Long Wavelength Defect Evaluation

This is a summary of work with B. Budiansky1 and W. Kohn 2 on the interpretation of long wavelength scattered fields from defects. The maximum information content of the long-wavelength fields is shown to consist of 22 parameters, one of which is the excess mass oM, and 21 of which are dete~mined by the excess elastic moduli tensor aC and quasi-static response properties of the defect region . It is shown that these parameters can, in principle, be determined by longitudinal to longitudinal wave scattering experiments only, and that they can provide evidence, necessarily incomplete, on the type, shape, orien- tation, and size of the defect. Particularly, whe~ ~he defect is in the form of a planar crack, it is shown that the crack orientation can be determined ' and that an approximate estimate can be made of the 1111ximum stress intensity factor that would be induced by tensile stresses acting normal to the defect plane . References 1. B. Budiansky and J. R. Rice, On the estimation of a crack fracture parameter by long-wavelangth scattering, in Preliminary Reports, Memoranda and Technical Notes of the Materials Research Council Summer Conference, July 1977, Univ. of MichiganlOiept. Materials andlMe~Engr .• ed. M. J. Sinnott, pp. 1-9. (To appear in Trans. ASME •. J. Appl. Mech.) 2. W. Kohn and J. R. Rice, Scattering of long wavelength elastic waves from localized defects in so 1 ids. in Pre 1 i mi nary Reports . . . (ibid. ) , pp. 390-416. (Submitted to J. Appl. Phys.)