Nondestructive Testing (NDT) encompasses a various group of test and inspection processes designed to detect surface and sub-surface defects or inconsistencies in testing samples, without affecting the future operating performance of the inspected parts. Since NDT does not permanently alter the article being inspected, it is a highly valuable technique that can save both money and time in product evaluation, troubleshooting, and research. The six most frequently used NDT methods are magnetic-particle, eddy-current, radiographic, visual testing, liquid penetrant, and ultrasonic. NDT labs most often test for forensic engineering, mechanical engineering, petroleum engineering, electrical engineering, civil engineering, systems engineering, aeronautical engineering, medicine, and art.