RICERCA ITALIANA     

Research program

Integrated Methods and Algorithms for NonDestructive Evaluations of architectural heritage

University Co-ordinator

Università degli Studi di CATANIA - INGEGNERIA ELETTRICA ELETTRONICA E DEI SISTEMI - CATANIA(CT)

Research Unit Leader

Giovanni Antonino AIELLO

Description

In consideration of the great importance which problems concerning the protection of the historical and artistic heritage hold today, there exists a growing activity intended to search for, develop and use testing techniques for their preservation, featuring by an increasing measure of accuracy and result reliability. Another requirement, also held in great consideration, is to reduce, if not to cancel out completely, the invasive nature of such techniques. In fact, the numerous non- destructive testing (NDT) techniques available today, and more specifically electromagnetic and ultrasonic techniques, are acquiring greater importance. The two types of techniques present, as is to be expected, have their advantages and disadvantages, which render them, to some extent, complementary with respect to each other, as concern both their sphere of use and the type of information obtainable from them.
In the context of the present research project, the research unit (RU) no. 5 intends to develop a finite-element code for the computation of both the electromagnetic field (EM) produced by the scattering of an EM wave generated by a transmitter antenna (generally working in the microwave range), placed in the proximity of a building structure, and the displacement field of an ultrasonic wave created by a suitable generator tool. In order to approach the problem gradually and in consideration of the subsequent validation of the code, we think it convenient initially to develop a bi-dimensional version, which uses simplex Lagrangian finite elements, including high-order elements. Then, we intend to develop a version of the code, which is able to treat tri-dimensional problems fully, based on the use of edge elements for the electromagnetic case and nodal finite elements for the ultrasonic one. With regard to the problems under examination, it is of crucial importance that the code be able to solve the field equations in the presence of strong non-homogeneities in the materials and walls of considerable thickness with respect to the wavelength. The code thus obtained will be inserted into a more wide finite-element code, called ELFIN, entirely developed by researchers from the RU no. 5 for research aims only.
Once this code has been tuned, in a further phase we will proceed, in collaboration with researchers from the RU no. 3, towards the definition and implementation of an optimized procedure for the design of a transmission-receiving system, in order to determine its characteristics and the parameters which guarantee optimal performance in terms of both reliability and diagnostic flexibility in identifying defects inside the building structure, such as cracks, cavities and the corrosion of metallic frameworks, and the computational effort needed to use the procedure itself. For the realization of the system, during this phase we will take several typologies of antenna into consideration both traditional types and more recent ones. As regards optimization methods, we foresee using stochastic methods such as Genetic Algorithms and Simulated Annealing, owing to their robustness and flexibility, and the existence of consolidated research activity in this sector in the RU no. 5.
As regards the finite-element code for the ultrasonic analysis of building structures, we foresee to collaborate with the researchers of the RU no. 2 for the experimental validation of the simulation accuracy.
Finally, in the last phase of the research project, we will contribute to the classification of the main types of defect.
From the operating point of view we intend to structure the activity in the following four phases:
1)development of a bi-dimensional version of the code;
2)development of a tri-dimensional version of the code;
3)tuning the optimisation procedure of transmitting-receiving system;
4)contribution to the defect classification.