Armature surface wear assessment method and system

Abstract

The present invention relates to the field of armature loss research, and provides an armature surface wear evaluation method and system. The armature surface wear evaluation method comprises: respectively controlling charging voltage and initial roughness as single variables, performing armature wear experiments on an electromagnetic guide rail launch experimental platform, calculating the wear rate of each experiment, and measuring the surface roughness after wear; establishing a numerical model of armature wear based on charging voltage, initial roughness, wear rate, and surface roughness after wear; inputting charging voltage and initial roughness into the numerical model of armature wear to predict the wear rate and surface roughness after wear. The numerical model of armature wear established by the present invention can quickly obtain the armature wear rate and the surface roughness after wear according to the charging voltage and initial roughness, thereby reducing the experimental cost and improving the efficiency of loss evaluation.

Description

Technical Field

[0001] The invention relates to the field of armature loss research, and in particular to an armature surface wear assessment method and system. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] The electromagnetic launch device uses a strong magnetic field to drive the payload and achieves high-speed propulsion without the need for traditional fuel. It has the advantages of being environmentally friendly, having a high initial velocity, and having a long range. It has broad application prospects in satellite launches, high-speed trains, and space station cleaning. The armature is a key component of the electromagnetic launch device, and usually adopts a C-shaped solid structure to improve the electrical contact performance. An inevitable challenge is that the armature is prone to wear when sliding relative to the fastened guide rail, and its wear condition directly affects the electrical contact state between the armature and the rail. Contact failure may lead to transition ablation, which seriously affects the service life of the device. At the same time, wear will also weaken the mechanical properties of the armature body and affect the launch safety.

[0004] Considering the strength, conductivity and other properties, electromagnetic launchers usually use aluminum alloy armatures and rails. It has been confirmed that the wear during the launch process mainly occurs on the armature surface rather than in the rails. Since it runs in a closed track, it is difficult to measure the wear process online in real time. The current research on the armature wear mechanism mainly relies on the morphological observation and modeling analysis after launch. The Archard wear model shows that defects such as gouges on the armature surface will cause melting and loss of materials, and aluminum debris deposition can be clearly seen on the rails. Measurements show that the thickness of the aluminum deposition layer is about 3-10μm, and the maximum erosion depth occurs at the top and bottom edges of the armature surface, but the specific wear depth is not given, and the analysis of the armature photos is also limited to simple qualitative evaluation. Through image processing algorithms and precision instrument measurements, the armature surface contour fluctuations are quantitatively characterized by curves, which can more accurately determine the wear state, which is lacking in current research.

[0005] For a typical launch, the main heat sources are Joule heat and friction heat. The three-dimensional characteristics of Joule heat in armatures of different shapes and the damage law of dry friction heating on the armature-rail contact surface are analyzed. The internal ballistic dynamic process of armature wear is simulated considering the two heat sources, but the specific wear quality is not obtained. Unfortunately, due to the dependence of the traditional finite element method on the inherent grid, it has limitations in dealing with extreme deformation or phase change of the armature. As a supplement, these models lack an organic connection with experimental data.

[0006] The actual contact surface between the armature and the guide rail is composed of multiple tiny conductive spots, and the effective contact area is only about 1% of the nominal contact area. Friction experiments show that the contact area and wear diameter increase with increasing current. (Using a pulse power supply, adjusting the charging voltage can control the current passed.) Surface roughness is not only an important experimental indicator for evaluating contact quality, but also a key experimental condition affecting the contact state of the armature and rail. People generally pay attention to textured surfaces because they have good tribological properties such as changing contact area, blocking or lubrication. Different initial roughness levels of the armature surface are set in the model, and it is found that it is closely related to the melting rate and thickness of the material, but no experimental verification has been carried out. In order to clarify the wear characteristics of the armature with different currents and initial texture surfaces, there is still a lot of work to be done. In particular, it is urgent to explore the evolution of the macroscopic morphology, microstructure and organizational composition of the armature surface, analyze the armature wear mechanism under different working conditions, and propose a theoretical basis for preventing armature failure and extending the life of the device. Summary of the invention

[0007] In order to solve the technical problems existing in the above-mentioned background technology, the present invention provides a method and system for evaluating armature surface wear. The present invention improves the comprehensiveness and accuracy of armature surface wear evaluation by establishing a numerical model of armature wear.

[0008] In order to achieve the above object, the present invention adopts the following technical solution:

[0009] A first aspect of the present invention provides a method for evaluating armature surface wear.

[0010] A method for evaluating armature surface wear, comprising:

[0011] The charging voltage and initial roughness were controlled as single variables, and the armature wear test was carried out on the electromagnetic guide rail launch test platform. The wear rate of each experiment was calculated and the surface roughness after wear was measured.

[0012] A numerical model of armature wear is established based on charging voltage, initial roughness, wear rate and surface roughness after wear.

[0013] The charging voltage and initial roughness are input into the numerical model of armature wear to predict the wear rate and the surface roughness after wear.

[0014] Furthermore, the numerical model of armature wear is expressed by the following formula:

[0015]

[0016]

[0017] in, w r represents the wear rate,Sa Indicates the surface roughness of the armature after wear, U Indicates the charging voltage, Sa 0 represents the initial roughness.

[0018] Furthermore, the electromagnetic guide rail launch experimental platform includes: a charging circuit, a transmitter and a detection device;

[0019] The charging circuit includes: a charger, a power module, a modulating inductor L and a diode D2. The charger is connected to a step-up transformer and charges the pulse power module after rectification by a silicon stack. The power module uses a capacitor to generate a large pulse current and discharges it to the transmitter through a semiconductor switch component D1. The semiconductor switch component D1 is configured with a dynamic pulse absorption circuit and a pulse trigger circuit. The modulating inductor L is used to adjust the pulse width and peak value of the capacitor output to widen the waveform and slow down the impact of large current; after discharge, the energy is discharged through the freewheeling diode D2;

[0020] The launcher is designed with a rectangular caliber, including rails and armature;

[0021] The detection equipment includes current sensor CT, high-voltage probe, digital oscilloscope, voltage divider, digital instrument measurement, thermal field emission scanning electron microscope and electron energy spectrum, laser spectrum confocal microscope. The current sensor CT and high-voltage probe are used to detect the track current and muzzle voltage respectively, and the measured waveforms are connected to the digital oscilloscope; the charging voltage is measured using a voltage divider and a digital instrument; the thermal field emission scanning electron microscope combined with the electron energy spectrum is used to detect the surface micromorphology and local micro-area composition of the armature after emission; the laser spectrum confocal microscope is used to perform three-dimensional profile measurement to obtain the armature wear mark height and roughness data.

[0022] Furthermore, the method for calculating the wear rate of each experiment includes: measuring the armature mass before and after each launch, calculating the mass loss according to the difference between the armature mass before launch and the armature mass after launch; and obtaining the wear rate according to the ratio between the mass loss and the armature mass before launch.

[0023] Furthermore, the method for measuring the surface roughness after wear includes: after each experiment, obtaining an armature surface wear morphology image to locate the wear area; and using a laser spectral confocal microscope to measure the wear area to obtain the surface roughness after wear.

[0024] Furthermore, the method of acquiring the armature surface wear morphology image and locating the wear area includes: using a camera to collect the armature surface wear morphology image, performing Gaussian denoising, spatial enhancement and threshold segmentation processing on the armature surface wear morphology image, and marking the connected area, which is the wear area.

[0025] Furthermore, after each experiment, the worn area was analyzed using electron spectroscopy to obtain the changes in the element content in the worn area.

[0026] Furthermore, after each experiment, the variation of the peak heat flux density of Joule heat and the peak heat flux density of friction heat during the launch process with time were calculated to verify the numerical model of armature wear.

[0027] Furthermore, the initial roughness is determined by grinding the armature surface with sandpaper of different grits.

[0028] A second aspect of the present invention provides an armature surface wear assessment system.

[0029] An armature surface wear assessment system, comprising:

[0030] The experimental module is used to control the charging voltage and the initial roughness as single variables, conduct armature wear experiments on the electromagnetic guide rail launch experimental platform, calculate the wear rate of each experiment, and measure the surface roughness after wear;

[0031] A model building module for building a numerical model of armature wear based on charging voltage, initial roughness, wear rate, and surface roughness after wear;

[0032] The output module is used to input the charging voltage and initial roughness into the numerical model of armature wear to predict the wear rate and the surface roughness after wear.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] The main purpose of the present invention is to obtain the evolution law of armature wear under different charging voltages and initial surface roughness conditions through quantitative detection, so as to suppress the occurrence of material failure from the source. By establishing a numerical model of armature wear, the comprehensiveness and accuracy of armature surface wear evaluation are improved.

[0035] The numerical model of armature wear established in the present invention can quickly obtain the armature wear rate and the surface roughness after wear according to the charging voltage and the initial roughness, thereby reducing the experimental cost and improving the efficiency of loss assessment. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0037] Figure 1 Schematic diagram of the circuit of the electromagnetic guide rail launch experimental platform of this embodiment;

[0038] Figure 2: are the wear morphology images of the armature surface under different charging voltage experiments of this embodiment (the red substance is the conductive glue applied during the SEM test and can be ignored);

[0039] Figure 3 1 is the wear morphology image of the armature surface under different initial roughness experiments of this embodiment;

[0040] Figure 4 1900V armature image processing and connected domain counting results schematic diagram of this embodiment;

[0041] Figure 5 is a schematic diagram of wear results under different charging voltages of this embodiment;

[0042] Figure 6 is a schematic diagram of the wear results under different initial roughnesses of this embodiment;

[0043] Figure 7 Schematic diagram of the change in peak height of the straight line profile of this embodiment;

[0044] Figure 8 is a schematic diagram of the change of wear degree under different charging voltages of this embodiment;

[0045] Fig. 9 is a schematic diagram of the change of wear degree under different initial roughness of this embodiment;

[0046] Fig.10 is a schematic diagram of the surface microscopic morphology of the armature under different charging voltages of this embodiment;

[0047] Fig.11 is a schematic diagram of element distribution in the wear region at 1900V of this embodiment; Fig.11 (a) represents the distribution diagram of each element, (b) represents the schematic diagram of the energy and signal intensity of each element, (c) represents the distribution diagram of C, (d) represents the distribution diagram of O, (e) represents the distribution diagram of Al, (f) represents the distribution diagram of Fe, (g) represents the distribution diagram of Cu, and (h) represents the distribution diagram of Si;

[0048] Fig.12 is a schematic diagram of changes in element content in the wear area under different charging voltages of this embodiment;

[0049] Fig.13 is a schematic diagram of the surface microscopic morphology of the armature under different initial roughnesses of this embodiment;

[0050] Fig.14 is a schematic diagram of the change of element content in the wear area under different initial roughnesses of this embodiment;

[0051] Fig.15 is a schematic diagram of the change of heat flux density over time in this embodiment;

[0052] FIG16 (a) is a schematic diagram showing the variation of heat flux density with charging voltage in this embodiment;

[0053] FIG16( b ) is a schematic diagram showing the variation of heat flux with initial roughness in this embodiment;

[0054] Fig.17 is a schematic diagram of the dynamic wear process of the armature with increased charging voltage in this embodiment;

[0055] Fig.18 is a schematic diagram of the dynamic wear process of the armature with reduced initial roughness in this embodiment;

[0056] Fig.19 4 is a flow chart of the armature surface wear evaluation method of this embodiment. DETAILED DESCRIPTION

[0057] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0058] It should be noted that the following detailed descriptions are all illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0059] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0060] Embodiment 1

[0061] like Fig.19 As shown, this embodiment provides an armature surface wear assessment method, comprising:

[0062] The charging voltage and initial roughness were controlled as single variables, and the armature wear test was carried out on the electromagnetic guide rail launch test platform. The wear rate of each experiment was calculated and the surface roughness after wear was measured.

[0063] A numerical model of armature wear is established based on charging voltage, initial roughness, wear rate and surface roughness after wear.

[0064] The charging voltage and initial roughness are input into the numerical model of armature wear to predict the wear rate and the surface roughness after wear.

[0065] The present invention is experimentally verified through the following aspects: (1) Experimental platform and detection means; the operating procedures of electromagnetic emission experiments are described. Experiments are conducted for different charging voltages and initial surface roughness. (2) The wear characteristics of the armature surface are quantitatively analyzed by using image processing algorithms and confocal profile measurement. (3) The dynamic wear behavior of the armature under different working conditions is analyzed by microstructure and composition detection. In particular, the evolution of the armature wear pattern is revealed. (4) The above experimental conclusions are verified by calculating the Joule heat and friction heat flux density, and a numerical model of armature wear is established, and a basic scheme for guiding device design is proposed.

[0066] Step 1: Experimental platform and detection methods

[0067] The electromagnetic rail launch system operates under short-duration pulse discharge conditions. In order to achieve the current amplitude and energy intensity required for launch, the widely used energy drive device is a capacitor energy storage type pulse power supply. In order to reduce the parasitic mass of the launch component and improve the effective load ratio, the launch bore should be designed to be approximately square. Based on this, an electromagnetic rail launch experimental platform is built, and its circuit principle is as follows Figure 1 shown.

[0068] Figure 1 The experimental platform mainly includes: charging circuit, transmitter and detection equipment. The components involved include: voltage divider, high-voltage digital instrument, step-up transformer, rectifier silicon stack, resistor R1, switch K, resistor R2, capacitor C, resistor ,switch ,resistance , large-capacity semiconductor switch component D1, wave modulation inductor L, freewheeling diode D2 and transmitter. In the charging circuit, the charger with a capacity of 10kVA is connected to the step-up transformer, and the pulse power module is charged after rectification by the silicon stack. The maximum charging voltage can reach 100kV and the charging current is 100mA. The power module uses two groups of 4mF-5kV capacitors to generate large pulse currents, which are discharged to the transmitter through the large-capacity semiconductor switch component D1. The switch is equipped with necessary dynamic pulse absorption circuits and pulse trigger circuits. The wave modulation inductor L is used to adjust the pulse width and peak value of the capacitor output to widen the waveform and slow down the impact of large current. After discharge, the energy is discharged through the freewheeling diode D2. The transmitter is designed to be a 15mm×20mm rectangular caliber. The guide rail is made of two parallel 1200mm×23mm×2mm 45# medium carbon structural steel, and the inner bore is kept stable by polytetrafluoroethylene insulation support and pre-tightening bolts. The armature is made of 6063-T6 aluminum alloy, adopts a typical C-shaped solid structure, and weighs about 15.667g.

[0069] Before the formal experiment, a no-load experiment was carried out to check whether the line connection was good and to ensure that the capacitor could be effectively charged. The charging voltage was measured by a voltage divider (voltage divider ratio of 1000:1) and its matching digital instrument. During the experiment, a current sensor CT and a high-voltage probe (attenuation ratio of 1000:1) were used to detect the track current and muzzle voltage respectively, and the measured waveforms were connected to a digital oscilloscope. After the experiment, a KathMatic laser spectral confocal microscope (LSCM) was used to perform three-dimensional profile measurement to obtain data such as armature wear scar height and roughness. A GeminiSEM 300 thermal field emission scanning electron microscope (SEM) was used to detect the microscopic morphology of the armature surface, and the electron energy spectrum (Energy Dispersive Spectrometer, EDS) was combined to analyze its micro-region composition.

[0070] 2. Wear characteristics of armature surface

[0071] In order to explore the effects of charging voltage and initial roughness on the wear performance of the armature, two groups of experiments were carried out by controlling a single variable:

[0072] a) Using unground armature, set the charging voltage to 1900V, 2000V, 2100V, 2200V, 2300V and 2400V respectively.

[0073] b) The charging voltage was set to 2000V, and the armature surface was pre-polished with sandpaper of 120cw, 180cw, 240cw, 600cw, 800cw, 1000cw, 1500cw and 2000cw before launch. The initial roughness of the textured surface was 2.65 μm, 2.15 μm, 1.65 μm, 1.05 μm, 0.55 μm, 0.25 μm, 0.15 μm and 0.05 μm respectively measured by LSCM. That is, the smaller the sandpaper mesh, the rougher the polished armature surface.

[0074] Step 2.1: To preliminarily evaluate the degree of armature surface wear and determine the subsequent SEM observation area, a macroscopic image of the armature after firing was taken. The armature surface wear morphology under different charging voltage experiments is shown in Figure 2. Figure 2 shown.

[0075] Depend on Figure 2 It can be seen that as the voltage increases, the concave grinding pits and strip-shaped furrows on the armature surface after firing gradually transform into fine pits, dense scratches and conductive glue. The white one is the exposed aluminum alloy matrix, and the black metal oxide appears from the edge of the tail wing and spreads to the head of the armature. It is most widely distributed at 2100V and 2200V. After exceeding 2300V, the black area tends to decrease and is accompanied by tumor-like morphology.

[0076] Figure 3The armature surface wear morphology under different initial roughness experiments is provided. Figure 3 In the range above 1.05μm, as the initial roughness decreases, the grinding pits and scratches on the armature surface gradually become lighter after firing, and the grinding texture can still be seen in some local areas. When it is below 0.55μm, the black oxide spreads further forward, accompanied by complex gullies, tumors, and flowing water.

[0077] In order to quantitatively extract the wear information of the armature, an image processing algorithm is used to Figure 2 , Figure 3 The photos in the figure are subjected to Gaussian denoising, spatial enhancement and threshold segmentation, and the connected areas are marked. Taking the armature of 1900V transmission as an example, the image processing and connected area counting results are shown in Figure 4 shown.

[0078] Depend on Figure 4 It can be seen that the oxide in the image is binarized and segmented into black, while lighter-colored pits, scratches and other depressions are white. White depressions with the same grayscale value are identified as independent connected domains and selected with blue rectangles. The centroid position of each connected domain is marked with a red line and displayed as a green number based on this count. A total of 183 connected domains were identified at 1900V. The armature images are all 1064×1890 pixels, and the proportion of white areas and the number of connected domains are counted. At the same time, the ratio of the mass loss after launch to the mass before launch is calculated to analyze the change in wear rate. The wear results under different charging voltages are shown in Figure 2. Figure 5 shown.

[0079] Depend on Figure 5 It can be seen that as the charging voltage increases, the proportion of white areas and wear first decrease and then increase, while the number of connected domains changes in the opposite trend. This is because as the voltage increases, the number of pits decreases, changing from large-area, concentrated grinding pits to more small-area, shallow-depth pits, and the grinding process changes from local severe damage to more uniform slight damage, which is consistent with the Figure 2 However, after exceeding 2100V, the oxide layer covers a wider area, the aluminum alloy matrix peels off over a large area, the connected domains re-aggregate and the wear rate increases.

[0080] Similarly, the wear results under different initial roughness are calculated, such as Figure 6 As shown. Figure 6It can be seen that as the initial roughness decreases, the proportion of white areas first decreases, then slightly recovers and then decreases significantly. Wear first decreases and then increases slightly. The number of connected domains fluctuates irregularly, and the overall performance is an increase. This shows that as the initial surface becomes smoother, the number of grinding pits decreases and the distribution becomes more dispersed. When the roughness is lower than 0.25μm, the oxidation wear intensifies, but unlike the material spalling under the unpolished condition, the armature forms a complex melt morphology due to the deformation and accumulation of the metal and its oxides. Therefore, while the white aluminum alloy area decreases, the wear rate does not increase significantly.

[0081] Step 2.2: Wear profile and surface roughness.

[0082] In order to accurately analyze the wear characteristics of the armature, the armature surface profile and roughness data are obtained through LSCM. The armature of 1900V transmission is still taken as an example.

[0083] By scanning the height map point cloud data, accurate information about the armature surface contour can be obtained. In order to compare the damage degree of the front and rear ends of the armature, four horizontal lines x1~x4 are drawn on the armature surface for contour measurement. The peak height changes are shown in Figure 2. Figure 7 shown.

[0084] Figure 7 It shows that the four straight lines all have violent fluctuations in the front section and become gentle in the rear section. Due to the presence of grinding pits and furrows, there is an obvious depression on the armature head. A The highest peak of 1 is 322.77μm beyond the original reference surface, and the maximum valley depth is 203.55μm. The rear end of the armature is mainly composed of the flowing water structure of aluminum after being heated and melted and the wrinkles of oxide accumulation. The rear section of the contour line presents small and fine undulations, and the maximum peak height and valley depth are only 181.83μm and 86.92μm. A The surface roughness of 2 is significantly reduced, but due to the wider distribution of its wrinkles, the interface expansion area is larger.

[0085] In order to compare the changes in armature wear under different charging voltages, the surface roughness Sa, maximum peak height Sp, and maximum valley depth Sv were statistically analyzed. The results are as follows: Figure 8 shown.

[0086] Depend on Figure 8 It can be seen that as the charging voltage increases, Sa decreases first, then slightly recovers and then decreases again. At 1900V, there are significant pits and protrusions on the armature surface, and the surface roughness is very high. As the voltage increases, the degree of wear is reduced. When it increases to 2100V, although the depth of the local grinding pits decreases, due to the increase in heat and oxidation, a flowing water-like molten morphology appears on the surface, and the roughness increases instead. As the voltage continues to increase, the more uniform ablative expansion and large flakes of surface metal peel off, making the armature surface smoother and the roughness gradually decreases.

[0087] The wear degree of the armature under different initial roughness changes as shown in Fig. 9 As shown. Fig. 9 In the figure, as the initial roughness decreases, Sa decreases first and then increases. When the initial roughness is 2.65μm, the surface of the armature after launch is uneven, with large peak heights, valley depths and roughness. As the initial roughness decreases, the surface tends to be smoother. However, after it is lower than 1.05μm, severe high-temperature oxidation and melt ablation occur between the armature rails, and a large amount of oxide layer accumulates, accompanied by the formation of melt pits, cracks and even grooves, resulting in a significant increase in roughness.

[0088] Step 3: Dynamic wear behavior analysis

[0089] In order to investigate the microstructure and organizational composition of the armature wear surface and clarify the formation process and nature of the damage, based on macroscopic observation, the typical wear area with the highest surface roughness of the armature was selected, and the sampling size was set to 2mm×2mm. SEM micromorphology and EDS composition analysis were carried out on the armature surface under different working conditions to explore its dynamic wear behavior.

[0090] Step 3.1: Wear behavior at different charging voltages

[0091] The surface microstructure of the armature under different charging voltages is as follows: Fig.10 As shown. Fig.10 As the charging voltage increases, the wear debris becomes finer, and small holes and micro cracks deteriorate into deeper cracks, and finally flaking marks appear. Under 1900V, large pieces of wear debris with irregular shapes are formed, and the distance is relatively sparse. This is because under the friction of high-speed current, the harder rails scrape the softer aluminum alloy armature surface to produce wear debris, which is manifested macroscopically as Figure 2 The isolated and scattered grinding pits in the armature. As the voltage increases, on the one hand, the armature moves faster and the shear force acts for a shorter time. On the other hand, the normal component of the Lorentz force increases, and the grinding chips become smaller and sharper under the rolling action, which helps to cut the armature surface, thus forming Figure 2The roughness is also reduced. As the voltage continues to rise, the loop current increases, the accumulated Joule heat promotes the oxidation reaction, and the metal is softened by heat, and granular molten holes appear on the surface of the armature. A small amount of fatigue cracks appear at the stress concentration point at the bottom or edge of the hole, and they continue to deepen and deteriorate, and the surface roughness increases. This shows that after 2100V and 2200V, the wear mode begins to transition from abrasive wear to oxidation wear and fatigue wear. The cracks continue to expand and connect with each other along the direction of armature movement, eventually causing the metal material to peel off or accumulate. On the surface of the armature at 2300V, traces of peeling layers and corrugated deposits can be seen. The deposited layer effectively fills the depression of the aluminum matrix, the ablative expansion tends to be uniform, the armature surface is smoother, and the roughness decreases again. At 2400V, the peeling layer changes from gray-black to silver-gray, that is, the surface metal and the brittle oxide layer fall off in large pieces, exposing the underlying aluminum matrix.

[0092] Further, EDS was used to detect the element information of the wear interface. Taking the wear area at 1900V as an example, the element distribution is as follows: Fig.11 shown.

[0093] Depend on Fig.11 From (a) and (b), we can see that the main elements detected in the wear area are C, O, Al, Fe, Cu, Si, etc. Among them, Al accounts for more than 58.34%, which is the original 6063-T6 aluminum alloy armature matrix, and its main components also include Fe, Si, Cu, etc. Fig.11 It can be seen from (c), (d), and (f) that there are still a small amount of dispersed Fe, O, and C covering the Fig.11 Above the Al layer in Figure (e), this is the rail debris scattered during the scratching process. The changes in the element content in the wear area under different charging voltages are statistically analyzed. The results are as follows Fig.12 shown.

[0094] Depend on Fig.12 It can be seen that the changes in the content of Al, Si, and Cu elements are basically the same, first decreasing and then increasing, which represents the change in the proportion of aluminum alloy materials in the wear area, while the change in O element is the opposite. When it is lower than 2100V, with the increase of voltage, on the one hand, the abrasive wear is alleviated and the large-area pits on the armature surface are reduced, on the other hand, the oxidation wear is intensified, and the coverage area of ​​the oxide layer is getting wider and wider, so the proportion of Al decreases and O increases. After exceeding 2100V, the violent oxidation reaction and the uneven distribution of heat cause the cracks in the local stress concentration to expand or even penetrate. Compared with aluminum metal, oxides are more brittle and fragile. Under the cutting and plowing action of sharp grinding chips, they fall off in layers, re-exposing the aluminum alloy matrix and increasing the Al content. The trend of Fe element is not completely consistent with Al. Combined with the change of C element, it shows that there is a two-way transfer of metal materials during the armature-rail grinding process, and the filling of rail grinding chips is also reduced to a certain extent. Figure 8 Armature surface roughness at 2000V.

[0095] Step 3.2: Wear behavior under different initial roughness

[0096] The surface microstructure of the armature under different initial roughness is as follows Fig.13 As shown. Fig.13 , as the initial roughness decreases, the wear debris becomes smaller, and the armature surface becomes relatively flat temporarily, which leads to more serious material loss or accumulation. Fig.10 It can be found that the edges of the chips produced by sandpaper grinding and then firing are more rounded and blunt, the cutting ability is worse, and the armature wear rate is slightly improved (compared to Figure 5 and Figure 6 ) and surface roughness (comparison Figure 8 and Fig. 9 ). When the initial roughness is 2.65μm, the loose micro-convex peaks grind the aluminum alloy at a certain angle of attack during the launch, leaving depressions or flanges on the armature surface. When the initial roughness decreases, the surface becomes smoother and the abrasive wear is reduced. At 1.65μm, the traces of grinding can still be seen in the local area after the launch. However, when it is reduced to less than 1.05μm, the conductive spots on the armature-rail contact surface are reduced due to the excessive smoothness of the polished surface, which reduces the effective transmission path of the current and increases the contact resistance. The accumulation of heat causes the armature to continue to heat up and soften. The aluminum matrix undergoes plastic deformation under the cutting action of the abrasive chips, but it does not completely peel off. Instead, it is squeezed and accumulated on the surface to form plow wrinkles and flowing water-like structures. At the same time, local high temperature and compressive stress may cause the molten metal liquid film to be instantly cold-welded, accelerating the formation of a dark oxide layer. The brittle oxide layer is easy to break, and after falling off as abrasive chips, it adheres to the armature surface, further melts and stacks, leaving ablation pits and ridges. In addition, the adhered oxide transforms the original steel-aluminum contact into a more compatible contact of the same material, which makes the joint stronger and is conducive to adhesive wear. On the other hand, it reduces the conductive area, and more energy is converted into heat when the current passes through the armature, further exacerbating wear and degradation. A dazzling white light area was observed at 0.05μm, indicating that the conductivity of the sample is so poor that a charging effect occurs under the SEM lens.

[0097] The changes in element content in the wear area under different initial roughness were also detected. The results are as follows: Fig.14 As shown. Fig.14, as the initial roughness decreases, the Al, Si, and Cu elements first decrease, slightly increase, and then continue to decrease. The O element is the opposite, and the Fe and C elements fluctuate slightly. Above 1.65μm, as the surface flatness of the armature increases, the abrasive wear decreases, and the proportion of exposed aluminum matrix decreases. The fluctuations in Fe and C elements indicate that rail debris remains on the surface of the armature. As the initial roughness decreases, the increase in contact resistance leads to heat accumulation, and the wear mode between the armature and the rail transitions from abrasive wear to oxidative wear. It basically tends to be balanced at 1.65-1.05μm, and the roughness is also slightly improved ( Fig. 9 ). After that, the heat-affected zone continues to spread, and the oxide layer does not peel off violently like increasing the charging voltage, but accumulates on the surface of the armature, causing water-like structures and nodular defects under repeated plowing and cutting behaviors. The components of the oxide layer such as Fe, C, and O continue to increase, while the proportion of aluminum matrix elements decreases. In addition, a small amount of S element was detected at 0.25-0.05μm, which may be due to the reaction between the metal and the sulfide in the air under high-speed and high-temperature friction, which will further aggravate the ablation of the armature.

[0098] 4. Discussion

[0099] In order to clarify the damage mechanism of the hinge-rail contact interface, the time-dependent changes of the peak heat flux density of Joule heat QJ and friction heat QF during the launch process were calculated. Fig.15 As shown. Fig.15 It is easy to find that the change trend of Joule heat flux density is consistent with the pulse current source, first rising and then falling, while the friction heat flux density continues to rise. During the entire launch process, the initial armature movement speed is low, and the current quickly reaches the pulse peak. Joule heat, as the main heat source, causes pit-like ablation on the surface, especially at the front end, due to uneven distribution. After 3.05 ms, the armature movement speed increases, and the friction heat rises to exceed the Joule heat, forming a sheet-like high-temperature area on the tail wing and dominating the expansion melting phenomenon. Existing studies have pointed out that Joule heat is concentrated at the head of the armature, while the friction heat accumulated at the rear is harmful to the armature. This conclusion is consistent with the present invention, which further verifies the validity of the results. Then, the changes in the peak values ​​of the two heat flux densities under different charging voltages and initial roughness are calculated, as shown in Figures 16 (a) and 16 (b).

[0100] It can be seen from Figure 16 (a) and Figure 16 (b) that as the charging voltage increases and the initial roughness decreases, the Joule heat and friction heat flux densities continue to increase. The initial peak value of Joule heat is low, but the growth rate is faster, surpassing friction heat at 2100V and 0.55μm. This is consistent with the conclusion of existing studies that "friction heat mainly works when the armature moves at low speeds." In addition, the increase in Joule heat caused by the increase in charging voltage is more significant than the decrease in roughness. Taking into account the changes in wear morphology and heat flux density, the dynamic wear process of the armature with increasing charging voltage is as follows: Fig.17 shown.

[0101] according to Fig.17 Under low voltage, the armature first experiences abrasive wear, forming grinding pits and furrows extending along the direction of movement on the surface. As the voltage increases, the abrasive particles become finer under the normal extrusion, and the abrasive wear is reduced. The accumulation of heat also catalyzes oxidative wear, forming a black brittle oxide layer on the surface of the armature. After exceeding 2100V, the Joule heat rises sharply, and the high-speed moving armature is always in contact with the new room temperature track in front, and the heat is quickly taken away with a higher temperature gradient. Under the action of the alternating force generated by the strong alternating temperature field, the armature produces cracks and expands, eventually causing the surface metal, especially the brittle oxide, to fall off in flakes, and the wear turns into fatigue wear.

[0102] Reducing the initial roughness of the armature's dynamic wear process Fig.18 As shown. Fig.18 , the armature first experiences abrasive wear. As the initial roughness decreases, the abrasive grains become more rounded and blunt, the cutting action weakens, and the abrasive wear is reduced. At the same time, due to the reduction of conductive spots and the increase of contact resistance, the surface of the aluminum alloy undergoes an oxidation reaction with the gas medium under the action of high temperature, and an oxide film adheres to the surface. The oxide film is squeezed and transferred, and the newly exposed surface is oxidized and accumulated again, eventually forming a complex molten morphology. Under the action of oxidation wear and adhesive wear, the material does not fall off in large quantities, but the conductivity deteriorates.

[0103] The above studies show that the charging voltage and initial roughness have a complex relationship with the wear degree of the material. In order to comprehensively consider the influence of the two factors on the wear performance of the armature, the wear rate w r and armature surface roughness after wear Sa The relationship between the two:

[0104] (1)

[0105] (2)

[0106] In the formula, U is the charging voltage, Sa 0 is the initial roughness. Based on the above analysis, the present invention believes that the following methods can improve the wear performance of the armature:

[0107] 1) Apply appropriate charging voltage. It is unwise to blindly increase the charging voltage in pursuit of acceleration. For the 1.2m long track in this experimental platform, the optimal charging voltage is 2100V.

[0108] 2) Set the appropriate surface roughness level. For this platform, the optimal initial roughness is 0.55-1.05μm, which can be achieved by sanding with 600cw-800cw sandpaper. The conductivity of the rough material needs attention.

[0109] 3) For C-type solid armature, the head should improve heat resistance, the tail should strengthen wear resistance, and suitable plating or coating is worth looking forward to.

[0110] 5. Conclusion

[0111] The main purpose of the present invention is to obtain the evolution law of armature wear under different charging voltages and initial surface roughness conditions through quantitative detection, so as to suppress the occurrence of material failure from the source. Launch experiments with charging voltages of 1900V-2400V and initial roughness of 0.05μm-2.65μm were carried out, and image processing analysis, LSCM profile measurement, SEM morphology detection, EDS component analysis and heat flux density calculation were carried out on the armature surface after launch. For the work provided, the following statements are true:

[0112] 1) As the charging voltage increases, the armature wear first decreases and then increases, and the wear roughness first decreases, slightly increases, and then decreases. Abrasive wear turns into oxidation wear and fatigue wear, and large pieces of material fall off.

[0113] 2) As the initial roughness decreases, the wear of the armature first decreases and then increases slightly. The wear roughness increases overall, and the abrasive wear turns into oxidative wear and adhesive wear, and the conductivity is seriously damaged.

[0114] 3) The head of the C-type solid armature mainly undergoes pitting ablation caused by Joule heat, and the tail wing mainly undergoes expansion melting dominated by friction heat, which puts forward different requirements on the heat resistance and wear resistance of the material.

[0115] The present invention built an electromagnetic rail launch experimental platform, and carried out morphological analysis, contour measurement and composition detection on the armature surface after launch. The results show that as the charging voltage increases, the armature changes from abrasive wear to oxidative wear and fatigue wear. As the initial surface roughness decreases, abrasive wear, oxidative wear and adhesive wear occur in sequence. This is because the growth rate of Joule heat is higher than that of frictional heat, which gradually dominates the wear mode. For this platform, the optimal charging voltage and initial surface are 2100V and 0.55-1.05μm. Finally, a numerical model of armature wear and the optimization direction of armature design are proposed.

[0116] Embodiment 2

[0117] This embodiment provides an armature surface wear assessment system, comprising:

[0118] The experimental module is used to control the charging voltage and the initial roughness as single variables, conduct armature wear experiments on the electromagnetic guide rail launch experimental platform, calculate the wear rate of each experiment, and measure the surface roughness after wear;

[0119] A model building module for building a numerical model of armature wear based on charging voltage, initial roughness, wear rate, and surface roughness after wear;

[0120] The output module is used to input the charging voltage and initial roughness into the numerical model of armature wear to predict the wear rate and the surface roughness after wear.

[0121] In some embodiments, the numerical model of armature wear is expressed by the following formula:

[0122]

[0123]

[0124] in, w r represents the wear rate, Sa Indicates the surface roughness of the armature after wear, U Indicates the charging voltage, Sa 0 represents the initial roughness.

[0125] In some embodiments, the electromagnetic guide rail launch experimental platform includes: a charging circuit, a transmitter and a detection device;

[0126] The charging circuit includes: a charger, a power module, a modulating inductor L and a diode D2. The charger is connected to a step-up transformer and charges the pulse power module after rectification by a silicon stack. The power module uses a capacitor to generate a large pulse current and discharges it to the transmitter through a semiconductor switch component D1. The semiconductor switch component D1 is configured with a dynamic pulse absorption circuit and a pulse trigger circuit. The modulating inductor L is used to adjust the pulse width and peak value of the capacitor output to widen the waveform and slow down the impact of large current; after discharge, the energy is discharged through the freewheeling diode D2;

[0127] The launcher is designed with a rectangular caliber, including rails and armature;

[0128] The detection equipment includes current sensor CT, high-voltage probe, digital oscilloscope, voltage divider, digital instrument measurement, thermal field emission scanning electron microscope and electron energy spectrum, laser spectrum confocal microscope. The current sensor CT and high-voltage probe are used to detect the track current and muzzle voltage respectively, and the measured waveforms are connected to the digital oscilloscope; the charging voltage is measured using a voltage divider and a digital instrument; the thermal field emission scanning electron microscope combined with the electron energy spectrum is used to detect the surface micromorphology and local micro-area composition of the armature after emission; the laser spectrum confocal microscope is used to perform three-dimensional profile measurement to obtain the armature wear mark height and roughness data.

[0129] In some embodiments, the method for calculating the wear rate of each experiment includes: measuring the mass of the armature before and after each launch, calculating the mass loss based on the difference between the mass of the armature before launch and the mass of the armature after launch; and obtaining the wear rate based on the ratio between the mass loss and the mass of the armature before launch.

[0130] In some embodiments, the method for measuring the surface roughness after wear includes: after each experiment, obtaining an armature surface wear morphology image to locate the wear area; and using a laser spectral confocal microscope to measure the wear area to obtain the surface roughness after wear.

[0131] In some embodiments, the method of acquiring the armature surface wear morphology image and locating the wear area includes: using a camera to collect the armature surface wear morphology image, performing Gaussian denoising, spatial enhancement and threshold segmentation on the armature surface wear morphology image, and marking the connected area, which is the wear area.

[0132] In some embodiments, after each experiment, the worn area is analyzed using electron spectroscopy to obtain changes in element content in the worn area.

[0133] In some embodiments, after each experiment, the variation of the heat flux peak value of Joule heat and the heat flux peak value of friction heat during the launch process over time are calculated to verify the numerical model of armature wear.

[0134] In some embodiments, the initial roughness is determined by grinding the armature surface with sandpaper of different grits.

[0135] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for evaluating armature surface wear, characterized in that: include: The charging voltage and initial roughness were controlled as single variables, and the armature wear test was carried out on the electromagnetic guide rail launch test platform. The wear rate of each experiment was calculated and the surface roughness after wear was measured. A numerical model of armature wear is established based on charging voltage, initial roughness, wear rate and surface roughness after wear. The charging voltage and initial roughness are input into the numerical model of armature wear to predict the wear rate and the surface roughness after wear; The numerical model of armature wear is expressed by the following formula: in, w r represents the wear rate, Sa Indicates the surface roughness of the armature after wear, U Indicates the charging voltage, Sa 0 represents the initial roughness.

2. The armature surface wear evaluation method according to claim 1, characterized in that: The electromagnetic guide rail launch experimental platform includes: a charging circuit, a transmitter and a detection device; The charging circuit includes: a charger, a power module, a modulating inductor L and a diode D2. The charger is connected to a step-up transformer and charges the pulse power module after rectification by a silicon stack. The power module uses a capacitor to generate a large pulse current and discharges it to the transmitter through a semiconductor switch component D1. The semiconductor switch component D1 is configured with a dynamic pulse absorption circuit and a pulse trigger circuit. The modulating inductor L is used to adjust the pulse width and peak value of the capacitor output to widen the waveform and slow down the impact of large current; after discharge, the energy is discharged through the freewheeling diode D2; The launcher is designed with a rectangular caliber, including rails and armature; The detection equipment includes current sensor CT, high-voltage probe, digital oscilloscope, voltage divider, digital instrument measurement, thermal field emission scanning electron microscope and electron energy spectrum, laser spectrum confocal microscope. The current sensor CT and high-voltage probe are used to detect the track current and muzzle voltage respectively, and the measured waveforms are connected to the digital oscilloscope; the charging voltage is measured using a voltage divider and a digital instrument; the thermal field emission scanning electron microscope combined with the electron energy spectrum is used to detect the surface micromorphology and local micro-area composition of the armature after emission; the laser spectrum confocal microscope is used to perform three-dimensional profile measurement to obtain the armature wear mark height and roughness data.

3. The armature surface wear evaluation method according to claim 1, characterized in that: The method for calculating the wear rate of each experiment includes: measuring the armature mass before and after each launch respectively, calculating the mass loss according to the difference between the armature mass before launch and the armature mass after launch; and obtaining the wear rate according to the ratio between the mass loss and the armature mass before launch.

4. The armature surface wear evaluation method according to claim 1, characterized in that: The method for measuring the surface roughness after wear comprises: obtaining an armature surface wear morphology image after each experiment to locate the wear area; and measuring the wear area using a laser spectral confocal microscope to obtain the surface roughness after wear.

5. The armature surface wear evaluation method according to claim 4, characterized in that: The method for acquiring the armature surface wear morphology image and locating the wear area comprises: using a camera to collect the armature surface wear morphology image, performing Gaussian denoising, spatial domain enhancement and threshold segmentation processing on the armature surface wear morphology image, and marking the connected area, which is the wear area.

6. The armature surface wear evaluation method according to claim 4, characterized in that: After each experiment, the worn area was analyzed by electron spectroscopy to obtain the changes in element content in the worn area.

7. The armature surface wear evaluation method according to claim 1, characterized in that: After each experiment, the variation of the peak heat flux density of Joule heat and the peak heat flux density of friction heat during the launch process with time were calculated to verify the numerical model of armature wear.

8. The armature surface wear assessment method according to any one of claims 1 to 7, characterized in that: The initial roughness is determined by grinding the armature surface with different sandpaper grits.

9. An armature surface wear assessment system, characterized in that: include: The experimental module is used to control the charging voltage and the initial roughness as single variables, conduct armature wear experiments on the electromagnetic guide rail launch experimental platform, calculate the wear rate of each experiment, and measure the surface roughness after wear; A model building module for building a numerical model of armature wear based on charging voltage, initial roughness, wear rate, and surface roughness after wear; An output module for inputting the charging voltage and initial roughness into a numerical model of armature wear to predict the wear rate and the surface roughness after wear; The numerical model of armature wear is expressed by the following formula: in, w r represents the wear rate, Sa Indicates the surface roughness of the armature after wear, U Indicates the charging voltage, Sa 0 represents the initial roughness.

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