Eddy Current Probe for Formed Steel Tube End Inspection

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Solution Overview

Problem

Existing methods for inspecting high-strength and ultra-high-strength steel tubular products for defects in their formed end sections are time-consuming, costly, and material-intensive, particularly when both inner and outer walls need to be tested, and current non-destructive methods like eddy current testing are limited to electrically conductive materials.

Innovation Solution

A method and test probe using eddy current sensors simultaneously inspect both the inner and outer walls of formed end sections of steel tubes, with multiple sensors on arms and/or an inner part, allowing for simultaneous testing and shared evaluation electronics, and the probe is designed for axial and rotational movement to cover the entire surface.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If ultrasonic testing with liquid coupling medium is used, then defect detection capability is improved, but testing time and energy expenditure increase due to cleaning and drying requirements

Engineering Contradiction:
Improvedefect detection capabilityVSAvoidtesting time
Core Design Contradiction:
ReliabilityVSLoss of time

Solution Approach 1:

The patent extracts and eliminates the liquid coupling medium from the testing process by using eddy current testing instead of ultrasonic testing. This removes the need for cleaning and drying steps, directly resolving the contradiction between defect detection capability and testing time/energy expenditure.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces the mechanical ultrasonic testing system with an electromagnetic eddy current testing system. This substitution eliminates the need for liquid coupling medium and associated post-testing processing, thereby reducing testing time and energy expenditure while maintaining defect detection capability.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

2Reliability

If ultrasonic testing with liquid coupling medium is used, then defect detection capability is improved, but corrosion of the tubular product occurs

Engineering Contradiction:
Improvedefect detection capabilityVSAvoidcorrosion
Core Design Contradiction:
ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent removes the liquid coupling medium from the testing process by employing eddy current testing. This extraction eliminates the source of corrosion, resolving the contradiction between defect detection capability and protection of the tubular product from corrosion.

Inventive Principle:
Principle #2Taking out (Extraction)

Solution Approach 2:

The patent substitutes electromagnetic eddy current testing for mechanical ultrasonic testing with liquid medium. This replacement eliminates the corrosive liquid coupling medium while preserving defect detection capability, thereby preventing corrosion of the tubular product.

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If separate testing of inner and outer walls is performed, then comprehensive defect inspection is achieved, but testing time and equipment requirements increase

Engineering Contradiction:
Improvecomprehensive defect inspectionVSAvoidtesting efficiency
Core Design Contradiction:
ReliabilityVSProductivity

Solution Approach 1:

The patent combines the testing of inner and outer walls into a single integrated eddy current testing process. By using eddy current sensors that can detect defects in both walls simultaneously, the patent achieves comprehensive defect inspection while improving testing efficiency and reducing equipment requirements.

Inventive Principle:
Principle #5Merging (Combining)

Solution Approach 2:

The patent employs eddy current testing technology that serves multiple functions - it can inspect both the inner and outer walls of the tubular product using the same testing system and methodology. This multi-functionality resolves the contradiction between comprehensive inspection and testing efficiency.

Inventive Principle:
Principle #6Universality (Multi-functionality)

4Productivity

If eddy current testing is used, then testing time is reduced and corrosion is avoided, but the method is limited to electrically conductive materials only

Engineering Contradiction:
Improvetesting efficiencyVSAvoidmaterial applicability
Core Design Contradiction:
ProductivityVSAdaptability or versatility

Solution Approach 1:

The patent applies eddy current testing to steel tubular products, which are electrically conductive. While the method inherently limits applicability to conductive materials, the patent successfully adapts the technique to its specific application domain (steel airbag tubes), achieving high testing efficiency without corrosion while working within the material constraints.

Inventive Principle:
Principle #26Copying

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 approach reduces testing time by at least half, eliminates the need for separate test benches, minimizes equipment, and enhances defect detection reliability and resolution, while avoiding corrosion and additional processing steps.

Implementation Method 1

Eddy current testing utilizes the effect that impurities and damage in an electrically conductive material also have a different conductivity or permeability than the material itself. The measurement signal depends on the three parameters of conductivity, permeability, and the distance between the detector and the material surface, allowing for the detection of surface damage to the object being tested.

Methodology Applied
Scientific EffectEddy current: Eddy Currents

Data Source

PatentEP4036567B1Method for manufacturing and testing a high-strength steel pipe product and test probe
Publication Date: 2026.03.11 BENTELER STEEL TUBE GMBH & CO KG
  • EP4036567B1 patent drawingFigure 1
  • EP4036567B1 patent drawingFigure 2
  • EP4036567B1 patent drawingFigure 3

AI summary

The invention relates to a method for manufacturing and testing a high-strength steel tube product (1) comprising the following steps: a) providing a steel tube, b) forming the steel tube into the tube product (1), wherein the steel tube is formed at least in one of its end regions (10-1, 10-2), c) testing the inner wall (7) and the outer wall (8) of at least one formed end region (10-1, 10-2) of the tube product (1) for defects using a test probe (9) adapted to at least one formed end region (10-1, 10-2), which has at least one eddy current sensor (12) for testing the inner wall (7) and at least one eddy current sensor (13, 14, 15) for testing the outer wall (8) of the at least one formed end region (10-1, 10-2) of the tube product, wherein several sensors (13, 14, 15) are attached to at least one Arm (2, 3) and/or several sensors (12) are provided on an inner part (4).