Lamb Wave Mode Identification Using Single Transducer Thickness Measurement

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Solution Overview

Problem

Conventional methods for determining Lamb wave modes in structural health monitoring require two transducers on opposite sides of a structure, which can be impractical and costly due to the need for additional equipment and wiring, limiting their application in certain structural health monitoring scenarios.

Innovation Solution

A method and system that uses a single transducer mounted on one side of a structure to transmit and measure Lamb waves, allowing for the identification of wave modes by measuring instantaneous thickness and propagation characteristics, eliminating the need for opposing transducers and reducing system complexity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If two piezoelectric transducers are placed on opposite sides of the structure to accurately measure Lamb wave modes, then measurement precision is improved, but device complexity and cost increase

Engineering Contradiction:

ImproveLamb wave mode identification accuracyVSAvoidtransducer arrangement complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent extracts the thickness measurement function from the dual-transducer system and implements it through a single transducer using ultrasonic echo technique. The transducer emits an ultrasonic pulse and measures the echo time from the back wall of the structure, thereby obtaining thickness information without requiring a second transducer on the opposite side.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The single piezoelectric transducer performs multiple functions: it generates Lamb waves for structural health monitoring, measures instantaneous thickness through ultrasonic echo, and identifies wave modes by combining thickness data with wave propagation characteristics. This multi-functional approach eliminates the need for separate opposing transducers.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Measurement precision

If two piezoelectric transducers are placed exactly opposite one another to measure phase characteristics, then measurement precision is improved, but ease of operation deteriorates

Engineering Contradiction:

Improvephase measurement accuracyVSAvoidtransducer positioning difficulty

Core Design Contradiction:

Measurement precisionVSEase of operation

Solution Approach 1:

The patent replaces the mechanical alignment requirement of opposing transducers with an ultrasonic echo-based thickness measurement system. Instead of mechanically positioning transducers exactly opposite each other, the system uses the transducer's own emitted ultrasonic pulse and measures the echo time, eliminating the need for precise mechanical positioning.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If additional transducers and wiring are added to implement conventional Lamb wave mode identification, then measurement precision is improved, but manufacturing cost increases

Engineering Contradiction:

Improvemode identification accuracyVSAvoidsystem implementation cost

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent merges the Lamb wave generation function, thickness measurement function, and wave mode identification function into a single integrated system using one piezoelectric transducer. The transducer both generates the Lamb wave and measures the thickness through ultrasonic echo, while the processing system combines thickness data with wave propagation characteristics to identify modes, eliminating the need for additional transducers and wiring.

Inventive Principle:

Principle #5Merging (Combining)

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

Enables effective identification of Lamb wave modes and structural health monitoring with reduced costs and complexity, facilitating the detection of anomalies and damage in structures without the need for dual transducer setups.

Implementation Method 1

transmitting a Lamb wave through a structure... using a single piezoelectric transducer

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

measuring an instantaneous thickness of the structure at a predetermined location of the structure during passage of the Lamb wave

Methodology Applied

Scientific EffectUltrasonic time-of-flight measurement: Time of Flight

Data Source

PatentUS8677825B1Identification of lamb wave modes

Publication Date: 2014.03.25 THE BOEING CO

AI summary

A method for identifying Lamb wave modes and structural health monitoring may include transmitting a Lamb wave through a structure for monitoring the structural health of the structure. The method may also include measuring an instantaneous thickness of the structure at a predetermined location of the structure during passage of the Lamb wave at the predetermined location. The method may additionally include identifying a mode of the Lamb wave from the instantaneous thickness of the structure.