Interferometric strain/slope rosette for static and dynamic measurements

The interferometric strain/slope rosette (ISSR) is extended from the interferometric strain gage (ISG) and the interferometric strain rosette (ISR) for measuring three derivatives of out-of-plane displacements in addition to three derivatives of in-plane displacements. The ISSR can be used for both static and dynamic measurements. The principle of the measurement is a combination of diffraction and interference of laser beams. The miniature ISSR is applicable to complex geometries that are unaccessible to conventional sensors. As six displacement derivatives are measured, components of a strain tensor and rotation can be determined. The principle and image-processing system are described. Sensitivities to rigid-body translations are thoroughly studied. The technique is noncontacting, in contrast to resistance strain gages and accelerometers, which require attachment of transducers to specimen surfaces.