Causes of brittle fracture formation in gray iron castings
Release time:
2024-03-12 10:03
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The material of gray iron castings will produce fracture phenomenon when the stress generated under the action of external force exceeds its own fracture strength, and fracture is one of the important factors for the failure of mechanical parts.
According to the analysis of relevant experts, the fracture process of gray iron castings is more complicated, but on the whole, it has to go through three stages of internal crack initiation, crack expansion and fracture. The fracture line without obvious plastic deformation belongs to brittle fracture. Under the action of normal stress, brittle fracture is the fracture formed by the separation of the material along the reasonably weakest crystallographic plane between atoms, also known as cleavage fracture.
Regarding the crack nucleation mechanism of brittle fracture in gray iron castings, the dislocation accumulation theory holds that the moving dislocations are blocked by grain boundaries and impurity phases after the material is stressed, resulting in dislocation accumulation. When the stress concentration formed by the plug-in group is checked for material strength, cracks are initiated in the front of the plug-in group, and the cracks expand at a very fast speed before brittle fracture.
According to the stress relationship analysis, when the yield stress of the material is greater than the crack nucleation stress and the fracture stress at the same time, once the crack is initiated, it will fracture without plastic deformation.
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