Choosing the Right NDT Equipment for Aluminum Welding in the Aerospace Industry

Nondestructive Testing (NDT) is a must for aluminum welding in any industry, but especially for aerospace. Cracks, loose components, and corrosion can be costly if they go undetected—both in terms of money and lives. 

As such, it is crucial to use the right NDT equipment. There is a lot of equipment out there, varying in degrees of expense and efficacy. Every organization has to find the balance that works for them, and that includes factoring in the cost of not catching every flaw. 

Choosing NDT equipment for aluminum welding is a big decision in the aerospace industry. Here’s how aerospace organizations can determine what technology to employ. 

Testing Areas in Aerospace

Nondestructive testing is a vital part of the aerospace industry. This is one of the more heavily-regulated industries in the world, with civilian, commercial, and military aircraft being subjected to the strictest possible welding standards. 

Every aerospace engineer and mechanic wants to exceed those standards, knowing how much rides on accurate testing. That’s why technicians test all aluminum welds in turbines, machinery, and on the aircrafts themselves. 

Some of the main areas of testing include:

• Slag inclusion
• Gap detection 
• Porosity
• Strength

In aluminum welding, these are all important for determining if the weld is secure and reliable. Friction stir welding (FSW) and other techniques used to fabricate aluminum structures can produce flaws not found in other types of materials. While some NDT techniques can easily detect some of them, the level of importance demands comprehensive testing. 

Types of NDT Methods for Aluminum Welding

When probing aluminum welding, technicians should use methods and solutions that can capture the most potential damage in the shortest amount of time. Here are some common types of NDT techniques for inspecting aluminum welding:

Visual Testing

Visual testing involves more than just eyeballing a weld; there are manual tools for quickly testing a weld. While there is much a skilled inspector can judge from this simple test, there is also a lot that is impossible to see, including subsurface cracks. 

Liquid Penetrant 

With liquid penetrant testing, an engineer isolates a section of a weld and runs liquid over and through it. If the weld holds the liquid without it running through, then the weld is considered secure. This is easy in theory, and in practice at a small scale, but the effort of isolating and testing can be unwieldy as you scale up. In addition to this organizational flaw, this test also has trouble catching internal hollow spots that can quickly come to the surface in the field. 

Radiography

There are many types of radiography that vary in power, speed, and comprehensiveness. These include conventional radiography, computed radiography, close proximity radiography, and computed tomography. While all of these are sophisticated, they can be operationally cumbersome. Skilled technicians have to operate the equipment while wearing protective equipment, and there can’t be anyone else around them. 

Magnetic Particle Testing

With both “wet” and “dry” tests, magnetic particle testing (MPT) is a versatile and intuitive test for ferrous materials, including aluminum alloys. In this technique, the material is magnetized and sprayed with iron particles. If there is a crack or some other flaw, the particles will gather around it, giving a clear look at the flaw. This test is effective at surface-level cracks but has to be done before painting and is challenging to scale up. 

Eddy Current Testing

Eddy Current Testing (ECT) and, more specifically, Eddy Current Array (ECA) is one of the more effective tests for detecting cracks in aluminum, especially in multilayer aluminum jobs. For this reason, ECA is popular in the aerospace industry. ECA is a fast and easy-to-use solution for detecting surface-level flaws, especially if the equipment is handheld. Like MPT, this method uses magnetic fields to detect anomalies. Unlike MPT, though, eddy current can probe through paint and it creates a true digital “map” of the surface, letting analysts spot flaws quickly and comprehensively. 

ECT is primarily useful for surface-level flaws and cracks. It is fast and efficient but would have to be paired with other tests to get deeper below the surface. 

Ultrasonic Testing

Phased array ultrasonic testing (PAUT) is ideal for testing aluminum and friction stir welds in the aerospace industry. This technique is quick and easy to use; an operator simply runs a handheld device over the surface, sending ultrasonic waves throughout the entire component. The complete hardware/software system collects and interprets the diffusion and retraction of the waves, painting a picture on the screen. The technician can see both surface and internal flaws. 

With the right ultrasonic testing (UT) system, technicians can potentially achieve a comprehensive look at any flaws in the welding. The handheld capability is also ideal for the strange angles and rounded surfaces typically found in welding. 

Choosing NDT Equipment in the Aerospace Industry 

Every organization has to make decisions about their NDT equipment based on a number of considerations, including balancing the cost of the equipment, its efficacy, and the costs of mistakes. 

Some industries can afford minor cracks and flaws, and thus the cost of mistakes isn’t high. That’s not the case in the aerospace industry. Lives are held in the air, and mistakes can cost more than money. For that reason, it’s worth investing in high quality NDT equipment that can detect every flaw. 

Zetec is a major provider of nondestructive testing equipment for aluminum welding in aerospace and a variety of industries across the world. Contact us today to get the best NDT solutions for your aluminum welding testing operations.