A method and device for measuring multi-electrode electromagnetic solid interface performance

Abstract

The present invention discloses a multi-electrode electromagnetic solid interface performance measurement method and device. The resistivity and contact resistance of the sample to be measured are obtained by the current between two anisotropic current sources and the potential difference between two points on the interface, and the resistivity and contact resistance of the sample to be measured are obtained, and the distribution of the normal / tangential stress of the contact surface is obtained by substituting them into the established force-electric contact model, and then the contact surface defects and internal defects corresponding to the stress distribution are obtained; at the same time, the normal stress distribution corresponding to the rough interface is used to obtain the rough interface edge contour curve, and the random number generation seed is obtained by reverse calculation, and then the random number generation seed is fixed in the non-Gaussian numerical simulation process to obtain a uniquely determined interface morphology. The measuring device includes a support frame, a counterweight host, a slide rail, an active pulley and a copper elastic electrode. The present invention obtains the performance, characteristics and load on the electromagnetic solid contact interface by measuring the electrical signal, and realizes the synchronous measurement of the contact interface / internal defects and interface morphology.

Description

Technical Field

[0001] The invention belongs to the technical field of material detection, and in particular relates to a multi-electrode electromagnetic solid interface performance measurement method and device. Background Art

[0002] During the processing and forming of metal materials, various uncertain factors may cause structural defects or internal residual stress, which in turn affects the performance of the material. Therefore, understanding the type of internal damage at the material interface or measuring the interface residual stress is of great significance for the safe use of the material.

[0003] Methods for detecting internal damage on interfaces include fluorescence imaging, automatic optical detection, laser holographic detection, acoustic emission technology, automatic X-ray detection, infrared nondestructive testing, etc. The digital holographic method uses a photoelectric coupling device to record a digital hologram, and then numerically reconstructs it in a computer to obtain the three-dimensional morphology of the object surface. However, this method requires that the contact surface be exposed during detection. The automatic X-ray detection method uses the extremely strong penetrating power of X-rays to detect defects. When the detection interface contains defects such as bubbles, cracks, and slag inclusions, the ability of the defective part to absorb X-rays will be weakened, so the X-ray intensity will be higher than that of the defect-free part after penetrating the defective part; however, this method will produce heating effects on the material during the test, affecting the physical properties of the material.

[0004] The methods for measuring interface residual stress include curvature method, XRD diffraction method, micro-Raman spectroscopy, etc. However, due to the low resolution and small application scale of these measurement methods, their application scope is limited. Among them, the curvature method is a commonly used approximate measurement method, but it is not suitable for larger local stress conditions. The resolution and measurement accuracy of the XRD diffraction method are not enough to meet the measurement requirements of residual stress in multilayer film structures. Micro-Raman spectroscopy is usually used to measure residual stress at the interface of micro-nano-scale thin films, which is difficult to measure on larger-scale materials.

[0005] Existing methods cannot achieve simultaneous measurement of the contact interface / internal defects and morphology of metal materials, are difficult to implement in service environments, have high requirements for test material samples, and have limited application scope due to factors such as insufficient resolution, complex and time-consuming processes, etc. Summary of the invention

[0006] In view of the deficiencies pointed out in the above background technology, the present invention provides a method and device for measuring multi-electrode metal interface properties, aiming to solve the problems existing in the prior art in the above background technology.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] A multi-electrode electromagnetic solid interface performance measurement method, the method comprising the following steps:

[0009] S1, under two opposite current sources A and B, calculate the potential of any two points M and N on the sample interface when the interface is subjected to normal load and tangential force;

[0010] S2. According to the electric potential, the potential difference between M and N is obtained when two opposite-polarity current sources A and B are used as power supply electrodes;

[0011] S3. Calculate the resistivity and contact resistance of the sample to be tested through the potential difference between M and N and the current between A and B;

[0012] S4. Establish a force-electric contact model, the expression is as follows:

[0013]

[0014] In the formula, S real is the true contact area, a is the contact radius, R is the contact resistance, ρ is the material resistivity, T is the tangential force, F is the normal load, σ is the material shear strength, and R 0 is the initial contact resistance, b and k are fitting parameters;

[0015] S5. Substitute the resistivity and contact resistance of the sample to be tested into the force-electric contact model to obtain the distribution of tangential force on the contact interface when subjected to normal load, and the distribution of normal load on the contact interface when subjected to tangential force; thereby obtaining the distribution of normal stress and tangential stress on the contact surface, and then obtaining contact surface defects corresponding to the distribution of normal stress and tangential stress on the contact surface, and internal defects corresponding to the distribution of internal normal stress and tangential stress; at the same time, using the normal stress distribution corresponding to the rough interface in the contact condition of the contact surface and the stress distribution corresponding to the contact surface, as well as the measured rough interface edge contour curve, inversely calculate the random number generation seed, and then fix the random number generation seed during the non-Gaussian numerical simulation to obtain a uniquely determined interface morphology.

[0016] The present invention further provides a multi-electrode electromagnetic solid interface performance measuring device, comprising a supporting frame, a counterweight mainframe, a slide rail, an active pulley and a copper elastic electrode, wherein a slide rail is arranged on the top of the supporting frame, an active pulley is installed on the slide rail, and the active pulley is fixed to the top of the counterweight mainframe, a plurality of electrode adapters are arranged on the counterweight mainframe, a power supply device and an interface performance measuring electrical method instrument are arranged inside the counterweight mainframe, a measuring main line of the interface performance measuring electrical method instrument is connected to a plurality of copper elastic electrodes, the copper elastic electrodes are located at the outer bottom of the counterweight mainframe, the plurality of copper elastic electrodes are arranged along the moving direction of the counterweight mainframe, and the copper elastic electrodes are in contact with the sample to be tested.

[0017] Furthermore, the support frame adopts an automatic telescopic deformation structure, and the length of the slide rail is adjustable.

[0018] Furthermore, the distances between the plurality of electrode adapters are different.

[0019] Furthermore, the copper elastic electrode includes a main body, the top and bottom of the main body are respectively provided with an upper cover and a porous bottom plate, the upper cover is provided with a water injection valve and a copper electrode, the outer end of the copper electrode is connected to a copper clip via a connecting copper wire, the copper clip is connected to an interface performance measuring electrical instrument inside the counterweight host, the inner end of the copper electrode is connected to a copper mesh via a copper wire, the copper mesh is horizontally arranged above the porous bottom plate, and a conductive liquid is provided in the main body.

[0020] Compared with the shortcomings and deficiencies of the prior art, the present invention has the following beneficial effects:

[0021] (1) The measurement method provided by the present invention can synchronously measure the contact interface / internal defects and morphology of metal materials. By measuring the electrical signal of the contact interface and converting the electrical signal into a force signal using a force-electric contact model, the contact surface contact condition and the stress distribution corresponding to the contact surface, the internal defects and the corresponding stress distribution inside, and the interface morphology are obtained. Finally, the synchronous measurement of the contact interface / internal defects and the interface morphology is achieved, so as to achieve the purpose of obtaining the performance, characteristics and load on the electromagnetic solid contact interface by measuring the electrical signal.

[0022] (2) The measurement method of the present invention has low requirements on the flatness of the working surface and will not affect the physical properties of the specimen.

[0023] (3) The measuring device provided by the present invention has a simple structure, can be applied to large-scale devices, has low requirements on the test environment, has a large measurement scale, and has a wide range of applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the current field between two opposite-polarity point current sources on the surface provided by an embodiment of the present invention.

[0025] Figure 2 It is a schematic diagram of the relationship between the fitting parameters and the normal load provided by an embodiment of the present invention.

[0026] Figure 3 It is a schematic diagram of the structure of a multi-electrode electromagnetic solid interface performance measurement device provided in an embodiment of the present invention.

[0027] Figure 4 It is a schematic diagram of the internal structure of the counterweight host provided in an embodiment of the present invention.

[0028] Figure 5 It is a schematic diagram of the structure of a copper elastic electrode provided in an embodiment of the present invention.

[0029] In the figure: 1. support frame, 2. counterweight main unit, 3. slide rail, 4. active pulley, 5. electrode adapter, 6. copper elastic electrode, 61. main body, 62. upper cover, 63. water injection valve, 64. copper electrode, 65. copper clip, 66. copper wire, 67. copper mesh, 68. porous bottom plate, 69. conductive liquid, 7. sample to be tested, 8. power supply device, 9. interface performance measurement instrument, 10. measurement main line. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0031] 1. Basic principles

[0032] On a semi-infinite body, the electric field characteristics of two point current sources A and B are as follows Figure 1 As shown, the expression of the potential U in a uniform material under a point current source is:

[0033]

[0034] Where I is the current between AB, r is the distance between AB, and ρ is the material resistivity.

[0035] For the current source field at two opposite points on the surface, according to the superposition principle, the potential at any point M can be obtained: The expression is:

[0036]

[0037] Among them, U AM is the potential of the electric field of the power source at point A, is the potential of the electric field of the power source at point B, AM and BM are the distances from M to the point current sources A and B.

[0038] Therefore, take any point N in the current source field of points A and B, and measure the potential difference between MN and the current between AB respectively, and the resistivity of the sample can be calculated. for:

[0039]

[0040] Then, the resistivity ρ is:

[0041]

[0042] However, in practical applications, an ideal uniform half-space situation is rarely encountered, that is, the potential difference measured by the above method has a large error, and the calculated resistivity value is not the true resistivity of the interface, which is called apparent resistivity.

[0043] Since the defects in the sample or the pores between the contact interfaces can be considered as the transformation of the material from conductor to air, and the conductivity of the conductor and the air is quite different, the actual resistivity differs by several orders of magnitude. Therefore, the apparent resistivity measured under two-point power supply will also differ by several orders of magnitude, with obvious differences. Then, according to the distribution or mutation of the apparent resistivity, the defect distribution inside the sample or the contact condition on the contact interface can be obtained.

[0044] Furthermore, when subjected to normal load F and tangential force T, the electric potential U(F,T) at any point on the sample interface is:

[0045]

[0046] Among them, R(F,T) is the resistance of the point when it is subjected to normal load F and tangential force T, R0 is the resistance of the point when it is not subjected to tangential force, b and k are fitting parameters, then the potential difference between MN It can be written as:

[0047]

[0048] Substituting equation (6) into equation (4), the resistivity is obtained as follows:

[0049]

[0050] 2. Establishing the force-electrical contact model

[0051] For all normal loads and all interface types, the reduction in contact resistance R(T) can be fitted as follows:

[0052] R(T)=R 0 -αT 2 (8)

[0053] In the formula, R 0 is the initial contact resistance at T = 0, and α is the fitting parameter related to the normal load.

[0054] The decrease in contact resistance stops soon after the tangential force reaches the maximum static friction force, which marks the beginning of macroscopic sliding of the interface. The relationship between the interface friction force (i.e., tangential force T) and the true contact area can be expressed by the following formula:

[0055] T=σS real (9)

[0056] Where σ is the shear strength of the material, S realis the actual contact area.

[0057] Combine equations (8) and (9) and substitute them into the Holm model (i.e. ), we can get the electrical measurement formula of friction force:

[0058]

[0059] Where R is the contact resistance, ρ is the material resistivity, a is the contact radius, and b and k are fitting parameters.

[0060] The fitting parameter α related to the normal load represents the speed at which the contact resistance decreases with the increase of the tangential force. By fitting the experimental data to obtain the α corresponding to different normal loads, and taking the double logarithmic coordinates, it can be seen that the normal load and the fitting parameter α are approximately linearly related (refer to Figure 2 ), and the following relationship is obtained by fitting a function in the form of y=ax+b:

[0061] log 10 α=klog 10 F+c (12)

[0062] Then we have:

[0063]

[0064] Wherein, α is the fitting parameter related to the normal load, F is the normal load, and for stainless steel material, k = -3.55935, c = 3.03302.

[0065] 3. Transformation of electrical signals into mechanical signals

[0066] By measuring the interface contact current, calculating the contact resistance and resistivity, and substituting them into the force-electric contact model, we can get the contact resistance under normal load F. N When the tangential force T on the contact interface N Distribution; subject to tangential force T N When the normal load F on the contact interface N distribution; thus the distribution of normal stress σ and tangential stress τ is obtained, and then the contact surface defects corresponding to the distribution of normal stress and tangential stress of the contact surface, and the internal defects corresponding to the distribution of internal normal stress and tangential stress are obtained. At the same time, the contact surface contact situation and the normal stress distribution corresponding to the rough interface in the stress distribution corresponding to the contact surface, as well as the measured rough interface edge contour curve, are used to inversely calculate the random number generation seed, and then the random number generation seed is fixed during the non-Gaussian numerical simulation process to obtain a uniquely determined interface morphology. Finally, the synchronous measurement of the contact interface / internal defects and interface morphology is achieved, achieving the purpose of obtaining the performance, characteristics and load on the contact interface by measuring electrical signals.

[0067] 4. Multi-electrode electromagnetic solid interface performance measurement device

[0068] The structural schematic diagram of the multi-electrode electromagnetic solid interface performance measurement device provided by the present invention is shown in FIG. Figure 3 , including a support frame 1, a counterweight host 2, a slide rail 3, an active pulley 4 and a copper elastic electrode 6. The top of the support frame 1 is provided with a slide rail 3, and an active pulley 4 is installed on the slide rail 3. The active pulley 4 is driven by a motor, and the active pulley 4 is fixed to the top of the counterweight host 2. The counterweight host 2 is driven to move by the active pulley 4. The counterweight host 2 is used to apply a load to compress the electrode. The counterweight host 2 is provided with an electrode transfer interface 5 for connecting a voltmeter and a power supply. The counterweight host 2 is provided with a power supply device 8 and an interface performance measuring electrical method instrument 9 (refer to Figure 4 ), the power supply device 8 supplies power to the interface performance measuring electrical instrument 9, the measurement main line 10 of the interface performance measuring electrical instrument 9 is connected to multiple copper elastic electrodes 6, the copper elastic electrodes 6 are located at the outer bottom of the counterweight main unit 2, the copper elastic electrodes 6 can apply pressure to the test sample 7, so that the electrode and the test sample 7 maintain good contact during the movement of the counterweight main unit 2, and the multiple copper elastic electrodes 6 are arranged along the moving direction of the counterweight main unit 2.

[0069] The structure of the copper elastic electrode 6 is as follows Figure 5 As shown, it includes a main body 61, and an upper cover 62 and a porous bottom plate 68 are respectively arranged on the top and bottom of the main body 61. A water injection valve 63 and a copper electrode 64 are arranged on the upper cover 62. The outer end of the copper electrode 64 is connected to a copper clip 65 through a connecting copper wire. The copper clip 65 is connected to an interface performance measuring electrical method instrument 9 inside the counterweight host 2. The inner end of the copper electrode 64 is connected to a copper mesh 67 through a copper wire 66. The copper mesh 67 is horizontally arranged above the porous bottom plate 68. A conductive liquid 69 is arranged in the main body 61.

[0070] The support frame 1 adopts an automatic telescopic deformation structure, and the length of the slide rail 3 is adjustable, which can change with the expansion and contraction of the support frame 1, ensuring that the total length of the slide rail 3 is longer than the test sample 7, and the stroke is adjusted to meet the different installation scenarios of the test sample 7, expand the application range, reduce the cost, and reduce the cost. When the length of the test sample 7 >> the length of the slide rail 3, the support frame 1 is placed on the surface of the test sample 7, and multiple measurements are performed in sections; when the length of the test sample 7 << the length of the slide rail 3, the support frame 1 is placed at both ends of the test sample 7, and the active pulley 4 slides from one end of the slide rail 3 to the other end for continuous measurement.

[0071] During the test, the sample to be tested 7 is placed under the counterweight main unit 2 and the copper elastic electrode 6 is in contact with the top surface of the sample to be tested 7. The active pulley 4 controls the device to move slowly along the surface of the sample to be tested 7 as a whole, so as to obtain a continuous measurement line instead of a single measurement point, thereby obtaining a continuous resistivity change value of the contact surface or a certain internal section, thereby obtaining a continuous contact condition of the contact interface or a continuous feature of the section, and finally obtaining the contact feature of the contact surface or the defect distribution feature of the section.

[0072] According to the above basic principle, the detection depth can be controlled by controlling the distance between electrodes. Therefore, the electrode spacing needs to be changed to measure the voltage information at different depths. Therefore, an electrode adapter 5 with different spacings is set on the counterweight host 2 and connected to an electric meter to realize the control of the test depth of the measuring device. During measurement, the measuring point moves toward the end of the profile, and the voltage between the electrodes is measured to obtain the voltage measurement data of the first layer. Subsequently, the spacing between the electrodes is increased, and the measuring point moves toward the end of the profile to obtain the voltage measurement data of the second layer. By analogy, a measurement surface is obtained by superimposing the voltage measurement data, and then the force-electric contact model is applied to convert the electrical signal into a force signal, and finally the performance and characteristics of the contact interface and the measurement results of the load on the interface are obtained.

[0073] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A multi-electrode electromagnetic solid interface performance measurement method, characterized in that: The method comprises the following steps: S1, under two opposite current sources A and B, calculate the potential of any two points M and N on the sample interface when the interface is subjected to normal load and tangential force; S2. According to the electric potential, the potential difference between M and N is obtained when two opposite-polarity current sources A and B are used as power supply electrodes; S3. Calculate the resistivity and contact resistance of the sample to be tested through the potential difference between M and N and the current between A and B; Potential difference between MN for: Where I is the current between AB, R 0 M is the resistance when point M is not subjected to tangential force, R 0 N is the resistance when point N is not subjected to tangential force, b and k are fitting parameters, F is the normal load, and T is the tangential force; The potential difference Substitute the calculation formula into In the case of Replace ΔU MN , then the resistivity ρ is: Among them, AM, BM are the distances from M to the point current sources A and B, AN, BN are the distances from N to the point current sources A and B; The calculation formula of contact resistance R is: S4. Establish a force-electric contact model, the expression is as follows: In the formula, S real is the true contact area, a is the contact radius, R is the contact resistance, ρ is the material resistivity, T is the tangential force, F is the normal load, σ is the material shear strength, and R 0 is the initial contact resistance, b and k are fitting parameters; S5. Substitute the resistivity and contact resistance of the sample to be tested into the force-electric contact model to obtain the distribution of tangential force on the contact interface when subjected to normal load, and the distribution of normal load on the contact interface when subjected to tangential force; thereby obtaining the distribution of normal stress and tangential stress on the contact surface, and then obtaining contact surface defects corresponding to the distribution of normal stress and tangential stress on the contact surface, and internal defects corresponding to the distribution of internal normal stress and tangential stress; at the same time, using the normal stress distribution corresponding to the rough interface in the contact condition of the contact surface and the stress distribution corresponding to the contact surface, as well as the measured rough interface edge contour curve, inversely calculate the random number generation seed, and then fix the random number generation seed during the non-Gaussian numerical simulation to obtain a uniquely determined interface morphology.

2. A multi-electrode electromagnetic solid interface performance measurement device for implementing the multi-electrode electromagnetic solid interface performance measurement method according to claim 1, characterized in that: It includes a supporting frame, a counterweight mainframe, a slide rail, an active pulley and a copper elastic electrode. A slide rail is arranged on the top of the supporting frame, an active pulley is installed on the slide rail, and the active pulley is fixed to the top of the counterweight mainframe. A plurality of electrode adapters are arranged on the counterweight mainframe. A power supply device and an interface performance measuring electrical method instrument are arranged inside the counterweight mainframe. A measuring main line of the interface performance measuring electrical method instrument is connected to a plurality of copper elastic electrodes. The copper elastic electrodes are located at the outer bottom of the counterweight mainframe. The plurality of copper elastic electrodes are arranged along the moving direction of the counterweight mainframe, and the copper elastic electrodes are in contact with the sample to be tested.

3. The multi-electrode electromagnetic solid interface performance measuring device according to claim 2, characterized in that: The support frame adopts an automatic telescopic deformation structure, and the length of the slide rail is adjustable.

4. The multi-electrode electromagnetic solid interface performance measurement device according to claim 2, characterized in that: The distances between the plurality of electrode transfer interfaces are different.

5. The multi-electrode electromagnetic solid interface performance measurement device according to claim 2, characterized in that: The copper elastic electrode includes a main body, and an upper cover and a porous bottom plate are respectively arranged on the top and bottom of the main body. A water injection valve and a copper electrode are arranged on the upper cover. The outer end of the copper electrode is connected to a copper clip through a connecting copper wire, and the copper clip is connected to an interface performance measuring electrical instrument inside the counterweight main unit. The inner end of the copper electrode is connected to a copper mesh through a copper wire, and the copper mesh is horizontally arranged above the porous bottom plate. A conductive liquid is arranged in the main body.

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