Analyzis of optical techniques as non-destructive test to detect internal failure in materials

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Biological materials are governed by a disordered growing which promotes nonlinear deformations and deflects cracks into configuration. Nondestructive methods applied to detect material failure is experiencing significant development in engineering. Optical techniques are known to be simple application when compared with conventional methods of stress-state analysis and literature emphasizes speckle interferometric and moiré optical techniques as full field stress-strain state. This research work aimed to analyze the use of optical techniques to be applied as nondestructive test to detect internal material failures. Specimens included material of 1020 steel. Traction tests followed the brazilian norms. The experimental set up to carry on the moiré method included a grid of 0.2 mm density and for the speckle method it was included a laser of 632 mm of wavelength with collimated lens. The differences between the loaded and unloaded specimen images patterns are closely related to the imposed deformation. Image processing generated maps of deformation and surface deformation. Results showed that moiré technique methods generated precise identification of the point on the specimen surface of internal failure occurrence while speckle interferometry showed was precise. Moiré method presented some advantages if compared to the speckle interferometric method. It can be concluded that both tested methods can be used as nondestructive method to detect internal failure on the object surface.