Visual Testing (VT)
Visual testing is the most commonly used test method in industry. Because most test methods require that the operator look at the surface of the part being inspected, visual inspection is inherent in most of the other test methods. As the name implies, VT involves the visual observation of the surface of a test object to evaluate the presence of surface discontinuities.
It is considered as the oldest and cheapest NDT method. It is also considered as one of the most important NDT method and applicable at all stages of construction or manufacturing sequence. In inspection of any engineering component, if visual inspection alone is found to be sufficient to reveal the required information necessary for decision making, then other NDT methods may no longer considered necessary.