First Application of a New Optical Rosette for Strain Measurements

Abstract

Interferometric strain/slope rosette technique is an optical technique based on laser interferometric. It has advantages such as short gage length, non-contacting, thermal resistant, measuring both in-plane strains and out-of-plane deformations’ slopes simultaneously. Six-faced delta rosette has been always utilized. In this paper, a new type of rosette, the eight-faced rectangular rosette was first applied. Besides the advantages described above, the new rosette has the advantage for measuring strains/slopes directly in two orthogonal directions. This avoids the strain transformation process which was generally required by the delta rosette. Also, since the rectangular rosette measures strains directly along the two objective directions instead of measuring in the direction with an angle, higher sensitivity will be achieved. Two preliminary tests using the new rosette were presented in this paper. First, it was adapt to measure strains in a compression test of an aluminum block at each loading step. Resistance strain gage rosette was also applied for evaluating the result. Second, the new rosette was introduced for measuring the real time strain during an arc welding process. Strain history during the welding process was successfully obtained and compared well with results using delta rosettes.