Thin-wall formed part preparation device and method based on double-gradient structure

Abstract

The invention relates to an incremental forming preparation device and method for preparing a thin-wall component with a double-gradient structure based on thermal coupling cyclic loading, and the device comprises a clamp supporting tool, a driving device and a rotatable tool head, the clamp supporting tool is used for clamping a to-be-formed plate, exerting back reaction force when the plate is formed in the forward direction and providing a supporting effect when the plate is formed in the reverse direction. The driving control unit adjusts the deformation condition of the local area of the plate through the motion state (pressing amount and rotating speed) and the motion track of the tool head, and the high-performance thin-wall forming part of the double-gradient structure with the grain forward gradient and the dislocation density reverse gradient in the thickness direction is prepared under the thermal-mechanical coupling cyclic loading condition. Compared with the prior art, the novel double-gradient structure is prepared through the thermal coupling incremental forming technology, the thin-wall formed part is prepared at the same time, the toughness performance of the formed part can be remarkably improved, the machining cost is effectively reduced, and the machining efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of material heterogeneous organization design, and in particular to a device and method for preparing a thin-walled formed part based on a dual gradient structure. Background Art

[0002] With the continuous development of new material preparation technology and material structure design, people are increasingly demanding advanced materials with excellent strength and toughness in the fields of aerospace, rail transportation, nuclear power, petroleum and chemical industry. However, traditional engineering materials have an "inverted" relationship between strength and toughness, that is, the strength and toughness can conform to the concave "banana" curve relationship. When using traditional methods to improve the strength of materials, their toughness is often sacrificed. Therefore, how to achieve the synergistic improvement of the strength and toughness of engineering materials is an urgent problem to be solved.

[0003] Existing studies have shown that by regulating the heterogeneity between components, such as the gradient distribution of grain size along a certain scale direction, it is possible to break through the "mutually exclusive" relationship between strength and toughness, making the "banana" curve convex. Common preparation processes for grain gradient heterogeneous materials include surface mechanical treatment, surface shot peening, magnetron sputtering, and 3D printing. The main principle is to use surface mechanical treatment or energy deposition to make the material produce gradient deformation from the surface to the core under gradient distribution of strain, strain rate or temperature and other processing conditions, thereby obtaining heterogeneous materials with a gradient grain size structure.

[0004] Among them, surface mechanical treatment and surface shot peening belong to post-forming processing procedures. Compared with magnetron sputtering and 3D printing, which are integrated processes for part forming and gradient preparation, the procedures are more complicated; 3D printing and magnetron sputtering have the defects of being expensive and costly. In addition, the grain gradient heterogeneous materials prepared by traditional processes such as surface mechanical grinding will introduce large residual stresses inside the sample. In summary, although the above-mentioned traditional grain gradient structure preparation process can improve the strength and toughness of the material, the improvement is not significant; and the existing research can only be prepared on sheets or bars, that is, it has not yet been applied to formed parts, so it does not have engineering application value for the time being. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and to provide a device and method for preparing thin-walled formed parts based on a dual gradient structure. A new dual gradient structure is prepared through thermal-mechanical coupling progressive forming technology, and thin-walled formed parts are prepared at the same time, which can effectively improve the strength and toughness of the formed parts.

[0006] The object of the present invention can be achieved by the following technical solutions: A thin-walled formed part preparation device based on a dual gradient structure, comprising a fixture support tooling, a support die is arranged below the fixture support tooling, a tool head is arranged above the fixture support tooling, the tool head is connected to the output end of the spindle motor, the input end of the spindle motor is connected to a drive control unit, the drive control unit is connected to a host, and the fixture support tooling is used to clamp the sheet material to be formed;

[0007] The support mold is used to apply a back force when the sheet material is formed in the forward direction and to produce a supporting effect when the sheet material is formed in the reverse direction;

[0008] The drive control unit adjusts the motion state of the tool head by controlling the working state of the spindle motor under the corresponding instructions of the host, so as to perform thermal-mechanical coupled progressive forming processing on the sheet material, prepare a double-gradient structure including the coupling of the positive gradient of the grain and the reverse gradient of the dislocation, and obtain the corresponding thin-walled formed parts at the same time.

[0009] Furthermore, the host is connected to a temperature detector, which is used to detect the surface temperature data of the sheet material in real time and transmit it to the host, and the host changes the instructions output to the drive control unit in real time according to the surface temperature of the sheet material.

[0010] Furthermore, the temperature detector is provided with a display device for displaying the current temperature change of the sheet material surface in real time.

[0011] Furthermore, the temperature detector is specifically a thermal imager.

[0012] Furthermore, the fixture support tooling is composed of a combination of detachable "I"-shaped fixtures, which are fixed on the processing plane and can be assembled and disassembled according to the size of the formed part.

[0013] Furthermore, the supporting mold is fixed to the processing plane and is located at the bottom of the sheet to be formed.

[0014] Furthermore, the tool head is a cylinder, and the transition area between the end face of the tool head and the main body is a transition fillet.

[0015] Furthermore, the tool head is made of non-magnetic tungsten steel or hard alloy.

[0016] A method for preparing a thin-walled formed part based on a dual gradient structure comprises the following steps:

[0017] S1. Preliminarily perform 3D modeling on the target formed part and generate the corresponding 3D processing trajectory. Import the 3D processing trajectory into the host;

[0018] S2. Using the relationship between the dynamic recrystallization behavior of the material and the deformation conditions (temperature, strain rate and strain, etc.), according to the spatial characteristics of the target dual-gradient structure, set the spatial gradient distribution law of the deformation conditions. According to the analytical model of deformation conditions and processing parameters, calculate and set the processing parameters;

[0019] S3. Fix the support mold on the processing plane and clamp the sheet to be formed on the fixture support fixture. Calibrate the initial position of the tool head and the height of the cutter. The host transmits the three-dimensional processing trajectory and processing parameter instructions to the drive control unit, and combines the real-time feedback of the sheet surface temperature to drive the tool head through the spindle motor to perform thermal-mechanical coupling progressive forming on the sheet. If the sheet temperature does not meet the prediction results of the analytical model, correct the analytical model and reset the processing parameters;

[0020] S4. A dual gradient structure including a coupled grain forward gradient and a dislocation reverse gradient is prepared, and a corresponding thin-walled formed part is obtained at the same time.

[0021] Furthermore, the processing parameters include the pressing amount, the rotation speed of the tool head and the feed speed.

[0022] Furthermore, the specific process of the tool head performing thermal-mechanical coupled progressive forming processing on the sheet material in step S3 is as follows: according to the currently set processing parameters, the tool head rotates at high speed and contacts the sheet material, generates heat by frictional heat generation and transfers the heat to the surface of the sheet material, and at the same time, the tool head is connected to the spindle motor to transfer the load required for sheet material forming, so that the sheet material completes local deformation under the point contact of the tool head. Thereafter, the tool head moves according to the three-dimensional processing trajectory to complete the processing layer by layer. During the progressive process, the tool head transfers the heat and forming load to the surface of the sheet material according to the three-dimensional processing trajectory, completing the simultaneous preparation and processing of the thick dual gradient structure of the sheet material and the geometric shape of the formed part.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] The present invention provides a fixture support tooling for clamping the sheet material to be formed, and a support die is provided under the fixture support tooling for applying a back force when the sheet material is formed in the forward direction and generating a supporting effect when the sheet material is formed in the reverse direction, and a driving control unit is provided to adjust the motion state of the tool head by controlling the working state of the spindle motor under the corresponding instruction of the host, so as to perform a thermomechanical coupling progressive forming process on the sheet material, thereby preparing a dual-gradient structure and simultaneously obtaining a corresponding thin-walled formed part. The dual-gradient structure includes a heterogeneous structure in which a grain forward gradient and a dislocation reverse gradient are coupled, which can effectively improve the problem of insufficient hardening degree of the core, and realize the shape processing and performance optimization of the component while preparing the dual-gradient structure, which can effectively improve the strength and toughness of the thin-walled formed part, and effectively reduce the processing procedures and costs, and significantly improve the production efficiency.

[0025] The present invention is provided with a temperature detector for real-time detection of sheet material surface temperature data and transmission to a host computer, which changes the instructions output to a drive control unit in real time according to the sheet material surface temperature. If the sheet material surface temperature does not reach the expected level or exceeds the expected level, the processing parameters are adjusted accordingly, thereby ensuring precise adjustment of the processing process, thereby preparing a product that conforms to the target formed part.

[0026] The present invention utilizes the friction between the tool head and the sheet to generate heat, which promotes dynamic recrystallization of the sheet surface due to high temperature and large deformation, forming a dual gradient structure in which a fine grain positive gradient and a dislocation reverse gradient coexist along the thickness direction. Compared with traditional processes such as mechanical grinding and laser impact that utilize large surface deformation to obtain a fine grain gradient structure, the present invention does not introduce additional residual stress, and can effectively improve the stability and reliability of the formed parts during subsequent processing and use, thereby achieving low-cost, high-efficiency, and easy-to-control real-time dual gradient structure preparation, overcoming the shortcomings of traditional gradient structure preparation methods such as high cost, low efficiency, difficult to control performance, and large residual stress. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the overall scheme of the present invention;

[0028] Figure 2 It is a schematic diagram of the structure of the device of the present invention;

[0029] Figure 3 It is a schematic diagram of the method flow of the present invention;

[0030] Figure 4 It is a schematic diagram of the application process of the embodiment;

[0031] Figure 5a-5b A model of a target formed part and a schematic diagram of a three-dimensional processing trajectory in the embodiment;

[0032] Figure 6 The microstructure diagrams of different dual gradient structures in the embodiments;

[0033] Figure 7a-7b It is a graph showing the mechanical properties of different dual gradient structures in the embodiment;

[0034] Markings in the figure: 1. Fixture support tooling, 2. Support mold, 3. Tool head, 4. Spindle motor, 5. Main machine, 6. Drive control unit, 7. Temperature detector. DETAILED DESCRIPTION

[0035] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] Example

[0037] like Figure 1 As shown, the present invention proposes a progressive forming preparation scheme for preparing thin-walled components with dual gradient structures based on thermomechanical coupling cyclic loading. On the one hand, a thin-walled component progressive forming device is designed and the thin-walled component preparation is completed; on the other hand, a dual gradient structure of grains and dislocations is introduced into the thin-walled component to improve the strength and toughness of the thin-walled component. Among them, the device mainly includes a fixture support tooling, a driving device, and a rotatable tool head. The fixture support tooling is used to clamp the sheet to be formed and apply a back force when the sheet undergoes forward forming and provide support when the sheet undergoes reverse forming; the driving control unit adjusts the deformation conditions (temperature, strain rate and strain) of the local area of ​​the sheet through the motion state (pressure amount, rotation speed) and motion trajectory of the tool head, and prepares a high-performance thin-walled formed part with a dual gradient structure with a forward gradient of grains and a reverse gradient of dislocation density along the thickness direction under thermomechanical coupling cyclic loading conditions. This scheme mainly uses thermomechanical coupling incremental forming technology to prepare a new dual-gradient structure and simultaneously prepare thin-walled formed parts. The dual-gradient structure includes a heterogeneous structure in which a positive gradient of the grain is coupled with a reverse gradient of the dislocation, which can effectively improve the problem of insufficient hardening of the core, and realize shape processing and performance optimization of the component while preparing the dual-gradient structure, which can effectively improve the strength and toughness of thin-walled formed parts, while effectively reducing processing steps and costs, and significantly improving production efficiency.

[0038] like Figure 2 As shown, a thin-walled formed part preparation device based on a dual gradient structure includes a fixture support tool 1, a support die 2 is arranged below the fixture support tool 1, a tool head 3 is arranged above the fixture support tool 1, the tool head 3 is connected to the output end of the spindle motor 4, the input end of the spindle motor 4 is connected to the drive control unit 6, the drive control unit 6 is connected to the host 5, and the fixture support tool 1 is used to clamp the sheet material to be formed;

[0039] The support mold 2 is used to apply a back force when the sheet metal is formed in the forward direction and to provide a support function when the sheet metal is formed in the reverse direction;

[0040] Under the corresponding instructions of the host machine 5, the drive control unit 6 adjusts the movement state of the tool head 3 by controlling the working state of the spindle motor 4, so as to perform thermal-mechanical coupled progressive forming treatment on the sheet material, thereby preparing a double gradient structure including the coupling of the positive gradient of the grain and the reverse gradient of the dislocation, and obtaining the corresponding thin-walled formed parts.

[0041] It should be noted that the incremental forming technology is a sheet metal processing method based on the milling trajectory generation algorithm, which is widely used in the manufacturing industry. Due to its low processing cost and highly flexible manufacturing process, it is widely used in the field of rapid prototyping of small batches, customization and complex parts. The main process idea of ​​incremental forming technology is "local deformation, accumulation step by step", which is similar to the process and deformation mechanism of mechanical stirring grinding technology. This scheme takes into account that the tool head can be set to a rotating mode on the CNC machine tool, and a large amount of friction heat will be generated when it contacts the workpiece surface, causing the sheet metal to undergo dynamic recrystallization under the action of the thermal effect, thereby obtaining a fine-grained gradient structure with no residual stress or low residual stress.

[0042] In addition, the host 5 is connected to a temperature detector 7, which is used to detect the surface temperature data of the sheet in real time and transmit it to the host 5, and the host 5 changes the instructions output to the drive control unit 6 in real time according to the surface temperature of the sheet. The temperature detector 7 is provided with a display screen for displaying the current surface temperature change of the sheet in real time.

[0043] In this embodiment, the above device is built in combination with a three-axis CNC milling machine. The fixture support tool 1 is fixed on the processing plane of the milling machine and fixed around the sheet material to clamp the sheet material to be formed. The fixture support tool 1 is composed of a detachable "I"-shaped fixture, which can be assembled and disassembled according to the size of the formed part.

[0044] The support die 2 is also fixed to the milling machine processing plane and to the bottom of the sheet material, so as to apply an additional back reaction force when the sheet material is deformed in the forward direction, and to play a supporting role when the sheet material is reversely formed;

[0045] The tool head 3 is connected to the spindle motor 4, and the motion trajectory of the tool head 3 is controlled by the drive control unit 6 to contact the sheet material. The main body of the tool head 3 is a cylinder with a length of 120 mm and a diameter of 20 mm. The end face of the tool head is a circular plane of 10 mm. The transition area between the end face and the main body is a transition fillet with a radius of 5 mm. The tool head is made of non-magnetic tungsten steel or cemented carbide, which still maintains high strength and hardness at 800°C. The tool head has two degrees of freedom, namely, the vertical coordinate axis translational freedom and the rotational freedom. The two coordinate axis translational freedoms of the formed part in the processing plane are satisfied by the milling machine processing plane.

[0046] In this embodiment, the temperature detector 7 is a thermal imager, which is fixed on the processing plane of the milling machine, and the probe is aligned with the contact position between the tool head 3 and the sheet material to record the surface temperature of the sheet material in real time.

[0047] The above device is used to realize a method for preparing a thin-walled formed part based on a dual gradient structure, such as Figure 3 As shown, the following steps are included:

[0048] S1. Preliminarily perform 3D modeling on the target formed part and generate the corresponding 3D processing trajectory. Import the 3D processing trajectory into the host;

[0049] S2. Using the relationship between the dynamic recrystallization behavior of the material and the deformation conditions (temperature, strain rate and strain, etc.), according to the spatial characteristics of the target dual-gradient structure, set the spatial gradient distribution law of the deformation conditions. According to the analytical model of deformation conditions and processing parameters, calculate and set the processing parameters;

[0050] S3. Fix the support mold on the processing plane and clamp the sheet to be formed on the fixture support fixture. Calibrate the initial position of the tool head and the height of the cutter. The host transmits the three-dimensional processing trajectory and processing parameter instructions to the drive control unit, and combines the real-time feedback of the sheet surface temperature to drive the tool head through the spindle motor to perform thermal-mechanical coupling progressive forming on the sheet. If the sheet temperature does not meet the prediction results of the analytical model, correct the analytical model and reset the processing parameters;

[0051] S4. A dual gradient structure including a coupled grain forward gradient and a dislocation reverse gradient is prepared, and a corresponding thin-walled formed part is obtained at the same time.

[0052] In step S3, the specific process of the tool head performing thermal-mechanical coupled progressive forming processing on the sheet material is as follows: according to the currently set processing parameters, the tool head rotates at high speed to contact the sheet material, generates heat by frictional heating and transfers the heat to the surface of the sheet material, and at the same time, the tool head is connected to the spindle motor to transfer the load required for sheet material forming, so that the sheet material completes local deformation under the point contact of the tool head. Thereafter, the tool head moves according to the three-dimensional processing trajectory to complete the processing layer by layer. In the progressive process, the tool head transfers the heat and forming load to the sheet material surface according to the three-dimensional processing trajectory, completing the simultaneous preparation and processing of the thick dual gradient structure of the sheet material and the geometric shape of the formed part.

[0053] The application process of this embodiment is as follows Figure 4 As shown, including:

[0054] Step 1: Pre-treat the sheet to be formed (316L stainless steel sheet), use sandpaper to grind the oxide layer on the surface of the sheet until a uniform and flat surface with a metallic luster is exposed, and apply a layer of high-temperature lubricating grease about 0.1-0.2mm thick on the surface of the sheet to be formed.

[0055] Step 2: Using the relationship between the dynamic recrystallization behavior of the material and the deformation conditions (temperature, strain rate, strain, etc.), according to the spatial characteristics of the target dual-gradient structure, set the spatial gradient distribution law of the deformation conditions. According to the analytical model of deformation conditions and processing parameters, calculate and set the processing parameters. Figure 5a and 5bAs shown, the geometric shape of the formed part is constructed using 3D modeling software, a 3D CNC milling machine processing trajectory is generated, and the processing trajectory is exported into NC (Numeric Control) code format.

[0056] Among them, the processing parameters controlled by the drive control unit generally refer to the forming angle, the amount of pressure, the tool head rotation speed and the feed speed. In this embodiment, the forming angle and the feed speed are related to the geometric shape of the thin-walled formed part and are set to 40° and 1500 mm / min respectively; the tool head rotation speed and the amount of pressure determine the deformation conditions of the sheet, and the deformation conditions further affect the spatial distribution of the dual gradient structure. In this embodiment, the following model is used to calculate the deformation conditions and processing parameters for 316L stainless steel sheet:

[0057]

[0058] Where: X DRX is the volume fraction of dynamic recrystallization; T is the deformation temperature; ε is the strain magnitude; is the strain rate; Z is the Zener-Hollomon parameter; ε c is the microstructural critical strain at the starting point of dynamic recrystallization, which is related to the Z parameter; ε * is the strain at the maximum recrystallization rate, which is also related to the Z parameter; Q is the thermal deformation activation energy; R is the gas constant, and A, n and α are all material constants to be determined.

[0059] In the above model, after removing the undetermined material constants, the free variables are deformation conditions such as deformation temperature, strain and strain rate. Therefore, the recrystallization volume fraction can be calculated based on the deformation conditions, and then the spatial distribution of the dual gradient structure can be regulated. The deformation conditions are determined by the processing parameters. In this embodiment, based on the experience and literature of the thermomechanical coupling incremental forming process for 316L stainless steel sheet, the processing parameters under certain deformation conditions are calculated according to the following model.

[0060] The temperature calculation formula is:

[0061]

[0062] Where: T is the processing temperature; T m is the melting point of the material; ω is the tool head rotation speed; v is the feed speed; k and γ are fitting parameters.

[0063] The strain calculation formula is:

[0064]

[0065] Where: t is the sum of the bending strain and tensile strain of the sheet; ε sis the shear strain on the sheet surface; R p is the tool head size; t P is the target depth; t g is the final thickness of the sheet; t0 is the original sheet thickness; Δt is the deformation time; h is the width of the surface heat affected zone; r is the horizontal distance from the center of the tool head; θ is the angle between the calculation point and the horizontal moving direction.

[0066] The strain rate calculation formula is:

[0067] Surface contact area:

[0068] Internal deformation area:

[0069] in: is the strain rate; R t C is the tool head fillet radius; t is the thermal conductivity of the sheet; G t is the temperature gradient, which can be calculated based on the temperature measurement value; F z is the forming load, which can be measured; μ is the friction coefficient; β is the forming angle.

[0070] According to the above formula, the relationship model between processing parameters, deformation conditions and recrystallization volume fraction can be established when preparing dual gradient structures by thermal-mechanical coupled incremental forming process of 316L stainless steel. It should be noted that this relationship model contains many empirical formulas, and the prediction results of the actual dual gradient structure can only provide a reference for the selection of processing parameters.

[0071] According to the calculation results of the above relationship model, the processing window used for 316L stainless steel plate is: tool head rotation speed 2000-5000RPM, downward pressure 0.1-0.3mm, forming angle 40°, feed speed 1500mm / min. In the specific incremental forming process, the tool head rotation speed and downward pressure are adjusted accordingly according to the real-time sheet surface temperature.

[0072] Step 3: Import the NC code file into the CNC milling machine host and set the tool head rotation speed and feed speed in the host.

[0073] Step 4: Fix the support mold on the milling machine processing plane and clamp the sheet to be formed on the fixture and support tooling.

[0074] Step 5: Calibrate the initial position of the tool head and the cutting height, import the processing trajectory NC code in the host into the drive control unit, and drive the tool head to start moving according to the processing trajectory.

[0075] Step 6: Turn on the temperature detector and start the machine tool; the tool head performs processing according to the preset motion trajectory, rotation speed and feed speed, and promptly cleans the cutting debris generated when the tool head contacts the sheet surface;

[0076] During the forming process, the tool head rotates at high speed and contacts the sheet material, generating heat through frictional heating and transferring the heat to the sheet material surface. At the same time, the tool head is connected to the spindle motor to transfer the load required for sheet material forming, so that the sheet material is locally deformed under the point contact of the tool head. After that, the tool head completes the processing layer by layer under the motion trajectory provided by the drive control unit. In the progressive process, the tool head transfers the heat and forming load to the sheet material surface according to the preset processing trajectory, completing the simultaneous preparation and processing of the thick dual gradient structure of the sheet material and the geometric shape of the formed part.

[0077] Step 7: During the processing, use a thermal imager to detect the temperature change of the sheet metal surface in real time. If the temperature does not reach the expected level or exceeds the expected level, return to step 3 to adjust the tool head rotation speed and pressure.

[0078] Step 8: After the processing is completed, turn off the milling machine switch, remove the processed parts, and clean the processing debris and residual lubricating grease on the surface of the parts.

[0079] Step 9: Wire-cut the formed part to obtain tensile specimens and microscopic specimens, grind the surface to relevant experimental standards, and then perform electron backscatter diffraction (EBSD) characterization and uniaxial tensile specimens to verify the dual gradient structure and mechanical properties of the formed part.

[0080] The results of EBSD characterization and uniaxial tensile test are as follows: Figure 6 , Figure 7a , Figure 7b As shown. Figure 6 It can be seen that dual-gradient structural parts with different grain positive gradients and dislocation reverse gradients can be prepared according to the thermomechanical coupling incremental forming process. Figure 7a-7b It can be seen that by changing the process parameters such as the pressing amount, the tool head rotation speed and the feed speed, formed parts with different strength and toughness combinations can be obtained.

[0081] In summary, this scheme uses thermomechanical coupling progressive forming technology to prepare a dual-gradient structure with high strength and high toughness. This dual-gradient structure includes a heterogeneous structure in which the positive gradient of the grain is coupled with the reverse gradient of the dislocation. It can effectively improve the problem of insufficient hardening of the core of the traditional fine-grained gradient structure, and its mechanical properties have absolute advantages over other similar materials. This scheme only requires the use of a three-axis CNC milling machine and a matching forming fixture. The process is simple and the cost is low. The heat generated by friction between the tool head and the sheet surface can be effectively controlled by adjusting the speed, feed speed and pass pressure of the milling machine. That is, by simply adjusting the processing parameters of the milling machine, the spatial random distribution of the output heat can be achieved, and then the precise adjustment of the dual-gradient structure can be completed, and formed parts with different strength and toughness combinations can be obtained.

[0082] At the same time, the use of this scheme to prepare a dual-gradient structure can simultaneously achieve shape processing and performance optimization of the component, effectively reduce processing procedures and costs, and significantly improve production efficiency. In addition, when this scheme uses thermal-mechanical coupling progressive forming technology to prepare a dual-gradient structure, the main principle of surface grain refinement is dynamic recrystallization. Compared with traditional processes such as mechanical grinding and laser shock that use large surface deformation to obtain a fine-grained gradient structure, no additional residual stress is introduced, which can effectively improve the stability and reliability of the formed parts during subsequent processing and use.

Claims

1. A device for preparing thin-walled formed parts based on a dual gradient structure, characterized in that: The invention comprises a fixture support tool (1), wherein a support die (2) is arranged below the fixture support tool (1), and a tool head (3) is arranged above the fixture support tool (1), wherein the tool head (3) is connected to the output end of a spindle motor (4), and the input end of the spindle motor (4) is connected to a drive control unit (6), and the drive control unit (6) is connected to a host computer (5), and the fixture support tool (1) is used for clamping a sheet material to be formed; The support mold (2) is used to apply a back force when the sheet material is being formed in the forward direction, and to produce a supporting effect when the sheet material is being formed in the reverse direction; The drive control unit (6) adjusts the motion state of the tool head (3) by controlling the working state of the spindle motor (4) under the corresponding instructions of the host computer (5), so as to perform a thermal-mechanical coupled progressive forming process on the sheet material, thereby preparing a dual-gradient structure including a coupled grain forward gradient and a dislocation reverse gradient, and simultaneously obtaining a corresponding thin-walled formed part.

2. The device for preparing thin-walled formed parts based on a dual gradient structure according to claim 1, characterized in that: The host (5) is connected to a temperature detector (7), which is used to detect the surface temperature data of the sheet metal in real time and transmit the data to the host (5). The host (5) changes the instructions output to the drive control unit (6) in real time according to the surface temperature of the sheet metal.

3. The device for preparing thin-walled formed parts based on a dual gradient structure according to claim 2, characterized in that: The temperature detector (7) is provided with a display device for displaying the current temperature change of the plate surface in real time.

4. The device for preparing thin-walled formed parts based on a dual gradient structure according to claim 1, characterized in that: The clamp support tooling (1) is composed of a combination of detachable "I"-shaped clamps, fixed on a processing plane, and can be assembled and disassembled according to the size of the formed part.

5. The device for preparing thin-walled formed parts based on a dual gradient structure according to claim 4, characterized in that: The supporting mold (2) is fixed on the processing plane and is located at the bottom of the sheet material to be formed.

6. The device for preparing thin-walled formed parts based on a dual gradient structure according to claim 1, characterized in that: The tool head (3) is a cylinder, and the transition area between the end face of the tool head (3) and the main body is a transition fillet.

7. The device for preparing thin-walled formed parts based on a dual gradient structure according to claim 1, characterized in that: The tool head (3) is made of non-magnetic tungsten steel or hard alloy.

8. A method for preparing a thin-walled formed part based on a dual gradient structure, applied to a device for preparing a thin-walled formed part based on a dual gradient structure as claimed in claim 1, characterized in that: The following steps are involved: S1, pre-modeling the target formed part in three dimensions, generating a corresponding three-dimensional processing trajectory, and importing the three-dimensional processing trajectory into a host computer; S2. Using the relationship between the dynamic recrystallization behavior of the material and the deformation conditions, according to the spatial characteristics of the target dual-gradient structure, the spatial gradient distribution law of the deformation conditions is set, and according to the analytical model of the deformation conditions and the processing parameters, the processing parameters are calculated and set; S3, fix the support die on the processing plane, clamp the sheet to be formed on the fixture support fixture, calibrate the initial position of the tool head and the height of the cutter, and the host transmits the three-dimensional processing trajectory and processing parameter instructions to the drive control unit, and combines the real-time feedback of the sheet surface temperature, and drives the tool head through the spindle motor to perform thermal-mechanical coupling progressive forming on the sheet. If the sheet temperature does not meet the prediction results of the analytical model, the analytical model is corrected and the processing parameters are reset; S4. A dual gradient structure including a coupled grain forward gradient and a dislocation reverse gradient is prepared, and a corresponding thin-walled formed part is obtained at the same time.

9. A method for preparing a thin-walled formed part based on a dual gradient structure according to claim 8, characterized in that: The processing parameters include the pressing amount, the rotation speed of the tool head and the feed speed.

10. The method for preparing a thin-walled formed part based on a dual gradient structure according to claim 8, characterized in that: The specific process of the tool head performing thermal-mechanical coupled progressive forming processing on the sheet material in step S3 is as follows: according to the currently set processing parameters, the tool head rotates at high speed and contacts the sheet material, generates heat by frictional heating and transfers the heat to the surface of the sheet material, and at the same time, the tool head is connected to the spindle motor to transfer the load required for sheet material forming, so that the sheet material completes local deformation under the point contact of the tool head. Thereafter, the tool head moves according to the three-dimensional processing trajectory to complete the processing layer by layer. In the progressive process, the tool head transfers the heat and forming load to the surface of the sheet material according to the three-dimensional processing trajectory, completing the simultaneous preparation and processing of the thick dual gradient structure of the sheet material and the geometric shape of the formed part.

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