Fatigue life testing device for fiber bragg grating strain sensor

Abstract

The utility model provides a fiber bragg grating strain sensor fatigue life testing device, which comprises an installation frame, a fiber bragg grating strain sensor, a fiber bragg grating strain sensor and a fiber bragg grating strain sensor, the first test clamp is fixed on the vertical edge of the rectangular frame, and a jaw of the first test clamp faces the stand column in the horizontal direction; the up-and-down reciprocating motion mechanism is mounted on the stand column and reciprocates up and down in the vertical direction; and the second test clamp is fixed on the up-down reciprocating mechanism, a jaw of the second test clamp faces the first test clamp in the horizontal direction, and when the fixed end and the test end of the fiber bragg grating strain sensor are clamped on the first test clamp and the second test clamp respectively, the fiber bragg grating strain sensor is kept in a horizontal state. The device can simulate the dynamic stress change of the sensor in an actual working environment, so that the fatigue life of the fiber grating strain sensor is accurately evaluated, and the effectiveness and accuracy of test data are ensured.

Description

Technical Field

[0001] This utility model relates to the field of sensor testing technology, and in particular to a fatigue life testing device for fiber optic strain sensors. Background Technology

[0002] Fiber Bragg grating strain sensors are primarily used to monitor the stress state of structural components and are widely applied in key fields such as wind power generation, civil engineering, aerospace, and machinery manufacturing. However, in complex and variable real-world working environments, fiber Bragg grating strain sensors may experience performance degradation or even failure due to factors such as material fatigue and temperature fluctuations. As a core component in structural health monitoring and mechanical performance testing, the long-term stability and lifespan of fiber Bragg grating strain sensors are key indicators for evaluating their performance. However, existing testing devices struggle to achieve precise control over testing conditions, resulting in inaccurate analysis results and failing to fully meet the requirements for reliability and stability testing of fiber Bragg grating strain sensors within their expected lifespan. Therefore, developing a testing device capable of accurately predicting and evaluating the lifespan of fiber Bragg grating strain sensors is of paramount importance. Summary of the Invention

[0003] This invention provides a fatigue life testing device for fiber optic strain sensors. This device can simulate the dynamic stress changes in the actual working environment of the sensor, thereby accurately evaluating the fatigue life of the fiber optic strain sensor and ensuring the validity and accuracy of the test data.

[0004] To solve the above-mentioned technical problems, the technical solution of this utility model is as follows:

[0005] A fatigue life testing device for fiber optic strain sensors, comprising:

[0006] The mounting frame includes a rectangular frame and columns fixed inside the rectangular frame, with the columns perpendicular to the horizontal side of the rectangular frame.

[0007] Test fixture one is fixed to the vertical side of the rectangular frame, and the jaws of test fixture one are horizontal and facing the column;

[0008] A reciprocating motion mechanism, which is mounted on a column and moves vertically up and down;

[0009] Test fixture two is fixed on the up-and-down reciprocating moving mechanism and moves up and down with the up-and-down reciprocating moving mechanism. The jaws of test fixture two are horizontal and face test fixture one. The initial position of the jaws of test fixture two is on the same horizontal line as the jaws of test fixture one. This ensures that when the fixed end and the test end of the fiber optic strain sensor are clamped on test fixture one and test fixture two respectively, the fiber optic strain sensor remains in a horizontal state.

[0010] The inner walls of the four corners of the rectangular frame are reinforced with corner brackets.

[0011] The test fixture is a manual precision flat-jaw pliers.

[0012] Both the jaws of test fixture one and the jaws of test fixture two are equipped with buffer protective sleeves around their inner sides.

[0013] The reciprocating motion mechanism includes a fixed plate, a drive motor, a first swing arm, a second swing arm, a push rod, a slide rail, and an adjustable power supply. The fixed plate is fixed to the column, the slide rail is fitted onto the push rod, and the slide rail is fixedly connected to the fixed plate, allowing the push rod to slide vertically within the slide rail. One end of the first swing arm is fixedly connected to the output shaft of the drive motor, and the other end of the first swing arm is rotatably connected to one end of the second swing arm. The other end of the second swing arm is rotatably connected to the bottom end of the push rod. The drive motor is connected to the adjustable power supply, which controls the speed of the drive motor. When the drive motor operates, it drives the first swing arm to rotate, thereby causing the push rod to reciprocate vertically. The second test fixture is fixed to the top of the push rod.

[0014] The first and second swing arms are rotatably connected by a first rotating shaft, and the second swing arm and the push rod are rotatably connected by a second rotating shaft. Both the first and second rotating shafts are fixedly connected to the fixed plate.

[0015] The adjustable speed power supply is a frequency converter connected to the power supply.

[0016] The second test fixture consists of a clamp body.

[0017] The fiber Bragg grating strain sensor is connected to the data processing module via a fiber Bragg grating demodulator. The fiber Bragg grating demodulator records the strain value of the strain sensor and transmits it to the data processing module for processing. The data processing module monitors the strain changes of the fiber Bragg grating sensor.

[0018] Two test fixtures are provided for each of the test fixtures. The two test fixtures are fixed to the two vertical sides of the rectangular frame, and the two test fixtures are fixed to the up-and-down reciprocating moving mechanism and move up and down with the up-and-down reciprocating moving mechanism.

[0019] Compared with the prior art, the beneficial effects of this utility model are: (1) The fiber optic strain sensor fatigue life testing device provided by this utility model clamps the fiber optic strain sensor by using a fixed test fixture one and a test fixture two that can move up and down, thereby driving the test end of the fiber optic strain sensor to move up and down. This can simulate the dynamic stress change in the actual working environment of the sensor, thereby accurately evaluating the fatigue life of the fiber optic strain sensor and ensuring the validity and accuracy of the test data.

[0020] (2) The fiber optic strain sensor fatigue life testing device provided by this utility model includes an installation frame, a test fixture one, an up-and-down reciprocating moving mechanism, a test fixture two, and a data analysis module. The overall structure is simple and stable, ensuring the stability of the test data.

[0021] (3) The fiber optic strain sensor fatigue life testing device provided by this utility model can control the strain value and frequency during the test of the fiber optic strain sensor, accurately control the test conditions of the fiber optic strain sensor, and can perform customized testing of fiber optic strain sensors in specific application scenarios. Attached Figure Description

[0022] Figure 1 A schematic diagram of the fiber optic strain sensor fatigue life testing device provided in Example 1 Figure 1 ;

[0023] Figure 2 A schematic diagram of the fiber optic strain sensor fatigue life testing device provided in Example 1 Figure 2 ;

[0024] Figure 3 This is a schematic diagram illustrating the change in strain of the fiber Bragg grating sensor over test time in Example 1, as monitored by the data processing module.

[0025] In the figure, 11-rectangular frame, 12-column, 13-corner bracket, 2-test fixture one, 21-base, 22-clamp body one, 23-lead screw, 24-handle, 31-fixed plate, 32-drive motor, 33-swing arm one, 34-swing arm two, 35-push rod, 36-slide groove, 37-adjustable speed power supply, 38-rotating shaft one, 39-rotating shaft two, 4-test fixture two, 5-fiber optic grating strain sensor. Detailed Implementation

[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0027] Example 1

[0028] The overall structure of the fiber optic strain sensor fatigue life testing device provided in this embodiment is as follows: Figure 1 and Figure 2 As shown, it includes an installation frame, test fixture 1 2, a reciprocating up-and-down moving mechanism, and test fixture 2 4.

[0029] The mounting frame includes a rectangular frame 11 and columns 12 fixed within the rectangular frame, with the columns perpendicular to the horizontal sides of the rectangular frame. The inner walls at the four corners of the rectangular frame are reinforced with corner brackets 13 to enhance structural stability. Specifically, the rectangular frame is made of aluminum profiles with a cross-sectional dimension of 30mm × 90mm, the columns have a cross-sectional dimension of 30mm × 30mm, and the corner brackets have a dimension of 30mm × 30mm. The mounting frame is the core support system of the fiber optic strain sensor fatigue life testing device, ensuring structural stability and reliability during the testing process. By adjusting the horizontal position of the columns, the horizontal distance between test fixture one and test fixture two can be adjusted to accommodate test pieces of different specifications, ensuring the flexibility and accuracy of the test.

[0030] Test fixture one is fixedly connected to the vertical side of the rectangular frame by bolts, and the jaws of test fixture one are horizontal and facing the column; specifically, test fixture one is a manual precision flat-jaw pliers, which consists of a base 21, a clamp body 22, a lead screw 23 and a crank handle 24. The manual precision flat-jaw pliers are existing products, and their structure will not be described in detail here.

[0031] A reciprocating motion mechanism is mounted on a column and moves vertically up and down. Specifically, the reciprocating motion mechanism includes a fixed plate 31, a drive motor 32, a first swing arm 33, a second swing arm 34, a push rod 35, a slide rail 36, and a variable speed power supply 37. The fixed plate is fixed to the column, the slide rail is fitted onto the push rod, and the slide rail is fixedly connected to the fixed plate, allowing the push rod to slide vertically within the slide rail. One end of the first swing arm is fixedly connected to the output shaft of the drive motor, and the other end of the first swing arm is rotatably connected to one end of the second swing arm. The other end of the second swing arm is rotatably connected to the bottom end of the push rod. The drive motor is connected to the variable speed power supply, which controls the speed of the drive motor. The drive motor drives the first swing arm to rotate. The slide rail ensures that the push rod can only move linearly in the vertical direction, allowing the second swing arm to convert the rotational motion of the first swing arm into reciprocating linear motion and drive the push rod to move vertically up and down. Further, the variable speed power supply is a frequency converter connected to a power source. Furthermore, swing arm one and swing arm two are rotatably connected by pivot shaft one 38, and swing arm two and push rod are rotatably connected by pivot shaft two 39. Both pivot shaft one and pivot shaft two are fixedly connected to the fixed plate.

[0032] Test fixture two is fixed to the reciprocating moving mechanism and moves up and down with the mechanism. The jaws of test fixture two are horizontal and face test fixture one. The initial position of the jaws of test fixture two is on the same horizontal line as the jaws of test fixture one. This ensures that the fiber optic strain sensor 5 remains horizontal when its fixed end and test end are clamped on test fixture one and test fixture two, respectively. Specifically, test fixture two is fixed to the top of the push rod and moves up and down vertically with the push rod. Specifically, test fixture two consists of a clamp body two. The jaw height of clamp body two matches the height of the test piece to ensure that the test piece can remain properly fixed and centered throughout the test.

[0033] During testing, the fiber Bragg grating strain sensor is first clamped onto test fixture one and test fixture two. Initially, the fiber Bragg grating strain sensor is in a horizontal position. The speed of the drive motor is controlled by an adjustable power supply, causing the motor to rotate, which in turn drives the push rod to move up and down reciprocally within the groove. The push rod pushes one end of the fiber Bragg grating strain sensor, causing it to continuously swing up and down, simulating the dynamic stress changes in the sensor's actual working environment. This allows for real-time monitoring of the tensile and contractile properties of the fiber Bragg grating strain sensor, thereby achieving the fatigue life test. Specifically, the jaws of test fixture one and test fixture two are equipped with cushioning protective sleeves, such as rubber or foam, around their inner sides to prevent damage to the test piece.

[0034] In this embodiment, the fiber Bragg grating strain sensor is connected to the data processing module via a fiber Bragg grating demodulator. The fiber Bragg grating demodulator records the strain value of the strain sensor and transmits it to the data processing module for processing. The data processing module monitors the strain change of the fiber Bragg grating sensor.

[0035] The testing steps of the fiber optic strain sensor fatigue life testing device provided in this embodiment are as follows: (1) Place the entire testing device in an environment with pre-set temperature and humidity conditions to ensure that the environment can stably maintain the required temperature and humidity parameters in order to simulate the actual working conditions and provide accurate and reliable conditions for testing.

[0036] (2) Clamp the fixed end and the test end of the fiber optic strain sensor to be tested into the jaws of test fixture one and test fixture two, respectively; specifically, gently place the narrower end of the fiber optic strain sensor into the jaws of test fixture two, ensuring that an appropriate amount of space is reserved above and below, so that the jaws just contact the sensor but do not apply excessive pressure; then place the other end of the fiber optic strain sensor horizontally into the jaws of test fixture one, and push the jaws to move by rotating the screw until the contact layer of the jaws is tightly attached to the surface of the strain sensor;

[0037] (3) Before performing a life test on the fiber Bragg grating strain sensor, it is necessary to ensure that the fiber Bragg grating strain sensor is kept horizontal; in addition, the reciprocating swing amplitude is adjusted by changing the position of the push rod in the slide groove, and the stroke of the fiber Bragg grating strain sensor is adjusted. In this embodiment, the stroke is set to ±2500με.

[0038] Before testing, place the fiber optic strain sensor on a horizontal surface for a few seconds to ensure it is in a stable state. Then, use a fiber optic demodulator to test the strain of the fiber optic strain sensor and record the data at this time as a reference. This initial strain value is the equilibrium value, which is used for comparative analysis of strain changes during subsequent testing.

[0039] (4) Before the test, the current of the drive motor is changed by the adjustable speed power supply to accurately set the measurement frequency. In this embodiment, the measurement frequency is ensured to be stable at 1 time / s (1Hz).

[0040] (5) During the test, the strain of the fiber optic strain sensor is recorded every 24 hours, and the data are compared to observe the strain change pattern.

[0041] (6) The data processing module continuously monitors the strain changes of the current fiber Bragg grating sensor, such as... Figure 3 As shown, if the sensor remains stable throughout the test, the data processing module will repeat step (5) until the predetermined fatigue test time T is reached; when the test time T is reached, the test stops and it is determined that the fiber grating sensor has reached its expected lifespan; if the fiber grating sensor becomes unstable or malfunctions during the test, the data processing module will immediately detect this abnormality and terminate the test, at which point it is determined that the sensor has failed to reach its expected lifespan.

[0042] Example 2

[0043] The structure of the fiber optic strain sensor fatigue life testing device provided in this embodiment is basically the same as that in Embodiment 1. The only difference is that in this embodiment, there are two test fixtures and two test fixtures. The two test fixtures are fixed on the two vertical sides of the rectangular frame, and the two test fixtures are fixed on the up-and-down reciprocating moving mechanism and move up and down with the up-and-down reciprocating moving mechanism at the same time, so that the fatigue life test of two fiber optic strain sensors can be performed at the same time.

Claims

1. A fiber grating strain sensor fatigue life testing device, characterized in that: The fiber grating strain sensor fatigue life test device comprises: A mounting frame comprising a rectangular frame and a stand fixed in the rectangular frame, the stand being perpendicular to the horizontal edges of the rectangular frame; A first test clamp fixed to the vertical edge of the rectangular frame, the jaws of the first test clamp being in the horizontal direction and facing the stand; An up-and-down reciprocating mechanism mounted on the stand and reciprocating up and down in the vertical direction; A second test clamp fixed to the up-and-down reciprocating mechanism and reciprocating up and down with the up-and-down reciprocating mechanism, the jaws of the second test clamp being in the horizontal direction and facing the first test clamp, and the initial positions of the jaws of the second test clamp being on the same horizontal line as the jaws of the first test clamp, so as to ensure that the fiber grating strain sensor remains horizontal when the fixed end and the test end of the fiber grating strain sensor are clamped on the first test clamp and the second test clamp respectively.

2. The fiber Bragg grating strain sensor fatigue life test apparatus of claim 1, wherein: The inner walls of the four corners of the rectangular frame are reinforced by corner braces.

3. The fiber grating strain sensor fatigue life test apparatus of claim 1, wherein: The first test clamp is a manual precision flat clamp.

4. The fiber grating strain sensor fatigue life test apparatus of claim 1, wherein: The inner sides of the jaws of the first test clamp and the second test clamp are provided with buffer protective sleeves.

5. The fiber grating strain sensor fatigue life test apparatus of claim 1, wherein: The up-and-down reciprocating mechanism comprises a fixed plate, a driving motor, a swing arm one, a swing arm two, a push rod, a sliding groove, and an adjustable speed power supply, wherein the fixed plate is fixed to the stand, the sliding groove is sleeved on the push rod, the sliding groove is fixedly connected with the fixed plate, the push rod slides in the sliding groove in the vertical direction, one end of the swing arm one is fixedly connected with the output shaft of the driving motor, the other end of the swing arm one is rotatably connected with one end of the swing arm two, the other end of the swing arm two is rotatably connected with the bottom end of the push rod, the driving motor is connected with the adjustable speed power supply, the adjustable speed power supply controls the rotating speed of the driving motor, the driving motor works to drive the swing arm one to rotate, thereby driving the push rod to reciprocate up and down in the vertical direction, and the second test clamp is fixed to the top end of the push rod.

6. The fiber Bragg grating strain sensor fatigue life test apparatus of claim 5, wherein: The swing arm one and the swing arm two are rotatably connected through a rotating shaft one, and the swing arm two and the push rod are rotatably connected through a rotating shaft two, both the rotating shaft one and the rotating shaft two being fixedly connected with the fixed plate.

7. The fiber grating strain sensor fatigue life test apparatus of claim 5, wherein: The adjustable speed power supply is a frequency converter connected with a power supply.

8. The fiber grating strain sensor fatigue life test apparatus of claim 1, wherein: The second test clamp is composed of one clamp body two.

9. The fiber grating strain sensor fatigue life test apparatus of claim 1, wherein: The fiber grating strain sensor is connected with a data processing module through a fiber grating demodulator, the fiber grating demodulator records the strain value of the strain sensor and transmits it to the data processing module for processing, and the data processing module monitors the strain change of the fiber grating sensor.

10. The fiber grating strain sensor fatigue life test apparatus of claim 1, wherein: Both the first test clamp and the second test clamp are provided with two, the two first test clamps being fixed to the two vertical edges of the rectangular frame, and the two second test clamps being fixed to the up-and-down reciprocating mechanism and reciprocating up and down with the up-and-down reciprocating mechanism simultaneously.

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