Optical Characterization of Stressed Aluminum

The characterization of the effects of stress on materials is a field of inherent interest. Nondestructive evaluation (NDE) methods have been developed to assess damage before any major failures. Current NDE methods have several limitations such as expense and the need for highly-trained operators. To eliminate some of these limitations we have found an optical technique, second harmonic generation (SHG), can be used to characterize mechanical and chemical stress in aluminum. In optical surface SHG, one input light is converted to produce a SHG response at half the wavelength after interaction with the sample surface. In our work, we measured the SHG response before and after mechanical and chemical stress on 2024 and 5083 series aluminum samples. We monitored the SHG change of 2024 samples after we used tensile loading to induce mechanical stress. We found the SHG response decreases with increasing deformation. We also used an oven at 175 °C to speed up the chemical stress in 5083 samples. We monitored SHG response to the amount of chemical stress and found it to be directly correlated. These results suggest that we have a promising new method that could compliment current nondestructive testing