Tower Flange Wedge Geometry for Fatigue-Resistant Bolted Joints
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Solution Overview
Problem
Bolted flange connections in large tower structures, such as wind turbine towers, face challenges with structural strength, fatigue resistance, nut loosening due to vibrations, and corrosion from dynamic loads and water ingress.
Innovation Solution
A flange connection design featuring a ring-shaped flange element with a wedge and heel surface, providing a wedge surface angle and heel surface angle that create a pre-stressed condition to resist dynamic loads, prevent water ingress, and maintain contact under extreme loads, thereby reducing fatigue and corrosion risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional flat flange connections are used, then assembly is simple, but fatigue resistance deteriorates due to dynamic bolt stresses
Solution Approach 1:
The flange connection uses a spherical ball joint instead of a flat rigid connection. The ball and socket geometry allows rotational movement to accommodate dynamic loads, transforming the rigid flat flange interface into a curved, flexible joint that reduces stress concentrations and improves fatigue resistance while maintaining assembly simplicity.
Solution Approach 2:
The flange connection incorporates a ball joint mechanism that enables dynamic adjustment. The ball can rotate within the socket to adapt to varying load directions from wind and waves, transforming a static rigid connection into a dynamic system that actively responds to environmental forces, thereby improving fatigue resistance without complicating assembly.
2Strength
If bolted flange connections are used to join tower sections, then structural strength is achieved, but nut loosening occurs due to vibrations from wind loads
Solution Approach 1:
The ball joint design intentionally introduces controlled mechanical movement to counteract harmful vibrations. By allowing the ball to rotate and absorb vibrational energy from wind loads, the system dissipates vibration energy through the joint's degrees of freedom rather than transmitting it to the bolts and nuts, preventing loosening while maintaining structural strength.
Solution Approach 2:
The ball joint acts as an intermediary element between the tower sections. Instead of directly transmitting all forces and vibrations through the bolted flange connection, the ball joint mediates the load transfer, absorbing and redirecting vibrational forces, thereby protecting the fastening system from loosening while preserving structural integrity.
3Reliability
If flange connections are made watertight, then corrosion resistance is improved, but structural flexibility under dynamic loads deteriorates
Solution Approach 1:
The patent employs a flexible membrane or gasket system that can deform with the ball joint's movement. This flexible sealing element maintains the watertight barrier against corrosion while accommodating the rotational and positional changes of the ball joint under dynamic wind and wave loads, thus preserving both corrosion resistance and structural flexibility.
Solution Approach 2:
The sealing system is designed to be dynamic rather than rigid. The seal can adjust its position and shape in response to the ball joint's movement, maintaining the watertight seal throughout the range of motion. This dynamic sealing approach preserves corrosion resistance while allowing the necessary structural flexibility to handle dynamic environmental loads.
Data Source
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AI summary
A flange element (20, 50, 74) for a flange connection (92) with a longitudinal centre axis A is disclosed where the flange element (20, 50, 74) comprises a flange part (21, 51, 75) having a front side (29, 59, 83) with a front surface (30, 60, 84). The flange part (21, 51, 75) is provided with a flange wedge (32, 62, 86) comprising a flange wedge surface (33, 63, 87) that is part of the front surface (30, 60, 84), and a flange heel (34, 64, 88) comprising a flange heel surface (35, 65, 89) that is part of the front surface (30, 60, 84). The flange wedge surface (33, 63, 87) makes a wedge surface angle α1 and the flange heel surface (35, 65, 89) makes a heel surface angle β with a plane P that is perpendicular to the longitudinal centre axis A of the flange element (20, 50, 74). There is also disclosed a flange connection (92) comprising two flange elements (20, 50, 74) and a tower structure (16) comprising at least two tower sections (44, 68, 94, 100) where adjacent tower sections are securely connected with a flange connection (92).