Numerical Simulation of X-Ray Scattering Processes during Radiographic Inspection of Materials
(2006)
Abstract A technique for numerical simulation of the processes of forming X-ray radiography images of complex multicomponent objects with allowance for the penetrating-radiation absorption and scattering processes is proposed. The technique proposed is based on an efficient description of complex 3D objects with piecewise-homogeneous structures and uses precisely specified shells separating homogeneous components of an object. Being combined with a developed version of the Monte Carlo method, this approach yields an efficient computational apparatus for analyzing the regularities of the formation of radiographic images of objects internal structures. This apparatus is intended for state-of-the-art multiprocessor computing systems. Having been obtained via the technique developed, the results of the numerical analysis of the effect of different mechanisms of interaction between photons and matter (including coherent and incoherent scattering with allowance for bonds of electrons in atoms) on the formed radiographic image of the objects internal structure are discussed. The advantage of the described technique over the known MCNP program complex is shown.
The computer simulation of radiography is applicable for different purposes in NDT such as for the qualification of NDT systems, the optimization of system parameters, feasibility analysis, model-based data interpretation, education and training of NDT/NDE personnel, and others. Within the framework of the European project PICASSO simulators will be adapted to support reliability assessments of NDT tasks. The radiographic simulator aRTist developed by BAM is well suited for this task. It combines analytical modelling of the RT inspection process with the CAD-orientated object description applicable to various industrial sectors such as power generation, aerospace, railways and others. The analytic model includes the description of the radiation source, the interaction of Radiation
with the material of the part, and the detection process with special focus to DIR. To support reliability estimations the simulation tool is completed by a tool for probability of detection (POD) estimation. It consists of a user interface for planning automatic simulation runs with varying parameters, specifically defect variations.
Further, an automatic image analysis procedure is included to evaluate the defect visibility and calculate the POD therefrom.
X-ray computed tomography (CT) is a volumetric (3D) Imaging diagnostic method, well established in the medical field, and in industrial NDE as well. Developments in industrial CT aim to extent the applicability to complex structures, which do not allow the access of all directions. This are e.g. limited view, data and angle CT applications. New reconstruction algorithms are required on one
side, and the accuracy has to be improved on the other side. Numerical Simulation can support such developments by providing well defined data sets for the testing of reconstruction algorithms. This approach of virtual CT is realized within the radiographic simulator aRTist, developed by BAM. The poster shows the possibilities of this tool to consider complex scan paths. Simulated data sets have been reconstructed by an versatile backprojection algorithm.