Development of efficient hybrid finite element modelling for simulation of ultrasonic Non-Destructive Evaluation

The measurement and numerical modelling of ultrasonic wave scattering is essential for detecting complex defects in safety critical components for engineering structures across a range of industries. Fast and accurate numerical modelling to simulate candidate set ups for Non-Destructive Evaluation (NDE) is attractive as it both improves confidence in the inspection results and reduces the cost of experimental qualification. As the scope of applications broaden and the modelling complexities increase, simulations become more computationally intensive. However, such demand can be reduced by using different kinds of modelling for different features and combining them in a hybrid method. For example, analytical methods are efficient for modelling propagation through the volume of the material, whereas the Finite Element (FE) method is a better solution for modelling discrete complex details such as the local scattering from an irregularly shaped real defect. The authors have developed this concept into a generic hybrid method, in which separate small local domains containing the distinct features, for example, the source, defect and receiver can be modelled by separate, appropriately chosen, local models (e.g. FE), while the propagation through the volume between them is modelled analytically. Despite the computational gains achieved by using the hybrid method, the FE model of the region around the defect can still be very demanding of computer resources, especially for simulations in 3D. The authors have been investigating approaches to improve the efficiency of the FE modelling for ultrasonic NDE, for example: more efficient sound-absorbing elements around the FE domain, regular mesh generation and GPU-driven FE calculations. The wave propagation simulations from the hybrid method, with additional development to incorporate the results of these investigations, show similar accuracy but require less computational power than previously. Furthermore, the hybrid model has been developed, within the SIMPOSIUM project, to link with the CIVA software for NDE. The CIVA simulation software manages the overall model and the wave propagation in the component, while the hybrid model brings in FE simulation for the defect. In this case the FE simulation can be done using a commercially available package that has the quality approval and familiarity needed for industrial users. This paper will present the development of the hybrid method and demonstrate its application. The research leading to these results has received funding from the European Community’s Seventh Framework Program (FP7/2007-2013) under Grant Agreement No. 285549: SIMPOSIUM project.