Bolt Connection With Anti-Fatigue Sleeve for Flange Waviness
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Solution Overview
Problem
The assembly of segmented steel towers in wind power plants faces challenges due to flange misalignment/waviness, which reduces bolt prestress and affects the fatigue life of bolts, leading to increased manufacturing and assembly costs and complexities.
Innovation Solution
A bolt connection using a long threaded bar with an anti-fatigue sleeve pressed against the flange to compensate for waviness, increasing the clamp length and reducing the impact of misalignment on bolt tension, thereby enhancing the fatigue life of the connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If segmented steel tower sections are used to enable transport, then the tower can be assembled in sections, but flange misalignment and waviness occur leading to reduced bolt prestress and fatigue life
Solution Approach 1:
The tower is divided into transportable sections with flanges that can be assembled in the field. The segmentation enables transport of sections that would otherwise be too long, while the anti-fatigue sleeve compensates for the connection reliability issues arising from segmentation-induced misalignment
Solution Approach 2:
An anti-fatigue sleeve is introduced as an intermediary component between the flange and the bolt. This sleeve compensates for misalignment and waviness by providing a longer clamp length, thereby maintaining bolt prestress and fatigue life despite the segmentation of the tower
2Reliability
If additional manufacturing measures are taken to solve flange misalignment, then connection reliability improves, but manufacturing time and cost increase
Solution Approach 1:
The anti-fatigue sleeve is pre-installed on the bolt before assembly. This preliminary action ensures that the compensation for misalignment is already in place during assembly, eliminating the need for time-consuming post-assembly adjustments or shimming operations
Solution Approach 2:
The anti-fatigue sleeve is a simple, inexpensive component that compensates for manufacturing tolerances. Rather than investing in complex manufacturing processes or expensive precision machining, a relatively simple sleeve is used to achieve the desired connection reliability
3Manufacturing precision
If on-site milling and shimming are performed to correct flange waviness, then connection precision improves, but assembly complexity and cost increase
Solution Approach 1:
The problem of flange misalignment is extracted from the flange itself and transferred to the anti-fatigue sleeve. Instead of modifying the flange through milling or adding complex shimming systems, the compensation function is isolated to a simple sleeve component that absorbs the misalignment
Solution Approach 2:
The anti-fatigue sleeve automatically compensates for misalignment through its design geometry. The sleeve's longer clamp length inherently provides tolerance for waviness without requiring active adjustment mechanisms, sensors, or complex control systems
Data Source
Figure 1~2
Figure 3~4
AI summary
A bolt connection is provided for connecting two flanges. The bolt connection includes a threaded bar extending through a hole of a first flange and a hole of a second flange, the first flange abutting the second flange; an anti-fatigue sleeve; and a nut. The anti-fatigue sleeve is disposed on the threaded bar on the side of the first flange between the nut and the first flange, the nut is configured to be screwed onto the threaded bar and is configured to press the anti-fatigue sleeve against the first flange to fasten the first flange and the second flange together.