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Quantitative Ultrasonics

The ERL Quantitative Ultrasonics Team performs research on complex materials, both manmade and natural. Our interests span everything quantitative that can be done with ultrasonics: evaluation of mechanical properties (stiffness tensor components, shear properties), viscotic properties (loss modulus, attenuation) and changes in them. Most research is done non-destructively, thus allowing the same samples to be probed with other measurement methods.We also combine quantitative ultrasonics with other measurement techniques, e.g. X-ray scattering and mechanical testing.

For further information about the team, please contact the team leader Dr. Ari Salmi, ari.salmi (at) helsinki.fi.

Current EQUATE projects:

Localizing defects in adhesion between a metal hemisphere and a polymer shell

We aim to study whether one can experimentally detect defects in adhesion between a metal hemisphere and a polymer shell. To this end, we built a custom made contact and a non-contact setup to launch ultrasonic waves that propagate along the hemisphere. The presence of extra echoes and changes in the Fourier transform as a function of angle allowed us to quantitatively determine the location of localized non-adhered areas.

 

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Samples. (left) Hemispherical cavity milled into UHMWPE base, a 17.5 mm hexagonal hole in the base is visible. (right) Steel shell dislodged out after gluing, featuring glue everywhere except at the location of the hexagon. The coordinate system used to localize the defect is shown.

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Detecting a localized defect in adhesion. FFT of received signals as a function of θ. (top left) reference sample, (top right) 17.5 mm diameter defect, (bottom left) 10 mm diameter defect and (bottom right) 5 mm diameter defect.

 

 

 

 

 

 

 

 

 

 

 

 

Participating team members: Dr. Ari Salmi, Ms. Olga Heino, Dr. Adam Hacking (affiliated team member, MGH)

Recent publications:

A. Salmi, P. Karppinen, S. A. Hacking, E. Haeggström, Non-contact quantification of adhesion between a metal hemispherical shell and a polymer base by guided acoustic waves, Proceedings of the 2012 IEEE UFFC, DOI: 10.1109/ULTSYM.2012.0362

A. Salmi, O. Heino, H. J. Nieminen, T. Salmi, P. Karppinen, T. Patola, S. A. Hacking and E. Hæggström, Detecting defects in adhesion between a metal hemisphere and a polymer base, Proceedings of the 2013 IEEE UFFC, DOI:

For more information, contact ari.salmi (at) helsinki.fi

 

Determination of the modulus of the unit cell of materials by a combination of X-rays and ultrasound

We combined standing wave ultrasonics and X-ray diffraction to quantitatively determine the mechanical properties of the unit cell of materials. Part of the research was performed at the ESRF Grenoble facility.

 

Participating team members: Dr. Ari Salmi, B. Sc. Antti Meriläinen (affiliated team member), Dr. Kari Pirkkalainen (affiliated team member, X-ray laboratory), Dr. Mika Torkkeli (affiliated team member, X-ray laboratory)

Recent publications:

A. Salmi, A. Meriläinen, M. Peura, E. Hæggström and R. Serimaa, Microelasticity in Wood Using X-ray Diffraction and Ultrasound, ICU 2007 Conference, Vienna (Talk)

A. Salmi, A. Meriläinen, M. Torkkeli, E. Hæggström and R. Serimaa, Combining X-rays and Ultrasound to Determine Micro-elasticity in Wood, Proceedings of the UFFC 2007, pp. 54-57

A. Salmi, Master’s thesis, 2008

Ongoing research:

Determining Unit Cell Elasticity by Combining X-ray Diffraction and Ultrasound