In order to the exciting elastic wave enabling exciting device produce corresponding frequencies, exciting device can be configured by the following method.

The principal element of decision exciting elastic wave frequency is in exciting process, T duration of contact of exciting device and top board _c.

Duration of contact T _cas follows with the relation of the exciting elastic wave free running frequency caused:

$f_s=\frac{1.25}{T_c};$

Wherein, f _sexciting elastic wave frequency, T _cfor the duration of contact of exciting device and top board.

On the other hand, duration of contact T _cdepend primarily on the factors such as the quality of exciting device, the radius-of-curvature of front end and impact dynamics (speed during contact).For the excitation head of spheroidal, T _c(unit: s) can be expressed as:

$T_c=4.53{\left[\frac{({\mathrm{\δ}}_1+{\mathrm{\δ}}_2)m_1}{\sqrt{R_1{v}_0}}\right]}^{2/5};$

${\mathrm{\δ}}_1=\frac{1-{{\mathrm{\μ}}_1}^2}{E_1\mathrm{\π}};$

${\mathrm{\δ}}_2=\frac{1-{{\mathrm{\μ}}_2}^2}{E_2\mathrm{\π}};$

Wherein, E ₁for exciting device hits the elastic modulus of spheroid, E ₂for concrete elastic modulus, μ ₁the Poisson ratio of the material of spheroid is hit, μ for forming exciting device ₂for concrete Poisson ratio, m ₁for the quality of exciting device, R ₁for exciting device hits the radius-of-curvature of spheroid, v ₀for speed when exciting device and top board collide.

Therefore, as long as be aware of the quality of exciting device, speed when radius-of-curvature that exciting device hits spheroid and exciting device and top board collide, the natural frequency of vibration of exciting elastic wave can be extrapolated.

The present embodiment, using spheroidal stainless steel hammer body as exciting device, under different impact velocity (being converted to free height of fall), excites the sphere diameter required by exciting elastic wave of required frequency as shown in the table:

When actual job, larger exciting device is less by the impact of concrete surface state, and accumulation signal is more stable, therefore can the larger exciting device of prioritizing selection sphere diameter.

After the above step is finished, exciting device can be utilized to carry out exciting to the measuring point on top board, produce a kind of exciting elastic wave possessed in 11.5KHz, 21KHz, 31KHz frequency.Concrete steps are: sensor (generally can select acceleration transducer) is installed (general available artificial or alternate manner press against) on measuring point, with producing the exciting device of exciting elastic wave of corresponding frequencies at sensor proximity exciting, detect accumulation signal and reflected signal and record by sensor.

Measuring point elastic wave reflex rate is calculated by the intensitometer of accumulation signal and reflected signal, as be greater than the judgement threshold of coming to nothing under corresponding exciting elastic wave frequency, then come to nothing in measuring point place.

Embodiment 2:

Fragment-free track slab based on elastic wave comes to nothing rate detection method, comprises the steps:

A. grid division on top board, each grid is a measuring point;

B. adopt the method described in embodiment 1, respectively each measuring point is detected;

C. calculate the ratio that the measuring point come to nothing accounts for all measuring points, this ratio is fragment-free track slab and comes to nothing rate.

As mentioned above, just the present invention can be realized preferably.

Claims (6)

1. to come to nothing lossless detection method based on the fragment-free track slab of elastic wave, it is characterized in that, comprise the steps:

A. the funtcional relationship determined exciting elastic wave frequency and come to nothing between surface elastic wave reflection rate;

B. the funtcional relationship between exciting elastic wave frequency and packed layer elastic wave reflex rate is determined;

C. according to the funtcional relationship that steps A and step B obtain, draw based on exciting elastic wave frequency and x-Y axial coordinate figure, find out the exciting elastic wave frequency that each crest is corresponding;

D. each crest of reduction is corresponding value, obtains the judgement threshold of coming to nothing under the exciting elastic wave frequency that each crest is corresponding;

E. utilize exciting device to carry out exciting to the measuring point on top board, produce a kind of exciting elastic wave possessed in frequency described in step C, D;

F. obtain measuring point elastic wave reflex rate according to exciting elastic wave and reflection elastic wave, as strong survey entirely the elastic wave-wave of the place of putting bullet reflect the rate rate of penetrating and be greater than judgement threshold of coming to nothing corresponding to exciting elasticity wave frequency, then come to nothing in this measuring point place.

2. the fragment-free track slab based on elastic wave according to claim 1 comes to nothing lossless detection method, it is characterized in that, in described steps A, determine exciting elastic wave frequency and the method for the funtcional relationship between surface elastic wave reflection rate of coming to nothing as follows:

By $R_V=2\left|\cos \left(\frac{2H\·f_s\·\mathrm{\π}}{V_p}\right)\right|$

φ＝4πf _SH/V _p＝2πf _ST

Obtain: R _v=2|cos (φ/2) |;

When φ is 2N π, the face reflected signal of coming to nothing is the strongest, and surface elastic wave reflection rate of coming to nothing is the highest, is 200%;

When φ is (2N+1) π, the face reflected signal of coming to nothing is the most weak, and surface elastic wave reflection rate of coming to nothing is minimum, is 0;

Wherein: R _vfor surface elastic wave reflection rate of coming to nothing, φ is the phase differential of top board reflected signal and accumulation signal, f _sfor exciting elastic wave frequency, N is integer, and T is the reciprocal time of elastic wave in top board, T=2H/V _p, H is the thickness of top board, V _pfor the velocity of wave of top board Elastic Wave.

3. the fragment-free track slab based on elastic wave according to claim 1 comes to nothing lossless detection method, it is characterized in that, in described step B, determines that the method for the funtcional relationship between exciting elastic wave frequency and packed layer elastic wave reflex rate is as follows:

$R_F=\sqrt{1-\frac{{{4z}_1}^2{z_2}^2}{{{4z}_1}^2{z_2}^2{\cos }^2\left(k_{2}L\right)+{({z_1}^2+{z_2}^2)}^2{\sin }^2\left(k_{2}L\right)}}$

z ₁＝ρ ₁·V _p1

z ₂＝ρ ₂·V _p2

Wherein, R _ffor packed layer elastic wave reflex rate, f _sfor exciting elastic wave frequency, k ₂=2 π f _s/ V _p2, ρ ₁for the density of top board, ρ ₂for packed layer density, V _p1for the velocity of wave of top board Elastic Wave, V _p2for the velocity of wave of packed layer Elastic Wave, L is the thickness of packed layer, z ₁for the mechanical impedance of elastic wave in top board, z ₂for the mechanical impedance of elastic wave in packed layer.

4. the fragment-free track slab based on elastic wave according to claim 1 comes to nothing lossless detection method, it is characterized in that, in described step D, comes to nothing and judges that the defining method of threshold is as follows:

κ＝1+(η-1)ψ _；

Wherein, κ is judgement threshold of coming to nothing, and ψ is the reduction coefficient under the exciting elastic wave frequency that crest is corresponding, and η is that crest is corresponding value.

5. to come to nothing lossless detection method according to the fragment-free track slab based on elastic wave in Claims 1 to 4 described in any one, it is characterized in that, in described step e, exciting device is configured as follows:

$f_s=\frac{1.25}{T_c};$

Wherein, f _sexciting elastic wave frequency, T _cfor the duration of contact of exciting device and top board;

$T_c=4.53{\left[\frac{({\mathrm{\δ}}_1+{\mathrm{\δ}}_2)m_1}{\sqrt{R_1{v}_0}}\right]}^{2/5};$

${\mathrm{\δ}}_1=\frac{1-{{\mathrm{\μ}}_1}^2}{E_1\mathrm{\π}};$

${\mathrm{\δ}}_2=\frac{1-{{\mathrm{\μ}}_2}^2}{E_2\mathrm{\π}};$

Wherein, E ₁for exciting device hits the elastic modulus of spheroid, E ₂for concrete elastic modulus, μ ₁the Poisson ratio of the material of spheroid is hit, μ for forming exciting device ₂for concrete Poisson ratio, m ₁for the quality of exciting device, R ₁for exciting device hits the radius-of-curvature of spheroid, v ₀for speed when exciting device and top board collide.

6. to come to nothing rate detection method based on the fragment-free track slab of elastic wave, it is characterized in that, comprise the steps:

A. grid division on top board, each grid is a measuring point;

B. adopt the method in Claims 1 to 5 described in any one, respectively each measuring point is detected;

C. calculate the ratio that the measuring point come to nothing accounts for all measuring points, this ratio is fragment-free track slab and comes to nothing rate.