1. Qualification of sheets for cold forming
Advanced material and technologies, MSc
2017

2. Qualification of sheets for cold forming
Vertical (or normal) anisotropy (plastic strain ratio or Lankford ratio):
Average vertical anisotropy:
Planar anisotropy:

3. Qualification of sheets for cold forming
Strain-hardening exponent (n):

4. Qualification of sheets for cold forming
Formability of sheets (Lillet-diagram), in case of steels:
- large r → decrease of thinning,
- low Δr → lower planar anisotropy.
I. High quality sheets, suitable for complex forming processes (good for stretch and deep drawing),
II. Sheets mainly for deep drawing (lower thinning behaviour),
III. Sheets mainly for stretching,
IV. Low quality sheets, less suitable for cold forming.

5. Qualification of sheets for cold forming
Forming Limit Diagram (FLD):

6. Qualification of sheets for cold forming
Forming Limit Diagram (FLD):

7. Qualification of sheets for cold forming
Forming Limit Diagram (FLD):

8. Qualification of sheets for cold forming

9. Qualification of sheets for cold forming

10. Qualification of sheets for cold forming

11. Qualification of sheets for cold forming
Examples:
1. In a sheet forming process, the following maximum strains are expected on a part of the component: φ1= 0,26 and φ2= 0,1. Is there any possibility for crack initiation on this part? Please determine it by using the Forming Limit Diagram (FLD) of the given alloy signed by AW6016-T4!
2. In a deep drawing process it is expected on the basis of preliminary experiments, that on a part of the component the strain reaches 0,2 in a plane strain state. Is there any possibility for crack initiation on this part? Please determine it by using the FLD of the given alloy signed by AA6111!
3. In a deep drawing process it is expected on the basis of preliminary experiments, that on a part of the component the strain reaches 0,2 in a plane strain state. The thickness of the sheet is 1 mm. The yield strength for the base material should not be less than 80 MPa and the minimum elongation at breakage should be 20% (referring to 50 mm gauge length). With the use of FLD-s and quality tables of alloys specify the material quality with which the forming process can be carried out!
4. A finite element analysis of a sheet forming process has exhibited, that on a part of the component biaxial tension is occurred in which the strain reaches 0,25, while in the other part plane strain is occurred in which the strain reaches 0,2. With the use of FLD-s of given alloys specify the material quality with which the forming process can be carried out, if the tensile strength is not less than 180MPa!