Plastic versus Steel: An Automotive Fuel Tank Case Study Using the 2013 GM Cadillac ATS Platform

Transcription

1 Plastic versus Steel: An Automotive Fuel Tank Case Study Using the 2013 GM Cadillac ATS Platform Eric Neuwirth Spectra Premium Industries

2 Case Study Review Design Requirements Design Overview Forming Analysis Manufacturability Fuel Capacity / Grade Venting Studies Mass Pressure / Vacuum Cyclic Fatigue Summary Conclusions Additional Opportunities Outline

3 Design Requirements Atmospheric (non-pressurized) system Steel fuel tank requirements must fit existing 2013 Cadillac ATS package space, while maintaining appropriate clearances must be formable using commercially available steel grades must be manufacturable using standard equipment must meet or exceed fuel volume of existing plastic fuel tank must have a mass that is equivalent to or less than the mass of existing plastic fuel tank must meet applicable fuel tank pressure/vacuum cycling durability requirements for an atmospheric system: 12,000 PV cycles + 50% safety factor o Pressure: 14.9 kpa o Vacuum: 7.0 kpa

4 Design Requirements Based on the design assumptions listed on the previous slide, two different steel tanks have been designed: Volume-Maximizing Steel Tank o Seeks to maximize usable fuel volume to a level greater than that of the plastic fuel tank while still maintaining a mass less than that of the plastic fuel tank Volume-Equivalent Steel Tank o Seeks to achieve a usable fuel volume equal to that of the plastic fuel tank while achieving a mass significantly less than that of the plastic fuel tank

5 Design Requirements Steel fuel tank must fit existing 2013 Cadillac ATS package space, while maintaining appropriate clearances.

6 Design Overview: Volume-Maximizing Steel Tank

7 Design Overview: Volume-Maximizing Steel Tank

8 Design Overview: Volume-Maximizing Steel Tank

9 Design Overview: Volume-Maximizing Steel Tank SECTION at Y=zero

10 Design Overview: Volume-Maximizing Steel Tank

11 Design Overview: Volume-Maximizing Steel Tank

12 Design Overview: Volume-Maximizing Steel Tank

13 Design Overview: Volume-Equivalent Steel Tank

14 Design Overview: Volume-Equivalent Steel Tank

15 Design Overview: Volume-Equivalent Steel Tank

16 Design Overview: Volume-Equivalent Steel Tank INTERNAL VAPOR MANAGEMENT STEEL : GREEN PLASTIC : PURPLE

17 Forming Analysis Steel fuel tank must be formable using commercially available steel grades.

18 Forming Analysis Volume-Maximizing Steel Tank

19 Forming Analysis: Volume-Maximizing Steel Tank Top Shell Thinning at 0.7 mm nominal

20 Forming Analysis: Volume-Maximizing Steel Tank Top Shell Forming Limit Diagram

21 Forming Analysis: Volume-Maximizing Steel Tank Bottom Shell Thinning at 0.65 mm nominal

22 Forming Analysis: Volume-Maximizing Steel Tank Bottom Shell Forming Limit Diagram

23 Forming Analysis Volume-Equivalent Steel Tank

24 Forming Analysis: Volume-Equivalent Steel Tank Top Shell Thinning at 0.67 mm nominal

25 Forming Analysis: Volume-Equivalent Steel Tank Top Shell Forming Limit Diagram

26 Forming Analysis: Volume-Equivalent Steel Tank Bottom Shell Thinning at 0.65 mm nominal

27 Forming Analysis: Volume-Equivalent Steel Tank Bottom Shell Forming Limit Diagram

28 Manufacturability Steel fuel tank must be manufacturable using standard equipment.

29 Manufacturability The following slide shows the relevant Contour II design guidelines, as published by welding equipment manufacturer Soutec. Both the Volume-Maximizing tank and the Volume-Equivalent tank adhere to these guidelines.

30 Manufacturability

31 Manufacturability Andritz Soutec AG Contour II Fuel Tank Welding Machine

32 Fuel Capacity / Grade Venting Studies Steel fuel tank must meet or exceed fuel volume of existing plastic fuel tank.

33 Grade Venting Requirements Fuel Capacity / Grade Venting Studies When filled to capacity, the fuel tank assembly must be capable of venting when the vehicle is inclined up to 30% in the four primary orientations, and up to 27% in the four secondary orientations, accounting for thermal expansion of the fuel. The fuel tank capacity used shall be the Customer Fill Fuel Capacity plus an additional 4% for fuel expansion for grades less than or equal to 6%, and 2.2% for fuel expansion for grades greater than 6% up to 30%. The fuel tank assembly shall be designed to address either a failed FLVV or GVV with the vehicle on these grades.

34 Fuel Capacity / Grade Venting Studies Volume-Maximizing Steel Tank

35 Fuel Capacity / Grade Venting Studies: Volume-Maximizing Steel Tank FRONT UP 30% STANDARD GRADES REAR UP LEFT SIDE UP RIGHT SIDE UP

36 Fuel Capacity / Grade Venting Studies: Volume-Maximizing Steel Tank 27% COMPOUND GRADES

37 Fuel Capacity / Grade Venting Studies: Volume-Maximizing Steel Tank LEVEL

38 GRADE VENTING Fuel Capacity / Grade Venting Studies: Volume-Maximizing Steel Tank Orientation Grade Usable Volume* Vapor Space Limiting (%) (degrees) (gallons) (%) Factor 0 Front Up GVV 45 Right Front Up X-connector 90 Right Up X-connector 135 Right Rear Up X-connector & GVV 180 Rear Up GVV 225 Left Rear Up X-connector 270 Left Up X-connector 315 Left Front Up X-connector n/a Level GVV FLVV Shutoff Height (maximum) 19.1 * Usable volume shown is net of a 0.5-gallon contingency (design safety factor) to account for the effect of unusable fuel. Usable volume shown accounts for 2.2% thermal expansion of fuel on non-zero grades. Usable volume shown accounts for 4.0% thermal expansion of fuel at level (zero grade).

39 Fuel Capacity / Grade Venting Studies: Volume-Maximizing Steel Tank Usable Fuel Volume (gallons) (liters) Volume-Maximizing Steel Tank Production Plastic Tank* Steel Tank Advantage * Production plastic tank volume provided by General Motors Product Engineering. Advertised volume is 16.0 gallons (60.6 liters).

40 Fuel Capacity / Grade Venting Studies: Volume-Maximizing Steel Tank But what if the sub-side module were serviceable? If the steel tank sub-side module were serviceable, the steel tank usable volume would be reduced by only 0.87 gallons (3.3 L), resulting in a steel tank usable volume of 17.9 gallons (67.8 L), which is still 1.4 gallons (5.3 L) more useable fuel than the plastic tank capacity. Cut-out for serviceable sub-side module

41 Fuel Capacity / Grade Venting Studies Volume-Equivalent Steel Tank

42 Fuel Capacity / Grade Venting Studies: Volume-Equivalent Steel Tank FRONT UP 30% STANDARD GRADES REAR UP LEFT SIDE UP RIGHT SIDE UP

43 Fuel Capacity / Grade Venting Studies: Volume-Equivalent Steel Tank 27% COMPOUND GRADES

44 Fuel Capacity / Grade Venting Studies: Volume-Equivalent Steel Tank LEVEL

45 GRADE VENTING Fuel Capacity / Grade Venting Studies: Volume-Equivalent Steel Tank Orientation Grade Usable Volume* Vapor Space Limiting (%) (degrees) (gallons) (%) Factor 0 Front Up GVV 45 Right Front Up X-connector 90 Right Up X-connector 135 Right Rear Up X-connector & GVV 180 Rear Up GVV 225 Left Rear Up X-connector 270 Left Up X-connector 315 Left Front Up X-connector n/a Level GVV FLVV Shutoff Height (maximum) 16.5 * Usable volume shown is net of a 0.5-gallon contingency (design safety factor) to account for the effect of unusable fuel. Usable volume shown accounts for 2.2% thermal expansion of fuel on non-zero grades. Usable volume shown accounts for 4.0% thermal expansion of fuel at level (zero grade).

46 Mass Steel fuel tank must have a mass that is equivalent to or less than the mass of existing plastic fuel tank.

47 Mass: Volume-Maximizing Steel Tank Mass (pounds) (kg) Plastic Fuel Tank Heat Shield Total Assembly, Plastic Fuel Tank Mass (pounds) (kg) Steel Fuel Tank Heat Shield Total Assembly, Volume-Maximizing Steel Fuel Tank Mass Savings with Steel Mass (pounds) (kg) Despite the 2.3-gallon (8.7-liter) usable fuel advantage of the Volume-Maximizing steel tank, the mass of the steel tank is still 1.7 pounds (0.76 kg) less than the mass of the production plastic tank.

48 Mass: Volume-Maximizing Steel Tank Flangeless Alternative If a less conventional welding method were used which would eliminate the need for a weld flange, the mass impact of removing weld flange would be a further reduction of 1.1 lbs (0.5 kg), resulting in a total mass improvement of 2.8 lbs (1.26 kg) compared to the production plastic fuel tank: Top Shell = 3.64 kg (Δ = kg) Bottom Shell = 3.52 kg (Δ = kg) Total = 7.16 kg (Δ = kg)

49 Mass: Volume-Equivalent Steel Tank Mass (pounds) (kg) Plastic Fuel Tank Heat Shield Total Assembly, Plastic Fuel Tank Mass (pounds) (kg) Steel Fuel Tank Heat Shield Total Assembly, Volume-Maximizing Steel Fuel Tank Mass Savings with Steel Mass (pounds) (kg) In the case of the Volume-Equivalent steel tank, the mass benefit is even greater. This fully functional design saves 3.1 pounds (1.39 kg) compared to the production plastic tank.

50 Pressure / Vacuum Cyclic Fatigue Steel fuel tank must meet pressure / vacuum cycling durability requirements for an atmospheric system: 12,000 PV cycles + 50% safety factor Pressure: 14.9 kpa Vacuum: 7.0 kpa

51 Pressure / Vacuum Cyclic Fatigue Volume-Maximizing Steel Tank

52 Pressure / Vacuum Cyclic Fatigue: Volume-Maximizing Steel Tank

53 Pressure / Vacuum Cyclic Fatigue: Volume-Maximizing Steel Tank Loading Details Load Optistruct Equation Location Hydro e-6*(898-z) All elements below Z height of 898 mm Positive Pressure 14.9 kpa All internal elements Negative Pressure 7 kpa All internal elements Pre-load Z=3 mm Strap ends

54 Pressure / Vacuum Cyclic Fatigue: Volume-Maximizing Steel Tank Material Properties Shell Top Bottom Name EDDS EDDS Young s Modulus 210,000 MPa 210,000 MPa Yield 152 MPa 152 MPa UTS 306 MPa 306 MPa Optistruct Fatigue Parameters Sf' b c Ef' n' K' Nc 2.0E E+08

55 Pressure / Vacuum Cyclic Fatigue: Volume-Maximizing Steel Tank Shell Fatigue Life (cycles) Top 17,975 Bottom 19,382

56 Pressure / Vacuum Cyclic Fatigue: Volume-Maximizing Steel Tank Fatigue - Top

57 Pressure / Vacuum Cyclic Fatigue: Volume-Maximizing Steel Tank Fatigue - Top

58 Pressure / Vacuum Cyclic Fatigue: Volume-Maximizing Steel Tank Fatigue - Bottom

59 Pressure / Vacuum Cyclic Fatigue: Volume-Maximizing Steel Tank Fatigue - Bottom

60 Pressure / Vacuum Cyclic Fatigue: Volume-Maximizing Steel Tank Displacement (+14.9 kpa)

61 Pressure / Vacuum Cyclic Fatigue: Volume-Maximizing Steel Tank Displacement (-7 kpa)

62 Pressure / Vacuum Cyclic Fatigue: Volume-Maximizing Steel Tank Stress - Top Shell (+14.9 kpa)

63 Pressure / Vacuum Cyclic Fatigue: Volume-Maximizing Steel Tank Stress - Bottom Shell (+14.9 kpa)

64 Pressure / Vacuum Cyclic Fatigue: Volume-Maximizing Steel Tank Stress - Top Shell (-7 kpa)

65 Pressure / Vacuum Cyclic Fatigue: Volume-Maximizing Steel Tank Stress - Bottom Shell (-7 kpa)

66 Pressure / Vacuum Cyclic Fatigue Volume-Equivalent Steel Tank

67 Pressure / Vacuum Cyclic Fatigue: Volume-Equivalent Steel Tank PRT /AA.036

68 Pressure / Vacuum Cyclic Fatigue: Volume-Equivalent Steel Tank Loading Details Load Optistruct Equation Location Hydro e-6*(898-z) All elements below Z height of 898 mm Positive Pressure 14.9 kpa All internal elements Negative Pressure 7 kpa All internal elements Pre-load Z=3 mm Strap ends

69 Pressure / Vacuum Cyclic Fatigue: Volume-Equivalent Steel Tank Material Properties Shell Top Bottom Name EDDS EDDS Young s Modulus MPa MPa Yield 150 MPa 150 MPa UTS 270 MPa 270 MPa Optistruct Fatigue Parameters Sf' b c Ef' n' K' Nc 2.0E E+08

70 Pressure / Vacuum Cyclic Fatigue: Volume-Equivalent Steel Tank Shell Fatigue Life (cycles) Top 36,285 Bottom 20,453

71 Pressure / Vacuum Cyclic Fatigue: Volume-Equivalent Steel Tank Fatigue - Top

72 Pressure / Vacuum Cyclic Fatigue: Volume-Equivalent Steel Tank Fatigue - Top

73 Pressure / Vacuum Cyclic Fatigue: Volume-Equivalent Steel Tank Fatigue - Bottom

74 Pressure / Vacuum Cyclic Fatigue: Volume-Equivalent Steel Tank Fatigue - Bottom

75 Pressure / Vacuum Cyclic Fatigue: Volume-Equivalent Steel Tank Displacement (+14.9 kpa)

76 Pressure / Vacuum Cyclic Fatigue: Volume-Equivalent Steel Tank Displacement (-7 kpa)

77 Pressure / Vacuum Cyclic Fatigue: Volume-Equivalent Steel Tank Stress - Top Shell (+14.9 kpa)

78 Pressure / Vacuum Cyclic Fatigue: Volume-Equivalent Steel Tank Stress - Bottom Shell (+14.9 kpa)

79 Pressure / Vacuum Cyclic Fatigue: Volume-Equivalent Steel Tank Stress - Top Shell (-7 kpa)

80 Pressure / Vacuum Cyclic Fatigue: Volume-Equivalent Steel Tank Stress - Bottom Shell (-7 kpa)

81 Summary: Conclusions Two different steel fuel tanks a volume-maximizing tank and a volumeequivalent tank have been designed to fit the existing 2013 Cadillac ATS package space, while maintaining appropriate clearances. These steel fuel tanks are both formable using commercially available steel grades. are both manufacturable using standard equipment. have a usable fuel volume that exceeds the usable fuel volume of the existing plastic fuel tank by up to 8.7 L (2.3 gallons). are as much as 1.39 kg (3.06 lbs) lighter than the existing plastic fuel tank, not including the additional mass avoidance with the flangeless alternative. both meet the fuel tank pressure / vacuum cycling durability requirements specified for an atmospheric system, including a 50% safety factor.

82 Summary: Additional Opportunities The results presented here are a work-in-progress. It is possible to continue to improve the 2013 Cadillac ATS steel fuel tank designs with the following goals: Achieve nominal gauge of 0.6 mm through further topography optimization. Design slosh baffles that are also structural, thereby allowing a further reduction in shell gauge. Further reduce mass through the use of alternative steels such as advanced high strength steels or stainless steels.

83 For More Information Visit: Rich Cover Program Manager, SASFT +1 (248) Eric Neuwirth Spectra Premium Industries +1 (248)

84 PRESENTATIONS WILL BE AVAILABLE MAY 3 Use your web-enabled device to download the presentations from today s event Great Designs in Steel is Sponsored by: