An electrically assisted tension-compression cyclic loading device and test method for ultra-thin titanium plates

Abstract

The present invention discloses an electric-assisted tensile-compression cyclic loading device and a testing method for an ultra-thin titanium plate. The device comprises: two outer specimens used in conjunction with an ultra-thin titanium plate specimen, the two outer specimens are fixed on both sides of the ultra-thin titanium plate specimen, and the three form a composite tensile-compression specimen, the ends of the ultra-thin titanium plate specimen both extend out of the ends of the outer specimens, and the two sides of the composite tensile-compression specimen are fixed by a clamping assembly to apply lateral force thereto; two pairs of electric-assisted clamps, which are respectively clamped at both ends of the composite tensile-compression specimen, and each pair of electric-assisted clamps comprises two oppositely arranged chucks, the clamping surfaces of the chucks having a conductive structure, the conductive structure being connected to an external power supply, and when the composite tensile-compression specimen is clamped on the chucks, the conductive structure contacts the composite tensile-compression specimen to transfer current to the composite tensile-compression specimen through the conductive structure to heat it, and the chucks are connected to the loading end of a universal testing machine. The present invention can prevent the ultra-thin titanium plate specimen from twisting and deforming during the test.

Description

Technical Field

[0001] The present invention relates to the technical field of electrically assisted tension-compression testing, and in particular to an electrically assisted tension-compression cycle loading device and a testing method for an ultra-thin titanium plate. Background Art

[0002] With the demand for lightweight and high performance in industries such as aerospace, transportation, and automotive manufacturing, titanium and titanium alloys with high specific strength are widely used. However, titanium has poor plasticity at room temperature, with high deformation resistance and yield-to-elasticity ratio, which seriously limits the application of ultra-thin titanium plates.

[0003] To address the poor formability of titanium at room temperature, electro-assisted forming (E-AF) has emerged. However, the deformation behavior of ultra-thin titanium sheets during E-AF is complex. During stamping, fillets undergo complex deformation paths, including loading and unloading, reverse loading, and cyclic loading. This makes E-assisted uniaxial tensile testing difficult to characterize. Therefore, E-assisted tension-compression cyclic loading testing is typically used to characterize the mechanical behavior of ultra-thin titanium sheets under these complex loading paths. Currently, thin-plate tension and compression testing devices primarily apply lateral forces to the left and right clamps to prevent the ultra-thin titanium specimen, located between the two clamps, from buckling during compression. Tensile and compressive loads are then applied to the upper and lower ends of the ultra-thin titanium sheet using the clamps of a universal testing machine. However, the smooth progress of the test is often hampered by wrinkling and deformation of the specimen. For example, due to the thinness of the ultra-thin titanium sheet, it is difficult to prevent the sheet from twisting using only the clamps and specimen fixtures. Furthermore, existing E-assisted tension and compression tests rely on specialized specimens with wire interfaces to apply the electric field, which can easily cause kinking at the connection between the wires and the ultra-thin specimen. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides an ultra-thin titanium plate electrically assisted tension-compression cyclic loading device and a testing method, which can prevent the ultra-thin titanium plate specimen from twisting and deforming during the test.

[0005] The first aspect of the present invention provides an electric-assisted tensile and compressive cyclic loading device for ultra-thin titanium plates, comprising: two outer samples used in conjunction with ultra-thin titanium plate specimens, the two outer samples are fixed on both sides of the ultra-thin titanium plate specimens, and the three form a composite tensile and compressive specimen. The ends of the ultra-thin titanium plate specimens extend out of the ends of the outer samples. The two sides of the composite tensile and compressive specimens are fixed by clamping assemblies to apply lateral force thereto. Two pairs of electric-assisted clamps are respectively clamped at the two ends of the composite tensile and compressive specimens. Each pair of electric-assisted clamps includes two oppositely arranged clamps, and the clamping surfaces of the clamps have a conductive structure. The conductive structure is connected to an external power supply. When the composite tensile and compressive specimen is clamped on the clamps, the conductive structure contacts the composite tensile and compressive specimen to transfer current to the composite tensile and compressive specimen through the conductive structure to heat it. The clamps are connected to the loading end of a universal testing machine. The composite tensile and compressive specimen should have a moderate thickness. If it is too thin, it is still easy to twist during compression. If it is too thick, the specimen is difficult to clamp. At the same time, the two outer samples are fixed on both sides of the ultra-thin titanium plate specimen to form a composite tensile and compressive specimen structure, which can also ensure uniform force transmission.

[0006] Optionally, the outer specimen has a resistivity of 10 12 Ω·m-10 17 Ω·m, resistivity is 10 12 Ω·m-10 17 Insulation can be considered within the Ω·m range, and the current has little effect on the outer specimen.

[0007] Optionally, the conductive structure includes a conductive sheet and a connecting sheet connected together, both of which are made of conductive materials. The conductive sheet is located on the clamping surface of the chuck, and has serrations on the side that contacts the composite tensile and compressive specimen. A through groove is also provided on the conductive sheet, and the outer end of the specimen is placed in the through groove. The ultra-thin titanium plate specimen contacts the conductive sheet, and the connecting sheet is connected to an external power supply. The conductive sheet is responsible for transmitting current and heating the ultra-thin titanium plate specimen, and the connecting sheet is connected to an external power supply and is responsible for transmitting the current of the external power supply to the conductive sheet.

[0008] Optionally, the upper and lower clamps of the universal testing machine correspondingly clamp two pairs of electric-assisted clamps. The clamps are also provided with positioning columns and fixing slots. The positioning columns cooperate with the positioning slots of the universal testing machine, and the loading head of the universal testing machine is clamped into the fixing slots, thereby achieving the purpose of quickly completing the connection and alignment with the universal testing machine, accurately positioning the relative position of the electric-assisted clamp and the universal testing machine clamp, and ensuring the centering and stability during the loading process.

[0009] Optionally, the thickness of the outer sample is 0.5 mm to 0.7 mm, and the material is one of glass fiber composite material, polyetheretherketone, carbon fiber-glass fiber composite material, or other composite materials with good insulation, high temperature resistance and elongation.

[0010] Optionally, the outer sample and the ultra-thin titanium plate sample are bonded and fixed by epoxy resin, and the layer thickness of the epoxy resin is 0.02 mm-0.05 mm. The layer thickness is selected to be 0.02 mm-0.05 mm. In this range, the tensile pressure on the resin layer can be ignored, which is convenient for subsequent calculations.

[0011] Optionally, the clamping assembly includes: two insulating gaskets symmetrically arranged on both sides of the composite tensile and compressive specimen, each insulating gasket includes a first insulating sheet and a second insulating sheet stacked along the extension direction of the ultra-thin titanium plate specimen, and two splints symmetrically arranged on the outside of the two insulating gaskets, the outside of the splints is connected to a lateral force adjustment assembly, each splint includes a first splint and a second splint stacked, the first splint is fixedly connected to the corresponding first insulating sheet, and the second splint is fixedly connected to the corresponding second insulating sheet, the first insulating sheet and the second insulating sheet, as well as the first splint and the second splint are each slidably connected by a plurality of straight rods, so that the first insulating sheet and the second insulating sheet, as well as the first splint and the second splint move synchronously along the extension direction of the ultra-thin titanium plate specimen, the insulating gasket is used to isolate current, and the splint is used to transmit lateral force.

[0012] Optionally, the first insulating sheet and the second insulating sheet, as well as the first splint and the second splint are each connected by a comb-like structure, which ensures that all sections can be constrained by lateral force when the composite tensile-compression specimen is stretched and then compressed.

[0013] Optionally, the lateral force adjustment component includes: two inner plates, two outer plates and a spring, the two inner plates are respectively placed on the outside of the corresponding splints, and the two outer plates are respectively placed on the outside of the corresponding inner plates, and the inner plates and the outer plates are provided with sliding holes along the extension direction of the ultra-thin titanium plate specimens, and the screws pass through the sliding holes in turn and are fixed to the splints and insulating gaskets. A spring adjustment block is rotatably connected to one of the outer plates, one end of the spring is fixed to the spring adjustment block, and the other end is fixed to the corresponding inner plate. The compression force of the spring is adjusted by rotating the spring adjustment block, thereby adjusting the lateral force applied to one side of the inner plate. In this way, only the spring adjustment block and the spring are set on one side for convenient adjustment, and the lateral force on the other side can be collected by a force sensor.

[0014] A second aspect of the present invention provides a test method based on the above-mentioned ultra-thin titanium plate electrically assisted tension-compression cyclic loading device, comprising the following steps:

[0015] Step 1: Prepare a composite tension-compression specimen by fixing outer specimens on both sides of the ultra-thin titanium plate specimen to form a composite tension-compression specimen;

[0016] Step 2: Clamp the prepared composite tensile and compressive specimen onto the universal testing machine using an electric-assisted clamp. Apply lateral force to the composite tensile and compressive specimen on both sides through clamping components to secure it.

[0017] Step 3: Set the required parameters for the tension and compression tests and conduct the tension and compression tests;

[0018] Step 4: Observe whether the ultra-thin titanium plate specimen buckles. If buckling occurs, adjust the lateral force. Repeat steps 1 to 4 until the ultra-thin titanium plate specimen does not buckle. Obtain the corresponding lateral force when no buckling occurs.

[0019] Step 5: Use the lateral force corresponding to the non-buckling state to fix the remaining composite tension and compression specimens, and conduct tension and compression tests to obtain experimental data, and use the experimental data to obtain stress-strain curves.

[0020] The technical solution provided by the embodiment of the present invention has the following advantages compared with the existing technology:

[0021] An embodiment of the present invention provides an electric-assisted tensile-compression cyclic loading device and a test method for ultra-thin titanium plates, which are used for compression tests of thin plates with a thickness of less than 1 mm. By fixing two outer samples on both sides of the original ultra-thin titanium plate sample to form a composite tensile-compression sample as a whole, the sample thickness is increased, which can avoid unstable buckling during the compression process. At the same time, two pairs of electric-assisted clamps clamp the composite tensile-compression sample, and the conductive structure on each clamp of the electric-assisted clamp is directly connected to the composite tensile-compression sample to heat it. By connecting the composite tensile-compression sample and the electric-assisted clamp to form a whole, the original ultra-thin titanium plate sample is replaced, and the setting of a wire interface on the sample is avoided, thereby further avoiding the twisting and deformation of the sample, solving the problem of wrinkling of the ultra-thin plate under compression load, and ensuring the smooth progress of the test. The clamp is then connected to the loading end of the universal testing machine, which can be used to characterize the mechanical behavior of the ultra-thin titanium plate under complex loading paths under current conditions, providing theoretical support for the electric-assisted forming process. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A schematic structural diagram of an electrically assisted tension-compression cyclic loading device for an ultra-thin titanium plate provided in an embodiment of the present invention;

[0023] Figure 2 A schematic diagram of the explosion structure of an electrically assisted tension-compression cyclic loading device for ultra-thin titanium plates provided in an embodiment of the present invention;

[0024] Figure 3 A schematic structural diagram of the first orientation of a composite tension-compression specimen provided by an embodiment of the present invention;

[0025] Figure 4 A schematic structural diagram of a chuck provided in an embodiment of the present invention;

[0026] Figure 5 A schematic structural diagram of a first insulating sheet and a second insulating sheet provided in an embodiment of the present invention;

[0027] Figure 6A schematic structural diagram of a first clamping plate and a second clamping plate provided in an embodiment of the present invention;

[0028] Figure 7 A schematic structural diagram of the second orientation of the composite tension-compression specimen provided by an embodiment of the present invention;

[0029] Figure 8 for Figure 7 Enlarged schematic diagram of the local structure at G in the middle.

[0030] Description of reference numerals:

[0031] 1. Outer specimen; 2. Ultra-thin titanium plate specimen; 3. First insulating sheet; 4. Second insulating sheet; 5. Spring; 6. Spring adjustment block; 7. Force sensor; 8. Outer plate; 9. Inner plate; 10. Straight rod; 11. Chuck; 12. First clamping plate; 13. Second clamping plate; 14. Thermocouple; 15. Conductive structure; 150. Conductive sheet; 151. Connecting sheet; 152. Through slot; 16. Positioning column; 17. Fixing slot; 18. Insulation layer. DETAILED DESCRIPTION

[0032] A specific embodiment of the present invention is described in detail below with reference to the accompanying drawings, but it should be understood that the protection scope of the present invention is not limited by the specific embodiment.

[0033] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the technical solutions of the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0034] Existing electrically assisted tension-compression cyclic loading test equipment will cause the ultra-thin titanium plate to buckle and deform when testing it. For example, because the ultra-thin titanium plate is too thin, the pressure is difficult to be transmitted to the gauge section through both ends of the specimen during compression, and the transition area between the clamping section and the gauge section is prone to distortion. It is difficult to ensure that the ultra-thin titanium plate does not twist and deform only by using the clamp and the specimen fixture. For example, the existing electrically assisted tension-compression test mainly applies the electric field by designing a special specimen with a wire interface. The connection between the wire and the ultra-thin specimen is prone to kinking, which affects the test.

[0035] To this end, an embodiment of the present invention provides an ultra-thin titanium plate electrically assisted tension-compression cyclic loading device and a testing method, which can prevent the ultra-thin titanium plate specimen from twisting and deforming during the test.

[0036] The present invention is described below by means of several specific embodiments. To keep the following description of the embodiments of the present invention clear and concise, detailed descriptions of known functions and components may be omitted. When any component of an embodiment of the present invention appears in more than one drawing, the component may be represented by the same reference numeral in each drawing.

[0037] refer to Figure 1 、 Figure 2 and Figure 3 , Figure 1 This is a schematic diagram of the structure of an electric-assisted tension-compression cyclic loading device for an ultra-thin titanium plate provided by an embodiment of the present invention. Figure 2 A schematic diagram of the packaging structure of an ultra-thin titanium plate electrically assisted tension-compression cyclic loading device provided by an embodiment of the present invention. Figure 3 A schematic structural diagram of the first orientation of the composite tension-compression specimen provided by an embodiment of the present invention is shown in FIG. Figure 1 、 Figure 2 and Figure 3As shown, an embodiment of the present invention provides an ultra-thin titanium plate electrically assisted tension and compression cyclic loading device, comprising: two outer samples 1 used in conjunction with the ultra-thin titanium plate sample 2 and two pairs of electrically assisted clamps. The two outer samples 1 are fixed on both sides of the ultra-thin titanium plate sample 2, and the three form a composite tension and compression sample. It should be understood that the composite tension and compression sample should ensure a moderate thickness. If it is too thin, it is still easy to twist during compression. If it is too thick, the sample is not easy to be clamped. At the same time, the two outer samples 1 are fixed on both sides of the ultra-thin titanium plate sample 2 to form a composite tension and compression sample structure, which can also ensure uniform force transmission. The ends of the ultra-thin titanium plate sample 2 extend out of the ends of the outer sample 1 to ensure that the ultra-thin titanium plate sample 2 is in contact with the conductive structure 15, and to ensure that the current is accurately passed into the ultra-thin titanium plate sample 2. The two sides of the composite tension and compression sample are fixed by a clamping assembly to apply lateral force to it. The clamping assembly fixes the composite tension and compression sample to ensure that it does not torsion and buckling during loading. Mechanical clamping, hydraulic clamping or pneumatic clamping can be used. The specific selection depends on the test requirements. Two pairs of electrically assisted The clamps are respectively clamped at both ends of the composite tensile and compressive specimens. Each pair of electrically assisted clamps includes two oppositely arranged clamps 11. The clamping surface of the clamp 11 has a conductive structure 15. The conductive structure 15 usually uses highly conductive materials such as copper or silver to ensure efficient current transmission and reduce energy loss. The conductive structure can be designed as multi-point contact or surface contact to optimize current distribution and heating uniformity. The conductive structure 15 is connected to an external power supply. When the composite tensile and compressive specimen is clamped on the clamp 11, the conductive structure 15 contacts the composite tensile and compressive specimen to transfer current to the composite tensile and compressive specimen through the conductive structure 15 to heat it. The external power supply provides the required current, and the current size is adjustable to adapt to different heating requirements. The current size and heating time are adjusted by the control system to ensure that the composite tensile and compressive specimen is tested at the set temperature. The clamp 11 is connected to the loading end of the universal testing machine, and the tensile pressure is applied by the universal testing machine. The universal testing machine can accurately control the loading speed and number of cycles, and the current size is controlled by an external power supply to meet different test conditions and realize electrothermal coupling loading.

[0038] An embodiment of the present invention provides an electric-assisted tension-compression cyclic loading device for ultra-thin titanium plates, which is used for compression tests of thin plates with a thickness of less than 1 mm. By fixing two outer samples on both sides of the original ultra-thin titanium plate sample to form a composite tension-compression sample as a whole, the sample thickness is increased, which can avoid unstable buckling during the compression process. At the same time, two pairs of electric-assisted clamps clamp the composite tension-compression sample, and the conductive structure on each clamp of the electric-assisted clamp is directly connected to the composite tension-compression sample to heat it. By connecting the composite tension-compression sample and the electric-assisted clamp to form a whole, the original ultra-thin titanium plate sample is replaced, and the setting of a wire interface on the sample is avoided, thereby further avoiding the distortion of the sample, solving the problem of wrinkling of the ultra-thin plate under compression load, and ensuring the smooth progress of the test. The clamp is then connected to the loading end of the universal testing machine, which can be used to characterize the mechanical behavior of the ultra-thin titanium plate under complex loading paths under current conditions, providing theoretical support for the electric-assisted forming process.

[0039] Specifically, in the embodiment of the present invention, the resistivity of the outer sample 1 is 10 12 Ω·m-10 17 Ω·m, when the resistivity of the outer sample 1 is 10 12 Ω·m-10 17 When the resistance is greater than Ω·m, it can be considered as insulating, and the current has basically no effect on the outer sample 1. In this way, when the chuck 11 clamps the composite tensile and compressive sample, there is no need to repeatedly adjust the position of the composite tensile and compressive sample. It is sufficient to ensure that the ultra-thin titanium plate sample 2 contacts the conductive structure 15, and the outer sample 1 can contact or not contact the conductive structure 15. In this way, there is no need to separately measure the mechanical properties of the outer sample 1 and the stress conditions during the tensile and compressive processes when current exists.

[0040] refer to Figure 4 , Figure 4 A schematic diagram of the structure of the chuck provided in an embodiment of the present invention is shown in FIG. Figure 4 As shown, the conductive structure 15 includes a conductive sheet 150 and a connecting sheet 151 that are connected together. The conductive sheet 150 and the connecting sheet 151 are both made of conductive materials, such as copper. The conductive sheet 150 is located on the clamping surface of the chuck 11, and has serrations on the side that contacts the composite tensile and compressive specimen. A through groove 152 is also provided on the conductive sheet 150, and the end of the outer specimen 1 is placed in the through groove 152. The ultra-thin titanium plate specimen 2 contacts the conductive sheet 150. The conductive sheet 150 is responsible for transmitting current and heating the ultra-thin titanium plate specimen 2. The connecting sheet 151 is connected to an external power supply and is responsible for transmitting the current of the external power supply to the conductive sheet 150.

[0041] A through groove 152 is also provided on the conductive sheet 150, and the end of the outer sample 1 is placed in the through groove 152, thereby increasing the clamping thickness of the chuck 11 and increasing the clamping force of the chuck 11 on the composite tensile and compressive sample, preventing the composite tensile and compressive sample from sliding, while also ensuring that the current is directly transmitted to the ultra-thin titanium plate sample 2. The conductive sheet 150 is located on the clamping surface of the chuck 11, and the side in contact with the composite tensile and compressive sample has serrations, which can increase the contact area and friction, prevent the composite tensile and compressive sample from sliding, and optimize the current distribution. When the chuck 11 clamps the composite tensile and compressive sample, the serration structure of the conductive sheet 150 is in close contact with the composite tensile and compressive sample, ensuring that the current is evenly transmitted and heating the ultra-thin titanium plate sample 2.

[0042] Reference again Figure 4 The upper and lower clamps of the universal testing machine correspond to clamping two pairs of electric-assisted clamps. The clamp 11 also has a positioning column 16 and a fixing groove 17. The positioning column 16 cooperates with the positioning groove of the universal testing machine to achieve the purpose of quickly completing the connection and alignment with the universal testing machine, accurately positioning the relative position of the electric-assisted clamp and the universal testing machine clamp, ensuring the centering and stability during the loading process. The loading head of the universal testing machine is clamped in the fixing groove 17, and the loading head can accurately transmit the force to the composite tensile and compressive specimen. It should be noted that the clamp 11 also has an insulating layer 18, which is located under the conductive sheet 150. Peek polyetheretherketone insulating material is selected. The main part of the clamp 11 is iron, which has high strength to ensure that the electric-assisted clamp will not be damaged under repeated use.

[0043] In this embodiment, the thickness of the outer sample 1 is 0.5mm-0.7mm, and the material is one of glass fiber composite material, polyetheretherketone, carbon fiber-glass fiber composite material, or other composite materials with good insulation, high temperature resistance and elongation. After the outer sample 1 is clamped on both sides of the ultra-thin titanium plate sample 2, the thickness should be ensured to be moderate. Too thin samples are prone to distortion during compression, and too thick samples are difficult to clamp. Glass fiber is chosen because it has high resistivity and a large elastic limit. In tension and compression tests, it generally deforms elastically, which facilitates the calculation of the stress conditions during tension and compression. However, its elongation at break is small, and it can be used for tension and compression cyclic loading tests with smaller strains. Polyetheretherketone has good elongation and can be used for tension and compression cyclic loading under high strain. It also has good strength and hardness, ensuring the smooth progress of the test.

[0044] In this embodiment, the outer sample 1 and the ultra-thin titanium plate sample 2 are bonded and fixed by epoxy resin, and the layer thickness of the epoxy resin is 0.02mm-0.05mm. If the layer thickness of the epoxy resin is too thick, it will affect the stress calculation of the ultra-thin titanium plate sample 2 during tension and compression. The layer thickness is selected to be 0.02mm-0.05mm. In this range, the tensile pressure on the resin layer can be ignored, which is convenient for subsequent calculations.

[0045] refer to Figure 5 and Figure 6 , Figure 5 A schematic structural diagram of a first insulating sheet and a second insulating sheet provided in an embodiment of the present invention, Figure 6 A schematic structural diagram of the first and second splints provided in an embodiment of the present invention is shown in FIG. Figure 5 and Figure 6 As shown, in an embodiment of the present invention, the clamping assembly includes: two insulating gaskets symmetrically arranged on both sides of the composite tensile and compressive specimen, each insulating gasket includes a first insulating sheet 3 and a second insulating sheet 4 stacked along the extension direction of the ultra-thin titanium plate specimen 2, two clamps symmetrically arranged on the outside of the two insulating gaskets, and the outside of the clamps is connected to a lateral force adjustment assembly to adjust the clamping force of the clamps and the insulating gaskets on the composite tensile and compressive specimen, each clamp includes a first clamp 12 and a second clamp 13 stacked, the first clamp 12 is fixedly connected to the corresponding first insulating sheet 3, and the second clamp 13 is fixedly connected to the corresponding second insulating sheet 4, and the first insulating sheet 3 and the second insulating sheet 4, as well as the first clamp 12 and the second clamp 13, are each slidably connected by a plurality of straight rods 10, so that the first insulating sheet 3 and the second insulating sheet 4, as well as the first clamp 12 and the second clamp 13 move synchronously along the extension direction of the ultra-thin titanium plate specimen 2. In this embodiment, the insulating gasket is used to isolate the current. Since the melting point of the insulating material is generally low, between 200℃ and 300℃, the increase in sample temperature during the electrical assist process will cause the insulating gasket to soften and fail to transmit lateral force well. Therefore, a splint is provided on the outer layer of the insulating gasket to transmit lateral force. The through grooves opened at the same position of the insulating gasket and the splint can facilitate DIC strain measurement.

[0046] The first and second insulating sheets 3 and 4 are connected to the first and second clamping plates 12 and 13 via bolts. These plates allow for free movement perpendicular to the clamping plates, enabling cyclic loading during tension and compression. To prevent vertical misalignment of the clamping plates and insulating gaskets, straight rods 10 are positioned between the first and second insulating sheets 3 and 4, and between the first and second clamping plates 12 and 13, acting as centering guides. The clamping plates and insulating gaskets on the left and right sides of the specimen are symmetrically arranged to prevent distortion of the specimen in the comb-shaped regions of the insulating gaskets and clamping plates.

[0047] Specifically, the first insulating sheet 3 and the second insulating sheet 4, as well as the first splint 12 and the second splint 13 are each connected by a comb-like structure. The comb-like structure ensures that all sections can be constrained by lateral forces when the composite tensile and compressive specimen is stretched and then compressed. The comb-like structure in the non-gauge section is used to achieve movement without reducing the anti-buckling ability of the device, further avoiding buckling deformation, and realizing tensile and compressive cyclic loading of the ultra-thin titanium plate specimen 2.

[0048] Reference again Figure 2In this embodiment, the lateral force adjustment component includes: two inner plates 9, two outer plates 8 and a spring 5. The two inner plates 9 are respectively placed on the outer sides of the corresponding splints, and the two outer plates 8 are respectively placed on the outer sides of the corresponding inner plates 9. Slide holes are opened on the inner plates 9 and the outer plates 8 along the extension direction of the ultra-thin titanium plate specimen 2. The screws pass through the slide holes in turn and are fixed to the splints and insulating gaskets. A spring adjustment block 6 is rotatably connected to one of the outer plates 8. One end of the spring 5 is fixedly connected to the spring adjustment block 6, and the other end is fixedly connected to the corresponding inner plate 9. The compression amount of the spring 5 is adjusted by rotating the spring adjustment block 6, thereby adjusting the lateral force applied to one side of the inner plate 9.

[0049] The spring adjusting block 6 can freely rotate the spring 5 at the outer plate 8. The spring adjusting block 6 rotates the spring 5 downward to compress it. At the same time, the bolts at the outer plate 8 are adjusted to make the outer plate 8 close to the spring adjusting block 6, so that the lateral force is transmitted from the inner plate 9 to both sides of the composite tension and compression specimen through the spring 5. In this way, it is convenient to adjust by setting the spring adjusting block 6 and the spring 5 on only one side, and the lateral force can be collected by the force sensor 7 on the other side.

[0050] A second aspect of the present invention provides a test method based on the above-mentioned ultra-thin titanium plate electrically assisted tension-compression cyclic loading device, comprising the following steps:

[0051] Step 1: Prepare a composite tensile-compression specimen by fixing the outer specimens 1 on both sides of the ultra-thin titanium plate specimen 2 to form a composite tensile-compression specimen;

[0052] Step 2: Clamp the prepared composite tensile and compressive specimen onto the universal testing machine using an electric-assisted clamp. Apply lateral force to the composite tensile and compressive specimen on both sides through clamping components to secure it.

[0053] Step 3: Set the required parameters for the tension and compression tests and conduct the tension and compression tests;

[0054] Step 4: Observe whether the ultra-thin titanium plate specimen 2 buckles. If buckling occurs, adjust the lateral force. Repeat steps 1 to 4 until the ultra-thin titanium plate specimen 2 does not buckle. Obtain the lateral force corresponding to the condition where no buckling occurs.

[0055] Step 5: Use the lateral force corresponding to the non-buckling state to fix the remaining composite tension and compression specimens, and conduct tension and compression tests to obtain experimental data, and use the experimental data to obtain stress-strain curves.

[0056] The specific implementation is as follows:

[0057] 1) Prepare composite tensile and compressive specimens by bonding outer specimens (1) with a thickness of 0.5 mm to 0.7 mm on both sides of an ultra-thin titanium plate specimen (2) using epoxy resin. The epoxy resin layer is approximately 0.05 mm thick. After bonding, the specimens are cured to ensure that the outer specimens (1) and the ultra-thin titanium plate specimen (2) are tightly bonded to form composite tensile and compressive specimens.

[0058] 2) Spraying speckles in the thickness direction of the prepared composite tensile and compressive specimens for DIC strain measurement;

[0059] 3) Clamp the prepared composite tensile and compressive specimen onto the universal testing machine using an electric-assisted fixture. Apply a lubricant with a thickness of approximately 0.1 mm to the gauge section and surrounding areas on both sides of the composite tensile and compressive specimen to ensure sufficient lubrication to reduce friction between the composite tensile and compressive specimen and the insulating pad. Then, install the first clamping plate 12, the second clamping plate 13, the straight rod 10, the spring 5, the spring adjustment block 6, the outer plate 8, the inner plate 9, and the force sensor 7 in sequence. Separate the first clamping plate 12 and the second clamping plate 13 by a distance to facilitate compression. After installation, connect the force sensor 7 in the device to the computer to obtain the lateral force F applied to the composite tensile and compressive specimen. c ;

[0060] 4) Adjust the spring adjustment block 6 to clamp the composite tension and compression specimen and record the screw-in amount x;

[0061] 5) Set the required parameters for the tension and compression tests and conduct the tension and compression tests;

[0062] 6) Observe whether the ultra-thin titanium plate specimen 2 buckles. If buckling occurs, remove the buckled composite tension-compression specimen and adjust the screw-in amount x in step 4 to 1.5 times the previous amount. Repeat steps 1 to 6 until the ultra-thin titanium plate specimen 2 does not buckle, then continue with the following steps.

[0063] 7) If no buckling occurs, record the current screw-in amount x, take a new composite tension-compression specimen, re-clamp it, adjust the screw-in amount to x, and start the following steps;

[0064] 8) Set the current parameters and test conditions, start the power supply, and transmit the current to the composite tension and compression specimen through the electric auxiliary fixture. Heat the ultra-thin titanium plate specimen 2 to the predetermined temperature and monitor the temperature through the thermocouple 14. Figure 7 and Figure 8 ;

[0065] 9) Start the universal testing machine to conduct tension and compression cycle loading test;

[0066] 10) After the test is completed, adjust the spring adjustment block 6 to loosen the splint and remove the composite tension and compression specimen;

[0067] 11) Calculate the force F exerted on the ultra-thin titanium plate specimen 2 during tension and compression using the data measured by the universal testing machine and force sensor 7. Ti =F A -F f -F gf , where F A is the force on the composite tension and compression specimen, F f is the friction force, F gfis the force applied to the outer specimen 1 during tension and compression;

[0068] 12) Friction is equal to the lateral force multiplied by the coefficient of friction, F f =2F c *μ, where μ can be measured by an electrically assisted friction coefficient test;

[0069] 13) If the outer specimen 1 is always in elastic state during deformation, F gf The elastic modulus E gf And strain calculation, if the outer sample 1 enters the plastic stage during the deformation process, since the outer sample 1 is not affected by the current during the insulation and electrical auxiliary process, the stress condition F during the tension and compression process can be obtained through the thin plate tension and compression test gf ;

[0070] 14) Obtain the force magnitude of each part of the sample during the tension and compression process, and then use the formula F Ti =F A -F f -F gf The force F exerted on the ultra-thin titanium plate sample 2 during the tension and compression process can be calculated. Ti ;

[0071] 15) By F Ti The strains measured numerically and by DIC can be used to calculate the stress-strain curves of the electrically assisted ultra-thin titanium plate during tension-compression cyclic loading.

[0072] The above inventions are only several specific embodiments of the present invention. However, the embodiments of the present invention are not limited thereto. Any changes that can be conceived by those skilled in the art should fall within the scope of protection of the present invention.

Claims

1. An electrically assisted tension-compression cyclic loading device for ultra-thin titanium plates, characterized in that: include: Two outer specimens (1) used in conjunction with the ultra-thin titanium plate specimen (2), the two outer specimens (1) being fixed on both sides of the ultra-thin titanium plate specimen (2), the three forming a composite tensile-compression specimen, the ends of the ultra-thin titanium plate specimen (2) both extending beyond the ends of the outer specimens (1), the two sides of the composite tensile-compression specimen being fixed by a clamping assembly to apply a lateral force thereto; Two pairs of electric auxiliary clamps are respectively clamped at the two ends of the composite tensile and compressive specimen, each pair of the electric auxiliary clamps comprises two oppositely arranged clamps (11), the clamping surfaces of the clamps (11) are provided with a conductive structure (15), the conductive structure (15) is connected to an external power supply, when the composite tensile and compressive specimen is clamped on the clamps (11), the conductive structure (15) contacts the composite tensile and compressive specimen to transfer current to the composite tensile and compressive specimen through the conductive structure (15) to heat the composite tensile and compressive specimen, and the clamps (11) are connected to the loading end of the universal testing machine; The clamping assembly comprises: Two insulating gaskets are centrally symmetrically arranged on both sides of the composite tensile and compressive specimen, each of the insulating gaskets comprising a first insulating sheet (3) and a second insulating sheet (4) stacked along the extension direction of the ultra-thin titanium plate specimen (2); Two clamping plates are centrally symmetrically arranged on the outside of two insulating gaskets, and the outside of the clamping plates is connected to a lateral force adjustment component. Each of the clamping plates includes a first clamping plate (12) and a second clamping plate (13) stacked together, the first clamping plate (12) is fixedly connected to the corresponding first insulating sheet (3), and the second clamping plate (13) is fixedly connected to the corresponding second insulating sheet (4). The first insulating sheet (3) and the second insulating sheet (4), as well as the first clamping plate (12) and the second clamping plate (13) are slidably connected by a plurality of straight rods (10), so that the first insulating sheet (3) and the second insulating sheet (4), as well as the first clamping plate (12) and the second clamping plate (13) move synchronously along the extension direction of the ultra-thin titanium plate sample (2).

2. The ultra-thin titanium plate electrically assisted tension-compression cyclic loading device according to claim 1, characterized in that: The conductive structure (15) includes a conductive sheet (150) and a connecting sheet (151) connected as one body, wherein the conductive sheet (150) and the connecting sheet (151) are both made of conductive material, the conductive sheet (150) is located on the clamping surface of the chuck (11), and has serrations on the side thereof that contacts the composite tensile and compressive specimen, and a through groove (152) is also provided on the conductive sheet (150), the end of the outer specimen (1) is placed in the through groove (152), the ultra-thin titanium plate specimen (2) contacts the conductive sheet (150), and the connecting sheet (151) is connected to an external power supply.

3. The ultra-thin titanium plate electrically assisted tension-compression cyclic loading device according to claim 2, characterized in that: The resistivity of the outer sample (1) is 10 12 Ω·m-10 17 Ω·m.

4. The ultra-thin titanium plate electrically assisted tension-compression cyclic loading device according to claim 1, characterized in that: The upper and lower clamps of the universal testing machine correspondingly clamp two pairs of electric auxiliary clamps, and the clamp head (11) also has a positioning column (16) and a fixing groove (17), the positioning column (16) cooperates with the positioning groove of the universal testing machine, and the loading head of the universal testing machine is clamped in the fixing groove (17).

5. The ultra-thin titanium plate electrically assisted tension-compression cyclic loading device according to claim 1, characterized in that: The outer sample (1) has a thickness of 0.5 mm to 0.7 mm and is made of one of glass fiber composite materials, polyetheretherketone, or carbon fiber-glass fiber composite materials.

6. The ultra-thin titanium plate electrically assisted tension-compression cyclic loading device according to claim 5, characterized in that: The outer sample (1) and the ultra-thin titanium plate sample (2) are bonded and fixed by epoxy resin, and the thickness of the epoxy resin layer is 0.02 mm to 0.05 mm.

7. The ultra-thin titanium plate electrically assisted tension-compression cyclic loading device according to claim 1, characterized in that: The first insulating sheet (3) and the second insulating sheet (4), as well as the first clamping plate (12) and the second clamping plate (13), are each connected via a comb-like structure.

8. The ultra-thin titanium plate electrically assisted tension-compression cyclic loading device according to claim 1, characterized in that: The lateral force adjustment assembly includes: Two inner plates (9) are respectively placed on the outer sides of corresponding splints; Two outer plates (8) are placed on the outside of the corresponding inner plates (9), and the inner plates (9) and the outer plates (8) are both provided with sliding holes along the extension direction of the ultra-thin titanium plate specimen (2). The screws pass through the sliding holes in sequence and are fixed to the clamping plate and the insulating gasket. A spring adjustment block (6) is rotatably connected to one of the outer plates (8); The spring (5) has one end fixedly connected to the spring adjustment block (6) and the other end fixedly connected to the corresponding inner plate (9).

9. A test method based on the ultra-thin titanium plate electrically assisted tension-compression cyclic loading device according to any one of claims 1 to 8, characterized in that: The following steps are involved: Step 1: Prepare a composite tensile-compression specimen by fixing outer specimens (1) on both sides of an ultra-thin titanium plate specimen (2) to form a composite tensile-compression specimen; Step 2: Clamp the prepared composite tensile and compressive specimen onto the universal testing machine using an electric-assisted clamp. Apply lateral force to the composite tensile and compressive specimen on both sides through clamping components to secure it. Step 3: Set the required parameters for the tension and compression tests and conduct the tension and compression tests; Step 4: Observe whether the ultra-thin titanium plate specimen (2) buckles. If buckling occurs, adjust the lateral force. Repeat steps 1 to 4 until the ultra-thin titanium plate specimen (2) does not buckle, and obtain the lateral force corresponding to the case where no buckling occurs. Step 5: Use the lateral force corresponding to the non-buckling state to fix the remaining composite tension and compression specimens, and conduct tension and compression tests to obtain experimental data, and use the experimental data to obtain stress-strain curves.

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