An initial experimental study on the influence of beam hardening in X-ray CT for dimensional metrology

X-ray computed tomography (CT) enables the visualisation and dimensional evaluation of both the internal and external geometry of a workpiece, it is therefore well suited for measuring geometric features that are otherwise inaccessible to tactile and optical instruments. Beam hardening is a wellknown physical process that can degrade the quality of CT images and influence edge detection algorithms that define surface points used for dimensional evaluation. The influence of beam hardening on dimensional measurements has yet to be fully characterised; in this work a comparison is made between measurements evaluated with and without beam hardening correction. The results show beam hardening reduces internal dimensions and increases external dimensions; this effect is shown for two different surface determination methods in the absence of scattered radiation