Notch Effect of Materials： Strengthening or Weakening

Notch is a very important geometry with widespread applications in engineering structural components. Finding a universal equation to predict the effect of notch on strength of materials is of much significance for structural design and materials selection. In the present work, we tried to find this universal equation from experimental results of metallic glasses （MGs） and other materials as well as theoretical derivations based on a universal fracture criterion （Qu and Zhang, Sci. Rep. 3 （2013） 1117）. Experimental results showed that the notch effect of the studied MG was affected by the notch geometry characterized by the stress concentration factor Kt. As Kt becomes smaller, the notch strength ratio （NSR, which is the ratio of nominal ultimate tensile strength （UTS） of the notched sample to UTS of the unnotched sample） increases. By comparing MGs with other materials like brittle ceramics and ductile for ductile metals but smaller for brittle effect on strength of materials： NSR = equation was found to be consistent with crystalline metals, we find that when Kt is same, the NSR is larger ceramics. Theoretically, we derived a universal equation for notch M/Kt, where M is a constant related to materials. This universal the experimental results.