Penetrant testing (PT), also known as fluorescent penetrant inspection (FPI), is a type of liquid penetrant inspection. This is a very common NDT in aerospace for surface applications. This method involves coating components with a liquid dye by spraying, dipping, or brushing.
Fremont CA: Nondestructive testing (NDT) methods are widely used in the aerospace industry. The structural integrity and safety of nearly all components, particularly the most critical ones, must be validated, and NDT plays a significant role in this. Nearly all areas of newly manufactured, serviced, repaired, or overhauled inspections require NDT.
There are numerous NDT methods used in aerospace, with the majority of them falling into two categories: surface and sub-surface. Surface methods are used to detect defects and anomalies on or near the surface. Penetrant inspection and laser shearography are two of the most commonly used surface methods. Subsurface methods are those that detect defects beneath the surface. Radiography and ultrasonic inspections are two of the most commonly used techniques. Some methods, such as ultrasonic and electromagnetic testing, can be used for both surface and subsurface inspections, allowing them to fit into either bucket as needed. Another method, the acoustic resonance method, is a full-body inspection, which means it can evaluate the overall structural integrity of an entire component.
Surface NDT Methods
Penetrant testing (PT), also known as fluorescent penetrant inspection (FPI), is a type of liquid penetrant inspection. This is a very common NDT in aerospace for surface applications. This method involves coating components with a liquid dye by spraying, dipping, or brushing. The parts are then subjected to a dwell time during which the liquid uses capillary action to penetrate defects. Following the expiration of the dwell time, the excess penetrant is removed from the surface, leaving only the dye that has penetrated the defect. The parts are then examined under ultraviolet light after a developer is applied to pull any entrapped penetrant back to the surface. Any visible dye indications are inspected and disposed of. The process concludes with a thorough post-inspection cleaning. There are several cleaning methods available, but the key is to remove all residual dye. PT is a highly effective method that is used by almost every aerospace company or its suppliers.
Sub-surface NDT Methods
Radiography, also known as RT, is a widely used technique. In fact, aerospace manufacturers have been using it for over a century. Radiography is the use of X-rays or gamma rays to inspect products for flaws and verify dimensions. X-rays are directed at a component or an area of interest within a component after all safety precautions have been considered and implemented. As the X-rays pass through the target, some of them are absorbed by the denser material areas, while more X-rays pass through the target in the less dense areas. The image contrast is provided by the absorption and varying amount of X-rays passing through the target. The most common methods for capturing X-rays are film, imaging plates, and digital detectors. Most people are familiar with this NDT because they have seen the results of an X-ray at their doctor's office or an emergency room. Almost every aerospace company that manufactures any component uses RT.