Meeting Abstract
In this study, we introduce a methodology, Large-Amplitude Oscillatory Bending (LAOB), which increases the accuracy of measuring mechanical properties taking into account non-linear viscoelasticity (NLV). The NLV approach extends linear viscoelasticity theory by allowing measurement of the changes in both viscosity and elasticity within a single loading cycle. Where linear measurements might provide information comparing different tail-beats during swimming, NLV output describes the properties during the tail-beat such as those found at minimum and maximum strains. We apply NLV to the characterization of the mechanical behavior of vertebral columns, the primary skeletal element of the vertebrate body axis. Here we characterize the NLV properties of Squalus acanthias, the spiny dogfish shark, vertebral columns using LAOB. Vertebral column segments consisted of ten centra and nine intervertebral joints were tested on a MTS Tytron 250 using bending frequencies and body curvatures seen during volitional swimming. The resulting moment and curvature data were analyzed using the MITlaos analytic tool, purpose-built for NLV studies. We found that as inputs increase in magnitude, so, too, does the level of non-linearity in both elastic and viscous moduli. In a swimming shark this means that during faster swimming the vertebral column will behave as a stiffer more elastic spring.
