Un-Constrained Models Comparison For

1. Un-Constrained Models Comparison For Elastic Roof – Production Roof – Strong Pillars Properties; Roadbed Weights & Speeds Jan 27, 2011 Prepared by: Fadi Tahan tahan@ncac.gwu.edu (703) 726-8327

2. Study Overview • FE Model • Model Validation to Static Tests (NHTSA test number C0139 & C0140) • Un-Constrained Model Set up • Different Roof Property Simulations • Different Roadbed Weight Simulation • Deformable Roof • Elastic Roof • Different Roadbed Speed Simulation • 145° Initial Roll Angle • 180° Initial Roll Angle

3. FEA Model • The Finite Element model of a 2003 Ford Explorer was used • The suspensions, drivetrain and engine were removed to reduce the model (shown in yellow) • The weight and inertia of these parts were replaced by adding concentrated mass and inertia elements at six points on the ladder frame (shown in red) Reduced Model Full Model

4. Model Validation - Based on FMVSS 216 Tests Validation to NHTSA test number C0139 Validation to NHTSA test number C0140 5° Pitch; 25° Roll 10° Pitch; 45° Roll

5. Roof Material Properties Effect On Un-Constrained Model (Elastic Roof – Production Roof – Strong Pillars Properties)

6. 3 Different Roof Models – Material Change • Elastic Roof Model; SWR is measured to be 3.9 • Components shown in blue have pure elastic properties (Properties shown in next slide) • Production Roof Model; • (No material change) SWR = • Strong Pillars & Production Roof Rails Model; SWR = • Components shown in green are made from DF140T (Properties shown in next slide) E= 200GPa With No Yielding Strong Roof & Production Roof Rails Materials E= 200GPa; Yield at ~775 MPa

7. Material Characteristics Based on Arcelor-Mittal Steels Yield (True) Stress: ~ 775 Mpa Maximum Plastic Strain: ~ 13.3% E= 200GPa Yield (True) Stress: N/A Plastic Strain: N/A E= 200GPa What SWR?

8. U-C Model – Setup ISO View Front View Side View

9. Model Setup - Roadbed Dimension 2800 mm (~ 110 in – 9 ft) 4550 mm (~ 180 in – 15 ft) The roadbed weight is 3183 kg (7000 lbs) Vehicle weight is 2255 kg ( 4971 lbs) The roadbed surface is made of wood of 25.4 mm (1 in) thick

10. U-C – Roadbed Normal Force Vs Roll Angle Roof Material Variation Production Elastic Strong

11. U-C – Roll Rate Vs Roll Angle Roof Material Variation Production Elastic Strong Filtered Curves (SAE 060)

12. U-C – Passenger & Driver Intrusion Characteristics Roof Material Variation Production Elastic Strong 0.271 m 0.223 m

13. U-C – Passenger & Driver Intrusion Characteristics Roof Material Variation Production Elastic Strong

14. U-C Animation – Elastic Roof Vs. Strong Pillars

15. U-C – Elastic Roof Vs. Strong Pillars Overlay Elastic Roof Model & Strong Pillars Model Overlaid on top of each other (t = 0 s) Roof Crush at ~ 215° Roll Angle (t = 0.3 s) Roof Crush at ~ 195° Roll Angle (t = 0.2 s)

16. Conclusion For Different Roof Properties It is assumed that using an elastic roof model can be used for simplification for the rollover parametric study since: The roadbed normal force for the strong pillars model follows similar pattern as the elastic model • The roof crush mode is attributed to the location of the buckling at the structure or excessive elasticity for elastic model • The driver side intrusion for the strong pillar model is only 21% more than the elastic model

17. Roadbed Weight Effect On Un-Constrained Model (4 Different Weights)

18. U-C Model – Setup ISO View Front View Side View

19. Model Setup - Roadbed Dimension 2800 mm (~ 110 in – 9 ft) • Four different roadbed weights were investigated: • 2255 kg (4971 lbs) Similar weight of the vehicle with initial roadbed speed of 6.7 m/s • 3183 kg (7000 lbs) Baseline analysis with initial roadbed speed of 6.7 m/s • 4183 kg (9222 lbs) 1 ton more than the baseline model with initial roadbed speed of 6.7 m/s • 3183 kg (7000 lbs) with constant roadbed speed (assumption made to cover heavy roadbed weight) 4550 mm (~ 180 in – 15 ft)

20. Roadbed Force, Roll Angle & Intrusion Characteristics Comparisons Deformable Roof

21. U-C – Roadbed Normal Force Vs Roll Angle Variations in Roadbed Weight 2255 kg 3183 kg 4183 kg 3183 kg Deformable Roof

22. U-C – Roll Rate Vs Roll Angle Filtered Curves (SAE 060) Variations in Roadbed Weight 2255 kg 3183 kg 4183 kg 3183 kg Deformable Roof

23. U-C – Passenger & Driver Intrusion Characteristics Variations in Roadbed Weight 2255 kg 3183 kg 4183 kg 3183 kg Passenger Driver Passenger Driver Deformable Roof

24. U-C – Roadbed Speed (Deformable Roof) at 350 ms Deformable Roof

25. Roadbed Force, Roll Angle & Intrusion Characteristics ComparisonsElastic Roof

26. Strong Roof Assumption - Elastic Model • Representative of future vehicles that are going to meet the new FMVSS 216 requirements • All roof components were switched to linear elastic • The Strength to Weight Ratio (SWR) is measured to be 3.9 E= 200GPa With No Yielding Elastic Roof

27. U-C – Roadbed Normal Force Vs Roll Angle Variations in Roadbed Weight 2255 kg 3183 kg 4183 kg 3183 kg Elastic Roof

28. U-C – Roll Rate Vs Roll Angle Filtered Curves (SAE 060) Variations in Roadbed Weight 2255 kg 3183 kg 4183 kg 3183 kg Elastic Roof

29. U-C – Passenger & Driver Intrusion Characteristics Variations in Roadbed Weight 2255 kg 3183 kg 4183 kg 3183 kg Passenger Driver Passenger Driver Elastic Roof

30. U-C – Roadbed Speed (Elastic Roof) at 350 ms Elastic Roof

31. Conclusion For Different Roadbed Weights • The normal roadbed force, the roll rate and the intrusion characteristics were similar for both the Deformable and Elastic roof models. • When the roadbed weight increased, the difference between the initial and final roadbed speeds decreased. The percentage decrease for the Deformable model was greater than for the Elastic model. • * The heavy roadbed weight is assumed by applying a constant speed Elastic Roof

32. Conclusions Roadbed Weight What difference does it make on the test? What weight to I need?

33. Roadbed Speed Effect On Un-Constrained Model (6 Different Speeds)

34. Strong Roof Assumption - Elastic Model • Representative of future vehicles that are going to meet the new FMVSS 216 requirements • All roof components were switched to linear elastic • The Strength to Weight Ratio (SWR) is measured to be 3.9 E= 200GPa With No Yielding Elastic Roof

35. Baseline Model – Setup ISO View Front View Side View

36. Different Roadbed SpeedsRoadbed Force, Roll Angle & Intrusion Characteristics

37. Baseline Simulation – Elastic Model Simulation tracked at the C.G.

38. Roadbed Normal Force Vs Roll Angle Variations in Roadbed Speed 0 kph 09 kph 18 kph 24 kph 30 kph 36 kph

39. Roll Rate Vs Roll Angle Filtered Curves (SAE 060) Variations in Roadbed Speed 0 kph 09 kph 18 kph 24 kph 30 kph 36 kph

40. Passenger & Driver Intrusion Characteristics Passenger (near) Side Driver (far) Side

41. Different Roadbed SpeedsRoadbed Force, Roll Angle & Intrusion Characteristics

42. Model Setup & Initial Conditions Roadbed Side View Front View Same set up as previous model with initial roll angle of 180°

43. Baseline Simulation – Elastic Model Simulation tracked at the C.G.

44. Roadbed Normal Force Vs Roll Angle Variations in Roadbed Speed 180o Roll Angle 09 kph 18 kph 24 kph 30 kph 36 kph

45. Roll Rate Vs Roll Angle Variations in Roadbed Speed 180o Roll Angle 09 kph 18 kph 24 kph 30 kph 36 kph Filtered Curves (SAE 060)

46. Driver Intrusion Characteristics

47. Intrusion Characteristics Comparison (180° & 145°) Driver (far) Side Dynamic Intrusion Intrusion Rate

48. Conclusion For Different Roadbed Speeds The minimum roadbed speeds necessary to obtain 3 quarter turns rollover is of 24 km/h (14.9 mph) (Have you tried 20 and 22?) The roadbed normal forces follow the same pattern for roadbed speeds between 24 and 36 km/h (14.9 - 22.4 mph) for initial roll angle of 145° When the roadbed speed increases, the roll rate after initial contact increases for speeds above 18 km/h (11.2 mph) For different roadbed speeds and the baseline initial conditions, the dynamic intrusion and the intrusion rate for initial roll angle of 145° are higher than for 180° initial roll angle

49. Questions?