Specific application method for determining the strength and fracture toughness of metal materials

The elastic-plastic fracture of metal components with cracks is an interesting structural behavior because of the sizable crack-tip plastic zone and its strong interactions with the structural boundaries and load conditions. These complex interactions lead to constant elastic-plastic fracture phenomenon that does not exist normally. Currently, there are several restrictions, such as specific height, thickness, initial crack length, loading fixture, and loading method, on the test specimens to determine the fracture toughness of metal materials. Considering the plastic zone at the crack tip, it is proposed that the elastic-plastic fracture phenomenon of metals can be predicted entirely by two basic material properties, tensile yield strength and fracture toughness. A 40 mm wide plate is used to test ordinary carbon steel Q235B, low alloy carbon steel Q345B and aluminum alloy 6061 under tension. The initial cracks introduced through wire-cutting were 4, 8, 12, 16, 20, 24, and 28 mm in dimensions with the initial notch length to the width ratios of 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, and 0.7. Based on the elastic-plastic fracture model, the specific application method for determining the strength and fracture toughness of metal materials was realized, and the complete failure curves of three metal materials were determined. A cru-cial link between the structural behavior and material parameters of metal materials was established, which can predict the yield load of actual large-scale metal structures based on the elastic-plastic fracture model.