IIW-2363 Simulation of NDT

RECOMMENDATIONS FOR THE USE ANDVALIDATION OF NON-DESTRUCTIVE TESTING SIMULATION

3. Considerations and recommendations for the validation of codes

The sources of error in the above list which must be considered as possibly contributing to the inaccuracy of the “simulation” are items 2 to 5.

This situation corresponds to the least informative one. The conclusions of the validation are essentially limited to the application under consideration. When the objective is to evaluate the reliability of the predictions provided by one given code in a range of situations of interest defined by qualifying characteristics (on probes, components, flaws…), the process under validation is reduced to the simulation itself. The sources of error in the above list which must be considered as possibly contributing to the inaccuracy of the “simulation” are items 3 to 5. In this case the conclusions of the validation can be transposed to similar applications of the same code. When the objective is to evaluate the validity of the theoretical model itself (the mathematical formulation and eventually its numerical implementation) or one limited aspect of the model (one specific approximation), the process under validation is limited to the model. The sources of error in the above list which must be considered as possibly contributing to the inaccuracy of the “simulation” are reduced to items 3 and 4. This situation is the most academic and the most general. The information provided is of interest not only for one specific code but can be transposed and help with justifying the use of other simulation codes based on a similar model. 3.2.3 Experimental uncertainity The accuracy of the experiment itself is measured by the reproducibility of experimental results for one fixed set-up (one fixed equipment, one fixed specimen under test and one fixed procedure). The possible factors limiting the accuracy of the experiment are: sources of noise, fluctuations in parameters pertaining to the measurement, the effects of influential parameters or phenomena not listed in the definition of the set-up.

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Recommendations related to this issue are given § 3.4, items 5 and 6.

3.2.4 Uncertainty linked to the determination of the inputs of the simulation

The real trial is represented by an amount of information transformed into inputs for the simulation code.

The inputs of the simulation generally consist of qualifying characteristics (type of probe, isotropy of the material, etc…), and the values of essential parameters (frequency of the excitation, wave speed in the component, CAD files, etc…). In general identifying elements, such as the type or serial number of a piece of equipment, are not part of the information transferred to the simulation.

This representation of the real experiment by a set of inputs:

i. is based on hypotheses about the specimen under test (geometrical assertions, material considerations, etc…) or about the equipment behaviour (piston source behaviour of ultrasonic probes for example), ii. requires the determination of the input values of the essential parameters. Both hypotheses which may be approximations, and uncertainties or inaccuracies in the determination of essential parameters, may have a considerable influence on the relevance of the simulated results. Recommendations related to this issue are given § 3.4, items 4 and 7.

International Institute of Welding