New Modeling Technique for Pre-Strained Heat Treated Aluminium Sheets

Transcription

1 New Modeling Technique for Pre-Strained Heat Treated Aluminium Sheets Rajarajan Govindarajan 1, Martin Zubeil 2, David Lorenz 3, Thomas Borrvall 4 1 -Mercedes-Benz Research and Development India 2 -Daimler AG, Germany 3 -DYNAmore GmbH, Germany 4 -DYNAmore Nordic AB, Sweden

2 Agenda Introduction Intermediate Induction Heat Treatment or Heat assisted forming Material behaviour New Modelling Technique Experiments and validation Cross die deep drawn cup Conclusion and Discussion Slide 2

3 Lightweight construction Steel Mild High strength Modern high strength Ultra high strength Ultra high strength (hot formed) Aluminium Plastics Hood Side wall Fender Body-in-White BR W204 Slide 3

4 Induction heat treatment (IIHT): Process principle Slide 4

5 Intermediate Induction Heat Treatment Pre-forming Conventional cold forming Induction heat treatment Temperature ~ 350 c Time ~ 3 5 secs. Final forming Conventional cold forming 1 st stage Part is pre-formed to approx. 90% of its final shape 2 nd stage Part is heated up locally with an induction heating tool to approx c for about 3 to secs. 3 rd stage Part is cooled down to room temperature and then formed to final shape Slide 5

6 Induction heat treatment (IIHT): Material behavior Slide 6

7 Material behavior: AA5182, t=1.5mm, Flow curves 400 σ 0% & RT Effect of pre-strain and heat treatment ε 300 True stress (Mpa) % & 350 c 10% & 350 c 15% & 350 c True strain Slide 7

8 Material behavior: AA5182, t=1.5mm Stress σ (Mpa) 100 Uniform elongation Yield strength 6 Elongation ε (%) Temperature ( C) Pre-strain - 10% Slide 8

9 Induction heat treatment (IIHT): Simulation Slide 9

10 Modeling intermediate heat treatment 3 BC - Before closing* - Conventional cold forming Slide 10

11 Modeling intermediate heat treatment Slide 11

12 Modeling intermediate heat treatment Print σ vs. ε p -ε pre Slide 12

13 Modeling intermediate heat treatment Slide 13

14 Induction heat treatment (IIHT): Validation with Cross die Slide 14

15 Cross die Experiments and Numerical simulations Slide 15

16 Heating zone Temperaturen bei der induktiven Erwärmung am vorgezogenen Cross Die lagen zwischen 250 C und maximal 350 C Slide 16

17 Cross die - Experiments Cold forming Draw depth - 47mm Induction heat treatment Draw depth - 80mm Slide 17

18 Simulation procedure Pre-forming Springback Heat transfer modeling Post forming Calculation of heat affected zone is very important Heating simulation is required Temp. ( C) Inductor width 23 mm HAZ Width (mm) Max. temp. 341 C Slide 18

19 Validation Thickness distribution (mm) 2.2 Section A-A Thickness (mm) Simulation Experiment Draw depth = 80mm Length (mm) Slide 19

20 Validation 2.2 Section B-B Thickness (mm) Experiment Simulation Length (mm) Slide 20

21 Conclusion Formability of Al-Mg alloy AA5182 has greatly enhanced through Heat assisted forming The developed modeling technique is suitable for both Tailor heat treated blanks (THTB) and pre-strained components. It is also suitable for a variety of automotive aluminium alloys. Thermal simulation of heat treatment results in proper prediction of heat affected zone. Localized heating often results in part distortions due to residual stress gradient. Further research is needed to identify the capability of this technique to capture this effect. Slide 21

22 Thank you for your attention! Slide 22