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Simulating to help NDE methods to improve their performance and competitivity:

Nowadays, because of the complexity of the received signals and of the uncertainties, Acoustic Emission NDT is not said to be a really quantitative testing method. The analysis is generally limited to a small part of the information available from the different sensors and the main efforts to interpret the results are used to reduce the quantity of data to extract.

However, AE shows certain advantages that should allow it to be more popular in the NDE community: Ability to control rapidly very large structures, high sensitivity to crack breaking, compatibility with a continuous monitoring of the devices, cost effective compared to hydraulic testing, etc.

The availability of a simulation tool should help to greatly improve the understanding of inputs and outputs of Acoustic Emission testing and then to make it more quantitative then more popular. A better knowledge of the signals will enable to find new interpretations from inspection results and will generate more a complete diagnosis. One can think about the ability to characterize the detected flaws: Nature, dimension, more precise localization. NDT AE will have the possibility to better complete or replace hydraulic testing and then reduce the associated impact (corrosion, discharge of pollutants in the environment, etc.).

In the different sectors in which this technique is used, the improvement induced by the simulation shall bring:

• Competitivity profits (lower cost, higher performance),
• Reliability improvement,
• More quantitative output data allowing to bring elements to justification works for the qualification,
• A help for technical demonstrations to convince an end-user that this technique can be relevant for a given control,
• A reduction of environmental impacts during the control of pressure devices,
• A visual and interactive support to train operators,
• A technical support for the evolution of standards.

Technical gains provided by a simulation tool in acoustic emission:

A simulation software will help users :

When designing and preparing test campaigns,

• By visualizing the different propagation modes depending on the thickness and the distance source to sensors,
• By calculating the attenuation laws of waves depending on :
  • their propagation mode,
  • the influence of surrounding media (air, gas, liquids),
  • the influence of internal or external claddings (thermal insulators, fireproofing, etc.),
  • the influence of obstacles (nozzle, change of thickness, welds, elbows, etc.),
  • the influence of the temperature,
• To guide the choice od sensors (frequency, mode sensitivity, directivity),
• To design wave guides in particular conditions of service (high temperature, corrosive media, thick claddings, etc.),
• To optimize the type of sensor networks and the distances between sensors.

When analysing inspection data, in order to indeify the propagation modes in each detected signal and assign it the good velocity which will allow to optimize the triangulation algorithms in the different cases:

• In thin structures, where the multi-modal nature of lamb waves can bring discrepancies, for which today the localization algorithms have to remove a large part of the signals,
• In thick structures, where, when the source of acoustic emission is close to the sensor, bulk waves signals can give additional contributions that would mask the targetted rayleigh waves signals, leading to a bad precision of the localization,
• In very thick structures, where the localization using surface waves is not very relevant any more but where no algorithm using bulk waves is available today.

Advantages of the integration in the CIVA platform:

The development will take benefits of the architecture of the CIVA modeling platform, world leader for the simulation of NDT which will provide to this module, right from the beginning, a renown linked to the large diffusion of CIVA within industry.

Moreover, the dedicated interface of CIVA makes possible the use of simulation directly by NDE engineers which are not modelling experts.

Finally, to make this tool really usefull in an industrial contexte, it is required that this software can run on classical computers. That’s why, like for the other modules of CIVA software, the Acoustic Emission simulator will rely on semi-analytical methods, more adapted to an efficient modeling of the multi-physics and multi-scale (from millimeters to meters) phenomena of acoustic emission, for which a fully numerical approach would lead to unsolvable problems due to hardware memory limits. Available for an intensive use in engineering departments, this module will ease the realization of parametric studies.