An Infrared Interferometer for Elastoplastic Crack-Tip Field Investigation of Homogeneous and Bimaterial Beams: A Study of Three-Dimensional Effects and J-Dominance

An infrared interferometer capable of performing real-time full-field noncontacting deformation field measurements on optically rough surfaces is proposed as a tool for elastoplastic fracture mechanics investigations. The choice of the infrared wavelength allows interferometric measurements' on fracture samples with little or no surface preparation and is more tolerant of the damage accumulation near the crack. The interferometer also bridges a sensitivity gap among existing techniques for out-ofplane deformation measurement. First, a rigorous Fourier optics analysis is provided for the interferometer and the range of surface roughness that can be studied using this interferometer is examined. The interferometer is then used for mapping deformations near elastoplastically deformed cracks in aluminum beams and solder-copper bimaterials. The regions of dominant three-dimensional efJ'ects and J-dominance are examined on the sample surface by evaluating measurements along with companion finite element analyses and the HRR fields.