Weibull Effective Volumes and Surfaces for Cylindrical Rods Loaded in Flexure
George D. Quinn
Formulas are given for the effective volumes and effective surfaces for cylindrical rods loaded in flexure. Strength scaling for specimen size usually depends upon whether the flaws are volume or surface distributed. Flexural loadings of rods of constant diameter are an unusual exception. The ratio of 3-poing flexural strengths to 4-point flexural strengths is dependent of whether the flaws are volume or surface distributed. Rods tested in flexure do not expose much material to the maximum stresses. Large rods produce comparable strengths to common standard sized rectangular bend bars for volume flaws. For surface flaws, smaller rectangular bar specimens actually have larger effective surfaces.