Multi-axis loading device and method for composite material structure

Abstract

The invention belongs to the technical field of helicopter fatigue tests, and discloses a multi-axis loading device and method for a composite material structure, and the device comprises a first clamping assembly which enables one end of a test piece to be fixedly connected to a test bench; the second clamping assembly is connected with the other end of the test piece and is connected with the bearing through an extension rod; the bending torsion loading mechanism is provided with a force transmission shaft and single fork lug assemblies, the force transmission shaft is vertically connected with the extension rod, and the two ends of the force transmission shaft are connected with the single fork lug assemblies respectively; and the centrifugal loading mechanism is provided with a centrifugal force transmission rod, one end of the centrifugal force transmission rod is connected with the bearing seat, and the other end is connected with the test bed. According to the invention, the problem that multi-axis loading is difficult to carry out when a fatigue test is carried out on the flexible beam is solved, and the fatigue performance of the helicopter composite material structure is explored.

Description

Technical Field

[0001] This invention belongs to the field of aircraft power system design technology, specifically relating to a multi-axis loading device and method for composite material structures. Background Technology

[0002] The 115V fixed-frequency AC power system, as the primary power supply system for helicopter platforms, involves switching between multiple power sources during operation, making high reliability crucial. During helicopter flight, the power system must maintain stable operation at all times to ensure a continuous and reliable power supply to various critical equipment. Any power supply failure could lead to serious consequences, even jeopardizing the entire aircraft's flight safety. Therefore, a highly reliable power supply system plays a decisive role in the overall flight safety of the aircraft.

[0003] In traditional AC power systems, conversion-type three-phase AC contactors are commonly used. However, during the energized switching process, these contactors may experience arcing, leading to burn-out and damage. Therefore, there is an urgent need to develop a new type of multi-power conversion circuit. Summary of the Invention

[0004] Purpose of the invention: To address the difficulty of multiaxial loading in fatigue testing of flexible beams, this invention provides a multiaxial loading device and method for composite material structures, thereby solving the lack of multiaxial loading devices and methods for helicopter composite material structures and exploring the fatigue performance of helicopter composite material structures.

[0005] To address the above-mentioned technical issues, the present invention provides the following technical solution: In a first aspect, the present invention provides a multiaxial loading device for composite material structures, comprising: The first clamping assembly securely connects one end of the test piece to the test bench; The second clamping assembly is connected to the other end of the test piece and is connected to the bearing via an extension rod; A bending and torsion loading mechanism, which has a force transmission shaft and a single fork lug assembly, wherein the force transmission shaft is perpendicularly connected to the extension rod and the two ends are respectively connected to the single fork lug assembly; A centrifugal loading mechanism has a centrifugal force transmission rod, one end of which is connected to a bearing seat and the other end is connected to a test bench.

[0006] As a further technical solution of the present invention: the first clamping assembly includes a cover plate and a fixed joint. The test piece is divided into a fixed end and a loading end. The fixed end of the test piece is connected to the fixed joint by bolts. The front end face of the rear boss of the fixed joint is connected to the cover plate. The cover plate is designed with evenly distributed bolt holes. The cover plate is connected to the test bench by bolts. When the bolts connected to the cover plate are loosened, the fixed joint can rotate around the axis.

[0007] As a further technical solution of the present invention: the second clamping assembly includes a force transmission fork lug, the loading end of the test piece is connected to the force transmission fork lug by bolts, and the force transmission fork lug is connected in sequence to the force transmission shaft, the intermediate bushing, the tapered roller bearing, the outer bushing, and the tightening nut.

[0008] As a further technical solution of the present invention: the force transmission fork ear passes through the center hole of the force transmission shaft, the center hole of the intermediate bushing is connected to the force transmission fork ear, one side of the outer side of the intermediate bushing is connected to the center hole surface of the force transmission shaft, and the other end face is connected to the inner ring end face of the tapered roller bearing. The other end face of the inner side of the tapered roller bearing is connected to the outer bushing, and the outer bushing is then connected to the tightening nut.

[0009] As a further technical solution of the present invention: the outer ring surface of the tapered roller bearing is connected to the inner side of the bearing housing, and the other end face of the outer side of the bearing housing is connected to the centrifugal force transmission rod by machining evenly distributed bolt holes. The end of the centrifugal force transmission rod is machined with threads and connected to the corresponding centrifugal force loading servo mechanism.

[0010] As a further technical solution of the present invention: the two ends of the force transmission shaft are respectively connected to single fork lug assemblies, the two single fork lug assemblies are symmetrically distributed and are equidistant from the center line of the force transmission fork lug, and the two single fork lug assemblies are then connected to the corresponding bending moment loading servo mechanism.

[0011] As a further technical solution of the present invention: the single fork lug assembly consists of a single fork lug and a joint bearing. The joint bearing can rotate and swing at any angle without adding additional bending moment during the test, thus ensuring that the test sensor is not damaged abnormally.

[0012] As a further technical solution of the present invention: a key structure is machined on the part of the force transmission fork ear that is connected to the force transmission shaft, and a corresponding keyway is machined on the force transmission shaft to ensure that they can cooperate with each other, prevent rotation during the test, and effectively transmit the test load.

[0013] Secondly, the present invention provides a multiaxial loading method for composite material structures, which includes the following steps: Step 1: Before the test specimen is installed, first attach the patches to the corresponding positions according to the requirements of the test task book and test outline; Step 2: After completing Step 1, the test specimen is calibrated and installed. The test specimen is installed on a dedicated calibration platform and calibrated in the three directions of swinging, oscillation, and torsion. The linear relationship between bending moment, torque and strain on the corresponding cross section is established to obtain the swing calibration coefficient Kb, oscillation calibration coefficient Kt, and torsion calibration coefficient Km of the corresponding cross section. Step 3: After completing Step 2, remove the test piece from the dedicated calibration stand and then install the test piece onto the test stand. First, connect the cover plate and the fixing joint to the fixing port of the test stand. Step 4: Connect the force transmission fork lug, single fork lug assembly, force transmission shaft, bearing housing, outer bushing, tapered roller bearing, centrifugal force transmission rod, intermediate bushing, and tightening nut in sequence. Connect the single fork lug assembly to the bending moment loading servo mechanism, and connect the centrifugal force transmission rod to the centrifugal force loading servo mechanism. Step 5: After completing steps 3 and 4, the strain value of the test piece is zeroed. Then, the two ends of the test piece are connected to the mounting and fixing joints and the force transmission fork lugs respectively, and the corresponding bolts are tightened according to the tightening torque requirements. Step 6: After completing Step 5, proceed to test debugging. First, apply centrifugal force to the test piece through the centrifugal force loading servo mechanism. Adjust the bending moment loading servo mechanism of the single fork lug assembly on both sides to input the same displacement so that the test piece does not deflect and the output strain value of the test piece is minimized. This state is the initial state of test loading. Step 7: Rotate the test piece by a certain angle. After tightening the cover plate at the fixed end of the test piece with bolts, apply centrifugal force to the test piece using the centrifugal force loading servo mechanism. Adjust the displacement input of the bending moment loading servo mechanism of the single fork lug assembly on both sides, collect the test strain data, and obtain the swing, swing bending moment and torque loads by using the relationship between the swing calibration coefficient Kb, the oscillation calibration coefficient Kt, the torsion calibration coefficient Km and the strain. If the swing, swing bending moment and torque loads just meet the test requirements, a fatigue test is performed. When the test load does not meet the load requirements, loosen the bolts on the cover plate, rotate the installation angle of the test piece, and repeat the above loading steps. The installation angle of the test piece and the moment loading servo mechanism are adjusted to load the test piece by controlling the displacement until the moment loads of the swinging, oscillating, and torsional loads meet the test requirements. In the above debugging process, the installation angle adjustment mainly changes the proportion of the test piece load in the swinging and oscillating directions, and the displacement control mainly changes the magnitude of the test piece load in the swinging, oscillating, and torsional directions. If the test does not require the application of torsional load, the input displacements of the moment loading servo mechanisms of the two single fork lug assemblies are equal and in the same direction. If the test does not require the application of loads in the swinging and oscillating directions, the input displacements of the moment loading servo mechanisms of the two single fork lug assemblies are equal and in opposite directions. Step 8: After continuously adjusting in step 7 to obtain the test load that meets the test requirements, record the installation angle and displacement that meet the requirements after adjustment, and load according to this installation angle and displacement to enter the fatigue test. During the test, the installation angle and control displacement remain unchanged. Design the protection limit and test error in the control system, observe the load and test conditions on the test piece according to the inspection requirements of the test requirements, and terminate the test according to the test termination conditions.

[0014] In summary, the beneficial effects of the present invention are as follows: 1. This invention is simple and practical, with low processing and maintenance costs, and solves the problem of multiaxial loading fatigue testing technology for composite material structures.

[0015] 2. The device of this invention can apply four types of loads—flapping, oscillation, centrifugal force, and torsion—to flexible beams and blades of composite materials to simulate the stress state of a helicopter. It can obtain the fatigue performance and failure location of flexible beams and blades of composite materials under multi-directional loads, providing reliable data support for fatigue life assessment of composite material structures.

[0016] 3. This invention is not limited to flexible beams made of composite materials, but can also be applied to other multiaxial loading devices and methods, such as those for metal materials and rubber material structures.

[0017] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0018] Figure 1 This is an isometric view of the multi-axis loading device for composite material structures of the present invention.

[0019] Figure 2 This is a front view of the multi-axis loading device for composite material structures according to the present invention.

[0020] Figure 3 This is a cross-sectional view of the multi-axis loading device for composite material structures according to the present invention.

[0021] Figure 4 This is an isometric view of the force transmission shaft of the present invention.

[0022] Figure 5 This is an isometric view of the force transmission fork lug of the present invention.

[0023] Figure 6 This is an isometric view of the bearing housing of the present invention.

[0024] Figure 7 This is an isometric view of the centrifugal force transmission rod of the present invention.

[0025] Figure 8 This is an isometric view of the single-fork lug assembly of the present invention.

[0026] The attached figures are labeled as follows: cover plate 1, fixed joint 2, test piece 3, force transmission fork lug 4, single fork lug assembly 5, force transmission shaft 6, bearing seat 7, centrifugal force transmission rod 8, tightening nut 9, tapered roller bearing 10, outer bushing 11, and intermediate bushing 12. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be described in more detail below with reference to the accompanying drawings.

[0028] In the accompanying drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are some, but not all, of the embodiments of the present invention.

[0029] The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0030] The following is in conjunction with the appendix Figure 1-8 The embodiments of the present invention will be described in detail below.

[0031] Example 1 This invention discloses a multi-axis loading device for composite material structures. The device mainly comprises: a cover plate 1, a fixed joint 2, a test piece 3, a force transmission fork lug 4, a single fork lug assembly 5, a force transmission shaft 6, a bearing seat 7, a centrifugal force transmission rod 8, a tightening nut 9, a tapered roller bearing 10, an outer bushing 11, and an intermediate bushing 12.

[0032] The test piece 3 is divided into a fixed end and a loading end. The fixed end of the test piece 3 is connected to the fixed joint 2 by bolts. The front end face of the rear boss of the fixed joint 2 is connected to the cover plate 1. The cover plate 1 is designed with evenly distributed bolt holes. The cover plate 1 is connected to the test bench by bolts. When the bolts connected to the cover plate 1 are loosened, the fixed joint 2 can rotate around the axis.

[0033] The loading end of test piece 3 is connected to the force transmission fork lug 4 by bolts. The force transmission fork lug 4 is connected in sequence to the force transmission shaft 6, the intermediate bushing 12, the tapered roller bearing 10, the outer bushing 11, and the tightening nut 9.

[0034] The force transmission fork lug 4 passes through the center hole of the force transmission shaft 6. The center hole of the intermediate bushing 12 is connected to the force transmission fork lug 4. One side of the intermediate bushing 12 is connected to the center hole surface of the force transmission shaft 6, and the other end face is connected to the end face of the inner ring of the tapered roller bearing 10. The other end face of the inner sleeve of the tapered roller bearing 10 is connected to the outer bushing 11. The outer bushing 11 is then connected to the tightening nut 9.

[0035] The outer ring surface of the tapered roller bearing 10 is connected to the inner side of the bearing housing 7. The other end face of the outer side of the bearing housing 7 is connected to the centrifugal force transmission rod 8 through machined and distributed bolt holes. The end of the centrifugal force transmission rod 8 is threaded and connected to the corresponding centrifugal force loading servo mechanism.

[0036] The two ends of the force transmission shaft 6 are connected to the single fork lug 5 respectively. The two single fork lug 5 are symmetrically distributed and are equidistant from the center line of the force transmission fork lug 4. The two single fork lug 5 are then connected to the corresponding bending moment loading servo mechanism.

[0037] The single fork lug assembly 5 consists of a single fork lug and a spherical bearing. The spherical bearing can rotate and swing at any angle without adding extra bending moment during the test, ensuring that the test sensor is not damaged abnormally.

[0038] The part of the force transmission fork lug 4 that is connected to the force transmission shaft 6 is machined with a key structure, and the force transmission shaft 6 is machined with a corresponding keyway to ensure that they can fit together, prevent rotation during the test, and effectively transmit the test load.

[0039] Example 2 This invention discloses a multiaxial loading method for composite material structures, and its experimental procedure is as follows: Step 1: Before installing test piece 3, first attach the patches to the corresponding positions according to the requirements of the test task book and test outline; After completing steps 2 and 1, the test specimen 3 is calibrated and installed. The test specimen 3 is installed on a dedicated calibration platform, and the test specimen 3 is calibrated in the three directions of swinging, oscillation, and torsion. The linear relationship between bending moment, torque and strain on the corresponding cross section is established, and the swing calibration coefficient Kb, oscillation calibration coefficient Kt, and torsion calibration coefficient Km of the corresponding cross section are obtained. Step 3: After completing step 2, remove test piece 3 from the dedicated calibration platform and then install test piece 3 onto the test platform. First, connect cover plate 1 and fixing joint 2 to the fixing inlet of the test platform. Step 4: Connect the force transmission fork lug 4, single fork lug assembly 5, force transmission shaft 6, bearing seat 7, outer bushing 11, tapered roller bearing 10, centrifugal force transmission rod 8, intermediate bushing 12, and tightening nut 9 in sequence. Connect the single fork lug assembly 5 to the bending moment loading servo mechanism and connect the centrifugal force transmission rod 8 to the centrifugal force loading servo mechanism. Step 5: After completing steps 3 and 4, the strain value of test piece 3 is zeroed. Then, the two ends of test piece 3 are connected to the mounting and fixing joint 2 and the force transmission fork lug 4 respectively, and the corresponding bolts are tightened according to the tightening torque requirements. After completing steps 6 and 5, proceed to the test debugging. First, apply centrifugal force to the test piece 3 through the centrifugal force loading servo mechanism. Adjust the bending moment loading servo mechanism of the single fork lug assembly 5 on both sides to input the same displacement so that the test piece 3 does not deflect and the output strain value of the test piece 3 is the minimum. This state is the initial state of the test loading. Step 7: Rotate the test piece 3 by a certain angle. After tightening the cover plate 1 at the fixed end of the test piece with bolts, the centrifugal force loading servo mechanism applies centrifugal force to the test piece 3. Adjust the displacement of the bending moment loading servo mechanism of the single fork lug assembly 5 on both sides, collect the test strain data, and obtain the swing, swing bending moment and torque loads by using the relationship between the swing calibration coefficient Kb, the oscillation calibration coefficient Kt, the torsion calibration coefficient Km and the strain. If the swing, oscillation bending moment and torque load just meet the test requirements, a fatigue test is performed. When the test load does not meet the load requirements, loosen the bolts on the cover plate 2, rotate the installation angle of the test piece, and repeat the above loading steps. The installation angle of the test specimen and the moment loading servo mechanism are adjusted by controlling the displacement to load until the moment loads of the swinging, oscillating, and torsional loads meet the test requirements. In the above-mentioned debugging process, the installation angle adjustment mainly changes the proportion of the test specimen load in the swinging and oscillating directions, and the displacement control mainly changes the magnitude of the test specimen load in the swinging, oscillating, and torsional directions. If the test does not require the application of torsional load, the input displacements of the moment loading servo mechanisms of the two single fork lug assemblies 5 are equal and in the same direction. If the test does not require the application of loads in the swinging and oscillating directions, the input displacements of the moment loading servo mechanisms of the two single fork lug assemblies 5 are equal and in opposite directions.

[0040] Step 8: After continuously adjusting in step 7 to obtain the test load that meets the test requirements, record the installation angle and displacement that meet the requirements after adjustment, and load according to this installation angle and displacement to enter the fatigue test. During the test, the installation angle and control displacement remain unchanged. Design the protection limit and test error in the control system, observe the load and test conditions on the test piece according to the inspection requirements of the test requirements, and terminate the test according to the test termination conditions.

[0041] Thus, the objective of this invention has been achieved.

[0042] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A multiaxial loading device for composite material structures, characterized in that, include: The first clamping assembly securely connects one end of the test piece to the test bench; The second clamping assembly is connected to the other end of the test piece and is connected to the bearing via an extension rod; A bending and torsion loading mechanism, which has a force transmission shaft and a single fork lug assembly, wherein the force transmission shaft is perpendicularly connected to the extension rod and the two ends are respectively connected to the single fork lug assembly; A centrifugal loading mechanism has a centrifugal force transmission rod, one end of which is connected to a bearing seat and the other end is connected to a test bench.

2. The multi-axis loading device for composite material structures according to claim 1, characterized in that, The first clamping assembly includes a cover plate and a fixed joint. The test piece is divided into a fixed end and a loading end. The fixed end of the test piece is connected to the fixed joint by bolts. The front face of the rear boss of the fixed joint is connected to the cover plate. The cover plate is designed with evenly distributed bolt holes. The cover plate is connected to the test bench by bolts. When the bolts connected to the cover plate are loosened, the fixed joint can rotate around the axis.

3. The multi-axis loading device for composite material structures according to claim 2, characterized in that, The second clamping assembly includes a force transmission fork lug. The loading end of the test piece is connected to the force transmission fork lug by bolts. The force transmission fork lug is connected in sequence to the force transmission shaft, intermediate bushing, tapered roller bearing, outer bushing, and tightening nut.

4. The multi-axis loading device for composite material structures according to claim 3, characterized in that, The force transmission fork lug passes through the center hole of the force transmission shaft. The center hole of the intermediate bushing is connected to the force transmission fork lug. One side of the outer side of the intermediate bushing is connected to the center hole surface of the force transmission shaft, and the other end is connected to the inner ring end face of the tapered roller bearing. The other end face of the inner side of the tapered roller bearing is connected to the outer bushing. The outer bushing is then connected to the tightening nut.

5. The multi-axis loading device for composite material structures according to claim 4, characterized in that, The outer ring of the tapered roller bearing is connected to the inner side of the bearing housing. The other end face of the outer side of the bearing housing is connected to the centrifugal force transmission rod through machined and distributed bolt holes. The end of the centrifugal force transmission rod is threaded and connected to the corresponding centrifugal force loading servo mechanism.

6. The multi-axis loading device for composite material structures according to claim 5, characterized in that, The two ends of the force transmission shaft are connected to single fork lug assemblies. The two single fork lug assemblies are symmetrically distributed and are equidistant from the center line of the force transmission fork lug. The two single fork lug assemblies are then connected to the corresponding bending moment loading servo mechanism.

7. The multi-axis loading device for composite material structures according to claim 6, characterized in that, The single-fork lug assembly consists of a single fork lug and a spherical bearing. The spherical bearing can rotate and swing at any angle without adding extra bending moment during the test, ensuring that the test sensor is not damaged abnormally.

8. The multi-axis loading device for composite material structures according to claim 7, characterized in that, The part of the force transmission fork ear that connects to the force transmission shaft is machined with a key structure, and the force transmission shaft is machined with a corresponding keyway to ensure that they can fit together, prevent rotation during the test, and effectively transmit the test load.

9. A multiaxial loading method for composite material structures, characterized in that, Includes the following steps: Step 1: Before the test specimen is installed, first attach the patches to the corresponding positions according to the requirements of the test task book and test outline; Step 2: After completing Step 1, the test specimen is calibrated and installed. The test specimen is installed on a dedicated calibration platform and calibrated in the three directions of swinging, oscillation, and torsion. The linear relationship between bending moment, torque and strain on the corresponding cross section is established to obtain the swing calibration coefficient Kb, oscillation calibration coefficient Kt, and torsion calibration coefficient Km of the corresponding cross section. Step 3: After completing Step 2, remove the test piece from the dedicated calibration stand and then install the test piece onto the test stand. First, connect the cover plate and the fixing joint to the fixing port of the test stand. Step 4: Connect the force transmission fork lug, single fork lug assembly, force transmission shaft, bearing housing, outer bushing, tapered roller bearing, centrifugal force transmission rod, intermediate bushing, and tightening nut in sequence. Connect the single fork lug assembly to the bending moment loading servo mechanism, and connect the centrifugal force transmission rod to the centrifugal force loading servo mechanism. Step 5: After completing steps 3 and 4, the strain value of the test piece is zeroed. Then, the two ends of the test piece are connected to the mounting and fixing joints and the force transmission fork lugs respectively, and the corresponding bolts are tightened according to the tightening torque requirements. Step 6: After completing Step 5, proceed to test debugging. First, apply centrifugal force to the test piece through the centrifugal force loading servo mechanism. Adjust the bending moment loading servo mechanism of the single fork lug assembly on both sides to input the same displacement so that the test piece does not deflect and the output strain value of the test piece is minimized. This state is the initial state of test loading. Step 7: Rotate the test piece by a certain angle. After tightening the cover plate at the fixed end of the test piece with bolts, apply centrifugal force to the test piece using the centrifugal force loading servo mechanism. Adjust the displacement input of the bending moment loading servo mechanism of the single fork lug assembly on both sides, collect the test strain data, and obtain the swing, swing bending moment and torque loads by using the relationship between the swing calibration coefficient Kb, the oscillation calibration coefficient Kt, the torsion calibration coefficient Km and the strain. If the swing, swing bending moment and torque loads just meet the test requirements, a fatigue test is performed. When the test load does not meet the load requirements, loosen the bolts on the cover plate, rotate the installation angle of the test piece, and repeat the above loading steps. The installation angle of the test piece and the moment loading servo mechanism are adjusted to load the test piece by controlling the displacement until the moment loads of the swinging, oscillating, and torsional loads meet the test requirements. In the above debugging process, the installation angle adjustment mainly changes the proportion of the test piece load in the swinging and oscillating directions, and the displacement control mainly changes the magnitude of the test piece load in the swinging, oscillating, and torsional directions. If the test does not require the application of torsional load, the input displacements of the moment loading servo mechanisms of the two single fork lug assemblies are equal and in the same direction. If the test does not require the application of loads in the swinging and oscillating directions, the input displacements of the moment loading servo mechanisms of the two single fork lug assemblies are equal and in opposite directions. Step 8: After continuously adjusting in step 7 to obtain the test load that meets the test requirements, record the installation angle and displacement that meet the requirements after adjustment, and load according to this installation angle and displacement to enter the fatigue test. During the test, the installation angle and control displacement remain unchanged. Design the protection limit and test error in the control system, observe the load and test conditions on the test piece according to the inspection requirements of the test requirements, and terminate the test according to the test termination conditions.

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