benEFIT- Numerical simulation of non-destructive testing in concrete

Fabian Dethof (Professorship Engineering Materials and Building Preservation, HSU)

In order to assess the current state of concrete structures like a buildings or bridges without causing any damage, different non-destructive testing (NDT) methods can be performed. Some of those methods are based on elastic wave propagation like the ultrasonic testing (UT) or the impact echo (IE) method. The impact echo method is used to measure the resonance frequency of a plate-like structure. Therefore, a mechanical impact is generated (often manually) and the resulting waveform is measured at the structure’s surface just a few centimetres away from the impact point.

With the ultrasonic inspection direct reflections of defects or the back wall of the structure can be detected. Therefore, much higher frequencies are used and consequently a finer spatial resolution is required for simulations. When performing numerical simulations of these NDT methods with the aim of obtaining qualitatively realistic results, one needs to discretize the concrete as a heterogeneous material (cement matrix, aggregates and pores). For the simulations we use a finite difference staggered-grid code called EFIT (elastodynamic finite integration technique) as it uses the integral version of the underlying wave equations which makes the code more robust for strongly heterogeneous materials like concrete. However, as EFIT uses a cartesian grid and an explicit discretization of the concrete aggregates and pores is desired, the grid sizes can get very large and will use a lot of RAM. Here, will help us to optimize the code with respect to the amount of RAM used for the simulations. The reduction of RAM usage should allow a finer concrete discretization, which might be of particular importance for Ultrasonic testing simulations. Impact echo simulations, compared to ultrasonic testing, do suffer from a different problem which is the runtime. While the waves in UT simulations only have to be reflected once by the back wall or defect in order to detect them, in IE simulations the waves have to travel back and forth multiple times in order to give a stable and precise frequency spectrum. Here, a runtime optimization will help to perform more IE simulations in a shorter time as in reality often hundreds or thousands of single IE measurements are performed during one inspection.


Letzte Änderung: 20. Juni 2022