Making internal structures visible – penetrative and precise
Radiographic testing is based on the different transparency of materials to ionising radiation. The component is penetrated using X-ray or gamma radiation. The radiation is attenuated to different degrees depending on material density, material thickness and internal irregularities.
Behind the component is a detector – for example film, a digital flat-panel detector or a storage phosphor system – that records the transmitted residual radiation. Regions of higher material density absorb more radiation and appear brighter in the image, while regions of lower density or voids are shown darker.
If a defect such as shrinkage, porosity or lack of fusion is present inside the component, it locally changes radiation absorption. This produces a contrast difference in the recorded image, allowing conclusions on the position, size and shape of the irregularity.
Image evaluation is performed using defined evaluation scales, reference blocks or contractually agreed criteria. Depending on the inspection task, different radiation sources, energy ranges and exposure parameters are used to ensure adequate image quality and inspection reliability.
Radiographic testing thus enables two-dimensional imaging of the internal component condition and is an established volumetric inspection method in particular for castings, welds and complex geometries.
