DETERMINATION OF DUCTILE FRACTURE (DUCTILITY) AT ANY STRESS STATE BY MEANS OF THE UNIAXIAL TENSILE TEST

Various ductile fracture criterions are discussed. The proposed new ductile fracture criterion is developed from the theory of fracture toughness under different mean stress from the tensile test. The elongation at fracture decreases linearly with increase of depressive mean stress, the decreasing gradient being determined by the line from the yield point to the ultimate tensile point in the uniaxial tensile test. The material endures elastic and plastic deformation to the point where the mean stress equals the maximum sustainable equi-cohesive bonding stress, the latter stress decreasing as the temperature rises, as time elapses, as the depressive mean stress rises and as the material suffers damage by plastic deformation.