Application of speckle metrology for surface roughness extraction and non destructive evaluation
Pek, Quan Xiang
Date of Issue2016
School of Mechanical and Aerospace Engineering
This project focused on demonstrating a non-contact, non-destructive and accurate methodology for measurement of surface roughness and identification of defects in structures. For this purpose to be inherently advantageous, speckle contrast and speckle interferometry is adopted. This report also includes a thorough literature review on the different techniques used in the measurement of surface roughness and current non-destructive testing techniques that are currently available in the market. Speckle images obtained are used to analyse the contrast and a contrast map was developed thereafter to compare the surface roughness of the sample. Fringe patterns for sample with and without defect were acquired using speckle shearography. The images were captured by a CCD. Both set of images were taken a minimum of three times to ensure consistency of the images. The sample was subjected to a point load and three point loading. Finally, a sample with defect was investigated using vibration analysis. The fringe images were studied to identify the location of the defect. The results of the findings were consolidated and comparisons were drawn between the images taken for the sample with defect and the ones without defect. It was concluded that subsurface defects were detected using speckle shearography and surface roughness can also be identified using speckle contrast analysis.
Final Year Project (FYP)
Nanyang Technological University