A notch root radius to attain minimum fracture loads in plates weakened by U-notches under Mode I loading

The paper deals with the minimum value of a fracture load, with respect to the notch rootradius, in plates weakened by u-notches under mode i loading. it has been found that the fracture loadhas a minimum value at a critical value of the notch root radius (), using four criteria, namely, meanstress (ms), maximum tangent stress or point stress (ps), critical strain-energy (cse) and averaged strain-energy density (ased). using a characteristic length (lch), which is a function of material properties, theresults showed that the dimensionless critical notch root radius .=lch/cr depended on w=a ratio (thespecimen width to the notch depth), poisson ratio, and loading condition (tensile or bending loading)under mode i loading. in other words, according to these criteria, a notch root radius different from zeroexists, providing a minimum fracture load. therefore, a crack is not more dangerous rather than a u-notchunder mode i loading. this critical notch root radius is important for a quasi-brittle material, but maynot be significant for brittle ones in practical engineering situations. good agreement was found betweentheoretical predictions and experimental results on al356-t6.