Anchor Nut Shoulder Structure for Thread Fatigue Relief

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing fasteners, particularly anchor bolts, face fatigue cracking issues under dynamic loads due to stress concentration at the foremost engaged thread turn when load transfer occurs directly through the nut's face, leading to reduced performance.

Innovation Solution

A fastener design featuring a nut with a forward nut section having at least one slot extending towards an outside shoulder, located axially between the forward and rearward nut sections, which redirects load transfer to the middle region of the nut, reducing stress peaks and enhancing fatigue performance by distributing loads more evenly across thread turns.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If load transfer occurs directly through the nut's face to the attachment part, then the structural design is simple, but stress concentration occurs at the foremost engaged thread turn leading to fatigue cracking

Engineering Contradiction:

Improvenut structureVSAvoidfatigue performance

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The nut is divided into two distinct sections: a first nut section with an outside shoulder for load transfer, and a second nut section with internal threads for engaging the threaded rod. This segmentation separates the load transfer function from the thread engagement function, preventing stress concentration at the thread roots while maintaining structural simplicity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The outside shoulder acts as an intermediary element between the attachment part and the threaded rod. It transfers loads from the attachment part directly to the threaded rod body, bypassing the threaded regions and eliminating stress concentration at the thread roots, thereby improving fatigue performance.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If the internal thread engages the external thread at the foremost region of the nut, then the load transfer path is short, but stress peaks occur at the first engaged thread turn

Engineering Contradiction:

Improveload transfer efficiencyVSAvoidstress at thread turn

Core Design Contradiction:

ProductivityVSStress or pressure

Solution Approach 1:

The load transfer is moved from the axial dimension (through the threads) to the radial dimension (through the outside shoulder). The outside shoulder transfers loads radially from the attachment part directly to the threaded rod body, bypassing the threaded regions entirely and eliminating stress peaks at the thread turns.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Data Source

PatentEP3947987B1Fastener and fastening arrangement including nut with load transfer shoulder

Publication Date: 2023.10.25 HILTI AG

Figure 1~2
Figure 3

AI summary

The invention relates to a fastener comprising an anchor bolt and a nut. The nut comprises a rearward nut section, a forward nut section located closer to an anchor portion of the anchor bolt than the rearward 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, wherein an internal thread of the nut extends at least in the forward nut section and the internal thread of the nut threadedly engages an external thread of a threaded rod of the anchor bolt at least in the forward nut section. The invention further relates to a fastening arrangement including such a fastener.