Instrumented Fastener Transducers for Hidden Joint Damage Detection

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Solution Overview

Problem

Existing damage detection methods for fastened structures, particularly fastened joints, are hindered by the complex geometry of fasteners and multiple stacked materials, often requiring modification of the joint, which can lead to additional failure, and are ineffective in detecting hidden damage without disassembly.

Innovation Solution

A transducer assembly is integrated into the fastener, comprising a piezoelectric element and substrate, which is mechanically coupled within the fastener's cavity, allowing for non-invasive and non-destructive damage detection by ultrasonic wave propagation through the fastener and surrounding structure.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If traditional inspection methods (eddy currents or ultrasonic detection) are used, then damage detection capability is improved, but the complex geometry of fasteners and multiple stacked materials hinders sensor placement and modifies the joint, leading to additional failure risk

Engineering Contradiction:

Improvedamage detection capabilityVSAvoidjoint integrity

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The transducer assembly is nested within the cavity of the fastener itself, utilizing the existing fastener geometry as a housing for the inspection device. This eliminates the need for external sensor placement that would modify the joint, while enabling ultrasonic damage detection of the fastened structure.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The fastener serves dual functions: it both joins the structural components and houses the transducer assembly for inspection. The fastener inspects itself and the surrounding structure without requiring external inspection equipment that would modify the joint.

Inventive Principle:

Principle #25Self-service

2Measurement precision

If sensors or transducers are placed along the structure surface, within the drilled hole, or under a fastener, then damage detection capability is improved, but the joint between the fastener and structure is modified, leading to additional failure

Engineering Contradiction:

Improvedamage detection capabilityVSAvoidadditional failure risk

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The fastener is designed to perform multiple functions: structural joining and housing the transducer assembly. This multi-functionality eliminates the need for separate inspection equipment that would require modifying the joint, thereby avoiding additional failure risks.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The transducer assembly is nested within the pre-existing cavity of the fastener, utilizing the fastener's own geometry as the housing. This approach allows sensor placement without creating additional holes or modifications to the joint, thus avoiding sources of additional failure.

Inventive Principle:

Principle #7Nested doll (Nesting)

3Ease of operation

If visual inspection is used, then inspection simplicity is maintained, but damage hidden under fastener heads or between layers cannot be detected

Engineering Contradiction:

Improveinspection simplicityVSAvoiddamage detection capability

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

Visual inspection is replaced with ultrasonic wave-based detection. The transducer assembly generates and detects ultrasonic waves that propagate through the fastened structure, enabling detection of hidden damage that cannot be seen visually, while maintaining automated operation.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

The system effectively detects damage in fastened structures without modifying the fastener or installation process, providing sensitive detection of hidden damage and maintaining structural integrity.

Implementation Method 1

The electromechanical unit includes a piezoelectric element and a substrate. The piezoelectric element is disposed outside of the cavity of the fastener

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

The system effectively detects damage in fastened structures without modifying the fastener or installation process, providing sensitive detection of hidden damage

Methodology Applied

Scientific EffectPiezoelectric effect: Converse Piezoelectric Effect

Data Source

PatentEP3762714B1Damage detection system and method for detecting damage in fastened structures

Publication Date: 2025.09.03 METIS DESIGN CORP

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AI summary

Exemplary embodiments are directed to instrumented fasteners and associated damage detection systems for detecting damage in an assembled structure secured together by at least one instrumented fastener. The instrumented fastener forms a transducer assembly for detecting damage in the assembled structure. The fastener can include a cavity disposed at one end of the fastener. The transducer assembly includes an electromechanical unit at least partially inserted into and mechanically coupled within the cavity of the fastener. The electromechanical unit can include a piezoelectric element.