Non-destructive testing ensures quality components without wasting material, but with so many methods available in the quality control space, it can be difficult to identify the strengths and weaknesses of each. To make it easier, this guide will compare two prominent methods: Eddy Current Testing (ECT) and Acoustic Resonance Testing (ART).
While ECT is widely used for detecting surface and near-surface flaws in conductive materials, ART offers comprehensive structural insights through resonance analysis. Read on to discover the differences and determine which method best fits your production needs.
What is Eddy Current Testing (ECT)?
Eddy Current Testing (ECT) is an electromagnetic NDT technique used primarily on conductive materials. An Eddy Current (EC) is a closed loop of induced current circulating in planes perpendicular to a changing magnetic field. EC is induced within a conductor with a coil carrying an alternating current. This phenomenon is explained by Faraday's Law of Electromagnetic Induction, which states that a changing magnetic field creates an electromotive force in a conductor. Any flaws, such as cracks or corrosion, disrupt these currents, produce measurable changes in impedance that signal the presence of defects. ECT is effective for surface and near-surface flaw detection, thickness measurements, material characterization, and can also differentiate alloys and detect heat treatment changes.
Advantages of Eddy Current Testing:
Detects surface and near-surface defects
Measures thickness and material conductivity
Non-contact method, works through coatings or paint, and also underwater
Immediate results
High sensitivity, especially effective for detecting small surface cracks
Compact equipment allows for field testing
Limitations:
Only effective on conductive materials
skin effect: Limited depth penetration (ECT ranges from 1-15mm depending on the frequency of the excitation current, the electrical conductivity, and the magnetic permeability of the specimen.)
Requires skilled operator for calibration and analysis
Susceptible to magnetic permeability changes, making it difficult to test welds in ferromagnetic materials
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 analyzing 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 revolutionized this traditional method through its AI algorithm that significantly enhances the power of 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 anomalies in new production parts. This process is completed in seconds and is not limited by surface type, material, or defect depth. As a result, components that are 3D printed, porous, or have rough surfaces can be objectively assessed.
Advantages of RESONIKS Acoustic Resonance Testing:
Detects a wide range of surface and internal defects (e.g., cracks, porosity, inclusions, laminations, weld defects)
Suitable for various materials, both non-porous and porous
Fast detection, ideal for high-volume production
Easily integrates into automated production lines
Does not require a skilled operator
A cost-effective alternative to traditional NDT methods
Limitations:
Focuses on determining whether a part is good or defective, rather than pinpointing the exact defect location
Requires a batch of reference parts for machine learning, making it less suitable for one-off testing
Conclusion
Choosing the right non-destructive testing method is pivotal to ensuring quality in production. Eddy Current Testing (ECT) and Acoustic Resonance Testing (ART) each shine in their own domains—ECT specializes in detecting surface and near-surface flaws in conductive materials, while ART offers a more versatile solution for identifying defects across a wide range of materials. With RESONIKS’ AI-enhanced ART system, traditional resonance testing is elevated to meet the demands of modern manufacturing. Faster, more precise, and scalable, it’s the perfect match for high-volume, automated production environments.
