Fatigue Performance of AHSS GMAW Lap Joints

Transcription

1 Fatigue Performance of AHSS GMAW Lap Joints Dave Anderson Chuck Porter AISI Yan (Jack) Sang Chonghua (Cindy) Jiang AET Integration, Inc.

2 Presentation Contents Project Background. Review of Test Results and Analysis. Summary. Next Step.

3 Project Objective Compare GMAW weld fatigue life. Mild steel and AHSS Similar joint geometry Evaluate the effects on weld fatigue life. Weld geometry Base steel strength Welding wire

4 Project Sponsors

5 Test Factors Materials 2.0mm Mild Steel Bare, DP600 Bare, DP780 Bare 2.0 mm Mild Steel HDGI, DP600 HDGI, DP780 HDGA 4.0mm Mild Steel Bare Filler Metal ER70S-3, ER80S-D2 Geometry Min. acceptable Improved

6 Methodology Develop two distinct weld geometries: Acceptable and Improved. Compare fatigue response for mild steel and AHSS joints. Find statistical significance of weld geometry, steel strength, filler metal strength. Utilize FEA modeling to evaluate the effects of weld geometry.

7 Related AET Capability

8 Fatigue Testing Setup

9 Weld Profile 2.0mm Mild Bare, Acceptable vs. Improved Mild Steel, Uncoated, Acceptable Geometry Mild Steel, Uncoated, Improved Geometry

10 Weld Profile 2.0mm DP780 Bare, Acceptable vs. Improved DP780, Uncoated, Acceptable Geometry DP780, Uncoated, Improved Geometry

11 Weld Profile 2.0mm Mild HDGI, Acceptable vs. Improved Mild Steel, HDGI, Acceptable Geometry Mild Steel, HDGI, Improved Geometry

12 Fatigue Performance 2.0mm Mild Bare Fatigue Life, 2.0mm Mild Bare Wire Improved Geometry 70 Wire Acceptable Geometry 80 Wire Improved Geometry 80 Wire Acceptable Geometry Stress Range (MPa) 100 R= Cycles to Failure

13 Fatigue Performance 2.0mm DP600 Bare Fatigue Life: 2.0mm DP600 Bare Nominal Stress Range (MPa) Wire Improved Geometry 70 Wire Acceptable Geometry 80 Wire Improved Geometry 80 Wire Acceptable Geometry R= Cycles to Failure

14 Fatigue Performance 2.0mm DP780 Bare Fatigue Life, 2.0mm DP780 Bare Nominal Stress Range (MPa) Wire Improved Geometry 70 Wire Acceptable Geometry 80 Wire Improved Geometry 80 Wire Acceptable Geometry R= Cycles to Failure

15 Fatigue Performance 2.0mm Mild HDGI Fatigue Life, 2.0mm Mild GI Nominal Stress Range (MPa) Wire Improved Geometry 70 Wire Acceptable Geometry 80 Wire Improved Geometry 80 Wire Acceptable Geometry R= Cycles to Failure

16 Fatigue Performance 2.0mm DP600 HDGI Fatigue Life, 2.0mm DP600 GI Nominal Stress Range (MPa) Wire Improved Geometry 70 Wire Acceptable Geometry 80 Wire Improved Geometry 80 Wire Acceptable Geometry R= Cycles to Failure

17 Fatigue Performance 2.0mm DP780 HDGA Fatigue Life, 2.0mm DP780 GA Nominal Stress Range (MPa) Wire Improved Geometry 70 Wire Acceptable Geometry 80 Wire Improved Geometry 80 Wire Acceptable Geometry R= Cycles to Failure

18 Fatigue Performance 70 Wire 2.0mm Bare Steel Acceptable Geometry 70 Wire 2.0mm Bare Steel Acceptable Geometry Nominal Stress Range (MPa) Mild DP600 DP780 R= Cycles to Failure

19 Fatigue Performance 70 Wire 2.0mm Bare Steel Improved Geometry 70 Wire 2.0mm Bare Steel Improved Geometry Nominal Stress Range (MPa) Mild DP600 DP780 DP780 Run Out R= Cycles to Failure

20 Fatigue Performance 80 Wire 2.0mm Bare Steel Acceptable Geometry Fatigue Life, 80 wire 2.0mm Bare Steel Acceptable Geometry Nominal Stress Range (MPa) Mild Bare DP600 Bare DP780 Bare R= Cycles to Failure

21 Fatigue Performance 80 Wire 2.0mm Bare Steel Improved Geometry 80 Wire 2.0mm Bare Steel Improved Geometry 150 Mild DP600 DP780 Nominal Stress Range (MPa) 100 R= Cycles to Failure

22 Why the results are different from some other studies? Mixed Geometry, Mixed Wire, 2.0mm Bare Steel Nominal Stress Range (MPa) Mild DP600 DP780 DP780 Run Out R= Cycles to Failure

23 Why the results are different from some other studies? 70 Wire 2.0mm Steel Nominal Stress Range (MPa) M ild Bare A cceptable Geometry DP780 Bare Improv ed Geometry DP780 Bare Run O ut Cycles to Failure

24 Fatigue Life Regression Analysis using Weibull Distribution Log (Fatigue Life) is analyzed Probability Plot for SResids of N Smallest Extreme Value - 95% CI Censoring Column in Censor - ML Estimates Percent Standardized Residuals 0 2

25 3D Bar Chart 70 Wire Bare Steels at 1200 lb. loading D esig n-expert Software Transformed Scale Log 10(Fatig ue) X1 = A: Geometry X2 = B: M aterial 6.7 Log10(Fatigue) D P780 Improved D P600 B : Ma te ria l M ild Steel Acceptable A: Geom etry

26 Static FEA Analysis

27 Static FEA Analysis Weld toe stress MPa Oak Ridge National Lab (Dr. Zhili Feng) s analysis using notch stress theory indicates that improvement in weld toe stress results in more fatigue life improvement for AHSS than conventional steel.

28 Summary Weld profile can be improved by welding parameter adjustments. Weld profile influence weld fatigue life. Weld profile improvement has more significant impact on AHSS weld fatigue life than on mild steel. Base metal strength appears to influence weld fatigue life. Higher strength wire in this study does not appear to improve AHSS weld fatigue life.

29 Acknowledgement Dave Anderson, Chuck Porter, American Iron and Steel. Tom Natale, AK Steel. Andy Lee, Elliot Biro, Dofasco. Benda Yan, Min Kuo, Mittal Steel. Alex Von Rogov, SeverStal, USA. Zhili Feng, Oak Ridge National Lab.

30 Q & A