Testing Cell for Online DIC and Raman Spectroscopy

Digital Image Correlation (DIC) technique can be used for the monitoring of the specimen strain, the specimen deformation, the crack initiation and early crack growth. Raman spectroscopy is a method used for the monitoring the corrosion products and the surface films on the passivating materials.

Cormet has designed and built instrument where an optical window has been positioned close to a single edge-notched (SENT) specimen or cruciform specimen. Regular Cormet’s electromechanical loading device is used to apply stress on the specimen. The specimens are positioned in a testing cell operating in HT HP water at 350°C temperature and 200 bar pressure.

Operator installs a DIC or Raman instrument optics and optionally a light source close to the sapphire window positioned in the testing cell bottom lid. It is obvious that water in between the sapphire window and the specimen lower surface reduces the visibility. Therefore the distance has been minimized down to max. 5 mm.

The main benefit of this instrument is related to its on line and in situ nature. One can monitor the crack growth process or the corrosion layer formation continuously in the operation environment. The tests are not biased due to the cooling process related phase changes or contamination as the tests are performed in situ.