Macroscopic features of the dimple fracture

The effect of the steel material on the external force is due to the strong sliding displacement and the accumulation of many voids in the deformed area. Or because the inclusions are broken, the inclusions and the matrix metal interface are broken to form many tiny holes. The pores continue to grow under the action of external force, and accumulate to form cracks until the final separation. This type of fracture is called microporous aggregate fracture, and the fracture is called the fracture of the dimple.

Figure 3-1 8740 steel tensile fracture fiber area

The macroscopic features of the fracture of the dimple are characterized by fibrous and sheared lips. In the tensile fracture of a smooth round specimen, the fiber zone is generally located in the center of the fracture and is rough, see Figure 3-1. The fiber zone is composed of a myriad of fibrous "small peaks" with a small bevel and an axis of tension of approximately 45°. Single-phase metal, ordinary carbon steel, and pearlitic steel tensile fractures generally have such characteristics, and the high-strength martensitic steel fiber region also has a ring-like pattern. Longitudinal and relatively regular zigzag, is a circular shear ridge.

There is also a fiber zone on the impact fracture, see Figure 3-2(a)(b).

Figure 3-2 Schematic diagram of impact fracture and impact fracture _

a) Schematic diagram of three fracture zones of impact fracture; (b) Impact fracture

The impact fracture of the higher plastic material often has two fiber regions, and the impact fracture diagram is shown in Figure 3-3. The surface of the fiber area is dark and has no metallic luster.

Figure 3-3 Schematic diagram of four-zone impact fracture

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