Ultrasonic and Stereo-Optical Characterization Techniques for Applications in Mechanical Testing

Authors

Jonathan M. Hein, University of Nebraska-LincolnFollow

Date of this Version

4-2011

Comments

A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Engineering Mechanics, Under the Supervision of Professor Mehrdad Negahban. Lincoln, Nebraska: May, 2011
Copyright 2011 Jonathan M. Hein

Abstract

This thesis considers methods developed based on ultrasonic reflections from interfaces and stereo-optical surface strain measurements to study the mechanical characterization of materials and bodies. The ultrasonic method is used to characterize wave speed and attenuation for highly attenuating samples. The stereo-optical strain measurements are used to characterize the effects of genes on mechanical properties of bone, and the dynamic characterization of blast waves in the UNL Shock Wave Trauma Mechanics facility.

A method is described and developed for characterizing the wave speed and attenuation spectrums from reflected waves from the contact surface with an unknown material. The method is demonstrated on samples of PDMS, PC, Sillyputty®, and bovine liver. This method has potential to characterize soft materials in the dynamic range where other methods cannot do so due to high wave attenuation.

In a study of the effects of genotypes on bone rigidity that was conducted in collaboration with Creighton University, the mechanical properties of mouse tibia were characterized. With the stereo-optical system (ARAMIS), a special method was developed to construct a 360 degree view of the deformation of each tibia as the sample was being subjected to axial compression. The effective modulus of the bone was calculated based on geometrical and strain data from the tests.

The ARAMIS system is also capable of performing high speed measurements such as is needed in shock loading. A series of experiments and analysis were performed to characterize the nine inch shock tube in the Shock Wave Trauma Mechanics facility at UNL.