Biaxial stress effects in a reinforced cracked sheet

Abstract

The effect of biaxial stress on the stress intensity factor and rivet loads has been determined for a single crack in a reinforced sheet. It is shown that for a sheet reinforced by intact orthogonal stiffeners the stress intensity factor is unaffected by the stress applied parallel to the crack. In this respect its behaviour follows that of a crack in a unstiffened sheet but is contrary to conclusions drawn from previous results in the literature on biaxially stressed stiffened sheets. However, a re-analysis of these existing results shows them to be consistent with the present finding that the stress intensity factor is independent of the stress applied parallel to the crack in a sheet stiffened by orthogonal intact stiffeners. For a sheet in which a stiffener is broken across the crack line a tensile stress parallel to the crack is shown to reduce the stress intensity factor compared to that which exists for a uniaxial tensile stress only, applied perpendicular to the crackline. The opposite effect is shown to occur for a compressive stress parallel to the crack in the biaxially stressed sheet. For a cracked sheet reinforced with a patch, it is shown that the stress intensity factor will also depend on the stress applied parallel to the crack. The various effects of biaxial stress are illustrated with new results for the stress intensity factor, rivet loads, and maximum stiffener stress for a sheet having equally spaced stiffeners along line perpendicular to the crack.