CN104990656A - Method for nondestructive evaluation of residual stress of aluminum alloy pre-stretched plate by utilizing ultrasonic wave - Google Patents
Method for nondestructive evaluation of residual stress of aluminum alloy pre-stretched plate by utilizing ultrasonic wave Download PDFInfo
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- CN104990656A CN104990656A CN201510336346.3A CN201510336346A CN104990656A CN 104990656 A CN104990656 A CN 104990656A CN 201510336346 A CN201510336346 A CN 201510336346A CN 104990656 A CN104990656 A CN 104990656A
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Abstract
The invention provides a method for nondestructive evaluation of a residual stress of an aluminum alloy pre-stretched plate by utilizing an ultrasonic wave. The method comprises the following steps: selecting an ultrasonic wave characteristic frequency, and then obtaining a characteristic attenuation coefficient under the characteristic frequency; obtaining a surface roughness compensation coefficient, determining a grain size compensation coefficient of a detected aluminum alloy pre-stretched plate, determining a loosening compensation coefficient value of the aluminum alloy pre-stretched plate, determining a constant, related to a material characteristic, of the detected aluminum alloy pre-stretched plate, and then obtaining a residual stress value equation; selecting an ultrasonic wave probe; performing calibration on a residual stress test block, and performing correction on a system gain compensation; performing ultrasonic wave scanning on the to-be-detected plate; and generating a residual stress field map. Through adoption of the technical scheme, an influence of surface roughness is reduced, an obtained quantitative value of the residual stress is more accurate, the method has a large thickness application scope, and interferences of plate loosening and plate grain size factors on residual stress detection precision are reduced.
Description
Technical field
The invention belongs to field of non destructive testing, particularly relate to a kind of method of ultrasound wave nondestructive evaluation aluminum alloy pretensioning plate unrelieved stress.
Background technology
Modern Aviation manufacturing industry is to the future development that aircraft large-scale integral parts manufacture.There is a large amount of unrelieved stresss in aluminum alloy plate materials and will cause serious consequence.The solution hardening technique of 2XXX system, 7XXX line aluminium alloy is the main cause importing unrelieved stress.But in order to obtain more excellent combination property after Ageing Treatment, the solution hardening operation of 2XXX system, 7XXX line aluminium alloy is but absolutely necessary.Aluminum alloy pretensioning plate manufacturer often uses large-tonnage prestretched machine to stretch to the aluminum alloy plate materials after solution hardening, thus the stress in sheet material is redistributed.In order to judge the effect of stretching process to aluminium alloy plate stress reduction, aircraft industry in the urgent need to a kind of fast, low cost, characterize the lossless detection method of sheet material unrelieved stress intuitively.
At present, the lossless detection methods such as physico-chemical method and ray diffraction method such as boring method, porous variance method, Crack Compliance Method are applied to the residual stress measurement of material more maturely, also have increasing researcher to disclose the unrelieved stress using ultrasonic method to measure material.As patent 98806517.7 discloses a kind of method using ultrasonic measurement test button unrelieved stress, the ultrasonic incident wave of incident gating time computation and measurement of the method in selection and the incident convolution integral value of the periodic wave of a basic frequency.But the method does not use unrelieved stress, and calibration block is demarcated, therefore only can generate residual stress distribution collection of illustrative plates, but can not carry out quantitatively to residual-stress value; In addition, the method does not consider the impact that rolled plate loosens and sheet material grain size detects unrelieved stress.
Patent 201310533626.4 also discloses a kind of aluminum alloy pretensioning plate unrelieved stress water logging ultrasonic method.Mode that the method uses a transmitting of popping one's head in, another probe receives detects.But the accuracy of detection of the method affects comparatively large by surface irregularity, the unrelieved stress being only applicable to thin sheet surface detects; In addition, the unrelieved stress test block that the method uses utilizes the method for interference fit to import unrelieved stress to unrelieved stress test block, and the sheet material of each batch needs preparation unrelieved stress test block like this, and this process need at substantial fund and time, cost is very high.
Summary of the invention
For above technical matters, the invention provides a kind of method of ultrasound wave nondestructive evaluation aluminum alloy pretensioning plate unrelieved stress, reduce the impact of surface irregularity, make the quantitative values of the unrelieved stress obtained more accurate, and there is the larger thickness scope of application, and reduce sheet material loosen and sheet material grain size factor to the interference of unrelieved stress accuracy of detection.
To this, the present invention adopts technical scheme to be: a kind of method of ultrasound wave nondestructive evaluation aluminum alloy pretensioning plate unrelieved stress, comprises the following steps:
Step S1: select ultrasound wave characteristic frequency A, obtain the characteristic decay factor alpha of described characteristic frequency A ultrasound wave round trip in tested aluminum alloy pretensioning plate
a; Described characteristic frequency A value is not less than 10MHz, is not more than 40MHz;
Step S2: be residual-stress value by characteristic decay coefficient conversion; Concrete grammar is: obtain surface irregularity penalty coefficient η by ultrasonic method; Obtained the grain size of tested aluminum alloy pretensioning plate by metallographic examination, determine the grain size penalty coefficient μ of tested aluminum alloy pretensioning plate; To be loosened penalty coefficient ξ value by total rolling reduction ratio determination aluminum alloy pretensioning plate of process; By with the comparison of XRD ray diffraction method, determine the constant a relevant with material behavior and constant b; Then according to the characteristic decay factor alpha that step S1 obtains
a, obtain residual-stress value equation S=exp (the b α of tested aluminum alloy pretensioning plate
a+ a) × η × μ × ξ;
Step S3: select ultrasonic probe;
Step S4: calibrate in unrelieved stress test block;
Step S5: according to the unrelieved stress numerical value of step S4 calibrate in unrelieved stress test block, compensates system-gain and corrects; Described system-gain compensates and refers in a calibration process, and when finding that test block actual measured value and test block nominal value are not inconsistent, adjustment distance wave amplitude calibration curve, makes the deviation of final test block actual measured value and test block nominal value in the range of uncertainty allowed;
Step S6: ultrasonic scanning is carried out to tested aluminum alloy pretensioning plate;
Step S7: generate residual stress field collection of illustrative plates.
The order of step S1 ~ step S3 can be exchanged, and step S1 and step S2 can carry out after step S6 completes.Preferably, first perform step S3, step S4, step S6 (preserving the scan-data of detected sheet material during completing steps S6), then scan-data is carried out to the data processing of step S1 and step S2, then perform step S7 and generate residual stress field collection of illustrative plates.This scheme is also applicable to the detection of the unrelieved stress of other sheet metals simultaneously.
In such scheme, be that the database that the operational equation of residual-stress value can use actual experiment to set up substitutes by characteristic decay coefficient conversion, namely the mode of actual experiment is adopted to obtain data, the characteristic decay coefficient of aluminum alloy pretensioning plate and unrelieved stress numerical value one_to_one corresponding are got up, form complete database, in testing process, database is utilized to complete the conversion of characteristic decay coefficient and residual-stress value.
This technical scheme adopts the data acquisition modes of characteristic frequency uniquely, and calculates characteristic decay coefficient by these data, improves the sensitivity that unrelieved stress detects.
Preferred further, the method for described ultrasound wave nondestructive evaluation aluminum alloy pretensioning plate unrelieved stress is applied to the unrelieved stress assessment of aluminum alloy pretensioning plate.
As a further improvement on the present invention, be that residual-stress value adopts following methods by described characteristic decay coefficient conversion: obtain surface irregularity penalty coefficient η by ultrasonic method; Obtained the grain size of tested aluminum alloy pretensioning plate by metallographic examination, determine the grain size penalty coefficient μ of tested aluminum alloy pretensioning plate; To be loosened penalty coefficient ξ value by total rolling reduction ratio determination aluminum alloy pretensioning plate of process; By with the comparison of XRD ray diffraction method, determine constant a and the constant b of tested aluminum alloy pretensioning plate, described constant a is relevant with the material behavior of tested aluminum alloy pretensioning plate with constant b, and the constant a that often kind of alloy designations is corresponding with alloy state is different with constant b, needs actual measurement and determines.Then according to the characteristic decay factor alpha that step S1 obtains
a, obtain residual-stress value equation S=exp (the b α of tested aluminum alloy pretensioning plate
a+ a) × η × μ × ξ.
The ultrasonic attenuation of characteristic frequency A is mainly relevant with the intensive defect (such as loosening) that unrelieved stress, grain size, material itself exist and surperficial unevenness etc.Technical scheme of the present invention, in order to obtain the numerical value of unrelieved stress exactly, is considered surface irregularity, grain size, the loose interference detected the unrelieved stress of tested sheet material simultaneously, the impact that disturbing factor causes is got rid of in residual-stress value equation.And introduce the loose and sheet material grain size penalty coefficient of sheet material, reduce sheet material loosen and sheet material grain size factor to the interference of unrelieved stress accuracy of detection.
Comprehensive, the creationary mode by building database of technical scheme of the present invention, surface irregularity, grain size, loose influence factor are brought in the calculating formula of unrelieved stress, decreases interference, improve precision and the accuracy of unrelieved stress detection.
As a further improvement on the present invention, the acquisition methods of described surface irregularity penalty coefficient η is: be placed on by tracking gate in detected material upper surface echoed signal, in the scanning process to detected material, obtain plate surface unevenness data, thus calculate surface irregularity penalty coefficient η.
As a further improvement on the present invention, aluminum alloy pretensioning plate penalty coefficient ξ value of loosening is determined by total rolling reduction ratio, and total rolling reduction ratio is more than or equal to 80%, and ξ is 1.0; Total rolling reduction ratio is 60% ~ 80%, ξ is 0.1 ~ 1.0.
Further preferred, described aluminum alloy pretensioning plate penalty coefficient ξ value of loosening comprehensively is determined by the first rolling pass drafts and total rolling reduction ratio.When the first rolling pass drafts reaches more than 20mm, when total rolling reduction ratio is more than or equal to 70%, ξ is 1.0.
As a further improvement on the present invention, the grain size of described tested aluminum alloy pretensioning plate adopts and intercepts sample respectively at the head of tested aluminum alloy pretensioning plate and afterbody and carry out metallographic examination acquisition.
As a further improvement on the present invention, the grain size of described tested aluminum alloy pretensioning plate adopts ultrasonic method to detect tested aluminum alloy pretensioning plate and obtain.
As a further improvement on the present invention, the obtaining step of described characteristic decay coefficient is: in 10MHz ~ 40MHz, select characteristic frequency A, ultrasonic scanning is carried out to tested aluminum alloy pretensioning plate, obtains the first time upper surface wave-wave width H of described characteristic frequency A ultrasound wave to tested aluminum alloy pretensioning plate
1with wave-wave width H at the bottom of first time
2, and the detected sheet metal thickness T of test, then according to
calculate characteristic decay factor alpha
a.
Existing measurement attenuation coefficient method directly measures upper surface echo wave amplitude and the first Bottom echo wave amplitude for the first time, thus calculate all-wave attenuation coefficient.But, the ultrasonic frequency of launching due to ultrasonic probe is except the centre frequency of nominal value, also launch the ultrasound wave of other frequencies, due to the ultrasound wave of various frequency and the interaction complexity of sheet material interior tissue, the data source using all-wave attenuation coefficient to detect as unrelieved stress will bring larger interference.Bring error in order to reduce other frequency ultrasonic waves as far as possible to residual stress measurement, the present invention only uses the ultrasound wave of certain characteristic frequency to measure unrelieved stress, selects a specifically value, be called characteristic frequency A in 10MHz ~ 40MHz.A definite value between the preferred 15MHz ~ 25MHz of described characteristic frequency A, is more preferably 20MHz.Use characteristic frequency A upper surface wave-wave of hyperacoustic first time width and end first time wave-wave width to calculate the characteristic decay coefficient of characteristic frequency ultrasound wave round trip in detected material, thus improve the sensitivity of unrelieved stress detection.
As a further improvement on the present invention, the contact normal probe of described ultrasonic probe to be frequency be 10MHz ~ 40MHz or immersion type ultrasonic probe or phased-array ultrasonic probe.For characterizing the better frequency range of unrelieved stress, ultrasonic frequency range is preferably 15MHz ~ 25MHz.
As a further improvement on the present invention, when the thickness of described sheet material to be measured is 6 ~ 12mm, adopt immersion type focusing probe; When the thickness of described sheet material to be measured is greater than 12mm, adopt immersion type flat probe or immersion type phased-array ultrasonic probe; When needing to carry instrument to Site Detection, adopt contact normal probe.Adopt this technical scheme, the residual-stress value obtained is more accurate.
As a further improvement on the present invention, described unrelieved stress test block intercepts from the aluminum alloy pre-stretching plate that unrelieved stress is 0 ~ 60MPa.
As a further improvement on the present invention, described unrelieved stress test block intercepts from the aluminum alloy pre-stretching plate that unrelieved stress is 0 ~ 20MPa.
The unrelieved stress test block that technique scheme uses is nearly unstressed test block, this test block due to the residual-stress value of self very low, so materials behavior is more stable, the problem such as creep, stress relaxation, stress corrosion that high residual stress test block faces is less likely to occur, the unrelieved stress calibration value measured is more stable, make the quantitatively more accurate of ultrasonic investigation unrelieved stress, reduce cost simultaneously.
As a further improvement on the present invention, the thickness of described unrelieved stress test block is 6mm ~ 250mm, and the width of described unrelieved stress test block is 100mm ~ 1000mm, and length is 100mm ~ 1000mm.
As a further improvement on the present invention, described unrelieved stress test block is for intercept from 7050-T7451 aluminum alloy pre-stretching plate, and thickness is 76mm, and width is 200mm, and length is 200mm.
As a further improvement on the present invention, the residual-stress value of described unrelieved stress test block adopts XRD method to measure; Use XRD method to measure the unrelieved stress numerical value of once described unrelieved stress test block at least every year, and re-start demarcation.Preferred further, require that customization residual stress level is qualified critical unrelieved stress test block according to Customer Standard, be called the test block of judgement unrelieved stress.If the residual stress level of detected aluminum alloy pretensioning plate is higher than the test block of judgement unrelieved stress in testing process, be judged to defective; If the residual stress level of detected aluminum alloy pretensioning plate is lower than the test block of judgement unrelieved stress in testing process, it is qualified to be judged to.
As a further improvement on the present invention, described step S6, when ultrasonic scanning is carried out to board under test material, ultrasound wave water distance is 50mm ~ 120mm, low-pass filtering is 25 ~ 50MHz, and high-pass filtering is set to 5 ~ 15MHz, and scan method adopts step-by-step movement 100% to scan, ultrasonic wave acoustic beam covers more than 10%, and sweep velocity is less than 300mm/s.Pulse repetition rate is set according to detected sheet metal thickness, need ensures not produce phantom ripple in testing process.
As a further improvement on the present invention, when carrying out ultrasonic scanning, the temperature as the water of couplant is 7 DEG C ~ 37 DEG C, and in whole ultrasonic scanning testing process, the temperature fluctuation of water is less than ± and 2 DEG C.Just measure the temperature as the water of couplant when starting to detect, guarantee that this temperature is in 7 DEG C ~ 37 DEG C scopes.Adopt this technical scheme, avoid temperature fluctuation to reduce the precision of unrelieved stress detection.
As a further improvement on the present invention, in the collection of illustrative plates of described residual stress field, adopt warm colour point to represent the large point of unrelieved stress numerical value, use cool colour point to represent the little point of unrelieved stress numerical value, and the scale of the corresponding unrelieved stress numerical value of subsidiary respective color.Adopt this technical scheme, represent the numerical value of unrelieved stress at each coordinate of aluminum alloy pretensioning plate more intuitively.
Compared with prior art, beneficial effect of the present invention is:
The first, technical scheme of the present invention obtains the unevenness data of monoblock sheet material in testing process, and uses these unevenness data to carry out the compensation of unrelieved stress testing result, thus reduces surface irregularity to the impact of the unrelieved stress precision recorded;
The second, technical scheme of the present invention adopts the straight acoustic beam technology of pulse to carry out ultrasonic scanning to board under test material, and its restriction by sheet metal thickness is very little, greatly reduces the influence factor of sheet metal thickness, has the larger thickness scope of application;
3rd, technical scheme of the present invention adopts the data acquisition modes of characteristic frequency uniquely, and calculates characteristic decay coefficient by these data, improves the sensitivity that unrelieved stress detects;
4th, introduce sheet material and loosen and sheet material grain size penalty coefficient, reduce sheet material and loosen with sheet material grain size factor to the interference of unrelieved stress accuracy of detection;
5th, technical scheme of the present invention considers surface irregularity, grain size, the loose interference detected the unrelieved stress of tested sheet material simultaneously, the creationary mode by building database, surface irregularity, grain size, loose influence factor are brought in the calculating formula of unrelieved stress, improves precision and the accuracy of unrelieved stress detection; Assessment for unrelieved stress provides a kind of design newly;
6th, the unrelieved stress test block that technical scheme of the present invention uses is nearly unstressed test block, this test block due to the residual-stress value of self very low, so materials behavior is more stable, the problem such as creep, stress relaxation, stress corrosion that high residual stress test block faces is less likely to occur, the unrelieved stress calibration value measured is more stable, makes the quantitatively more accurate of ultrasonic investigation unrelieved stress, reduces cost simultaneously.
Accompanying drawing explanation
Fig. 1 is sheet material is imported unrelieved stress by the embodiment of the present invention 1 schematic diagram by manual method;
Fig. 2 is the unrelieved stress collection of illustrative plates that the embodiment of the present invention 1 generates;
Fig. 3 is the unrelieved stress 3D view that the embodiment of the present invention 1 generates;
The spectrogram frequency of Fig. 4 to be the embodiment of the present invention 2 medium frequency be ultrasonic probe of 15MHz;
Fig. 5 is the residual stress field collection of illustrative plates that the embodiment of the present invention 2 generates;
Fig. 6 is the residual stress field 3D view that the embodiment of the present invention 2 generates.
Mark in figure: 1-7075 sheet material; 2-support; 3-cold water; 4-water pipe.
Embodiment
Below in conjunction with accompanying drawing, preferably embodiment of the present invention is described in further detail.
Embodiment 1
Detected sheet material is 7075 aluminum alloy plate materials, and specification is thickness 20mm, width 200mm, length 300mm.Unrelieved stress test block intercepts from 7075 aluminum alloy pre-stretching plates, and specification is thickness 20mm, width 150mm, length 150mm.Adopt XRD Diffraction to measure described unrelieved stress test block, the residual-stress value recording described unrelieved stress test block is 20MPa, and fixed at the enterprising rower of unrelieved stress test block.
Detected sheet material imports unrelieved stress by manual method, as shown in Figure 1, is placed in heating furnace by this 7075 sheet material 1 and is warming up to 475 DEG C, be incubated 4 hours.Then 7075 sheet materials 1 are transferred to rapidly on unsettled support 2.The water pipe 4 of a band nozzle is fixed at the center of support 2.Cold water 3 is injected into the surface of 7075 sheet materials 1 by water pipe 4, makes 7075 sheet materials 1 be quickly cooled to room temperature with uneven cooling velocity.Due to 7075 sheet materials 1 only a point be subject to quick cooling, cause 7075 sheet materials 1 leave higher unrelieved stress.
Use the method for the invention to carry out analysis of Residual Stress to 7075 sheet materials that described single-point quenches, concrete operation step is as follows:
(1) operation program of characteristic decay coefficient is set up:
The detected sheet metal thickness of test, obtains detected sheet metal thickness T; Sync gate and upper surface ripple gate are placed on detected sheet material first time upper surface echo.Bottom surface ripple gate is placed on first time Bottom echo.Signals collecting is set to only frequency acquisition is the ultrasonic signal of 20MHz simultaneously.Characteristic frequency 20MHz is selected and recording feature wave amplitude H in the Fourier space of first time upper surface echo
1; In the Fourier space of first time Bottom echo, select characteristic frequency 20MHz and recording feature wave amplitude H simultaneously
2.By H
1and H
2substitute into equation
calculate characteristic decay coefficient.Wherein, T is detected sheet metal thickness; α
20MHzit is characteristic decay coefficient.
(2) operation program that characteristic decay coefficient conversion is residual-stress value is set up:
Surface irregularity penalty coefficient η is obtained by ultrasonic method.Embodiment is placed on by tracking gate in detected sheet material upper surface echoed signal.Plate surface unevenness data can be obtained in aluminum alloy pretensioning plate scanning process and generate C scintigram, being gone out the surface irregularity penalty coefficient η of each coordinate points by the transit time numerical evaluation on C scintigram;
Carry out metallographic examination being intercepted sample respectively by the head of aluminum alloy pretensioning plate and afterbody, grain size is one-level, thus determines grain size penalty coefficient μ;
Detected sheet material in the hot rolling the first rolling pass drafts is 20mm, and total rolling reduction ratio is 80%.These 2 data are used to determine loose penalty coefficient ξ value;
For 7075 aluminum alloy plate materials, its constant a and constant b is respectively 32.02 and 1.24, by a, b, α of obtaining
20MHz, η, μ and ξ value substitutes into residual-stress value equation S=exp (b α
a+ a) in × η × μ × ξ, obtain unrelieved stress equation.
(3) be 15MHz by frequency, diameter is that the immersion type ultrasound wave flat probe of 12.7mm is installed on ultrasonic equipment.
(4) calibrate in unrelieved stress test block.Unrelieved stress displayed value is 15MPa.
(5) the adjustment System gain compensation nominal value 20MPa that makes unrelieved stress displayed value equal in unrelieved stress test block.
(6) detected sheet material is carried out to the ultrasonic scanning of 100% covering, ultrasound wave water distance is 70mm; Low-pass filtering is set to 40MHz, and high-pass filtering is set to 5MHz, and scanning stepping is 2mm, thus ensures to scan sheet material 100%; Pulse repetition rate is set to 500Hz, and sweep velocity is 100mm/s, is 25 ± 2 DEG C as the temperature of the water of couplant in testing process.
(7) residual stress field collection of illustrative plates is generated:
By the A sweep data of the entire plate that step (6) obtains, namely the all-wave scan-data obtained imports exclusive data process software, this exclusive data process software comprises step (1) and step (2) described operation program, obtain the residual stress field collection of illustrative plates of detected sheet material as shown in Figure 2, the 3D view of residual stress field is as Fig. 3.
Embodiment 2
Detected sheet material is 7050-T7451 aluminum alloy plate materials, and detected 7050-T7451 aluminum alloy plate materials employing extensibility is the drawing stress abatement operation of 2.5%, and specification is thickness 76mm, width 260mm, length 260mm.Unrelieved stress test block intercepts from 7050-T7451 aluminum alloy plate materials, and specification is thickness 76mm, width 200mm, length 200mm.The residual-stress value adopting XRD Diffraction to record unrelieved stress test block is 18MPa, and fixed at the enterprising rower of unrelieved stress test block.Carry out residual stress measurement to detected sheet material, step is as follows:
(1) be 15MHz by frequency, diameter is that the immersion type ultrasound wave flat probe of 12.7mm is installed on ultrasonic equipment, described frequency be the spectrogram of the ultrasonic probe of 15MHz as shown in Figure 4.
(2) calibrate in unrelieved stress test block.Unrelieved stress displayed value is 22MPa.
(3) the adjustment System gain compensation nominal value 18MPa that makes unrelieved stress displayed value equal in unrelieved stress test block.
(4) detected sheet material is carried out to the ultrasonic scanning of 100% covering.Ultrasonic system data acquiring and recording pattern is set to record A sweep.Also can be understood as ultrasonic system to be set in scanning process, record all-wave scan-data, to use special software to process these data after the end of scan.Ultrasound wave water is apart from being 75mm, and low-pass filtering is set to 35MHz, and high-pass filtering is set to 5MHz; Scanning stepping is 2mm, thus ensures to scan sheet material 100%; Pulse repetition rate is set to 400Hz; Sweep velocity is 80mm/s; It is 25 ± 2 DEG C as the temperature of the water of couplant in testing process.
(5) operation program of characteristic decay coefficient is set up.The detected sheet metal thickness of test, obtains detected sheet metal thickness T.Then sync gate and upper surface ripple gate are placed on detected sheet material first time upper surface echo, bottom surface ripple gate are placed on first time Bottom echo.Signals collecting is set to only frequency acquisition is the ultrasonic signal of 15MHz simultaneously.Characteristic frequency 15MHz is selected and recording feature wave amplitude H in the Fourier space of first time upper surface echo
1; In the Fourier space of first time Bottom echo, select characteristic frequency 15MHz and recording feature wave amplitude H simultaneously
2.By H
1and H
2substitute into equation
calculate characteristic decay coefficient.Wherein, T is detected sheet metal thickness; α
15MHzit is characteristic decay coefficient.
(6) operation program that characteristic decay coefficient conversion is residual-stress value is set up:
Surface irregularity penalty coefficient η is obtained by ultrasonic method.Embodiment is placed on by tracking gate in detected sheet material upper surface echoed signal.Plate surface unevenness data can be obtained in aluminum alloy pretensioning plate scanning process and generate C scintigram, being gone out the surface irregularity penalty coefficient η of each coordinate points by the transit time numerical evaluation on C scintigram;
Carry out metallographic examination being intercepted sample respectively by the head of aluminum alloy pretensioning plate and afterbody, grain size is one-level, thus determines grain size penalty coefficient μ;
Detected sheet material in the hot rolling the first rolling pass drafts is 15mm, and total rolling reduction ratio is 75%.These 2 data are used to determine loose penalty coefficient ξ value;
For 7050-T7451 aluminum alloy plate materials, wherein constant a and constant b is respectively 29.23 and 1.32, by a, b, α of obtaining
20MHz, η, μ and ξ value substitutes into residual-stress value equation by characteristic decay factor alpha
15MHzvalue substitute into residual-stress value equation S=exp (b α
a+ a) × η × μ × ξ.
(7) residual stress field collection of illustrative plates is generated:
By the A sweep data of the entire plate that step (4) obtains, the all-wave scan-data being about to obtain imports exclusive data process software.This exclusive data process software comprises step (5) and step (6) described operation program.Perform step (7) and obtain the residual stress field collection of illustrative plates of detected sheet material as shown in Figure 5, the 3D view of residual stress field as shown in Figure 6.
Above content is in conjunction with concrete preferred implementation further description made for the present invention, can not assert that specific embodiment of the invention is confined to these explanations.For general technical staff of the technical field of the invention, without departing from the inventive concept of the premise, some simple deduction or replace can also be made, all should be considered as belonging to protection scope of the present invention.
Claims (10)
1. a method for ultrasound wave nondestructive evaluation aluminum alloy pretensioning plate unrelieved stress, is characterized in that, comprise the following steps:
Step S1: select ultrasound wave characteristic frequency A, obtain the characteristic decay factor alpha of described characteristic frequency A ultrasound wave round trip in tested aluminum alloy pretensioning plate
a; Wherein, described characteristic frequency A value is not less than 10MHz, is not more than 40MHz;
Step S2: be residual-stress value by characteristic decay coefficient conversion, concrete grammar is: obtain surface irregularity penalty coefficient η by ultrasonic method; Obtained the grain size of tested aluminum alloy pretensioning plate by metallographic examination, determine the grain size penalty coefficient μ of tested aluminum alloy pretensioning plate; To be loosened penalty coefficient ξ value by total rolling reduction ratio determination aluminum alloy pretensioning plate of process; Determine the constant a relevant with tested aluminum alloy pre-stretching plate material characteristic and constant b; Then according to the characteristic decay factor alpha that step S1 obtains
a, obtain residual-stress value equation S=exp (the b α of tested aluminum alloy pretensioning plate
a+ a) × η × μ × ξ;
Step S3: select ultrasonic probe;
Step S4: calibrate in unrelieved stress test block;
Step S5: according to the unrelieved stress numerical value of step S4 calibrate in unrelieved stress test block, and system-gain compensation is corrected;
Step S6: ultrasonic scanning is carried out to tested aluminum alloy pretensioning plate;
Step S7: generate residual stress field collection of illustrative plates.
2. the method for ultrasound wave nondestructive evaluation aluminum alloy pretensioning plate unrelieved stress according to claim 1, it is characterized in that, the acquisition methods of described surface irregularity penalty coefficient η is: be placed on by tracking gate in detected material upper surface echoed signal, in the scanning process to detected material, obtain plate surface unevenness data, thus calculate surface irregularity penalty coefficient η; Described aluminum alloy pretensioning plate penalty coefficient ξ value of loosening determines by total rolling reduction ratio, and total rolling reduction ratio is more than or equal to 80%, and ξ is 1.0; Total rolling reduction ratio is 60% ~ 80%, ξ is 0.1 ~ 1.0.
3. the method for ultrasound wave nondestructive evaluation aluminum alloy pretensioning plate unrelieved stress according to claim 1, is characterized in that: the grain size of described tested aluminum alloy pretensioning plate adopts and intercepts sample respectively at the head of tested aluminum alloy pretensioning plate and afterbody and carry out metallographic examination acquisition; The grain size of described tested aluminum alloy pretensioning plate adopts ultrasonic method to detect tested aluminum alloy pretensioning plate and obtains.
4. the method for ultrasound wave nondestructive evaluation aluminum alloy pretensioning plate unrelieved stress according to claim 1, it is characterized in that: the obtaining step of described characteristic decay coefficient is: in 10MHz ~ 40MHz, select characteristic frequency A, ultrasonic scanning is carried out to tested aluminum alloy pretensioning plate, obtains the first time upper surface wave-wave width H of described characteristic frequency A ultrasound wave to tested aluminum alloy pretensioning plate
1with wave-wave width H at the bottom of first time
2, and the detected sheet metal thickness T of test, then according to
calculate characteristic decay factor alpha
a.
5. the method for ultrasound wave nondestructive evaluation aluminum alloy pretensioning plate unrelieved stress according to claim 1, is characterized in that: the contact normal probe of described ultrasonic probe to be frequency be 10MHz ~ 30MHz or immersion type ultrasonic probe or phased-array ultrasonic probe; When the thickness of described sheet material to be measured is 6 ~ 12mm, adopt immersion type focusing probe; When the thickness of described sheet material to be measured is greater than 12mm, adopt immersion type flat probe or immersion type phased-array ultrasonic probe; When needing to carry instrument to Site Detection, adopt contact normal probe.
6. the method for the ultrasound wave nondestructive evaluation aluminum alloy pretensioning plate unrelieved stress according to Claims 1 to 5 any one, is characterized in that: the aluminum alloy pre-stretching plate that described unrelieved stress test block is 0 ~ 60MPa from unrelieved stress intercepts.
7. the method for ultrasound wave nondestructive evaluation aluminum alloy pretensioning plate unrelieved stress according to claim 6, is characterized in that: the aluminum alloy pre-stretching plate that described unrelieved stress test block is 0 ~ 20MPa from unrelieved stress intercepts.
8. the method for ultrasound wave nondestructive evaluation aluminum alloy pretensioning plate unrelieved stress according to claim 6, it is characterized in that: the thickness of described unrelieved stress test block is 6mm ~ 250mm, the width of described unrelieved stress test block is 100mm ~ 1000mm, and length is 100mm ~ 1000mm; The residual-stress value of described unrelieved stress test block adopts XRD method to measure; Use XRD method to measure the unrelieved stress numerical value of once described unrelieved stress test block at least every year, and re-start demarcation.
9. the method for the ultrasound wave nondestructive evaluation aluminum alloy pretensioning plate unrelieved stress according to Claims 1 to 5 any one, it is characterized in that: described step S6, immersion type ultrasonic scanning is carried out to board under test material, ultrasound wave water distance is 50mm ~ 120mm, low-pass filtering is 25 ~ 50MHz, and high-pass filtering is set to 5 ~ 15MHz, and scan method adopts step-by-step movement 100% to scan, ultrasonic wave acoustic beam covers more than 10%, and sweep velocity is less than 300mm/s.
10. the method for ultrasound wave nondestructive evaluation aluminum alloy pretensioning plate unrelieved stress according to claim 9, it is characterized in that: when carrying out ultrasonic scanning, temperature as the water of couplant is 7 DEG C ~ 37 DEG C, and in whole ultrasonic scanning testing process, the temperature fluctuation of water is less than ± and 2 DEG C.
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| CN111207884A (en) * | 2020-01-17 | 2020-05-29 | 西北工业大学 | Design and manufacturing method of standard sample of residual stress deflection method calibration device |
| CN111504530A (en) * | 2020-04-02 | 2020-08-07 | 江苏科技大学 | Method for rapidly realizing regulation and control of stress of cladding layer without damage based on ultrasonic technology |
| CN112207522A (en) * | 2020-10-26 | 2021-01-12 | 许晨玲 | Flatness control method for large aluminum alloy integral wall plate |
| CN112880895A (en) * | 2019-11-29 | 2021-06-01 | 哈尔滨工业大学 | Nonlinear ultrasonic wave-based large-scale high-speed rotation equipment blade residual stress measurement method |
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| CN111207884A (en) * | 2020-01-17 | 2020-05-29 | 西北工业大学 | Design and manufacturing method of standard sample of residual stress deflection method calibration device |
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| CN111504530A (en) * | 2020-04-02 | 2020-08-07 | 江苏科技大学 | Method for rapidly realizing regulation and control of stress of cladding layer without damage based on ultrasonic technology |
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