APPLYING HIGH-ENERGY X-RAY DIFFRACTION TO QUANTIFY MULTI-AXIAL RESIDUAL STRESS GRADIENTS
Budrow, Christopher Jeffery
This dissertation focuses on improving residual stress measurement techniques using synchrotron based high-energy x-ray diffraction (HEXD). HEXD is an emerging tool for measuring multi-axial stress gradients because it is able to non-destructively probe the interior of crystalline solids. Improvements were developed in three case studies. In the first study, the residual stress profile induced by carburization was studied and a new lattice parameter correction method was developed. This method applied a traction-free surface condition (a mechanical constraint) to determine a surface lattice parameter (a materials problem), thus making the technique more robust. In the second study, finite elements were used to impose mechanical constrains on a measured stress field, which revealed stress gradients that had been obscured by relatively large gage volumes. The mechanical constraints were applied in the data processing step and prevented the use of a complex slitting system, making the experiment sim- pler. Finally, in the third case study, a method for conducting a measurement sensitivity study is proposed. This method identifies the error (relative to a full set of data) associated with conducting less strain measurements and results show a reduced measurement scheme, which produces low error, is possible and stress dependent. This allows data to be collected more quickly so experi- mental research time (beam time) can be used more efficiently. These case stud- ies serve to advance residual stress measurements using HEXD by making the experimental methods faster, simpler, and more robust. The efforts outlined in this dissertation serve to elevate synchrotron based HEXD one step closer to becoming a readily applied engineering and industry tool.
Carburization; Finite Element; Residual Stress; Synchrotron; X-ray Diffraction
Miller, Matthew Peter
Dawson, Paul Richard; Earls, Christopher J.
Ph. D., Mechanical Engineering
Doctor of Philosophy
dissertation or thesis