Title

Resonance measurements of a pre-stressed spherical shell with application to non-invasive intracranial pressure monitoring

Presenter Information

Rafael Avila
Cameron Kastner

Document Type

Oral Presentation

Location

SURC Ballroom C/D

Start Date

15-5-2014

End Date

15-5-2014

Keywords

Resonance frequency, Pressure, Frequency shifts

Abstract

Recent experiments and numerical modeling by faculty and students at CWU have shown that resonance frequencies of a spherical aluminum shell (radius 3.0 in, thickness 1/8 inch) exhibit small shifts when different pressures are applied to the fluid inside. Further investigation is needed to determine whether this phenomenon can be exploited as part of a noninvasive method for monitoring intracranial pressure. The goal of the present study is to modify the experimental apparatus and procedure to more closely resemble clinical conditions and to acquire reliable resonance measurements. In previous experiments, the shell was suspended from elastic cords and the pressure was varied from 0 to 120 psig in steps of 10 psi. In the modified apparatus, we let the sphere rest on a support system, such as a ring stand, and the target pressure range is 0 to .5 psig in steps of 0.05 psi. Both modifications presented significant challenges: supporting the shell necessarily interferes with the vibrational response, and small pressure changes produce very small resonance frequency shifts that are difficult to detect. We present results comparing the efficacy of different support systems and preliminary results for detecting small frequency shifts.

Poster Number

7

Faculty Mentor(s)

Piacsek, Andrew

Additional Mentoring Department

Physics

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May 15th, 8:30 AM May 15th, 11:00 AM

Resonance measurements of a pre-stressed spherical shell with application to non-invasive intracranial pressure monitoring

SURC Ballroom C/D

Recent experiments and numerical modeling by faculty and students at CWU have shown that resonance frequencies of a spherical aluminum shell (radius 3.0 in, thickness 1/8 inch) exhibit small shifts when different pressures are applied to the fluid inside. Further investigation is needed to determine whether this phenomenon can be exploited as part of a noninvasive method for monitoring intracranial pressure. The goal of the present study is to modify the experimental apparatus and procedure to more closely resemble clinical conditions and to acquire reliable resonance measurements. In previous experiments, the shell was suspended from elastic cords and the pressure was varied from 0 to 120 psig in steps of 10 psi. In the modified apparatus, we let the sphere rest on a support system, such as a ring stand, and the target pressure range is 0 to .5 psig in steps of 0.05 psi. Both modifications presented significant challenges: supporting the shell necessarily interferes with the vibrational response, and small pressure changes produce very small resonance frequency shifts that are difficult to detect. We present results comparing the efficacy of different support systems and preliminary results for detecting small frequency shifts.