Home - Education Resources - Science of NDT - Introduction

WHAT IS NONDESTRUCTIVE TESTING (NDT)?

NDT is the use of special equipment and methods to learn something about an object without harming the object. The term nondestructive testing usually implies that a nonliving object, such as a piece of metal, is being evaluated. NDT methods are used to make sure that important parts on airplanes and automobiles and in nuclear power plants are free of defects that could lead to an accident. NDT is also used in many other industries to make sure that parts do not have defects that would make the customer unhappy. The inspection and measurement methods used in the field of NDT are largely based on the scientific principles of physics and chemistry.

Where is NDT used?

Many of the parts that are used in complex systems like aircraft or the Space Shuttle must be inspected to make sure they do not contain defects that my lead to problems or accidents. In the picture at the right an NDT inspector examines a Space Shuttle component to make sure that it has been manufactured properly and that there are no defects present. Even very small defects that can not be seen without magnification (like the one shown in the picture below) can sometimes cause problems and must be found. NDT inspectors use specialized equipment that can find these small defects even if they are buried inside the material.

 

 


 

Some of the equipment and procedures used by NDT personnel are similar to those used in the medical industry. NDT personnel use X-rays to make inspections just like a doctor or a dentist uses X-rays to produce an image of the internal features of your body or teeth. The image in the center below is an X-ray of a person's teeth showing fillings and other dental work. The image below on the right, is an X-ray or what is also called a radiograph of several welds. Flaws can be seen in one of the welds.



Another NDT method that is also used in the medical industry is ultrasound (high frequency sound waves). In a hospital, ultrasound might be used to produce an image of a baby still in the womb or to look at the heart as it pumps away. In the field of NDT, technicians use ultrasound to locate cracks and other flaws inside materials and also to measure the thickness of materials. The man in the picture to the right is using ultrasound to inspect the wall of the ship for areas that may be thinning due to corrosion damage.

An extreme example of how NDT is important to all of us can be seen in a video of an actual airline crash on the next page.