Magneto-Mechanical Coupling Modeling and Full-Cycle Characterization of V-Shaped Crack Evolution in Q345 Steel Using...

Area of Science:

• Materials Science
• Non-Destructive Evaluation
• Magnetism

Background:

• Metal magnetic memory (MMM) is a non-destructive evaluation technique for detecting defects in ferromagnetic materials.
• Existing magneto-mechanical coupling models struggle to accurately describe the behavior of small cracks throughout their lifecycle.
• Characterizing crack evolution is crucial for assessing structural integrity and predicting fatigue life.

Purpose of the Study:

• To develop and validate a novel magnetic dipole model for analyzing V-shaped cracks in ferromagnetic materials.
• To investigate the magneto-mechanical coupling mechanism and magnetic signal evolution during crack propagation.
• To establish a quantitative correlation between MMM signals and crack growth for improved damage assessment.

Main Methods:

• Development of a decomposed magnetic dipole model for V-shaped cracks.
• Theoretical derivation and finite element simulation of magneto-mechanical coupling.
• In situ three-point bending tests on Q345 steel to validate the model and observe crack propagation.

Main Results:

• The MMM normal component shows peak-peak features at crack tips, while the tangential component exhibits a single peak.
• Two critical signal mutations were identified at approximately 100 μm and 3000 μm crack lengths, indicating micro-meso and meso-macro transitions.
• The proposed model achieved relative errors of 15.2% for Hx and 17.6% for Hy, demonstrating its validity.

Conclusions:

• The study successfully correlates MMM signals with the full lifecycle of crack growth in ferromagnetic materials.
• The developed model provides a more computationally efficient and accurate method for characterizing crack evolution compared to existing models.
• This research supports enhanced damage assessment and fatigue life prediction for engineering structures utilizing ferromagnetic materials.