CN112666020B - Stress concentration verification test method for chamfering of wind power blade pultrusion plate - Google Patents
Stress concentration verification test method for chamfering of wind power blade pultrusion plate Download PDFInfo
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Abstract
The invention discloses a stress concentration verification test method for chamfering of a wind power blade pultrusion plate, which comprises the following steps of 1) manufacturing a sample test piece according to the structure of blade layering and the chamfering proportion of the pultrusion plate to be tested; 2) one end of the test piece is fixed with the clamp through a hexagon bolt and a nut, and the other end of the test piece is connected to the hydraulic actuator through the clamp; 3) deducing the limit design load and the fatigue design load of the pultruded slab; 4) according to the tensile fatigue test peak load and the tensile fatigue test valley load, a load is applied to the test piece through the hydraulic actuator, the fatigue test is carried out, when the cycle number reaches the set number, the part test is completed, and at the moment, whether the chamfer design of the drawing plate is safe or not can be verified. The method can effectively solve the problems of long test period and high test cost of verifying the stress concentration of the chamfer angle of the pultruded plate.
Description
Technical Field
The invention relates to the technical field of wind power generation fan blades, in particular to a stress concentration verification test method for chamfering of a pultrusion plate of a wind power blade.
Background
The development trend of high performance and low cost of the wind turbine generator set also puts higher requirements on the wind turbine blade which is a core component of the wind turbine generator set, and how to achieve low cost while realizing high generating capacity becomes the subject of the research on the wind turbine blade. The contribution to high power generation in terms of the blade mainly comes from aerodynamic appearance and high rigidity, the improvement of the unit power generation depends on the rigidity of the blade, and the rigidity of the blade mainly comes from the modulus of materials used by the spar caps. Therefore, the method is particularly important for improving the modulus of the existing glass fiber material by changing the forming process. The pultrusion process is a forming mode which can improve the modulus of the glass fiber material by 30 percent as a relative pouring process, and becomes a solution which is in line with the era. The pultrusion process is adopted to fully excavate the performance of the glass fiber fabric, and the power consumption cost of the wind turbine generator is reduced.
The pultrusion process is to continuously produce the glass fiber reinforced plastic sheet with unlimited length by molding and curing the continuous glass fiber bundles, belts or cloths and the like which are impregnated with the resin glue solution through a drawing and pressing mold under the action of traction force. Because the automation degree is high, the production efficiency is high, and the batch use of the material is facilitated.
Since the pultruded panel is a sheet material with a certain thickness, and the thickness dimension of a single layer is larger (about 3-5 times) than that of a perfusion single layer, the problem of stress concentration caused by the starting and stopping positions of the pultruded panel is a key problem needing to be researched when the pultruded panel is applied to the blade. The stress concentration coefficient can be further verified and determined by testing components because the finite element method can only be used as a selection guide and cannot completely determine the coefficient of stress concentration caused by the starting point and the ending point of the chamfer because the analysis area size is small and is sensitive to the grid size.
According to the DNVGL specification requirements, the static test of a component with a chamfer size at least needs 5 test pieces, and the fatigue test needs 4 stress levels to obtain the SN curve of the pultrusion chamfer component.
The load is a sine wave with a load ratio of 0.1:
the number of cycles of 4 test pieces under a certain load is 10 4 Next time
The number of cycles of 4 test pieces under a certain load is 10 5 Next time
The number of cycles of 4 test pieces under a certain load is 2 x 10 6 Next time
The cycle number of 3 test pieces under a certain load is 10 7 Next time
According to the verification of selecting 3 chamfer sizes at one time, at least 45 sample pieces are needed, the test period is about one year, and the test cost is more than 150 thousands. With the strong competition of the wind power market, the design, process manufacturing and full-size blade testing period of the development of a new blade product is generally about 1 year. Therefore, the method for pultrusion of the SN curve of the chamfer part in the mode can not catch up with the development progress of blade products seriously, so that an alternative testing method is urgently needed, namely, the requirements of design certification are met, and the development progress of new products can also be met.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, provides a method for verifying and testing the stress concentration of a chamfer of a pultruded plate of a wind turbine blade, and can effectively solve the problems of long test period and high test cost of the stress concentration verification of the chamfer of the pultruded plate.
In order to achieve the purpose, the technical scheme provided by the invention is as follows: a stress concentration verification test method for a wind power blade pultrusion plate chamfer comprises the following steps,
1) manufacturing a sample according to the blade laying structure and the chamfering proportion of the pultruded panel to be tested, respectively paving a reinforcing layer at two ends of the outer side of each inner skin, and after paving, pouring and molding the reinforcing layers into a whole through a vacuum pouring process to obtain a pultruded panel chamfering part test piece;
2) a plurality of hole sites for connection are respectively processed at two ends of the test piece, wherein one end of the test piece is fixed with a clamp through a hexagon bolt and a nut, the other end of the test piece is connected to a hydraulic actuator through the clamp, and the test piece is prevented from being damaged in advance due to stress concentration after holes are formed in the two ends of the test piece through laying of the reinforcing layer;
3) carrying out finite element analysis on the full-size blade model based on the limit working condition and the fatigue working condition to obtain the maximum limit strain and the fatigue strain of the blade pultrusion plate material, and then deducing the limit design load and the fatigue design load of the pultrusion plate;
4) performing static test on the test piece to obtain static tensile failure load F u ；
The Goodman formula (3) is derived by combining the load ratio formula (1) and the similar triangle formula (2),
wherein R is a load ratio, F a The load is the fatigue test amplitude load when the load ratio is 0.1; f m The mean load of the fatigue test when the load ratio is 0.1; f a(-1) Designing an amplitude load for fatigue when the load ratio is-1; f u Breaking the load for static tension;
and then deducing the peak load F of the tensile fatigue test by combining the Goodman formula (3) with the amplitude load formula (4) and the load ratio formula (5) max Equation (6) and tensile fatigue test valley load F min Equation (7) of (a), thereby converting the fatigue design load with the load ratio of-1 into the fatigue test load with the load ratio of 0.1,
F min ＝R*F max (7)
wherein R is a load ratio, F m The mean load of the fatigue test when the load ratio is 0.1; f a(-1) Designing an amplitude load for fatigue with a load ratio of-1; f u Breaking the load for static tension;
and applying a load to the test piece through the hydraulic actuator according to the obtained tensile fatigue test peak load and the tensile fatigue test valley load, carrying out fatigue test, finishing the part test when the cycle times reach the set times, and verifying whether the chamfer design of the drawing plate is safe or not.
Furthermore, the pultrusion plates are laid according to a brick stacking mode, and splicing seams of the pultrusion plates are prevented from being on the same plane; and the diversion fabric is laid between the pultrusion plate and the pultrusion plate, so that resin diversion infusion is facilitated during vacuum infusion.
Furthermore, both ends of the test piece are in a fishtail shape.
Compared with the prior art, the invention has the following advantages and beneficial effects:
the method for verifying and testing the stress concentration of the chamfer angle of the pultruded plate is simple, greatly shortens the test period and cost of the pultruded plate, and provides a feasible solution for the application and development of the glass fiber pultruded plate adopted by the new type blade beam cap.
Drawings
FIG. 1 is a model diagram of a finite element analysis performed in the method of the embodiment.
FIG. 2 is a flowchart of an iterative design of the chamfer ratio of the pultruded slab in the method of the embodiment.
FIG. 3 is an exploded view of a test piece of a drawdown board in the method of the example.
FIG. 4 is a sectional view of an airfoil section of the blade in the method of the embodiment.
FIG. 5 is a schematic representation of the placement of a deflector fabric between pultruded panels in a method according to an embodiment.
FIG. 6 is a schematic structural diagram of a test strip in the method according to the embodiment.
Detailed Description
The present invention is further illustrated by the following examples.
The wind power blade pultrusion plate chamfer design and chamfer stress concentration verification test method comprises the following steps,
1) as shown in fig. 1, according to the structure of the blade layer, a finite element model is constructed and modeled in sequence according to the sequence of an inner skin 1, a pultruded plate 2 with a chamfer, a pultruded plate 3 without a chamfer, an outer skin 4, a pultruded plate 3 without a chamfer, a pultruded plate 2 with a chamfer and the inner skin 1, and the two sides of the outer skin 4 in the model are mutually symmetrical by taking the outer skin 4 as a center, so as to prevent the generation of additional bending moment during finite element analysis;
2) the chamfering proportion of the pultrusion plate in the model is the ratio of the chamfering length w to the chamfering thickness h, then one end of the model is fixed, and the other end of the model is applied with an initial tensile load; changing the chamfer length w under a certain chamfer thickness h by using a parametric finite element analysis method, and carrying out iterative analysis to obtain the most appropriate chamfer proportion as shown in figure 2; the specific process of the iterative analysis is as follows: setting the chamfer length w of the pultruded plate as a fixed value, and obtaining the initial chamfer proportion of the pultruded plate by setting the initial chamfer thickness h; obtaining the stress distribution of the chamfer tip area of the pultruded panel through finite element calculation, judging whether the stress value reaches the limit stress, and outputting the tensile load under the chamfer proportion of the pultruded panel if the stress value reaches the limit stress; if not, continuing to increase the load until reaching the ultimate stress level, and outputting the final tensile load under the chamfer ratio; returning to modify the chamfer length w of the pultruded plate, further modifying the chamfer proportion of the pultruded plate, repeating finite element analysis to obtain tensile loads under different chamfer proportions, and selecting the most appropriate chamfer proportion according to the tensile load value simulated by the finite element;
3) as shown in fig. 3, a sample is manufactured according to the structure of the blade laying layer and the most appropriate chamfer ratio of the pultruded plate selected in the step 2), the sample sequentially comprises an inner skin 1, a pultruded plate 2 with a chamfer, a pultruded plate 3 without a chamfer, an outer skin 4, a pultruded plate 3 without a chamfer, a pultruded plate 2 with a chamfer and an inner skin 1 from top to bottom, two ends of the test piece are fishtail-shaped, then reinforcing layer triaxial cloth 5 is respectively paved on the structures with the fishtail-shaped structures at the two ends, and after paving is completed, the test piece is molded into a whole through a vacuum perfusion process to obtain the test piece of the chamfer part of the pultruded plate; as shown in fig. 4, after the beam cap is stressed during the test of the full-size blade 6, transverse cracks are easily generated in the splicing seam area, so that the pultruded slab 2 is laid in the blade 6 mold according to a brick stacking mode, and the splicing seams of the pultruded slab 2 are prevented from being on one plane; as shown in fig. 5, a diversion fabric 7 is laid between the pultruded panel 2 and the pultruded panel 2, so as to facilitate resin diversion infusion during vacuum infusion;
4) because the test load is large, the fish tail end of the test piece is clamped only by the extrusion friction force, and the fish tail end can slide, a plurality of hole sites 8 for connection are respectively processed at the fish tail ends at two sides, as shown in fig. 6, and meanwhile, due to the laying of the reinforcing layer triaxial cloth, the fish tail end is prevented from being damaged in advance due to stress concentration after the hole is formed; the fish tail end of one end of the test piece is fixed with the clamp through a hexagon bolt and a nut, and the fish tail end of the other end of the test piece is connected to the hydraulic actuator through the clamp;
5) based on the limit working condition and the fatigue working condition, carrying out finite element analysis on the full-size blade model to obtain the maximum limit strain and the fatigue strain of the pultruded plate material of the blade, and then deducing the limit design load and the fatigue design load of the pultruded plate to be used as the input design requirement of the test piece test;
6) performing static test on the test piece to obtain static tensile failure load F u ；
In combination with the Goodman formula (3) derived from the load ratio formula (1) and the similar triangle formula (2),
wherein R is a load ratio, F a The load is the fatigue test amplitude load when the load ratio is 0.1; f m The mean load of the fatigue test when the load ratio is 0.1; f a(-1) Designing an amplitude load for fatigue with a load ratio of-1; f u Breaking the load for static tension;
and then deducing the peak load F of the tensile fatigue test by combining the Goodman formula (3) with the amplitude load formula (4) and the load ratio formula (5) max Equation (6) and tensile fatigue test valley load F min The formula (7) of (a), thereby converting the fatigue design load with the load ratio of-1 into the fatigue test load with the load ratio of 0.1, performing load conversion, and aiming at considering the influence of the mean value load on the fatigue damage of the component in the test process, reducing the test load, making the damage under the test load consistent with the damage under the design load as much as possible,
F min ＝R*F max (7)
wherein R is a load ratio, F m The mean load of the fatigue test when the load ratio is 0.1; f a(-1) Designing an amplitude load for fatigue with a load ratio of-1; f u Breaking the load for static tension;
and applying a load to the test piece through the hydraulic actuator according to the obtained tensile fatigue test peak load and the tensile fatigue test valley load, carrying out fatigue test, finishing the part test when the cycle times reach the set times, and verifying whether the chamfer design of the drawing plate is safe or not.
The above-mentioned embodiments are merely preferred embodiments of the present invention, and the scope of the present invention is not limited thereto, so that variations based on the shape and principle of the present invention should be covered within the scope of the present invention.
Claims (3)
1. A stress concentration verification test method for chamfering of a wind power blade pultrusion plate is characterized by comprising the following steps: comprises the following steps of (a) preparing a solution,
1) constructing finite element models according to the construction of blade layers in sequence of an inner skin, a pultruded plate with a chamfer, a pultruded plate without a chamfer, an outer skin, a pultruded plate without a chamfer, a pultruded plate with a chamfer and the inner skin, and in the models, two sides of the outer skin are symmetrical with each other by taking the outer skin as the center so as to prevent the generation of additional bending moment during finite element analysis; the chamfering proportion of the pultrusion plate in the model is the ratio of the chamfering length to the chamfering thickness, then one end of the model is fixed, and the other end of the model is applied with an initial tensile load; changing the length of the chamfer by using a parameterized finite element analysis method under the condition that the thickness of the chamfer is kept unchanged, and carrying out iterative analysis to obtain the most appropriate chamfer proportion; the specific process of the iterative analysis is as follows: setting the chamfer length of the pultrusion plate as a fixed value, and obtaining the initial chamfer proportion of the pultrusion plate by setting the initial chamfer thickness; obtaining the stress distribution of the chamfer tip area of the pultruded panel through finite element calculation, judging whether the stress value reaches the limit stress, and outputting the tensile load under the chamfer proportion of the pultruded panel if the stress value reaches the limit stress; if not, continuing to increase the load until reaching the ultimate stress level, and outputting the final tensile load under the chamfer ratio; returning to modify the chamfer length of the pultruded plate, further modifying the chamfer proportion of the pultruded plate, repeating finite element analysis to obtain tensile loads under different chamfer proportions, and selecting the most appropriate chamfer proportion according to the tensile load value simulated by the finite element; then manufacturing a sample according to the structure of the blade layer and the most appropriate chamfer angle proportion, respectively paving a reinforcing layer at two ends of the outer side of each inner skin, and after paving, pouring and molding into a whole through a vacuum pouring process to obtain a test piece of the chamfer angle part of the pultrusion plate;
2) a plurality of hole sites for connection are respectively processed at two ends of the test piece, wherein one end of the test piece is fixed with a clamp through a hexagon bolt and a nut, the other end of the test piece is connected to a hydraulic actuator through the clamp, and the test piece is prevented from being damaged in advance due to stress concentration after holes are formed in the two ends of the test piece through laying of the reinforcing layer;
3) carrying out finite element analysis on the full-size blade model based on the limit working condition and the fatigue working condition to obtain the maximum limit strain and the fatigue strain of the blade pultrusion plate material, and then deducing the limit design load and the fatigue design load of the pultrusion plate;
4) performing static test on the test piece to obtain static tensile failure load F u ；
The Goodman formula (3) is derived by combining the load ratio formula (1) and the similar triangle formula (2),
wherein R is a load ratio, F a The load is the fatigue test amplitude load when the load ratio is 0.1; f m The mean load of the fatigue test when the load ratio is 0.1; f a(-1) Designing an amplitude load for fatigue with a load ratio of-1; f u Breaking the load for static tension;
and then deducing the peak load F of the tensile fatigue test by combining the Goodman formula (3) with the amplitude load formula (4) and the load ratio formula (5) max Equation (6) and tensile fatigue test valley load F min Equation (7) of (a), thereby converting the fatigue design load with the load ratio of-1 into the fatigue test load with the load ratio of 0.1,
F min ＝R*F max (7)
wherein R is a load ratio, F m The mean load of the fatigue test when the load ratio is 0.1; f a(-1) Designing an amplitude load for fatigue with a load ratio of-1; f u Breaking the load for static tension;
and applying a load to the test piece through the hydraulic actuator according to the obtained tensile fatigue test peak load and the tensile fatigue test valley load, carrying out fatigue test, finishing the part test when the cycle times reach the set times, and verifying whether the chamfer design of the drawing plate is safe or not.
2. The wind power blade pultruded panel chamfer stress concentration verification test method according to claim 1, characterized in that: in the step 1), the pultrusion plates are laid according to a brick stacking mode, and splicing seams of the pultrusion plates are prevented from being on the same plane; and the flow guide fabric is laid between the pultrusion plates, so that resin flow guide infusion is facilitated during vacuum infusion.
3. The wind power blade pultruded panel chamfer stress concentration verification test method according to claim 1, characterized in that: in the step 1), two ends of the test piece are in a fishtail shape.
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| CN103217282B (en) * | 2013-03-26 | 2015-04-22 | 中国科学院工程热物理研究所 | Fatigue test method of blade scaling model of horizontal axis wind turbine based on equal-service-life principle |
| CN108661853A (en) * | 2018-02-01 | 2018-10-16 | 上海电气风电集团有限公司 | A kind of wind electricity blade main beam structure and preparation method thereof |
| CN208921575U (en) * | 2018-07-17 | 2019-05-31 | 常州达姆斯检测技术有限公司 | A kind of testing fatigue batten of pultrusion plate |
| CN109383049B (en) * | 2018-11-23 | 2023-09-22 | 明阳智慧能源集团股份公司 | Wind power blade embedded screw sleeve test piece and test authentication method realized by using same |
| DK180532B1 (en) * | 2019-04-23 | 2021-06-10 | Envision Energy Denmark Aps | A WIND WINDOW WING AND A METHOD FOR MANUFACTURING THE WIND WIND WING |
| CN110126303A (en) * | 2019-05-31 | 2019-08-16 | 连云港中复连众复合材料集团有限公司 | A method of fan blade of wind generating set girder is prepared with the wide pultruded panels of whole picture |
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Effective date of registration: 20230825 Address after: 014070 No. 8 Kechuang Avenue, Shiguai District, Baotou City, Inner Mongolia Autonomous Region Patentee after: Mingyang New Energy Materials Technology (Baotou) Co.,Ltd. Address before: 528437 No. 22 Torch Road, Torch Development Zone, Zhongshan City, Guangdong Province Patentee before: MING YANG SMART ENERGY GROUP Co.,Ltd. |