Strength and Fracture Properties of Structural Steels Under Dynamic Loading

摘要

An investigation has been carried out on the stress/strain behavior near a notch tip under dynamic loading and its influence on the fracture property of structural steels. 3D FE-analysis, taking account of the strain rate effect on the flow stress, figured out that the dynamic loading elevates a local stress near the notch tip to a large extent. This was accompanied with acceleration of the strain rate in the notch tip region. Because of high-speed straining, the concentration of plastic work in the vicinity of notch tip leads to temperature rise at the notch tip. These effects contribute to fracture behavior of materials under dynamic loading. Which effect is more dominant, stress elevation or temperature rise, depends on the toughness level of the material: For a low toughness material, the near-tip stress elevation by dynamic loading raises the ductile-brittle fracture transition temperature. By contrast, the temperature rise at the notch tip will protect the initiation of brittle fracture provided the material holds superior fracture toughness.