Page 157 - T. Anderson-Fracture Mechanics - Fundamentals and Applns.-CRC (2005)

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Elastic-Plastic Fracture Mechanics 137

FIGURE 3.30 Effect of specimen geometry on critical J values for initiation of ductile tearing. Taken from
Joyce, J.A. and Link, R.E., ‘‘Effect of Constraint on Upper Shelf Fracture Toughness.’’ Fracture Mechanics,
Vol. 26, ASTM STP 1256, American Society for Testing and Materials, Philadelphia, PA (in press).

3.6.1 THE ELASTIC T STRESS
Williams [23] showed that the crack-tip stress fields in an isotropic elastic material can be expressed
as an infinite power series, where the leading term exhibits a 1 r singularity, the second term is constant
with r, the third term is proportional to r , and so on. Classical fracture mechanics theory normally
neglects all but the singular term, which results in a single-parameter description of the near-tip

FIGURE 3.31 Effect of specimen geometry on tearing modulus at ∆a = 1 mm. Taken from Towers, O.L. and
Garwood, S.J., ‘‘Influence of Crack Depth on Resistance Curves for Three-Point Bend Specimens in HY130.’’
ASTM STP 905, American Society for Testing and Materials, Philadelphia, PA, 1986, pp. 454–484.