A mild structural steel of the kind used in ship hulls has yield stress and

PHYSICS · Multi-part · Fermi University Physics · Fluids & Continuum Physics · Solid continuum mechanics and complex fluids · Solid continuum mechanics and complex fluids

Bending, Ringing, Breaking and Flowing, Ch Fracture: stress concentration, cracks and toughness

Problem

A mild structural steel of the kind used in ship hulls has yield stress σY=350 MPa\sigma_Y = 350\,\mathrm{MPa} and, at its service temperature, a fracture toughness of about KIc=60 MPa m1/2K_{Ic} = 60\,\mathrm{MPa\,m^{1/2}}, typical of a tough ductile steel. ((a)) Estimate the plane-stress crack-tip plastic zone size rpr_p at fracture. ((b)) Using the fact that the plane-strain zone is smaller by the factor of about 66 that Section 8.6 found for ν=0.3\nu=0.3, estimate the plane-strain plastic zone size. ((c)) Estimate the minimum specimen thickness for a valid plane-strain toughness test on this steel, using the standard rule that the thickness must be at least 2.5(KIc/σY)22.5(K_{Ic}/\sigma_Y)^2.

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