Using Eddy Current NDT for Subsurface Crack Detection in Multilayer Aluminum with Fasteners

The inspection of multi-layered aluminum requires a precise nondestructive testing (NDT) method that conforms to the geometry of the tested object. Aluminum is highly susceptible to defects within the aviation industry; as such, NDT analysts need a specialized approach that fosters a comprehensive analytical process, especially for minor aberrations that are normally harder to read. In this case, eddy current technology is an ideal choice for testing aluminum surfaces with fasteners. Eddy current testing is a fast, accurate, chemical-free method for detecting a variety of surface and subsurface defects, including cracks, corrosion, and heat damage. Today, it’s perhaps the most effective and cost-efficient nondestructive testing technology for inspecting skins, stringers, frames, rivet holes, tubing, and other ferrous and non-ferrous components in aerospace and aviation.

Overall, eddy current inspections are conducive to the inspection of flat aluminum materials. Subsurface crack detection using Eddy Current Array (ECA) is unrivaled given the cutting-edge signal quality and advanced probing measures that surpass other NDT measures. However, it’s not enough to apply ECA measures; technicians also need impeccable equipment to achieve the most reliable data.

Choosing The Right ECT Equipment for Subsurface Crack Detection

When choosing the right ECT equipment for detecting subsurface cracks in fastener-based aluminum, choose an array capable instrument that’s handheld and allows you to move faster throughout the inspection process. A portable ECA solution affords analysts optimized probing on multi-layered aluminum, with all the data displayed on a basic interface backed by state-of-the-art software. A handheld ECA instrument should come with the following features:

• Simple graphic displays that highlight flaws with glaring prominence
• Little to no arm fatigue during testing
• Long battery life that easily sustains equipment throughout the testing process
• Zoom-in features to further assess all flaws indicated

Other NDT methods, such as standard ECT, don’t have the same capability and versatility as ECA. With more traditional eddy current methods, analysts might need to scan each fastener or row of fasteners individually, which can be extremely time-consuming. With an advanced low frequency flexible array probe and a portable eddy current array instrument, analysts can scan multiple rows of fasteners at the same time for a fast inspection.

Eddy Current Array Capabilities

When searching for ECT equipment, choose instruments and probes that have an array functionality. An array probe can enhance the probability of detection, and it is one of the best methods that can detect cracks around fasteners and other parts of multi-layer aluminum. When testing a complex aluminum piece with fasteners, the best type of array probe to use is a low-frequency, flexible probe that can inspect thicker plates. 

However, array probing can come with a certain set of universal benefits that will improve the testing of aluminum structures, such as:

• Enhanced position indicators that assist during the alignment process and ensure that an entire area is covered during testing
• Pretesting calibrations that save time, including the ability to customize filters when necessary
• Flexible multi-coil array designs that help to further customize the probe to the contortions of the surface, eliminating the need to frequently adjust the probe during the inspection. 

Example: Analysts might use pencil probes to analyze each fastener, but the ECA can glide over the entire fastener. This enables analysts to catch any flaws and save time.

An ECA probe can scan multiplefastener rows at a time with a single pass and can conform to the fastener holes and any unconventional area at the surface level. As a result, users will get a well-rounded inspection campaign that covers just about any form of cracking, regardless of orientation.

ECA can reduce inspection times by as much as 95 percent when compared to an approach that includes standard pencil probes. It’s also more suited to the testing of complicated geometrical patterns than standard fastener probing, such as sliding probes.

Efficient Subsurface Crack Detection with ECA

ECT is one of the best methods for the detection of cracking on aluminum welds, but ECA provides greater depth into sequestered cracking below the surface. To achieve optimal results, buy an ECA solution from a trustworthy NDT provider that invests in quality software and enhanced ECA instruments. Then, choose the right array probe for aluminum welds with fasteners, such as a low-frequency, multi-coil array flex probe. Overall, choose equipment that has powerful capabilities, high signal to noise ratios and user friendly interfaces.

The efficiencies associated with ECA practices allow technicians to focus on finding flaws instead of diverting energy into lengthy setup times or frequent probe adjustments that elongate the testing procedure and hamper the ability to detect abnormalities.

Zetec is a major provider of advanced ECT equipment as well as ultrasonic solutions. Contact us today to learn more about ECT testing on multi-layer aluminum materials with fasteners, including our custom inspection options for your NDT needs.