In-Situ Measurements of three-dimensional displacement fields in shear crack growth using phase-shifted speckle interferometry

摘要

A three illumination beam, phase-shifted speckle interferometry system is used to measure three-dimensional surface deformation fields to study the mechanics of cracks loaded in shear. The interferometer, which is mounted to the actuator of a servohydraulic loading machine, is augmented with a piezoelectric phase shifter to obtain a sequence of differential phase maps over small load increments. This avoids problems with speckle decorrelation and provides more detailed information about the phenomena of interest. The displacement fields were accumulated relative to the unloaded state by sampling at appropriate locations in the incremental fields to optimize spatial resolution and compensate for large rigid body motions. Features of the effect of fracture surface interference on a shear-loaded crack inferred from the displacement fields are described.