Wind Turbine Blade Bolt Neck Design for Shear Stress
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Solution Overview
Problem
Current connection joints for wind turbine rotor blades and rotor hubs face challenges in scaling with increasing blade sizes, leading to increased material and manufacturing costs, as well as insufficient structural integrity to handle the growing shear stresses.
Innovation Solution
A bolt design with a neck region having a reduced cross dimension compared to the blade end, which is threaded and includes an elliptical or cylindrical configuration, allowing for a smooth transition and maintaining a constant cross-sectional area, coupled with embedded inserts that increase the contact surface area with the composite material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional threaded stud bolts are directly inserted into composite material at the blade root, then the connection structure is simple, but the composite material has insufficient shear strength to transfer loads and deterioration occurs at the interface
Solution Approach 1:
The patent introduces metal inserts as intermediary components between the threaded stud bolts and the composite material. These inserts are embedded within the composite material at the blade root, providing a mechanically robust interface that can withstand shear loads. The inserts act as mediators that transfer forces between the bolts and the composite structure, preventing direct stress concentration on the weaker composite material.
2Strength
If metal inserts are embedded in the composite material to distribute forces, then the structural integrity is sufficient, but the joint size and material usage increase proportionally with blade size
Solution Approach 1:
The patent applies local quality by concentrating the reinforcement function in specific localized regions where the metal inserts are embedded within the composite material at the blade root. Rather than uniformly increasing the size of the entire joint structure, the inserts provide targeted structural enhancement only where needed - at the critical stress interface between the bolts and composite material. This allows the joint to maintain structural integrity for larger blades without proportionally increasing overall material usage.
3Power
If the blade length increases to produce more electrical energy, then the power generation capacity increases, but the joint experiences increased stresses that challenge design integrity
Solution Approach 1:
The patent utilizes composite materials in the form of metal inserts embedded within the composite blade structure. This composite approach combines the high strength and stiffness of metal inserts with the lightweight and aerodynamic properties of the composite blade material. The metal inserts provide the necessary mechanical strength to handle increased joint stresses from longer, heavier blades, enabling the blade to generate more power without compromising connection integrity.
Data Source
AI summary
A connecting joint for attaching a wind turbine rotor blade to a rotor hub includes a bolt having a blade end configured to be coupled to the rotor blade and a hub end configured to be coupled to the rotor hub. The bolt includes a neck region adjacent the blade end, wherein the neck region has a cross dimension less than a cross dimension of the blade end of the bolt. A wind turbine blade having such a connecting joint is also disclosed. Additionally, a method of making the connecting joint is disclosed.