Wind Turbine Blade Root Insert for Fatigue-Resistant Load Transfer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The design of wind turbine blade hub connections faces significant challenges due to high stresses and fatigue, particularly in the bolted connections between the blade root and the hub, which are critical for the longevity and performance of the wind turbine.
Innovation Solution
An insert for the wind turbine blade root is designed with a bushing having a threaded bore and circumferential grooves, covered by a transition layer of alternating fibrous plies and windings, which provides a fatigue-resistant interface between the bushing and the insert body, enhancing the structural integrity and load transfer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a simple cylindrical steel bushing is embedded into the blade root, then the manufacturing process is simple and cost-effective, but the fatigue resistance and structural integrity of the blade hub connection are insufficient under high stresses and perpetual rotation
Solution Approach 1:
The insert employs a composite structure combining a steel bushing with a fibre-reinforced polymer matrix. The bushing provides load-bearing capacity while the composite material layer provides fatigue resistance and stress distribution. This composite approach resolves the contradiction by maintaining structural integrity and fatigue performance without requiring the entire insert to be made of complex high-performance materials throughout.
Solution Approach 2:
The insert features a transition layer with varying fibre orientations and winding patterns at different locations. The fibrous plies are arranged with specific orientation angles (e.g., ±45°, 0°, 90°) in different radial and axial positions to locally optimize stress distribution. This local quality variation enhances fatigue resistance at critical interfaces while maintaining overall structural efficiency.
2Reliability
If circumferential grooves with large depth-to-pitch ratio are machined into the bushing, then the anchoring effect is strong, but stress concentration increases reducing fatigue life
Solution Approach 1:
The design optimizes the circumferential groove parameters by controlling the depth A and pitch P such that the ratio A/P is less than 1. This parameter change balances the anchoring effect with stress concentration reduction. The grooves are deep enough to provide adequate mechanical interlocking with the transition layer while maintaining sufficient wall thickness to avoid excessive stress concentration that would compromise fatigue strength.
3Reliability
If the transition layer uses multiple alternating fibrous plies and windings, then the fatigue resistance and load transfer are enhanced, but the manufacturing complexity and production time increase
Solution Approach 1:
The transition layer is segmented into distinct functional zones: an inner layer with fibrous plies and windings for anchoring to the bushing, and an outer layer with different fibre orientations for load transfer to the insert body. This segmentation allows each layer to be optimized for its specific function while enabling modular manufacturing processes.
Solution Approach 2:
The bushing with circumferential grooves is prepared in advance before the transition layer is applied. The grooves are machined and positioned beforehand to ensure proper alignment and anchoring geometry. This preliminary action simplifies the subsequent layering process by providing a pre-configured substrate that guides the placement of fibrous plies and windings.
4Strength
If the bushing wall thickness is increased at the threaded bore region, then the crack resistance is improved, but the overall insert size and material usage increase
Solution Approach 1:
The bushing features variable wall thickness with a concentrated reinforcement zone at the threaded bore region where cracks are most likely to initiate and propagate. The end region has increased wall thickness to provide crack resistance, while the body region maintains optimal thickness for load transfer. This localized quality variation provides enhanced crack resistance only where needed, minimizing overall material usage.
Data Source
Figure 1~2
Figure 3~5
Figure 6a
AI summary
An insert (105) for a wind turbine blade root. The insert (105) has a bushing (40) and an outer surface with circumferential annular grooves (68). A transition layer (102) is built up around the bushing (40). The transition layer (102) has fibrous material sheet layers and filamentary material windings (80) in the grooves which alternate with fibrous plies (98) covering the grooves (68). Each fibrous ply (98) is anchored into the grooves (68) by the windings (80). Fibrous battens (148) are fitted around the transition layer (102) to form an insert body (108). Each batten (148) has a deltoid cross-section so that the battens give the insert a quadrilateral or trapezoidal cross-section.