Inductive Crack Depth Measurement via Time-Range Segmentation
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Solution Overview
Problem
Current inductive techniques for crack detection in metallic materials face challenges in accurately determining crack depth due to influences from various parameters other than crack depth, such as distance, magnetic oxide, material characteristics, and surface irregularities, making it difficult to distinguish crack depth from other changes in the magnetic field, especially on irregular surfaces.
Innovation Solution
A method involving a transmitter coil and a receiver coil to generate and detect a magnetic field, with controlled current magnitudes and specific time ranges to isolate crack depth measurements by determining characteristic values within these ranges, minimizing the impact of other process parameters, and optionally determining crack length using additional characteristic values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If inductive techniques are used for crack detection, then crack depth can be measured, but other process parameters (distance, magnetic oxide, material characteristics, surface irregularities) also influence the magnetic field changes, making it difficult to distinguish crack depth from other variations
Solution Approach 1:
The measurement process is segmented into multiple time ranges (first time range for shallow depth, second time range for deeper depth). By separating the measurement into distinct temporal segments, the system can isolate the magnetic field changes corresponding to different depth ranges, thereby distinguishing crack depth measurements from influences of other parameters like distance and surface irregularities that affect the overall field differently.
Solution Approach 2:
The patent introduces a time dimension to the measurement process. Instead of relying solely on spatial proximity to distinguish crack depth from other factors, the system uses temporal separation by measuring at different time ranges. This additional time dimension allows the system to resolve ambiguities between crack depth and other parameter influences, as each parameter affects the magnetic field at different rates and times.
2Adaptability or versatility
If inductive techniques are used for crack inspection, then crack detection is possible, but it is difficult to use for irregular surfaces such as casted metallic surfaces due to varying parameters
Solution Approach 1:
The system dynamically adjusts the current magnitude in the transmitter coil over time. By varying the current magnitude through different time ranges, the system can adapt to different surface conditions and crack depths. This dynamic approach allows the same inductive system to handle both regular and irregular surfaces effectively, as the time-varying current compensates for variations in surface geometry and material properties.
3Ease of manufacture
If optical methods are used for crack detection, then surface cracks can be detected, but cracks not visible on the surface cannot be detected and color variations may be misinterpreted as cracks
Solution Approach 1:
The patent replaces optical inspection with electromagnetic induction-based inspection. Instead of using light and cameras to detect surface cracks, the system uses a transmitter coil to generate a magnetic field that penetrates the material, and a receiver coil to detect changes in the magnetic field caused by cracks. This substitution eliminates the limitations of optical methods, allowing detection of subsurface cracks and eliminating misinterpretation of color variations, while maintaining inspection simplicity through automated electromagnetic field measurement.
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 allows for reliable and accurate crack depth measurements independent of other process parameters, enabling effective crack detection on both smooth and irregular metallic surfaces, including those in extreme conditions like casting processes.
Implementation Method 1
a current is induced in the metallic material, e.g. a slab or a metal sheet, by means of a time-varying magnetic field generated by a transmitter coil fed with a likewise time-varying current
Implementation Method 2
The change in the magnetic field is measured by a receiver coil, whereby it can be determined that a crack is present in the inspected surface portion of the metallic material
Data Source
AI summary
A method of determining a crack depth of a crack in a metallic material including the steps: feeding a current with a first magnitude to a transmitter coil for generating a magnetic field in the metallic material; controlling the current such that it obtains a second magnitude when the magnetic field is estimated to have penetrated deeper than a deepest crack depth desired to be measured in the metallic material; detecting the magnetic field by means of a receiver coil; determining a first characteristic value of the signal in a first time range; determining a second characteristic value of the signal in a second time range after the first time range; and determining a possible presence of a crack and its crack depth based on the first characteristic value and the second characteristic value.