Design method of blade connection interface and hybrid structure fan blade

Abstract

The application discloses a design method of a blade connecting interface and a hybrid structure fan blade. The design method of the blade connecting interface comprises the following steps: S1, assuming a curve of the connecting interface and obtaining a curve function of the curve, and decomposing external force on the connecting interface into a tangent force function and a normal force function; S2, obtaining an interface shear strength function by using the normal force function; S3, making the tangent force function less than the interface shear strength function, and obtaining a relationship between the external force on the connecting interface and the curve function; S4, obtaining a relationship between an external force load and the curve function; S5, obtaining a specific form of the curve function according to the determined external force load, if the curve form cannot be realized due to various reasons, returning to S1 to start iteration, and if the curve form can be realized, executing step S6; S6, processing a metal leading edge panel and a composite material according to a corresponding form of the connecting interface; and S7, splicing. The force borne by the interface is converted into a tangent force and an interface pressure, and finally the shear deformation or stress of the interface is reduced.

Description

Technical Field

[0001] This invention relates to a design method for blade connection interfaces and a hybrid structure fan blade. Background Technology

[0002] The hybrid fan blade consists of two parts: a titanium alloy (leading edge and titanium core) and a composite material (outer blade and trailing edge). The titanium alloy leading edge and the composite material of the blade body are bonded together using resin during co-curing, while the titanium core and the blade body composite are connected by a stitching process. Under rotational centrifugal loads, due to the difference in stress and deformation between the titanium alloy leading edge and the blade body composite, as well as seam deformation, cracks can easily form between the leading edge and the composite. These cracks can affect not only the static strength and fatigue performance of the blade itself but also its aerodynamic performance. Due to process limitations, stitching or mechanical connections with high strength and stiffness cannot be used to connect the metal leading edge and the composite blade. Only co-curing or adhesive bonding methods can be used. However, the interface strength and stiffness formed by these two connection processes are insufficient to meet the requirements of typical operating conditions and loads on the blade. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the problem of low strength of the interface between the metal leading edge and the composite blade in the prior art, and to provide a design method for the blade connection interface and a hybrid structure fan blade.

[0004] The present invention solves the above-mentioned technical problems through the following technical solution:

[0005] A method for designing a blade connection interface, the method comprising:

[0006] S1. Assume a curve of a connection interface and obtain the curve function of the curve. Decompose the external force on the connection interface into tangential force function and normal force function.

[0007] S2. Substitute the normal force function into the relationship between the interface shear strength and the normal force to obtain the interface shear strength function;

[0008] S3. Make the tangential force function less than the interface shear strength function to obtain the relationship between the external force and the curve function on the connection interface;

[0009] S4. Based on the relationship between the external force load and the external force on the connection interface, obtain the relationship between the external force load and the curve function;

[0010] S5. Based on the determined external force load, obtain the specific form of the curve function. If the curve form cannot be realized, return to step S1. If the curve form can be realized, proceed to step S6.

[0011] S6: Process the metal leading edge panel and composite material according to the corresponding form of the connection interface;

[0012] S7: Spliced ​​metal front edge panel and composite material.

[0013] In this technical solution, the external force in the direction of shear force on the interface is transformed into interfacial pressure and shear force, establishing a relationship between interfacial shear strength and interfacial tangential force, ensuring that the interfacial tangential force is less than the interfacial shear strength. This transforms the force borne by the interface into tangential force and interfacial pressure. Based on this, the interface curve can be redesigned, changing the stress state and direction of the interface, ultimately reducing the shear deformation or stress on the interface.

[0014] Preferably, the specific form of the assumed curve function of the connected interface includes one or more of the following: parabola, spline curve, hyperbola, and Archimedean involute.

[0015] In this technical solution, the interface curve includes one or more of the following: parabola, spline curve, brachistochrone, hyperbola, and Archimedes' involute. This allows the preferred curve to better increase the interface strength and prevent separation between interfaces.

[0016] A hybrid structure fan blade, wherein the hybrid structure fan blade is designed by the design method of the blade connection interface.

[0017] In this technical solution, the hybrid structure fan blade is derived from the design method of the blade connection interface. By changing the stress state and direction of the interface, the external force of the hybrid structure fan blade is adjusted into interface pressure and shear force, which ultimately reduces the shear deformation or stress of the interface.

[0018] A hybrid structure fan blade, the hybrid structure fan blade comprising:

[0019] Metal leading edge panel and composite materials;

[0020] The protrusions or grooves on the side of the metal leading edge panel mate with the grooves or protrusions on the side of the composite material.

[0021] The extended curve of the groove or protrusion is one or more of the following: parabola, spline curve, brachistochrone curve, hyperbola, and Archimedes curve.

[0022] In this technical solution, the protrusions or grooves on the side cooperate with the grooves or protrusions on the composite material, so that the metal front edge panel and the composite material are connected together. The extension curve of the groove or protrusion is one or more of the following: parabola, spline curve, steepest curve, hyperbola, Archimedes curve, which transforms the external force in the shear direction of the interface into interface pressure and shear force, thereby improving the interface shear strength and reducing the interface shear stress.

[0023] Preferably, the connection between the metal leading edge panel and the composite material includes adhesive bonding and / or co-curing.

[0024] In this technical solution, an adhesive is used to generate a combined force at the interface between the metal leading edge panel and the composite material, thereby connecting the metal leading edge panel and the composite material. The adhesive bonding process is simple and does not require complex equipment. Co-curing simultaneously completes the curing and molding of the metal leading edge panel and the composite material, as well as the overall part of the adhesive layer, within a single curing cycle, achieving one-time molding and ensuring molding quality.

[0025] Preferably, the corners of the extended curve are rounded.

[0026] In this technical solution, rounded corners are provided at the corners of the extended curve to avoid stress concentration at the connection interface between the metal leading edge panel and the composite material. This prevents excessive force at the corners from causing the composite material to detach from the metal leading edge panel.

[0027] Preferably, the hybrid structure blade includes a blade tip, and the groove or the protrusion is located at the end away from the blade tip.

[0028] In this technical solution, the groove and protrusion are located at the end of the hybrid structure blade away from the blade tip, which makes the joint more compact in the part with greater stress and improves the service life of the hybrid structure fan blade.

[0029] Preferably, the metal leading edge panel and the composite material are composed of metal, carbon fiber preform and adhesive layer.

[0030] In this technical solution, the metal leading edge panel and composite material are composed of metal, carbon fiber preform and adhesive layer, which can effectively reduce the weight of the blade and increase the structural strength of the blade.

[0031] Preferably, the interface between the metal leading edge panel and the composite material is a curved surface.

[0032] In this technical solution, the connection interface between the metal leading edge panel and the composite material is curved, which can make the two fit more tightly and avoid stress concentration on the composite material.

[0033] The positive and progressive effects of this invention are as follows:

[0034] The external force in the direction of shear force on the interface is transformed into interfacial pressure and shear force, establishing a relationship between interfacial shear strength and interfacial tangential force, ensuring that the interfacial tangential force is less than the interfacial shear strength. This transforms the force on the interface into tangential force and interfacial pressure. Based on this, the interface curve can be redesigned to change the stress state and direction of the interface, ultimately reducing the shear deformation or stress on the interface. Attached Figure Description

[0035] Figure 1 This is a flowchart illustrating a design method for the blade connection interface according to an embodiment of the present invention.

[0036] Figure 2 This is a schematic diagram of the structure of a hybrid fan blade according to an embodiment of the present invention.

[0037] Figure 3 This is a schematic diagram of the forces acting on a hybrid structure fan blade according to an embodiment of the present invention.

[0038] Figure 4 This is a schematic diagram of the destruction of a hybrid structure fan blade according to an embodiment of the present invention.

[0039] Figure 5 This is a schematic diagram of the unmodified hybrid structure fan blades according to an embodiment of the present invention.

[0040] Figure 6 This is a schematic diagram of an improved hybrid structure fan blade according to an embodiment of the present invention.

[0041] Figure 7 This is a schematic diagram showing the relationship between the connection interface of the hybrid structure fan blade and the tangential and normal forces according to an embodiment of the present invention.

[0042] Figure 8 This is a schematic diagram of the overall force distribution on a hybrid structure fan blade according to an embodiment of the present invention.

[0043] Figure 9 This is a schematic diagram of the force analysis of a hybrid structure fan blade according to an embodiment of the present invention.

[0044] Figure 10 This is a schematic diagram of the interface curve of a hybrid structure fan blade according to an embodiment of the present invention.

[0045] Figure 11 This is a schematic diagram (a) of the connection interface of a hybrid structure fan blade according to an embodiment of the present invention.

[0046] Figure 12 This is a schematic diagram (II) of the connection interface of a hybrid structure fan blade according to an embodiment of the present invention.

[0047] Figure 13 This is a schematic diagram (III) of the connection interface of a hybrid structure fan blade according to an embodiment of the present invention.

[0048] Explanation of reference numerals in the attached figures

[0049] Connection Interface 1

[0050] Metal front edge panel 2

[0051] Leaf tip 3

[0052] Leaf surface 4

[0053] Tail edge 5

[0054] Tenon 6

[0055] Rounded corners 7

[0056] Crack 8 Detailed Implementation

[0057] The present invention will be further illustrated by way of embodiments below, but the present invention is not limited to the scope of the embodiments described herein.

[0058] like Figure 1 and Figure 2 As shown, the present invention discloses a design method for a blade connection interface 1, wherein the hybrid structure fan blade comprises a composite material of a metal leading edge panel 2 and a blade body.

[0059] The design method for blade connection interface 1 includes:

[0060] S1. Assume a curve of connection interface 1 and obtain the curve function of the curve. Decompose the external force on connection interface 1 into tangential force function and normal force function.

[0061] S2. Substitute the normal force function into the relationship between the interface shear strength and the normal force to obtain the interface shear strength function;

[0062] S3. Make the tangential force function less than the interface shear strength function to obtain the relationship between the external force and the curve function on the connection interface 1.

[0063] S4. Based on the relationship between the external force load and the external force on the connection interface 1, obtain the relationship between the external force load and the curve function;

[0064] S5. Based on the determined external force load, obtain the specific form of the curve function. If the curve form cannot be realized, return to step S1. If the curve form can be realized, proceed to step S6.

[0065] S6: Process the metal leading edge panel 2 and the composite material according to the corresponding form of the connection interface 1;

[0066] S7: Splicing metal leading edge panel 2 and composite material.

[0067] like Figure 2 As shown, the metal leading edge panel 2 and the composite material form a connection interface 1. S1, assuming a curve for the connection interface 1, the curve function h(x) of this curve is obtained. The curve function h(x) includes one or more of the following: parabola, spline curve, brachistochrone, and Archimedean involute. These preferred curves can better increase the interface strength and prevent delamination between the connection interfaces 1.

[0068] like Figure 8 and Figure 9 As shown in Figure 9 , the external force F on the connection interface 1 is decomposed into a tangential force function and a normal force function. As Figure 9 and Figure 10 shown, the interface normal pressure c and the tangential force t at any point at the connection interface 1 can be expressed as functions of the external force f and the curve h at that point. As shown in the following formulas, by substituting the tangential force function and the normal force function obtained in step S1.

[0069]

[0070] In engineering practice, the relationship between the interface shear strength and the normal force is already known. The general interface strength can be regarded as the interface shear strength function g(c) of the normal force perpendicular to the connection interface 1. Therefore, in S2, substitute the normal force function into the relationship between the interface shear strength and the normal force to obtain the interface shear strength function.

[0071] In S3, make the tangential force function less than the interface shear strength function to obtain the relationship between the external force on the connection interface 1 and the curve function. That is, make t < g(c), as Figure 3 and Figure 4 shown, when the tangential force t is less than g(c), the connection interface 1 will not be damaged. After the connection interface 1 is damaged, cracks 8 will occur. As Figure 7 shown, that is, when it is below the curve g(c) of Figure 7 , the connection interface 1 is intact and does not fail. Generally, the tensile force is taken as positive and the pressure as negative. As the normal force on the connection interface 1 changes from tensile force to pressure, that is, the horizontal axis changes from positive to negative, the interface shear strength will gradually increase. Therefore, in order to improve the shear strength of the connection interface 1, it is appropriate for the normal force on the connection interface 1 to bear pressure. Therefore, mainly considering the compression situation of the connection interface 1, the design method of the blade connection interface 1 is only applicable to Figure 7 the second quadrant (the negative half of the horizontal axis).

[0072] From Figure 5 and Figure 6 shown, by changing the form of the connection interface 1 and converting the force borne by the connection interface 1 into the tangential force t and the interface pressure c, not only can the tangential force be reduced, but also the interface shear strength can be improved.

[0073] Substitute the tangential force function and the normal force function into the discriminant to obtain the following expression:

[0074]

[0075] As Figure 10 shown, t < g(c) is the best state for the connection interface 1 not to be damaged. Making t = g(c) can obtain the relationship between the external force and the curve function.

[0076] S4. Based on the relationship between the external force load and the external force on the connection interface 1, obtain the relationship between the external force load and the curve function. The connection interface 1 can be designed in detail according to the interface shear strength function g(c) and other limiting conditions, such as the interface size, external force load F, etc. That is, the cross-section curve function h(x) and dimensions, etc., can make the interface force f integrated along the interface curve to be equal to the external force received, that is, the external force load F = ∫ h fdx.

[0077] S5. According to the determined external force load, obtain the specific form of the curve function and the specific form of the connection curve function. After the external force load F is determined, according to the relationship between the external force and the curve function obtained in step S3, substitute it into S4 for integration, and the specific form of the curve function can be obtained. The specific form of the curve function h(x) includes the specific coefficients of the curve. If this curve form (such as length, shape, etc.) cannot be realized due to various reasons (such as processing technology limitations, boundary size limitations), then return to S1 to start a new round of iteration. If this curve form can be realized, then execute step S6. Such as Figure 11 As Figure 12 and Figure 13 shown, avoid the separation between the connection interfaces 1. [[ID=***]]

[0078] Among them, the specific embodiments of steps S1 - S5 can be:

[0079] If the assumed curve form in step S1 is a parabola, let the curve function h = ax 2 (a < 0, x < 0), and the vertex of the curve passes through the origin of coordinates. Then h' = 2ax, and the interface normal pressure c and tangential force t at any point on the connection interface 1 can be expressed as functions of the external force f at this point and the curve h. As shown in the following formulas, by substituting the tangential force function and the normal force function obtained in step S1.

[0080]

[0081] Step S2. Substitute the normal force function into the relationship between the interface shear strength and the normal force to obtain the interface shear strength function g(c).

[0082] Let g = -kc + b (k > 0, b > 0), and assume k = 1, b = 2. Substitute t < g(c) in step S3, and assume that the centrifugal force is uniformly distributed in the latitudinal direction and f = 1, then we can get:

[0083]

[0084] Let the latitudinal span of the curve be x ∈ (-1, 0), and the solution is: Take the minimum value

[0085]

[0086] Then h = -0.36x 2 , (x ∈ (-1, 0))

[0087] Conversely, at this time the latitudinal span distance of the curve is 1. Then, according to the relationship between the determined external force load F and the external force on the connection interface 1 in step S4, the relationship between the external force load F and the curve function is obtained.

[0088] Step S5, according to the determined external force load, obtain the specific form of the curve and connect the specific form of the curve function. The resultant force Check whether F meets the actual conditions. If not, return to step S1, increase the latitudinal span range of the curve and solve the corresponding curve parameters so that the resultant force F meets the requirements. If the curve form can be realized, execute step S6. [[ID=..]]

[0089] If the assumed curve function in step S1 is a quadratic spline curve, let the curve function h = !

[0090] ax 2 + bx + c, and it passes through the points (0, 0), (-1, m). Substituting can solve for c = 0, a - b = m, then h = ax 2 + (a - m)x, h' = 2ax + (a - m). And the interface normal pressure c and tangential force t at any point on the connection interface 1 can both be expressed as functions of the external force f at this point and the curve h = ax 2 + (a - m)x. As shown in the following formulas, substitute the tangential force function and normal force function obtained in step S1.

[0091]

[0092] Step S2, substitute the normal force function into the relationship between the interface shear strength and the normal force to obtain the interface shear strength function g(c). Also assume g(c) = -c + 2, substituting t < g(c) in step S3 gives:

[0093]

[0094] a(2x + 1) < 1 + m

[0095] a < 0, let the latitudinal span of the curve be x ∈ (-1, 0). When x ∈ (-0.5, 0), m > -1 is sufficient.

[0096] When x ∈ (-1, -0.5), take m = -0.4, Take a = -0.5, then b = a - m = -0.1.

[0097] Then h = -0.5x 2 - 0.1x, (x ∈ (-1, 0))

[0098] Step S4: Obtain the relationship between the external force load F and the curve function according to the relationship between the determined external force load F and the external force on the connection interface 1.

[0099] Step S5: Obtain the specific form of the curve according to the determined external force load F, and connect the specific form of the curve function. The resultant force Check whether F meets the actual conditions. If not, return to Step S1, increase the latitudinal span range of the curve and solve the corresponding curve parameters so that the resultant force F meets the requirements. If the curve form can be realized, execute Step S6.

[0100] If the assumed curve function in Step S1 is a hyperbola, let Let the latitudinal span of the curve be x ∈ (1, 2), and h(2) = 0. Substituting it in, we can get q = p / 2.

[0101]

[0102] And the interface normal pressure c and the tangential force t at any point on the connection interface 1 can both be expressed as functions of the external force f at this point and the curve function.

[0103] As shown in the following formula, substitute the tangential force function and the normal force function obtained in Step S1.

[0104]

[0105] Step S2: Substitute the normal force function into the relationship between the interface shear strength and the normal force to obtain the interface shear strength function g(c).

[0106] Let g(c) = -2c + 2, and substitute it into t < g(c) in Step S3 to get:

[0107]

[0108] Expand and organize to get:

[0109]

[0110] Since Therefore, it needs to satisfy Since x ∈ (1, 2), take the maximum value x = 2, then p > 16 / 3. We can take p = 6, then

[0111] Then

[0112] At this time, the latitudinal span distance of the curve is 1. Then, according to the relationship between the determined external force load F and the external force on the connection interface 1 in Step S4, obtain the relationship between the external force load F and the curve function.

[0113] Step S5: Based on the determined external force F, obtain the specific form of the curve and connect the specific form of the curve function. Resultant force Check if F meets the actual conditions. If not, return to step S1, increase the latitudinal span range of the curve and solve for the corresponding curve parameters to make the resultant force F meet the requirements. If the curve form can be realized, proceed to step S6.

[0114] S6. Process the metal leading edge panel 2 and the composite material according to the corresponding form of the connection interface 1. Process the metal leading edge panel 2 and the composite material according to the corresponding form of the connection interface 1, such as one or more of the following: parabola, spline curve, brachistochrone, and Archimedes involute, and process them according to the specific parameters of these curves calculated.

[0115] S7, spliced ​​metal front edge panel 2 and composite material.

[0116] This blade-connection interface design method transforms the external force in the shear direction of the interface into interfacial pressure and shear force, establishing a connection between interfacial shear strength and interfacial tangential force, ensuring that the interfacial tangential force is less than the interfacial shear strength. This converts the force borne by the interface into tangential force and interfacial pressure. Based on this, the interface curve can be redesigned to change the stress state and direction of the interface, ultimately reducing the shear deformation or stress on the interface.

[0117] The present invention also discloses a hybrid structure fan blade, which is designed by the design method of the blade connection interface 1. By changing the stress state and direction of the interface, the shear stress of the hybrid structure fan blade is adjusted to interface pressure and shear force, thereby reducing the shear deformation or stress of the interface.

[0118] like Figure 2 As shown, this invention also discloses a hybrid structure fan blade, which includes a metal leading edge panel 2 and a composite material. The hybrid structure fan blade includes five regions: a blade tip 3, a blade surface 4, a trailing edge 5, and a tenon 6. The protrusions or grooves on the side of the metal leading edge panel 2 cooperate with the grooves or protrusions on the side of the composite material. Figure 11 ,like Figure 12 and Figure 13 As shown, the extension curve of such protrusions or grooves is one or more of the following: parabola, spline curve, maximum speed curve, hyperbola, and Archimedean curve. The protrusions or grooves on the side of the hybrid structure fan blades cooperate with the grooves or protrusions on the composite material, so that the metal leading edge panel 2 and the composite material are connected together. The extension curve of the grooves or protrusions is one or more of the following: parabola, spline curve, maximum speed curve, hyperbola, and Archimedean curve. For example... Figure 5 and Figure 6As shown, the external force in the shear direction on the interface is converted into interfacial pressure and shear force, thereby increasing the interfacial shear strength and reducing the interfacial shear stress.

[0119] The connection between the metal leading edge panel 2 and the composite material can be achieved through adhesive bonding or co-curing. Adhesive bonding generates a combined force at the interface 1 between the metal leading edge panel 2 and the composite material, thereby connecting them. Adhesive bonding is simple and does not require complex equipment. Co-curing simultaneously cures the metal leading edge panel 2 and the composite material, creating a single integral part within a single curing cycle, achieving one-time molding and ensuring molding quality. In other embodiments, both adhesive bonding and co-curing processes can be used simultaneously to enhance the adhesion effect.

[0120] like Figure 2 and Figure 6 As shown, the corners of the extended curve are provided with fillets 7. The fillets 7 at the corners of the extended curve are provided to avoid stress concentration at the connection interface 1 between the metal leading edge panel 2 and the composite material, and to prevent the composite material from detaching from the metal leading edge panel 2 due to excessive force at the corner.

[0121] like Figure 2 As shown, the hybrid structure fan blade includes a blade tip 3, and a groove or protrusion is provided at the end of the hybrid structure fan blade away from the blade tip 3. This design makes the joint more compact in the parts subjected to greater stress, thereby improving the service life of the hybrid structure fan blade.

[0122] like Figure 2 As shown, the metal leading edge panel 2 and the composite material consist of metal, carbon fiber preform, and adhesive layer. This design can effectively reduce the weight of the blade while increasing its structural strength.

[0123] like Figure 2 As shown, the connection interface 1 between the metal leading edge panel 2 and the composite material is a curved surface, which can make the two fit more tightly and avoid stress concentration on the composite material.

[0124] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of the present invention is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, but all such changes and modifications fall within the scope of protection of the present invention.

Claims

1. A design method for a blade connection interface, characterized in that, The design method for the blade connection interface includes: S1. Assume a curve of a connection interface and obtain the curve function of the curve. Decompose the external force on the connection interface into tangential force function and normal force function. S2. Substitute the normal force function into the relationship between the interface shear strength and the normal force to obtain the interface shear strength function; S3. Make the tangential force function less than the interface shear strength function to obtain the relationship between the external force and the curve function on the connection interface; S4. Based on the relationship between the external force load and the external force on the connection interface, obtain the relationship between the external force load and the curve function; S5. Based on the determined external load, obtain the specific form of the curve function. If the external force on the curve function is inconsistent with the determined external load, return to step S1. If the external force on the curve function is consistent with the determined external load, proceed to step S6. S6: Process the metal leading edge panel and composite material according to the corresponding form of the connection interface; S7: Spliced ​​metal front edge panel and composite material.

2. The design method for the blade connection interface as described in claim 1, characterized in that, The assumed curve function of the connected interface may take the form of one or more of the following: parabola, spline curve, hyperbola, and Archimedean involute.

3. A hybrid structure fan blade, characterized in that, The hybrid structure fan blades are designed using the blade connection interface design method described in any one of claims 1-2.

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