CN101799454A - Electromagnetic ultrasonic flaw detecting method for eliminating electromagnetic ultrasonic Lamb wave multi-mode influence - Google Patents
Electromagnetic ultrasonic flaw detecting method for eliminating electromagnetic ultrasonic Lamb wave multi-mode influence Download PDFInfo
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Abstract
The invention discloses an electromagnetic ultrasonic flaw detecting method for eliminating an electromagnetic ultrasonic Lamb wave multi-mode influence, relates to the technical field of ultrasonic detection, and solves the problem that echo signals are complex and cannot be detected caused by the multi-mode characteristic of electromagnetic ultrasonic Lamb waves in the process of realizing non-contact ultrasonic nondestructive detection by adopting the electromagnetic ultrasonic detection method at present. The method comprises the following steps: determining the distance fluctuation range of coil windings of an electromagnetic ultrasonic transducer and a bandwidth range of excitation current frequency introduced in the coil windings according to the property and the thickness of the material of a piece to be detected, so that a probe of the electromagnetic ultrasonic transducer excites single-mode electromagnetic ultrasonic Lamb waves or excites multi-mode electromagnetic ultrasonic Lamb waves with the same propagation speed in the piece to be tested; and starting detecting, acquiring a detection result signal and processing data so as to obtain the position and the size of a flaw in the piece to be detected. The method provides a foundation for the wide application of electromagnetic ultrasonic detection.
Description
Technical field
The present invention relates to the ultrasonic detection technology field, be specifically related to eliminate the electromagnetic ultrasonic flaw detecting method of electromagnetic ultrasonic Lamb wave multi-mode influence.
Background technology
Lamb ripple propagation distance is far away, detection efficiency is high, is widely used a kind of guided wave form in the Ultrasonic NDT.The electromagnetic acoustic detection technique is comparatively popular a kind of non-contact type Ultrasonic NDT mode, need not acoustic couplant, need not the test specimen surface preparation, therefore the electromagnetic ultrasonic Lamb wave that is inspired by the electromagnetic acoustic technology has special advantage, to large tracts of land, long distance or buried underground, there is the detection of the metal plate-like of clad and tubular test coupon particularly suitable, and can be used for special occasions such as high temperature and high speed, on May 1st, 1991, disclosed publication number was to have mentioned the use electromagnetic ultrasonic Lamb in " automatic defect detection technology using electromagnetic ultrasonic " patent of CN1051086A to carry out steel plate and detect, and the detection advantage and the implementation method of this inspection technique have been set forth, yet the Lamb ripple has the multi-mode characteristic, and this specific character can be brought negative effect to Ultrasonic Detection.If the Lamb ripple of a plurality of patterns is propagated in test specimen simultaneously, make the echoed signal that receives complicated chaotic; If simultaneously occur the defect reflection signal again, waveform will more mixed and disorderly, cause the defective discrimination difficulty higher and cause to detect and fail.For the adverse effect of multi-mode in Non-Destructive Testing of electromagnetic ultrasonic Lamb wave, a kind of effective removing method is not proposed clearly also both at home and abroad at present.
Summary of the invention
Adopting the electromagnetic acoustic detection method to realize in the process of non-contact type Ultrasonic NDT in order to solve at present, because the problem that the multi-mode characteristic of electromagnetic ultrasonic Lamb wave causes the echoed signal complexity, can't detect the invention provides the electromagnetic ultrasonic flaw detecting method of eliminating electromagnetic ultrasonic Lamb wave multi-mode influence.
The present invention is an electromagnetic ultrasonic flaw detecting method of eliminating electromagnetic ultrasonic Lamb wave multi-mode influence, its detailed process is: at first according to the material properties and the thickness of the test specimen to be measured in the electromagnet ultrasonic changer, spacing L and the fluctuation range thereof of determining the tortuous coil of electromagnet ultrasonic changer is [L-Δ L, L+ Δ L] and described tortuous coil in pass to excitation current frequency f and bandwidth range [f-Δ f thereof, f+ Δ f], make the probe of described electromagnet ultrasonic changer in test specimen to be measured, inspire the electromagnetic ultrasonic Lamb wave of single-mode or inspire the electromagnetic ultrasonic Lamb wave of various modes with same propagation speed, then, begin to detect, adopt the probe of an electromagnet ultrasonic changer to send detection signal to test specimen to be measured, and the probe by described electromagnet ultrasonic changer receives the testing result signal of described detection signal behind test specimen inner counter folding to be measured, according to described testing result signal is carried out data processing, obtain the defective locations and the size of test specimen to be measured inside.
Magnetic ultrasonic flaw detecting method of the present invention, be on the basis of existing magnetic ultrasonic flaw detecting method, before detection, material behavior and thickness according to the test specimen to be measured in the electromagnet ultrasonic changer obtain the running parameter of ultrasonic probe, and then adopt existing magnetic ultrasonic flaw detecting method to carry out carrying out flaw detection.
Beneficial effect of the present invention is: the present invention excites equation to make electromagnet ultrasonic changer be operated in rational working point and perform region on the electromagnetic ultrasonic Lamb wave excitation curve according to electromagnetic ultrasonic Lamb wave, and the concrete grammar of electromagnetic ultrasonic Lamb wave by only inspiring single-mode or the electromagnetic ultrasonic Lamb wave by inspiring the various modes with same propagation speed effectively eliminated electromagnetic ultrasonic Lamb wave multi-mode influence, improved the detection performance of electromagnetic ultrasonic Lamb wave.
Method of the present invention is applicable to existing various magnetic ultrasonic flaw detecting method.
Description of drawings
Fig. 1 is the structural representation that excites the electromagnet ultrasonic changer of electromagnetic ultrasonic Lamb wave of the present invention, Fig. 2 is the electromagnetic ultrasonic Lamb wave excitation curve synoptic diagram when test specimen 1 to be measured is for steel plate in the embodiment two, Fig. 3 is the electromagnetic ultrasonic Lamb wave excitation curve synoptic diagram when test specimen 1 to be measured is for steel plate in the embodiment three, and Fig. 4 is the electromagnetic ultrasonic Lamb wave group velocity L '-c when test specimen 1 to be measured is for steel plate in the embodiment three
gCurve synoptic diagram, Fig. 5 are the electromagnetic ultrasonic Lamb wave group velocity f '-c when test specimen 1 to be measured is for steel plate in the embodiment three
gCurve synoptic diagram, Fig. 6 are working point 5 (0.30,7.20) and perform region 6 (Δ L among Fig. 2 in the embodiment two
1', Δ f
1') the measured waveform synoptic diagram, wherein, U1 represents to excite working point 5 and perform region 6 master of place shock waves under the electromagnetic ultrasonic Lamb wave single-mode, A1 represents to excite the test specimen to be measured 1 one end face echoes of electromagnet ultrasonic changer under the electromagnetic ultrasonic Lamb wave single-mode, B1 represents to excite the other end echo of the test specimen to be measured 1 of electromagnet ultrasonic changer under the single-mode, Fig. 7 is working point 7 (0.19,8.00) and perform region 8 (Δ L among Fig. 3 in the embodiment three
2', Δ f
2') the measured waveform synoptic diagram, wherein, U2 represents to excite working point 7 and perform region 8 master of place shock waves under the electromagnetic ultrasonic Lamb wave multi-mode, A2 represents to excite the test specimen to be measured 1 one end face echoes of electromagnet ultrasonic changer under the electromagnetic ultrasonic Lamb wave multi-mode, and B2 represents to excite the other end echo of the test specimen to be measured 1 of electromagnet ultrasonic changer under the electromagnetic ultrasonic Lamb wave multi-mode.
Embodiment
Embodiment one: the electromagnetic ultrasonic flaw detecting method of the described elimination electromagnetic ultrasonic Lamb wave multi-mode influence of present embodiment, its detailed process is: at first according to the material properties and the thickness of the test specimen to be measured 1 in the electromagnet ultrasonic changer, spacing L and the fluctuation range thereof of determining the tortuous coil 2 of electromagnet ultrasonic changer is [L-Δ L, L+ Δ L] and described tortuous coil 2 in pass to excitation current frequency f and bandwidth range [f-Δ f thereof, f+ Δ f], make the probe of described electromagnet ultrasonic changer in test specimen 1 to be measured, inspire the electromagnetic ultrasonic Lamb wave of single-mode or inspire the electromagnetic ultrasonic Lamb wave of various modes with same propagation speed, then, begin to detect, adopt the probe of an electromagnet ultrasonic changer to send detection signal to test specimen 1 to be measured, and receive the testing result signal of described detection signal behind test specimen 1 inner reflexed to be measured by described electromagnet ultrasonic changer, according to described testing result signal is carried out data processing, obtain the defective locations and the size of test specimen to be measured 1 inside.
Testing process in the present embodiment can be finished detection with reference to the process of regulation among the GJB GJB3384-1998 " sheet metal Lamb wave test method ".
Embodiment two: present embodiment is further specifying embodiment one, material properties and thickness described in the embodiment one according to the test specimen to be measured 1 in the electromagnet ultrasonic changer, spacing L and the fluctuation range thereof of determining the tortuous coil 2 of electromagnet ultrasonic changer is [L-Δ L, L+ Δ L] and described tortuous coil 2 in pass to excitation current frequency f and bandwidth range [f-Δ f thereof, f+ Δ f], the method that makes the probe of described electromagnet ultrasonic changer inspire the electromagnetic ultrasonic Lamb wave of single-mode in test specimen 1 to be measured is:
Step 1: obtain the material properties of the test specimen to be measured 1 in the electromagnet ultrasonic changer, described material properties comprises thickness, transverse wave speed and longitudinal wave velocity, excites equation according to described material properties and electromagnetic ultrasonic Lamb wave
Wherein, c
sThe expression transverse wave speed, c
lThe expression longitudinal wave velocity, the tortuous coil 2 spacing L of L ' expression electromagnet ultrasonic changer and the ratio of test specimen to be measured 1 thickness d, be apart from thickness rate L '=L/d, excitation current 4 frequency f of f ' expression electromagnet ultrasonic changer and the product of test specimen to be measured 1 thickness d are thick long-pending f '=f * d frequently;
Step 2: determine the electromagnetic ultrasonic Lamb wave single-mode that in test specimen 1 to be measured, will excite;
Step 3: the working point (L that on the electromagnetic ultrasonic Lamb wave excitation curve of test specimen 1 to be measured, selects the electromagnetic ultrasonic Lamb wave single-mode
1', f
1'), L wherein
1' when being illustrated in the electromagnetic ultrasonic Lamb wave single-mode apart from thickness rate, f
1' frequency when being illustrated in electromagnetic ultrasonic Lamb wave and exciting single-mode is thick long-pending;
Step 4: the coil parameter and the excitation current parameter of design electromagnet ultrasonic changer make electromagnet ultrasonic changer be operated in working point (L
1', f
1') on, determine perform region (the Δ L of described electromagnet ultrasonic changer on the electromagnetic ultrasonic Lamb wave excitation curve of test specimen 1 to be measured simultaneously
1', Δ f
1') in, wherein, described perform region (Δ L
1', Δ f
1') on the electromagnetic ultrasonic Lamb wave excitation curve of test specimen 1 to be measured be one with working point (L
1', f
1') be center, the long Δ L of being
1'=2 * Δ L/d, wide be Δ f
1The rectangle frame of '=2 * Δ fd, Δ L are represented the fluctuation range of tortuous coil 2 spacing L, and Δ f represents the fluctuation range of excitation current 4 frequency f;
Step 5: with determined perform region (Δ L
1', Δ f
1') correspond on the electromagnetic ultrasonic Lamb wave excitation curve of test specimen 1 to be measured, obtain perform region (Δ L
1', Δ f
1') position on the electromagnetic ultrasonic Lamb wave excitation curve of test specimen 1 to be measured, if at described perform region (Δ L
1', Δ f
1') in, only there is the electromagnetic ultrasonic Lamb wave of the single-mode described in the step 2, then execution in step seven, otherwise execution in step six;
Step 6: return step 3, on the electromagnetic ultrasonic Lamb wave excitation curve of test specimen 1 to be measured, select the working point (L of the single excitation mode of electromagnetic ultrasonic Lamb wave again
1', f
1');
Step 7: the spacing L and the fluctuation range thereof that obtain the tortuous coil 2 of ultrasonic transducer are to pass to excitation current frequency f and bandwidth range [f-Δ f, f+ Δ f], wherein L=L in [L-Δ L, L+ Δ L] and the described tortuous coil 2
1', Δ L=Δ L
1', f=f
1', Δ f=Δ f
1'.
In the present embodiment, step 7 has finally been finished the design of electromagnet ultrasonic changer, has reached the purpose of eliminating electromagnetic ultrasonic Lamb wave multi-mode influence.
In the present embodiment, perform region (Δ L
1', Δ f
1') define with the spacing L fluctuation range of tortuous coil 2, the frequency f fluctuation range of excitation current 4 and the thickness d of test specimen to be measured 1.
In the present embodiment, the index on equation the right that excites equation of electromagnetic ultrasonic Lamb wave is for representing symmetric pattern (S pattern) at+1 o'clock, index is-1 o'clock title mode (A pattern) that makes difficulties, electromagnetic ultrasonic Lamb wave has or not several modes in theory, and symmetric pattern is expressed as S0, S1, S2 ... antisymmetric mode is expressed as A0, A1, A2 ...
In the present embodiment, exciting and receiving by electromagnet ultrasonic changer of electromagnetic ultrasonic Lamb wave finished, described electromagnet ultrasonic changer comprises test specimen 1 to be measured, tortuous coil 2 and magnet 3, described tortuous coil 2 and magnet 3 are as probe, described tortuous coil 2 is between magnet 3 and test specimen to be measured 1, and guarantee that described test specimen to be measured 1 and tortuous coil 2 are in the magnetic field range of magnet 3, the probe placement of electromagnet ultrasonic changer is between two end faces that test specimen 1 detection side to be measured makes progress during detection, make lifting between described probe and the test specimen to be measured 1 simultaneously apart from the smaller the better, generally be close to test specimen to be measured 1 surface, distance is 0 under the perfect condition.
Carry out instance analysis at present embodiment:
In step 1, when test specimen 1 to be measured is steel plate, excite equation to draw the electromagnetic ultrasonic Lamb wave excitation curve of test specimen 1 to be measured according to electromagnetic ultrasonic Lamb, as shown in Figure 2.
In step 3, on curve shown in Figure 2, select the working point 5 (0.30,7.20) of the determined electromagnetic ultrasonic Lamb wave single-mode that will excite of step 2, described working point 5 (0.30,7.20) is positioned on the curve of S1 pattern.
In step 4, the perform region of electromagnet ultrasonic changer on Fig. 2 curve is as perform region 6 (Δ L
1', Δ f
1'), working point 5 (0.30,7.20) and perform region 6 (Δ L
1', Δ f
1') measured waveform as shown in Figure 6;
In step 5, determined perform region 6 (Δ L
1', Δ f
1') correspond on Fig. 2 curve, confirm the position of perform region on excitation curve, if perform region 6 (Δ L
1', Δ f
1') in have only selected S1 pattern, then eliminate electromagnetic ultrasonic Lamb wave multi-mode influence success; If perform region 6 (Δ L
1', Δ f
1') in still have the pattern of other electromagnetic ultrasonic Lamb waves, then do not reach the purpose of eliminating multi-mode influence, need carry out next step and reselect the working point.
Embodiment three: present embodiment is further specifying embodiment one, material properties and thickness described in the embodiment one according to the test specimen to be measured 1 in the electromagnet ultrasonic changer, the fluctuation range of spacing L of determining the tortuous coil 2 of electromagnet ultrasonic changer is [L-Δ L, L+ Δ L] and described tortuous coil 2 in pass to bandwidth range [the f-Δ f of excitation current frequency f, f+ Δ f], the method that makes the probe of described electromagnet ultrasonic changer inspire the electromagnetic ultrasonic Lamb wave of the various modes with same propagation speed in test specimen 1 to be measured is:
Steps A: obtain the material properties of the test specimen to be measured 1 in the electromagnet ultrasonic changer, described material properties comprises thickness, transverse wave speed and longitudinal wave velocity, according to described material properties, electromagnetic ultrasonic Lamb wave group velocity equation
Excite equation with electromagnetic ultrasonic Lamb wave
, the electromagnetic ultrasonic Lamb wave group velocity equation and the electromagnetic ultrasonic Lamb wave of finding the solution test specimen 1 to be measured excite equation, and draw the electromagnetic ultrasonic Lamb wave group velocity curve and the electromagnetic ultrasonic Lamb wave excitation curve of test specimen 1 to be measured;
Step B:, on the excitation curve of the electromagnetic ultrasonic Lamb wave of test specimen 1 to be measured, select working point (L according to the coil parameter and the excitation current parameter of electromagnet ultrasonic changer
2', f
2') and perform region (Δ L
2', Δ f
2'), make described electromagnet ultrasonic changer be operated in working point (L
2', f
2') on, make described perform region (Δ L simultaneously
2', Δ f
2') on the excitation curve of the electromagnetic ultrasonic Lamb wave of test specimen 1 to be measured, cover at least two kinds of electromagnetic ultrasonic Lamb wave patterns;
Step C: with working point (L
2', f
2') correspond on the electromagnetic ultrasonic Lamb wave group velocity curve of test specimen 1 to be measured, obtain described working point (L
2', f
2') corresponding point on the electromagnetic ultrasonic Lamb wave group velocity curve of test specimen 1 to be measured, and with perform region (Δ L
2', Δ f
2') correspond on the electromagnetic ultrasonic Lamb wave group velocity curve of test specimen 1 to be measured, obtain described perform region (Δ L
2', Δ f
2') corresponding line segment on the electromagnetic ultrasonic Lamb wave group velocity curve of test specimen 1 to be measured;
Step D: obtain corresponding point and the position of corresponding line segment on the electromagnetic ultrasonic Lamb wave group velocity curve of test specimen 1 to be measured, if perform region (Δ L
2', Δ f
2') each pattern of the electromagnetic ultrasonic Lamb wave that covered overlaps mutually with corresponding corresponding line segment or close, the group velocity error between perhaps described each pattern corresponding point is no more than 3%, execution in step F then, otherwise execution in step E;
Step e: return step B,, on the excitation curve of the electromagnetic ultrasonic Lamb wave of test specimen 1 to be measured, select working point (L again according to electromagnet ultrasonic changer
2', f
2') and perform region (Δ L
2', Δ f
2');
Step F: the spacing L and the fluctuation range thereof that obtain the tortuous coil 2 of ultrasonic transducer are to pass to excitation current frequency f and bandwidth range [f-Δ f, f+ Δ f], wherein L=L in [L-Δ L, L+ Δ L] and the described tortuous coil 2
2', Δ L=Δ L
2', f=f
2', Δ f=Δ f
2'.
In the present embodiment, the group velocity of electromagnetic ultrasonic Lamb wave is represented the velocity of propagation of electromagnetic ultrasonic Lamb wave in test specimen 1 to be measured.
At present embodiment, carry out instance analysis:
In steps A, the electromagnetic ultrasonic Lamb wave group velocity curve of the test specimen of being drawn to be measured 1 comprises electromagnetic ultrasonic Lamb wave group velocity L '-c shown in Figure 4
gCurve and electromagnetic ultrasonic Lamb wave group velocity f '-c shown in Figure 5
gCurve, the electromagnetic ultrasonic Lamb wave excitation curve of test specimen 1 to be measured as shown in Figure 3, test specimen 1 to be measured is a steel plate.
In step B, on the excitation curve of the electromagnetic ultrasonic Lamb wave of test specimen to be measured 1 shown in Figure 3, select working point 7 (0.19,8.00) and perform region 8 (Δ L
2', Δ f
2'), described perform region 8 (Δ L
2', Δ f
2') on excitation curve shown in Figure 3, covered S0 pattern and A0 pattern, described working point 7 (0.19,8.00) and perform region 8 (Δ L
2', Δ f
2') measured waveform as shown in Figure 7.
In step C, with working point 7 (0.19,8.00) and perform region 8 (Δ L
2', Δ f
2') correspond to the electromagnetic ultrasonic Lamb wave group velocity L '-c of test specimen to be measured 1 as shown in Figure 4
gOn the curve, obtain corresponding point 11 (two points of S0 and A0) and corresponding line segment 12 (two line segments of S0 and A0), and with working point 7 (0.19,8.00) and perform region 8 (Δ L
2', Δ f
2') correspond to the electromagnetic ultrasonic Lamb wave group velocity f '-c of test specimen to be measured 1 as shown in Figure 5
gOn the curve, obtain corresponding point 13 (two points of S0 and A0) and corresponding line segment 14 (two line segments of S0 and A0).
Claims (3)
1. eliminate the electromagnetic ultrasonic flaw detecting method of electromagnetic ultrasonic Lamb wave multi-mode influence, the detailed process that it is characterized in that it is: at first according to the material properties and the thickness of the test specimen to be measured (1) in the electromagnet ultrasonic changer, spacing L and the fluctuation range thereof of determining the tortuous coil (2) of electromagnet ultrasonic changer is [L-Δ L, L+ Δ L] and described tortuous coil (2) in pass to excitation current frequency f and bandwidth range [f-Δ f thereof, f+ Δ f], make the probe of described electromagnet ultrasonic changer in test specimen to be measured (1), inspire the electromagnetic ultrasonic Lamb wave of single-mode or inspire the electromagnetic ultrasonic Lamb wave of various modes with same propagation speed, then, begin to detect, adopt the probe of an electromagnet ultrasonic changer to send detection signal to test specimen to be measured (1), and receive the testing result signal of described detection signal behind the inner reflexed of test specimen to be measured (1) by the probe of described electromagnet ultrasonic changer, according to described testing result signal is carried out data processing, obtain test specimen to be measured (1) inner defective locations and size.
2. the electromagnetic ultrasonic flaw detecting method of elimination electromagnetic ultrasonic Lamb wave multi-mode influence according to claim 1, it is characterized in that material properties and thickness according to the test specimen to be measured (1) in the electromagnet ultrasonic changer, spacing L and the fluctuation range thereof of determining the tortuous coil (2) of electromagnet ultrasonic changer is [L-Δ L, L+ Δ L] and described tortuous coil (2) in pass to excitation current frequency f and bandwidth range [f-Δ f thereof, f+ Δ f], the method that makes the probe of described electromagnet ultrasonic changer inspire the electromagnetic ultrasonic Lamb wave of single-mode in test specimen to be measured (1) is:
Step 1: obtain the material properties of the test specimen to be measured (1) in the electromagnet ultrasonic changer, described material properties comprises thickness, transverse wave speed and longitudinal wave velocity, excites equation according to described material properties and electromagnetic ultrasonic Lamb wave
Wherein, c
sThe expression transverse wave speed, c
lThe expression longitudinal wave velocity, the ratio of tortuous coil (2) the spacing L of L ' expression electromagnet ultrasonic changer and test specimen to be measured (1) thickness d, be apart from thickness rate L '=L/d, the product of excitation current (4) frequency f of f ' expression electromagnet ultrasonic changer and test specimen to be measured (1) thickness d is thick long-pending f '=f * d frequently;
Step 2: determine the electromagnetic ultrasonic Lamb wave single-mode that in test specimen to be measured (1), will excite;
Step 3: the working point (L that on the electromagnetic ultrasonic Lamb wave excitation curve of test specimen to be measured (1), selects the electromagnetic ultrasonic Lamb wave single-mode
1', f
1'), L wherein
1' when being illustrated in the electromagnetic ultrasonic Lamb wave single-mode apart from thickness rate, f
1' frequency when being illustrated in electromagnetic ultrasonic Lamb wave and exciting single-mode is thick long-pending;
Step 4: the coil parameter and the excitation current parameter of design electromagnet ultrasonic changer make electromagnet ultrasonic changer be operated in working point (L
1', f
1') on, determine perform region (the Δ L of described electromagnet ultrasonic changer on the electromagnetic ultrasonic Lamb wave excitation curve of test specimen to be measured (1) simultaneously
1', Δ f
1') in, wherein, described perform region (Δ L
1', Δ f
1') on the electromagnetic ultrasonic Lamb wave excitation curve of test specimen to be measured (1) be one with working point (L
1', f
1') be center, the long Δ L of being
1'=2 * Δ L/d, wide be Δ f
1The rectangle frame of '=2 * Δ fd, Δ L are represented the fluctuation range of tortuous coil (2) spacing L, and Δ f represents the fluctuation range of excitation current (4) frequency f;
Step 5: with determined perform region (Δ L
1', Δ f
1') correspond on the electromagnetic ultrasonic Lamb wave excitation curve of test specimen to be measured (1), obtain perform region (Δ L
1', Δ f
1') position on the electromagnetic ultrasonic Lamb wave excitation curve of test specimen to be measured (1), if at described perform region (Δ L
1', Δ f
1') in, only there is the electromagnetic ultrasonic Lamb wave of the single-mode described in the step 2, then execution in step seven, otherwise execution in step six;
Step 6: return step 3, on the electromagnetic ultrasonic Lamb wave excitation curve of test specimen to be measured (1), select the working point (L of the single excitation mode of electromagnetic ultrasonic Lamb wave again
1', f
1');
Step 7: the spacing L and the fluctuation range thereof that obtain the tortuous coil (2) of ultrasonic transducer are to pass to excitation current frequency f and bandwidth range [f-Δ f, f+ Δ f], wherein L=L in [L-Δ L, L+ Δ L] and the described tortuous coil (2)
1', Δ L=Δ L
1', f=f
1', Δ f=Δ f
1'.
3. the electromagnetic ultrasonic flaw detecting method of elimination electromagnetic ultrasonic Lamb wave multi-mode influence according to claim 1, it is characterized in that material properties and thickness according to the test specimen to be measured (1) in the electromagnet ultrasonic changer, the fluctuation range of spacing L of determining the tortuous coil (2) of electromagnet ultrasonic changer is [L-Δ L, L+ Δ L] and described tortuous coil (2) in pass to bandwidth range [the f-Δ f of excitation current frequency f, f+ Δ f], the method that makes the probe of described electromagnet ultrasonic changer inspire the electromagnetic ultrasonic Lamb wave of the various modes with same propagation speed in test specimen to be measured (1) is:
Steps A: obtain the material properties of the test specimen to be measured (1) in the electromagnet ultrasonic changer, described material properties comprises thickness, transverse wave speed and longitudinal wave velocity, according to described material properties, electromagnetic ultrasonic Lamb wave group velocity equation
Excite equation with electromagnetic ultrasonic Lamb wave
Step B:, on the excitation curve of the electromagnetic ultrasonic Lamb wave of test specimen to be measured (1), select working point (L according to the coil parameter and the excitation current parameter of electromagnet ultrasonic changer
2', f
2') and perform region (Δ L
2', Δ f
2'), make described electromagnet ultrasonic changer be operated in working point (L
2', f
2') on, make described perform region (Δ L simultaneously
2', Δ f
2') on the excitation curve of the electromagnetic ultrasonic Lamb wave of test specimen to be measured (1), cover at least two kinds of electromagnetic ultrasonic Lamb wave patterns;
Step C: with working point (L
2', f
2') correspond on the electromagnetic ultrasonic Lamb wave group velocity curve of test specimen to be measured (1), obtain described working point (L
2', f
2') corresponding point on the electromagnetic ultrasonic Lamb wave group velocity curve of test specimen to be measured (1), and with perform region (Δ L
2', Δ f
2') correspond on the electromagnetic ultrasonic Lamb wave group velocity curve of test specimen to be measured (1), obtain described perform region (Δ L
2', Δ f
2') corresponding line segment on the electromagnetic ultrasonic Lamb wave group velocity curve of test specimen to be measured (1);
Step D: obtain corresponding point and the position of corresponding line segment on the electromagnetic ultrasonic Lamb wave group velocity curve of test specimen to be measured (1), if perform region (Δ L
2', Δ f
2') each pattern of the electromagnetic ultrasonic Lamb wave that covered overlaps mutually with corresponding corresponding line segment or close, the group velocity error between perhaps described each pattern corresponding point is no more than 3%, execution in step F then, otherwise execution in step E;
Step e: return step B,, on the excitation curve of the electromagnetic ultrasonic Lamb wave of test specimen to be measured (1), select working point (L again according to electromagnet ultrasonic changer
2', f
2') and perform region (Δ L
2', Δ f
2');
Step F: the spacing L and the fluctuation range thereof that obtain the tortuous coil (2) of ultrasonic transducer are to pass to excitation current frequency f and bandwidth range [f-Δ f, f+ Δ f], wherein L=L in [L-Δ L, L+ Δ L] and the described tortuous coil (2)
2', Δ L=Δ L
2', f=f
2', Δ f=Δ f
2'.
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| CN103308609A (en) * | 2013-06-26 | 2013-09-18 | 哈尔滨工业大学 | Lamb wave mode control method based on electromagnetic ultrasonic emission transducer |
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