MEASUREMENT OF 3D STRAIN IN BONE BY TEXTURE CORRELATION

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DESCRIPTION (Adapted from the applicant's Abstract): This application's goal is to develop a method for noninvasive measurement of 3D strain in solid objects with internal texture, particularly cancellous and cortical bone. The location of points internal to the solid will be determined using X-ray Tomographic Microscopy, using monochromatic synchrotron x-rays. These type of machines have resolutions several times greater than the "micro CT" machines. Displacement and strain in the solid will be determined using "texture correlation", a method developed by the authors for tracking identifiable points in an object with texture, such as cancellous bone, and computing strain from the displacement fields. After further development of computer algorithms to extend the method from 2D to 3D, a series of tests and analyses will be done to assess the accuracy and sensitivity of the method. In the first series, a uniform foam material will be tested in uniaxial compression. Both homogeneous cylinders and solids with a hole will be tested. A finite element model simulating the test will be constructed and analyzed. The finite element model results will be compared with the texture correlation method as a means of assessing the accuracy of the latter. The same procedure will then be done on cancellous bone from the vertebral body and proximal tibia of a pig. Material properties will be estimated from published stiffness/density data. Finally, a series of coarser data sets from the XTM will be used to assess the resolution of texture data needed to get acceptable resolution and accuracy of the method. It is possible that methods with less resolution, such as micro-CT, could give adequate strain measures.