Development of 3D Digital Image Correlation and its Application in Analysis of Ocular Inflation Test Data

Dual Phd Programme with University of Liverpool and the National Tsing Hua University:
The PhD student will spend 2 years studying at the University of Liverpool and 2 years at National Tsing Hua University under the bilaterally agreed 2+2 scheme between the two institutions. The expertise developed at National Tsing Hua University and the University of Liverpool will be transferred between them, to the benefit of both institutions.

Project aim, objectives and outline
2D Digital image correlation (DIC) has seen increasing use in the analysis of mechanical tests. The technique offers a low-cost, high resolution method to trace the deformation of objects when subjected to mechanical forces, and can determine with high accuracy the distribution of displacement and strain across the monitored area of the test specimen. However, difficulties arise when dealing with objects that have significant curvatures such as the case in tests on the eye, and in areas with steep gradients relative to the plane of the camera image, the accuracy of DIC deteriorates. This project will seek to overcome this problem by developing a 3D version of the DIC technique for applications involving curved surfaces. The research will employ a number of spatially oriented digital cameras that can monitor the curved surface of the test specimen. The 2D images will be analysed and combined to form a 3D image of the surface by using information on the location and orientation of each camera and relying on significant overlap between adjacent cameras to improve the match between images and reduce the error or fit.

The project will have two main components; it will seek to develop the 3D DIC technique followed by its application in the analysis of ocular inflation test data. Inflation testing is regularly used to determine the material behaviour of corneal and scleral tissue. The technique is based on subjecting the eye to cycles of internal pressure while monitoring its deformation using a system of digital cameras. The camera images are analysed only in 2D and because of the problem discussed above with curved surfaces, attention is normally limited to the edge of the specimen as seen from individual cameras. If successful, the new 3D technique will represent a step change in the way inflation data is analysed and in the magnitude and quality of data obtained on ocular material behaviour.