Multi-technology combined in-situ characterization instrument and method under complex load

Abstract

The invention discloses a multi-technology combined in-situ characterization instrument and method under a complex load, and belongs to the field of precise scientific instruments. Comprising a complex load loading module and an in-situ characterization module, the complex load loading module comprises a rigid frame, a longitudinally-loaded tension-compression unit and a transversely-loaded bending unit, the moving end of the tension-compression unit is used for being connected with the end of a tested sample, the fixed end of the tension-compression unit is connected with the moving end of the bending unit, and the moving end of the bending unit is connected with the rigid frame. The fixed end of the bending unit is installed on the rigid frame, the bending pressure head is installed on the rigid frame, the bending pressure head corresponds to the middle part of the tested sample, and the in-situ characterization module is used for carrying out in-situ monitoring on the tested sample. According to the invention, the tension / compression and bending loads can be loaded on the tested sample at the same time by using the tension and compression unit and the bending unit, so that the complex load effect is realized, and the in-situ characterization of the tested sample under the complex load is facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of precision scientific instruments, and in particular to an in-situ characterization instrument and method using multiple technologies under complex loads. Background Art

[0002] Fiber-reinforced composite materials have shown broad application prospects in aerospace, civil engineering and other fields due to their excellent high strength, high toughness and lightweight properties. In actual engineering applications, such materials often face complex and changeable load conditions. Taking engineering bamboo (bamboo-based fiber-reinforced composites) as an example, when used as a beam structure, its two ends are constrained and the middle is loaded, which puts it in a complex load state of tension and bending; when used as a column structure, factors such as slight deviations in design or construction and occasional lateral loads may cause it to face a complex stress environment where compression and bending coexist. Similarly, carbon fiber reinforced composites (CFRP) in applications such as aircraft engine fan blades or helicopter flexible beams also need to deal with the combined tensile and bending loads caused by high-speed rotation and airflow impact. However, the current evaluation of the mechanical parameters of fiber-reinforced composites is mostly based on tests under a single load, such as axial tension, compression and bending. Studies have shown that under complex loads, the deformation, damage and failure behavior of materials are significantly different from those under single load conditions. Therefore, relying solely on mechanical parameters under a single load to guide engineering applications may pose serious safety hazards.

[0003] In view of this, developing testing methods and equipment under complex loads is a technical problem faced by this field. Summary of the invention

[0004] The purpose of the present invention is to provide an in-situ characterization instrument and method for combining multiple technologies under complex loads to solve the problems existing in the above-mentioned prior art. By using a tension-compression unit and a bending unit, tensile / compression and bending loads can be simultaneously applied to the test sample, thereby realizing the action of complex loads and facilitating the in-situ characterization of the test sample under complex loads.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] The present invention provides an in-situ characterization instrument for multiple technologies under complex loads, comprising a complex load loading module and an in-situ characterization module, wherein the complex load loading module comprises a rigid frame, a longitudinally loaded tension and compression unit, and a transversely loaded bending unit, wherein the movable end of the tension and compression unit is used to connect the end of a sample to be tested, the fixed end of the tension and compression unit is connected to the movable end of the bending unit, the fixed end of the bending unit is mounted on the rigid frame, and further comprises a bending pressure head mounted on the rigid frame, wherein the bending pressure head corresponds to the middle part of the sample to be tested, and the in-situ characterization module is used to perform in-situ monitoring on the sample to be tested.

[0007] Preferably, the bending unit comprises a transverse telescopic cylinder and a movable frame, the cylinder body of the transverse telescopic cylinder is fixed to the rigid frame, the piston rod of the transverse telescopic cylinder is connected to the movable frame, and the movable frame is rotatably connected to the fixed end of the tension and compression unit.

[0008] Preferably, the movable frame includes a first movable frame and a second movable frame distributed on both sides of the fixed end of the tension and compression unit, the first movable frame and the second movable frame are both slidably connected to the rigid frame, the piston rod of the transverse telescopic cylinder is connected to the first movable frame or the second movable frame, and the transverse telescopic cylinder is arranged at both ends of the test sample in a centrally symmetrical manner with the test sample.

[0009] Preferably, the tension and compression unit includes a longitudinal telescopic cylinder, a force sensor and a clamping body, the cylinder body of the longitudinal telescopic cylinder is rotatably connected to the moving frame, the force sensor is connected between the piston rod of the longitudinal telescopic cylinder and the clamping body, and the clamping body is used to clamp the test sample.

[0010] Preferably, the bending pressure head includes a base and a pressure head end, the base includes legs and an elastic beam connected to the legs, the pressure head end is connected to the middle of the elastic beam, and both sides of the elastic beam are used to install strain gauges.

[0011] Preferably, it further comprises a frame and a transfer module, wherein the fixed end of the transfer module is connected to the frame, the rotating end of the transfer module is connected to the rigid frame, and the rotation center of the transfer module coincides with the axis of the tested sample.

[0012] Preferably, the in-situ characterization module includes a neutron scattering unit, an acoustic emission unit and a digital image correlation unit, the neutron scattering unit and the digital image correlation unit are respectively located behind and in front of the tested sample, the acoustic emission unit is located on the side of the tested sample, and the acoustic emission units are symmetrically arranged up and down along the center of the gauge section of the tested sample.

[0013] Preferably, the digital image correlation unit is located above or below the center of the gauge section of the tested sample, and the digital image correlation unit includes a laterally distributed microscope CCD camera and a standard CCD camera, and a fill light located between or outside the microscope CCD camera and the standard CCD camera, and the shooting angles of the microscope CCD camera and the standard CCD camera are toward the center of the gauge section of the tested sample.

[0014] The present invention also provides a method for in-situ characterization using multiple technologies under complex loads, using the in-situ characterization instrument using multiple technologies under complex loads as described above, comprising the following contents:

[0015] S1. Clamp the test sample on the moving end of the tension and compression unit;

[0016] S2, moving the moving end of the tension and compression unit to apply a tensile / compressive force to the test sample in the axial direction, and maintaining the tensile / compressive force constant after reaching a predetermined tensile / compressive force;

[0017] S3, moving the moving end of the bending unit to drive the end of the tested sample to move toward one side of the bending pressure head, so that the tested sample is bent and deformed at the position of the bending pressure head, and after reaching a predetermined bending force, the bending force is kept constant;

[0018] S4. Using an in-situ characterization module to perform in-situ monitoring on the tested sample.

[0019] Preferably, the in-situ monitoring using the in-situ characterization module in step S4 includes the following:

[0020] A neutron scattering unit is used to monitor the damage information inside the tested sample and to reconstruct a three-dimensional damage image; an acoustic emission unit is used to collect the acoustic emission signal of the damage of the tested sample; and a digital image correlation unit is used to monitor the multi-scale strain information on the surface of the tested sample;

[0021] Carry out multi-mode in-situ information fusion analysis of digital image correlation, acoustic emission and neutron scattering to reveal the multi-scale damage failure mechanism under complex loads.

[0022] Compared with the prior art, the present invention has achieved the following technical effects:

[0023] The present invention utilizes a tension / compression unit and a bending unit to simultaneously load tensile / compression and bending loads on the test sample, thereby realizing complex load action. At the same time, because during bending loading, the bending pressure head remains stationary while the bending unit moves, the position of the tensile / compression loading can be kept the same as the position of the bending loading and is always in the center of the in-situ characterization field of view, thereby facilitating in-situ characterization of the test sample under complex loads.

[0024] Other technical solutions included in the present invention can also achieve the following technical effects:

[0025] Fiber-reinforced composites contain a large number of fibers, thin-walled cells and multi-scale interfaces, which make them exhibit a variety of damage failure modes under complex loads. The present invention combines the neutron scattering unit, the acoustic emission unit acquisition and the digital image correlation unit to fully reveal the multi-scale damage failure mechanism of the tested sample (such as fiber-reinforced composites) under complex loads, which is helpful for optimizing the preparation process of fiber-reinforced composites and improving their performance.

[0026] The multi-technique combined in-situ characterization instrument under complex loads of the present invention is suitable for fiber-reinforced composite materials. According to the instrument of the present invention and the method recorded therein, it is possible to reveal the influence mechanism of complex loads on the ultimate strength and clarify the multi-scale damage failure mechanism under complex loads. This has important practical significance and scientific value for ensuring the service safety of fiber-reinforced composites under complex loads and promoting their large-scale application in the fields of aerospace, civil construction, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0028] Figure 1 It is a schematic diagram of the overall structure of an embodiment of the present invention;

[0029] Figure 2 This is a schematic diagram of the rack structure of an embodiment of the present invention;

[0030] Figure 3 This is a schematic diagram of the structure of an in-situ characterization module according to an embodiment of the present invention;

[0031] Figure 4 This is a schematic diagram of the structure of a digital image correlation unit according to an embodiment of the present invention;

[0032] Figure 5 This is a schematic diagram of the structure of a transfer module according to an embodiment of the present invention;

[0033] Figure 6 This is a schematic diagram of the structure of a complex load loading module according to an embodiment of the present invention;

[0034] Figure 7 This is a schematic diagram of the structure of a bending unit according to an embodiment of the present invention;

[0035] Figure 8 This is a schematic diagram of the structure of the tension and compression unit according to an embodiment of the present invention;

[0036] Fig. 9 This is a schematic diagram of the bending pressure head structure according to an embodiment of the present invention;

[0037] Fig.10 This is a schematic diagram of the indirect measurement principle of bending force according to an embodiment of the present invention;

[0038] Fig.11 It is a schematic diagram showing that the center of the gauge section of the tested sample is always at the center of the in-situ characterization field of view during the complex load loading process of an embodiment of the present invention;

[0039] Fig.12Schematic diagram of the macro and micro strain measurement process according to an embodiment of the present invention;

[0040] Fig.13 Schematic diagram of an in-situ characterization method using multiple techniques under complex loads according to an embodiment of the present invention;

[0041] Among them, 1. rack; 2. in-situ characterization module; 3. transfer module; 4. complex load loading module; 5. tested sample; 101. mounting plate; 102. column; 103. substrate; 104. foot pad; 201. neutron scattering unit; 202. acoustic emission unit 1; 203. acoustic emission unit 2; 204. digital image correlation unit; 20401. microscopic CCD camera; 20402. fill light 1; 20403. fill light Light 2; 20404, standard CCD camera; 20405, bracket; 301, upper rotating assembly; 302, upper conversion support; 303, lower conversion support; 304, lower rotating assembly; 401, bending unit; 402, tension and compression unit; 403, bending pressure head; 404, rigid frame; 405, guide rail; 40101, transverse telescopic cylinder 1; 40110, transverse telescopic cylinder 2; 40108, fixed seat 2; 40114, Fixed seat 1; 40102, clamping plate 1; 40109, clamping plate 2; 40103, first moving frame 1; 40107, first moving frame 2; 40106, second moving frame 2; 40112, second moving frame 1; 40104, bearing 1; 40105, bearing 2; 40111, guide groove 2; 40113, guide groove 1; 40201, longitudinal telescopic cylinder 1; 40210, longitudinal telescopic cylinder 2; 40202, adapter 1; 40209, adapter 2; 40203, force sensor 1; 40208, force sensor 2; 40204, limit screw 1; 40207, limit screw 2; 40211, clamp body 2; 40212, clamp body 1; 40205, cover plate 1; 40206, cover plate 2; 40301, base; 40302, pressure head end; 40303, support leg; 40304, elastic beam; 40305, strain gauge. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] The purpose of the present invention is to provide an in-situ characterization instrument and method for combining multiple technologies under complex loads to solve the problems existing in the prior art. By using a tension-compression unit and a bending unit, tensile / compression and bending loads can be simultaneously applied to the test sample, thereby realizing the action of complex loads and facilitating the in-situ characterization of the test sample under complex loads.

[0044] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0045] like Figures 1 to 13 As shown, the present invention provides an in-situ characterization instrument for multiple technologies under complex loads, including a complex load loading module 4 and an in-situ characterization module 2. The complex load loading module 4 is used to realize load loading in various ways (such as stretching-bending or compression-bending) to simulate a complex force environment, and the in-situ characterization module 2 is used to perform in-situ monitoring of the test sample 5 under load. Specifically, the complex load loading module 4 includes a rigid frame 404, a longitudinally loaded tension and compression unit 402, and a transversely loaded bending unit 401. The longitudinal telescopic cylinder in the tension and compression unit 402 can adopt a linearly moving telescopic cylinder, a linear motor, a lead screw nut and other structural forms. The moving end of the tension and compression unit 402 is used to connect the end of the test sample 5. The tension and compression unit 402 can be set at one end or both ends of the test sample 5. When the tension and compression unit 402 is set at both ends, symmetrical loading can be achieved. At this time, both the loading efficiency can be improved and the in-situ loading of the test sample 5 can be guaranteed. The fixed end of the tension and compression unit 402 is connected to the movable end of the bending unit 401. The transverse telescopic cylinder of the bending unit 401 can adopt a telescopic cylinder that moves linearly, a linear motor, a lead screw nut and other structural forms. The fixed end of the bending unit 401 is installed on the rigid frame 404. It also includes a bending pressure head 403 installed on the rigid frame 404. The bending pressure head 403 corresponds to the middle part of the tested sample 5. When the bending unit 401 is in motion, it can drive the tension and compression unit 402 to move to one side, that is, drive the end of the tested sample 5 to move to one side. Due to the existence of the bending pressure head 403, the tested sample 5 is forced to bend to achieve bending loading. It should be noted that: the bending unit 401 can be set only at one end of the tested sample 5, and the bending loading can be achieved only by the bending unit 401 at one end of the tested sample 5. The bending units 401 can also be set at both ends of the tested sample 5, and the bending units 401 at both ends of the tested sample 5 can achieve synchronous bending loading. The latter can achieve more stable and uniform loading, better achieve in-situ loading, and is the preferred mode of the present invention. After applying a load to the test sample 5, the test sample 5 is monitored in situ through the in-situ characterization module 2. The in-situ characterization module 2 is used to realize multi-scale strain measurement, internal damage evolution process monitoring, damage pattern recognition and damage three-dimensional image reconstruction of the test sample 5, obtain corresponding in-situ monitoring data, and process it.

[0046] The present invention utilizes the tension and compression unit 402 and the bending unit 401 to simultaneously load tensile / compressive and bending loads on the test sample 5, thereby realizing complex load action. At the same time, because the bending pressure head 403 is stationary while the bending unit 401 is in motion during bending loading, the position of tensile / compressive loading can be kept the same as the position of bending loading and always in the center of the in-situ characterization field of view, thereby facilitating in-situ characterization of the test sample 5 under complex loads. The present invention provides a new technology and method for testing and analyzing the mechanical properties of materials under complex and harsh working conditions, which helps to promote the transition of mechanical properties testing technology of fiber-reinforced composites from single load to complex load, and promotes the transformation of in-situ damage characterization technology of fiber-reinforced composites from a single mode to the combination of multiple technologies.

[0047] like Figure 6 and Figure 7 As shown, the bending units 401 at both ends of the test sample 5 are structurally consistent, and can be arranged axially symmetrically or centrally symmetrically. The bending unit 401 arranged at one end is used as an example for explanation, and includes a transverse telescopic cylinder 1 40101 (transverse telescopic cylinder 2 40110) and a moving frame. The cylinder body of the transverse telescopic cylinder 1 40101 (transverse telescopic cylinder 2 40110) can be fixed to the rigid frame 404 through a fixed seat 1 40114 (fixed seat 2 40108) and a clamping plate 1 40102 (clamping plate 2 40109). The piston rod of the transverse telescopic cylinder 1 40101 (transverse telescopic cylinder 2 40110) is connected to the moving frame, and the moving frame is rotatably connected to the fixed end of the tension and compression unit 402. When the transverse telescopic cylinder 1 40101 (transverse telescopic cylinder 2 40110) is in motion, the tension and compression unit 402 can be driven to move laterally through the moving frame.

[0048] Further, the moving frame may include a first moving frame 40103 (first moving frame 40107) and a second moving frame 40112 (second moving frame 40106) distributed on both sides of the fixed end of the tension and compression unit 402. The two can be connected to each other as a whole, or each can be independently connected to the tension and compression unit 402. The former can better maintain the strength and structural stability of the moving frame when the transverse telescopic cylinder 40101 (transverse telescopic cylinder 40110) is in motion. The first moving frame 40103 (first moving frame 40107) and the second moving frame 40112 (second moving frame 40106) are both slidably connected to the guide rail 405 on the rigid frame 404 through the guide groove 40113 (guide groove 40111), and the movement of the moving frame can be guided by the cooperation between the guide groove 40113 (guide groove 40111) and the guide rail 405, so as to further ensure the stability of the system during bending loading. The piston rod of the transverse telescopic cylinder 40101 (transverse telescopic cylinder 40110) can be connected only to the first moving frame 40103 (first moving frame 40107) or only to the second moving frame 40112 (second moving frame 40106). The preferred method is that the transverse telescopic cylinder 40101 and the transverse telescopic cylinder 40110 are arranged symmetrically with the test sample 5 at both ends of the test sample 5. This structural arrangement can effectively suppress the overturning moment occurring during the mechanical loading process and the rotation around the axis, thereby ensuring the accuracy of mechanical testing and in-situ characterization.

[0049] like Figure 6 and Figure 8As shown, the tension and compression units 402 at both ends of the test sample 5 can be consistent in structure and symmetrically arranged at both ends of the test sample 5. The tension and compression unit 402 arranged at one end is illustrated, including a longitudinal telescopic cylinder 1 40201 (longitudinal telescopic cylinder 2 40210), a force sensor 1 40203 (force sensor 2 40208) and a clamp body 1 40212 (clamp body 2 40211). The first moving frame 40103 (the first moving frame 40107) and the second moving frame 40112 (the second moving frame 40106) are respectively rotatably connected with the cylinder body of the longitudinal telescopic cylinder 40201 (the longitudinal telescopic cylinder 40210) through the bearing 40104 (the bearing 40105). The cylinder body of the longitudinal telescopic cylinder 40201 (the longitudinal telescopic cylinder 40210) is provided with a rotating shaft sleeved on the inner ring of the bearing 40104 (the bearing 40105), and is installed by means of interference fit or transition fit. The first moving frame 40103 (the first moving frame 40107) and the second moving frame 40112 (the second moving frame 40106) are provided with through holes for installing the outer ring of the bearing 40104 (the bearing 40105), and are installed by means of interference fit or transition fit. Force sensor 1 40203 (force sensor 2 40208) is connected between the piston rod of longitudinal telescopic cylinder 1 40201 (longitudinal telescopic cylinder 2 40210) and clamp body 1 40212 (clamp body 2 40211), and an adapter 1 40202 (adapter 2 40209) can also be arranged between the piston rod and force sensor 1 40203 (force sensor 2 40208), and the piston rod and adapter 1 40202 (adapter 2 40209) can be connected by internal and external threads, and force sensor 1 40203 (force sensor 2 40208) and clamp body 1 40212 (clamp body 2 40211) can be rigidly connected by studs. The clamp body 1 40212 (clamp body 2 40211) cooperates with the cover plate 1 40205 (cover plate 2 40206) to clamp the test sample 5, and is locked and fixed by the limit screw 1 40204 (limit screw 2 40207), and a locking nut can be added to achieve further locking.

[0050] During the test, a double-cylinder synchronous loading method can be used for tensile / compressive loading, that is, the longitudinal telescopic cylinder 1 40201 and the longitudinal telescopic cylinder 2 40210 arranged symmetrically drive the clamp body 1 40212 and the clamp body 2 40211 to move, thereby applying tensile / compressive force to the test sample 5. The bending pressure head 403 passive contact loading strategy can be used for bending loading, that is, the transverse telescopic cylinder 1 40101 and the transverse telescopic cylinder 2 40110 arranged symmetrically at the center drive the first moving frame 1 40103 and the first moving frame 2 40107 to move respectively, and transmit the load to the tension and compression unit 402 through the rotating shaft, thereby applying bending force to the test sample 5.

[0051] like Fig.11 As shown, the tension and compression unit 402 and the bending unit 401 work together to achieve complex load loading of tension-bending and compression-bending. The ingenious combination of the dual-cylinder synchronous loading method and the passive contact loading method of the bending pressure head 403 can effectively suppress the position deviation of the center of the gauge length of the tested sample 5 during the complex load loading process, ensuring that the center of the gauge length section of the tested sample 5 is always in the center of the in-situ characterization field, thereby providing important guarantee for subsequent multi-parameter in-situ characterization.

[0052] Combination Fig. 9 As shown, the bending pressure head 403 may include a base 40301 and a pressure head end 40302, and the whole is in a "T" shape. The base 40301 includes a leg 40303 and an elastic beam 40304 connected to the leg 40303. The leg 40303 and the elastic beam 40304 can be obtained by slotting a rectangular block at the bottom, or by being connected in parts. The leg 40303 is fixed to the rigid frame 404 by screws, and the pressure head end 40302 is connected to the middle of the elastic beam 40304. Both sides of the elastic beam 40304 are used to install strain gauges 40305. Four strain gauges 40305 can be attached to the elastic beam 40304. The calibration coefficient K is established by calibrating the relationship between the bending force and the average strain measured by the four strain gauges 40305. During the test, the bending force can be obtained by collecting the average strain and combining the calibration coefficient K.

[0053] The average strain is calculated as follows:

[0054]

[0055] Among them, ε ave represents the average strain value.

[0056] The bending force calibration formula is as follows:

[0057] F B =Kε ave

[0058] Among them, F B Represents bending force.

[0059] like Figure 1 , Figure 2 and Figure 5As shown, it also includes a frame 1 and a transfer module 3, and the transfer module 3 is used to realize the precise rotation and positioning of the complex load loading module 4. The transfer module 3 above the test sample 5 includes an upper rotating component 301 and an upper conversion support 302, the upper rotating component 301 is connected to the upper part of the frame 1 as a fixed end, and the upper conversion support 302 is connected to the upper part of the rigid frame 404 as a rotating end; the transfer module 3 below the test sample 5 includes a lower rotating component 304 and a lower conversion support 303, the lower rotating component 304 is connected to the lower part of the frame 1 as a fixed end, and the lower conversion support 303 is connected to the lower part of the rigid frame 404 as a rotating end. The rotation center of the transfer module 3 can coincide with the axis of the test sample 5. When the transfer module 3 drives the test sample 5 to rotate, it can rotate around the axis of the test sample 5.

[0060] like Figure 2 As shown, the rack 1 may include a base plate 103, two columns 102 mounted on the base plate 103, and a mounting plate 101 located at the top of the columns 102 and connected to the columns 102, and a foot pad 104 is provided at the bottom of the base plate 103. The upper rotating assembly 301 may be connected to the mounting plate 101 by screws, and the lower rotating assembly 304 may be connected to the base plate 103 by screws. The rack 1 is used to support and position the in-situ characterization module 2, the indexing module 3, and the complex load loading module 4.

[0061] like Figure 3 and Figure 4 As shown, the in-situ characterization module 2 may include a neutron scattering unit 201, an acoustic emission unit 1 202, an acoustic emission unit 203 and a digital image correlation unit 204. The in-situ characterization module 2 is used to realize multi-scale strain measurement, internal damage evolution process monitoring, damage pattern recognition and damage three-dimensional image reconstruction of the tested sample 5. Among them, the neutron scattering unit 201 and the digital image correlation unit 204 are respectively located at the rear and front of the tested sample 5, and the neutron beam penetrates the center of the gauge section of the tested sample 5 from the back to the front. The acoustic emission unit 1 202 and the acoustic emission unit 203 are located on the side of the tested sample 5, and the acoustic emission unit 1 202 and the acoustic emission unit 2 203 are arranged symmetrically up and down along the center of the gauge section of the tested sample 5. Through the setting of the complex load loading module 4 and the in-situ characterization module 2, the present invention provides a new technology and new method for the mechanical property test and analysis of materials under complex and harsh working conditions, which is helpful to promote the mechanical property test technology of fiber-reinforced composites from a single load to a complex load, and promote the transformation of the in-situ characterization technology of fiber-reinforced composite damage from a single mode to a combination of multiple technologies.

[0062] Further, the digital image correlation unit 204 is located above or below the center of the gauge length section of the tested sample 5 so as not to block the neutron beam and avoid affecting the neutron scattering unit 201. The digital image correlation unit 204 includes a bracket 20405, a laterally distributed micro-CCD camera 20401 and a standard CCD camera 20404, and a fill light located between or outside the micro-CCD camera 20401 and the standard CCD camera 20404, and the fill light includes a fill light 1 20402 and a fill light 2 20403 respectively corresponding to the micro-CCD camera 20401 and the standard CCD camera 20404. The bracket 20405 can be connected to the rigid frame 404 by screws, and the shooting angles of the micro-CCD camera 20401 and the standard CCD camera 20404 are oriented toward the center of the gauge length section of the tested sample 5, so as to monitor the center position of the gauge length of the tested sample 5. The microscopic CCD camera 20401 and the standard CCD camera 20404 are synchronously triggered and used in conjunction with an external trigger to transmit the collected image information to the image acquisition card, thereby realizing synchronous measurement of the macroscopic strain and microscopic strain of the test sample 5.

[0063] like Figures 1 to 13 As shown, the present invention also provides an in-situ characterization method using multiple technologies under complex loads, which can be applied to the in-situ characterization instrument using multiple technologies under complex loads as described above, including the following contents:

[0064] S1, clamping the test sample 5 at the moving end of the tension and compression unit 402;

[0065] S2, moving the moving end of the tension and compression unit 402 to apply a tensile / compressive force to the test sample 5 in the axial direction, and maintaining the tensile / compressive force constant after reaching a predetermined tensile / compressive force;

[0066] S3, moving the moving end of the bending unit 401 to drive one or both ends of the tested sample 5 to move toward one side of the bending pressure head 403, so that the tested sample 5 is bent and deformed at the position of the bending pressure head 403, and after reaching a predetermined bending force, the bending force is kept constant;

[0067] S4. Use the in-situ characterization module 2 to perform in-situ monitoring on the test sample 5.

[0068] Furthermore, the in-situ monitoring using the in-situ characterization module 2 in step S4 includes the following:

[0069] The neutron scattering unit 201 is used to monitor the damage information inside the test sample 5 and reconstruct a three-dimensional damage image; the acoustic emission unit (acoustic emission unit 1 202 and acoustic emission unit 2 203) is used to collect the acoustic emission signal of the damage of the test sample 5; the digital image correlation unit 204 is used to monitor the multi-scale strain information on the surface of the test sample 5;

[0070] Carry out multi-mode in-situ information fusion analysis of digital image correlation, acoustic emission and neutron scattering to reveal the multi-scale damage failure mechanism under complex loads.

[0071] According to the aforementioned multi-technique combined in-situ characterization instrument and method under complex loads, the present invention can achieve the following technical effects:

[0072] 1) Adopt modular unitized design ideas. The present invention may include a frame 1, an in-situ characterization module 2, a transposition module 3 and a complex load loading module 4. The in-situ characterization module 2 may include a neutron scattering unit 201, an acoustic emission unit 1 202, an acoustic emission unit 203 and a digital image correlation unit 204. The complex load loading module 4 includes a tension and compression unit 402 and a bending unit 401. Through high modularization, unitization and standardization, it is convenient for later maintenance.

[0073] 2) It can simulate the actual service conditions of materials. The present invention has a compact layout and diverse functions, and can realize the reconstruction of complex loads of tension-bending and compression-bending. Compared with the existing single-load mechanical testing instruments, it can effectively simulate the actual service conditions of fiber-reinforced composites, thereby providing innovative technical means for the precise testing of mechanical properties of fiber-reinforced composites under complex loads.

[0074] 3) Parallel in-situ monitoring can be achieved. The present invention aims at the problem that the existing in-situ characterization methods cannot simultaneously obtain information such as macro-fine-micro multi-scale crack initiation and damage evolution of fiber-reinforced composites, and it is difficult to fully reveal the multi-scale damage failure mechanism of fiber-reinforced composites. The innovative new in-situ characterization method based on digital image correlation, acoustic emission and neutron scattering is proposed. The combination of the above three in-situ characterization technologies can simultaneously carry out multi-scale deformation analysis, micro damage pattern recognition and three-dimensional damage image reconstruction. The three are mutually verified and functionally complementary, thereby truly realizing the multi-scale and multi-dimensional in-situ characterization of the entire process from deformation to fracture of fiber-reinforced composites, and solving the problem of "limited information" in the acquisition of damage and failure caused by a single in-situ characterization method. Due to the high penetration of neutrons, the new in-situ characterization method of multi-technique combination proposed by the present invention is applicable to materials with sizes ranging from microns to decimeters. Therefore, the method has wide applicability and is expected to serve the in-situ characterization of damage and failure mechanisms of structural materials in many key fields such as aerospace, nuclear industry, and national defense and military industry.

[0075] Referring to the above multi-technique combined in-situ characterization instrument and method under complex load, the present invention provides the following embodiments:

[0076] Combination Fig.12 and Fig.13 As shown in the figure, the in-situ characterization method using multiple techniques under complex loads includes the following steps:

[0077] Step 1: Prepare speckles. First, use sandpaper with increasing mesh size (400#, 800#, 1200#) to grind the center of the sample gauge section. Then, use spraying and jetting methods to prepare macroscopic and microscopic speckles, respectively. Consider factors such as spray paint material, film thickness, and speckle diameter to achieve high-quality composite speckle preparation.

[0078] Step 2: Clamp the test sample 5. Place the mounting surface of the test sample 5 on the clamp body 1 40212 and the clamp body 2 40211, rotate the limit screw 1 40204 and the limit screw 2 40207, and clamp the test sample 5 through the cover plate 1 40205 and the cover plate 2 40206.

[0079] Step 3: Loading tensile force. Start the tension and compression unit 402, and drive the clamp body 1 40212 and the clamp body 2 40211 to move through the symmetrically arranged longitudinal telescopic cylinder 1 40201 and the longitudinal telescopic cylinder 2 40210, thereby applying tensile / compressive force to the test sample 5. After reaching the predetermined tensile / compressive force, keep the tensile / compressive force constant.

[0080] Step 4: Loading bending force. After completing step 3, start the bending unit 401. The first moving frame 1 40103 and the first moving frame 2 40107 are driven to move by the centrally symmetrically arranged transverse telescopic cylinder 1 40101 and transverse telescopic cylinder 2 40110, and the load is transferred to the tension and compression unit 402 through the rotating shaft to apply bending force to the test sample 5.

[0081] Step 5: In-situ characterization using multiple technologies. This step is performed simultaneously with step 3 and step 4, that is, when the tension and compression unit 402 is started, the neutron scattering unit 201, the acoustic emission unit 1 202, the acoustic emission unit 203 and the digital image correlation unit 204 are started at the same time. The neutron scattering unit 201 is used to monitor the damage information inside the test sample 5 and reconstruct a three-dimensional damage image. The acoustic emission unit 1 202 and the acoustic emission unit 203 are used to collect the acoustic emission signals of the damage of the test sample 5. The digital image correlation unit 204 is used to monitor the multi-scale strain information on the surface of the test sample 5.

[0082] Step 6: Data post-processing. ① Drawing of bending force-deflection curve: The bending force is indirectly measured by the strain gauge 40305 on the bending pressure head 403, and the bending deflection is measured by the image method based on the digital image correlation unit 204. According to the measured bending force and bending deflection, the bending force-deflection curve is drawn by computer. ② In-situ characterization information processing: The three-dimensional damage reconstruction image of the test sample 5 is directly obtained based on the supporting software of the neutron scattering unit 201. Based on the three-dimensional damage reconstruction image, the initial damage position, damage mode, three-dimensional crack extension mode and extension path of the sample under different load modes are analyzed, and the crack density of the sample under the limit state is statistically analyzed. Based on the acoustic emission signal of the damaged test sample 5 collected by the acoustic emission unit 1 202 and the acoustic emission unit 2 203, the wavelet transform is used to carry out the time domain and frequency domain feature analysis of the acoustic emission signal, and the mapping relationship between the acoustic emission frequency domain signal waveform, frequency distribution and the damage mode of the fiber reinforced composite is established. In addition, an automatic recognition model for the damage mode of fiber reinforced composites is established based on the deep learning algorithm of the convolutional neural network. Based on the established automatic damage identification model, the number and proportion of matrix fracture, fiber fracture and interface separation under different load modes are counted to reveal the quantitative influence of complex load modes on damage types. Based on the supporting analysis software of the digital image correlation unit 204, the macroscopic and microscopic strain distribution information of the tested sample 5 is obtained, and the correlation between the load mode (tensile-bending composite, compression-bending composite) and the macroscopic strain distribution is established to explore the microscopic strain transfer mode and macroscopic strain evolution process of the sample under different load modes. Finally, the multi-mode in-situ information fusion analysis of digital image correlation, acoustic emission and neutron scattering is further carried out to reveal the multi-scale damage failure mechanism of fiber-reinforced composites under complex loads, thereby providing an important basis for the improvement of the preparation process of fiber-reinforced composites.

[0083] In one embodiment, the multi-technique combined in-situ characterization instrument under complex loads includes an in-situ characterization module 2, a complex load loading module 4, a transposition module 3 and a frame 1. The frame 1 is a double-column 102 structure, which is used to support and position the in-situ characterization module 2, the transposition module 3 and the complex load loading module 4. The in-situ characterization module 2 includes a neutron scattering unit 201, an acoustic emission unit (acoustic emission unit 1 202 and acoustic emission unit 2 203) and a digital image correlation unit 204, which are used to achieve multi-scale strain measurement, internal damage evolution process monitoring, damage pattern recognition and damage three-dimensional image reconstruction of the test sample 5. The transposition module 3 is used to achieve precise rotation and positioning of the complex load loading module 4. The complex load loading module 4 mainly includes a bending unit 401 and a tension and compression unit 402, which are used to apply single loads such as tension, compression, bending, etc. to the test sample 5, as well as complex loads such as tension-bending compound and compression-bending compound. The present invention is aimed at major national needs and provides a new technology and method for testing and analyzing the mechanical properties of materials under complex and harsh working conditions. It helps to promote the transition of fiber-reinforced composite mechanical properties testing technology from single load to complex load, and promotes the transformation of fiber-reinforced composite damage in-situ characterization technology from a single mode to the combination of multiple technologies.

[0084] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. An in-situ characterization instrument for multiple technologies under complex loads, characterized by: It includes a complex load loading module and an in-situ characterization module. The complex load loading module includes a rigid frame, a longitudinally loaded tension and compression unit, and a transversely loaded bending unit. The movable end of the tension and compression unit is used to connect the end of the test sample, the fixed end of the tension and compression unit is connected to the movable end of the bending unit, and the fixed end of the bending unit is installed on the rigid frame. It also includes a bending pressure head installed on the rigid frame, and the bending pressure head corresponds to the middle part of the test sample. The in-situ characterization module is used to perform in-situ monitoring of the test sample.

2. The multi-technique combined in-situ characterization instrument under complex loads according to claim 1, characterized in that: The bending unit includes a transverse telescopic cylinder and a moving frame. The cylinder body of the transverse telescopic cylinder is fixed to the rigid frame. The piston rod of the transverse telescopic cylinder is connected to the moving frame. The moving frame is rotatably connected to the fixed end of the tension and compression unit.

3. The multi-technique combined in-situ characterization instrument under complex loads according to claim 2, characterized in that: The movable frame includes a first movable frame and a second movable frame distributed on both sides of the fixed end of the tension and compression unit, the first movable frame and the second movable frame are both slidably connected to the rigid frame, the piston rod of the transverse telescopic cylinder is connected to the first movable frame or the second movable frame, and the transverse telescopic cylinder is arranged at both ends of the test sample in a centrally symmetrical manner with the test sample.

4. The multi-technique combined in-situ characterization instrument under complex loads according to claim 2, characterized in that: The tension and compression unit includes a longitudinal telescopic cylinder, a force sensor and a clamp body. The cylinder body of the longitudinal telescopic cylinder is rotatably connected to the moving frame. The force sensor is connected between the piston rod of the longitudinal telescopic cylinder and the clamp body. The clamp body is used to clamp the test sample.

5. The multi-technique combined in-situ characterization instrument under complex loads according to claim 1, characterized in that: The bending pressure head includes a base and a pressure head end, the base includes legs and an elastic beam connected to the legs, the pressure head end is connected to the middle of the elastic beam, and both sides of the elastic beam are used to install strain gauges.

6. The multi-technique combined in-situ characterization instrument under complex loads according to claim 1, characterized in that: It also includes a frame and a transfer module, wherein the fixed end of the transfer module is connected to the frame, the rotating end of the transfer module is connected to the rigid frame, and the rotation center of the transfer module coincides with the axis of the tested sample.

7. The multi-technique combined in-situ characterization instrument under complex loads according to any one of claims 1 to 6, characterized in that: The in-situ characterization module includes a neutron scattering unit, an acoustic emission unit and a digital image correlation unit, wherein the neutron scattering unit and the digital image correlation unit are respectively located at the rear and the front of the tested sample, the acoustic emission unit is located at the side of the tested sample, and the acoustic emission units are symmetrically arranged up and down along the center of the gauge section of the tested sample.

8. The multi-technique combined in-situ characterization instrument under complex loads according to claim 7, characterized in that: The digital image correlation unit is located above or below the center of the gauge section of the tested sample. The digital image correlation unit includes a laterally distributed microscope CCD camera and a standard CCD camera and a fill light located between or outside the microscope CCD camera and the standard CCD camera. The shooting angles of the microscope CCD camera and the standard CCD camera are toward the center of the gauge section of the tested sample.

9. A multi-technique combined in-situ characterization method under complex loads, characterized by: The multi-technique combined in-situ characterization instrument under complex loads as described in any one of claims 1 to 8 is used, comprising the following contents: S1. Clamp the test sample on the moving end of the tension and compression unit; S2, moving the moving end of the tension and compression unit to apply a tensile / compressive force to the test sample in the axial direction, and maintaining the tensile / compressive force constant after reaching a predetermined tensile / compressive force; S3, moving the moving end of the bending unit to drive the end of the tested sample to move toward one side of the bending pressure head, so that the tested sample is bent and deformed at the position of the bending pressure head, and after reaching a predetermined bending force, the bending force is kept constant; S4. Using an in-situ characterization module to perform in-situ monitoring on the tested sample.

10. The multi-technique combined in-situ characterization method under complex loads according to claim 9, characterized in that: In step S4, the in-situ monitoring using the in-situ characterization module includes the following: A neutron scattering unit is used to monitor the damage information inside the tested sample and to reconstruct a three-dimensional damage image; an acoustic emission unit is used to collect the acoustic emission signal of the damage of the tested sample; and a digital image correlation unit is used to monitor the multi-scale strain information on the surface of the tested sample; Carry out multi-mode in-situ information fusion analysis of digital image correlation, acoustic emission and neutron scattering to reveal the multi-scale damage failure mechanism under complex loads.

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