The Temperature Dependence of the Fracture Stress of Notched Tensile Specimens

The fracture stresses of unnotched tensile specimens exhibit various temperature dependences. It is shown that such various dependences also occur in tensile tests on notched specimens. For that purpose tests were performed between -140 degrees C and +82 degrees C on notched specimens with notch root radii of 7.0, 2.0, and 0.075 mm. The observed data indicated seven temperature ranges with different temperature dependences of the fracture stress (and area reduction). These dependences were described by seven different fitting curves. The intersections of these fitting curves lead to the transition temperatures cleavage fracture - mixed fracture and mixed fracture - fibrous fracture. For notch root radii of 7.0 and 2.0 mm these tests yielded the same temperature dependences as were expected from unnotched tensile specimens. Specimens with a notch root radius of 0.075 mm showed some differences in the temperature dependence which are discussed in detail.