CN112631420B - Virtual experiment teaching system for uniaxial tension magnetic memory nondestructive testing experiment and operation mode thereof - Google Patents
Virtual experiment teaching system for uniaxial tension magnetic memory nondestructive testing experiment and operation mode thereof Download PDFInfo
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
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- G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
- G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
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- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
- G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
- G06F3/011—Arrangements for interaction with the human body, e.g. for user immersion in virtual reality
- G06F3/014—Hand-worn input/output arrangements, e.g. data gloves
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- G06Q—INFORMATION AND COMMUNICATION TECHNOLOGY [ICT] SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES; SYSTEMS OR METHODS SPECIALLY ADAPTED FOR ADMINISTRATIVE, COMMERCIAL, FINANCIAL, MANAGERIAL OR SUPERVISORY PURPOSES, NOT OTHERWISE PROVIDED FOR
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- G09B5/00—Electrically-operated educational appliances
- G09B5/06—Electrically-operated educational appliances with both visual and audible presentation of the material to be studied
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Abstract
The virtual experiment teaching system for the uniaxial tension magnetic memory nondestructive testing experiment and the operation mode thereof comprise a computer platform, VR glasses and gloves; VR glasses pass through the wire and are connected with the computer platform, and earphone one end is connected to the side of VR glasses, and gloves one end passes through the wire and is connected with the computer platform. Based on the force magnetic coupling and magnetostatic analysis theoretical model analysis, the invention develops the virtual machine for the tensile test and the virtual operation display system for the magnetic memory nondestructive testing, generates the live-action operation environment of the virtual machine for the tensile test and the virtual operation display system for the magnetic memory nondestructive testing through the computer platform and the VR glasses, enables students to directly learn the experiment operation from the virtual experiment teaching, summarizes the experiment rules, and achieves the purpose of culturing the experiment capacity of the students in the virtual live-action.
Description
Technical Field
The invention relates to the field of virtual VR development of nondestructive testing technology, and aims at developing a virtual experiment teaching system for a uniaxial tensile experiment in magnetic memory nondestructive testing.
Background
With the continuous development of the nondestructive testing career in China, the teaching of nondestructive testing experiments such as a magnetic memory method and the like gradually enters the classroom, and corresponding professional experimental instruments and equipment are indispensable to the development of teaching and scientific research in colleges and universities. The purchase cost of professional experimental instruments and equipment is high, the requirement for students to participate in the experiment is large, and the management experience of the professional experimental equipment is lack, so that the smooth development of related experimental teaching is restricted.
The magnetic memory detection method is an emerging nondestructive detection method and is considered as a nondestructive detection method for detecting early damage of ferromagnetic materials. The magnetic memory method relates to the problems of a force magnetic coupling mechanism of a ferromagnetic material, a magnetic memory signal rule caused by stress concentration and defects, signal-based defect quantitative determination and the like. Studies have shown that magnetic memory signals near defects or stress concentrations have significant nonlinear characteristics. The tangential component Hx has a maximum near the location of the stress concentration or defect region, and the normal component Hy is generally equal to zero. Therefore, the location of the maximum of the tangential component Hx and the zero-valued characteristic of the normal component Hy can be used to determine the location of the stress concentration or defect region. Further based on the characteristic information of the magnetic memory signal, the degree of stress concentration or defect size information at the position can be determined.
At present, virtual teaching of material stretching simple mechanical experiments can be developed by means of a material stress-strain theory, research and development of a magnetic memory nondestructive testing virtual experiment teaching system can be completed only by deeply combining professional theories such as force magnetic coupling and magnetostatic analysis of ferromagnetic materials, and the teaching requirement on engineering structure safety assessment is met.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide a virtual experiment teaching system for a uniaxial tension magnetic memory nondestructive testing experiment and an operation mode thereof, a tension test virtual machine and a magnetic memory nondestructive testing virtual operation display system are developed on the basis of force magnetic coupling and magnetostatic analysis theoretical model analysis, a live-action operation environment of the tension test virtual machine and the magnetic memory nondestructive testing virtual operation display system is generated through a computer platform and VR glasses, students can directly learn from virtual experiment teaching to experiment operation, experiment rules are summarized, and the aim of culturing the experiment capacity of the students in a virtual live-action is fulfilled.
In order to achieve the purpose, the invention adopts the technical scheme that:
the virtual experiment teaching system for the uniaxial tension magnetic memory nondestructive testing experiment comprises a computer platform 1, VR glasses 2 and gloves 3;
A tensile test virtual machine, a magnetic memory nondestructive testing virtual operation display system 5 and a virtual magnetic memory signal real-time calculation program 6 on the surface of a ferromagnetic material are configured in the computer platform 1;
the computer platform 1 is used for providing experimental data analysis in a tensile test and virtual magnetic memory signal real-time analysis of the surface of the ferromagnetic material in magnetic memory nondestructive testing;
the VR glasses 2 are used for providing a real-time virtual operation interface, the gloves 3 are combined with the VR glasses 2 to restore hand movement in the virtual experiment operation interface, and the earphones 4 play operation information in the experiment process to operators;
the virtual machine for the tensile test and the virtual operation display system 5 for the magnetic memory nondestructive testing are used for providing a virtual tensile test of materials and a virtual magnetic memory testing test of ferromagnetic materials.
The tensile test virtual machine and the magnetic memory nondestructive testing virtual operation display system 5 comprise a virtual magnetic memory detection system, the virtual magnetic memory detection system comprises a tested sample 7, a detection probe 8, a virtual magnetic memory signal detector 9 and a virtual real-time display device 10, one end of the detection probe 8 is connected to one end of the virtual magnetic memory signal detector 9, the other end of the virtual magnetic memory signal detector 9 is connected to one end of the virtual real-time display device 10, and the detection probe 8 is used for detecting the tested sample 7.
The virtual operation display system 5 for the tensile test virtual machine and the magnetic memory nondestructive testing comprises a real-time calculation program 6 for virtual magnetic memory signals of the surface of the ferromagnetic material, which is provided based on a force magnetic coupling constitutive theory and a magnetic memory micro magnetic signal calculation model; and the virtual magnetic memory signal real-time calculation program 6 on the surface of the ferromagnetic material is used for calculating the magnetic memory detection virtual signal measured by the detection probe 8 in real time according to the position of the magnetic memory nondestructive detection probe in the virtual scene.
The real-time virtual magnetic memory signal calculation program 6 on the surface of the ferromagnetic material has the following specific calculation mode:
for the change of the magnetization state of the material along the stretching direction in uniaxial stretching analysis, under the constant magnetic field and isothermal environment, the magnetization intensity of the isotropic ferromagnetic material changes under the action of external load, and under the equilibrium state of the force magnetic effect, the magnetization state of the ferromagnetic material is expressed as
In the formula: m is a group of an For non-hysteresis magnetization, M s Is the saturation magnetization of the material, H total Is equivalent field strength, a is a magnetization model parameter with the unit of A/m;
effective field H of ferromagnetic material under combined action of external force and magnetic field total Expressed as the sum of the ambient magnetic field, the demagnetizing field and the stress-equivalent field, i.e.
H total ＝H+αM+H σ (B)
In the formula: h is an external magnetic field, α M is an equivalent field reflecting the interaction between magnetic domains, H σ The stress equivalent field induced by an external load, M is the magnetization intensity;
the magnetostriction of ferromagnetic materials is an even function of the material, said magnetostriction of ferromagnetic materials being expressed as
In the formula: Δ M = | M | -M 0 ，ΔM s ＝M s -M 0 λ is magnetostrictive strain, σ is stress, σ s For yield stress, beta characterizes the strength of the stress magnetization effect, lambda s For saturation of magnetostrictive strain, M 0 Is the stress-dependent saturation wall-shift magnetization, M ws The saturation wall displacement magnetization intensity under the stress-free condition, k is the ratio of the magnetostrictive strain reduction section to the saturation magnetostriction quantity, and theta is a jump function;
the magnetoelastic equivalent field can be expressed as the differential of the magnetoelastic energy density function with respect to the magnetization, i.e.
Wherein mu 0 Is a vacuum magnetic permeability.
When M is less than 0.2M s When the expression between the magnetization and the effective magnetic field is simplified using the linear part of the langevin function, formula (a) can be simplified to
M＝M s H total /(3a) (E)
The error introduced by the use of the linear part of the langevin function does not exceed 2.5%, noting that M of equation (E) and the ideal non-hysteretic magnetization M solve for the ideal non-hysteretic magnetization an In agreement, by solving equations (D) and (E), the relationship between the ideal non-hysteretic magnetization and the applied environmental magnetic field, stress is:
solving by a formula (F) to obtain the ideal non-hysteresis magnetization M of the ferromagnetic bar an Is composed of
Formula (G) is an analytic expression of non-hysteresis magnetization, and when the magnitude of an external magnetic field and the stress state of a material are known, the expression is used for directly obtaining the theoretical value of the non-hysteresis magnetization of the ferromagnetic material;
in combination with the principle of proximity during stress magnetization, there is the following differential of magnetization M
Expression formula
Wherein, the parameter eta considers the influence of irreversible change caused by stress magnetization in a low magnetic field, ξ is the energy density correlation coefficient, E is Young modulus, and c describes the flexibility of a magnetic domain wall;
to this end, under the action of a constant weak magnetic field, the equations (G) and (H) together constitute the relationship between the magnetization of the ferromagnetic material and the applied magnetic field and stress.
The virtual magnetic memory signal real-time calculation program 6 of the ferromagnetic material surface establishes a virtual signal real-time calculation program of the magnetic signal vertical component of the test piece surface;
based on an elastic mechanical stress-strain relation, calculating the stress state of a rectangular test piece under uniaxial tension according to the condition that sigma is the stress state of the test piece, F is the force applied to two ends of the test piece, S is the cross section area of the test piece, establishing a calculation model of a magnetic memory signal on the surface of the test piece based on a magnetic charge theory, and reproducing the three-dimensional micro-magnetic signal distribution on the surface of the test piece;
the length, width and depth of a rectangular test piece are respectively 2L,2a and d, the direction of a magnetic field is defined as the positive direction of an x coordinate axis, a coordinate system as shown in the figure is established, after the test piece is subjected to uniaxial tension along the y axis direction, magnetic charge aggregation can be generated on ABFE and CDHG of the test piece, so that micro-magnetic signals are generated on the surface of the test piece, and components of the micro-magnetic signals along the x, y and z directions at the space (x, y and z) positions can be respectively represented
Wherein m (u) is a magnetic charge density, which is equal to the magnetization of the material surface, and is obtained by the formulas (G) and (H);
in the virtual experiment operation process, the virtual real-time signal of the virtual magnetic signal detection probe needs to be determined through the position information of the glove.
The specific calculation steps of the virtual real-time signal are as follows:
calculating the real-time position and the probe angle in the virtual space when the probe moves in real time according to the data of the sensor on the glove 3, wherein alpha 1 ,α 2 ,α 3 The included angles between the axial direction of the micro-magnetic probe and three coordinate axes of x, y and z are respectively set;
calculating in real time according to a formula (J) to obtain a three-dimensional component of the virtual magnetic signal, firstly calculating according to a formula (I) to obtain the three-dimensional component of the virtual magnetic signal at the position according to the position of the probe in a virtual space, then calculating according to the angle information of the probe to obtain a magnetic field component of the virtual three-dimensional magnetic signal at the point along the axial direction of the micro-magnetic probe, wherein the expression of the magnetic field component along the axial direction of the micro-magnetic probe is
H p ＝H x cos(α 1 )+H y cos(α 2 )+H z cos(α 3 ) (J)
And the micro-magnetic signals corresponding to the virtual probe in the moving process are calculated in real time.
The specific operation modes of the virtual experiment teaching system for the uniaxial tension magnetic memory nondestructive testing experiment comprise a virtual teaching mode and a scientific research simulation mode;
the first operation mode is a virtual teaching mode, and the specific execution operation steps are divided into three steps;
step one, experiment preparation work: an operator wears VR glasses 2 and gloves 3 to enter a virtual experiment operation window, a virtual machine for a tensile test and a virtual operation display system 5 for magnetic memory nondestructive testing are configured in a computer platform 1 to generate a scene of an actual experiment operation environment, and the scene is imaged in the VR glasses 2; an operator formulates an experimental scheme in a virtual interface displayed by VR glasses, the operator operates according to an experimental operation instruction prompted by a computer platform, and the instruction is synchronously played to students for listening through earphones 4 connected with the VR glasses 2 to guide the students to complete experimental operation; selecting a virtual component preparation option, and selecting the size of the virtual component according to the component size formulated in the experimental scheme to generate the virtual component;
step two, developing a virtual stretching experiment: starting to carry out virtual simulation live-action experiment operation according to the stretching experiment operation steps prompted by the computer platform; the method comprises the following steps of preparing a test piece, starting a tensile testing machine, adjusting the parallelism of an upper chuck and a lower chuck by using a spare part, avoiding the test piece from being subjected to torsion and load, installing the test piece to the testing machine, adjusting the position of a cross beam clamped in a clamp, adjusting the position of the cross beam by using a manual control box, adjusting the test piece to the position which can be correctly clamped by the lower clamp, ensuring that the test piece is vertically downward, eliminating clamping force and the like; starting the testing machine to perform a tensile test, clamping in a fixed direction every time of loading, gradually loading the test sample, and unloading after a preset load is reached; finally, taking the test piece down from the testing machine, closing the virtual testing machine, and then cutting off the virtual main power supply and other operations;
step three, developing a magnetic memory virtual detection experiment:
according to the computer operation prompt, when magnetic signal detection is carried out, an operator needs to be far away from other ferromagnetic components, and the operator places the sample 7 to be tested according to the same detection direction and position; an operator wears the data glove 3 to hold the virtual probe to detect the magnetic memory signal of the surface of the sample along the detection track 11, and at the moment, the operator needs to pay attention to the operation according to the information such as the optimized detection step distance, the lifting height, the detection probe perpendicular to the surface of the sample and the like prompted by a computer; finally, the detection signal is automatically transmitted to a virtual magnetic signal detector 9, in the measurement process, magnetic field data is automatically led into the computer platform 1, and the magnetic memory signal distribution result of the surface of the test piece is output on a computer in real time; after the virtual experiment is finished, the operator closes the magnetic signal virtual real-time display device 10 and the virtual magnetic memory signal detector 9, and places the virtual probe 8; after the experiment, the operator removes the VR glasses 2 and the gloves 3 and places the glasses at the designated position.
The second operation mode is a scientific research simulation mode; the mode operation is specifically as follows:
an operator wears the VR glasses 2 and the gloves 3, selects a scientific research simulation mode in the virtual interface, closes operation information prompted by the computer platform, and enters an experiment operation window; the operator starts independent operation to carry out the experiment; after the experiment operation is finished, the operator stores virtual experiment data, and the computer platform carries out general evaluation on the experiment; the operation is correct, and the experiment is finished, and the operating personnel take off VR glasses 2 and gloves 3 to place the assigned position. And providing a self-operation review function, if the operation is judged to have errors, reviewing the experimental operation process on the VR glasses 2, judging the step that the experimental operation has errors, and adjusting the corresponding experimental operation.
The invention has the beneficial effects that:
the technical scheme adopted by the invention is that a real-scene experiment operation environment scene is generated through a tension test virtual machine and a magnetic memory nondestructive testing virtual operation display system which are configured in a computer platform, so that a real experiment scene is restored for students. The schematic diagram of the operation principle of the magnetic memory nondestructive testing virtual operation display system is shown in fig. 5.
The virtual experiment teaching system and the operation mode thereof for the uniaxial tension magnetic memory nondestructive testing experiment provide two operation modes, namely a virtual teaching mode and a scientific research simulation mode. An operator can select one of the virtual experiment modes according to the requirement of the operator, and the teaching training and scientific research simulation are facilitated.
The virtual experiment teaching system and the operation mode thereof for the uniaxial tension magnetic memory nondestructive testing experiment are based on a virtual magnetic memory signal real-time calculation program on the surface of a ferromagnetic material developed in the invention, can realize the reduction of magnetic signal detection under the actual experiment operation condition and the measurement of magnetic signals on the surface of a test piece under the action of different stress load amplitudes and under different test piece sizes, and are convenient for students to know the basic experiment phenomenon and the formation mechanism of the magnetic memory detection method.
Drawings
FIG. 1 is a schematic view of a virtual experiment teaching system for uniaxial tension magnetic memory nondestructive testing.
Fig. 2 is a schematic view of the structure of the test piece.
FIG. 3 is a flow chart of operation of the virtual teaching simulation experiment for uniaxial tension magnetic memory nondestructive testing.
FIG. 4 is a schematic diagram of a magnetic memory detection system in a magnetic memory nondestructive testing virtual teaching simulation experiment system.
FIG. 5 is a schematic diagram of the operation principle of the magnetic memory nondestructive testing virtual operation display system.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
As shown in fig. 1-5, the virtual teaching simulation experiment system for uniaxial tension magnetic memory nondestructive testing comprises a computer platform 1, VR glasses 2 and gloves 3, wherein the VR glasses 2 are connected with the computer platform 1 through a conducting wire, earphones 4 are connected to the side edges of the VR glasses 2, and the gloves 3 are connected with the computer platform 1 through a conducting wire. In the virtual teaching simulation experiment system, a tensile test virtual machine, a magnetic memory nondestructive testing virtual operation display system 5 and a virtual magnetic memory signal real-time calculation program 6 on the surface of a ferromagnetic material are configured in a computer platform 1.
The virtual experiment teaching system for the uniaxial tension magnetic memory nondestructive testing experiment provides two operation modes, the first operation mode is a virtual teaching mode, and the mode is convenient for students to know the operation steps and basic experiment phenomena of the magnetic memory nondestructive testing experiment through virtual experiment operation. In the virtual teaching mode, the specific operation steps of the student or the operator are as follows:
step 1: an operator wears VR glasses 2 and gloves 3, selects a virtual teaching mode in a virtual interface, and enters an experiment operation window.
Step 2: a tensile test virtual machine and a magnetic memory nondestructive testing virtual operation display system 5 which are arranged in the computer platform 1 generate a live-action experiment operation environment scene and form images in the VR glasses 2.
And step 3: and (4) making an experimental scheme in a virtual interface displayed by VR glasses. The operating personnel operates according to the experiment operation instruction prompted by the computer platform, and the instruction is synchronously played for students to listen through the earphones (4) connected with the VR glasses 2 so as to better restore the real experiment scene.
And 4, step 4: selecting a virtual component preparation option, and selecting the size of the virtual component according to the component size formulated in the experimental scheme to generate the virtual component.
And 5: starting to carry out virtual simulation live-action experiment operation according to the stretching experiment operation steps prompted by the computer platform; the method comprises the following steps of preparing a test piece, starting a tensile testing machine, adjusting the parallelism of an upper chuck and a lower chuck by using a spare part, avoiding torsion and load of the test piece, installing the test piece to the testing machine, adjusting the position of a cross beam in a clamp by clamping the test piece, adjusting the position of the cross beam by using a manual control box, adjusting the test piece to the position which can be correctly clamped by the lower clamp, and ensuring that the test piece is vertically downward.
Step 6: and (3) starting the virtual testing machine by an operator to perform a tensile test, and clamping in a fixed direction during each loading. And (4) loading the sample step by step, and unloading the sample after the preset load is reached.
And 7: finally, the test piece is removed from the testing machine. And closing the virtual testing machine, and cutting off the main power supply and the like.
And 8: according to the computer operation prompt, when the magnetic signal is detected, the operator should move away from other ferromagnetic members, and the sample 7 to be tested is placed in the same detection direction and position.
And step 9: an operator holds the virtual probe by wearing a data glove and detects a magnetic memory signal of the surface of the sample along a detection track 11, wherein the signal is a result output based on a virtual magnetic memory signal real-time calculation program 6 of the surface of the ferromagnetic material configured on a computer platform 1 in the system. At this time, attention should be paid to the operation according to the information of optimizing the detection step distance, the lifting height, the detection probe vertical to the surface of the test piece and the like prompted by a computer.
Step 10: the detection signal is automatically transmitted to the virtual magnetic signal detector 9, the magnetic field data is automatically guided into the computer 1 in the measurement process, the magnetic memory signal distribution result of the surface of the test piece is output on the computer in real time, and the operator records the result.
Step 11: and (5) closing the virtual real-time display equipment and the virtual magnetic memory signal detector by an operator after the virtual experiment is finished, and placing the virtual probe.
Step 12: after the experiment, the operator removes the gloves and the VR glasses and places the gloves and VR glasses at the designated position.
The second mode of operation is a scientific simulation mode. This mode is used for satisfying scientific research personnel's autonomic experiment demand, and in scientific research simulation mode, operating personnel can break away from computer platform's operation suggestion according to the scientific research purpose of oneself, accomplishes the experiment alone, and this mode can help scientific research personnel to accomplish autonomic innovation experiment, the training of better supplementary scientific research personnel's experimental study. In the scientific research simulation mode, the specific operation steps of students or operators are as follows:
step 1: an operator wears the VR glasses 2 and the gloves 3, selects a scientific research simulation mode in the virtual interface, closes operation information prompted by the computer platform, and enters an experiment operation window.
And 2, step: the operator starts to operate independently to complete the whole experimental process.
And step 3: and after the experiment operation is finished, the operator stores the virtual experiment data, and the computer platform evaluates the experiment.
And 4, step 4: the operation is correct, and the experiment is ended, and operating personnel takes off gloves and VR glasses to place the assigned position. And providing a self-operation review function, if the operation is judged to have errors, reviewing the performed experimental operation process on VR glasses, judging the step that the experimental operation has errors, and adjusting the corresponding experimental operation.
Claims (7)
1. The virtual experiment teaching system for the uniaxial tension magnetic memory nondestructive testing experiment is characterized by comprising a computer platform (1), VR glasses (2) and gloves (3);
the VR glasses (2) are connected with the computer platform (1) through a lead, the side edges of the VR glasses (2) are connected with one end of an earphone (4), and one end of the glove (3) is connected with the computer platform (1) through a lead;
the virtual operation display system (5) for the tensile test virtual machine and the magnetic memory nondestructive testing comprises a real-time calculation program (6) for virtual magnetic memory signals on the surface of the ferromagnetic material, which is provided based on a force-magnetic coupling constitutive theory and a magnetic memory micro-magnetic signal calculation model; the virtual magnetic memory signal real-time calculation program (6) on the surface of the ferromagnetic material is used for calculating the magnetic memory detection virtual signal measured by the detection probe (8) in real time according to the position of the magnetic memory nondestructive detection probe in the virtual scene;
the real-time virtual magnetic memory signal calculation program (6) on the surface of the ferromagnetic material is specifically calculated in the following way:
for the change of the magnetization state of the material along the stretching direction in uniaxial stretching analysis, under the constant magnetic field and isothermal environment, the magnetization intensity of the isotropic ferromagnetic material changes under the action of external load, and under the equilibrium state of the force magnetic effect, the magnetization state of the ferromagnetic material is expressed as
In the formula: m an For non-hysteresis magnetization, M s Is the saturation magnetization of the material, H total Is equivalent field strength, a is a magnetization model parameter with the unit of A/m;
effective field H of ferromagnetic material under combined action of external force and magnetic field total Expressed as the sum of the ambient magnetic field, the demagnetizing field and the stress-equivalent field, i.e.
H total ＝H+αM+H σ (B)
In the formula: h is an external magnetic field, alpha M is an equivalent field reflecting the interaction between magnetic domains, H σ The stress equivalent field induced by external load, M is magnetization intensity;
the magnetostriction of ferromagnetic materials is an even function of the material, said magnetostriction of ferromagnetic materials being expressed as
In the formula: Δ M = | M | -M 0 ，ΔM s ＝M s -M 0 λ is magnetostrictive strain, σ is stress, σ s For yield stress, beta characterizes the strength of the stress magnetization effect, lambda s To saturate the magnetostrictive strain, M 0 Is the stress-dependent saturation wall-shift magnetization, M ws The saturation wall displacement magnetization intensity under the stress-free condition, k is the ratio of a magnetostrictive strain reduction section to the saturation magnetostrictive amount, and theta is a hopping function;
the magnetoelastic equivalent field can be expressed as the differential of the magnetoelastic energy density function with respect to the magnetization, i.e.
Wherein mu 0 Is a vacuum magnetic permeability.
2. The virtual experiment teaching system for uniaxial tension magnetic memory nondestructive testing experiment according to claim 1, characterized in that a virtual machine for tension test and a virtual operation and display system (5) for magnetic memory nondestructive testing and a virtual magnetic memory signal real-time calculation program (6) for ferromagnetic material surface are configured in the computer platform (1);
the computer platform (1) is used for providing experimental data analysis in a tensile test and virtual magnetic memory signal real-time analysis of the surface of the ferromagnetic material in magnetic memory nondestructive testing;
the VR glasses (2) are used for providing a real-time virtual operation interface, the gloves (3) are combined with the VR glasses (2) to restore hand motions in the virtual experiment operation interface, and the earphones (4) play operation information in the experiment process to operators;
the tensile test virtual machine and the magnetic memory nondestructive testing virtual operation display system (5) are used for providing virtual tensile tests of materials and virtual magnetic memory testing tests of ferromagnetic materials.
3. The virtual experiment teaching system for the uniaxial tension magnetic memory nondestructive testing experiment according to claim 1, wherein the tension test virtual machine and the magnetic memory nondestructive testing virtual operation display system (5) comprise a virtual magnetic memory detection system, the virtual magnetic memory detection system comprises a tested sample (7), a detection probe (8), a virtual magnetic memory signal detector (9) and a virtual real-time display device (10), one end of the detection probe (8) is connected to one end of the virtual magnetic memory signal detector (9), the other end of the virtual magnetic memory signal detector (9) is connected to one end of the virtual real-time display device (10), and the detection probe (8) is used for detecting the tested sample (7).
4. The virtual experiment teaching system for uniaxial tension magnetic memory nondestructive testing experiments according to claim 1, wherein when M < 0.2M s When the expression between the magnetization and the effective magnetic field is simplified using the linear part of the langevin function, equation (a) can be simplified to
M＝M s H total /(3a) (E)
The error introduced by the use of the linear part of the langevin function does not exceed 2.5%, it is noted that the solution to the ideal non-hysteretic magnet is obtainedWhen the magnetization is changed, M of the formula (E) and the ideal non-hysteresis magnetization M an In agreement, by solving equations (D) and (E), the relationship between the ideal non-hysteretic magnetization and the applied ambient magnetic field, stress is:
solving by a formula (F) to obtain the ideal non-hysteresis magnetization M of the ferromagnetic bar an Is composed of
Formula (G) is an analytic expression of non-hysteresis magnetization, and when the magnitude of an external magnetic field and the stress state of a material are known, the expression is used for directly obtaining the theoretical value of the non-hysteresis magnetization of the ferromagnetic material;
in combination with the principle of proximity during stress magnetization, there is the following differential expression of magnetization M
Wherein, the parameter eta considers the influence of irreversible change caused by stress magnetization in a low magnetic field, ξ is the energy density correlation coefficient, E is Young modulus, and c describes the flexibility of a magnetic domain wall;
thus, under the action of a constant weak magnetic field, the equations (G) and (H) jointly form the relationship between the magnetization of the ferromagnetic material and the applied magnetic field and stress.
5. The virtual experiment teaching system for the uniaxial tension magnetic memory nondestructive testing experiment according to claim 1, characterized in that the virtual magnetic memory signal real-time calculation program (6) of the surface of the ferromagnetic material establishes a virtual signal real-time calculation program of the vertical component of the magnetic signal of the surface of the test piece;
based on an elastic mechanical stress-strain relation, calculating the stress state of a rectangular test piece under uniaxial tension according to the condition that sigma = F/S, wherein sigma is the stress state of the test piece, F is the force applied to two ends of the test piece, S is the cross section area of the test piece, establishing a calculation model of a magnetic memory signal on the surface of the test piece based on a magnetic load theory, and reproducing the three-dimensional micro-magnetic signal distribution on the surface of the test piece;
the length, width and depth of a rectangular test piece are respectively 2L,2a and d, the direction of a magnetic field is defined as the positive direction of an x coordinate axis, a coordinate system is established, after the test piece is subjected to uniaxial tension along the y axis direction, magnetic charge aggregation can be generated on ABFE and CDHG of the test piece, so that micro-magnetic signals are generated on the surface of the test piece, and the components of the micro-magnetic signals along the x, y and z directions at the space (x, y and z) positions can respectively represent
Wherein m (u) is a magnetic charge density, which is equal to the magnetization of the surface of the material, and is obtained by the formulas (G) and (H);
in the operation process of the virtual experiment, the virtual real-time signal of the virtual magnetic signal detection probe needs to be determined through the position information of the gloves.
6. The virtual experiment teaching system for uniaxial tension magnetic memory nondestructive testing experiments according to claim 5, wherein the specific calculation steps of the virtual real-time signal are as follows:
calculating the real-time position and probe angle in the virtual space of the probe moving in real time according to the sensor data on the glove (3), wherein alpha 1 ,α 2 ,α 3 The included angles between the axial direction of the micro-magnetic probe and three coordinate axes of x, y and z are respectively set;
calculating in real time according to a formula (J) to obtain a three-dimensional component of the virtual magnetic signal, firstly calculating according to a formula (I) to obtain the three-dimensional component of the virtual magnetic signal at the position according to the position of the probe in a virtual space, then calculating according to the angle information of the probe to obtain a magnetic field component of the virtual three-dimensional magnetic signal at the position along the axial direction of the micro-magnetic probe, wherein the expression of the magnetic field component along the axial direction of the micro-magnetic probe is
H p ＝H x cos(α 1 )+H y cos(α 2 )+H z cos(α 3 ) (J)
And the micro-magnetic signals corresponding to the virtual probe in the moving process are calculated in real time.
7. The specific operation mode of the virtual experiment teaching system based on the uniaxial tension magnetic memory nondestructive testing experiment of claim 1 is characterized by comprising a virtual teaching mode and a scientific research simulation mode;
the first operation mode is a virtual teaching mode, and the specific execution operation steps are divided into three steps;
step one, experiment preparation: an operator wears VR glasses (2) and gloves (3) to enter a virtual experiment operation window, a tension test virtual machine and a magnetic memory nondestructive testing virtual operation display system (5) which are arranged in a computer platform (1) generate a live-action experiment operation environment scene, and the scene is imaged in the VR glasses (2); an operator formulates an experimental scheme in a virtual interface displayed by VR glasses, the operator operates according to an experimental operation instruction prompted by a computer platform, and the instruction is synchronously played to students through earphones (4) connected with the VR glasses (2) to guide the students to complete experimental operation; selecting a virtual component preparation option, and selecting the size of the virtual component according to the component size formulated in the experimental scheme to generate the virtual component;
step two, developing a virtual stretching experiment: starting to carry out virtual simulation live-action experiment operation according to the stretching experiment operation steps prompted by the computer platform; preparing a test piece, starting a tensile testing machine, adjusting the parallelism of an upper chuck and a lower chuck by using a spare part, avoiding torsion and load of the test piece, installing the test piece to the testing machine, adjusting the position of a cross beam clamped in a clamp, adjusting the position of the cross beam by using a manual control box, adjusting the test piece to the position which can be correctly clamped by the lower clamp, ensuring that the test piece is vertically downward, and eliminating clamping force; starting the testing machine to perform a tensile test, clamping in a fixed direction every time of loading, gradually loading the test sample, and unloading after a preset load is reached; finally, taking the test piece down from the testing machine, closing the virtual testing machine, and then cutting off the virtual main power supply for operation;
step three, developing a magnetic memory virtual detection experiment:
according to the operation prompt of the computer, when the magnetic signal is detected, the operator needs to be far away from other ferromagnetic components, and places the sample to be tested (7) according to the same detection direction and position; an operator holds the virtual probe to detect a magnetic memory signal of the surface of the sample along the detection track (11) by wearing the data glove (3), and at the moment, the operation is carried out according to the optimized detection step distance, the lifting height and the information of the detection probe vertical to the surface of the test piece, which are prompted by a computer; finally, the detection signal is automatically transmitted to a virtual magnetic signal detector (9), in the measurement process, magnetic field data is automatically led into a computer platform (1), and the magnetic memory signal distribution result of the surface of the test piece is output on a computer in real time; after the virtual experiment is finished, the operator closes the magnetic signal virtual real-time display equipment (10) and the virtual magnetic memory signal detector (9), and places the virtual probe (8); after the experiment is finished, the operator takes off the VR glasses (2) and the gloves (3) and places the VR glasses and the gloves at the designated positions;
the second operation mode is a scientific research simulation mode; the mode operation is specifically as follows:
an operator wears VR glasses (2) and gloves (3), selects a scientific research simulation mode in a virtual interface, closes operation information prompted by a computer platform, and enters an experiment operation window; the operator starts independent operation to carry out the experiment; after the experiment operation is finished, the operator stores virtual experiment data, and the computer platform carries out general evaluation on the experiment; the operation is correct, and the experiment is ended, and operating personnel take off VR glasses (2) and gloves (3) to place the assigned position, provide the self-operation and look back the function, if think that the operation has the mistake, can look back the experimental operation process of carrying out on VR glasses (2), judge that the experimental operation has the step of mistake, adjust corresponding experimental operation.
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