Measurements of crack-tip strain using laser interferometer

• Main Authors: Hsiung-Nien Feng, 馮熊年
• Other Authors: Sheng-Hsiung Shih
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/31758809652609546922

碩士 === 國立臺北科技大學 === 製造科技研究所 === 92 === This thesis introduces the Michelson, Moire’, and Savart shearing interferometers and adopts them as the tools for determining the strain fields at a crack tip. The crack tip strain field measurements using Savart shearing interferometer is a new concept and first proposed in this research, thus the description and application of the Savart shearing interferometer are more detailedly. The Savart shearing interferometer consists of a laser source, Savart polariscope, polarizer, and CCD camera. Where the Savart polariscope is the shearing device that divides the incoming beam into two parallel beams whose polarizations are orthogonal. Thus as a beam coming from the object and passing through the Savart polariscope and polarizer will generate a shearing interference pattern on the CCD camera. The phase-shifting mechanism is to rotate the Savart polariscope about an axis normal to the plane includes the two parallel beams so the phase of the interference pattern can be shifted. We adopt five-steps phase-shifting Michelson, Moire’, and Savart shearing interferometers to determine the crack tip strains and compare the measurement results with each other. The comparisons agree the validity and applicability as the Savart shearing interferometer is applied for the crack strain measurements.