Flanged Nut Structure for Bolt Thread Fatigue Relief
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Solution Overview
Problem
Existing nuts fail to effectively reduce the load on the first fastening meshing thread of bolts, leading to fatigue fractures, and their production is hindered by complex shapes and poor producibility.
Innovation Solution
A nut design with a flange part and a shallow depression on the bearing surface, where the depression's depth is less than 1.5-fold the thread pitch, allowing for commercial production and reduced load distribution to the first fastening meshing thread.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a notch is formed on the threaded hole side of the bearing surface to reduce load on the first meshing thread, then the fatigue fracture life is improved, but the bearing surface area is reduced causing the nut to sink into the fastened object or buckle
Solution Approach 1:
The invention transitions from a 2D surface modification (notch on bearing surface) to a 3D volumetric modification (cavity extending axially into the nut body). This allows load redistribution through the third dimension without compromising the bearing surface area, resolving the contradiction between fatigue life improvement and bearing surface integrity
Solution Approach 2:
The cavity is segmented into multiple regions with different depths - shallower near the bearing surface and deeper toward the release side. This segmentation allows progressive load redistribution while maintaining structural integrity of the bearing surface, preventing both sinking and buckling
2Strength
If deep cuts or convex spaces are formed on the threaded hole side to reduce rigidity and increase flexibility, then the burden on the thread valley is reduced, but the production complexity and tool wear increase significantly
Solution Approach 1:
The invention changes the depth parameter of the cavity modification from deep (7+ thread pitches in prior art) to shallow (less than 1.5 thread pitches). This parameter change achieves the necessary load redistribution while making the feature accessible to standard forging and machining tools, dramatically improving manufacturability
Solution Approach 2:
Instead of applying the full depth modification throughout the entire thread engagement zone, the cavity is applied partially - only in the region where it most effectively redistributes load without compromising structural integrity. This partial action achieves the fatigue life improvement with minimal impact on manufacturing
3Strength
If the bearing surface is made narrow to reduce load on the first thread, then the load distribution is improved, but the fastening force is insufficient and the nut cannot be fastened properly
Solution Approach 1:
The invention moves the load reduction mechanism from the 2D bearing surface plane to the 3D axial dimension by creating a cavity that extends into the nut body. This allows load redistribution without reducing the bearing surface area, maintaining both proper load distribution and sufficient fastening force
Data Source
Figure 1(a)
Figure 1(b)~1(c)
Figure 1(d)~1(e)
AI summary
Provided is a nut which extends the fatigue life of a bolt in bolt-nut fastening and which is easy to produce. A nut (1) includes a nut body (2) with a flange part (5) and a shallow depression (7) with a depth of less than 1.5 pitches on the axial side of a bearing surface (5s), which is a flat surface extending perpendicular to an axis on the fastening side of the nut body (2). This nut (1) preferably has an additional rigidity part (6) on the release side.