A composite material structure bushing reinforcing method based on electromagnetic loading

Abstract

The application discloses a composite material structure bushing reinforcing method based on electromagnetic loading, which uses electromagnetic loading to complete the bushing reinforcement of the composite material structure, and obvious beneficial effects are obtained compared with traditional methods. The method proposes a process parameter calculation method for the reinforcement process of the structure to solve the problem that existing devices and methods cannot be applied to the bushing reinforcement of the composite material structure. The radial compressive stress around the hole is obtained through the Lame formula and the elastic stress-strain relationship of the composite material, and then the total resistance of dynamic extrusion friction in the reinforcement process is obtained through the Coulomb friction theory, and the process parameters are determined in combination with the mathematical model of the electromagnetic force. The application can realize the calculation of the reinforcement process parameters of the composite material bushing with different structures and sizes, and is used for guiding the reinforcement of the dynamic cold extrusion composite material bushing structure.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of composite material reinforcement, and particularly relates to a composite material structure bushing reinforcement method based on electromagnetic loading. BACKGROUND

[0002] Traditional static cold extrusion methods often generate large resistance in the extrusion process, thereby causing a series of problems such as rod sticking, rod breaking, and hole wall damage. Dynamic cold extrusion can reduce the extrusion resistance generated in the traditional static cold extrusion process and further improve the fatigue life of the hole structure after extrusion. However, this method is only suitable for alloy materials with good plasticity and isotropy. For composite materials with poor plasticity and anisotropy, if the specific process parameters cannot be determined, damage will be caused to the composite material, thereby reducing or even offsetting the fatigue life gain effect brought by cold extrusion reinforcement. SUMMARY

[0003] In view of the technical problems in the background art, the application provides a composite material structure bushing reinforcement method based on electromagnetic loading, which solves the problem that the process parameters of dynamic cold extrusion applied in composite materials are difficult to determine.

[0004] The application is implemented by specifically adopting the following technical solutions:

[0005] The application provides a composite material structure bushing reinforcement method based on electromagnetic loading, which comprises the following steps:

[0006] The bushing is installed into the extruded hole of the composite material, so that the outer surface of the bushing is in contact with the extruded hole wall of the composite material, and the position of the extrusion mandrel is adjusted so that the front end positioning part of the extrusion mandrel is inserted into the inner hole of the bushing;

[0007] The radial compressive stress of the bushing after extrusion and the radial compressive stress of the extruded hole of the composite material are calculated;

[0008] According to the radial compressive stress and the structural characteristics and reinforcement characteristics of the composite material and the bushing in the extrusion reinforcement process, an extrusion friction resistance model based on the Coulomb friction principle is established between the extrusion mandrel and the bushing and between the bushing and the extruded hole of the composite material;

[0009] According to the extrusion friction resistance model, a total friction resistance model in the extrusion process is established;

[0010] According to the characteristics of electromagnetic loading, a mathematical model of electromagnetic force and process parameters is established, and constant parameters in the mathematical model are obtained through electromagnetic loading tests;

[0011] According to the total friction resistance model and the mathematical model, the reinforcement process parameters are determined;

[0012] According to the strengthening process parameters, the strengthening process is completed.

[0013] As a further illustration of the present application, the outer diameter of the bushing and the extruded hole diameter of the composite material are the same.

[0014] As a further illustration of the present application, the radial compressive stress of the bushing after extrusion is calculated according to the Lame formula; the radial compressive stress of the composite material around the extruded hole is calculated through the elastic stress-strain relationship of the composite material.

[0015] As a further illustration of the present application, the radial compressive stress of the bushing after extrusion is as follows:

[0016] ;

[0017] Wherein: σ r1 is the radial compressive stress of the bushing after extrusion, E B , E P are the elastic modulus of the extrusion mandrel and the bushing respectively, v B , v P are the Poisson's ratios of the extrusion mandrel and the bushing respectively, I1 is the relative extrusion amount between the extrusion mandrel and the bushing, obtained by , D is the diameter of the extrusion mandrel, and d is the inner diameter of the bushing.

[0018] As a further illustration of the present application, the radial compressive stress of the composite material around the extruded hole is as follows:

[0019] ;

[0020] Wherein: , , and , σ r2 is the radial compressive stress around the extruded hole, I2 is the relative extrusion amount between the hole of the composite material and the bushing, estimated by , wherein E max is the larger one of E1 and E2, v 12 , v 21 are the Poisson's ratios of the composite material in the longitudinal and transverse directions respectively, E1 and E2 are the elastic modulus of the composite material in the longitudinal and transverse directions respectively, G 12 is the shear modulus of the composite material, and θ is the included angle between the line connecting the point on the hole circumference and the hole center point and the horizontal line.

[0021] As a further illustration of the present application, the extrusion resistance F1 friction model between the extrusion mandrel and the bushing is as follows:

[0022] ;

[0023] Wherein, μ1 is the friction coefficient between the extrusion mandrel and the bushing, h is the height of the bushing.

[0024] As a further illustration of the present application, the extrusion resistance F2 friction model between the bushing and the extruded hole of the composite material is specifically:

[0025] 2 = π d 2 μ 2 I 2 s 2 β [ 2 α − 2 ν 1 2 + δ ( 1 + α ) ] ;

[0026] Wherein, μ2 is the friction coefficient between the hole wall of the composite material and the contact surface of the bushing, s is the thickness of the composite material 2, and d2 is the outer diameter of the bushing.

[0027] As a further illustration of the present application, the total friction resistance F model is specifically:

[0028] = π D μ 1 E B E P I 1 h E P ( 1 − ν B ) + E B ( 1 + ν P ) + π d 2 μ 2 I 2 s 2 β [ 2 α − 2 ν 1 2 + δ ( 1 + α ) ] .

[0029] As a further illustration of the present application, the electromagnetic force F e The model between the electromagnetic force and the process parameters is:

[0030]

[0031] Wherein, U is the discharge voltage, and K is a constant; through a plurality of electromagnetic loading tests, the value of K can be fitted.

[0032] As a further illustration of the present application, the process parameter discharge voltage is as follows:

[0033] = 1 K ( π D μ 1 E B E P I 1 h E P ( 1 − ν B ) + E B ( 1 + ν P ) + π d 2 μ 2 I 2 s 2 β [ 2 α − 2 ν 1 2 + δ ( 1 + α ) ] ) ;

[0034] According to the calculated discharge voltage, discharge is carried out, and the electromagnetic force generator drives the extrusion mandrel to complete the strengthening process.

[0035] Compared with the prior art, the present application has the following advantages:

[0036] The present application uses electromagnetic loading to carry out the bushing cold extrusion strengthening process of the composite material structure, compared with the traditional static method, the resistance in the cold extrusion process can be reduced, and the fatigue life of the composite material structure after extrusion can be improved. The method can determine the process parameters for dynamic cold extrusion strengthening of the composite material bushing through a small amount of electromagnetic loading test and simple manual calculation or Matlab, Python, Excel and the like, avoiding a large number of tests required to determine the process parameters. The method is suitable for dynamic cold extrusion strengthening of composite material bushings of any size. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 A schematic diagram of the composite material structure bushing strengthening method based on electromagnetic loading provided by the present application;

[0038] Figure 2 Process parameter determination flow chart of the composite structure bushing reinforcement process method based on electromagnetic loading provided by the present application;

[0039] Figure 3 Comparison chart of extrusion resistance generated by the method provided by the present application and traditional method;

[0040] Figure 4 Comparison chart of fatigue life of the composite material structure after being reinforced by the method provided by the present application and traditional method;

[0041] Figure 5 Comparison chart of total friction resistance obtained at different voltages and test values obtained by the present application.

[0042] In the figure, 1-electromagnetic force generator, 2-composite material, 3-extrusion mandrel, 4-bushing, 5-pad. DETAILED DESCRIPTION

[0043] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0044] Embodiment 1

[0045] The reinforcement method provided in this embodiment uses T800 carbon fiber, the layering order is [+45 / -45 / 0 / +45 / 90 / -45 / +45 / 90 / -45]s, the single layer thickness is 0.188 mm, the total thickness of the composite material is 3.384 mm, and the bushing of TA2 titanium alloy is tested; the composite material opening is 4 mm, the inner diameter of the bushing is 4 mm, and the outer diameter is 5 mm.

[0046] As shown in Figure 1 and 2 The present embodiment provides a composite material structure bushing reinforcement method based on electromagnetic loading, which comprises the following steps:

[0047] Step 1: Install the bushing 4 into the extruded hole of the composite material 2, so that the outer surface of the bushing 4 is in contact with the extruded hole wall of the composite material 2, and adjust the position of the extrusion mandrel 3 so that the front end positioning part of the extrusion mandrel 3 is inserted into the inner hole of the bushing 4.

[0048] The outer diameter of the general bushing 4 is the same as the extruded hole diameter of the composite material 2. During the reinforcement process, a backing plate 5 is generally required, and the opening diameter of the backing plate 5 is generally smaller than the extruded hole diameter of the composite material 2 and larger than the inner diameter of the bushing 4.

[0049] Step 2: Calculate the radial compressive stress of the bushing after extrusion and the radial compressive stress of the extruded hole of the composite material.

[0050] In some embodiments, the radial compressive stress of the bushing after extrusion is calculated according to the Lame formula; the radial compressive stress of the extruded hole of the composite material is calculated through the elastic stress-strain relationship of the composite material.

[0051] Specifically, the radial compressive stress of the bushing after extrusion is as follows:

[0052] ;

[0053] wherein: σ r1 is the radial compressive stress of the bushing after extrusion, E B , E P are the elastic moduli of the extrusion mandrel and the bushing, respectively, v B , v P are the Poisson's ratios of the extrusion mandrel and the bushing, respectively, I1 is the relative extrusion amount between the extrusion mandrel and the bushing, and is derived from , wherein D is the diameter of the extrusion mandrel, and d is the inner diameter of the bushing.

[0054] The radial compressive stress of the extruded hole of the composite material is as follows:

[0055] ;

[0056] wherein: , , and , σ r2 is the radial compressive stress of the extruded hole, I2 is the relative extrusion amount between the hole of the composite material and the bushing, and is estimated from , wherein E max is the larger one of E1 and E2, v 12 , v 21 are the Poisson's ratios of the longitudinal and transverse directions of the composite material, respectively, E1 and E2 are the elastic moduli of the longitudinal and transverse directions of the composite material, respectively, G 12 is the shear modulus of the composite material, and θ is the included angle between the line connecting the point on the hole circumference and the hole center point and the horizontal line.

[0057] Step 3: Based on the radial compressive stress obtained in Step 2 and the structural characteristics and reinforcement characteristics of the composite material and the bushing during the extrusion reinforcement process, an extrusion friction resistance model based on the Coulomb friction principle is established between the extrusion mandrel and the bushing and between the bushing and the extruded hole of the composite material.

[0058] Specifically, the extrusion resistance F1 between the extrusion mandrel and the bushing is modeled as follows:

[0059] ;

[0060] wherein μ1 is the friction coefficient between the extrusion mandrel and the bushing, and h is the height of the bushing.

[0061] The extrusion resistance F2 between the bushing and the composite material is modeled as follows:

[0062] 2 = π d 2 μ 2 I 2 s 2 β [ 2 α − 2 ν 1 2 + δ ( 1 + α ) ] ;

[0063] wherein μ2 is the friction coefficient between the bushing and the composite material, s is the thickness of the composite material, and d2 is the outer diameter of the bushing.

[0064] Step 4: According to the extrusion friction resistance model obtained in step 3, a total friction resistance model during the extrusion process is established.

[0065] Specifically, the total friction resistance F model is as follows:

[0066] = π D μ 1 E B E P I 1 h E P ( 1 − ν B ) + E B ( 1 + ν P ) + π d 2 μ 2 I 2 s 2 β [ 2 α − 2 ν 1 2 + δ ( 1 + α ) ] .

[0067] Step 5: According to the characteristics of the electromagnetic loading, a mathematical model between the electromagnetic force and the process parameters is established, and the constant parameters therein are obtained through electromagnetic loading tests.

[0068] Specifically, the model between the electromagnetic force F e and the process parameters is as follows:

[0069]

[0070] wherein U is the discharge voltage, and K is a constant; the value of K can be fitted through multiple sets of electromagnetic loading tests.

[0071] Step 6: According to the total friction resistance model and the mathematical model obtained in steps 4 and 5 respectively, the strengthening process parameters are determined.

[0072] Specifically, the determined process parameter discharge voltage is as follows:

[0073] = 1 K ( π D μ 1 E B E P I 1 h E P ( 1 − ν B ) + E B ( 1 + ν P ) + π d 2 μ 2 I 2 s 2 β [ 2 α − 2 ν 1 2 + δ ( 1 + α ) ] ) .

[0074] Step 7: According to the strengthening process parameters, the strengthening process is completed.

[0075] Specifically, the discharge voltage calculated according to step 6 is used for discharging, and the electromagnetic force generator 1 drives the extrusion mandrel 4 to complete the strengthening process. The control system of the present strengthening process can use the existing electromagnetic riveting control system to store energy and discharge the electromagnetic generator 1 to generate electromagnetic force.

[0076] With reference to Figure 3 The extrusion resistance generated by the method provided in the embodiment is about 1 / 4 of that of the traditional method, and the extrusion resistance is obviously reduced.

[0077] With reference to Figure 4 The fatigue life of the composite structure after the strengthening of the method provided in the embodiment is increased by about 50% compared with that of the traditional method, and the fatigue life is obviously improved, and the strengthening effect is improved.

[0078] With reference to Figure 5 The electromagnetic force change curve obtained by the process parameters calculated by the method provided in the embodiment is in good agreement with the test value, which proves the feasibility and accuracy of the method.

[0079] It should be noted that in this paper, terms such as "including", "containing" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or includes elements inherent to such process, method, article or equipment.

[0080] Although the embodiments of the present application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to the embodiments without departing from the principles and spirit of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A method of reinforcing a composite structure bushing based on electromagnetic loading, characterized in that, The application relates to a method for calculating the frictional resistance of an extrusion process. The method comprises the following steps: installing a bushing into a composite material extruded hole, so that the outer surface of the bushing is in contact with the wall of the composite material extruded hole, and adjusting the position of an extrusion mandrel so that the front end positioning part of the extrusion mandrel is inserted into the inner hole of the bushing; calculating the radial compressive stress of the bushing after extrusion and the radial compressive stress of the composite material extruded hole; according to the radial compressive stress and the structural features and strengthening features of the composite material and the bushing during the extrusion strengthening process, establishing an extrusion friction resistance model based on the Coulomb friction principle between the extrusion mandrel and the bushing and between the bushing and the composite material extruded hole; According to the characteristics of the electromagnetic loading, a mathematical model between the electromagnetic force and the process parameters is established, and constant parameters in the model are obtained through electromagnetic loading tests; wherein the mathematical model between the electromagnetic force F e and the process parameters is: ； according to the extrusion friction resistance model, establishing a total friction resistance model during the extrusion process; wherein U is a discharge voltage, and K is a constant; the value of K can be fitted through a plurality of electromagnetic loading tests; ； wherein: , , ; D is the diameter of the extrusion mandrel, μ1 is the friction coefficient between the extrusion mandrel and the bushing, h is the height of the bushing; μ2 is the friction coefficient between the hole wall of the composite material and the contact surface of the bushing, E B , E P are the elastic moduli of the extrusion mandrel and the bushing, respectively, I1 is the relative extrusion amount between the extrusion mandrel and the bushing, and is derived from , d is the inner diameter of the bushing, v B , v P are the Poisson's ratios of the extrusion mandrel and the bushing, respectively, d2 is the outer diameter of the bushing, I2 is the relative extrusion amount between the hole of the composite material and the bushing, and is estimated from , wherein E max is the larger one of E1 and E2, E1 and E2 are the longitudinal and transverse elastic moduli of the composite material, respectively, G 12 is the shear modulus of the composite material, s is the thickness of the composite material, v 12 , v 21 are the longitudinal and transverse Poisson's ratios of the composite material, respectively. the discharge voltage is as follows: discharging according to the calculated discharge voltage, and the electromagnetic force generator drives the extrusion mandrel to complete the strengthening process; according to the total friction resistance model and the mathematical model, determining the strengthening process parameters; 2. The method of strengthening according to claim 1, wherein, according to the strengthening process parameters, completing the strengthening process.

3. The method of strengthening of claim 1, wherein, The outer diameter of the bushing is the same as the diameter of the composite material extruded hole.

4. The method of strengthening according to claim 3, wherein, The radial compressive stress of the bushing after extrusion is calculated according to the Lam formula, and the radial compressive stress of the composite material extruded hole is calculated through the elastic stress-strain relationship of the composite material. ； where: σ r1 is the radial compressive stress after the bushing is extruded.

5. The method of strengthening according to claim 4, wherein, The radial compressive stress of the bushing after extrusion is as follows: ； where: σ r2 is the radial stress at the hole circumference, and θ is the angle between the line connecting the point on the hole circumference and the hole center and the horizontal line.

6. The method of strengthening according to claim 5, wherein, The radial compressive stress of the composite material extruded hole is as follows: 。 7. The method of strengthening according to claim 6, wherein, The extrusion resistance F1 friction model between the extrusion mandrel and the bushing is as follows: 。 8. The method of strengthening according to claim 7, wherein, The extrusion resistance F2 friction model between the bushing and the composite material extruded hole is as follows: The total friction resistance F model is as follows: 。

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