Effect of Notch on Strength and Ductility of a Martensitic Stainless Steel in Tensile Test

Tensile properties characterize the quality of the product and forecast the performance for design purpose. There is no clear evidence that the tensile results obtained from a different type of specimen are comparable or interchangeable. This study investigates the effect of notch on the tensile properties of stainless steel by conducting uniaxial tensile tests on notched and round specimens at room temperature. A flat specimen was also tested to compare the tensile properties of notched and round specimens. The ultimate tensile strength (UTS), while being higher for notched specimen, was found to be consistent with the type of specimens. The tri-axial stress at the notch root was responsible to the increased UTS of the notched specimen. The higher strain hardening in flat specimen attributed to the reduced ductility. The tensile results of flat stainless steel specimen were found to be more consistent with the standard (round smooth) specimen. The formation of dimples on the fractured surfaces identified a ductile type of fracture for all three types of tensile specimens. Local strain hardening and cracking in notched specimen might have resulted in facets on the fractographs.