Non-invasive Ultrasonic Inspection Through Steel Pipes Using the SURF Method
The main objective of this thesis has been to study the possibility to establish
a simulation tool for Second Order Ultrasonic Field (SURF) based on finite
element modeling implemented in COMSOL Multiphysics. The SURF method
is a dual-frequency ultrasonic imaging technique where two waves are trans-
mitted in the same direction with a large separation in frequency of about 1:10.
This causes interaction between the waves, which give rise to non-linear sound
propagation. The method can be used for enhanced ultrasonic imaging ca-
pabilities. The COMSOL implementation has been documented and through
studies of normal incident waves and oblique incident waves at a steel interface,
the advantages and disadvantages of the implementation has been highlighted.
The SURF method has been implemented in the built-in physical interfaces
of Pressure Acoustics and Acoustic-Solid Interaction in COMSOL. Simple 2D
normal incident plane wave simulations have been compared to theoretically
calculated values of non-linear speed of sound, with matching results. The
study of the plane wave model has been extended to include water and steel
modeled as both linear and non-linear materials. Studies on the possibility of
analyzing non-linear materials behind steel have shown possible ways to ensure
transmission through steel, despite high impedance ratios between water and
steel. The most promising methods proved to be based on impedance match-
ing and standing waves which coincides with other studies on the topic.
Simulations with the Acoustic-Solid Interaction interface on large models,
which include structural waves and deformations, have been bounded to a
low frequency study in a SURF scheme. This is because of a rapidly increas-
ing computational time, as a function of degrees of freedom to solve for in the
model. Estimations predict solution time of in terms of weeks on large scale
models, when the fundamental convergence criteria of elements per wavelength
and number time steps in a time dependent finite element analysis are fulfilled.
Possible measures to overcome this are performing the simulations on a more
powerful computer, modifying the implemented solution process or using a
different solver than the direct solver used in this thesis.
Place, publisher, year, edition, pages
Institutt for elektronikk og telekommunikasjon , 2014. , 75 p.
IdentifiersURN: urn:nbn:no:ntnu:diva-26490Local ID: ntnudaim:11058OAI: oai:DiVA.org:ntnu-26490DiVA: diva2:747991
Pettersen, Odd Kr., Professor IIJohansen, Tonni Franke