Wind Turbine Blade Butt Joint With Tapered Wedges for Stress Relief
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Solution Overview
Problem
Joining two stiff structures in a wind turbine blade using a butt joint results in high strain concentrations around the joint, which can lead to stress concentration issues.
Innovation Solution
The wind turbine blade design incorporates wedge-shaped portions with a lower stiffness than the main portions at the joint interface, allowing for easy handling and alignment, and distributes load transfer over a larger area by tapering these portions away from the joint, reducing stress concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If two stiff planks are joined by a butt joint, then easy handling and accurate placement are achieved, but high strain concentrations occur around the joint
Solution Approach 1:
The patent applies local quality by introducing wedge-shaped portions with different material properties (lower stiffness, higher damping) specifically at the joint interface between planks. This localized modification allows the joint area to have different mechanical characteristics than the main plank body, reducing stress concentration while maintaining the overall structural integrity and ease of handling of the planks.
Solution Approach 2:
The patent changes the material parameters (stiffness, damping) at the joint interface by using wedge-shaped portions made of materials with different properties than the main planks. The tapered geometry gradually transitions the stiffness parameter from the joint interface toward the main plank, reducing abrupt stress concentrations while maintaining ease of assembly.
2Strength
If wedge-shaped portions with lower stiffness are introduced at the joint interface, then stress concentration is reduced, but the complexity of manufacturing increases
Solution Approach 1:
The patent segments the plank structure into distinct components: main planks and separate wedge-shaped portions. This segmentation allows each component to be manufactured independently using optimized processes, then assembled together. The wedge-shaped portions can be pre-formed and inserted into recesses in the main planks, simplifying the overall manufacturing complexity despite the added functional sophistication.
Solution Approach 2:
The wedge-shaped portions act as intermediary elements between the main planks at the joint interface. These intermediaries are designed to fit into recesses in the planks and can be attached using conventional joining methods, serving as a bridge that reduces stress concentration without requiring complex integrated manufacturing processes.
Data Source
Figure 1
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AI summary
A wind turbine blade (3), comprising two planks (8, 9) joined with each other in a longitudinal direction (L1) of the planks (8, 9) at joining surfaces (12, 13) by a butt joint (14), wherein each plank (8, 9) comprises a main portion (18, 20) with a wedge-shaped recess (19, 21) and a wedge-shaped portion (15, 16) filling the recess, each wedge-shaped portion (15, 16) has a respective one of the joining surfaces (12, 13) and is tapered from its joining surface (12, 13) in a direction (D1, D2) away from its joining surface (12, 13), and a stiffness of a material of the wedge-shaped portions (15, 16) is smaller than a stiffness of a material of the main portions (18, 20). By having the wedge-shaped portions, the load is transferred to the surrounding material over a larger area which reduces the stress concentration.