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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.
An approach is presented to construct operators for transforming the characteristics of incident radiation to transmitted radiation, as well as operators for transforming the transmitted radiation to measured values. Simu-lating the radiation transport is based on Monte Carlo modeling of the interaction of X-ray photons and electrons with matter. The proposed method permits to construct, for instance, the operator connecting the initial radiation spectrum with the absorbed photon energy penetrating a given object. The elaborated approach provides the possibility of effective mathematical modeling of radiation techniques such as radiography, treating complex multi-component objects. Moreover, the method can be used to construct the operator equation for solving in-verse problems, e.g. the reconstruction of the initial radiation spectrum using simple experimental measure-ments. Comparison with some experimental measurements is presented.
Statistical algorithms are presented for modeling the interaction processes between electrons and matter. A software
implementation has been developed for hybrid supercomputers making use of NVIDIA© CUDA©
technology. Standard Monte Carlo schemes are modified for effectively exploiting the parallel computing capabilities
of graphical processors. The model of individual collisions (MIC) is used to describe the interaction of
electrons with atoms. This model does not include the approximations assumed in multiple collision theory or
the continuous slow down approach with the Landau theory for energy-loss fluctuations. The distributions of
electron characteristics are obtained from tabulated electron cross section data. The examples discussed in this
paper demonstrate the applicability of the algorithms to investigating the interaction of electrons with X-ray tube
targets producing Bremsstrahlung. The proposed technique can be used for mathematical modeling in radiography.
Computer simulation of radiography can be used for different purposes in NDT, such as qualification of NDT systems, optimization of radiographic parameters, feasibility analysis, model-based data interpretation, and training of NDT/NDE personnel. BAM has been working on modeling in the field of radiographic testing for many years. With the gathered theoretical background and the familiarity with practical requirements of industrial application the simulation software aRTist has been developed. This analytical simulator includes a description of the radiation source, the interaction of radiation with test pieces and flaws, and the detection process with special focus on film and digital industrial radiology. It features high processing speed with nearinteractive frame rates and a high level of realism. Here we focus on the recent developments of the simulator, notably the release of aRTist version 2. Extended functionality regarding automated virtual computed tomography now allows for arbitrary scan paths. Another program extension supports reliability investigations and provides a user interface for planning automatic simulations with varying parameters and defects.
A model is discussed which describes the generation of X-rays in conventional tubes using tabulated bremsstrahlung energy spectra depending on three variables: the target atomic number, the incident electron kinetic energy, and the fraction of energy radiated. Additionally a parameter-free description of the characteristic radiation is included. The constructed model includes technical tube parameters like kilovoltage, target material, and angles of electron incidence and photon emission to also account for self-absorption in the target, as well as radiographic parameters like filtering. In order to verify model results, detector response is also considered. The validity of the proposed model is shown by measurements. Future work includes the extension of the model to transmission targets. This research was supported by the German Federal Ministry of Economics and Technology under contract MNPQ transfer II D 5-30/06.
Within the framework of the European project PICASSO, the radiographic simulator aRTist (analytical
Radiographic Testing inspection simulation tool) developed by BAM has been extended for reliability
assessment of film and digital radiography. A simulation supported probability of detection (POD) methodology
has been developed and the validity of the approach has been studied using an application from the aeronautics
industry. An experimental POD has been determined with the help of a specialized software tool, developed to
aid with the collection of large series of POD data. The resulting POD is compared to simulations of the same
setting using aRTist and the newly available module for simulation supported POD. A quantitative agreement
within a few percent is achieved between the experimental and the simulation supported POD.
Modelling becomes more and more important in modern NDE. It is increasingly used to optimize techniques for complex applications and to support the preparation of written procedures. Hence, computer simulation nowadays has to be able to handle all significant properties of an NDE system with sufficient accuracy. In case of radiographic applications this includes models of the radiation source, of the interaction of radiation with materials, of the detection process, and the geometrical description of the part or the construction. Depending on the given inspection problem and the influencing factors that should be addressed by the simulation an appropriate physical model has to be chosen to describe the underlying interaction mechanisms. The simulator aRTist combines analytical and Monte Carlo methods to efficiently model the radiation transport. Simulation is a powerful tool to separate different influencing factors. Here we focus on Monte-Carlo simulation of scatter contributions within aRTist.
In this contribution, we discuss the influence of scattered radiation on materials’ effective attenuation coefficients at higher X-ray energies. The selected X-ray spectra for the dual-energy experiments correspond to 3 MV and 7.5 MV acceleration potential of the used betatron. Experiments were performed on a test phantom containing step wedges of different low- and high-Z materials. We evaluated the ratio between low- and high-energy X-ray attenuation coefficients quantitatively based on simulated poly-energetic high-energy X-ray source spectra and the detector sensitivity using the “analytical Radiographic Testing inspection simulation tool” (aRTist) developed at BAM. Furthermore, the influence of scattered radiation is evaluated using an efficient Monte-Carlo simulation. The simulation results are compared quantitatively with experimental investigations. Finally, important applications of the proposed technique in the context of aviation security are discussed.