Photoelastic Method
The photoelastic method is an experimental technique used to determine the strain an object is experiencing when subjected to certain loading conditions. This technique is commonly used to analyse rigid structures such as bones when in a biomedical engineering setting, but with the advances in the lost-wax process developed here at CABER, the technique can now be applied to flexible structures, such as healthy and diseased arteries.
Analysis of AAAs
A previous publication of CABER (Morris et al., Strain, 2004) identified the use of the photoelastic method as a powerful tool to determine the strain experienced in an AAA. This used the lost-wax process to create an experimental AAA made from photoelastic liquid plastic which is then coated internally with a reflective coating. The model is then subjected to a simulated cardiac pressure loading and a polariscope is used to quantify the strain magnitude. Results revealed that the region of maximum diameter experiences significantly lower strain than the regions of inflection at the proximal and distal areas of the AAA sac. These findings were later validated using FEA.
Figure: Strain contours on an idealised AAA using the photoelastic method
The work at CABER using the photoelastic method to examine realistic AAA geometries and the correlation of wall stress distributions with both FEA-predicted wall stress and Gaussian surface curvature was recently awarded the cover image in the September 2010 issue of the prestigious clinical journal Arteriosclerosis, Thrombosis and Vascular Biology.