1. -simple state of stress
Plastic deformation
-simple state of stress

2. Flow stress of metals Flow stress
For understanding the stresses and the forces
The concept of flow stress
The study of plastic deformation under conditions (a simple state of stress)
Uniform or homogeneous deformation condition
Flow
stress
The metal starts
“Flowing”
“deforming plastically”
The applied stress : “yield stress”

3. Flow stress of metals Why the flow stress? The forming load
(a) part geometry
(b) friction
(c) the flow stress of the deforming material
The flow stress is influenced by
Factors unrelated to the deformation process
: chemical composition, metallurgical structure, phases, grain size, segregation,
the prior strain history
Factors related to the deformation process
: temperature of deformation, degree of deformation (strain), rate of deformation
(strain rate)

4. Flow stress of metals Expression of the flow stress Cold Hot
at various elevated temp.

5. Tensile test In the most common use
Useful for designing only component
Valid for relatively small amount of plastic strains

6. Tensile test
The criterion for necking : L should be the maximum

7. Tensile test
= zero

8. Tensile test

9. Compression test The flat platens The cylindrical billets
At the same temperature
(die chilling prevented)
No limit of compression strain

10. Ring test
Compressing a flat ring-shape specimen
To a known reduction

11. 감사합니다