CN113312746B - Method for predicting service performance of permanent magnet - Google Patents
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- 230000005415 magnetization Effects 0.000 claims abstract description 23
- 238000007725 thermal activation Methods 0.000 claims abstract description 15
- 238000013178 mathematical model Methods 0.000 claims abstract description 13
- 230000007774 longterm Effects 0.000 claims abstract description 12
- 238000005259 measurement Methods 0.000 claims description 12
- 230000004888 barrier function Effects 0.000 claims description 4
- 238000009795 derivation Methods 0.000 claims description 4
- 230000002427 irreversible effect Effects 0.000 claims description 4
- 230000035699 permeability Effects 0.000 claims description 2
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- 238000010408 sweeping Methods 0.000 description 5
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- NAWXUBYGYWOOIX-SFHVURJKSA-N (2s)-2-[[4-[2-(2,4-diaminoquinazolin-6-yl)ethyl]benzoyl]amino]-4-methylidenepentanedioic acid Chemical compound C1=CC2=NC(N)=NC(N)=C2C=C1CCC1=CC=C(C(=O)N[C@@H](CC(=C)C(O)=O)C(O)=O)C=C1 NAWXUBYGYWOOIX-SFHVURJKSA-N 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 3
- 230000005347 demagnetization Effects 0.000 description 2
- 238000011534 incubation Methods 0.000 description 2
- 230000005381 magnetic domain Effects 0.000 description 2
- 239000000696 magnetic material Substances 0.000 description 2
- 238000011160 research Methods 0.000 description 2
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- 229910000938 samarium–cobalt magnet Inorganic materials 0.000 description 2
- 238000009825 accumulation Methods 0.000 description 1
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- 230000006866 deterioration Effects 0.000 description 1
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- 230000004907 flux Effects 0.000 description 1
- 239000008204 material by function Substances 0.000 description 1
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Abstract
The invention discloses a method for predicting the service performance of a permanent magnet, which predicts the magnetic performance change condition of the permanent magnet in the long-term service process by establishing a mathematical model of demagnetizing quantity h irr and time of the permanent magnet, wherein the established mathematical model specifically comprises the following steps: wherein H f represents a thermal activation field of the permanent magnet at a certain temperature T; Representing the form factor of the permanent magnet device; m (t 0) represents the magnetization of the permanent magnet at the initial time t 0; t 0 is the initial time; t is the time to be predicted. The method can accurately predict the performance change condition of the permanent magnet in the long-term service process, greatly shortens the service life detection time of the permanent magnet, and enables the permanent magnet with new brands or new components to be rapidly put into the practical application process.
Description
Technical Field
The invention relates to the technical field of permanent magnet performance, in particular to a method for predicting service performance of a permanent magnet.
Background
Permanent magnet materials serve as important functional materials and play an irreplaceable important role in various fields. In the specific application process of the permanent magnet material, people not only want to have good magnetic performance, but also want the material to provide a stable and reliable magnetic field environment for equipment in the long-term use process, otherwise once the performance of the permanent magnet changes too much, the equipment may have problems, so that the precision of the whole equipment is reduced and even the equipment is damaged. Through continuous research, many factors affecting the stability of the magnet are overcome, but the demagnetization of the magnet still exists, namely the time stability of the permanent magnet material, and the problem is also an important link of the application research of the permanent magnet material.
The magnetic viscous theoretical model in the prior art considers that the magnetic flux loss and the logarithm of time are in a linear change relation, and then proves that the theory is consistent with the experimental result, but the theory and the experimental result can not be reasonably and effectively combined up to the present, the judging method of the magnetic property change condition of the permanent magnet in the service process generally comprises the steps of recording the performances of the permanent magnet at different time points through long-term simulation environment experiments, fitting a large amount of data through long-time data accumulation, and judging the deterioration condition of the performances of the permanent magnet of the same type in the service process according to the fitting result.
Disclosure of Invention
The invention aims to provide a method for predicting the service performance of a permanent magnet, which can accurately predict the performance change condition of the permanent magnet in the long-term service process, greatly shorten the service life detection time of the permanent magnet and enable a new brand or new component permanent magnet to be rapidly put into the practical application process.
The invention aims at realizing the following technical scheme:
a method of predicting permanent magnet service performance, the method comprising:
The magnetic property change condition of the permanent magnet in the long-term service process is predicted by establishing a mathematical model of the demagnetizing quantity h irr and time of the permanent magnet, wherein the established mathematical model specifically comprises the following steps:
wherein H f represents a thermal activation field of the permanent magnet at a certain temperature T; Representing the form factor of the permanent magnet device; m (t 0) represents the magnetization of the permanent magnet at the initial time t 0; t 0 is the initial time; t is the time to be predicted;
By using the formula, the thermal activation field H f of the permanent magnet to be predicted at a certain temperature T, the magnetization M (T 0) at the initial time T 0 and the shape factor of the permanent magnet device to be predicted are measured and calculated The magnetic property change condition of the permanent magnet to be predicted at the time t to be predicted can be accurately predicted.
According to the technical scheme provided by the invention, the performance change condition of the permanent magnet in the long-term service process can be accurately predicted by the method, the service life detection time of the permanent magnet is greatly shortened, the new license plate or the new component permanent magnet can be rapidly put into the practical application process, and accurate and reliable data support is provided for the application of the permanent magnet.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the description of the embodiments will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of the change in remanence of a permanent magnet in a continuous 500 ℃ temperature environment in an example of the invention;
FIG. 2 is a schematic diagram showing the variation of the demagnetization quantity of the permanent magnet with time according to the embodiment of the present invention;
FIG. 3 is a schematic diagram of hysteresis loops of a magnet sample at 500 ℃ for different speed measurements according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a curve represented by an experimental fitting formula and a theoretical derivation formula according to an embodiment of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to fall within the scope of the invention.
The embodiment of the invention is further described in detail below with reference to the accompanying drawings, and provides a method for predicting service performance of a permanent magnet, wherein a mathematical model of demagnetizing quantity h irr and time of the permanent magnet is established to predict magnetic performance change condition of the permanent magnet in a long-term service process, and the established mathematical model is specifically as follows:
wherein H f represents a thermal activation field of the permanent magnet at a certain temperature T; Representing the form factor of the permanent magnet device; m (t 0) represents the magnetization of the permanent magnet at the initial time t 0; t 0 is the initial time; t is the time to be predicted;
By using the formula, the thermal activation field H f of the permanent magnet to be predicted at a certain temperature T, the magnetization M (T 0) at the initial time T 0 and the shape factor of the permanent magnet device to be predicted are measured and calculated The magnetic property change condition of the permanent magnet to be predicted at the time t to be predicted can be accurately predicted.
The deduction process of the mathematical model specifically comprises the following steps:
Firstly, according to the basic principle of the magnetic viscosity theory, in the service process of the permanent magnet, the magnetization intensity of the permanent magnet is in a linear change relation with the logarithm of time, namely:
M(t)＝M(t0)-Sln(t/t0) (1)
Wherein M (t 0) and M (t) respectively represent the magnetization of the permanent magnet at the initial time t 0 and the magnetization at the time iota; s represents the magnetic viscosity coefficient of the permanent magnet, expressed as:
wherein k B represents a boltzmann constant; t represents the temperature of the service environment of the permanent magnet; Representing the density of the energy barrier created by the coercive field; Representing irreversible magnetic susceptibility, M representing the magnetization of the permanent magnet; h represents the coercive field of the permanent magnet;
The mathematical expression of the energy barrier E A is:
Wherein K 1 represents the anisotropic constant of the permanent magnet in the service temperature environment, and can be obtained by measurement and calculation, and for the same material, K 1 is a fixed value at a certain temperature, and the constant values of different magnetic materials are different; v 0 represents the thermal activation volume of the permanent magnet in the service environment, specifically, after the thermal activation field is measured, the value is obtained through calculation; h 0 represents the anisotropic field of the permanent magnet in the service environment, the H 0 can be directly obtained by measurement, specifically, initial magnetization curves of the magnetic material along an easy axis and a difficult axis are respectively measured, the two curves are magnetized to the intersection point when saturation, and the corresponding magnetic field intensity represents the anisotropic field;
According to the linear change rule of the magnetic viscosity theory, the index m=1 in the formula (3);
H 0＝2K1/μ0Ms, according to the theoretical derivation process, constant 2 in the anisotropy field H 0 is incorporated as a non-significant parameter into the variable parameter, whereby it is possible to obtain according to formula (3):
Wherein μ0 represents vacuum permeability; ms represents the saturation magnetization of the magnet;
Further, as the permanent magnet is used as a main magnetic field source in the service process, the influence of the weak magnetic field of the external environment on the permanent magnet is negligible, and the permanent magnet is mainly influenced by the demagnetizing field H d, namely:
Wherein, Representing the form factor of the permanent magnet device;
The irreversible susceptibility χ irr of the permanent magnet is expressed as:
and then the formulas (2), (4) and (6) are brought into the formula (1), so that the change relation of the magnetization intensity of the permanent magnet along with time is obtained:
In formula (7), k BT/μ0MxV0 represents the thermal activation field H f of the permanent magnet at a certain temperature T;
And then processing the formula (7), and dividing the two sides by the magnetization intensity M (t 0) of the permanent magnet at the initial time t 0 at the same time to obtain the change relation of the demagnetizing quantity of the permanent magnet along with time in the long-term service process at a certain temperature, wherein the change relation is as follows:
H irr＝(M(t0)-M(t))/M(t0) represents the demagnetizing amount of the permanent magnet;
According to the specific requirements of experiments, when the permanent magnet works in a certain temperature environment, the temperature of the permanent magnet is generally raised to a certain temperature and then kept for 3 to 5 minutes in order to ensure that the magnet is heated uniformly; meanwhile, the root formula is derived based on the theory of magnetic viscosity, and is determined by calculating the proportion of the magnetization state of a micro-area in a magnet, namely the proportion of forward and reverse magnetic domains, when the demagnetizing quantity h irr reaches 100%, the proportion of the forward and reverse magnetic domains is 50%, so that the whole right side of an equal sign of the formula (8) is divided by 2, and the time variable t needs to be added with the initial time t 0 to ensure that the demagnetizing quantity h irr of the permanent magnet is consistent with the proportion of the micro-area magnet of the permanent magnet, and finally, the mathematical model of the demagnetizing quantity h irr of the permanent magnet and the time is expressed as follows:
In a specific implementation, the thermal activation field H f is directly obtained by measuring coercive force at different sweeping speeds at a temperature T, and a specific formula is as follows:
Wherein η and η ref represent respectively different measurement rates; h c (η) and H c(ηref represent coercive forces at different measurement rates, respectively.
The process and effect of the method of the present invention will be described in detail below with specific examples, in which Sm 2Co17 type permanent magnet material applied at a high temperature of 500 c and having a size of 4×3×0.8mm 3 was taken as an experimental verification sample, and residual magnetism, coercive force and magnetic energy products at room temperature and high temperature of 500 c were 9.25kGs, 23.89kOe and 21.29MGOe, and 6.92kGs, 8.22kOe and 11.32MGOe, respectively. FIG. 1 is a schematic diagram showing the change of remanence of permanent magnet in 500 ℃ in the temperature environment continuously in the example of the invention, through the following formula
Changing the change of the residual magnetism of the magnet along with time into the change of the demagnetizing quantity along with time, and fitting the data, wherein the change of the demagnetizing quantity of the permanent magnet along with time is shown in fig. 2, and a mathematical equation after the data fitting is as follows:
hirr＝0.027ln(t+223.11)-0.146 (12)
Then respectively measuring hysteresis loops of the experimental magnet under different field sweeping rates, as shown in fig. 3, which is a schematic diagram of hysteresis loops of a magnet sample at 500 ℃ measured at different rates according to the embodiment of the invention, respectively selecting two groups of data of magnet coercivity of 8.30kOe when the field sweeping rate is 50Oe/s and magnet coercivity of 8.37kOe when the field sweeping rate is 200Oe/s, and calculating a thermal activation field H f of 0.05kOe of the magnet according to a formula (10); at the same time the shape factor of the experimental magnet 0.135, And the initial remanence M (t 0) is 6.92kGs.
The data are carried into a formula (9) to obtain a change relation of the demagnetizing quantity of the experimental magnet, which is used for a long time in a temperature environment of 500 ℃, along with time, as follows:
hirr＝0.026ln(t+180)-0.135 (13)
Then, drawing an experimental fitting curve and a theoretical calculation curve of the experimental magnet in coordinate axes respectively, wherein as shown in fig. 4, a curve diagram represented by an experimental fitting formula and a theoretical derivation formula in the embodiment of the invention is shown, the two curves are more accurate to conform, and the demagnetizing amounts of the experimental fitting of the magnet in 500 ℃ continuous service for 500h, 10000h, 10 years and 20 years are 3.2%, 10.3%, 16.2% and 18.1 respectively; the theoretical deductions are respectively 3.4%, 10.5%, 16.1% and 17.9%, which show that: the change rule of the demagnetizing quantity of the permanent magnet obtained by calculation through the method is accurate and reliable along with time in the service process.
Example 1 commercial SmCo sintered permanent magnet material applied at 350 ℃ purchased on the market was selected, a plurality of cylindrical samples with a size of phi 3 x 3mm were cut out from a large block of permanent magnet by wire cutting, and the demagnetizing amounts after continuous heating for 100h and 500h in the environment of 350 ℃ were about 1.3% and 3.2%, respectively.
The shape factor of the permanent magnet sample of the size is calculated0.31; The residual magnetism of the magnet at 350 ℃ is 9.7kOe through measurement; the coercive force of the magnet at 350 ℃ is measured to be 10.65kOe and 10.86kOe respectively at 50Oe/s and 200Oe/s sweeping field rate, and the thermal activation field H f of the magnet at 350 ℃ is calculated to be 0.15kOe by using a formula (10); initial incubation time t 0 = 180s. Bringing the above parameters into equation (9) yields:
hirr＝0.025ln(t+180)-0.130 (14)
The demagnetizing amounts of the magnet samples of this shape after being continuously heated at 350 ℃ for 100h and 500h were calculated to be about 1.1% and 3.3%, respectively. The theoretical calculation results are basically consistent with the actual experimental measurement results.
Then, the demagnetizing amount of the commercial SmCo sintered permanent magnet material after being in service for 10 years in the environment of 350 ℃ for a long time can be estimated to be about 15.5% by the formula (14).
Example 2, selecting self-made Sm 2Co17 sintered permanent magnet material applied at high temperature of 550 ℃, cutting a large permanent magnet into a plurality of cylindrical samples with the size of phi 3 multiplied by 3mm by using a wire, and continuously heating for 100h and 500h in a 500 ℃ environment, wherein the residual magnetic losses of the cylindrical samples are about 1.7% and 4.2%, respectively.
The shape factor of the permanent magnet sample of the size is calculated0.31; The residual magnetism of the magnet at 500 ℃ is 7.33kOe through measurement; the coercive force of the magnet at 350 ℃ is measured to be 8.49kOe and 8.67kOe respectively at 50Oe/s and 200Oe/s, and the heat activation field H f of the magnet at 500 ℃ is calculated to be 0.13kOe by using a formula (10); initial incubation time t 0 = 180s. Bringing the above parameters into equation (9) yields:
hirr＝0.029ln(t+180)-0.148 (15)
The residual magnetic losses after continuous heating of the shaped magnet sample at 500 ℃ for 100h and 500h were calculated by equation (15) to be about 1.5% and 4.1%, respectively. The theoretical calculation results are basically consistent with the actual experimental measurement results.
In summary, according to the method provided by the embodiment of the invention, through simple data parameter measurement, the performance change condition of the magnet in a certain temperature environment can be accurately predicted directly according to the established mathematical model, so that the time of the application experiment of the permanent magnet with a new component (corresponding reliability experiment is carried out on materials required before the application of the materials in the middle-high end technical field, and the stability of the long-term service of the materials is ensured), and accurate and reliable data support is provided for the application of the permanent magnet in the middle-high end technical field of the quick application of the magnet.
It is noted that what is not described in detail in the embodiments of the present invention belongs to the prior art known to those skilled in the art.
The foregoing is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions easily contemplated by those skilled in the art within the scope of the present invention should be included in the scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.
Claims (3)
1. A method of predicting service performance of a permanent magnet, the method comprising:
The magnetic property change condition of the permanent magnet in the long-term service process is predicted by establishing a mathematical model of the demagnetizing quantity h irr and time of the permanent magnet, wherein the established mathematical model specifically comprises the following steps:
wherein H f represents a thermal activation field of the permanent magnet at a certain temperature T; Representing the form factor of the permanent magnet device; m (t 0) represents the magnetization of the permanent magnet at the initial time t 0; t 0 is the initial time; t is the time to be predicted;
By using the formula, the thermal activation field H f of the permanent magnet to be predicted at a certain temperature T, the magnetization M (T 0) at the initial time T 0 and the shape factor of the permanent magnet device to be predicted are measured and calculated The magnetic property change condition of the permanent magnet to be predicted at the time t to be predicted can be accurately predicted.
2. The method for predicting service performance of a permanent magnet according to claim 1, wherein the establishing process of the mathematical model specifically comprises:
Firstly, according to the basic principle of the magnetic viscosity theory, in the service process of the permanent magnet, the magnetization intensity of the permanent magnet is in a linear change relation with the logarithm of time, namely:
M(t)＝M(t0)-Sln(t/t0) (1)
wherein M (t 0) and M (t) respectively represent the magnetization of the permanent magnet at the initial time t 0 and the magnetization at the time t; s represents the magnetic viscosity coefficient of the permanent magnet, expressed as:
wherein k B represents a boltzmann constant; t represents the temperature of the service environment of the permanent magnet; Representing the density of the energy barrier created by the coercive field; Representing irreversible magnetic susceptibility, M representing the magnetization of the permanent magnet; h represents the coercive field of the permanent magnet;
The mathematical expression of the energy barrier E a is:
Wherein K 1 represents the anisotropy constant of the permanent magnet in the service temperature environment; v 0 represents the thermally activated volume of the permanent magnet in service; h 0 represents the anisotropy field of the permanent magnet in the service environment;
According to the linear change rule of the magnetic viscosity theory, the index m=1 in the formula (3);
H 0＝2K1/μ0Ms, according to the theoretical derivation process, constant 2 in the anisotropy field H 0 is incorporated as a non-significant parameter into the variable parameter, whereby it is possible to obtain according to formula (3):
Wherein μ0 represents vacuum permeability; ms represents the saturation magnetization of the magnet;
Further, as the permanent magnet is used as a main magnetic field source in the service process, the influence of the weak magnetic field of the external environment on the permanent magnet is negligible, and the permanent magnet is mainly influenced by the demagnetizing field H d, namely:
Wherein, Representing the form factor of the permanent magnet device;
The irreversible susceptibility χ irr of the permanent magnet is expressed as:
and then the formulas (2), (4) and (6) are brought into the formula (1), so that the change relation of the magnetization intensity of the permanent magnet along with time is obtained:
In formula (7), k BT/μ0MsV0 represents the thermal activation field H f of the permanent magnet at a certain temperature T;
And then processing the formula (7), and dividing the two sides by the magnetization intensity M (t 0) of the permanent magnet at the initial time t 0 at the same time to obtain the change relation of the demagnetizing quantity of the permanent magnet along with time in the long-term service process at a certain temperature, wherein the change relation is as follows:
H irr＝(M(t0)-M(t))/M(t0) represents the demagnetizing amount of the permanent magnet;
dividing the whole right side of the equal sign of the formula (8) by 2, and adding an initial time t 0 to a time variable t to ensure that the demagnetizing quantity h irr of the permanent magnet is consistent with the proportion of the permanent magnet micro-area magnet, wherein a mathematical model of the demagnetizing quantity h irr of the permanent magnet and the time is finally obtained and is expressed as:
3. the method for predicting the service performance of a permanent magnet according to claim 1, wherein the thermal activation field H f is directly calculated by measuring coercive force at different field speeds at a temperature T, and the specific formula is:
Wherein η and η ref represent respectively different measurement rates; h c (η) and H c(ηref represent coercive forces at different measurement rates, respectively.
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| CN111625983A (en) * | 2020-05-30 | 2020-09-04 | 哈尔滨工业大学 | Finite element simulation method containing nonlinear permanent magnet electromagnetic mechanism based on hysteresis model |
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| CN111625983A (en) * | 2020-05-30 | 2020-09-04 | 哈尔滨工业大学 | Finite element simulation method containing nonlinear permanent magnet electromagnetic mechanism based on hysteresis model |
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