Material fatigue damage measuring device and method based on Ampere force loading

Abstract

The invention discloses a material fatigue damage measuring device and method based on Ampere force loading. The device comprises a base support; the circular magnetic field generating device is fixed on a top plate of the base bracket and is connected to the magnetic field controller through a first lead to adjust parameters of a magnetic field; the two sliding contact clamps are installed on the baffles on the two sides of the base support respectively. A to-be-tested material is fixed between the two sliding contact clamps, and the sliding contact clamps clamp the to-be-tested material through a sliding contact structure; the constant current source is connected to the two ends of the to-be-tested material through a second wire to form a closed loop, and ampere force is generated when current passes through the to-be-tested material; the constant current source provides constant current for the to-be-tested material and has an overcurrent protection function; according to the method, the stress and fatigue damage of the material under the action of the Ampere force can be accurately calculated through accurate current and magnetic field control in combination with the calculation formula of the Ampere force.

Description

Technical Field

[0001] The present invention belongs to the technical field of material fatigue performance testing, and in particular relates to a material fatigue damage measurement device and method based on Ampere force loading, which is suitable for research related to material mechanics, material science and electromagnetic mechanics. Background Art

[0002] Fatigue damage is a performance degradation phenomenon that gradually accumulates when a material is subjected to alternating loads, which is directly related to the service life and safety of the material. Traditional fatigue loading methods mainly rely on mechanical loading, applying alternating forces to the material through a contact loading device. However, this method has the problem of contact wear, that is, the contact between the mechanical loading system and the material causes additional wear, affecting the accuracy of the experimental results; there is also the problem of complex loading, that is, the mechanical loading system usually requires complex mechanical design, and the loading path and loading uniformity are difficult to guarantee. Therefore, the loading method based on electromagnetic force (Ampere force) has become a potential solution due to its strong controllability and simple structure. However, there is currently a lack of a complete fatigue damage measurement device based on Ampere force loading. Summary of the invention

[0003] The purpose of the present invention is to provide a material fatigue damage measurement device and method based on Ampere force loading to solve the technical problems of contact wear, high loading complexity and insufficient measurement accuracy existing in traditional mechanical loading.

[0004] In order to solve the above technical problems, the specific technical solutions of the present invention are as follows:

[0005] A material fatigue damage measuring device based on Ampere force loading includes a base bracket; the base bracket is composed of a bottom support structure and a top plate, and baffles are provided on both sides of the top plate for installing a sliding contact fixture to fix the material to be measured; the support structure has a support column, which can stand firmly on a working plane to provide reliable basic support for the overall device.

[0006] The circular magnetic field generating device is fixed on the top plate of the base support, and the circular magnetic field generating device is connected to the magnetic field controller through a first wire to adjust the parameters of the magnetic field;

[0007] Two sliding contact fixtures are respectively mounted on baffles on both sides of the base bracket;

[0008] The material to be tested is fixed between two sliding contact fixtures, and the sliding contact fixtures clamp the material to be tested through a sliding contact structure;

[0009] The constant current source is connected to the two ends of the material to be tested through the second wire to form a closed loop. When the current passes through the material to be tested, an Ampere force is generated;

[0010] The constant current source provides a constant current to the material to be tested and also has an overcurrent protection function.

[0011] Furthermore, a tension-compression bidirectional force sensor is installed on the outside of the baffle to ensure that its force measuring axis is consistent with the loading direction of the material to be tested. The force sensed by the tension-compression bidirectional force sensor is used to assist in verifying the loading force on the material calculated according to the Ampere force formula.

[0012] Furthermore, the baffles on both sides of the base bracket are provided with grooves for installing the sliding contact fixture.

[0013] Furthermore, a position sensor is installed on the outer side of the baffle to measure the displacement of the sliding contact fixture.

[0014] Furthermore, the position sensor is a photoelectric encoder or a laser sensor.

[0015] Furthermore, a temperature sensor is installed on the constant current source to monitor temperature changes in real time.

[0016] Furthermore, the temperature sensor is a thermocouple or an RTD temperature sensor.

[0017] Furthermore, the contact surface between the upper clamp and the lower clamp of the sliding contact clamp adopts a slide rail structure or a roller structure, allowing the sliding contact clamp to slide in a specific direction to adjust the clamping force or position.

[0018] The present invention also discloses a method for using a material fatigue damage measuring device based on Ampere force loading, comprising the following steps: fixing a base bracket on a test bench; connecting a constant current source to both ends of a material to be tested via a wire to form a closed loop; after the magnetic field controller is powered on, an iron ring on a circular magnetic field generating device generates a magnetic field, and the magnetic field strength B is measured to ensure that the magnetic field in the loading area is uniform; current is passed through the material to be tested, so that the material to be tested is subjected to the action of the Ampere force; and finally, the amount of fatigue damage is obtained through a formula.

[0019] Furthermore, the fatigue damage amount is obtained by the formula. The specific process is: the cross-sectional area is calculated by measuring the diameter d of the material (6) and the formula, that is:

[0020] S=πd 2 / 4 (1)

[0021] The Ampere force is calculated by the formula:

[0022] F=I*L*B*sinθ(2)

[0023] Where, F is the Ampere force, I is the current intensity, L is the effective length of the conductor in the magnetic field, and θ is the angle between the current direction and the magnetic field direction;

[0024] The design makes the current direction perpendicular to the magnetic field direction, then sinθ=1, and formula (2) is simplified to:

[0025] F = I * L * B (3);

[0026] Using the force F and the material cross-sectional area S obtained from formula (3), calculate the material stress:

[0027] σ=F / S(4)

[0028] According to the SN curve theory, calculate the fatigue life of the material to be tested:

[0029] N=C / σ m (5)

[0030] Where C,m is the fatigue characteristic parameter of the material to be tested;

[0031] According to Miner's damage accumulation theory, the fatigue damage is calculated as:

[0032] D=N / n0(6)

[0033] Where n0 is the current cycle number, N is the theoretical fatigue life; the damage amount D indicates the damage progress of the material during the loading process: when D<1, the material has not failed; when D=1, the material reaches fatigue failure;

[0034] Substituting formula (6) into the equation, the final fatigue damage is:

[0035]

[0036] The material fatigue damage measurement device and method based on Ampere force loading of the present invention have the following advantages:

[0037] The present invention adopts the material fatigue damage measurement principle based on Ampere force loading, combines a constant current source, a magnetic field controller, and other core components, and is implemented by constant current loading, uniform magnetic field control, and other methods. Finally, after measurement and data analysis, the fatigue damage amount of the material to be measured is obtained. The present invention can accurately calculate the stress and fatigue damage of the material under the action of the Ampere force through precise current and magnetic field control, combined with the calculation formula of the Ampere force. The present invention can also accurately sense the stress of the material through the use of a tension and compression bidirectional force sensor, solving the problem of how to accurately measure the loading force in a complex electromagnetic environment. The present invention can predict the fatigue life of the material and calculate the amount of damage through the Ampere force formula, the SN curve and the Miner damage accumulation theory, solving the problem of how to accurately calculate the fatigue of the material through current and magnetic field loading. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 A block diagram of the fatigue damage measurement device of the present invention is provided;

[0039] Figure 2 It is a schematic diagram of the fatigue damage measurement device of the present invention;

[0040] Explanation of the markings in the figure: 1. Base bracket; 2. Magnetic field controller; 3. First wire; 4. Sliding contact fixture; 5. Circular magnetic field generating device; 6. Material to be tested; 7. Tension and compression bidirectional force sensor; 8. Second wire; 9. Constant current source. DETAILED DESCRIPTION

[0041] In order to better understand the purpose, structure and function of the present invention, the following is a further detailed description of a material fatigue damage measurement device and method based on Ampere force loading of the present invention in conjunction with the accompanying drawings.

[0042] A material fatigue damage measurement device based on Ampere force loading. Figure 1 As shown: it includes a base bracket 1; baffles are provided on both sides of the top plate of the base bracket 1;

[0043] The circular magnetic field generating device 5 is fixed on the top plate of the base support 1, and the circular magnetic field generating device 5 is connected to the magnetic field controller 2 through the first wire 3 to adjust the parameters of the magnetic field;

[0044] Two sliding contact fixtures 4 are respectively mounted on baffles on both sides of the base bracket 1;

[0045] The material to be tested 6 is fixed between two sliding contact fixtures 4, and the sliding contact fixtures 4 clamp the material to be tested 6 through a sliding contact structure;

[0046] The constant current source 9 is connected to both ends of the material to be tested 6 through the second wire 8 to form a closed loop. When the current passes through the material to be tested 6, an Ampere force is generated;

[0047] The constant current source 9 provides a constant current to the material to be tested 6 and also has an overcurrent protection function;

[0048] Install the tension and compression bidirectional force sensor 7 on the outside of the baffle to ensure that its force measuring axis is consistent with the loading direction of the material 6 to be tested. The force sensed by the tension and compression bidirectional force sensor 7 is used to assist in verifying the loading force calculated by the Ampere force formula. During the experiment, a Gauss meter is also used.

[0049] To assemble the experimental instrument, first fix the base bracket 1 firmly on the experimental table to ensure that it is horizontal and stable. This will allow each supporting point of the base bracket to be evenly stressed to prevent the device from shaking or tilting during loading. Fix the magnetic field controller 2 on the base bracket (such as Figure 2As shown), it is convenient for subsequent operations. The magnetic field controller 2 is an energized device. After being energized, the iron ring on the circular magnetic field generating device 5 can generate a magnetic field. The magnetic field strength B is measured with a Gaussmeter to ensure that the magnetic field in the loading area is uniform. Use the first wire 3 to connect the magnetic field controller 2 to the circular magnetic field generating device 5. Check the contact of the wire to ensure that there is no looseness. The magnetic field controller 2 is used to control the connection and disconnection of the circular magnetic field generating device 5 to ensure the controllability of the magnetic field during the experiment. Ensure that the wire is well insulated to avoid short circuits. Fix the circular magnetic field generating device 5 in an appropriate position on the base bracket so that it can surround the material to be tested 6. Adjust the position of the device to ensure that the material to be tested is in the central area of ​​the circular magnetic field to obtain a uniform magnetic field distribution. The circular magnetic field design can provide a stable and uniform magnetic field, maximize the uniformity of the loading force, and improve the experimental accuracy. Use a Gaussmeter to check the magnetic field strength and uniformity to ensure the stability of the magnetic field in the loading area.

[0050] Fix the sliding contact fixture 4 at both ends of the material to be tested 6 and contact it with the second wire 8 connected to the constant current source 9, while ensuring good conductive contact. Adjust the clamping force of the sliding contact fixture 4 to ensure that the material can be fixed and allowed to deform freely during loading. Check whether the sliding contact fixture 4 is in full contact with the material to prevent current instability. Fix the material to be tested between the sliding contact fixtures 4 to ensure that the material remains horizontal. Adjust the position of the sliding contact fixture 4 so that the effective length of the material is in the central area of ​​the magnetic field. Check whether the material is perpendicular to the direction of the magnetic field to ensure that the geometric relationship in the Ampere force formula holds. Connect the constant current source 9 to both ends of the material to be tested through the second wire 8. Adjust the output current of the constant current source 9 to the preset value to ensure that the current direction is perpendicular to the direction of the magnetic field. The constant current source 9 provides a stable current to ensure that the loading force is constant and avoid the experimental results being affected by current fluctuations. Check the closure of the circuit to ensure that the output current of the constant current source 9 is stable. The connection of the second wire 8 needs to be tight to avoid interruption of the experiment due to poor contact.

[0051] A tension and compression bidirectional force sensor 7 is used because it can measure the force of the material in both the tensile and compressive directions at the same time. This means that it can provide a more comprehensive measurement when the direction of the force is uncertain or may change during the loading process. A boss is provided on the outer side of the baffle, and the tension and compression bidirectional force sensor 7 is mounted on the boss on the outer side of the baffle, such as Figure 2As shown, ensure that its measuring direction is consistent with the force direction of the material to be tested. Calibrate the tension and compression bidirectional force sensor 7 to ensure that its zero point data is accurate. The tension and compression bidirectional force sensor 7 does not directly measure the internal force of the material, but senses the reaction force of the material through the sliding contact fixture 4, and indirectly derives the Ampere force of the material to be tested based on the balance of the two forces. In this way, accurate material force monitoring can be achieved. At the same time, ensure that the axis of the tension and compression bidirectional force sensor 7 is completely aligned with the loading direction, and the tension and compression bidirectional force sensor 7 and the base bracket 1 need to be insulated to prevent the current from passing through the tension and compression bidirectional force sensor 7 or the bracket part to affect the measurement.

[0052] After everything is installed, turn on the constant current source 2 and set the constant current value; turn on the magnetic field controller 3 to generate a uniform constant magnetic field; the tension and compression bidirectional force sensor 7 starts to record the loading force and monitor the experimental data in real time.

[0053] During the experiment, check the equipment regularly to see if it is operating normally, such as whether the output of the constant current source 2 is stable, and use a Gauss meter to check the magnetic field strength and uniformity to ensure the magnetic field stability in the loading area. Make sure there is no strong electromagnetic interference in the surrounding environment to avoid affecting the operation of the tension and compression bidirectional force sensor 7 or the constant current source 2.

[0054] The present invention reduces the uncertainty caused by the current fluctuation and magnetic field unevenness that may occur in the equipment during the experiment by designing monitoring measures during the experiment, such as a Gauss meter, and ensures the stability and reliability of the experimental results.

[0055] The following is an introduction to the process of experiment and formula derivation.

[0056] First, use a Gauss meter to measure the magnetic field strength B of the circular magnetic field generating device 5 to ensure that the magnetic field in the loading area is uniform and record the magnetic induction intensity value. Record the magnetic field strength B and the effective length L of the material to be tested (the length of the conductor located in the magnetic field) to check the material cross-sectional area S, and calculate the cross-sectional area by measuring the material diameter d and the formula, that is:

[0057] S=πd 2 / 4 (1)

[0058] Turn on the constant current source 9 and provide a constant current I to the material 6 to be tested through the wire 8. It is recommended to start with a small current and gradually increase it, and record the loading force under different currents. Make sure that the current direction is perpendicular to the magnetic field direction to meet the Ampere force formula conditions. According to the Ampere force formula:

[0059] F=I*L*B*sinθ(2)

[0060] Among them, F is the Ampere force (N, Newton), I is the current intensity (A, Ampere), L is the effective length of the conductor in the magnetic field (m, meter), B is the magnetic induction intensity (T, Tesla), and θ is the angle between the current direction and the magnetic field direction.

[0061] In the present invention, the current direction is designed to be perpendicular to the magnetic field direction, then sinθ=1, and the formula is simplified to:

[0062] F=I*L*B(3)

[0063] Calculate the Ampere force F on the material to be tested.

[0064] The tension and compression bidirectional force sensor 7 can measure the force value F0 of the material to be tested, and compare it with the calculation result F=I*L*B to verify the accuracy of the experimental system. Under the conditions of constant current and magnetic field, the force value of the material to be tested is recorded.

[0065] Using the loading force F and material cross-sectional area S obtained from the Ampere force formula, calculate the material stress:

[0066] σ=F / S(4)

[0067] The stress σ of the material to be tested under Ampere force loading is calculated using the above formula and compared with the stress σ0=F0 / S obtained by the tension and compression bidirectional force sensor 7. In actual loading, different stress values ​​can be applied by adjusting the current of the constant current source to simulate different loading conditions.

[0068] Next, fatigue loading is performed, and constant current and magnetic field are maintained, and the number of fracture cycles n of the material to be tested under a specific stress σ is recorded. According to the SN curve theory, the fatigue life of the material to be tested is calculated:

[0069] N=C / σ m (5)

[0070] Among them, C,m are fatigue characteristic parameters of the material to be tested, which need to be determined by standard fatigue test, or by reference to literature or material database, which will not be elaborated here. The actual fatigue life N0 and theoretical life N are recorded experimentally to verify the damage accumulation law.

[0071] During the loading process, the number of loading cycles n0 and the damage of the material are recorded at regular intervals. According to Miner's damage accumulation theory, the fatigue damage is calculated:

[0072] D=N / n0(6)

[0073] Where n0 is the current cycle number and N is the theoretical fatigue life. The damage amount D indicates the damage process of the material during loading: when D<1, the material has not failed; when D=1, the material has reached fatigue failure.

[0074] Substituting the above formula into the final fatigue damage is:

[0075]

[0076] At the same time, the theoretical formula can be combined with experimental operation to systematically measure and evaluate material fatigue damage: combining the tension and compression bidirectional force sensor data and the fatigue damage calculation formula, the fatigue damage curve of the material (such as the relationship between the damage amount D and time or the number of cycles n0) is drawn. Then, a high-resolution tracking device is used to observe the damage characteristics of the material to be tested (such as crack initiation and expansion) and compare them with the results of the theoretical formula.

[0077] After the experiment, the constant current source 2 and the magnetic field controller 3 are gradually turned off to avoid damage to the equipment due to sudden power failure.

[0078] It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of the present invention.

Claims

1. A material fatigue damage measurement device based on Ampere force loading, characterized in that: The base bracket (1) comprises a bottom support structure and a top plate, and baffles are provided on both sides of the top plate; The circular magnetic field generating device (5) is fixed on the top plate of the base support (1), and the circular magnetic field generating device (5) is connected to the magnetic field controller (2) through the first wire (3) to adjust the parameters of the magnetic field; Two sliding contact fixtures (4) are respectively mounted on baffles on both sides of the base bracket (1); The material to be tested (6) is fixed between two sliding contact clamps (4), and the sliding contact clamps (4) clamp the material to be tested (6) via a sliding contact structure; The constant current source (9) is connected to two ends of the material to be tested (6) through the second wire (8) to form a closed loop, and when the current passes through the material to be tested (6), an Ampere force is generated; The constant current source (9) provides a constant current for the material to be tested (6) and also has an overcurrent protection function.

2. The material fatigue damage measuring device based on Ampere force loading according to claim 1 is characterized in that: The tension and compression bidirectional force sensor (7) is installed on the outer side of the baffle, ensuring that its force measuring axis is consistent with the loading direction of the material to be measured (6).

3. The material fatigue damage measuring device based on Ampere force loading according to claim 1 is characterized in that: The baffles on both sides of the base support (1) are provided with grooves for mounting the sliding contact fixture (4).

4. The material fatigue damage measuring device based on Ampere force loading according to claim 1 is characterized in that: A position sensor is installed on the outer side of the baffle to monitor the displacement of the sliding contact fixture (4).

5. The material fatigue damage measuring device based on Ampere force loading according to claim 4 is characterized in that: The position sensor is a photoelectric encoder or a laser sensor.

6. The material fatigue damage measuring device based on Ampere force loading according to claim 1 is characterized in that: A temperature sensor is installed on the constant current source (9) to monitor temperature changes in real time.

7. The material fatigue damage measuring device based on Ampere force loading according to claim 6 is characterized in that: The temperature sensor is a thermocouple or RTD temperature sensor.

8. The material fatigue damage measuring device based on Ampere force loading according to claim 1 is characterized in that: The contact surface between the upper clamp and the lower clamp of the sliding contact clamp (4) adopts a slide rail structure or a roller structure, allowing the sliding contact clamp (4) to slide in a specific direction to adjust the clamping force or position.

9. A method for using a material fatigue damage measurement device based on Ampere force loading, characterized in that: A material fatigue damage measuring device based on Ampere force loading as described in any one of claims 1 to 8 is used, characterized in that it includes the following steps: fixing a base bracket (1) on a test bench; connecting a constant current source (9) to two ends of a material to be tested (6) through a second wire (8) to form a closed loop; after the magnetic field controller (2) is powered on, the iron ring on the circular magnetic field generating device (5) generates a magnetic field through the first wire (3), and the magnetic induction intensity B is measured to ensure that the magnetic field in the loading area is uniform; the current passes through the material to be tested (6), so that the material to be tested (6) is subjected to the action of the Ampere force, and finally the fatigue damage amount is obtained through a formula.

10. The method for using the material fatigue damage measurement device based on Ampere force loading according to claim 9, characterized in that: The specific process of obtaining the fatigue damage amount by the formula is as follows: the cross-sectional area is calculated by measuring the diameter d of the material (6) and the formula, namely: S=πd 2 / 4 (1); The Ampere force is calculated by the formula: F = I*L*B*sinθ(2); Among them, F is Ampere force, I is current intensity, L is the effective length of the conductor in the magnetic field, B is the magnetic induction intensity, and θ is the angle between the current direction and the magnetic field direction; The design makes the current direction perpendicular to the magnetic field direction, then sinθ=1, and formula (2) is simplified to: F = I * L * B (3); Using the force F and the material cross-sectional area S obtained from formula (3), calculate the material stress: σ=F / S(4); According to the SN curve theory, calculate the fatigue life of the material to be tested: N=C / σ m (5); Where C,m is the fatigue characteristic parameter of the material to be tested; According to Miner's damage accumulation theory, the fatigue damage is calculated as: D = N / n0 (6); Where n0 is the current cycle number, N is the theoretical fatigue life; the damage amount D indicates the damage progress of the material during the loading process: when D<1, the material has not failed; when D=1, the material reaches fatigue failure; Substituting formula (6) into the equation, the final fatigue damage is:

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