EMAT for Bending Vibration in Rod Members

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Solution Overview

Problem

Existing electromagnetic acoustic transducers (EMATs) are unable to measure or generate bending vibrations in rod members, limiting their application to axial shear waves, torsional waves, longitudinal waves, and transverse waves in plate members.

Innovation Solution

An EMAT design featuring a non-metal main body with a hollow portion, anti-symmetric magnetic fields generated by pairs of magnets, and a coil wound around the outer surface, allowing for the measurement and generation of bending vibrations in rod members by inducing eddy currents and Lorentz's force.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If conventional EMAT design is used, then axial shear waves, torsional waves, longitudinal waves, and transverse waves in plate members can be measured, but bending vibrations in rod members cannot be measured

Engineering Contradiction:

Improvemeasurement capabilityVSAvoidbending vibration measurement

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent applies asymmetry by arranging magnets in an asymmetric configuration around the rod member, with different numbers of magnets on different sides (e.g., two magnets on one side, one magnet on the other side). This asymmetric magnetic field distribution creates a net force that generates bending vibrations, enabling the measurement of bending modes that cannot be detected by symmetric conventional EMAT designs.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent transitions from measuring only axial and transverse waves in conventional EMATs to measuring bending vibrations by introducing a new dimension of measurement capability. The asymmetric magnet arrangement creates out-of-plane forces that generate bending modes, expanding the measurement capability into a previously inaccessible dimensional space of vibration modes.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Device complexity

If symmetric magnet arrangement is used, then simple structure is maintained, but bending vibration generation is not achieved

Engineering Contradiction:

Improvemagnet arrangementVSAvoidbending vibration measurement capability

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

The patent deliberately introduces asymmetry in the magnet arrangement to achieve bending vibration generation. By positioning magnets asymmetrically (different numbers, different positions, or different polarities on different sides), the system breaks the symmetry that would otherwise cancel out bending forces, thereby enabling bending mode excitation and measurement while maintaining a relatively simple overall structure.

Inventive Principle:

Principle #4Asymmetry

3Reliability

If non-contact measurement method is used, then material damage is prevented, but bending vibration measurement capability is lost

Engineering Contradiction:

Improvenon-destructive testingVSAvoidbending vibration measurement

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent maintains non-contact measurement by using electromagnetic forces (Lorentz force from interacting magnetic fields and eddy currents) to generate and detect bending vibrations, replacing mechanical contact methods. This substitution preserves the non-destructive nature of the testing while enabling bending vibration measurement through the asymmetric electromagnetic force distribution.

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

Enables the measurement and generation of bending vibrations in rod members, expanding the applicability of EMATs and providing insights into modal testing through frequency response functions and mode shapes, thereby aiding in the design of machines to prevent vibration-induced damage.

Implementation Method 1

a magnetic field generation portion generating two magnetic fields parallel to a lengthwise direction of the rod member and in opposite directions to each other

Methodology Applied

Scientific EffectMagnetic field: Magnetic Field

Implementation Method 2

converting wave energy transferred to the rod member into electric energy or transferring a wave to the rod member by inducing a change in the magnetic field

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 3

EMATs refer to devices which can operate as a non-contact sensor and an actuator using Lorentz's force

Methodology Applied

Scientific EffectLorentz's force: Lorentz Force

Implementation Method 4

converting wave energy transferred to the rod member into electric energy

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS7742616B2Electromagnetic acoustic transducer for generating and measuring bending vibration in rod member using anti-symmetric magnetic field structure

Publication Date: 2010.06.22 SEOUL NATIONAL UNIVERSITY R&DB FOUNDATION

AI summary

Provided is an electromagnetic acoustic transducer including a main body formed of a non-metal material and having a hollow portion, a magnetic field generation portion generating two magnetic fields parallel to a lengthwise direction of the rod member and in opposite directions to each other, at both sides of the rod member that is inserted in the hollow portion of the main body, and a coil wound around an outer circumferential surface of the main body.