|NDT.net June 2006 Vol. 11 No.6|
Simulation Software of NDT TechniquesFabrice Foucher*, Cedrat SA; Laurent Le Ber, Steve Mahaut, Commissariat א l'Energie Atomique.
ABSTRACTSimulation and data processing in Non Destructive Testing p lays an increasing role for analysing results (improve the identification, location and characterization of defects) or p erformance demonstration (evaluation of the capability of a given method and identification of the limitations). Another very common application, particularly for phased-array methods, is the design and optimization of inspection methods. Large work for over ten years has led to CIVAnde software to fulfill the requirement of computation times compatible with practical use in industrial context, a twofold strategy was put forward: the choice of semi- a nalytical methods and the development of models integrated into software modules usable by operators who are not simulation specialists. The application fields have become increasingly diverse: nuclear industry, aircraft industry or petrochemical, railways,...
Ultrasonic tools in CIVAnde• Nozzle inspection:
We can see in figure 1 an example of ultrasonic simulation performed in CIVAnde concerning a nozzle inspection. The nozzle is specified by a few parameters (diameter, depth and orientation of the two pipes) and automatically a CAD designed nozzle is built. A wedge coupled transducer has been located outside the secondary pipe and the field computation module has been executed. The display is a cartography of the magnitude of the velocity potential within the component. It can be noticed that, on this example, the field computation accounts for reflections on the internal surface of the nozzle.
• Phased Array & Electronic
• Highly Bended composite
It means that 8 elements are fired over an overall aperture of 64 channels. The first 8 elements are used at transmission and reception, then this aperture of 8 elements is successively translated to cover the whole array.
The efficiency of this technique can be evaluated and qualified in the echo computation module of CIVAnde First, six flaws have been aligned along the curved part, then another simulation has been performed with several misaligned flaws (see figure 3). On the first simulation, thanks to the normal incidence of the longitudinal waves hold all along the curved part, the echoes are clearly separated , there is neither distortion neither attenuation between the different ones. On the second simulation, echoes are still clearly separated but signal distortion and attenuation appears for misaligned defects.
• Tandem Technique:
Such inspection techniques may be carried out to detect mid wall defects in noisy materials, as they provide a way to assess flaws in specular reflection (as a contrary a pulse echo inspection with one single probe cannot be used for an optimal corner echo as soon as the defect is not emerging at back wall or front wall). As the elements may be arbitrarily selected, and, in addition, with arbitrary delay laws applied, phased array allows a flexible tool for tandem inspections. In this example, three mid wall defects have been inserted in a cylindrical component at different depths. A contact phased array made of 48 elements is used with separate elements at transmission and reception. Inspections have been simulated for three different settings of the phased array probe, each setting being designed to optimise the inspection of one particular defect.
The delay laws are computed to focus shear waves at the selected defect depth, in direct mode for elements used at reception, and focusing after back wall reception for elements used at reception. We can see on the echo dynamic curves that, for each set of delay laws, the echoes of the different defects are clearly separated (figure 5).
Eddy Current simulation tools in CIVAndeThe main problem in Eddy Current Non Destructive Evaluation consists in predicting the effects due to the interaction of eddy currents with defects within a conducting material. For many applications, the surface curvature is low and can be locally considered as planar. The response of a surface riding coil to a 3D flaw in a slab can be computed with great time efficiency and accuracy with the semi-analytical model. CIVAnde also offers the possibility to simulate the response of an encircling coil or a bobbin coil for any configuration of tubes with axisymmetrical flaws such as grooves or 3D flaws. An example of a signal obtained with a differential bobbin coil at 100 kHz with a longitudinal notch is given in figure 6. This flaw is a 54% tw outer notch of 10 mm length and of 0.1 mm opening. The agreement is excellent between simulation and experimental data.
ConclusionsIn this paper we have briefly presented the capabilities of the CIVAnde software. Emphasis has been put on the major ultrasonics and Eddy Current simulation tools existing in the plat-form. For both techniques, the semi-analytical modeling approach has been chosen to minimize numerical costs for an industrial use of the codes. With successive versions of CIVAnde, the last results of research are integrated in order to improve the software capability and to widen the fields of applications.