Wind Turbine Blade Butt Joint With Low-Stiffness Wedge Inserts
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Solution Overview
Problem
Joining two stiff structures in a butt joint in wind turbine blades results in high strain concentrations around the joint, complicating handling and alignment, and requiring improved load distribution.
Innovation Solution
The wind turbine blade design incorporates wedge-shaped portions with lower stiffness than the main portions, allowing for easy alignment and distributing load transfer over a larger area by tapering the wedge-shaped portions away from the joint interface.
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 creating wedge-shaped recesses and portions at the joint interface with different stiffness characteristics. The wedge-shaped portions have reduced stiffness compared to the main plank bodies, creating a localized zone that gradually transitions from stiff to compliant material. This local modification allows the joint area to accommodate strain concentrations while maintaining the overall structural integrity and ease of handling of the planks.
Solution Approach 2:
The patent changes the stiffness parameter locally at the joint interface by creating wedge-shaped portions with reduced material density or different material composition. The gradual tapering of these wedge-shaped portions creates a continuous gradient in stiffness parameter from the stiff main plank to the more compliant joint interface, thereby reducing stress concentrations while maintaining accurate placement capability.
2Strength
If wedge-shaped portions with smaller stiffness are introduced at the joint interface, then stress concentration is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent segments the plank structure into three distinct zones: the main stiff plank body, the wedge-shaped transition portions at the joint interface, and the surrounding material. This segmentation allows each zone to be optimized independently - the main body for structural strength, the wedge-shaped portions for stress distribution, and the surrounding material for load bearing. The segmented approach simplifies manufacturing by allowing pre-fabrication of wedge-shaped inserts that can be integrated into the main plank structure.
Data Source
AI summary
A wind turbine blade is provided, including two planks joined with each other in a longitudinal direction of the planks at joining surfaces by a butt joint, wherein each plank includes a main portion with a wedge-shaped recess and a wedge-shaped portion filling the recess, each wedge-shaped portion has a respective one of the joining surfaces and is tapered from its joining surface in a direction away from its joining surface, and a stiffness of a material of the wedge-shaped portions is smaller than a stiffness of a material of the main portions. By having the wedge-shaped portions, the load is transferred to the surrounding material over a larger area which reduces the stress concentration.