Piezoelectric stacked fast reflector flexible hinge fatigue test device

Abstract

The invention relates to the field of fatigue testing technology, and solves the problems of axial deviation, temperature drift, steady-state error and complex control process in existing fatigue testing. The testing device includes a base, a fixture and a column, a load loading mechanism and a piezoelectric stack driver; the fixture is installed on the base, the test piece is fixed on the base by the fixture, and the load loading mechanism is placed above the test piece; the alternating load is applied to the test piece 4 by the piezoelectric stack driver, and the static and dynamic force data are extracted by the load sensor to realize fatigue detection and testing. According to the preset state of the system, the present invention can simulate low-frequency or high-frequency alternating loading conditions, and the structure is simple and small in size, and it does not generate or accept magnetic interference at all. It is more suitable for alternating loading and high-frequency high-cycle fatigue performance testing of small and precision components than traditional electromagnetic drive high-frequency fatigue testing machines.

Description

Technical Field

[0001] The present invention relates to the technical field of fatigue testing, and in particular to a piezoelectric stacked fast reflector flexible hinge fatigue testing device. Background Art

[0002] Beam pointing control technology is a crucial component of modern precision guidance, space laser communications, and aerial imaging systems. Fast reflectors are one of the core devices enabling fast, high-precision beam pointing control. However, the system operates at high frequencies, and the flexure hinge support, as a key component, is subject to periodic forces and is susceptible to fatigue damage, such as fracture. Therefore, fatigue life verification of the flexure hinge system is essential.

[0003] Fatigue testing machines are widely used to determine the fatigue properties, fatigue life, pre-crack formation, and crack propagation of metal, non-metal, and alloy components under cyclic alternating stress. Traditional fatigue testing machines have four main drive modes: mechanical, pneumatic, electro-hydraulic servo, and electromagnetic resonance. Mechanical and pneumatic fatigue testing machines have lower loading frequencies, while electro-hydraulic servo and electromagnetic resonance are currently the most commonly used high-frequency loading methods. However, these methods all have loading capacities exceeding 500N and are expensive.

[0004] Currently, there are three types of driving force sources: two-point piezoelectric stack drive, three-point piezoelectric stack drive, and four-point piezoelectric stack drive. Considering the precision requirements of the fast reflector system and the need for easy maintenance, the two-point solution has many drawbacks, such as axial deviation, temperature drift, and large steady-state error, and generally cannot meet the positioning requirements of this design. Although the three-point drive solution has the advantage of high precision, the control process is too complex. Before achieving the target control, the program must make very accurate calculations, which places high demands on programming. The four-point drive solution not only has the advantages of high precision, but also has low control difficulty, simple and feasible program implementation, and higher control accuracy than the previous solutions. In addition, the four-point drive fast reflector (FSM) is easier to maintain.

[0005] Therefore, the fatigue testing device described in this application uses a four-point piezoelectric stack as its driving force to apply an alternating load to the hinge housing, while simultaneously adjusting the voltage to control the magnitude of the applied alternating load. This effectively addresses the fatigue testing challenges associated with high-frequency, low-load components and is of great significance for promoting technological innovation and advancement in the fatigue testing field. Summary of the Invention

[0006] In order to solve the problems of axial deviation, temperature drift, steady-state error and complex control process in existing fatigue tests, the present invention provides a piezoelectric stacked fast reflector flexible hinge fatigue testing device.

[0007] A piezoelectric stack fast reflector flexible hinge fatigue test device, the test device comprising a base, a fixture and a column, and also comprising a load loading mechanism and a piezoelectric stack driver;

[0008] The fixture is installed on the base, the test piece is fixed on the base through the fixture, and a load loading mechanism is placed above the test piece;

[0009] The load loading mechanism includes a tray, a sleeve base plate, a connecting sleeve, a sleeve cover plate and a locking screw;

[0010] The sleeve base plate is fixed on the tray. The sleeve base plate is provided with four pre-set grooves for positioning the piezoelectric stack drivers. After the four piezoelectric stack drivers are placed in the pre-set grooves, they are wrapped with the connecting sleeve 503 and fixed to the sleeve cover plate on the connecting sleeve by bolts.

[0011] The load-applying mechanism is fixed to the column by means of locking screws;

[0012] The piezoelectric stack driver comprises a threaded base, a driver housing, a load contact, a piezoelectric stack and a preloaded spring;

[0013] The piezoelectric stack is encapsulated in the driver housing through a threaded base. A load contact is placed at the front end of the piezoelectric stack and is pre-tightened with a pre-tightening spring. When the piezoelectric stack is energized, the load contact performs reciprocating telescopic motion, applying an alternating load to the test piece, and the load sensor extracts static and dynamic force data to achieve fatigue detection and testing.

[0014] Beneficial effects of the present invention:

[0015] The fatigue testing device described in this invention utilizes a four-point piezoelectric stack to drive the mirror, eliminating the need for Z-axis movement of the mirror center and eliminating the need for Z-axis error compensation. Consistent preload on the mirror eliminates preload deflection. This structure achieves deflection about the X and Y axes through the push-pull operation of two pairs of piezoelectric stack actuators, requiring only two variables to be controlled, eliminating the need for coordinate transformation to obtain the drive displacement and deflection angle. Furthermore, depending on the system's preset state, it can simulate low- or high-frequency alternating loading conditions. This simple and compact structure neither generates nor receives magnetic interference, making it more suitable for alternating loading and high-frequency, high-cycle fatigue performance testing of small and precision components than conventional electromagnetically driven high-frequency fatigue testing machines. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a three-dimensional front view of the piezoelectric stacked fast reflector flexible hinge fatigue testing device of the present invention;

[0017] Figure 2A right side view of the piezoelectric stacked fast reflector flexible hinge fatigue testing device of the present invention and a partial cross-sectional view of the tray and the piezoelectric stack driver;

[0018] Figure 3 Schematic diagram of the internal structure of the piezoelectric stack driver;

[0019] Figure 4 It is a structural schematic diagram of the load loading mechanism 5;

[0020] Figure 5 Schematic diagram of the structure of the clamp 3.

[0021] In the figure, 1. rubber foot, 2. base, 301. fixture back plate, 302. fixture slide, 303. left caliper, 304. caliper column, 305. caliper scale frame, 306. right caliper, 4. test piece, 5. load loading mechanism, 501. tray, 502. sleeve bottom plate, 503. connecting sleeve, 504. sleeve cover, 505. locking screw, 6. column, 7. piezoelectric stack driver, 701. threaded base, 702. driver housing, 703. load contact, 704. piezoelectric stack, 705. preload spring, 8. load sensor. DETAILED DESCRIPTION

[0022] Combine Figure 1-Figure 5 To describe this embodiment, a piezoelectric stacked fast reflector flexible hinge fatigue testing device includes a rubber foot 1, a base 2, a fixture 3, a test piece 4, a load loading mechanism 5, a column 6, a piezoelectric stack driver 7 and a load sensor 8.

[0023] The rubber foot 1 is bolted to the underside of the base 2, supporting the tabletop and providing vibration damping. A slot is provided on the left side of the base 2, housing the left-side clamp 303. This allows the clamp's left-right distance and vertical height to be adjusted based on the diameter and height of the test piece 4. Similarly, a right-side clamp 306 is mounted on the right side of the base 2, securing the test piece 4 securely to the tabletop of the base 2 with the clamps on both sides. A load-applying mechanism 5 is positioned above the test piece 4 and secured to the upright 6 by tightening the locking screw 505. When the locking screw 505 is tightened, the initial load is converted into a static load on the test piece 4, contributing to fatigue testing of the test piece 4. Consequently, when an external alternating excitation voltage is applied to the piezoelectric stack actuator 7, its deformation applies an alternating load to the test piece 4 via the load contacts 703. Static and dynamic force data are then collected by the load sensor, enabling fatigue testing and detection.

[0024] like Figure 3 As shown, Figure 3The internal structure of the piezoelectric stack driver 7 is shown. The piezoelectric stack driver 7 is configured to perform alternating dynamic loading on a specimen, and includes a threaded base 701 , a driver housing 702 , a load contact 703 , a piezoelectric stack 704 , and a preload spring 705 .

[0025] The piezoelectric stack 704 is enclosed in the driver housing 702 via a threaded base 701. A load contact 703 is placed at the front of the piezoelectric stack 704 and preloaded with a preload spring 705. This allows the load contact 703 to reciprocate and extend when the piezoelectric stack 704 is energized, applying an alternating load to the test piece 4. A load sensor 8 is positioned at the bottom of the test piece 4 and secured with a locking screw. The load sensor extracts static and dynamic force data from the test piece 4, enabling reciprocating tensile fatigue testing and inspection of the test piece.

[0026] like Figure 4 As shown, Figure 4 Figure 5 shows the internal structure of the load-loading mechanism 5. The load-loading mechanism 5 is designed to pre-statically load the specimen and includes a tray 501, a sleeve base plate 502, a connecting sleeve 503, a sleeve cover plate 504, and locking screws 505. The load-loading mechanism 5 is designed to apply alternating loads to the specimen. During installation, the sleeve base plate 502 is first bolted to the tray 501. The sleeve base plate 502 has four pre-set slots for positioning the piezoelectric stack actuators 7. After the four piezoelectric stack actuators 7 are positioned, they are wrapped with the connecting sleeve 503 and bolted to the sleeve cover plate 504. This completes the packaging of the four piezoelectric stack actuators 7. Finally, the load-loading mechanism 5 is secured to the column 6 via locking screws 506. This completes the load-loading mechanism 5 assembly.

[0027] like Figure 5 As shown, Figure 5 The diagram shows the structure of the fixture 3. The left caliper structure includes a fixture backing plate 301, a fixture slide 302, and a left caliper 303; the right caliper structure includes a caliper column 304, a caliper scale frame 305, and a right caliper 306. The left caliper structure of the fixture 3 is mounted on the slide, and the right caliper structure is mounted on the base opposite the left caliper structure. The left and right caliper structures are used to adjust the left-right distance and vertical height of the fixture according to the diameter and height of the test piece 4, which is then fixed to the base 2.

[0028] The clamp support plate 301 is fixed to the base slide groove by T-bolts. Such a connection allows the position of the left caliper 303 to be adjusted left and right according to the diameter of the test piece 4. The clamp support plate 301 is also provided with a slide groove for placing the clamp slide 302, which can be tightened by T-bolts. In this way, the connection of the left structure of the clamp is completed, and the selection of the position height of the clamp slide 302 needs to be determined according to the height of the test piece 4; the right structure of the clamp is also a mechanism that can achieve left and right distance and height adjustment. The caliper column 304 is fixed to the table surface of the base 2 by bolts to support the caliper scale frame 305. The caliper scale frame 305 can achieve up and down height adjustment by pre-tightening bolts. A threaded hole is provided at the cantilever end of the caliper scale frame 305 for connecting the right caliper 306. The pre-tightening of the right caliper 306 connected by bolts realizes the left and right movement of the right caliper structure; the left and right distance and up and down height adjustment of the right caliper structure are also determined according to the diameter and height of the test piece 4.

[0029] The piezoelectric stack fast-reflecting mirror flexure hinge fatigue testing device described in this embodiment utilizes a piezoelectric stack driver as the driving force source and is equipped with a load-applying mechanism 5. During operation, these mechanisms, along with the test specimen 4 and the fixture 3, form the device's excitation system. The load-applying mechanism 5 encapsulates the piezoelectric stack driver 7 via a connecting sleeve 503 and a sleeve cover 504. The piezoelectric stack driver 7 applies a load to the test specimen 4 via load contacts 703, which is then held in place by the fixture 3. Consequently, when an external alternating excitation voltage is applied to the piezoelectric stack driver 7, its deformation is converted into an alternating load that acts on the specimen 4, thereby achieving fatigue testing of the fast-reflecting mirror flexure hinge.

[0030] In this embodiment, the piezoelectric stack driver 7 uses a single-layer wafer as the driving source. Typically, piezoelectric wafers are relatively thick, and achieving the desired deformation with this configuration typically requires an applied voltage of 1000V or even higher. However, a piezoelectric stack can be driven at a lower voltage, typically below 150V. By applying voltage to each wafer separately and then superimposing them, a larger combined deformation can be achieved, meeting the requirements for displacement accuracy and good stability in the micron range or even lower.

Claims

1. A piezoelectric stacked fast reflector flexible hinge fatigue testing device, comprising a base (2), a fixture (3) and a column (6); wherein: Also included is a load loading mechanism (5) and a piezoelectric stack driver (7); The fixture (3) is mounted on the base (2), the test piece (4) is fixed on the base (2) via the fixture (3), and a load loading mechanism (5) is placed above the test piece (4); The load loading mechanism (5) comprises a tray (501), a sleeve base plate (502), a connecting sleeve (503), a sleeve cover plate (504) and a locking screw (505); The sleeve base plate (502) is fixed on the tray (501), and four pre-set grooves for positioning the piezoelectric stack drivers (7) are provided on the sleeve base plate (502). After the four piezoelectric stack drivers (7) are placed in the pre-set grooves, they are wrapped with a connecting sleeve (503) and the sleeve cover plate (504) is fixed to the connecting sleeve (503) by bolts. The load loading mechanism (5) is fixed to the column (6) via a locking screw (505); The piezoelectric stack driver (7) comprises a threaded base (701), a driver housing (702), a load contact (703), a piezoelectric stack (704) and a preloaded spring (705); The piezoelectric stack (704) is encapsulated in the driver housing (702) via a threaded base (701), a load contact (703) is placed at the front end of the piezoelectric stack (704), and the load contact (703) is pre-tightened by a pre-tightening spring (705). When the piezoelectric stack (704) is energized and working, the load contact (703) performs reciprocating telescopic motion, applies an alternating load to the test piece (4), and the load sensor (8) extracts static and dynamic force data to achieve fatigue detection and testing; A slide groove is provided on the left side of the base (2), and a left caliper structure of the fixture (3) is installed on the slide groove, and a right caliper structure is installed on the base opposite to the left caliper structure; the left and right distances and the upper and lower heights of the fixture are adjusted according to the diameter and height of the test piece (4) through the left and right caliper structures of the fixture, and then the test piece (4) is fixed on the base (2); The left caliper structure includes a clamp backing plate (301), a clamp slide plate (302) and a left caliper (303); the right caliper structure includes a caliper column (304), a caliper scale frame (305) and a right caliper (306); The clamp support plate (301) is fixed to the slide groove of the base (2) by T-bolts, and a slide groove is provided on the clamp support plate (301) for fixing the clamp slide plate (302); The caliper column (304) is fixed to the table of the base (2) by bolts, and the caliper frame (305) is adjusted in height up and down on the caliper column (304) by pre-tightening bolts. A threaded hole for connecting the right caliper (306) is provided at the cantilever end of the caliper frame (305), and the right caliper (306) is pre-tightened by the bolt-connected right caliper (306) to achieve left and right movement; the left and right distance and the up and down height of the right caliper (306) are adjusted according to the diameter and height of the test piece (4); The load sensor (8) is arranged at the bottom of the tested piece (4) and is fixed by a locking screw.

2. The piezoelectric stacked fast reflector flexible hinge fatigue testing device according to claim 1, characterized in that: The selection of the position height of the fixture slide (302) is determined according to the height of the tested piece (4).

3. The piezoelectric stacked fast reflector flexible hinge fatigue testing device according to claim 1, characterized in that: It also includes a rubber foot (1), which is connected to the bottom of the base (2) by bolts.

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