CN112994514A - Giant magnetostrictive vibration source - Google Patents
Giant magnetostrictive vibration source Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02N—ELECTRIC MACHINES NOT OTHERWISE PROVIDED FOR
- H02N2/00—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction
- H02N2/02—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction producing linear motion, e.g. actuators; Linear positioners ; Linear motors
- H02N2/026—Electric machines in general using piezoelectric effect, electrostriction or magnetostriction producing linear motion, e.g. actuators; Linear positioners ; Linear motors by pressing one or more vibrators against the driven body
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Abstract
The invention discloses a giant magnetostrictive vibration source which comprises an excitation coil (5), wherein a magnetostrictive material rod (6) is arranged in the excitation coil (5) along the axial direction, an elastic vibration output piece (14) is arranged in the direction of the telescopic end of the magnetostrictive material rod (6), a limiting end cover (3) is arranged at one end, far away from the telescopic end, of the magnetostrictive material rod (6), and when the magnetostrictive material rod (6) deforms along the direction of the telescopic end under the action of the excitation coil (5), the detection end of the elastic vibration output piece (14) moves along the deformation direction of the magnetostrictive material rod. The giant magnetostrictive material rod is triggered to vibrate by transmitting a step excitation signal to the excitation coil, so that vibration is generated.
Description
Technical Field
The invention relates to the technical field of nondestructive testing of elastic waves, in particular to a giant magnetostrictive vibration source.
Background
When various fixed and installed metal devices and equipment are detected in the situations of damage, corrosion and the like, the metal devices and the equipment are generally directly observed in a disassembling or taking-out mode. However, in the case of a huge or expensive apparatus, the labor or labor for disassembling or removing is extremely high, and it is not suitable to remove it for inspection.
For example, a grounding grid, which exists in each link of a power system, is an extremely important part of the power system. Due to the limitation of economic conditions, the grounding grid in China uses a large amount of steel, the traditional grounding grid is generally made of galvanized flat steel, copper-coated flat steel is also used as the grounding grid material recently, and pure copper is generally used as the grounding grid material abroad. The grounding grid is directly buried under the soil, the copper material has better corrosion resistance, and even if the burying time in the soil exceeds 10 years, the copper material can still maintain better performance and is not corroded or broken, so that the foreign research on the defects of the grounding grid is less. The defects of the grounding grid can cause huge economic loss and social influence. In China, accidents of a power system caused by the defects of corrosion, breakage and the like of a grounding grid occur occasionally, and each accident causes great economic loss. The down lead part of the grounding grid is located on the ground and exposed in the air, and the down lead part of the grounding grid is buried in the soil. In southern areas with humid climate in China, the soil permeability and humidity change are large. Due to the galvanic effect, the corrosion rate of the down lead of the grounding grid is obviously higher than that of the horizontal conductor of the grounding grid, and in addition, the down lead of the grounding grid needs to bear large fault current sometimes, and the fault current can generate large electrodynamic force. Therefore, the down conductor of the grounding grid is the most vulnerable part of the whole grounding grid, so that the research on the fault diagnosis and the state evaluation of the down conductor of the grounding grid is particularly important. For the detection of the down lead of the grounding grid, the conventional excavation detection method is adopted at present, namely, the whole grounding grid is excavated, and then the corrosion of the grounding grid is judged by knocking or visual observation. This detection method has several problems as follows: the engineering quantity is large. Generally, the coverage area of a grounding grid is large, the buried depth is also deep, and the engineering quantity is large if the down conductor is detected in an excavation mode. ② the influence range is wide. If the grounding grid of the power plant or the transformer substation is detected in an excavation mode, the power plant or the transformer substation is shut down due to long construction period, and a large range of influence is generated. And thirdly, the detection result is inaccurate. In the excavation-type detection of the grounding grid, a mode of observing whether the down lead of the grounding grid is corroded or broken by naked eyes is adopted for detection under many conditions, and the detection mode can not effectively judge the defect phenomenon caused by internal cavities or internal corrosion in the down lead of the grounding grid due to quality problems. Therefore, there is a need to develop a convenient and economical detection method that does not require excavation in order to perform early diagnosis of the ground electrode before ground faults (e.g., corrosion and breakage of the down conductor) occur.
With the development of the technology, an impact type elastic wave diagnosis method appears in the year, and the key of the elastic wave diagnosis technology is how to design a vibration source with accuracy, controllability and reliable performance. In engineering, a hammer or explosive and other vibration excitation devices are commonly used for generating elastic waves by impact. The energy generated in this way is not easy to control and causes certain difficulties in the quantitative analysis of the defects of the down conductor of the grounding grid. Moreover, the explosive is controlled by law, and if the equivalent weight of the explosive is not well controlled, the equipment to be detected is easily damaged.
Disclosure of Invention
In order to solve the problems, the invention provides a giant magnetostrictive vibration source which uses a giant magnetostrictive material and transmits a step excitation signal to an excitation coil to trigger a giant magnetostrictive material rod to vibrate so as to generate vibration.
In order to achieve the purpose, the invention adopts the following specific technical scheme:
a giant magnetostrictive vibration source has the key technology that: the magnetostrictive vibration sensor comprises an excitation coil, wherein a magnetostrictive material rod is arranged in the excitation coil along the axial direction, an elastic vibration output piece is arranged in the direction of a telescopic end of the magnetostrictive material rod, a limiting end cover is arranged at one end, far away from the telescopic end, of the magnetostrictive material rod, and when the magnetostrictive material rod deforms along the direction of the telescopic end under the action of the excitation coil, a detection end of the elastic vibration output piece moves along the deformation direction of the magnetostrictive material rod.
Through the design, the magnetostrictive material is used as a core, and the precise vibration source for exciting vibration is realized by utilizing the magnetostrictive effect. When the magnetostrictive material rod is subjected to excitation expansion, as one end of the magnetostrictive material rod is limited by the limiting end cover, the expansion end of the magnetostrictive material rod can generate certain displacement and act on the elastic vibration output piece, and the detection end of the elastic vibration output piece vibrates along with the expansion direction of the magnetostrictive material rod, so that a vibration source is formed. The resulting vibration source impacts the target, thereby generating a vibration source of vibration signals. In order to avoid the mutual superposition interference of the vibration wave signal and the defect reflection signal on the defect diagnosis of the down lead, the magnetostrictive vibration source can use the rising edge of the transmitting current waveform of the transient electromagnetic transmitter to carry out single triggering.
According to a further technical scheme, a prestress action mechanism is arranged at one end, far away from the telescopic end, of the magnetostrictive material rod, the action force of the prestress action mechanism acts on the magnetostrictive material rod, and the action direction is along the telescopic direction of the telescopic end of the magnetostrictive material rod.
When the magnetostrictive material is not acted by a prestress, the magnetization directions of the magnetic domains in the material are randomly distributed. When the magnetostrictive material is subjected to an axial pre-compression stress, the magnetic domains in the material deflect radially in the direction of the applied force. At this time, the magnetostrictive material is shortened in the direction of the pre-stress. Therefore, under the same excitation magnetic field, the magnetostrictive material under the action of the pre-stress will obtain larger saturated magnetostrictive displacement, so that the magnetostrictive vibration source can generate better excitation effect, which is a main reason for introducing the pre-stress design into the magnetostrictive vibration source.
According to a further technical scheme, the prestress action mechanism comprises a flat head screw fixed on the limiting end cover, and the flat head end of the flat head screw abuts against the second bias magnet.
By adopting the scheme, the size of the prestress is changed by rotating the flat head screw and changing the depth of the thread, so that the prestress with different acting forces acts on the magnetostrictive material rod by combining vibration sources with different sizes.
In a further technical scheme, a first bias magnet is arranged between the telescopic end of the magnetostrictive material rod and the elastic vibration output piece; and a second bias magnet is arranged between one end of the magnetostrictive material rod, which is far away from the telescopic end, and the covering surface of the limiting end cover.
The first bias magnet and the second bias magnet are arranged to induce a bias magnetic field in the vibration source. The effect of the bias magnetic field is: when the driving signal adopts a periodic signal, the application of a bias magnetic field can eliminate twice of a frequency doubling effect), and the resonance of the magnetostrictive material and the driving magnetic field is realized. At the same time, the application of a bias magnetic field also helps to alter the linearity of the magnetic field within the magnetostrictive material rod. Therefore, the design of the bias magnetic field is critical to the magnetostrictive vibration source. The bias magnetic field can be a permanent magnet magnetic field, an electromagnet magnetic field and a magnetic cylinder magnetic field.
According to a further technical scheme, the giant magnetostrictive vibration source also comprises a vibration source cylinder, the vibration output end of the vibration source cylinder is sealed by a vibration end cover, and the detection end of the elastic vibration output part penetrates out of the vibration end cover; and one end of the vibration source cylinder, which is far away from the vibration output end, is sealed by the limiting end cover. The vibration source cylinder, the vibration end cover and the limiting end cover are all made of iron-silicon alloy materials.
The magnetostrictive vibration source provides a bias magnetic field by a bias magnet, and a coil provides a driving magnetic field, but a closed magnetic circuit cannot be formed in the magnetostrictive vibration source, so that larger magnetic leakage exists. By adopting the scheme, the vibration source cylinder, the vibration end cover and the limiting end cover form a magnetic conduction path. And the three adopt iron-silicon alloy materials, and the iron-silicon alloy material has good magnetic performance, high magnetic conductivity, small coercive force and small iron core loss.
According to a further technical scheme, the thicknesses of the vibration source cylinder, the vibration end cover and the limiting end cover are consistent.
According to a further technical scheme, the thicknesses of the vibration source cylinder, the vibration end cover and the limiting end cover are 5 mm.
The further technical scheme is as follows: a circle of limiting and fixing steps are protruded on the inner wall of the vibration source cylinder, and each limiting and fixing step comprises a coil mounting surface, an enclosing surface and an elastic vibration limiting surface; the limiting fixing step comprises a coil mounting surface side provided with the exciting coil; the first bias magnet is arranged in a space formed by surrounding surfaces of the limiting fixed step; the elastic vibration output part comprises a boss, and the stepped surface of the boss is abutted with the elastic vibration limiting surface of the limiting fixing step; the bottom of the boss is axially connected with a spring, and the other end of the spring is abutted against the vibration end cover; the spring is internally provided with a telescopic rod, the fixed end of the telescopic rod is fixedly connected with the bottom of the boss, and one end of the telescopic rod, which is far away from the fixed end, is used as the detection end of the elastic vibration output piece and penetrates through the vibration end cover.
By adopting the scheme, the exciting coil is fixed between the limiting end cover and the limiting fixing step, and when the limiting end cover is opened, the exciting coil is freely taken out. The first bias magnet is abutted to the telescopic end of the magnetostrictive material rod, the elastic vibration output piece is abutted to the first bias magnet, the magnetostrictive material rod, the first bias magnet and the elastic vibration output piece are arranged on the same line, when the magnetostrictive material rod stretches, the elastic vibration output piece is arranged to stretch back and forth, and the detection end of the elastic vibration output piece continuously vibrates. The elastic vibration output piece comprises a boss and a telescopic rod connected to the bottom of the boss, wherein the step surface of the boss is abutted to the elastic vibration limiting surface of the limiting fixed step, and when the magnetostrictive material rod contracts, the detection end can be controlled to recover the distance length. And through wear to establish the spring outside the telescopic link, one end is fixed in the boss bottom, and one end unsettled sets up, when the extension of boss top received the magnetostrictive material stick and acted on, the spring removes until the butt on the vibration end cover to continue the effect, make the spring extrusion back, the telescopic link passes the vibration end cover, stretches out from the vibration end cover. When the magnetostrictive material rod contracts, the telescopic rod contracts along with the magnetostrictive material rod.
According to a further technical scheme, the detection surface side of the vibration end cover is also movably connected with a fixing plate in parallel, a movable gap between the vibration end cover and the fixing plate is used for fixing a detected piece, and the detection end of the elastic vibration output piece vibrates on the detected piece.
By adopting the scheme, the movable gap between the vibration end cover and the fixing plate is used for fixing the detected piece and can be adjusted in a self-adaptive manner according to the size of the detected piece, and the telescopic rod extends into the movable gap from the vibration end cover and is used for generating vibration on the detected piece so as to realize detection of the detected piece.
According to a further technical scheme, the first bias magnet and the second bias magnet are neodymium iron boron permanent magnets.
In a further technical scheme, the magnetostrictive material rod is made of a ferro-gallium alloy material.
The iron-gallium alloy material has both mechanical property and magnetostriction property uniquely, and fills the gap between the traditional iron-nickel magnetostriction material and terbium-dysprosium iron material. The traditional iron-nickel magnetostrictive material has low magnetostrictive coefficient and weak output vibration signal. Although terbium dysprosium iron material has high magnetostriction coefficient, the material is brittle and easy to crack during operation. The currently designed iron-gallium alloy magnetostrictive vibration source participates in the experiment for more than two years, and the iron-gallium alloy material rod inside the iron-gallium alloy magnetostrictive vibration source is still quite intact.
The invention has the beneficial effects that: the magnetostrictive vibration source is designed by adopting a magnetostrictive material rod, a bias magnetic field, a magnetic conduction path and a prestress loading device.
The giant magnetostrictive material can greatly improve the energy conversion efficiency of the vibration source, the mechanical property of the iron-gallium alloy material is better, the tensile strength is 14 times of that of the terbium dysprosium iron material, and the iron-gallium alloy material with better mechanical property is adopted when the magnetostrictive vibration source is designed. Except the mechanical property, other parameters of the Tb-Dy-Fe material are better than those of the Fe-Ga alloy material, and the Tb-Dy-Fe material can be adopted when designing a high-frequency sensor.
The frequency doubling effect can be eliminated by applying the bias magnetic field, so that the magnetostrictive vibration source realizes the resonance of the vibration source and the driving magnetic field in the frequency sweeping working state. The bias magnetic field can greatly improve the distribution uniformity of the magnetic field in the giant magnetostrictive material rod, so that the output performance of the vibration source is better.
The magnetic conduction path is increased, so that magnetic leakage and loss can be reduced.
The magnetostrictive property of the iron gallium magnetostrictive material increases with the increase of the pre-stress.
Drawings
FIG. 1 is a schematic view of the giant magnetostrictive vibration source of the present invention in its entirety;
FIG. 2 is a cross-sectional view of a giant magnetostrictive vibration source of the present invention;
FIG. 3 is a top view of the giant magnetostrictive vibration source of the present invention;
FIG. 4 is a diagram illustrating the relationship between the magnitude of magnetostrictive stress Tm and the magnetic induction B;
FIG. 5 is a graph of the relationship of prestress to saturated magnetostriction coefficient;
FIG. 6 is a graph of initial magnetization;
FIG. 7 is a graph illustrating the improved effect of a bias magnet on the magnetic field in a magnetostrictive rod;
FIG. 8 is a graph showing the relationship between the magnetic flux density in a rod of Fe83Ga17 magnetostrictive material and the thickness d1 of a magnetic conductive path;
FIG. 9 is a graph showing a comparison of magnetic flux densities in a rod of Fe83Ga17 magnetostrictive material with and without a magnetic flux path added to the magnetostrictive source.
Detailed Description
The following provides a more detailed description of the embodiments and the operation of the present invention with reference to the accompanying drawings.
As can be seen from fig. 1 to 3, a giant magnetostrictive vibration source includes an excitation coil 5, a magnetostrictive material rod 6 is axially disposed in the excitation coil 5, an elastic vibration output member 14 is disposed in a direction of a telescopic end of the magnetostrictive material rod 6, a limiting end cap 3 is disposed at an end of the magnetostrictive material rod 6 away from the telescopic end, and when the magnetostrictive material rod 6 deforms in the direction of the telescopic end under the action of the excitation coil 5, a detection end of the elastic vibration output member 14 moves in the deformation direction.
In this embodiment, the magnetostrictive material rod 6 is made of an iron-gallium alloy material. The magnetostrictive material rod 6 is made of Fe83Ga17 alloy.
Wherein, the magnetostrictive mathematical model is as follows: the magnetostrictive component in any direction can be calculated using the nonlinear equation for magnetization as follows:
the magnetostrictive elongation λ i along direction i depends on the magnetostrictive constant λ s and the magnetization direction cosine value α i. The magnetization direction cosine value α i is the ratio of the magnetization Mi along the magnetization direction and the saturation magnetization Ms of the material.
The formula 3.3 is brought into the formula 3.2
The term-1/3 in the above equation indicates that the magnetic moments in the material are random in the absence of any external magnetic field or pre-stress. In design, sufficient pre-stress is applied to the magnetostrictive material so that at the beginning of the magnetization process all magnetic moments are perpendicular to the magnetization direction and so the-1/3 term can be ignored with sufficient pre-stress applied to the magnetostrictive material, and the magnetization equation used in the actual modeling can be derived:
it can be seen that the amount of magnetostrictive elongation in a certain direction depends on the magnetostrictive constant λ s and the magnetization Mi in that direction.
For hysteresis, the Gils-Arthuton model can be used for description:
Mrev＝c(Man-Mirr) (3.8)
Mi＝Mirr+Mrev (3.9)
in the equation set, Man is the magnetic hysteresis-free intensity, Ms is the saturation magnetization intensity of the magnetostrictive material rod, He is the effective magnetic field intensity, a is the shape coefficient of the magnetic hysteresis-free magnetization intensity of the magnetostrictive material rod, Mirr is the irreversible magnetization intensity, sigma is the axial stress applied to the magnetostrictive material rod, E is the young modulus of the magnetostrictive material, ξ is the energy coupling coefficient of the unit volume of the magnetostrictive material, Mrev is the reversible magnetization intensity, c is the reversible coefficient, which can be generally regarded as a constant in calculation, and H0 is the initial magnetic field intensity.
For the relationship between the magnetization Mi and the stress σ, a magneto-mechanical coupling model is used for description
For the relationship between the magnetization Mi and the magnetic field strength H, a differential susceptibility can be used for description
In the above formula, δ becomes +1 when the magnetic field strength increases, and δ becomes-1 when the magnetic field strength decreases.
Frequency doubling effect
The frequency doubling effect is that the frequency of the magnetostrictive rod vibration is twice of the alternating magnetic field of the magnetic field, and is called frequency doubling effect. In magnetostrictive materials, the deformation of the material has an important characteristic that the magnetostrictive coefficient lambda of the magnetostrictive material is approximately proportional to the square of the magnetic induction B:
in the above formula, k (B) represents a proportional function, which is a function of the magnetic induction B.
The magnetostrictive material will deform due to magnetostrictive stress Tm generated inside the magnetostrictive material, which can be obtained from the Hooke's law:
wherein E is the Young's modulus of the magnetostrictive material
Tm＝E×k(B)×B2＝F(B)×B2 (3.15)
In the above formula, F (B) is a proportional function, and the magnitude of the magnetostrictive stress is related to the magnetic induction B in a quadratic function manner, as shown in FIG. 4.
The drive field is assumed to be a magnetic field that varies periodically with time:
B＝Bmsin(ωt) (3.16)
substituting formula 3.16 into formula 3.15 yields:
in the above formula, the term f (b) × Bm2 can be regarded as the constant K', and:
therefore, two parts exist in the magnetostrictive stress generated by the driving magnetic field in the magnetostrictive rod, namely a constant stress part and an alternating stress part, and the frequency of the alternating stress is twice of the frequency of the driving magnetic field, so that the magnetostrictive stress is called as a frequency doubling effect.
In this embodiment, as can be seen from fig. 2, a prestressing force applying mechanism 1 is disposed at an end of the magnetostrictive material rod 6 far from the telescopic end, and the acting force of the prestressing force applying mechanism 1 acts on the magnetostrictive material rod 6, and the acting direction is along the telescopic direction of the telescopic end of the magnetostrictive material rod 6.
In this embodiment, the prestressing mechanism 1 comprises a grub screw fixed to the end cap, the grub screw having its grub end abutting against the second biasing magnet 11.
As can be seen from fig. 5, under the action of the excitation magnetic field, the elongation λ x of the magnetostrictive material rod after the application of the pre-stress is equal to the sum of the shortening λ k of the magnetostrictive material rod generated by the pre-stress and the elongation λ of the magnetostrictive material rod when the pre-stress is not applied. Such as lambdax＝λ+λk. Table 1 shows the relationship between the prestress and the magnetostriction coefficient of the fe-ga alloy material, and a prestress-saturation magnetostriction coefficient relationship curve can be fitted according to table 1, which is detailed in fig. 5.
TABLE 1 relationship table of prestress and magnetostriction coefficient of Fe-Ga alloy material
When the applied prestress is increased from 0MPa to 21MPa, the saturation magnetostriction coefficient is increased continuously from 240ppm to 300ppm, the magnetostriction performance is increased by 25%, the increase speed of the saturation magnetostriction coefficient is increased continuously from the initial 10ppm/7MPa to 30ppm/7MPa, and the increase amplitude is 300%. However, after the prestress reaches 28MPa, the saturation magnetostriction coefficient is continuously increased along with the prestress, but the increasing speed is seriously reduced, and when the prestress is increased from 28MPa to 42MPa, the saturation magnetostriction coefficient is only increased from 315ppm to 320ppm, and the increasing amplitude is only 1.5%. Although the iron-gallium alloy has high tensile strength, the compressive strength is low, namely 100MPa, and the fatigue strength is only 75MPa, so that the effect of the unit prestress needs to be considered when the prestress design is carried out on the Fe83Ga17 magnetostrictive vibration source. In order to avoid excessive prestressing and thus reduced life of the magnetostrictive source. Therefore, it is necessary to avoid prestressing in the vicinity of the range of fatigue strength of the iron-gallium alloy. Considering that the effect increase brought by the prestress is not obvious after the prestress reaches 28MPa, but the risk of damaging the magnetostrictive material is gradually increased, the prestress of 28MPa is finally determined to be used as the prestress of the Fe83Ga17 magnetostrictive vibration source. The pre-stress is provided by an M5 screw on top of the magnetostrictive source end cap.
In the present embodiment, the stress of the M5 screw is 549.8N when the prestress of 28MPa is adopted, and the prestress can be provided by using the M5 screw of 3.6 grade.
In this embodiment, as can also be seen in connection with fig. 2, a first biasing magnet 13 is arranged between the telescopic end of the magnetostrictive material rod 6 and the elastic vibration output member 14; and a second bias magnet 11 is arranged between one end of the magnetostrictive material rod 6 far away from the telescopic end and the covering surface of the limiting end cover 3.
When the magnetic field strength H is gradually increased from 0, the magnetic induction B will also increase, and the initial magnetization curve thereof is shown in fig. 6. From the coordinate origin to the point a, when the magnetization starts, the magnetic induction intensity increases slowly due to the weak external magnetic field. From the point a to the point b, with the enhancement of the external magnetic field, a large number of magnetic domains in the Fe83Ga17 alloy begin to turn and tend to the direction of the external magnetic field, and the magnetic induction intensity is increased fastest at the moment. From point b to point c, since most of the magnetic domains in the Fe83Ga17 alloy are turned, the number of magnetic domains that can be turned is reduced, and thus the rate of magnetic induction increase is reduced until point c is saturated. From the point c to the point d, the magnetization curve of the saturated Fe83Ga17 alloy is parallel to the initial magnetization curve of the non-ferromagnetic material, and the magnetic induction intensity increases very slowly with the increase of the magnetic field intensity. Combining the principle that the bias magnetic field eliminates the frequency doubling effect, the bias magnetic field intensity of the magnetostrictive vibration source should be optimally set at Hx, the position of the point should be between Ha and Hc, and the following conditions should be met:
at this time, the magnetostrictive amount Δ l of the magnetostrictive material rod of Fe83Ga17 alloy is generated by the driving magnetic fieldxPartly by a bias fieldp。
Two pieces of Nd-Fe-B permanent magnets with common specification phi 14 x 10mm in the market are simulated by COMSOL software under different bias magnet specifications. The magnetic field data of the Fe83Ga17 rods with different bias magnet specifications shown in Table 2 were obtained.
TABLE 2 magnetic field in Fe83Ga17 bars under different bias magnet specifications
In table 2, when a neodymium iron boron permanent magnet having a residual flux density of 1.4T of N48 standard was used as the bias magnet, the uniformity of the flux density in the magnetostrictive material rod of Fe83Ga17 was the best, and the uniformity coefficient of the flux density reached 92.70%, which was 13.90 times the uniformity coefficient of the flux density of the magnetostrictive material rod without the bias magnet. At this time, Bmax was 1.165T, which was 1.94 times the maximum magnetic flux density of the magnetostrictive material rod without the bias magnet, which was 0.6T. Therefore, when the neodymium iron boron bias magnet of the N48 standard is used, the distribution uniformity of the magnetic flux density in the magnetostrictive rod is optimal, the output of each part in the magnetostrictive material rod is the most consistent, and the output effect is optimal. The improved effect of the biasing magnet on the magnetic field in the magnetostrictive rod is shown in fig. 7.
In this embodiment, when designing the Fe83Ga17 magnetostrictive source, two N48-sized cylindrical ndfeb permanent magnets are finally used as the bias magnetic field.
As can be seen in fig. 2, the vibration source device further comprises a vibration source cylinder 4, wherein the vibration output end of the vibration source cylinder 4 is sealed by a vibration end cover 8, and the detection end of the elastic vibration output element 14 penetrates out of the vibration end cover 8; and one end of the vibration source cylinder 4, which is far away from the vibration output end, is sealed by the limiting end cover 3.
In this embodiment, the limit end cover 3 is fixed and sealed with the vibration source cylinder 4 by screws, and the vibration source cylinder 4 is fixedly connected with the vibration end cover 8 by screws.
In this embodiment, the vibration source cylinder 4, the vibration end cover 8, and the limit end cover 3 are made of iron-silicon alloy materials. The iron-silicon alloy is also called as electrical steel, and has good magnetic property, high magnetic conductivity, small coercive force and small iron core loss. For the design of the magnetic conductive path, the most important part is to design the thickness of the magnetic conductive path. The COMSOL software is utilized to establish a model for the magnetic conduction path, the vibration source cylinder 4, the vibration end cover 8 and the limiting end cover 3 adopt the same thickness, the thickness d1 of the magnetic conduction path is parametrically scanned, the relation between the magnetic flux density in the Fe83Ga17 magnetostrictive material rod and the thickness d1 of the magnetic conduction path is obtained, and in combination with the graph 8, along with the increase of the thickness of the magnetic conduction path, the uniform coefficient beta of the magnetic flux density in the Fe83Ga17 magnetostrictive material rod is gradually reduced, and the uniformity of the magnetic flux density in the rod is poorer. The relationship between the magnetic flux density uniformity coefficient and the thickness d1 of the magnetic conductive path is shown in table 3.
TABLE 3 relationship table of the uniformity coefficient of magnetic flux density beta with the thickness d1 of the magnetic conductive path
From the table it follows: the flux density uniformity coefficient beta decreases with the increase of the thickness of the magnetic conductive path, but the decreasing speed of the flux density uniformity coefficient beta gradually decreases, and particularly after the thickness d1 of the magnetic conductive path reaches 5mm, the decreasing speed of the flux density uniformity coefficient beta is very slow. However, as the thickness of the magnetic path increases, the magnetic flux density in the rod of magnetostrictive material also increases as the thickness of the magnetic path increases. When the scheme of the magnetic conduction barrel with the thickness of 1mm is adopted, the uniformity coefficient of the magnetic flux density is optimal, the uniformity coefficient beta of the magnetic flux density is 89.35%, but the maximum magnetic flux density in the magnetostrictive rod does not reach the saturation value at the moment. When the thickness of the magnetic conduction barrel is 5mm, the maximum magnetic flux density in the magnetostrictive rod reaches a saturation value, and at the moment, although the average coefficient beta of the magnetic flux density in the magnetostrictive rod is reduced by 2.86 percent compared with the scheme of the magnetic conduction barrel with the thickness of 1mm, the maximum magnetic flux density in the magnetostrictive rod is increased by nearly 5.07 percent. The thickness of the magnetic conduction path is continuously increased, the magnetic flux density in the magnetostrictive rod is slightly increased, and the effect is not large. Therefore, for the design of the magnetic conduction path, in this embodiment, a scheme of a magnetic conduction barrel with a thickness of 5mm is finally adopted
In the magnetostrictive vibration source additionally provided with the magnetic conduction circuit, the uniformity of the magnetic flux density in the Fe83Ga17 magnetostrictive material rod is excellent, and the magnetic flux density in the magnetostrictive rod reaches the saturation magnetic flux density, so that the magnetic flux density in the magnetostrictive rod is increased by 37% compared with the design scheme without the magnetic conduction circuit. The magnetic flux density ratio in the rod of the magnetostrictive material of Fe83Ga17 in the magnetostrictive vibration source with and without the magnetic conductive path is shown in fig. 9. As can be seen from the figure, the magnetic path reduces the magnetic flux leakage and has a great influence on the magnetic flux density in the magnetostrictive rod.
As can also be seen from fig. 1 to 3, a circle of limiting fixing steps 18 protrudes from the inner wall of the vibration source cylinder 4, and the limiting fixing steps 18 include a coil mounting surface, a surrounding surface and an elastic vibration limiting surface; the limiting fixing step 18 is provided with the exciting coil 5 on the side of the coil mounting surface; the first bias magnet 13 is arranged in a space surrounded by the surrounding surface of the limit fixing step 18; the elastic vibration output part 14 comprises a boss, and the stepped surface of the boss is abutted with the elastic vibration limiting surface of the limiting fixing step 18; the bottom of the boss is axially connected with a spring, and the other end of the spring is abutted against the vibration end cover 8; a telescopic rod is arranged in the spring, the fixed end of the telescopic rod is fixedly connected with the bottom of the boss, and one end, far away from the fixed end, of the telescopic rod is used as the detection end of the elastic vibration output piece 14 and penetrates through the vibration end cover 8.
As can be seen from fig. 2, a fixing plate 10 is movably connected in parallel to the detection surface side of the vibrating end cap 8, a movable gap between the vibrating end cap 8 and the fixing plate 10 is used for fixing the detected object 9, and the detection end of the elastic vibration output element 14 vibrates on the detected object 9. In the embodiment, the vibrating end cover 8 and the fixing plate 10 are connected and fixed through bolts and nuts, and the distance of the movable space is set.
As can be seen from fig. 3, the limiting end cover 3 is further provided with a threading hole 17 for threading to connect the excitation coil with the transient electromagnetic transmitter, the transient electromagnetic transmitter transmits a step excitation signal, and the rising edge of the step excitation signal is used for triggering the giant magnetostrictive vibration source to excite vibration.
It should be noted that the above description is not intended to limit the present invention, and the present invention is not limited to the above examples, and those skilled in the art may make variations, modifications, additions or substitutions within the spirit and scope of the present invention.
Claims (10)
1. A giant magnetostrictive vibration source is characterized in that: the magnetostrictive vibration sensor comprises an excitation coil (5), a magnetostrictive material rod (6) is arranged in the excitation coil (5) along the axial direction, an elastic vibration output part (14) is arranged in the direction of the telescopic end of the magnetostrictive material rod (6), a limiting end cover (3) is arranged at one end, far away from the telescopic end, of the magnetostrictive material rod (6), and when the magnetostrictive material rod (6) deforms under the action of the excitation coil (5) along the direction of the telescopic end, the detection end of the elastic vibration output part (14) moves along the deformation direction.
2. The giant magnetostrictive vibration source according to claim 1, characterized in that: one end, far away from the telescopic end, of the magnetostrictive material rod (6) is provided with a prestress action mechanism (1), the action force of the prestress action mechanism (1) acts on the magnetostrictive material rod (6), and the action direction is along the telescopic direction of the telescopic end of the magnetostrictive material rod (6).
3. A magnetostrictive vibration source as claimed in claim 1 or 2, characterized in that: a first bias magnet (13) is arranged between the telescopic end of the magnetostrictive material rod (6) and the elastic vibration output piece (14);
and a second bias magnet (11) is arranged between one end of the magnetostrictive material rod (6) far away from the telescopic end and the covering surface of the limit end cover (3).
4. A giant magnetostrictive vibration source as claimed in claim 3, characterized in that: the vibration source device is characterized by also comprising a vibration source cylinder (4), wherein the vibration output end of the vibration source cylinder (4) is sealed by a vibration end cover (8), and the detection end of the elastic vibration output part (14) penetrates out of the vibration end cover (8);
and one end of the vibration source cylinder (4) far away from the vibration output end is sealed by the limiting end cover (3).
5. The giant magnetostrictive vibration source according to claim 4, characterized in that: the vibration source cylinder (4), the vibration end cover (8) and the limiting end cover (3) are made of iron-silicon alloy materials.
6. A giant magnetostrictive vibration source as claimed in claim 3, characterized in that: the prestress action mechanism (1) comprises a flat head screw fixed on the limit end cover, and the flat head end of the flat head screw abuts against the second bias magnet (11).
7. The giant magnetostrictive vibration source according to claim 4, characterized in that: a circle of limiting and fixing steps (18) are protruded on the inner wall of the vibration source cylinder (4), and each limiting and fixing step (18) comprises a coil mounting surface, a surrounding surface and an elastic vibration limiting surface;
the excitation coil (5) is arranged on the side, including the coil mounting surface, of the limiting fixing step (18);
the first bias magnet (13) is arranged in a space formed by the surrounding surface of the limiting fixed step (18);
the elastic vibration output part (14) comprises a boss, and the stepped surface of the boss is abutted with the elastic vibration limiting surface of the limiting fixing step (18); the bottom of the boss is axially connected with a spring, and the other end of the spring is abutted against the vibration end cover (8); a telescopic rod is arranged in the spring, the fixed end of the telescopic rod is fixedly connected with the bottom of the boss, and one end, far away from the fixed end, of the telescopic rod is used as the detection end of the elastic vibration output piece (14) and penetrates through the vibration end cover (8).
8. The giant magnetostrictive vibration source according to claim 4, characterized in that: the detection surface side of the vibration end cover (8) is also movably connected with a fixing plate (10) in parallel, a movable gap between the vibration end cover (8) and the fixing plate (10) is used for fixing a detected piece (9), and the detection end of the elastic vibration output piece (14) vibrates on the detected piece (9).
9. A giant magnetostrictive vibration source as claimed in claim 3, characterized in that: the first bias magnet (13) and the second bias magnet (11) are neodymium iron boron permanent magnets.
10. The giant magnetostrictive vibration source according to claim 1, characterized in that: the magnetostrictive material rod (6) is made of an iron-gallium alloy material.
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| CN116519113A (en) * | 2023-07-04 | 2023-08-01 | 山东科技大学 | Method for measuring vibration of object to be measured based on fiber bragg grating and vibration sensor |
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| CN116519113A (en) * | 2023-07-04 | 2023-08-01 | 山东科技大学 | Method for measuring vibration of object to be measured based on fiber bragg grating and vibration sensor |
| CN116519113B (en) * | 2023-07-04 | 2023-09-26 | 山东科技大学 | Method for measuring vibration of object to be measured based on fiber bragg grating and vibration sensor |
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