Dent Performance of Galvanized Coated Steel Grades Used in Automotive Closure Panels

Transcription

1 Dent Performance of Galvanized Coated Steel Grades Used in Automotive Closure Panels Gary Boudreau Dofasco Inc 1

2 Objective hcompare performance of grades, thickness and coating type hpredict dent performance based on thickness and properties ha/sp pie pan samples used to examine dent performance 2

3 Overview hexperimental Procedure hgrade and Thickness Effects hstrain Effects hdent Load versus thickness x YS hconclusions 3

4 Grades and thickness tested Table 1 Grade/Thickness (mm) Thick 1 Thick 2 Thick 3 IF(GI) IF(GA) DQ BH BH DP

5 Mechanical Properties Grade Thick (mm) YS (MPa) UTS (MPa) T E n R-Bar (20%) IF, GA IF, GA IF, GA IF, GI IF, GI IF, GI n based on longitudinal properties, 10 to 20 % elongation 5

6 Mechanical Properties Grade Thick (mm) YS (MPa) UTS (MPa) T E n R-Bar (20%) DQ DQ DQ BH BH BH BH DP n based on longitudinal properties, 10 to 20 % elongation 6

7 7 Test Facility

8 Test Facility Indenter 8

9 Dent Test Equipment Load versus displacement curves for quasi-static and dynamic tests Initial stiffness of panel Load at specified dent depth Laser scanning system to create image of dent profile and calculate both dent area and volume 9

10 Dent Test Equipment Actuator speeds comply with A/SP procedure for evaluating dent resistance of automotive body panels Standard static test velocity mm/sec (0.032 in/sec.) Minimum dynamic test velocity 894 mm/sec (35.2 inch/sec) 10

11 Dent Test Equipment 11

12 Procedure A/SP Pie-pans 5 Samples Lock bead 940 mm punch radius Lock bead 12

13 Sample Dimensions Lock bead 13

14 Results Figure 4 BH240 (M3, 0.80 mm)load Displacement curve 14

15 Results Ranking Ranking of Materials 15

16 Figure 6 Effects of Thickness on Dent Load BH240 BH210 DQ IF Dent Load (0.8 mm thick) BH N BH N IF 127 N 16

17 Figure 7 Effect of Thickness on Dent Load Note: ALL excludes DP600 data 277@0.8mm DP600 ALL 17

18 Strain Effects Dent Performance Grades Versus Strain 18

19 Figure 8 Effect of Formed Thickness on Dent Load 19

20 Figure 9 Effect of Formed Thickness, Grade, Strain 20

21 Figure 10 Effect of Formed Thickness and Strain on Dent Load - BH240 Only Trend Low more tests required 21

22 Figure 11 Yield Strength after strain & bake MPa Virgin 1% 2% 3% 0 IF-.63 IF-.70 IF-.81 DQ-.64 DQ-.69 DQ

23 Figure 12 Yield Strength after strain and bake MPa Virgin 1% 2% 3% BH BH BH BH DP

24 Comparing Dent Performance DP600 dent resistance depends on pre-strain DP600 not supplied as exposed but DP500 in development, DP500 lower mechanical properties, better formability Next compare DP500 mechanical properties with DP600 24

25 Mechanical Properties DP500/DP600 Grade Yield (MPa) UTS (MPa) DP500 Typical DP600 Actual Tested

26 Initial Stiffness & Coating Effects Effect of Coating on Dent Load Initial Stiffness Versus Thickness 26

27 Figure 13 Effect of Coating on Dent Load by Thickness 0.04 mm difference 27

28 Figure 14 Effect of Thickness and Grade on Initial Stiffness 28

29 Predicting Dent Performance Dent Load Versus YS Times Thickness Power

30 Source- Studies on Static Dent Resistance, Revue Metallurgie, April, 1980, Y Yutori, S Nomura, I Kokubo, H Ishigaki Note: Based on Virgin Yield Strength 30

31 Note: Based on post form and bake yield strength 31

32 Conclusions Bake hardenable grades improve dent performance over IF grades by 25 to 40 percent Dual Phase significantly improves dent performance Dent performance of DP600 improves with pre-strain 1%-221N 2%-255N 3%-354N 32

33 Future Work Test DP500 and BH300 Test aluminum T6022-T4 & 6111-T4 (0.80, 0.90,1.0 mm) FEA model 33

34 Solutions in Steel