Meeting Abstract

27.2  Saturday, Jan. 4 13:45  Nonlinear Elasticity of Tracheal Tubes in the American Cockroach WEBSTER, M.R.*; SOCHA, J.J.; DE VITA, R.; Virginia Tech; Virginia Tech; Virginia Tech mwbstr@vt.edu

In some insect species, diffusion-based respiration is supplemented with convection. For insects that use rhythmic tracheal compression, convective ventilation is produced by the periodic collapse and re-inflation of various tracheae in the respiratory system, a phenomenon that is dependent on the unique structure and material properties of the tracheal tissue. To understand the underlying mechanics of this method of gas transport, we are studying the microstructure and material properties of the primary thoracic tracheal tubes in American cockroaches. In previous tensile tests, we found that these tracheae sustain large strains and exhibit a nonlinear elastic behavior. Although these tests provided crucial information about the mechanical behavior of the tracheal tubes, they were insufficient to fully describe the complex three-dimensional loading conditions experienced in vivo by these tubes. Inflation-extension tests, in which the trachea is pressurized while being stretched in the longitudinal direction, provide mechanical data that are more physiologically relevant. For this reason, we design and built an inflation-extension testing system that is able to measure low axial forces, internal pressures, and surface deformations of tracheal tubes of ~500 µm diameter. Images collected with two synchronized CCD cameras were analyzed using the digital image correlation method to compute the strain field. In addition, we also developed a constitutive equation that can capture the finite strains and nonlinear elasticity of the tracheal tubes. Our ultimate goal is to formulate a three-dimensional model that can be implemented into finite element methods to reproduce the complex mechanical response of tracheal tubes under in vivo loading conditions. Supported by NSF 0938047.