British Institute of Non-Destructive Testing

'Non-destructive testing (NDT) is the branch of engineering concerned with all methods of detecting and evaluating flaws in materials. Flaws can affect the serviceability of the material or structure, so NDT is important in guaranteeing safe operation as well as in quality control and assessing plant life. The flaws may be cracks or inclusions in welds and castings, or variations in structural properties which can lead to loss of strength or failure in service ... The essential feature of NDT is that the test process itself produces no deleterious effects on the material or structure under test.'