SUBJECT: Ph.D. Proposal Presentation
BY: Fang Li
TIME: Monday, March 30, 2009, 10:00 a.m.
PLACE: MARC Building, 401
TITLE: Study of Stress Measurement Using Polariscope
COMMITTEE: Dr. Steven Danyluk, Chair (ME)
Dr. Jianmin Qu (ME)
Dr. Shreyes Melkote (ME)
Dr. Ajeet Rohatgi (ECE)
Dr. Dennis Hess (ChBE)


This thesis will investigate stress measurement using polariscopy for thin flat material and will be applied to multi-crystal silicon as a model material. The anisotropic properties of silicon in the measurement will be studied and anisotropic stress optic coefficients will be characterized for different crystal orientations and stress orientations. Then full stress components will be extracted from the measurement of the polariscope by shear difference method. Finally, the thermal induced stress from the system will be modeled using software ANSYS and will be accounted to the measurements. Recent x-ray diffraction results show that there are a variety of grain orientations in the multi-crystalline. Preliminary experiments show that the grain orientations have an impact on light transmission through crystalline materials and thus influence the stress measurement. It is crucial to calibrate the stress optic coefficients for individual grains. The normal stresses are crucial to determine the material breakage, crack propagation and residual stresses calculation when there is applied stress and vice versa. So it is important to obtain the full stress components from the polaricope measurement. Normal stresses can be calculated from equilibrium equations using shear difference method. This thesis will examine several methods of stress separation and apply these analytical methods to experimental data. Thermal stress induced by the system will be modeled using ANSYS and accounted for in the measurement