määr, millest alates pingekontsentratsiooni olemasolul (nt sälk, järsk ristlõike üleminek, pragu) suureneb kalduvus haprale purunemisele (vt pingekontsentratsioon), the extent to which the sensitivity of a material to fracture is increased by presence of stress concentration, sush as a notch, a sudden chande of cross-section, a crack (see: stress concentration)