文档介绍：Chaptor 6 Fracture of Metals 金属的断裂
cargo ship货船
问题的提出:构件失效、灾难性的后果
挤压制品的周期裂纹
Plastic deformation 塑性成形
surface/ internal cracks in working materials →integral failure.
加工材料出现表面/内部裂纹→整体破断
This happens in rolling轧制,extrusion挤压, drawing拉拔,forging锻造and so on.
It will largely reduce the rate of finished products and production rate成品率/生产率↓.
We concern about fracture for two reasons. One is crack’s destructive effect, the other one is that fracture is related to material’s formability .
(1)破坏; (2)成形性。
In this chapter ,we will analyze the physical essence and laws of fracture.
断裂的物理本质/规律
Definition of fracture
When metallic material deformation forereach its plastic limit , it will pletely. Then the interatomic force is damaged. 断裂-金属材料在变形超过其塑性极限—。
related subjects
断裂力学 fracture mechanics - macroscopic
Stress field 应力场
Strain field 应变场
Fracture criterion 断裂判据
断裂物理 fracture physics - microscopic
Fracture mechanism 断裂机制
Microstructure 组织
Basic types of fracture 断裂的基本类型
According to whether the metal has obvious plastic deformation before fracture, it can be sorted as following :
根据断裂前金属是否有明显的塑性变形可分为
brittle fracture 脆性断裂ψ<5%
ductile fracture 韧性断裂ψ>5%
According to the orientation relationship between fracture and acting force
按断裂面相对作用力的取向关系可分为
normal failure 正断 against to σ1
shearing failure 剪断 along the direction of maximum shear
宏观断裂
微观断裂
正断与剪断的宏观与微观形式
According to crack trend in microscopic view
从微观上按照裂纹的走向可分为
transgranular fracture 穿晶断裂/晶间~
intergranular fracture 沿晶~ grain晶粒
穿晶断裂
沿晶断裂
Fracture along grain-boundary in polycrystal material
多晶材料沿晶界发生的断裂
- 沿晶韧性断裂-晶界弱化,出现韧窝 dimple
- 沿晶脆性断裂 intergranular precipitated brittle continuous film -沿晶析出脆性连续膜