CN107449664B - The method for measuring concrete absolute stress under uniaxial compression using scattered ultrasonic wave method - Google Patents
The method for measuring concrete absolute stress under uniaxial compression using scattered ultrasonic wave method Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0014—Type of force applied
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- G01N2203/0019—Compressive
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/0058—Kind of property studied
- G01N2203/0069—Fatigue, creep, strain-stress relations or elastic constants
- G01N2203/0075—Strain-stress relations or elastic constants
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- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N2203/02—Details not specific for a particular testing method
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Abstract
The invention discloses a kind of methods for measuring concrete absolute stress under uniaxial compression using scattered ultrasonic wave method, comprising: Step 1: providing the progress scattered ultrasonic wave test under the first loaded mode with the consistent standard concrete test block of concrete component to be measured；Step 2: the original waveform figure and scattered wave travel-time difference change rate that are plotted under each loading status and stress relation curve；Step 3: carrying out scattered ultrasonic wave test to concrete component to be measured under the second loaded mode, which is contained in the first loaded mode；Step 4: drawing original waveform figure and scattered wave travel-time difference change rate and stress relation curve of the concrete component to be measured under each loading status；Step 5: finding scattered wave travel-time difference change rate and initial position of the stress relation curve on the curve of the standard concrete test block of the concrete component to be measured, the corresponding stress value in the initial position is absolute stress.The present invention can assess the absolute stress of concrete component to be measured.
Description
Technical field
The present invention relates to concrete nondestructive testing fields more particularly to a kind of application scattered ultrasonic wave method to measure uniaxial compression
The method of lower concrete absolute stress.
Background technique
Due to the complexity of concrete material, reflection, refraction and the scattering etc. of complexity can occur wherein propagating for ultrasonic wave
Phenomenon, therefore challenge very greatly is brought to the variation of precise measurement ultrasonic velocity, scattered ultrasonic wave method just can solve this hardly possible
Topic has the advantages that high-precision and high sensitivity to measurement concrete minimal stress variation.
Scattered ultrasonic wave method studies medium using the scattered wave that Multiple Scattering is formed, since propagation path is longer,
Therefore the minor change inside concrete medium can be amplified, therefore very sensitive to the faint variation of inside configuration, and it is normal
Rule method is then only able to detect the large change of critical state.
From the point of view of theoretical research and practical engineering application situation, scattered ultrasonic wave method detection technique has high sensitivity, misses
The advantages that difference small, favorable repeatability.But since this method is quite sensitive to media variations, to exclude during the test stress it
Outer influence, calibrates test.There are a degree of damages for active service concrete bridge structure.Mainly pass through detection at present
Crack, cavity, internal steel bar corrosion situation determine its degree of injury, but the above parameter can not directly reflect concrete structure
Real bearing state.Section stress under concrete-bridge permanent action is the key index for evaluating servicing bridges bearing capacity,
The measurement problem of section stress is not solved effectively always, causes in the detection process not holding existing concrete bridges
Loading capability is accurately assessed.The present invention is intended to provide method is assessed in a kind of high-precision concrete structure stress non-destructive testing.
Summary of the invention
In view of the above technical problems, the present invention provides a kind of high application scattered ultrasonic wave method measurement of measurement accuracy is uniaxial
By the method for pressure concrete absolute stress.
Technical solution provided by the invention are as follows:
A method of using concrete absolute stress under ultrasonic scattering wave measurement uniaxial compression, comprising:
Step 1: one and the consistent standard concrete test block of concrete component to be measured are provided, under the first loaded mode
Scattered ultrasonic wave test is carried out to the standard concrete test block, the initial loading load of the first loaded mode is 0；
Step 2: the ultrasonic wave original waveform data to the standard concrete test block is analyzed, detailed process includes:
It is every in the loaded mode of step (1) first to walk to obtain a loading status by a load, it is plotted in the standard concrete test block
Original waveform figure under each loading status；Step (2) utilizes original wave of the standard concrete test block under each loading status
Shape figure calculates scattered wave travel-time difference change rate, and draws out the scattered wave travel-time difference change rate and stress of the standard concrete test block
Relation curve；
Step 3: carrying out scattered ultrasonic wave test to concrete component to be measured under the second loaded mode, this is second loaded
The initial loading load of mode is not 0, and the second loaded mode is contained in the first loaded mode；During the test,
Acquire the ultrasonic wave original waveform data of the concrete component to be measured；
Step 4: the ultrasonic wave original waveform data to the concrete component to be measured is analyzed, detailed process includes:
It is every in the loaded mode of step (1) second to obtain a loading status by a load step, draw the concrete component to be measured
Original waveform figure under each loading status；Step (2) utilizes original wave of the concrete component to be measured under each loading status
Shape figure calculates scattered wave travel-time difference change rate, and draw out the scattered wave travel-time difference change rate dt/t of the concrete component to be measured with
Stress relation curve；
Step 5: by the scattered wave travel-time difference change rate dt/t of the concrete component to be measured and stress relation curve and the mark
The scattered wave travel-time difference change rate dt/t and stress relation curve comparison of quasi- concrete test block, find the concrete component to be measured
The scattered wave travel-time difference change rate dt/ of scattered wave travel-time difference change rate dt/t and stress relation curve in the standard concrete test block
Lap on t and stress relation curve, and with the corresponding stress value in the initial position of the lap for the coagulation to be measured
The absolute stress of native component.
Preferably, under the wave measurement uniaxial compression using ultrasonic scattering in the method for concrete absolute stress, institute
It states in the step (2) in step 2, detailed process are as follows:
1. step determines waveform starting point
Using the starting point of the original waveform of ultrasonic wave emission source as time reference, the time domain as receiving end original waveform is risen
Point；
2. step calculates travel-time difference change rate dt/t
The original waveform figure being plotted under each loading status is compared its similitude, the maximum phase of two waveforms two-by-two
Travel-time difference dt under relationship number, as required travel-time difference dt；
3. travel-time difference dt reliability judges step
The related coefficient of two sections of waveforms is if it is less than 0.75, then it is assumed that method failure, required dt result are unreliable number
According to；
Step 4. calculating and plotting scattered ultrasonic wave travel-time difference change rate dt/t and stress changing relation curve.
Waveform under two adjacent states is respectively h ' (t) and h (t).With the position h (t) normal condition, to the shape compared with it
State waveform h ' (t) is stretched or is compressed, and data analysis length can use 3000-7500 point and differ；To two groups of waveform h ' (t-
τ) and h (t) does cross-correlation, solves in cross-correlation function CCk(τ) corresponding τ value when maximum, wherein τ is that required travel-time difference becomes
Rate dt/t；
Preferably, under the wave measurement uniaxial compression using ultrasonic scattering in the method for concrete absolute stress, institute
State step 4. in, with certain state waveform h (t) be reference waveform, its adjacent states waveform h ' (t) is stretched or is collapsed into
Data analysis length is taken as 3000-7500 point by h ' (t- τ), carries out interpolation calculation, and the corresponding maximum τ of related coefficient is
Required travel-time difference change rate dt/t.
Preferably, under the wave measurement uniaxial compression using ultrasonic scattering in the method for concrete absolute stress, institute
It states in step 1, during test, ultrasonic excitation voltage is adjusted to receiving end and can receive the higher signal of signal-to-noise ratio to be advisable.
Preferably, under the wave measurement uniaxial compression using ultrasonic scattering in the method for concrete absolute stress, institute
It states in step 1, during test, ultrasonic excitation frequency is 20~500kHz.
Preferably, under the wave measurement uniaxial compression using ultrasonic scattering in the method for concrete absolute stress, institute
It states in step 1, during test, ultrasonic excitation frequency is 400kHz.
Preferably, under the wave measurement uniaxial compression using ultrasonic scattering in the method for concrete absolute stress, institute
It states in step 1, during test, transmitting terminal original waveform is the sine wave in 10 periods.
Preferably, under the wave measurement uniaxial compression using ultrasonic scattering in the method for concrete absolute stress, institute
It states in step 1, during test, sample frequency 5M/s.
Preferably, under the wave measurement uniaxial compression using ultrasonic scattering in the method for concrete absolute stress, institute
State in step 1, the first loaded mode are as follows: for the first time from 0 be pre-loaded to 50kN after unload, load step be taken as 5kN；Second
It is unloaded after being pre-loaded to 100kN, load step is taken as 10kN；It is unloaded after being loaded into the 80% of ultimate load for the third time, loads load
Step is 20kN, and unloading load step is 40kN.
The method of concrete absolute stress utilizes ultrasound under the wave measurement uniaxial compression of the present invention using ultrasonic scattering
Scattered wave measures the travel-time difference change rate and stress changing curve of standard concrete test block, then measures concrete component to be measured
Travel-time difference change rate and stress changing curve, standard concrete test block travel-time difference change rate and stress changing curve find with
The travel-time difference change rate and the most matched section of stress changing curve of concrete component to be measured, the start bit of the most matched section
Set the absolute stress for corresponding to concrete component to be measured.The present invention can absolutely answering with precise measurement concrete component to be measured
Power, and realize lossless, efficient detection to concrete component to be measured.
Detailed description of the invention
Fig. 1 is scattered ultrasonic wave test platform layout drawing of the present invention；
Fig. 2 is the receiving end original waveform under the conditions of different excitation voltages；
Fig. 3 is the receiving end original waveform under different stimulating frequencies；
Fig. 4 is receiving end original waveform under different cycle said conditions；
Fig. 5 is transmitting terminal original waveform (10 cycle)；
Fig. 6 is typical reception end original waveform；
Fig. 7 is three kinds of strength criterion concrete test blocks；
Fig. 8 (a) is sensor and foil gauge layout drawing in standard concrete test block；Fig. 8 (b) is that standard concrete test block is left
Side sensor and foil gauge layout drawing；Fig. 8 (c) is standard concrete test block right side sensor and foil gauge layout drawing；
Fig. 9 is the first loaded mode during test；
Figure 10 is flow chart of data processing figure；
Figure 11 is that scattered wave travel-time difference change rate of the standard concrete test block under multiple CYCLIC LOADING and stress variation are closed
It is curve；
Figure 12 is typical concrete stress-strain curves；
Figure 13 adds scattered wave travel-time difference change rate and stress changing relation song under unloading for standard concrete test block single
Line；
Figure 14 is the method for the present invention for measuring concrete absolute stress under uniaxial compression using scattered ultrasonic wave method
Flow chart；
Figure 15 is the comparable situation of standard concrete test block curve and concrete component curve to be measured.
Specific embodiment
Present invention will be described in further detail below with reference to the accompanying drawings, to enable those skilled in the art referring to specification text
Word can be implemented accordingly.
Such as Figure 14 to Figure 15, the present invention provides concrete under a kind of application ultrasonic scattering wave measurement uniaxial compression absolutely to answer
The method of power, comprising:
Step 1: one and the consistent standard concrete test block of concrete component to be measured are provided, under the first loaded mode
Scattered ultrasonic wave test is carried out to the standard concrete test block, the initial loading load of the first loaded mode is 0；
Step 2: the ultrasonic wave original waveform data to the standard concrete test block is analyzed, detailed process includes:
It is every in the loaded mode of step (1) first to walk to obtain a loading status by a load, it is plotted in the standard concrete test block
Original waveform figure under each loading status；Step (2) utilizes original wave of the standard concrete test block under each loading status
Shape figure calculates scattered wave travel-time difference change rate, and draws out the scattered wave travel-time difference change rate and stress of the standard concrete test block
Relation curve；
Step 3: carrying out scattered ultrasonic wave test to concrete component to be measured under the second loaded mode, this is second loaded
The initial loading load of mode is not 0, and the second loaded mode is contained in the first loaded mode；During the test,
Acquire the ultrasonic wave original waveform data of the concrete component to be measured；
Step 4: the ultrasonic wave original waveform data to the concrete component to be measured is analyzed, detailed process includes:
It is every in the loaded mode of step (1) second to obtain a loading status by a load step, draw the concrete component to be measured
Original waveform figure under each loading status；Step (2) utilizes original wave of the concrete component to be measured under each loading status
Shape figure calculates scattered wave travel-time difference change rate, and draw out the scattered wave travel-time difference change rate dt/t of the concrete component to be measured with
Stress relation curve；
Step 5: by the scattered wave travel-time difference change rate dt/t of the concrete component to be measured and stress relation curve and the mark
The scattered wave travel-time difference change rate dt/t and stress relation curve comparison of quasi- concrete test block, find the concrete component to be measured
The scattered wave travel-time difference change rate dt/ of scattered wave travel-time difference change rate dt/t and stress relation curve in the standard concrete test block
Lap on t and stress relation curve, and with the corresponding stress value in the initial position of the lap for the coagulation to be measured
The absolute stress of native component.
In a preferred embodiment, concrete absolute stress under the application ultrasonic scattering wave measurement uniaxial compression
Method in, in the step (2) in the step 2, detailed process are as follows:
1. step determines waveform starting point
Using the starting point of the original waveform of ultrasonic wave emission source as time reference, the time domain as receiving end original waveform is risen
Point；
2. step calculates travel-time difference change rate dt/t
The original waveform figure being plotted under each loading status is compared its similitude, the maximum phase of two waveforms two-by-two
Travel-time difference dt under relationship number, as required travel-time difference dt；
3. travel-time difference dt reliability judges step
The related coefficient of two sections of waveforms is if it is less than 0.75, then it is assumed that method failure, required dt result are unreliable number
According to；
Step 4. calculating and plotting scattered ultrasonic wave travel-time difference change rate dt/t and stress changing relation curve.
Waveform under two adjacent states is respectively h ' (t) and h (t).With the position h (t) normal condition, to the shape compared with it
State waveform h ' (t) is stretched or is compressed, and data analysis length can use 3000-7500 point and differ；To two groups of waveform h ' (t-
τ) and h (t) does cross-correlation, solves in cross-correlation function CCk(τ) corresponding τ value when maximum, wherein τ is that required travel-time difference becomes
Rate dt/t；
In a preferred embodiment, concrete absolute stress under the application ultrasonic scattering wave measurement uniaxial compression
Method in, the step 4. in, with certain state waveform h (t) be reference waveform, its adjacent states waveform h ' (t) is drawn
It stretches or is collapsed into h ' (t- τ), data analysis length is taken as 3000-7500 point, carry out interpolation calculation, corresponding related coefficient
Maximum τ is required travel-time difference change rate dt/t.
In a preferred embodiment, concrete absolute stress under the application ultrasonic scattering wave measurement uniaxial compression
Method in, in the step 1, during test, ultrasonic excitation voltage is adjusted to receiving end, and to receive noise relatively high
Signal be advisable.
In a preferred embodiment, concrete absolute stress under the application ultrasonic scattering wave measurement uniaxial compression
Method in, in the step 1, during test, ultrasonic excitation frequency be 20~500kHz.
In a preferred embodiment, concrete absolute stress under the application ultrasonic scattering wave measurement uniaxial compression
Method in, in the step 1, during test, ultrasonic excitation frequency be 400kHz.
In a preferred embodiment, concrete absolute stress under the application ultrasonic scattering wave measurement uniaxial compression
Method in, in the step 1, during test, transmitting terminal original waveform be 10 periods sine wave.
In a preferred embodiment, concrete absolute stress under the application ultrasonic scattering wave measurement uniaxial compression
Method in, in the step 1, during test, sample frequency 5M/s.
In a preferred embodiment, concrete absolute stress under the application ultrasonic scattering wave measurement uniaxial compression
Method in, in the step 1, the first loaded mode are as follows: for the first time from 0 be pre-loaded to 50kN after unload, load step be taken as
5kN；It is unloaded after being pre-loaded to 100kN for the second time, load step is taken as 10kN；It is unloaded after being loaded into the 80% of ultimate load for the third time
It carries, load load step is 20kN, and unloading load step is 40kN.
1, scattered ultrasonic wave test platform:
According to test requirements document, the scattered ultrasonic wave test platform of complete set is built, the layout of equipment is shown in Fig. 1.Test is flat
Platform includes the modules such as ultrasonic wave emission system, data receiving system, strain acquisition system, loading system and ultrasonic sensor.
2, the parameter configuration of scattered ultrasonic wave test
(1) ultrasonic device parameter setting
Before on-test, complete building for entire scattered ultrasonic wave test platform, connect modules, test data it is steady
It is qualitative, it after the completion of to be tested, then is tested, the accuracy of guarantee test data.It is dissipated for the ultrasound under the conditions of uniaxial loading
Ejected wave test, need to determine Multitest parameter, such as the stimulating frequency of ultrasonic wave, the data acquisition length of excitation voltage, oscillograph
With sample frequency etc..
A pair of probe is pasted at the centroid of two opposites of standard concrete test block, is respectively used to emit and receive letter
Number, stimulating frequency 400kHz, 3 kinds of voltages of excitation voltage point are excited (100V, 200V, 300V), the original wave of receiving end
Shape is shown in Fig. 2, compares the waveform diagram under three kinds of voltage shooting conditions, finds the original waveform noise under 300V voltage shooting condition
Than best, the amplitude of scattered wave part is larger.
Test discovery is under 300V voltage shooting condition, and original waveform signal-to-noise ratio is best, and the amplitude of scattered wave part is larger.
Since the research object of scattered ultrasonic wave is exactly the scattered wave that ultrasonic wave develops formation after concrete material, scattered wave amplitude
Larger, data are then more representative, in conditions permit, higher voltage taken to be excited.However, since excessively high swashs
Power generation pressure can damage sensor, the maximum voltage of sensors with auxiliary electrode no more than 350V, therefore select 300V for excitation voltage compared with
It is reasonable.
Selective exitation frequency is 200kHz, 300kHz, 400kHz respectively, and the original waveform of receiving end is shown in Fig. 3, comparison hair
It is existing, under 400kHz frequency shooting condition, scattered wave amplitude maximum, in the section time shaft [1.2ms, 1.8ms], scattered wave amplitude
It is larger, meet the requirement of scattered wave data analysis.Correlative study shows that for concrete material, the frequency of 20~500kHz has
Conducive to scattered wave development, the too low minor change for being unfavorable for finding concrete inner structure, excessively high frequency will lead to signal and decline
Subtract too big.In conclusion selective exitation frequency is 400kHz.
According to result above, 300V is set as excitation voltage, and 400kHz is stimulating frequency, carries out experimental test, cycle number
5,10,15,20 are selected respectively, and receiving end original waveform is shown in Fig. 4, and under 4 kinds of cycle said conditions, the amplitude of 4 waveforms is basic
It is identical, there is not notable difference.The limitation of empty ratio is carried in view of ultrasonic system, cycle number and repetition rate should not be too large, therefore set
Determining cycle number is 10, repetition rate 50Hz.Ultrasonic wave original waveform when Fig. 5 is 10 cycle, the waveform are 10
The sine wave in period, amplitude and period are all the same, illustrate that transmitting terminal ultrasonic frequency is pure, and wave source stability reaches test and wants
It asks.
After debugging, the sampling depth of oscillograph is set as 10000 points, sample frequency 5M/s, and each channel single is adopted
Integrate the time of data as 2ms.Thus the waveform acquired includes effective scattering wave component, meets scattered ultrasonic wave data processing and wants
It asks, sees Fig. 6.This time test sample frequency is taken as 5M/s, higher than 10 times or more of signal highest frequency, meets nyquist sampling
Law requirement.
(2) scattered ultrasonic wave is tested under the conditions of uniaxial loading
1. standard concrete test block makes
The ratio and dosage of standard concrete test block various composition are determined according to " design of common concrete proportioning regulation ",
Tri- kinds of strength criterion concrete test blocks of C30, C40, C50 are made respectively, and the ordinary portland cement used is 42.5 type；Flyash
It is I grade；Sand in 2nd area Sha Wei, fineness modulus 2.5~2.8；Rubble is 5~16mm continuous grading；It is mixed and stirred with tap water.Standard is mixed
Solidifying soil test block is size 150mm × 150mm × 300mm prism test block.Totally 18 (every kind of strength criterion concrete test blocks of quantity
6), and each test block is numbered, respectively 30- (1~6) #, 40- (1~6) #, 50- (1~6) #.Test block pours completion
Afterwards, standard curing is carried out in fog room, laboratory is deposited in after the completion of maintenance.
30- (1~3) #, 40- (1~3) #, 50- (1~3) # standard concrete test block is for super under the conditions of uniaxial loading
The test of sound scattering wave, such as Fig. 7；30-4#, 40-4#, 50-4# standard concrete test block are for determining three kinds of strength criterion concrete
The compressive ultimate strength of test block；30-5#, 40-5#, 50-5# standard concrete test block are used to test debugging work when early-stage preparations
Make, the setting that such as each system parameter and loading scheme load walk；Last group of standard concrete test block is used for complementary testing.2. marking
The sensor and foil gauge of quasi- concrete test block are arranged
6 foil gauges are arranged in each standard concrete test block altogether, are divided into two kinds of specifications, and length is respectively 10cm (vertical cloth
Set) and 5cm (lateral arrangement), number be that 1~6,1,2,4, No. 5 foil gauge is vertically arranged, for measuring vertical strain variation, 3,
No. 6 foil gauge lateral arrangements, for measuring transverse strain variation, in addition, setting temperature-compensating channel, is eliminated due to temperature change
The influence that strain sheet data is generated.Sensor arranges 4 altogether, and 1 transmitting, 3 receive, and emission sensor R1 is arranged in left side
Face centroid, receiving transducer R2 are arranged in right side centroid, and R1 and R3 are respectively arranged and R2 upper and lower, spacing 8cm.Specific arrangement
Figure is shown in Fig. 8 (a), Fig. 8 (b) and Fig. 8 (c).
3. scattered ultrasonic wave tests loading scheme
Before testing loading scheme formulation, chooses the test block of 30-4#, 40-4#, 50-4# standard concrete and carry out uniaxial loading examination
Test, press machine persistently loads, until standard concrete test block destroy, resulting ultimate load be respectively 1000kN, 1200kN and
1300kN.In test, 30- (1~3) #, 40- (1~3) #, 50- (1~3) # totally 9 standard concrete test blocks load step such as
Fig. 9 is first preloaded twice, is unloaded after being loaded into 50kN for the first time, and load step is taken as 5kN；After being loaded into 100kN for the second time
Unloading, load step are taken as 10kN；Third time is loaded into 800kN (about the 80% of ultimate load) and unloads afterwards, and load load step is
20kN, unloading load step is 40kN.Entire test process needs 100 load steps, about 2.5 hours of duration.
4. scattered ultrasonic wave tests implementation process
During test, it shall be noted that data acquisition need to be acquired after each load holds load 1 minute, because standard is mixed
Under different loading status, internal microstructure, which changes, needs the regular hour, finds in test 1 minute for solidifying soil test block
Time length comparison is suitable.In addition, need to ensure to acquire ultrasonic wave original waveform data and strain data in the same time, guarantee two kinds of numbers
According to stronger comparativity.
It according to above step, is tested at room temperature, three kinds of intensity (C30, C40, C50) standard concrete test blocks
3 repetitive tests are respectively carried out, 9 groups of ultrasonic wave initial data and 9 groups of strain datas is obtained, uniformly imported into computer and divided
Analysis.
5. data analysis process
Before application scattered ultrasonic wave method analysis data, need to the data of acquisition be classified and be numbered.Due in test
Load section be [0,800kN], range is larger, if original waveform h0 when using first zero loading status as reference waveform,
It is larger to calculate error.Therefore herein to the original waveform h of adjacent loading statuskAnd hk+1Cross-correlation is done, can guarantee calculated result
Accuracy, using the waveform of first loading status of adjacent loading status as reference waveform hk, k ∈ [1, n-1]；Second load
The waveform of state is hk+1, k ∈ [1, n-1]；K: loading status number, n: the maximum value of loading status number.Analysis method and mistake
Shown in journey is specific as follows, Figure 10 is flow chart of data processing figure.
From Figure 11 it can be found that scattered wave travel-time difference change rate (dt/t) is to the variation of strain (ε), there are stronger related
Property.Load is divided into preloading phase (0-50kN-0-100kN-0), load phase (0-800kN) and unloading phase by following analysis
(800kN-0) is discussed respectively.It is analyzed for convenience of data, the pass of scattered wave travel-time difference change rate curve and strain curve in figure
Key point and inflection point are indicated with letter A~G and a~g respectively.
(3) counter to push away absolute stress
1. by analyzing zero point of load application (A, C, E, G) in the entire load stage, it is found that numerical value A > C > E > G, explanation
Under three cyclic loads, the damage that inside concrete generates when peak load is 800kN is maximum, when peak load is 100kN
Damage is taken second place, minimum when peak load is 50kN, which meets the accumulative rule of damage of the concrete under CYCLIC LOADING.It is maximum
When load is bigger, the microcrack of generation is more, is distributed inside concrete structure more extensive, and load unloading is when being zero, microcrack
It is closed to varying degrees, but not healing completely, therefore the decline of scattered wave travel-time difference change rate is more.
2. counting payload values corresponding to 3 groups of standard concrete test blocks (totally 9) dt/t curve maximum, i.e. F* point respectively
Corresponding abscissa, is shown in Table 1.
Table 1F* point abscissa load Data-Statistics
3. dt/t with strain stress with pre-pressing stage variation tendency is consistent twice before load F change curve, but it is larger in load
When (be greater than 600kN), strain stress continuous linear increases, and turning point occurs near 600kN load in dt/t, and load increases, and
Dt/t numerical value then starts to reduce.The reason of causing this difference may is that strain data reaction normal concrete test block surface
Strain variation, and the variation of dt/t then reaction normal concrete test block internal microstructure.
4. in engineering, according to the stress-strain curves of concrete, such as Figure 12, being changed with actual measurement strain value by elasticity modulus
Calculation obtains the stress variation of practical concrete structure.In figure, o-a sections are straightways；A-b-c section concrete starts to show plasticity
Property, curve is bent downwardly.
There is relatively strong one-to-one relationship in the stress state by can see dt/t and standard concrete test block in Figure 11,
It theoretically can be by the value of the method measurement parameter dt/t of non-destructive testing, to ask concrete test block to be measured to survey the specific stress in area
Situation of change.Figure 13 adds scattered wave travel-time difference change rate and stress changing relation song under unloading for standard concrete test block single
Line.
As shown in Figure 14 and Figure 15, find same label first, with match, with intensity standard concrete test block dt/t with
Stress relation curve.If no, needing to take the standard concrete test block with concrete component striking resemblances to be measured, start from scratch
Load, makes a reference curve.Ensure that this curve includes component to be measured loading procedure experienced.Then to coagulation to be measured
Native component is continuously loaded and is unloaded, and is obtained a curve and (wherein, is carried out scattered ultrasonic wave test to concrete component to be measured
When, load initial load can be selected as the arbitrary value in addition to 0, such as 5kN or 10kN).Since we do not know to be measured mix
Stress of the solidifying soil component before load, so the absolute stress before load is unknown.But by below plus
The comparison of unloading curve and standard curve can must judge that concrete component to be measured adds correspondence of the curve of unloading on standard curve
Position, it is possible thereby to judge the stress state of the component to be measured before load.As shown in figure 15, it can be determined that the concrete to be measured
The absolute stress of component is about 13MPa.
Assuming that there is a component to be measured to need to know its internal stress is how many.Can to this concrete component to be measured into
Row continuous steps add unloading, obtain adding unloading curve, then go to compare on the curve to standard curve, find most matched
Section, the starting point of the section be both the absolute stress of component to be measured.
In test, pass through the scattered ultrasonic wave test under concrete in uniaxial loading environment, research scattering velocity of wave variation first
For rate with the variation tendency of stress, the variation tendency of 9 standard concrete test blocks is unanimous on the whole, it was demonstrated that the feasibility of this method.It is logical
The standard stress for establishing different labels concrete and scattering velocity of wave change curve are crossed, concrete structure to be measured can be obtained by comparison
The absolute stress of part.
Although the embodiments of the present invention have been disclosed as above, but its is not only in the description and the implementation listed
With it can be fully applied to various fields suitable for the present invention, for those skilled in the art, can be easily
Realize other modification, therefore without departing from the general concept defined in the claims and the equivalent scope, the present invention is simultaneously unlimited
In specific details and legend shown and described herein.
Claims (9)
1. a kind of method for measuring concrete absolute stress under uniaxial compression using scattered ultrasonic wave method characterized by comprising
Step 1: one and the consistent standard concrete test block of concrete component to be measured are provided, to this under the first loaded mode
Standard concrete test block carries out scattered ultrasonic wave test, and the initial loading load of the first loaded mode is 0；
Step 2: the ultrasonic wave original waveform data to the standard concrete test block is analyzed, detailed process includes: step
It is every in (1) first loaded mode to walk to obtain a loading status by a load, the standard concrete test block is plotted in each
Original waveform figure under loading status；Step (2) utilizes original waveform figure of the standard concrete test block under each loading status
Scattered wave travel-time difference change rate is calculated, and draws out the scattered wave travel-time difference change rate and stress relation of the standard concrete test block
Curve；
Step 3: carrying out scattered ultrasonic wave test, the second loaded mode to concrete component to be measured under the second loaded mode
Initial loading load be not 0, and the second loaded mode is contained in the first loaded mode；During the test, it acquires
The ultrasonic wave original waveform data of the concrete component to be measured；
Step 4: the ultrasonic wave original waveform data to the concrete component to be measured is analyzed, detailed process includes: step
It is every in (1) second loaded mode to obtain a loading status by a load step, the concrete component to be measured is drawn each
Original waveform figure under loading status；Step (2) utilizes original waveform figure of the concrete component to be measured under each loading status
Scattered wave travel-time difference change rate is calculated, and draws out the scattered wave travel-time difference change rate dt/t and stress of the concrete component to be measured
Relation curve；
Step 5: the scattered wave travel-time difference change rate dt/t of the concrete component to be measured is mixed with stress relation curve and the standard
The scattered wave travel-time difference change rate dt/t and stress relation curve comparison of solidifying soil test block, find the scattering of the concrete component to be measured
Wave travel-time difference change rate dt/t and stress relation curve the standard concrete test block scattered wave travel-time difference change rate dt/t with
Lap on stress relation curve, and with the corresponding stress value in the initial position of the lap for the concrete structure to be measured
The absolute stress of part.
2. the method for measuring concrete absolute stress under uniaxial compression using scattered ultrasonic wave method as described in claim 1,
It is characterized in that, in the step (2) in the step 2, detailed process are as follows:
1. step determines waveform starting point
Time domain starting point using the starting point of the original waveform of ultrasonic wave emission source as time reference, as receiving end original waveform；
2. step calculates travel-time difference change rate dt/t
The original waveform figure being plotted under each loading status is compared its similitude, the maximal correlation system of two waveforms two-by-two
Travel-time difference dt under several, as required travel-time difference dt；
3. travel-time difference dt reliability judges step
The related coefficient of two sections of waveforms is if it is less than 0.75, then it is assumed that method failure, required dt result are corrupt data；
Step 4. calculating and plotting scattered ultrasonic wave travel-time difference change rate dt/t and stress changing relation curve；
Waveform under two adjacent states is respectively h ' (t) and h (t)；With the position h (t) normal condition, to the state wave compared with it
Shape h ' (t) is stretched or is compressed, and data analysis length can use 3000-7500 point and differ；To two groups of waveform h ' (t- τ) and
H (t) does cross-correlation, solves in cross-correlation function CCk(τ) corresponding τ value when maximum, wherein τ is required scattered wave travel-time difference
Change rate dt/t；
3. the method for measuring concrete absolute stress under uniaxial compression using scattered ultrasonic wave method as claimed in claim 2,
Be characterized in that, the step 4. in, with certain state waveform h (t) be reference waveform, its adjacent states waveform h ' (t) is drawn
It stretches or is collapsed into h ' (t- τ), data analysis length is taken as 3000-7500 point, carry out interpolation calculation, corresponding related coefficient
Maximum τ is required travel-time difference change rate dt/t.
4. absolutely being answered using concrete under scattered ultrasonic wave method measurement uniaxial compression as claimed any one in claims 1 to 3
The method of power, which is characterized in that in the step 1, during test, ultrasonic excitation voltage, which is adjusted to receiving end, to be received
It is advisable to the higher signal of signal-to-noise ratio.
5. the method for measuring concrete absolute stress under uniaxial compression using scattered ultrasonic wave method as claimed in claim 3,
It is characterized in that, in the step 1, during test, ultrasonic excitation frequency is 20~500kHz.
6. the method for measuring concrete absolute stress under uniaxial compression using scattered ultrasonic wave method as claimed in claim 4,
It is characterized in that, in the step 1, during test, ultrasonic excitation frequency is 400kHz.
7. the method for measuring concrete absolute stress under uniaxial compression using scattered ultrasonic wave method as claimed in claim 5,
It is characterized in that, in the step 1, during test, transmitting terminal original waveform is the sine wave in 10 periods.
8. the method for measuring concrete absolute stress under uniaxial compression using scattered ultrasonic wave method as claimed in claim 6,
It is characterized in that, in the step 1, during test, sample frequency 5M/s.
9. the method for measuring concrete absolute stress under uniaxial compression using scattered ultrasonic wave method as described in claim 1,
Be characterized in that, in the step 1, the first loaded mode are as follows: for the first time from 0 be pre-loaded to 50kN after unload, load step be taken as
5kN；It is unloaded after being pre-loaded to 100kN for the second time, load step is taken as 10kN；It is unloaded after being loaded into the 80% of ultimate load for the third time
It carries, load load step is 20kN, and unloading load step is 40kN.
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