Fan blade foam core material shear key design method

Abstract

The invention discloses a fan blade foam core material shear key design method, which comprises the following steps of: firstly, establishing a finite element simulation model to facilitate simulation of a subsequent shear strength test, performing shallow slot design between deep slots on the basis of the existing deep slot design, and designing a shear key between the deep slots on the basis of the existing deep slot design. The size, the shape and the set angle of the shallow slot can be set at will, and the design of the shallow slot transverse shear key can enhance the shear strength according to simulation data; by designing the positions of the through holes, the positions of part of the through holes coincide with the deep grooves, so that the vertical shear key is designed, the size, the shape and the inclination angle of the through holes can be set at will, and it can be obtained through simulation data that the mode that part of the through holes coincide with the deep grooves is designed, and the shear strength can be enhanced; the method can effectively improve the shear strength of the foam core material, and is suitable for structural design of the foam core material in the fan blade.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of fan blade structure design, and particularly relates to a fan blade foam core shear key design method. BACKGROUND

[0002] The fan blade used in wind power generation is a sandwich structure, and the fan blade is composed of two layers of fiber reinforced plates and a light and porous foam core material between the two layers. The surface of the foam core material is slotted and perforated to provide resin flow and strengthen the core material structure. The existing foam core material is mostly designed with deep grooves and through holes, but lacks shear key design, resulting in insufficient shear strength of the existing foam core material. Therefore, in order to solve the problem, the present application provides a fan blade foam core shear key design method. SUMMARY

[0003] The present application aims to provide a fan blade foam core shear key design method to solve the problem of insufficient shear strength of the existing foam core material.

[0004] To achieve the above-mentioned purpose, the present application provides the following technical scheme:

[0005] A fan blade foam core shear key design method, comprising the following steps: S1, establishing a finite element simulation model: the established finite element model includes three parts of foam, pouring resin and steel clamp, the core material is connected with the upper clamp through a bilinear damage cohesive element to simulate the core material damage in the shearing process;

[0006] S2, transverse shear strengthening: based on the existing deep groove design, shallow grooves are added between the deep grooves, and after pouring resin into the shallow grooves, the shallow grooves form a transverse shear key between the panel and the core material;

[0007] S3, vertical shear strengthening: change the traditional punching position to coincide the through hole with part of the deep groove, and after pouring resin, the exposed part of the through hole forms a vertical shear key.

[0008] Further, the size and shape of the shallow groove in step S2 can be arbitrarily set.

[0009] Further, the size and shape of the through hole in step S3 can be arbitrarily set.

[0010] Further, the shallow groove in step S2 can be set at any angle.

[0011] Further, the through hole in step S3 can be set at any angle.

[0012] The principle and beneficial effects of the technical solution are as follows: the method sets shallow grooves between the traditional through-hole deep grooves, and verifies through a finite element simulation model that the designed shallow grooves can effectively increase the transverse shear strength and improve the maximum shear bearing capacity; and the original deep grooves are combined with part of the through holes, and verification through a finite element simulation model shows that the combination of the designed part of the through holes and the deep grooves can effectively increase the vertical shear strength and improve the maximum shear bearing capacity. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 A structure diagram of a foamed core material slotting and punching in the prior art;

[0014] Figure 2 A finite element simulation model established for the embodiment of the application;

[0015] Figure 3 A structure diagram when a shallow groove transverse shear key is designed;

[0016] Figure 4 An original structure diagram before the shallow groove is designed;

[0017] Figure 5 A structure diagram after the shallow groove is designed;

[0018] Figure 6 A support reaction force-displacement curve before the shallow groove is designed;

[0019] Figure 7 A support reaction force-displacement curve after the shallow groove is designed;

[0020] Figure 8 A structure diagram when a through-hole vertical shear key is designed;

[0021] Figure 9 An original structure diagram before the through hole is designed;

[0022] Figure 10 A structure diagram after the through hole is designed;

[0023] Figure 11 A support reaction force-displacement curve before the through hole is designed;

[0024] Figure 12 A support reaction force-displacement curve after the through hole is designed. DETAILED DESCRIPTION

[0025] The application will be further described in detail below in combination with the drawings and embodiments:

[0026] As Figure 1As shown, this is the slot design of the foam core material for wind turbine blades in the prior art. The foam core material in the prior art generally only has deep slots and through holes. Compared with natural balsa wood core material, the shear strength of the existing foam core material needs to be improved.

[0027] To improve the shear strength of the foam core material, the following process can be used:

[0028] Step 1: Establish a finite element simulation model

[0029] First, the structure of the anti-shear key is designed using the finite element simulation method. The finite element model includes three parts: foam, resin injection, and steel clamp. The core material is connected to the upper clamp through bilinear damage cohesive elements to simulate the failure of the core material during the shear test.

[0030] The shear test model, based on ISO 1922 "Rigid foamed plastics – Determination of shear properties", is used to measure the mechanical properties of materials in a shear direction parallel to their surface, including shear strength and shear modulus. For example... Figure 2 The diagram shows the established finite element simulation model. In the figure, blue represents resin, red represents foam, gray represents steel clamps, and green represents cohesive elements. The standard test size in the figure is 250mm × 50mm × 25mm. During the test, the specimen is clamped in a dedicated shear loading fixture, and a load is applied to the specimen plane by relative sliding. The loading rate is controlled at 1mm / min to obtain a stable stress-strain curve, thereby enabling the evaluation of the sandwich structure's ability to resist in-plane shear deformation.

[0031] Step 2: Transverse shear strengthening

[0032] Existing grooving designs only create deep, vertically penetrating grooves within the foam. This invention, however, adds shallow surface grooves to the deep groove design, creating shallow grooves between the deep grooves. The size and shape of these shallow grooves can be arbitrarily set, and they can be positioned at any angle on the core material surface. After resin infusion, these shallow grooves form transverse shear bonds between the panel and the core material. Figure 3 The diagram shown is a schematic of a shallow trench design.

[0033] Taking a model with a groove width of 1mm and a groove spacing of 20mm as an example, the original model only contains deep grooves, such as... Figure 4 As shown. In Figure 4 Based on this, shallow grooves are added between the deep grooves. The depth of the shallow grooves is 3mm, and the spacing between the shallow grooves is also 20mm, as detailed below. Figure 5 As shown.

[0034] After establishing the geometric model, cohesive elements were inserted between the resin and the core material, and corresponding material parameters were assigned to each part. Meshing was then performed, and the model was assembled with a steel clamp. Shear deformation simulation calculations were then conducted. After the calculations were completed, the support reaction-displacement curves were extracted from the control points. The results are as follows: Figure 6 , Figure 7 As shown, Figure 6 The support reaction-displacement curve is for a support without shallow groove transverse shear keys, and its maximum shear capacity is 23.15 kN. Figure 7 The support reaction-displacement curve of the shallow groove transverse shear key was designed, and its maximum shear bearing capacity is 24.92KN. The addition of the transverse shear key increased the maximum shear bearing capacity by 7.6%. The addition of the shallow groove design can effectively increase the maximum shear bearing capacity.

[0035] Step 3: Vertical Shear Strengthening

[0036] Traditional drilling designs only focus on the diameter and spacing of the holes, generally without specific requirements on the hole position. This invention, by changing the drilling position, allows for partial fusion of the through-hole and the deep groove. The size and shape of the through-hole can be arbitrarily set, and drilling can be performed at any angle. After resin infusion, the exposed portion of the through-hole forms a vertical shear key, thus strengthening the deep groove against shear. Figure 8 The diagram shown is a schematic of the through-hole design.

[0037] Taking a model with a groove width of 1mm and a groove spacing of 15mm as an example, the original model only contains the deep groove, such as... Figure 9 As shown, in Figure 9 Based on this, a through hole with a diameter of 2mm is added. The through hole is pressed against the edge of the deep groove, exposing a semicircle with a radius of 1mm, as shown in the following figure. Figure 10 As shown.

[0038] After establishing the geometric model, cohesive elements were inserted between the resin and the core material, and corresponding material parameters were assigned to each part. Meshing was then performed, and the model was assembled with a steel clamp. Shear deformation simulation calculations were then conducted. After the calculations were completed, the support reaction-displacement curves were extracted from the control points. The results are as follows: Figure 11 , Figure 12 As shown, Figure 11 The support reaction-displacement curve is for a support without vertical shear keys, and its maximum shear capacity is 18.40 kN. Figure 12 The maximum shear capacity is 19.05 kN, achieved by adding a vertical shear key. The addition of the vertical shear key increases the maximum shear capacity by 3.5%. The design of the through hole coinciding with the deep groove can effectively increase the maximum shear capacity.

[0039] The above descriptions are merely embodiments of the present invention, and common technical solutions or characteristics known in the schemes are not described in detail here. For those skilled in the art, various modifications and improvements can be made without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application shall be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A method for designing shear keys in the foam core material of wind turbine blades, characterized in that, Includes the following steps: S1. Establishing a finite element simulation model: The established finite element model includes three parts: foam, injection resin, and steel clamp. The core material is connected to the upper clamp through bilinear damage cohesive elements to simulate the failure of the core material during the shearing process. S2, Transverse Shear Strengthening: Based on the existing deep groove design, a surface shallow groove is added. The surface shallow groove is set between the deep grooves. After resin is poured into the shallow groove, the shallow groove forms a transverse shear bond between the panel and the core material. S3, Vertical shear reinforcement: The traditional drilling position is changed, and the through hole is overlapped with part of the deep groove. After resin is injected, the exposed part of the through hole forms a vertical shear bond.

2. The method for designing shear keys in the foam core material of wind turbine blades according to claim 1, characterized in that: The size and shape of the shallow trench in step S2 can be set arbitrarily.

3. The method for designing shear keys in the foam core material of wind turbine blades according to claim 1, characterized in that: The size and shape of the through hole in step S3 can be set arbitrarily.

4. The method for designing shear keys in the foam core material of wind turbine blades according to claim 1, characterized in that: In step S2, the shallow groove can be set at any angle.

5. The method for designing shear keys in the foam core material of wind turbine blades according to claim 1, characterized in that: In step S3, the through hole can be set at any angle.

Images