Anchor Nut Load Transfer Shoulder for Thread Fatigue Relief
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Solution Overview
Problem
Existing fasteners, particularly anchor bolts with nuts, experience fatigue cracking under dynamic loads due to stress concentrations at the foremost engaged thread turn, leading to reduced performance in dynamic load situations.
Innovation Solution
The fastener design includes a nut with a rearward and forward nut section, an outside shoulder for load transfer, and an internal thread that engages the external thread in the forward nut section, distributing load through an axial middle region to equalize stress and reduce peak loads on individual thread turns, with optional features like slots and a spherical washer for further flexibility and misalignment compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If load transfer occurs at the face of the nut, then the nut can be simply designed, but a pronounced stress maximum arises at the foremost engaged thread turn leading to fatigue cracking
Solution Approach 1:
The load transfer location is moved from the axial dimension (nut face) to a different axial position (outside shoulder between forward and rearward nut sections). This dimensional relocation of the load transfer interface separates the stress concentration point from the most critically loaded thread turn, reducing fatigue stress peaks while maintaining simple nut geometry.
2Ease of manufacture
If the foremost engaged thread turn carries highest load increment and total bolt tension, then the nut design is simple, but the stress peak promotes fatigue crack initiation
Solution Approach 1:
By relocating the load transfer interface to the outside shoulder at a different axial position, the patent redistributes the stress profile along the thread engagement. This causes the highest stress increment and highest total tension to occur at different thread turns, equalizing the stress distribution and preventing localized fatigue crack initiation, while requiring only minimal structural modification to the nut.
3Stability of the object's composition
If elastic pitch mismatch increases surface pressure in the foremost turn, then thread engagement is secure, but load concentration increases fatigue risk
Solution Approach 1:
The patent relocates the load transfer interface to the outside shoulder at an axial position between the forward and rearward nut sections. This dimensional shift causes the elastic pitch mismatch effects to manifest at a different location in the thread engagement, distributing the surface pressure more evenly and preventing excessive load concentration at any single thread turn, thereby improving dynamic load performance while maintaining engagement stability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design significantly reduces stress peaks and enhances fatigue performance by distributing load evenly across thread turns, particularly in dynamic load conditions, and allows for a more robust and easy-to-manufacture fastener.
Implementation Method 1
the threaded rod (37) has an external thread (63) and is connected to the anchor portion (31) to transfer tensile force into the anchor portion (31)
Implementation Method 2
the internal thread (64) of the nut (40) threadedly engages the external thread (63) of the threaded rod (37)
Implementation Method 3
an outside shoulder (44) for load transfer into the nut (40), which is located between, in particular located axially between, the forward nut section (45) and the rearward nut section (43) and which faces the anchor portion (31) of the anchor bolt (30)
Data Source
AI summary
A fastener includes an anchor bolt and a nut. The nut has a nut hole and an internal thread. The anchor bolt has an anchor portion and a threaded rod that has an external thread and that is connected to the anchor portion. The nut is arranged on the threaded rod and the internal thread of the nut threadedly engages the external thread of the threaded rod. The nut has a rearward nut section, a forward nut section, and an outside shoulder for load transfer into the nut which is located between the forward nut section and the rearward nut section and which faces the anchor portion of the anchor bolt. The internal thread of the nut extends at least in the forward nut section and threadedly engages the external thread of the threaded rod at least in the forward nut section.