Concave U-Bolt Fastening Geometry for Lower Vehicle Joint Stress

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Solution Overview

Problem

Conventional U-bolts used for connecting mechanical parts in vehicles face high stress and strain concentrations, leading to potential fatigue cracks and reduced operational lifetime due to uneven stress distribution and sensitivity to loads during vehicle operation.

Innovation Solution

A fastening arrangement featuring elongated leg members and a curved member with a concave inner surface, which forms an integral part with the leg members, reduces stress concentrations by distributing loads over a larger contact area, and includes a mating support element with a convex surface to further reduce stress concentrations and improve connection security.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a conventional U-bolt is used to connect mechanical parts, then the connection is robust and secure, but stress concentrations occur leading to reduced operational lifetime

Engineering Contradiction:
Improveconnection robustnessVSAvoidoperational lifetime
Core Design Contradiction:
StrengthVSDuration of action of stationary object

Solution Approach 1:

The patent applies curvature to the inner surface of the U-bolt, specifically creating a concave surface portion that contacts the mechanical part. This curved geometry distributes the contact stress over a larger area compared to a flat surface, reducing stress concentrations that would otherwise lead to fatigue cracks and premature failure, thereby extending operational lifetime while maintaining connection robustness

Inventive Principle:
Principle #14Spheroidality (Curvature)

2Device complexity

If a conventional U-bolt with flat inner surface is used, then the structure is simple, but stress and strain concentrations occur under severe loads

Engineering Contradiction:
Improvestructure simplicityVSAvoidstress concentration
Core Design Contradiction:
Device complexityVSStress or pressure

Solution Approach 1:

The patent modifies only the local geometry of the U-bolt's inner surface by creating a concave surface portion at the contact area, while maintaining the overall simple U-bolt structure. This localized geometric change concentrates the stress distribution improvement exactly where it is needed (at the contact surface with the mechanical part) without complicating the entire fastening structure

Inventive Principle:
Principle #3Local quality

Data Source

PatentEP4008915B1A fastening arrangement and a vehicle arrangement
Publication Date: 2024.03.06 VOLVO TRUCK CORP
  • EP4008915B1 patent drawingFigure 1
  • EP4008915B1 patent drawingFigure 2A~2B
  • EP4008915B1 patent drawingFigure 3A~4B

AI summary

The present disclosure relates to a fastening arrangement (100) for retaining at least a first mechanical part (10) and a second mechanical part (20) to each other, the fastening arrangement comprising a first elongated leg member (102), a second elongated leg member (104) and a curved member (106) extending between the first and second elongated leg members, wherein the first elongated leg member, the second elongated leg member and the curved member form an inner space (108) arranged to accommodate at least a part of the first and second mechanical parts, the curved member comprises an inner surface (110) arranged to face a surface (12) of the first mechanical part, wherein each of the first and second elongated leg members comprises a portion (14) arranged to receive a respective tightening element (30) for retaining the first and second mechanical parts to each other, characterized in that the inner surface (110) of the curved member comprises a concave surface portion (112) as seen in a cross-section transverse to the extension of the curved member.