An infrared interferometer for elastoplastic crack-tip field investigationof homogeneous and bimaterial beams: A study of three-dimensional effects and J-dominance

An infrared interferometer capable of performing real-time full-field nonco ntacting deformation field measurements on optically rough surfaces is prop osed as a tool for elastoplastic fracture mechanics investigations. The cho ice of the infrared wavelength allows interferometric measurements on fract ure samples with little or no surface preparation and is more tolerant of t he damage accumulation near the crack, The interferometer also bridges a se nsitivity gap among existing techniques for out-of-plane deformation measur ement First, a rigorous Fourier optics analysis is provided for the interfe rometer and the range of surface roughness that can be studied using this i nterferometer is examined. The interferometer is then used for mapping defo rmations near elastoplastically deformed cracks in aluminum beams and solde r-copper bimaterials. The regions of dominant three-dimensional effects and J-dominance are examined on the sample surface by evaluating measurements along with companion finite element analyses and the HRR fields.