ACFM Crack Evaluation Under Nonmetallic Coatings
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Solution Overview
Problem
Existing alternating current field measurement technologies face challenges in accurately quantifying metal surface cracks under nonmetallic coatings due to lift-off variations and interference noise, leading to inaccurate or missed defect detection.
Innovation Solution
An alternating current field based quantitative evaluation method that compensates for magnetic field signals under arbitrary lift-off using an attenuation coefficient, allowing for accurate crack evaluation by establishing a quantitative relation between crack size and magnetic field signals, and an array detection probe for intuitive defect identification under lift-off jitter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If nonmetallic coating is applied to prolong service life, then service life is extended, but crack detection accuracy deteriorates due to signal attenuation
Solution Approach 1:
The patent applies parameter changes by using an attenuation coefficient to compensate for signal degradation. The method calculates the attenuation coefficient based on coating thickness and applies it to correct the magnetic field signals, thereby restoring detection accuracy while maintaining the protective coating.
2Adaptability or versatility
If calibration is performed under different lift-off heights, then adaptability to varying coating thicknesses is improved, but calibration complexity and error accumulation increase
Solution Approach 1:
The patent transforms the calibration approach by introducing an attenuation coefficient that accounts for coating thickness variations. Instead of performing separate calibrations for different lift-off heights, the method calculates a single attenuation coefficient based on coating parameters and applies it to correct signals across varying conditions, simplifying the calibration process while maintaining adaptability.
3Ease of operation
If traditional ACFM technology is used under nonmetallic coatings, then non-contact detection capability is maintained, but quantitative evaluation accuracy deteriorates due to unknown coating thickness
Solution Approach 1:
The patent introduces an attenuation coefficient as an intermediary parameter that bridges the gap between the probe and the crack. This coefficient accounts for the unknown coating thickness and allows the system to maintain non-contact detection while compensating for the signal attenuation caused by the coating, thereby restoring quantitative evaluation accuracy.
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
The method improves the accuracy and reliability of crack evaluation under nonmetallic coatings and simplifies the computation flow, while the array detection probe enhances defect identification efficiency by distinguishing lift-off jitter from actual defects.
Implementation Method 1
a probe excites induced current on a surface of a workpiece to be tested
Implementation Method 2
The excitation coil is uniformly wound around a U-shaped magnetic core and is configured to generate a uniform induced electromagnetic field on a surface of a workpiece to be tested
Implementation Method 3
A distorted magnetic field signal is picked by a magnetic field sensor in the probe
Data Source
AI summary
Provided are an alternating current field based defect identification method and an array detection probe. The evaluation method includes the following steps: obtaining a magnetic field Bx signal in direction X and a magnetic field Bz signal in direction Z; removing a background magnetic field of each of the magnetic field Bx signal in the direction X and the magnetic field Bz signal in the direction Z, and obtaining a magnetic field Bx1 signal in the direction X and a magnetic field Bz1 signal in the direction Z without background magnetic fields; drawing an array image of the Bx1 signal and an array image of the Bz1 signal; and locating a distortion zone corresponding to disturbance at the same time and position in the array image of the Bx1 signal and the array image of the Bz1 signal.