Halbach Magnet Assembly for Thermal-Stable EMAT Sensitivity

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

The reliability and life of Halbach array magnets used in electromagnetic ultrasonic sensors are compromised when exposed to high temperatures, as the magnets expand and contract, shifting their position and affecting the sensor's sensitivity.

Innovation Solution

A Halbach array magnet configuration that includes a magnet unit with a Halbach array arrangement, a non-magnetic fixing jig to secure the magnets, and a magnetic yoke on the opposite side of the biased magnetic field, allowing for reliable fixation without adhesives or frames.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If magnets are arranged in a Halbach array for electromagnetic ultrasonic measurement, then magnetic field strength is concentrated on one side and sensitivity is improved, but the magnets expand and contract due to repeated heat load causing position shifts and reliability degradation

Engineering Contradiction:

ImprovesensitivityVSAvoidreliability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The magnet array is divided into multiple individual magnets (typically 4-8 magnets) arranged in a specific Halbach pattern, where each magnet can be independently fixed. This segmentation allows for precise positioning of each magnet while maintaining the overall magnetic field concentration effect, preventing position shifts under thermal load.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the magnet array are fixed with different strategies - magnets at corners or edges may use different fixing methods compared to central magnets. The fixing structure provides localized support where thermal expansion would cause the most displacement, while allowing other regions to maintain their magnetic field optimization.

Inventive Principle:

Principle #3Local quality

2Measurement precision

If magnets are brought close to the measurement target to improve sensitivity, then sensitivity increases, but the sensor cannot be brought close to high-temperature targets or moving targets

Engineering Contradiction:

ImprovesensitivityVSAvoidtemperature resistance

Core Design Contradiction:

Measurement precisionVSTemperature

Solution Approach 1:

A non-contact measurement approach is used where the electromagnetic ultrasonic sensor measures defects in the magnet array itself without physical contact. This intermediary measurement method allows the sensor to remain at a safe distance from high-temperature targets while still obtaining sensitive defect detection data.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Measurement precision

If conventional ultrasonic probes are used for measurement, then measurement sensitivity is high, but contact medium such as water must be used which limits application to high temperature or moving objects

Engineering Contradiction:

ImprovesensitivityVSAvoidapplication range

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The conventional mechanical contact-based ultrasonic measurement system is replaced with a non-contact electromagnetic ultrasonic measurement system. This substitution eliminates the need for water coupling medium while maintaining measurement capability, enabling application to high-temperature and moving objects.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The measurement approach changes from mechanical contact (requiring water coupling) to electromagnetic interaction (non-contact). This parameter change in the measurement mechanism fundamentally removes the limitation of requiring water medium, expanding applicability to high-temperature and moving target scenarios.

Inventive Principle:

Principle #35Parameter changes

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

This configuration ensures the reliability and extended life of the Halbach array magnet even under repeated heat loads or in water-cooling environments, maintaining sensitivity and preventing detachment issues.

Implementation Method 1

a technique called a Halbach array in which a main magnetic pole and an auxiliary magnetic pole are arranged so as to be orthogonal to each other, and a magnetic field is concentrated on one side (measurement target side) to improve magnetic field strength

Methodology Applied

Scientific EffectHalbach array: Halbach Array

Implementation Method 2

Since each magnet expands and/or contracts due to repeated heat load, and a position of each of the magnets arranged in a row and bonded to each other is shifted

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS20250146977A1Halbach array magnet, electromagnetic ultrasonic sensor, defect measurement apparatus, defect measurement method, metal material manufacturing method, metal material quality control method, metal material manufacturing facility, solidification position measurement apparatus, solidification position measurement method, and casting facility

Publication Date: 2025.05.08 JFE STEEL CORP

AI summary

A Halbach array magnet includes: a magnet unit in which a plurality of magnets is arranged in a Halbach array; a fixing jig that is one or a plurality of non-magnetic materials, the fixing jig being configured to at least fix each of the magnets of the magnet unit; and a yoke that is a magnetic material and is provided on a different side of biased magnetic field formed by the magnet unit.