Evaluation of Depth Size Based on Layered Magnetization by Double-Sided Scanning for Internal Defects

Area of Science:

• Materials Science
• Non-Destructive Testing
• Electromagnetism

Background:

• Accurate defect depth evaluation is crucial for preventing harm and economic losses, particularly for internal defects in ferromagnetic materials.
• Magnetic Permeability Perturbation Testing (MPPT) is effective for thick-walled steel pipes, but determining defect depth from single time-domain signals is challenging.

Purpose of the Study:

• To develop a novel magnetic method for precisely quantifying internal defect depths in ferromagnetic materials.
• To overcome the limitations of traditional MPPT in defect depth assessment.

Main Methods:

• Investigated magnetization layering in ferromagnetic materials under unsaturated magnetizing fields.
• Utilized step magnetization to achieve different magnetization depths.
• Employed finite element simulations to establish relationships between magnetization currents and depths.
• Applied a double-sided scan technique to localize defect boundaries.

Main Results:

• Successfully established magnetization characteristic current-depth relationships via simulations.
• Demonstrated the capability to detect spatial properties of layered magnetization.
• Experimentally evaluated defects with a 2 mm depth size.
• Achieved a maximum relative error of 5% in experimental evaluations.

Conclusions:

• The proposed method enables accurate determination of internal defect depth sizes in ferromagnetic materials.
• Layered magnetization and double-sided scanning effectively localize defect boundaries.
• This technique offers a significant improvement for defect evaluation in thick-walled steel pipes.