The aerospace industry relies on the innovation of parts and materials to improve safety in the air while reducing the cost of manufacturing parts and products. The integrity of every element in an aircraft must meet strict requirements. Detecting defects in these parts is critical. Visual inspections, while technically ‘non-destructive’, aren’t enough to meet the quality control needs of the aerospace industry. Aerospace non-destructive testing is a way of inspecting and evaluating products that are manufactured for the aerospace industry without affecting the end product.
What is Non-Destructive Testing (NDT) and How is it Used in Aerospace?
Since safety is paramount in aviation, researchers use NDT at various stages of a product’s lifecycle. Beginning with the evaluation and selection of suitable manufacturing materials for new equipment and aircraft design to the inspection of aircraft engines and structural components during service, NDT is a valuable process in the aerospace industry.
Aerospace non-destructive testing (NDT) examines the properties of a structure or component to find flaws or defects without causing any damage to the product. The goal is to identify flaws that might compromise the integrity of the product, in order to avoid catastrophic failure when in use.
Unlike NDT, in destructive testing, the material being tested may be scraped away or altered to test the product. This can compromise the product, which renders it unusable. In contrast, NDT offers quick results and doesn’t destroy the part. A significant benefit is that NDT can be used while the part is still in service.
Nadcap is a standardized approach to regulations and requirements. NDT must adhere to those regulations. The techniques applied in NDT are vital to the aerospace industry and are often considered to be the lifeblood of manufacturing parts for the aircraft industry. It’s the way to ensure all products are acceptable and can be safely used instead of being rejected for flaws.
What Is the Importance of Aerospace Non-Destructive Testing?
Non-destructive testing benefits the aerospace industry in multiple ways. The parts of an aircraft go through multiple processes. NDT methods can be applied at different points along the manufacturing process and again when the aircraft is complete. NDT processes can be performed on many different types of materials to check for defects and flaws that could hinder safe operations. Using the different techniques, the aircraft can be checked for flaws that are not visible to the naked eye, whether the product is built into the structure of the aircraft or being manufactured to be put in an aircraft.
Here are 4 important reasons to use NDT testing in the aerospace industry:
1. Accident Prevention
NDT testing methods can be applied at various points through the manufacturing process, which enables manufacturers to find defects and imperfections before the parts are assembled. This reduces the risk of accidents when the materials are fully assembled. NDT techniques can be used throughout the life cycle of parts, to avoid failure.
2. Cost Savings
NDT allows the item that is being tested to survive the testing unharmed. It saves money and resources. NDT testing is a quick evaluation, allowing the assets to move to the next part of the process quicker. If there is a problem with a part, it can be fixed before it becomes a bigger problem that requires more investment in repairs or replacements.
3. Product Reliability
NDT methods ensure products are reliable by identifying problems early in the manufacturing process. They are accurate and predictable. This type of precision testing improves insights into manufacturing because researchers can make a note of what flaws are occurring as the product is being produced. They can be fixed before too many components are produced.
4. Improved Repair Insights
Any flaws and inconsistencies in product design and quality are easily identified through non-destructive testing. With the greater insights gained, manufacturers are able to ensure accurate repairs and if necessary, replacement of parts and components.
6 Nadcap Approved Non-Destructive Testing Methods
There are several NDT methods that allow for data collection on the parts that are manufactured. Some types of NDT methods only work on specific materials, while others can be used for surface inspection or volumetric inspection. These six Nadcap-approved methods are some of the most commonly used NDT techniques.
1. Fluorescent Penetrant Inspection (FPI)
FPI inspection uses a dye or liquid applied to the surface of the product. The product must be clean and dry when the penetrant is applied. The liquid highlights any defects. A trained inspector can recognize problems either by the naked eye or by using specialty lightings, such as UV or fluorescent. This type of NDT is quick and affordable, but it only finds surface defects. This testing method can easily be added to the manufacturing process.
2. Magnetic Particle Inspection (MPI)
MPI detects invisible cracks using electromagnetic currents. This type of NDT testing is only applicable to ferromagnetic materials, such as iron or steel. The part to be tested is magnetized. In the aerospace industry, once the part is magnetized, a liquid that includes ferromagnetic particles is washed over it, or it is submerged. If there is a defect, the pattern of the magnetic particles is disrupted. Inspectors see the problem and know that the part is not perfect. The parts do need to be cleaned before this process, as grease, oil, and dirt can disrupt the patterns.
3. Ultrasonic Testing (UT)
Ultrasonic testing uses high-frequency sound waves to inspect for flaws in the thickness of a material. When the sound waves hit a defect, they bounce off it instead of passing through. Ultrasonic testing gives immediate results and can be performed on one (or both sides) of a material. It’s beneficial when you don’t have access to the other side. Testing results are easily shared, which is another valuable benefit of this type of testing. UT inspection can be used on metals, plastics, and ceramics, even very thin materials that have tiny defects too small to be seen by the naked eye or by other NDT techniques.
Radiation is commonly used in the medical field; however, it is frequently used in aerospace manufacturing to help find flaws in products. Both gamma rays and x-rays travel through many different substances. This allows inspectors to verify for internal defects without damaging and compromising the product. However, radiation can be hazardous to humans, so there are many strict procedures involved to protect all people involved. Radiation is pointed at the item to be inspected. The inspector takes a recording of the item, then analyzes the data to determine if there are any defects.
5. Digital Radiography (RT)
Digital radiography is joining the list of tools available for NDT testing as the technology evolves. It’s actually very similar to x-ray testing and can be set up next to x-ray scanners to take scans using normal lighting conditions. The film does not need to be processed, so it can be a quicker method than conventional radiography. Digital radiography can test and inspect many different components, made from a range of different materials. It’s extremely versatile. It’s gaining ground in the aerospace manufacturing industry as a reliable type of NDT.
6. Eddy Current Testing (ET)
Eddy current testing uses a coil comprised of a conductive wire to create an electromagnetic current. It finds defects and flaws on the surface of a conductive material. Eddy currents are created that are opposite to the probe’s currents, which identifies any defects. It works on both magnetic and non-magnetic surfaces, but it’s not ideal for large surfaces. It’s very sensitive, so it can find very small defects, even on underwater surfaces or high-temperature surfaces. Inspectors do need to understand how to interpret the data correctly because non-relevant data could end up being reported.
Conclusion
The aerospace industry relies on non-destructive testing as a critical aspect of the manufacturing process to maintain the safety of flight-critical components. Using NDT throughout the manufacturing process lets manufacturers test each component for safety and reliability at every stage, from research and development to the final product.
As an aerospace manufacturer, Avior uses proven testing methods to ensure the compliance of its various composites and metallic products. Our aerospace non-destructive testing methods are Nadcap accredited and meet the specifications of aircraft manufacturers such as Boeing, Bombardier, BellFlight and Northrop Grumman. Contact us to find out how we can help you make your aircraft perform better.
