Measurement of Microscopic Residual Stress Based on the Evolution of Surface Roughness During Shallow Chemical Etching

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A study will be made of stress-induced surface roughening caused by shallow chemical surface etching. The results will be adapted to residual-stress measurement. Previous work has shown that a simple spectrum analysis of nanometer-scale height changes in surface roughness caused by chemical etching permits determination of residual-stress components in solids. The principle of the analysis is that etching triggers stress-induced surface instability, resulting in a roughening of the surface controlled by the magnitude of the residual stresses and their direction. The experimental method is called "surface roughness-evolution spectroscopy (SRES)," and it measures residual stress components in solids with high spatial resolution. The study will include modeling and experimental studies of surface roughening caused by various etchants in shallow chemical etching; this research is expected to provide fundamental understanding of the roughening process of stressed solid surfaces, while etched chemically. In addition, the understanding will be applied to measuring microscopic residual stresses in technologically important solid structures, e.g. manufacturing-induced residual stresses in optical fibers and intra-granular residual stresses in polycrystalline solids. The resulting experimental method of skin test for residual-stress measurement is expected to make a significant impact in assessing manufacturability, reliability and residual life of solid components, which is essential in developing and maintaining proper infrastructures of civil and mechanical systems.