title: Mechanical stress measurement by an achromatic optical digital speckle pattern interferometry strain sensor with radial in-plane sensitivity: experimental comparison with electrical strain gauges.
abstract: This paper shows the optical setup of a radial in-plane digital speckle pattern interferometer which uses an axis-symmetrical diffractive optical element (DOE) to obtain double illumination. The application of the DOE gives in-plane sensitivity which only depends on the grating period of the DOE instead of the wavelength of the laser used as illumination source. A compact optical layout was built in order to have a portable optical strain sensor with a circular measurement area of about 5 mm in diameter. In order to compare its performance with electrical strain sensors (strain gauges), mechanical loading was generated by a four-point bending device and simultaneously monitored by the optical strain sensor and by two-element strain gauge rosettes. Several mechanical stress levels were measured showing a good agreement between both sensors. Results showed that the optical sensor could measure applied mechanical strains with a mean uncertainty of about 5% and 4% for the maximum and minimum principal strains, respectively.
authors.affiliation: Laboratório de Metrologia e Automatização, Universidade Federal de Santa Catarina, CEP 88040-970, Florianópolis, Santa Catarina, Brazil. matiasviotti@gmail.com
authors.forename: Matias R
authors.initials: MR
authors.lastname: Viotti
authors.forename: Armando
authors.initials: A
authors.lastname: Albertazzi G
authors.forename: Walter A
authors.initials: WA
authors.lastname: Kapp