CN111157628A - Electromagnetic ultrasonic excitation device for depth stress detection - Google Patents
Electromagnetic ultrasonic excitation device for depth stress detection Download PDFInfo
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- CN111157628A CN111157628A CN202010075726.7A CN202010075726A CN111157628A CN 111157628 A CN111157628 A CN 111157628A CN 202010075726 A CN202010075726 A CN 202010075726A CN 111157628 A CN111157628 A CN 111157628A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/04—Analysing solids
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L1/00—Measuring force or stress, in general
- G01L1/25—Measuring force or stress, in general using wave or particle radiation, e.g. X-rays, microwaves, neutrons
- G01L1/255—Measuring force or stress, in general using wave or particle radiation, e.g. X-rays, microwaves, neutrons using acoustic waves, or acoustic emission
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
- G01L5/00—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes
- G01L5/0047—Apparatus for, or methods of, measuring force, work, mechanical power, or torque, specially adapted for specific purposes measuring forces due to residual stresses
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/04—Analysing solids
- G01N29/07—Analysing solids by measuring propagation velocity or propagation time of acoustic waves
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/22—Details, e.g. general constructional or apparatus details
- G01N29/24—Probes
- G01N29/2412—Probes using the magnetostrictive properties of the material to be examined, e.g. electromagnetic acoustic transducers [EMAT]
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/22—Details, e.g. general constructional or apparatus details
- G01N29/28—Details, e.g. general constructional or apparatus details providing acoustic coupling, e.g. water
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/34—Generating the ultrasonic, sonic or infrasonic waves, e.g. electronic circuits specially adapted therefor
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/02—Indexing codes associated with the analysed material
- G01N2291/028—Material parameters
- G01N2291/02854—Length, thickness
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2291/00—Indexing codes associated with group G01N29/00
- G01N2291/02—Indexing codes associated with the analysed material
- G01N2291/028—Material parameters
- G01N2291/02872—Pressure
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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- G01N2291/042—Wave modes
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Abstract
The invention discloses an electromagnetic ultrasonic excitation device for detecting depth stress, which comprises a support body, a permanent magnet, an incident wedge block and a printed circuit board, wherein the support body is provided with a plurality of permanent magnets; the support body is composed of an excitation medium bottom plate, a permanent magnet placing frame and a connecting baffle. The device utilizes the excitation principle of the electromagnetic ultrasonic transducer to excite longitudinal waves in an excitation medium, and the longitudinal waves are conducted through the incident wedge block, so that critical refraction longitudinal waves are generated on the surface of a tested piece. Measuring the wave velocity of the critical refraction longitudinal wave under different excitation frequencies, and obtaining the stress under different excitation frequencies according to the linear relation between the wave velocity of the critical refraction longitudinal wave and the stress in the acoustic elasticity principle; according to the relation between the penetration depth of the critical refraction longitudinal wave on the surface of the tested piece and the excitation frequency, the penetration depth under different excitation frequencies is obtained, further, the corresponding relation between the penetration depth and the stress is obtained, and the stress magnitude under different depths can be calculated. The device can not damage the tested piece when in use, and belongs to nondestructive testing.
Description
Technical Field
The invention belongs to the field of electromagnetic ultrasonic detection, and particularly relates to an electromagnetic ultrasonic excitation device for depth stress detection.
Background
The residual stress generated by the non-uniform deformation of the material can influence the yield strength and the structural stability of the material, so that the measurement of the residual stress has great significance on the material structure and engineering safety. The residual Stress of most test pieces can change along with the change of the depth of the outer surface, and the Measurement of the residual Stress change at different depths is realized by using an electronic speckle interferometry in the document Rickert the o.S. Residual Stress by ESPI Hole-Drilling J. Procedia Cirp,2016,45: 203-.
In recent years, nondestructive testing methods have been increasingly used for stress testing and damage testing. Nondestructive testing can be carried out on the defects and physical parameters by utilizing an X-ray method, a neutron diffraction method, a magnetic measurement method and an ultrasonic method under the condition of not damaging a test specimen. The ultrasonic method is used for detecting the stress of a test piece based on the relation between the stress and the sound wave speed. In stress detection, the sensitivity of the critical refraction longitudinal wave to the tangential stress is highest, and the stress of the test piece can be detected by utilizing the change relation between the stress and the wave velocity of the critical refraction longitudinal wave. When the stress of the test piece is detected by using an ultrasonic method, the penetration depth of the critical refraction longitudinal wave in the test piece is related to the frequency of the critical refraction longitudinal wave, and the stress at different depths can be detected by different penetration depths. The stress of different depths of the test piece can be measured by changing the frequency of the critical refraction longitudinal wave, and the method is used for detecting the residual stress of different depths of the metal test piece.
At present, all devices generating critical refraction longitudinal waves adopt piezoelectric ultrasonic transducers, utilize a Thickness vibration Mode (Thickness Mode) of piezoelectric ceramics to generate longitudinal waves, and then obliquely irradiate the longitudinal waves into a detection test piece through a medium at a first critical angle according to Snell's law to obtain the critical refraction longitudinal waves. However, the resonant frequency of the thickness vibration mode of the piezoelectric ultrasonic transducer is related to the thickness of the piezoelectric ultrasonic transducer, and the piezoelectric ultrasonic transducer has fixed excitation frequency and bandwidth when the structure is determined, so that the piezoelectric ultrasonic transducer needs to be frequently replaced when the piezoelectric ultrasonic transducer is used for measuring the stress of a test piece at different depths.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to solve the technical problem of providing an electromagnetic ultrasonic excitation device for depth stress detection.
The invention provides an electromagnetic ultrasonic excitation device for detecting depth stress, which is characterized by comprising a support body, a permanent magnet, an incident wedge block and a printed circuit board;
the support body consists of an excitation medium bottom plate, a permanent magnet placing frame and a connecting baffle plate; permanent magnet placing racks are arranged on the left side and the right side of the excitation medium bottom plate; a connecting baffle is arranged between the two permanent magnet placing frames and is used for connecting the two permanent magnet placing frames and limiting the permanent magnets in the permanent magnet placing frames and simultaneously playing a role in magnetic concentration; a permanent magnet is respectively arranged in the two permanent magnet placing racks; the polarities of the magnetic poles at the corresponding positions of the two permanent magnets are opposite, the two permanent magnets are attracted to the middle through the opposite attraction effect and limited through the connecting baffle plate, and therefore the two permanent magnets are fixed in the permanent magnet placing frame;
one surface of the printed circuit board is printed with an exciting coil; the printed circuit board is fixed in the support body in a mode that one surface printed with the exciting coil faces downwards, so that the exciting coil is opposite to the upper surface of the exciting medium bottom plate; the upper surface of the incident wedge block is connected with the lower surface of the excitation medium bottom plate; during testing, a coupling medium is coated between the upper surface of the incident wedge and the lower surface of the excitation medium bottom plate; the front surface of the incidence wedge block is provided with a corrugated groove which is used for eliminating the reflected longitudinal wave in the incidence wedge block; the upper surface and the lower surface of the incidence wedge have the same inclination angle with the first critical angle calculated according to Snell's law.
Compared with the prior art, the invention has the beneficial effects that:
(1) the device utilizes the excitation principle of the electromagnetic ultrasonic transducer to excite longitudinal waves in an excitation medium, and the longitudinal waves are conducted through the incident wedge block, so that critical refraction longitudinal waves are generated on the surface of a tested piece. Measuring the wave velocity of the critical refraction longitudinal wave under different excitation frequencies, and obtaining the stress under different excitation frequencies according to the linear relation between the wave velocity of the critical refraction longitudinal wave and the stress in the acoustic elasticity principle; according to the relation between the penetration depth of the critical refraction longitudinal wave on the surface of the tested piece and the excitation frequency, the penetration depth under different excitation frequencies is obtained, further, the corresponding relation between the penetration depth and the stress is obtained, and the stress magnitude under different depths can be calculated.
(2) The device can not damage the tested piece when in use, and belongs to nondestructive testing.
(3) The frequency of the critical refraction longitudinal wave excited by the device is only related to the excitation frequency, so that the stress detection of different depths of the test piece can be carried out without replacing the whole device in the whole measuring process, the problem that the piezoelectric probe needs to be frequently replaced when the stress of different depths of the test piece is measured by an ultrasonic method is solved, and the detection efficiency is improved.
(4) The invention utilizes the acoustic-elastic method to measure the stress, has simple and convenient use method and small and exquisite device, and can be used for the field measurement of the stress of the test piece.
(5) The two permanent magnets are fixed in the supporting body by utilizing the principle that the magnetic poles attract each other in opposite directions, and the permanent magnets are not fixed by other structures.
(6) The arrangement positions of the two permanent magnets can provide a horizontal magnetic field for an excitation medium bottom plate below the excitation coil, so that excitation of longitudinal waves is facilitated, the support body is made of ferromagnetic materials, the connecting baffle plate can play a role in magnetism gathering, the horizontal magnetic field is increased to a certain degree, and the amplitude of the generated longitudinal waves is increased.
Drawings
FIG. 1 is an axial view of the overall structure of an embodiment of the present invention;
FIG. 2 is a left side view of the overall structure of an embodiment of the present invention;
FIG. 3 is a schematic top view of the overall structure of an embodiment of the present invention;
FIG. 4 is an axial view of a support body according to one embodiment of the present invention;
FIG. 5 is a schematic front view of a support body according to an embodiment of the present invention;
FIG. 6 is a schematic structural diagram of an excitation coil according to an embodiment of the present invention;
FIG. 7 is a schematic structural diagram of an incident wedge according to an embodiment of the present invention;
FIG. 8 is a schematic diagram of the detection according to an embodiment of the present invention.
In the figure: 1. a support body; 2. an excitation coil; 3. a permanent magnet; 4. an incident wedge; 5. a printed circuit board; 6. a test piece; 7. an acoustic receiving device; 1-1, exciting a medium bottom plate; 1-2, placing a permanent magnet rack; 1-3, connecting a baffle; 1-4, printed circuit board fixing groove; 1-5, an incident wedge block fixing groove; 2-1, an excitation zone; 2-2, a communicating region; 4-1, convex; 4-2, corrugated grooves; 5-1, welding holes.
Detailed Description
The present invention will be further described with reference to the following examples and accompanying drawings. The specific examples are only intended to illustrate the invention in further detail and do not limit the scope of protection of the claims of the present application.
The invention provides an electromagnetic ultrasonic excitation device (a device for short, see fig. 1-7) for depth stress detection, which is characterized by comprising a support body 1, a permanent magnet 3, an incident wedge 4 and a printed circuit board 5;
the support body 1 is an ultrasonic excitation medium and consists of an excitation medium bottom plate 1-1, a permanent magnet placing frame 1-2 and a connecting baffle plate 1-3; permanent magnet placing frames 1-2 are arranged on the left side and the right side of the excitation medium bottom plate 1-1; a connecting baffle plate 1-3 is arranged between the two permanent magnet placing frames 1-2 and is used for connecting the two permanent magnet placing frames 1-2 and limiting the permanent magnet 3 in the permanent magnet placing frame 1-2 and simultaneously playing a role in magnetic convergence; a permanent magnet 3 is respectively arranged in the two permanent magnet placing racks 1-2; the polarities of the magnetic poles at the corresponding positions of the two permanent magnets 3 are opposite (in the embodiment, the permanent magnet 3 with the upper N pole and the lower S pole is arranged in the permanent magnet placing frame 1-2 on the left side, and the permanent magnet 3 with the upper S pole and the lower N pole is arranged in the permanent magnet placing frame 1-2 on the right side), the two permanent magnets 3 are attracted to the middle through opposite attraction, and are limited through the connecting baffle plates 1-3, so that the two permanent magnets are fixed in the permanent magnet placing frame 1-2; the exciting medium bottom plate 1-1 is provided with a transparent incident wedge block fixing groove 1-5 which is used for being fixedly connected with an incident wedge block 4; the positions of the incident wedge block fixing grooves 1-5 are not overlapped with the exciting coil 2; a printed circuit board fixing groove 1-4 is arranged between the excitation medium bottom plate 1-1 and the permanent magnet placing frame 1-2, and different types of printed circuit boards 5 can be disassembled; an exciting coil 2 is printed on one surface of the printed circuit board 5; the printed circuit board 5 is inserted from the printed circuit board fixing groove 1-4 in a manner that the side printed with the exciting coil 2 is downward and fixed into the supporting body 1 so that the exciting coil 2 is opposed to the upper surface of the exciting medium base plate 1-1 (preferably, the exciting coil 2 is in contact with the upper surface of the exciting medium base plate 1-1);
the upper surface of the incident wedge block 4 is provided with a bulge 4-1 which is matched with an incident wedge block fixing groove 1-5 of the excitation medium bottom plate 1-1 to realize the connection of the upper surface of the incident wedge block 4 and the lower surface of the excitation medium bottom plate 1-1; during testing, coupling media such as glycerin are coated between the upper surface of the incident wedge 4 and the lower surface of the excitation medium bottom plate 1-1, and the coupling media are used for coupling the incident wedge 4 and the supporting block 1, so that the propagation of sound waves is facilitated; the front surface of the incidence wedge block 4 is provided with a corrugated groove 4-2 which is used for eliminating the reflected longitudinal wave of the longitudinal wave in the incidence wedge block 4 and preventing the sound wave from being incident into the tested piece 6 again after being reflected for multiple times in the incidence wedge block, and because the incident angle after being reflected for multiple times is not the first critical angle, other noise waves are generated in the tested piece 6 to influence the measurement result; the upper surface and the lower surface of the incident wedge 4 have a certain angle therebetween, i.e., a tilt angle, which is a first critical angle calculated according to snell's law.
The excitation medium bottom plate 1-1 is provided with a left transparent incident wedge block fixing groove 1-5 and a right transparent incident wedge block fixing groove 1-5, and the distance between the two incident wedge block fixing grooves 1-5 is larger than the width of the excitation coil 2; the center positions of the left side and the right side of the upper surface of the incidence wedge block 4 are respectively provided with a bulge 4-1 which is matched with respective incidence wedge block fixing grooves 1-5.
The excitation coil 2 is composed of an excitation area 2-1 and a communication area 2-2, and the excitation area 2-1 is connected through the communication area 2-2 to form the excitation coil 2; the excitation area 2-1 adopts wires arranged in parallel, so that the directions of excitation currents introduced into the same area at the same time are the same, induced eddy currents with the same direction and the same level are generated in the same area of the excitation medium bottom plate 1-1, and particles in the same area of the excitation medium bottom plate 1-1 are subjected to homotopic vibration by Lorentz force under the action of a horizontal magnetic field; the excitation area 2-1 is positioned between the two permanent magnets 3, preferably, the distance between the excitation area 2-1 and the two permanent magnets 3 is the same, and the center line of the excitation area 2-1 is collinear with the center lines of the two permanent magnets 3; the horizontal length of the excitation zone 2-1 is not more than the horizontal length of the upper surface of the incidence wedge 4; preferably, the vertical length of excitation region 2-1 is not less than the vertical length of the upper surface of incidence wedge 4, so that both communication region 2-2 and solder holes 5-1 on printed circuit board 5 are located outside the range of the upper surface of incidence wedge 4;
the excitation coil 2 is oblong (i.e., racetrack) or rectangular in shape.
The printed circuit board 5 is provided with a welding hole 5-1; the welding holes 5-1 are respectively connected with the inlet and outlet ends of the exciting coil 2 and an external exciting source through leads.
The support body 1 is made of ferromagnetic materials; cutting the printed circuit board 5 according to the size of the printed circuit board fixing groove 1-4; the exciting coil 2 is introduced with current with corresponding frequency according to the depth of the target measurement stress; the permanent magnet 3 is a neodymium iron boron magnet; the entrance wedge 4 is an acrylic material.
The working principle and the working process of the invention are as follows:
after the whole device is assembled, the incident wedge block 4 is placed on a tested piece 6 (the tested piece 6 adopts a metal test piece), and an ultrasonic coupling agent is coated between the lower surface of the incident wedge block 4 and the tested piece 6; placing the sound receiving device 7 on the tested piece 6, and placing the sound receiving device in front of the incidence wedge block 4 according to the propagation direction of the critical refraction longitudinal wave, wherein the front surface of the incidence wedge block 4 is opposite to the sound receiving device 7; between the device and the sound receiving device 7 is a detection area. The sound receiving device 7 includes a piezoelectric ultrasonic transducer and an electromagnetic ultrasonic transducer; when the piezoelectric ultrasonic transducer is adopted, an ultrasonic coupling agent is required to be coated between the piezoelectric ultrasonic transducer and the tested piece 6.
During testing, the permanent magnet 3 enables the upper surface of the excitation medium base plate 1-1 with the magnetic conduction function to generate a horizontal (parallel to the upper surface of the excitation medium base plate) magnetic field; after the exciting coil 2 is introduced with high-frequency exciting current, horizontal induced eddy current which is opposite to the direction of the introduced current and corresponds to the frequency (excitation frequency for short) of the high-frequency exciting current is generated on the upper surface of the exciting medium bottom plate 1-1 below the exciting coil 2; according to the left-hand rule, under the action of a horizontal magnetic field, a mass point of an excitation medium base plate 1-1 in the area where an induced eddy current is located is acted by a lorentz force vertical to the excitation medium base plate 1-1, the upper surface of the excitation medium base plate 1-1 generates a shear stress with corresponding frequency, mass point vibration vertical to the direction of the excitation medium base plate 1-1 is induced, and an incident longitudinal wave (the vibration direction of the mass point is parallel to the propagation direction of the wave, so the longitudinal wave) which is vertical to the excitation medium base plate 1-1 and propagates downwards is excited, wherein the frequency of the incident longitudinal wave is only related to the excitation frequency; the incident longitudinal wave is incident on the tested piece 6 through the incidence wedge 4 at a first critical angle, and a critical refraction longitudinal wave propagating along the surface can be generated on the surface of the tested piece 6, wherein the frequency of the critical refraction longitudinal wave is the same as that of the incident longitudinal wave.
The acoustic receiving device 7 is used for measuring wave velocity of critical refraction longitudinal waves at different excitation frequencies. Obtaining the stress under different excitation frequencies according to the linear relation between the wave speed of the critical refraction longitudinal wave and the stress in the acoustic elasticity principle (the wave speed of the critical refraction longitudinal wave is reduced along with the increase of the stress); according to the relation between the penetration depth of the critical refraction longitudinal wave on the surface of the tested piece 6 and the excitation frequency (the penetration depth is reduced along with the increase of the excitation frequency), the penetration depths under different excitation frequencies are obtained, and then the corresponding relation between the penetration depths and the stress is obtained, so that the stress of different depths of the tested piece 6 can be measured by changing the excitation frequency.
Examples
The support body 1 is made of an iron plate with the thickness of 1 mm; the size of the excitation medium base plate 1-1 is 80 multiplied by 54 multiplied by 1mm, the height of the permanent magnet placing rack 1-2 is 14mm, and the size is larger than that of the permanent magnet 3; the distance between the two permanent magnet placing racks 1-2 is 25 mm; the size of the printed circuit board fixing groove 1-4 is 3 multiplied by 1 mm; the size of the incident wedge fixing groove 1-5 is 2 x 4 mm.
The exciting coil 2 is in an oblong shape, the copper thickness is 0.3mm, the number of turns is 20, the width (horizontal length) of a single coil is 0.4mm, and the distance between the coils is 0.1 mm; in order to form a loop, the excitation area 2-1 is divided into a left area and a right area and is communicated through a communication area 2-2, the current directions in the two areas are opposite at the same time, the distance between the two areas is 3.6mm, and the length (vertical length) of a single coil is 30 mm.
The permanent magnet 3 is a neodymium iron boron magnet with the size of 50 multiplied by 25 multiplied by 12 mm.
The incident wedge block 4 is made of acrylic acid material, and the horizontal length is 30 mm; the size of the projection 4-1 is 2X 4X 1 mm.
The printed circuit board 5 is cut in accordance with the size of the printed circuit board fixing grooves 1-4, and the size of the printed circuit board 5 is 30 x 70mm x 0.5 mm.
The test piece 6 was a 5052 aluminum plate 10mm thick. Theoretically, the propagation velocity of longitudinal waves in aluminum is 6320m/s, and the propagation velocity in acrylic material is 2730 m/s. The first critical angle is 25.6 ° calculated by snell's law, i.e., the angle of inclination of the incident wedge 4 is 25.6 °, and the reception angle of the acoustic receiver 7 is also 25.6 °.
And starting a test, respectively introducing excitation currents of 0.5MHz, 1MHz, 1.5MHz, 2MHz and 2.5MHz into the excitation coil 2, and respectively generating critical refraction longitudinal waves of corresponding excitation frequencies in the detection area. Satisfying D ═ 6.4 xf in aluminum-0.96D is the penetration depth in mm; f is ultrasonic frequency, and the unit is MHz, and the corresponding penetration depth under different excitation frequencies is obtained.
The acoustic receiving means 7 measure the average wave velocity of critically refracted longitudinal waves at different excitation frequencies as they pass through the detection zone. According to the relation between the wave velocity of the critical refraction longitudinal wave and the stress, the corresponding average stress under different excitation frequencies can be obtained.
According to the corresponding penetration depth under different excitation frequencies and the corresponding average stress under different excitation frequencies, the relation between the penetration depth and the average stress under different excitation frequencies can be obtained. For the present embodiment: mean stresses corresponding to penetration depths of 12.45mm, 6.40mm, 4.34mm, 3.29mm and 2.66mm at excitation frequencies of 0.5MHz, 1MHz, 1.5MHz, 2MHz and 2.5MHz, respectively.
By adjusting the variation density of the excitation frequency, more accurate stress of the tested piece 6 at different depths can be obtained. Nothing in this specification is said to apply to the prior art.
Claims (10)
1. An electromagnetic ultrasonic excitation device for detecting depth stress is characterized by comprising a support body, a permanent magnet, an incident wedge block and a printed circuit board;
the support body consists of an excitation medium bottom plate, a permanent magnet placing frame and a connecting baffle plate; permanent magnet placing racks are arranged on the left side and the right side of the excitation medium bottom plate; a connecting baffle is arranged between the two permanent magnet placing frames and is used for connecting the two permanent magnet placing frames and limiting the permanent magnets in the permanent magnet placing frames and simultaneously playing a role in magnetic concentration; a permanent magnet is respectively arranged in the two permanent magnet placing racks; the polarities of the magnetic poles at the corresponding positions of the two permanent magnets are opposite, the two permanent magnets are attracted to the middle through the opposite attraction effect and limited through the connecting baffle plate, and therefore the two permanent magnets are fixed in the permanent magnet placing frame;
one surface of the printed circuit board is printed with an exciting coil; the printed circuit board is fixed in the support body in a mode that one surface printed with the exciting coil faces downwards, so that the exciting coil is opposite to the upper surface of the exciting medium bottom plate; the upper surface of the incident wedge block is connected with the lower surface of the excitation medium bottom plate; during testing, a coupling medium is coated between the upper surface of the incident wedge and the lower surface of the excitation medium bottom plate; the front surface of the incidence wedge block is provided with a corrugated groove which is used for eliminating the reflected longitudinal wave in the incidence wedge block; the upper surface and the lower surface of the incidence wedge have the same inclination angle with the first critical angle calculated according to Snell's law.
2. The electromagnetic ultrasonic excitation device for depth stress detection according to claim 1, wherein the excitation coil is in contact with an upper surface of the excitation medium base plate.
3. The electromagnetic ultrasonic excitation device for depth stress detection according to claim 1, wherein the excitation medium base plate is provided with a transparent incident wedge fixing groove, and the incident wedge fixing groove is not coincident with the excitation coil; the upper surface of the incidence wedge block is provided with a bulge which is matched with the incidence wedge block fixing groove to realize connection.
4. The electromagnetic ultrasonic excitation device for detecting depth stress according to claim 3, wherein the excitation medium base plate is provided with two left and right transparent incident wedge fixing grooves, and the distance between the two incident wedge fixing grooves is greater than the width of the excitation coil; the center positions of the left side and the right side of the upper surface of the incidence wedge block are respectively provided with a bulge which is matched with the respective incidence wedge block fixing grooves.
5. The electromagnetic ultrasonic excitation device for detecting depth stress according to claim 1, wherein a printed circuit board fixing groove is provided between the excitation medium base plate and the permanent magnet placing frame; the printed circuit board is inserted from the printed circuit board fixing groove in a manner that the side printed with the exciting coil faces downward and is fixed into the support body.
6. The electromagnetic ultrasonic excitation device for detecting depth stress according to claim 1, wherein the excitation coil is composed of an excitation region and a communication region, and the excitation regions are connected through the communication region to form the excitation coil; the excitation area adopts parallel arranged wires; the excitation area is positioned between the two permanent magnets; the horizontal length of the excitation zone is no greater than the horizontal length of the upper surface of the incidence wedge.
7. The device for detecting depth stress according to claim 6, wherein the distance between the excitation area and the two permanent magnets is the same and the center line of the excitation area is collinear with the center lines of the two permanent magnets.
8. The apparatus according to claim 6 or 7, wherein the vertical length of the excitation region is not less than the vertical length of the upper surface of the incidence wedge, so that the connection region and the solder hole of the printed circuit board are located outside the range of the upper surface of the incidence wedge.
9. The electromagnetic ultrasonic excitation device for depth stress detection according to claim 1 or 6, wherein the excitation coil has an oblong or rectangular shape.
10. The electromagnetic ultrasonic excitation device for depth stress detection according to claim 1, wherein said printed circuit board is provided with solder holes; the welding holes are respectively connected with the inlet and outlet ends of the exciting coil and an external exciting source.
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| CN113758623A (en) * | 2021-09-06 | 2021-12-07 | 西红柿科技（武汉）有限公司 | Adjustable steel structure stress monitoring sensor |
| CN115752835A (en) * | 2022-11-21 | 2023-03-07 | 北京理工大学 | Stress ultrasonic detection method and device |
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