Method for calculating friction force and friction coefficient between pivot rails

Abstract

The invention provides a method for calculating friction force and friction coefficient between pivot rails, and the method mainly comprises the steps: inputting theoretical voltage into an equivalent model of a transmitter, and obtaining an armature theoretical speed which only considers line loss under the condition of no friction force; the theoretical voltage is input into an armature transmitting device, the real-time current, the real-time voltage and the moving speed of an armature in the transmitting process are obtained, and the overall resistance of the pivot rail is calculated through the real-time current and the real-time voltage of the armature; on the basis of the energy conservation principle, energy loss in the armature launching process is calculated, pivot rail friction force acting can be obtained, and then friction force between pivot rails is calculated; finite element software is used for constructing a pivot rail characteristic model, the pivot rail characteristic model is used for solving the contact pressure of a pivot rail contact interface in the electromagnetic emission process, and then the friction coefficient between pivot rails is obtained. According to the method, the friction force and the friction coefficient between the pivot rails can be calculated, and powerful support is provided for revealing a current-carrying friction wear mechanism of the pivot rails in the electromagnetic emission process.

Description

Technical Field

[0001] The invention relates to the technical field of electromagnetic emission, in particular to a method for calculating the friction force and friction coefficient between a pivot rail. Background Art

[0002] Electromagnetic launch technology is to achieve ultra-high-speed launch of the armature by using electromagnetic force to accelerate the armature through instantaneous conversion of electromagnetic energy and kinetic energy. Compared with traditional launch methods, electromagnetic launch has the advantages of high launch speed, long range, high precision and low cost. In the long run, it can be applied to missile launch, super high-speed rail and aerospace. In the actual launch process, the armature is rapidly advanced on the energized track. The electromagnetic track is subjected to the extreme impact of electromagnetic-thermal-force multi-field coupling and the friction and wear of ultra-high-speed sliding current, which causes serious damage to the electromagnetic track. However, due to the strong magnetic field, large current and ultra-high sliding speed of the armature during the electromagnetic launch process, it is difficult for traditional measurement devices to perform real-time dynamic monitoring and collection of the friction force and friction coefficient between the armature and the rail under such extreme conditions, resulting in unclear disclosure of the friction failure mechanism of the armature-rail interface, which seriously restricts the reliability and service life of the electromagnetic rail launch system.

[0003] Therefore, it is urgent to propose a method for calculating the friction force and friction coefficient between the pivot rails to solve the above technical problems. Summary of the invention

[0004] In order to address the deficiencies in the prior art, the present invention provides a method for calculating the friction force and friction coefficient between the armature and the rail. This method can calculate the friction force and friction coefficient between the armature and the rail (referring to the armature and the electromagnetic rail) under extreme conditions (such as strong magnetic field, large current and ultra-high sliding speed of the armature), which provides strong support for revealing the friction and wear mechanism of the armature and the rail during electromagnetic launch.

[0005] In order to achieve the above object, the specific scheme adopted by the present invention is: A method for calculating the friction force and friction coefficient between an armature and a rail is provided, and the calculation is performed by means of an armature launching device. The calculation method mainly comprises the following steps: S1. Establish a transmitter equivalent model, input the theoretical voltage into the transmitter equivalent model, and obtain the armature theoretical speed without friction and only considering line loss; S2, inputting the theoretical voltage into the armature launching device, obtaining the real-time current of the armature, the real-time voltage of the armature and the movement speed of the armature during the launching process, and calculating the overall resistance of the armature rail using the real-time current of the armature and the real-time voltage of the armature; S3, based on the principle of energy conservation and the calculation results of steps S1 and S2, the energy loss during the armature launch process is calculated, the work done by the friction force of the armature and the rail can be obtained, and then the friction force between the armature and the rail can be calculated; S4. Use finite element software to construct a pivot-rail characteristic model, and use the pivot-rail characteristic model to solve the contact pressure of the pivot-rail contact interface during electromagnetic launch, and then obtain the friction coefficient between the pivot and the rail.

[0006] Furthermore, the armature transmitting device includes an armature, a pulse power supply, an electromagnetic track, a B probe, a fixing part, a current sensor and a voltage sensor; wherein the B probe and the electromagnetic track are both arranged on the fixing part, and two electromagnetic tracks are provided, and the two electromagnetic tracks are arranged in parallel up and down and have channels for the armature to pass through opposite to each other, and a plurality of B probes are evenly distributed along the extension direction of the channel, and are used to monitor and obtain the changes in the magnetic field during the movement of the armature, and obtain the movement speed of the armature; the current sensor is arranged at the initial position of the armature, and is used to monitor and obtain the real-time current of the armature in real time; the positive and negative poles of the voltage sensor are respectively installed on the upper and lower electromagnetic tracks, and are used to monitor and obtain the real-time voltage of the armature in real time; the pulse power supply supplies power to the electromagnetic track.

[0007] Furthermore, in step S1, the method for solving the theoretical armature speed using the transmitter equivalent model is: Where: t is time, I1(t) is the current generated by the pulse power supply, C is the capacitor capacitance, U(t) is the theoretical voltage, W 总 is the energy generated by the pulse power supply, E k1 is the theoretical kinetic energy of the armature, v1(t) is the theoretical speed of the armature, and m is the mass of the armature.

[0008] Furthermore, in step S2, the method for calculating the overall resistance R(t) of the hinge rail is: Among them, U2(t) is the real-time voltage of the armature, and I2(t) is the real-time current of the armature.

[0009] Furthermore, in step S3, the specific calculation method for calculating the friction force between the pivot rails is: Where: E k2 is the actual kinetic energy of the armature, v2(t) is the armature motion speed actually measured by multiple B probes, W 空 is the work done by air resistance, W f is the work done by the friction force of the pivot rail, W 阻 is the work done by the resistance heat, F 空 (t) is the air resistance, s(t) is the actual displacement of the armature; r is the specific heat capacity ratio of air, ρ0 is the air density, A 枢 is the cross-sectional area of ​​the armature, a(t) is the actual acceleration section of the armature, P is the circumference of the armature cross-sectional area, F f (t) is the friction force between the pivot rail.

[0010] Furthermore, in step S4, the specific method for calculating the friction coefficient is: S41, establishing an armature-rail characteristic model of the armature launching device in finite element software, wherein the armature-rail characteristic model includes an electromagnetic field module and a mechanical module; S42, inputting the real-time armature current actually monitored by the current sensor in step S2 into the electromagnetic field module, and using the electromagnetic field module to solve the inductance gradient; S43, inputting the inductance gradient solved in step S42 into the mechanics module, and using the mechanics module to solve the contact pressure of the pivot-rail contact interface during the electromagnetic launch process, the calculation formula is: Where: F 压 (t) is the contact pressure of the armature-rail contact interface during electromagnetic launch, L' is the inductance gradient, and α is the angle between the armature tail and the electromagnetic track; S44, using the contact pressure of the contact interface between the pivot and the rail during the electromagnetic launch calculated in step S43 to calculate the friction coefficient between the pivot and the rail, the calculation formula is: Where: f(t) is the friction coefficient between the armature and rail, and F0 is the armature preload.

[0011] Furthermore, in step S2, in addition to calculating the overall resistance of the pivot rails, the contact resistance between the pivot rails can also be obtained. The contact resistance between the pivot rails is calculated as follows: Where: R 接 (t) is the contact resistance, R1(t) is the electromagnetic track resistance, R2 is the armature resistance, ρ is the electromagnetic track resistivity, A 轨 is the cross-sectional area of ​​the electromagnetic track.

[0012] Beneficial effects:

[0013] (1) Based on the principle of conservation of energy, the present invention uses experiments and simulation analysis to calculate the friction between the pivot rails on the basis of the test results, and the calculation results are more accurate.

[0014] (2) The present invention proposes a launcher equivalent model based on an armature launch device, which can solve the theoretical launch speed of the armature.

[0015] (3) The present invention uses finite element analysis to calculate the contact pressure of the pivot rail contact interface during electromagnetic launch, and solves the friction coefficient of the contact interface based on the previous calculation. Combined with subsequent surface analysis, it provides strong support for revealing the current-carrying friction and wear mechanism of the pivot rail during electromagnetic launch. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1It is a flow chart of the method for calculating the friction force and friction coefficient between the pivot rails in the present invention.

[0017] Figure 2 It is a schematic diagram of the armature launching device in the present invention.

[0018] Figure 3 It is a schematic diagram of the installation position of the voltage sensor in the present invention.

[0019] Markings in the diagram: 1. B probe, 2. Electromagnetic track, 3. Fixing part, 4. Current sensor, 5. Voltage sensor, 6. Pulse power supply, 7. Armature. DETAILED DESCRIPTION

[0020] The technical solution of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0021] The present invention is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0022] The present invention discloses a method for calculating the friction force and friction coefficient between the armature and the rail, wherein the calculation is carried out by means of an armature launching device and combined with Figure 2-3 It can be known that the armature transmitting device in the present invention includes an armature 7, a pulse power supply 6, an electromagnetic track 2, a B probe 1, a fixing part 3, a current sensor 4 and a voltage sensor 5; wherein, the B probe 1 and the electromagnetic track 2 are both arranged on the fixing part 3, and two electromagnetic tracks 2 are provided, and the two electromagnetic tracks 2 are arranged in parallel up and down and are oppositely provided with channels for the armature 7 to pass through, and a number of B probes 1 are evenly distributed along the extension direction of the channel, and the B probe 1 is arranged in the middle of the channel, and is used to monitor and obtain the magnetic field changes when the armature 7 moves, and obtain the armature movement speed; the current sensor 4 is arranged at the initial position of the armature 7, and is used to monitor and obtain the real-time current of the armature in real time; the positive and negative poles of the voltage sensor 5 are respectively installed on the upper and lower electromagnetic tracks 2, and are used to monitor and obtain the real-time voltage of the armature in real time; the pulse power supply 6 supplies power to the electromagnetic track 2. The following is combined with Figure 1 Each step is explained in detail.

[0023] S1. Establish a transmitter equivalent model, input the theoretical voltage into the transmitter equivalent model, and obtain the armature theoretical speed v1(t) without friction and only considering line loss.

[0024] In step S1, the formula for solving the theoretical armature speed using the transmitter equivalent model is:

[0025] Where: t is time, I1(t) is the current generated by the pulse power supply, C is the capacitor capacitance, U(t) is the theoretical voltage, W 总 is the energy generated by the pulse power supply, E k1 is the theoretical kinetic energy of the armature, v1(t) is the theoretical speed of the armature, and m is the mass of the armature.

[0026] S2. Input the theoretical voltage into the armature launching device to obtain the real-time current I2(t), real-time voltage U2(t) and movement speed of the armature during the launching process. Use the real-time current I2(t) and real-time voltage U2(t) of the armature to calculate the overall resistance of the armature rail and the contact resistance of the armature rail.

[0027] In step S2, the method for calculating the overall resistance R(t) of the hinge rail is: Among them, U2(t) is the real-time voltage of the armature, and I2(t) is the real-time current of the armature.

[0028] In addition, the contact resistance between the pivot rails is calculated as: Where: R 接 (t) is the contact resistance, R1(t) is the electromagnetic track resistance, R2 is the armature resistance (which can be measured before the test and is a constant value during the test), ρ is the electromagnetic track resistivity, A 轨 is the cross-sectional area of ​​the electromagnetic track.

[0029] S3. Based on the principle of energy conservation and the calculation results of steps S1 and S2, the energy loss during the armature launch process is calculated to obtain the work done by the friction force between the armature and the rail, and then the friction force F between the armature and the rail is calculated. f .

[0030] In step S3, based on the principle of energy conservation, the energy loss during the armature launch process is calculated to obtain the work done by the friction force, and then the friction force between the armature and the rail is calculated. The specific calculation method is: Where: E k1 is the theoretical kinetic energy of the armature, v1(t) is the theoretical speed of the armature, m is the mass of the armature, E k2 is the actual kinetic energy of the armature, v2(t) is the armature motion speed actually measured by multiple B probes, W 空 is the work done by air resistance, W f is the work done by the friction force of the pivot rail, W 阻 is the work done by the resistance heat, F 空 (t) is the air resistance, s(t) is the actual displacement of the armature; r is the specific heat capacity ratio of air, ρ0 is the air density, A 枢is the cross-sectional area of ​​the armature, a(t) is the actual acceleration section of the armature, and P is the circumference of the cross-sectional area of ​​the armature; F f (t) is the friction between the pivot rail. The above parameters, except for the friction between the pivot rail F f (t), and the remaining parameters can be obtained through actual measurement and related calculations based on the measured values.

[0031] S4. Use finite element software to construct a pivot-rail characteristic model, and use the pivot-rail characteristic model to solve the contact pressure of the pivot-rail contact interface during electromagnetic launch, and then obtain the friction coefficient between the pivot and the rail.

[0032] In step S4, the friction coefficient is calculated by using finite element software to construct a pivot-rail characteristic model, wherein the pivot-rail characteristic model includes an electromagnetic field module and a mechanical module. The electromagnetic field module is used to obtain the inductance gradient after current is passed; and the mechanical module is used to calculate the contact pressure of the pivot-rail contact interface during electromagnetic emission.

[0033] Specifically, a pivot-rail characteristic model is constructed using finite element software, and the pivot-rail characteristic model is used to solve the contact pressure of the pivot-rail contact interface during electromagnetic launch, thereby obtaining the friction coefficient between the pivot and the rail, including the following steps: S41, establishing an armature-rail characteristic model of the armature launching device in finite element software, wherein the armature-rail characteristic model includes an electromagnetic field module and a mechanical module; S42, inputting the real-time armature current actually monitored by the current sensor in step S2 into the electromagnetic field module, and using the electromagnetic field module to solve the inductance gradient; S43, inputting the inductance gradient solved in step S42 into the mechanics module, and using the mechanics module to solve the contact pressure of the pivot-rail contact interface during the electromagnetic launch process, the calculation formula is: Where: F 压 (t) is the contact pressure of the armature-rail contact interface during electromagnetic launch, L' is the inductance gradient, and α is the angle between the armature tail and the electromagnetic track; S44, using the contact pressure of the contact interface between the pivot and the rail during the electromagnetic launch calculated in step S43 to calculate the friction coefficient between the pivot and the rail, the calculation formula is: Where: f(t) is the friction coefficient between the armature and the rail; F0 is the armature preload (a constant value obtained when the armature launch device is installed).

[0034] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any equivalent changes or modifications made according to the essence of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for calculating the friction force and friction coefficient between pivot rails, characterized in that: The calculation is performed with the aid of an armature launch device, and the calculation method mainly includes the following steps: S1. Establish a transmitter equivalent model, input the theoretical voltage into the transmitter equivalent model, and obtain the armature theoretical speed without friction and only considering line loss; S2, inputting the theoretical voltage into the armature launching device, obtaining the real-time current of the armature, the real-time voltage of the armature and the movement speed of the armature during the launching process, and calculating the overall resistance of the armature rail using the real-time current of the armature and the real-time voltage of the armature; S3, based on the principle of energy conservation and the calculation results of steps S1 and S2, the energy loss during the armature launch process is calculated, the work done by the friction force of the armature and the rail can be obtained, and then the friction force between the armature and the rail can be calculated; S4. Use finite element software to construct a pivot-rail characteristic model, and use the pivot-rail characteristic model to solve the contact pressure of the pivot-rail contact interface during electromagnetic launch, and then obtain the friction coefficient between the pivot and the rail.

2. A method for calculating the friction force and friction coefficient between pivot rails according to claim 1, characterized in that: The armature transmitting device comprises an armature, a pulse power supply, an electromagnetic track, a B probe, a fixing part, a current sensor and a voltage sensor; wherein the B probe and the electromagnetic track are both arranged on the fixing part, two electromagnetic tracks are arranged in parallel up and down and oppositely provided with channels for the armature to pass through, and a plurality of B probes are evenly distributed along the extension direction of the channel, and are used to monitor and obtain the magnetic field changes during the movement of the armature and obtain the movement speed of the armature; the current sensor is arranged at the initial position of the armature, and is used to monitor and obtain the real-time current of the armature in real time; the positive and negative poles of the voltage sensor are respectively installed on the upper and lower electromagnetic tracks, and are used to monitor and obtain the real-time voltage of the armature in real time; the pulse power supply supplies power to the electromagnetic track.

3. A method for calculating the friction force and friction coefficient between pivot rails according to claim 2, characterized in that: In step S1, the method for solving the theoretical armature speed using the transmitter equivalent model is: Where: t is time, I1(t) is the current generated by the pulse power supply, C is the capacitor capacitance, U(t) is the theoretical voltage, W 总 is the energy generated by the pulse power supply, E k1 is the theoretical kinetic energy of the armature, v1(t) is the theoretical speed of the armature, and m is the mass of the armature.

4. A method for calculating the friction force and friction coefficient between pivot rails according to claim 3, characterized in that: In step S2, the method for calculating the overall resistance R(t) of the hinge rail is: Among them, U2(t) is the real-time voltage of the armature, and I2(t) is the real-time current of the armature.

5. A method for calculating the friction force and friction coefficient between pivot rails according to claim 4, characterized in that: In step S3, the specific method for calculating the friction force between the pivot rails is: Where: E k2 is the actual kinetic energy of the armature, v2(t) is the armature motion speed actually measured by multiple B probes, W 空 is the work done by air resistance, W f is the work done by the friction force of the pivot rail, W 阻 is the work done by the resistance heat, F 空 (t) is the air resistance, s(t) is the actual displacement of the armature; r is the specific heat capacity ratio of air, ρ0 is the air density, A 枢 is the cross-sectional area of ​​the armature, a(t) is the actual acceleration section of the armature, P is the circumference of the armature cross-sectional area, F f (t) is the friction force between the pivot rail.

6. A method for calculating the friction force and friction coefficient between pivot rails according to claim 5, characterized in that: In step S4, the specific method for calculating the friction coefficient is: S41, establishing an armature-rail characteristic model of the armature launching device in finite element software, wherein the armature-rail characteristic model includes an electromagnetic field module and a mechanical module; S42, inputting the real-time armature current actually monitored by the current sensor in step S2 into the electromagnetic field module, and using the electromagnetic field module to solve the inductance gradient; S43, inputting the inductance gradient solved in step S42 into the mechanics module, and using the mechanics module to solve the contact pressure of the pivot-rail contact interface during the electromagnetic launch process, the calculation formula is: Where: F 压 (t) is the contact pressure of the armature-rail contact interface during electromagnetic launch, L′ is the inductance gradient, and α is the angle between the armature tail and the electromagnetic track; S44, using the contact pressure of the contact interface between the pivot and the rail during the electromagnetic launch calculated in step S43 to calculate the friction coefficient between the pivot and the rail, the calculation formula is: Where: f(t) is the friction coefficient between the armature and rail, and F0 is the armature preload.

7. A method for calculating the friction force and friction coefficient between pivot rails according to claim 1, characterized in that: In step S2, in addition to calculating the overall resistance of the pivot rail, the contact resistance between the pivot rails can also be obtained. The contact resistance between the pivot rails is calculated as follows: Where: R 接 (t) is the contact resistance, R1(t) is the electromagnetic track resistance, R2 is the armature resistance, ρ is the electromagnetic track resistivity, A 轨 is the cross-sectional area of ​​the electromagnetic track.

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