Background
Modeling is an important tool within NDT, partly to develop and optimize testing technologies, but also within the Qualification Body’s activities to assess technical verifications and perform parameter studies. SSM has supported university research in the area for many years and, among other things, in the development of a software for ultrasound modeling. In addition, the accredited NDE laboratories are increasingly using software for modeling inspection situations.
CIVA, developed by French CEA, is the commercially most successful software in simulation of NDT situations. The program according to the supplier can handle different materials, geometries, cladding and anisotropy in arbitrary symmetry and orientation. Even simulation of material structures, different probe types and defects with arbitrary shape, size and orientation can be simulate. UT, ET and RT are the NDT methods that the program can simulate. A project was started to evaluate the usability of the software within qualification projects.
The work performed within this research report only handles with the UT-module of the simulation software. The intended purpose with CIVA is to provide a tool for developing and optimizing probe design, enhancing qualification and supply help in analysis of inspection results.
The work has been carried out as collaboration between SQC (Swedish Qualification Body) and AMEC.
Objective
The purpose of this project has been to evaluate the usability of the simulation software CIVA within qualification projects.
CIVA software is used more and more in connection with qualification of NDT inspection systems, both during technique development and as a part of the technical justifications. The Qualification Body has to know the boundaries of such simulation tool to be able to assess the simulation results presented in a technical justification. Other areas where the Qualification Body can use this simulation tool (if verified) are parameter studies. Parameter studies can be used for review of important parameters, in order to find out limit values as well as which parameters are most important for the inspection system. In addition, optimization of defect content for the manufacture of test blocks can be done.
Results
The results of the work performed in this project indicate that simulations and experiments matches rather well.
The largest discrepancy between the simulations and experiments is noise or rather signal to noise ratio. Noise caused by the material structure can be modelled in CIVA but as a separate layer, which is super positioned on top of the defect response simulation, meaning that the defect response is not affected by the noise. If a noise simulation is used, it must be used together with additional attenuation modeling or else the result will be a non-conservative signal to noise ratio for any given indication. No simulations of noise or attenuation were made within this project. It is not possible to simulate a complete inspection, or validate an inspection procedure by simulations with CIVA at the current time.
Both the producer of simulated data and the evaluator must have great knowledge about the CIVA software to be able to draw the right conclusions from the results. Whether CIVA can be used in qualifications or not is a question of the purpose of the simulation and also the extent of the usage of simulated data.