Non-destructive testing (NDT) ensures part integrity without material waste. Magnetic Particle Inspection (MPI) and Acoustic Resonance Testing (ART) are two NDT methods both with unique advantages and disadvantages. MPI is effective in detecting surface and near-surface defects, while ART uses resonance to assess the entire component. In this article, we will compare the features of MPI and ART to help you determine the best fit for your testing requirements.
What is Magnetic Particle Inspection (MPI)?
Magnetic Particle Inspection (MPI) is an NDT technique used to detect surface and shallow subsurface defects in ferromagnetic materials. The process involves magnetising the component and applying fine ferrous particles, either suspended in a solution or dry, which accumulate at any areas of discontinuity such as cracks. These particles either fluoresce under UV light or are visible to the naked eye, depending on the type of particles used. The method is widely used for inspecting welds, castings, and other critical components.
Advantages of Magnetic Particle Inspection:
Suitable for large components and complex shapes
Can detect very small surface and near-surface discontinuities
Immediate results, allowing for real-time inspection
Applicable on both raw materials and finished parts
Limitations:
Only works on ferromagnetic materials (e.g., iron, steel)
Preparation and cleaning of surfaces required
Use of messy, fine particles and complex equipment
Cannot detect deeper subsurface defects
Requires Skilled Operator
What is Acoustic Resonance Testing (ART)?
Acoustic Resonance Testing is an NDT method that assesses structural integrity by measuring the resonance frequencies of a component. Every material possesses unique resonance frequencies based on its material and geometry. By exciting components through mechanical impact or vibration and analysing its acoustic response, ART can detect various defects, including cracks, inclusions, and porosity. Traditionally, it is performed with a hammer and human operator who listens to the sound upon impact. The operator then uses their trained ear to determine if the part is defective.
RESONIKS has revloutionised this traditional method through its AI algorithm that significantly enhances the power of the Acoustic Resonance Testing. Leveraging advanced machine learning models, RESONIKS precisely indexes the resonant signatures of defect-free parts during the training phase. The AI model then analyzes the data to create a sensitive model capable of detecting even the slightest of anomalies in new production parts. This process is completed in seconds, and is not limited to surface type, material type, or depth. Therefore, any parts that are 3D printed, porous, or have rough surfaces can be objectively assessed.
Advantages of RESONIKS Acoustic Resonance Testing:
Detects a large variety of surface and bulk defects (e.g. cracks, porosity, inclusions, laminations and weld defects)
Can be used with variety materials, non-porous and porous
Quickly identifies defects making it ideal for high-volume production
Ability to easily integrated (automated) into the production line
Doesn’t require a skilled operator
A low cost alternative to traditional NDT methods
Limitations:
Focuses on identifying whether a part is good or bad, rather than locating the exact location of the defect
Not suitable for one-off testing as a batch of reference parts are required for machine learning
Conclusion
Magnetic Particle Inspection and Acoustic Resonance Testing each offer powerful NDT capabilities, with MPI excelling in detecting surface and near-surface defects in ferromagnetic materials, and ART providing broader insights into material integrity, particularly for subsurface flaws. For companies seeking to modernize their NDT processes, RESONIKS’ AI-driven ART can deliver fast, reliable, and automated testing solutions tailored for a wide variety of materials and production scales.
