Energy absorption structure with torsion curved surface and machining method and equipment of energy absorption structure

Abstract

The invention relates to an energy absorption structure with torsion curved surfaces and a processing method and equipment thereof, specifically, the two ends of a regular polygon pipe are fixed, and the multiple sections of torsion curved surfaces are formed on the pipe in the mode that the torsion directions are switched forwards and backwards, so that when the energy absorption structure bears loads, the torsion curved surfaces are stacked to form buckling folds; therefore, collision energy can be effectively absorbed.

Description

Technical Field

[0001] The invention belongs to the field of energy absorbing structures, and in particular relates to an energy absorbing structure with a torsion curved surface and a processing method and equipment thereof. Background Art

[0002] The energy-absorbing structure of the hollow slender square column is prone to lateral bending when subjected to a head-on collision. After the component is laterally bent, its energy absorption effect is greatly reduced. Therefore, how to ensure that the energy-absorbing component continues to be squeezed and deformed for as long as possible when subjected to a collision without lateral bending becomes the top priority in the structural design of the energy-absorbing component.

[0003] At present, there are mainly the following structural improvements for energy-absorbing components with hollow slender square column structures: 1. Inserting cutouts or protrusions at the belly and nodes of the energy-absorbing components that are prone to buckling solves the problem of lateral bending of the energy-absorbing components, thereby reliably achieving accordion-like crushing deformation. However, due to the limitation of its own volume, only about 70% of its own length can be obtained, and the disadvantage of too high initial peak load of the crushing reaction force has not been solved; 2. Through the hydraulic forming method, an energy-absorbing component with a spiral origami structure is manufactured, so that the crushing deformation of the energy-absorbing component is increased to about 90%, and the initial peak load is reduced, but , limited by the processing technology, the equipment and molds required for the processing of the energy-absorbing components of this structure are complex, the production cost is high, and there is a defect that the wall thickness of the component is significantly thinned locally; 3. The pipe is heated and then twisted to form a twisted surface on the surface of the pipe. Since this processing method is to twist the pipe as a whole, it has high requirements on the output torque of the processing equipment and may also cause deformation of the clamping part of the pipe. In addition, the clamps of the existing torsion processing equipment are poorly adaptable to different pipes, and after heating and twisting, it is impossible to ensure synchronous cooling of the inside and outside of the pipe, resulting in uneven texture inside the pipe after cooling, affecting performance. Summary of the invention

[0004] The purpose of the present invention is to provide an energy absorbing structure with a torsion curved surface and a processing method and equipment thereof, wherein a square tube material is divided into multiple stages along the axial direction, and a molded product can be obtained by repeating simple torsion molding in each stage. In addition, by adopting a method of heating only the torsion plastic deformation part, processing can be performed with a smaller processing load, and the clamp for fixing the square tube material can be simplified. Since complex processing equipment such as machinery is not required, only partial simple torsion molding is required, so the processing cost can be significantly reduced, and since no tensile deformation occurs inside, the problem of significant thinning of the wall thickness can be avoided.

[0005] To achieve this goal, the specific technical solutions are as follows:

[0006] An energy absorbing structure with a torsion curved surface has a main body which is a regular polygonal tubular structure. A first torsion curved surface and a second torsion curved surface are continuously and alternately distributed on the tubular structure. The first torsion curved surface and the second torsion curved surface have the same length and torsion angle, but opposite torsion directions.

[0007] A method for processing an energy absorbing structure with a torsion curved surface comprises the following steps:

[0008] S1 fixes both ends of the pipe;

[0009] S2 heats a portion of the pipe, twists the pipe after the heating is completed to form a first twisted curved surface, and then cools the first twisted curved surface portion;

[0010] S3: heating the portion of the tube adjacent to the first twisted curved surface, twisting the tube in the opposite direction with the same torque and twisting angle after the heating is completed to form a second twisted curved surface adjacent to the first twisted curved surface, and then cooling the portion of the second twisted curved surface;

[0011] S4: heating a portion of the tube adjacent to the second twisted curved surface, twisting the tube after heating to form a first twisted curved surface, and then cooling the portion of the first twisted curved surface;

[0012] S5 repeats steps S3 and S4 until the pipe processing is completed.

[0013] Furthermore, the pipe heating temperature refers to the following formula:

[0014]

[0015] Among them, T is the temperature, R is the resistance of the coil, I is the eddy current flowing, m is the mass of the square tube part being heated, C is the specific heat capacity, and t is the heating time.

[0016] Furthermore, the pipe heating temperature is 950°C.

[0017] Furthermore, the torque and torsion angle are obtained by finite element analysis after calculating the material parameters by the formula. The specific formula for determining the material parameters is as follows:

[0018]

[0019] Among them, σ y is the dynamic yield stress, σ y0 is the static yield stress, is the strain rate, c and p are material specific constants. Referring to the values ​​in the actual automobile collision analysis case, c is taken as 8000 and p is taken as 8.

[0020] Furthermore, the torsion angle is 5°.

[0021] A processing device for energy-absorbing structures with a torsion curved surface, wherein a fixed chuck and a rotating chuck are coaxially mounted on both sides of the frame, and heaters powered by a power supply and movable along the axial direction of the fixed chuck and the rotating chuck are mounted on the sides of the fixed chuck and the rotating chuck.

[0022] Furthermore, the sides of the fixed chuck and the rotating chuck are equipped with a first annular cooling outlet that can move axially along the fixed chuck and the rotating chuck, and a second cooling outlet that can extend into the pipe is also arranged at the fixed chuck, and the first cooling outlet and the second cooling outlet are connected to a cooling air source.

[0023] Furthermore, the claws of the fixed chuck and the rotating chuck are installed with detachable fixing fixtures matching the shape of the pipe.

[0024] Furthermore, the rotating chuck is installed in a fixed bracket with rollers installed on the frame through a wheel track arranged on the outer side, and is driven to rotate by any method of manpower or a motor powered by a power supply.

[0025] The beneficial effects of the present invention are:

[0026] (1) The energy absorbing structure involved in the present application is provided with a first torsion curved surface and a second torsion curved surface with opposite torsion directions on its side. Based on this continuous anti-torsion structure, the energy absorbing member can adjust the distribution of collision buckling wrinkles through the polygonal lines on the side, so that when the energy absorbing member is subjected to axial load, it is not easy to bend laterally and has good collision energy absorption performance. In addition, based on this continuous anti-torsion structure, the energy absorbing member can be stacked to form fine wrinkles when deformed, so that a better crushing deformation amount can be obtained.

[0027] (2) The present application divides the square tube material into multiple stages along the axial direction, and repeats simple torsion molding in each stage to obtain a molded product. In addition, by adopting a method of heating only the torsion plastic deformation part, processing can be performed with a smaller processing load, and the fixture for fixing the square tube material can be simplified. Since complex processing equipment such as machinery is not required, only partial simple torsion molding is required, so the processing cost can be significantly reduced, and since no tensile deformation occurs inside, the problem of significant thinning of the wall thickness can be avoided.

[0028] (3) The present application processes the pipe by heating and twisting. Compared with the existing processing equipment, the pipe can be formed only by simple twisting plastic deformation, and the plate thickness of the obtained formed product is almost the same as the original plate thickness. In addition, since the present equipment adopts a processing mode of step-by-step forming along the axial direction, there is no limit on the axial length of the pipe, making the processing equipment miniaturized.

[0029] (4) The present application provides a detachable and replaceable fixing fixture on the chuck. When pipes with different cross-sectional shapes need to be processed, the corresponding fixing fixture can be replaced, thereby improving the adaptability of the equipment.

[0030] (5) The present application is provided with a first cooling air outlet and a second cooling air outlet, which can simultaneously cool down the inner and outer walls of the heated pipe, so that the material inside the pipe is uniform, thereby ensuring the performance of the pipe after processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a structural front view of the energy absorbing structure;

[0032] Figure 2 It is a diagram of the collapsed state of the energy-absorbing structure after absorbing the collision energy;

[0033] Figure 3 It is a structural schematic diagram of the energy absorbing structure processing process;

[0034] Figure 4 It is the time series that forms the load diagram;

[0035] Figure 5 is the stress and plastic strain diagram;

[0036] Figure 6 is a graph of temperature and Young’s modulus;

[0037] Figure 7 is a graph of temperature and yield stress;

[0038] Figure 8 It is a diagram showing the relationship between heating temperature and torque for torsional plastic forming of energy absorbing structures;

[0039] Fig. 9 This is the wall thickness analysis diagram of the torsion part of the energy absorbing structure;

[0040] Fig.10 It is the distribution diagram of simulated wall thickness and measured wall thickness of the energy absorbing structure;

[0041] Fig.11 It is the crushing deformation performance diagram of the energy-absorbing structure under simulated extrusion and measured extrusion;

[0042] Fig.12 It is a graph of crushing deformation and reaction force;

[0043] Fig.13 It is the comparison result of the collision energy absorption;

[0044] Fig.14 This is the crushing deformation diagram of the energy absorbing structure when the rotation angle is set to 5°;

[0045] Fig.15 It is a top view of the structure of the energy absorbing structure processing equipment;

[0046] Fig.16 This is a right view of the internal structure of the first cooling air outlet;

[0047] Fig.17 This is the right side view of the structure of the clamp for mounting the claw;

[0048] Fig.18 It is a front view of the structure of the rotating chuck in the fixed bracket;

[0049] The meanings of the symbols in the figure are as follows:

[0050] Tubular structure 1, first torsion curved surface 2, second torsion curved surface 3, frame 4, fixed chuck 5, rotating chuck 6, heater 7, first cooling air outlet 8, second cooling air outlet 9, fixing fixture 10, wheel rail 11, roller 12, fixing bracket 13. DETAILED DESCRIPTION

[0051] An energy absorbing structure with a torsion surface, the main body of which is a regular polygonal tubular structure 1, on which a first torsion surface 2 and a second torsion surface 3 are continuously and alternately distributed, the first torsion surface 2 and the second torsion surface 3 have the same length and torsion angle, but opposite torsion directions.

[0052] Based on the first torsion surface 2 and the second torsion surface 3 distributed on the tubular structure 1, polygonal lines are formed on the outer side of the tubular structure 1, so that when a collision occurs, the distribution of collision buckling wrinkles can be adjusted to avoid lateral bending. At the same time, after the tubular structure 1 is deformed by force, small buckling wrinkles will accumulate, so it can effectively absorb collision energy.

[0053] A method for processing an energy absorbing structure with a torsion curved surface comprises the following steps:

[0054] S1 fixes both ends of the pipe;

[0055] S2 heats a portion of the pipe, twists the pipe after the heating is completed to form a first twisted curved surface, and then cools the first twisted curved surface portion;

[0056] S3: heating the portion of the tube adjacent to the first twisted curved surface, twisting the tube in the opposite direction with the same torque and twisting angle after the heating is completed to form a second twisted curved surface adjacent to the first twisted curved surface, and then cooling the portion of the second twisted curved surface;

[0057] S4: heating a portion of the tube adjacent to the second twisted curved surface, twisting the tube after heating to form a first twisted curved surface, and then cooling the portion of the first twisted curved surface;

[0058] S5 repeats steps S3 and S4 until the pipe processing is completed.

[0059] Furthermore, the pipe heating temperature refers to the following formula:

[0060]

[0061] Among them, T is the temperature, R is the resistance of the coil, I is the eddy current flowing, m is the mass of the square tube part being heated, C is the specific heat capacity, and t is the heating time.

[0062] Furthermore, the pipe heating temperature is 950°C.

[0063] Furthermore, the torque and torsion angle are obtained by finite element analysis after calculating the material parameters by the formula. The specific formula for determining the material parameters is as follows:

[0064]

[0065] Among them, σ y is the dynamic yield stress, σ y0 is the static yield stress, is the strain rate, c and p are material specific constants. Referring to the values ​​in the actual automobile collision analysis case, c is taken as 8000 and p is taken as 8.

[0066] Furthermore, the torsion angle is 5°.

[0067] A processing device for an energy-absorbing structure with a torsion surface, wherein a fixed chuck 5 and a rotating chuck 6 are coaxially mounted on both sides of a frame 4, and a heater 7 powered by a power supply and movable along the axial direction of the fixed chuck 5 and the rotating chuck 6 is mounted on the side of the fixed chuck 5 and the rotating chuck 6.

[0068] After fixing both ends of the pipe on the fixed chuck 5 and the rotating chuck 6, start the heater 7 to heat part of the pipe. After heating, rotate the rotating chuck 6 to twist the heated part of the pipe. After the twisted part cools down, move the heater 7 to heat the part adjacent to the twisted part, and then twist the pipe in the opposite direction. Repeat the above steps until the whole pipe is processed.

[0069] The heater 7 is an electromagnetic heater.

[0070] Furthermore, in order to quickly cool down the pipe after heating and twisting, a first annular cooling outlet 8 that can move axially along the fixed chuck 5 and the rotating chuck 6 is installed on the side of the fixed chuck 5 and the rotating chuck 6, and a second cooling outlet 9 that can extend into the pipe is also provided at the fixed chuck 5. The first cooling outlet 8 and the second cooling outlet 9 are connected to a cooling air source.

[0071] Since the inner and outer walls of the pipe can be cooled at the same time, the internal material of the pipe after cooling can be ensured to be uniform and consistent, thus ensuring the performance of the pipe.

[0072] The cooling air source is provided by a blower powered by a power supply.

[0073] Furthermore, in order to fix pipes with different cross-sectional shapes, the claws of the fixed chuck 5 and the rotating chuck 6 are installed with a detachable fixing fixture 10 that matches the shape of the pipe. When processing pipes with different cross-sectional shapes, the corresponding fixing fixture 10 can be replaced.

[0074] Furthermore, the rotating chuck 6 is installed in a fixed bracket 13 with a roller 12 installed on the frame 4 through a wheel track 11 set on the outer side, and is driven to rotate by any method of manpower or a motor powered by a power supply. If manpower is used, a person inserts a crowbar into the jack on the rotating chuck 6 to drive the rotating chuck 6 to rotate. If motor drive is used, a servo motor or a stepper motor drives the rotating chuck 6 to rotate through structures such as a transmission shaft or a transmission gear.

[0075] In particular, the above electrical appliances can be powered by batteries or mains electricity.

[0076] In this embodiment, the pipe material used is low carbon steel, and its various parameters refer to Figure 4 , 5 , 6, 7, with a length of 300 mm, a wall thickness of 1.6 mm, and a side length of 50 mm. The software LS-DYNA is used to analyze the heating torsion forming process, in which the number of nodes is 15101, the number of units of rectangular isoparametric shell units is 15000, the average unit size of the square tube material is 1.0 mm, and the length of each partial heating torsion deformation is 50 mm, which is the same as the side length of the section. The final torsion angle is determined to be 5°, the heating temperature is 950°C, and the average torque under 950°C is 346.83 Nm.

[0077] Based on the data of finite element analysis, combined with Figure 8 It can be seen that the average torque value of the pipe at 25°C is 1162.54Nm, while the average torque at 950°C is 346.83Nm. The torque required for processing is reduced by about 3.35 times, proving that the pipe can be processed with a smaller processing load at 950°C.

[0078] Based on the data of finite element analysis, combined with Fig. 9 , 10 It can be seen that the thickest part of the processed tube is 1.602mm, the thinnest part is 1.597mm, and the overall thickness variation is within 0.19%, showing the characteristics of uniform thickness distribution of the tube. In addition, the thickness of the tube cut 1 / 4 along the axial direction is measured using a micrometer with an accuracy of 0.01mm, and the measured results are all 1.60mm, which once again proves that the thickness distribution of the processed tube is uniform.

[0079] Crushing deformation performance test of energy-absorbing structure with torsion surface:

[0080] The crushing test was conducted using a self-signed testing machine. The self-signed testing machine used for the crushing test was AGX / R300KNG manufactured by Shimadzu Corporation. Before the crushing test, the cross-sections at both ends of the energy-absorbing structure with a torsion surface obtained by partial heating torsion forming were processed into flat surfaces to apply an axial compression load. The compression fixture of the self-signed testing machine was set to a moving speed of 5 mm / s, and the compression load was applied in the form of forced displacement.

[0081] At the same time, FEM is used to simulate the crushing of the energy-absorbing structure.

[0082] Combination Fig.11 The initial peak value of the crushing load obtained by the crushing test is 60.48 kN, and the average value is 31.91 kN. The initial peak value of the crushing load obtained by FEM analysis is 60.53 kN, and the average value is 30.78 kN. Therefore, the initial peak load values ​​and average values ​​of the two are quite close, indicating that the obtained crushing deformation load is reasonable.

[0083] From the overall trend, the initial peak load values ​​of both are relatively small, and the subsequent load values ​​do not drop significantly, and the crushing deformation has the characteristics of lasting for a long time. That is, there is no high initial peak load, and there is no bending during the crushing deformation process, and the crushing amount is long, which is an ideal crushing deformation mode.

[0084] Collision energy absorption performance test of energy-absorbing structure with torsion surface:

[0085] In order to conduct comparative analysis under the same conditions as much as possible, the spiral origami structure square tube and the square cross-section square tube are taken as the objects of comparative analysis. Therefore, the structural length of the analysis model is 375 mm, the cross-sectional circumference is 180 mm, the energy-absorbing structure with a torsion surface and the torsion angle of the spiral origami structure square tube are set to 5°, and the plate thickness distribution results and material properties obtained from the forming solution analysis are reflected in each collision analysis model. A concentrated mass of 1000 kg is applied to the upper end face of the analysis model, and the collision analysis is carried out at a collision speed of 15 m / s under the same conditions.

[0086] Finally, it was determined that in continuous axial crushing (unit: MJ), the energy absorption of the energy-absorbing structure with a torsion surface is 1.1 times that of the spiral origami structure square tube and 1.78 times that of the square cross-section tube, and has the best collision energy absorption performance. The specific data are as follows:

[0087]

[0088] According to the analysis of the applicant, when absorbing collision energy, the energy-absorbing structure with a torsional curved surface accumulates fine buckling wrinkles in sequence from the end surface, thereby having good collision energy absorption performance and providing a larger crushing deformation amount.

[0089] Study on the influence of torsion angle on the performance of energy-absorbing structures with torsion surfaces:

[0090] In order to determine the appropriate rotation angle, we will create analysis models with torsion curved surface structures with several rotation angles, perform collision analysis, and study them while comparing. The cross-sectional perimeter of the collision analysis model is 180 mm, the axial length is 375 mm, and the plate thickness is 1 mm. 65285 three-node shell elements with a side length of 1.5 mm are applied to the collision rigid body, and the number of nodes is set to 32851. As boundary conditions, an axial displacement is set at the upper boundary of the anti-torsion type folded structure, other displacements are constrained, and conditions for fully constraining the bottom boundary are given.

[0091] Depend on Fig.12 It can be seen that when the rotation angle exceeds 5°, the reaction force of the extrusion deformation gradually decreases with the increase of the rotation angle. When the rotation angle is 15° and 30°, as the fold line angle increases, the stiffness and reaction force decrease, and the curve gradually flattens.

[0092] Depend on Fig.13 It can be seen that the collision energy absorption of the torsion curved surface structure with a rotation angle of 5° is the largest, and its collision energy absorption is 6.83×10 6 J. The structure with a twisted curved surface with a rotation angle of 2.5° has a collision energy absorption amount similar to that of the structure with a twisted curved surface with a rotation angle of 5°, but Fig.14 As shown in the figure, since the buckling induction effect of the torsion curved surface structure is almost insignificant, when the torsion curved surface structure is further extended, the crushing deformation may occur in lateral bending. It can be confirmed that in the torsion structure with a rotation angle of 5° or more, the collision energy absorption amount decreases due to the reduction of the torsion reaction force.

[0093] Therefore, setting the rotation angle to 5° is more appropriate because the guiding effect of the fold line on the buckling folds can be ensured and the reaction force can be kept as high as possible.

Claims

1. An energy absorbing structure with a torsion surface, the main body of which is a regular polygonal tubular structure (1), characterized in that: The tubular structure (1) is provided with first twisted curved surfaces (2) and second twisted curved surfaces (3) which are continuously and alternately distributed. The first twisted curved surfaces (2) and the second twisted curved surfaces (3) have the same length and twist angle, but opposite twist directions.

2. A method for processing an energy absorbing structure having a torsion surface, characterized in that: The following steps are involved: S1 fixes both ends of the pipe; S2 heats a portion of the pipe, twists the pipe after the heating is completed to form a first twisted curved surface, and then cools the first twisted curved surface portion; S3: heating the portion of the tube adjacent to the first twisted curved surface, twisting the tube in the opposite direction with the same torque and twisting angle after the heating is completed to form a second twisted curved surface adjacent to the first twisted curved surface, and then cooling the portion of the second twisted curved surface; S4: heating a portion of the tube adjacent to the second twisted curved surface, twisting the tube after heating to form a first twisted curved surface, and then cooling the portion of the first twisted curved surface; S5 repeats steps S3 and S4 until the pipe processing is completed.

3. The method for processing an energy absorbing structure with a torsion curved surface according to claim 2, characterized in that: The pipe heating temperature refers to the following formula: Among them, T is the temperature, R is the resistance of the coil, I is the eddy current flowing, m is the mass of the square tube part being heated, C is the specific heat capacity, and t is the heating time.

4. The method for processing an energy absorbing structure with a torsion curved surface according to claim 3, characterized in that: The pipe heating temperature is 950°C.

5. The method for processing an energy absorbing structure with a torsion curved surface according to claim 2, characterized in that: The torque and torsion angle are obtained by calculating the material parameters by the formula and then by finite element analysis. The specific formula for determining the material parameters is as follows: Among them, σ y is the dynamic yield stress, σ y0 is the static yield stress, is the strain rate, c and p are material specific constants. Referring to the values ​​in the actual automobile collision analysis case, c is taken as 8000 and p is taken as 8.

6. The method for processing an energy absorbing structure with a torsion curved surface according to claim 2, characterized in that: The twisting angle is 5°.

7. An energy absorbing structure processing device having a torsion surface, characterized in that: A fixed chuck (5) and a rotating chuck (6) are coaxially mounted on both sides of the frame (4), and a heater (7) powered by a power source and movable along the axial direction of the fixed chuck (5) and the rotating chuck (6) is mounted on the side surfaces of the fixed chuck (5) and the rotating chuck (6).

8. The energy absorbing structure processing equipment with a torsion curved surface according to claim 7, characterized in that: The fixed chuck (5) and the rotating chuck (6) are provided with an annular first cooling air outlet (8) which can move along the axial direction of the fixed chuck (5) and the rotating chuck (6), and a second cooling air outlet (9) which can extend into the pipe is also provided at the fixed chuck (5), and the first cooling air outlet (8) and the second cooling air outlet (9) are connected to a cooling air source.

9. The energy absorbing structure processing equipment with a torsion curved surface according to claim 7, characterized in that: The clamping claws of the fixed chuck (5) and the rotating chuck (6) are installed with a detachable fixing fixture (10) matching the shape of the pipe.

10. The energy absorbing structure processing equipment with a torsion curved surface according to claim 7, characterized in that: The rotating chuck (6) is installed in a fixed bracket (13) provided on a frame (4) and equipped with a roller (12) through a wheel track (11) provided on the outer side, and is driven to rotate by either human power or a motor powered by a power source.

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