DEPARTMENT OF MECHANICS AND APPLIED MATHEMATICS

NON-LINEAR ACOUSTODIAGNOSTICS

DESCRIPTION

Acoustodiagnostics - i.e., nondestructive determination of the investigated phenomena on the basis of wave propagation data - of the physical and geometrical properties of various objects and media has found wide range of applications in engineering and medicine. The use of ultrasound in non-destructive testing has been known since the discovery of the piezoelectric effect in quartz in 1880 that enabled to use electric signals to generate mechanical vibrations. Many special techniques were developed thereafter to evaluate the material properties on the basis of the theory of wave-material interaction. The mathematical basis of acoustodiagnostics of homogeneous media (material) with simple geometry as well as media with homogeneous predeformation has been developed in detail. When the geometry is complicated - and specially if the material is inhomoge-neous, microstructured and/or prestressed - the amount of information to be determined in acoustodiagnostics increases tremendously.

In this project the methods of acoustodiagnostics of complicated cases are intensively studied. Attention is mainly confined to the investigation of predeformed and inhomogeneous materials The possibility of non-destructive evaluation of inhomogeneous predeformed state and variable physical properties of materials is considered theoretically. The idea is to extend the efficiency of acoustodiagnostics by using the wave profile evolution data, in addition to the wave velocity measurement data. The result is that the relatively simple tests enable to evaluate the inhomogeneous properties of the material in many cases.

Phase shift of the sine-wave first harmonic versus the intensity of the
uniformly and quadratically distributed normal load applied to the plate

STAFF

• Arvi Ravasoo, Ph.D. (Cand. Sc.), senior research fellow
• Andres Braunbrück, master student of Tallinn University of Technology

PARTNERS

• Prof. B. Lundberg,
  Uppsala University
• Prof. J. Ballmann,
  Aachen Technical University

GRANTS

• ESF Grant No. 481/1908, 1995-1997
• ESF Grant No. 3131, 1998-2000
• Royal Swedish Acad. Sci. Grant, 1995/96
• BMBF Grant N 03N9005 2, 1996-1999
• Royal Swedish Acad. Sci. Grant, 1997/98

PUBLICATIONS

In 1995-1999, seven articles in refereed journals, seven talks at international conferences, twelve Research Reports