Optimized Steel Solutions for Roof Strength Using AHSS/media/Files/Autosteel/Great Designs in... ·...
Transcript of Optimized Steel Solutions for Roof Strength Using AHSS/media/Files/Autosteel/Great Designs in... ·...
Optimized Steel Solutions for
Roof Strength Using AHSS
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Guofei ChenAutomotive Center
United States Steel Corporation
Outline
• Introduction
• Baseline Model
• Optimization Without Design Change
• Design Change with Steel Inserts
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• Design Change with Steel Inserts
• Optimization With Design Changes
• Design Comparisons
• Summary
Introduction
• In August 2005, NHTSA proposed to increase the roof strength requirement
under FMVSS216 from 1.5 to 2.5 times unloaded vehicle weight (UVW).
• The combination of occupant safety and the new fuel economy standard presents
a challenge to automakers to meet the increased roof load requirements with the
least weight and cost penalties.
• Advanced High Strength Steels are being effectively utilized for vehicle weight
reduction while maintaining or improving safety, durability and NVH
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reduction while maintaining or improving safety, durability and NVH
performance.
• This study focuses on steel only design solutions with the use of AHSS and CAE
optimization technology.
• The target is to achieve a roof strength of 3 times UVW within 4.5 inch (114mm)
load platen travel, 20% safety margin over the new FMVSS 216 requirements.
A/SP MEARS Phase I – With Nylon Inserts
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THK: 1.3mm
MAT: DP590
THK: 0.8mm
MAT: DR210
THK: 0.8mm
MAT: DP980THK: 1.2mm
MAT: DP980
Cab Mass: 500.1kg
Load Factor: 3.05
(Nylon Inserts are located in the A-Pillar and C-Pillar)
A/SP MEARS Phase I – With Nylon Inserts
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THK: 0.9mm
MAT: DQSK
THK: 0.9mm
MAT: DQSK
THK: 1.2mm
MAT: Boron1550
THK: 1.1mm
MAT: DP590
THK: 1.8mm
MAT: DP590THK: 0.8mm
MAT: Boron1550
THK: 0.7mm
MAT: DP780
THK: 0.8mm
MAT: HSLA350
THK: 1.2mm
MAT: HSLA350
MAT: DR210
Baseline Model
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• Built a baseline model from the A/SP MEARS phase 1 model with nylon inserts
• Removed nylon inserts and unnecessary contact definitions
• Increased time step (1.0 1.3 µs) and moving speed (1 3 m/s) of the rigid plate
• Decreased the CPU time from 15 hours to 3 hours with 4 CPUs for each run
Create a Reduced Model for Optimization
A/SP MEARS Phase I Model
Gauge and Material (AHSS) Optimization
w/o Design Change
Methodology Schematic
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Concept Designs
Add Steel Inserts to Improve Crush Load
Update the Model with Optimal Steel Inserts
Gauge and Material (AHSS) Optimization
With Optimal Steel Inserts
AHSS Grades
800
1200
1600
2000
Str
ess (
MP
a)
HSLA350
DP590
DP780
DP980
Boron1550
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0
400
800
0 0.05 0.1 0.15 0.2 0.25
Plastic strain
Str
ess (
MP
a)
Parts for Optimization
Part Name MaterialGauge Range
(mm)
A_Pillar_Inner HSLA350 - Boron1550 0.6 - 2.2
A_Pillar_Rnf HSLA350 - Boron1550 0.6 - 2.2
BSO_Apillar HSLA350 - Boron1550 0.6 - 2.2
BSO_Cpillar HSLA350 - Boron1550 0.6 - 2.2
C_Pillar_Up HSLA350 - Boron1550 0.6 - 2.2
C_Pillar_Low HSLA350 - Boron1550 0.6 - 2.2
Header_Fr_Up HSLA350 - Boron1550 0.6 - 2.2
Header_Fr_Low HSLA350 - Boron1550 0.6 - 2.2
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Header_Fr_Low HSLA350 - Boron1550 0.6 - 2.2
Header_Rr_Up/C_Jt_Rnf HSLA350 - Boron1550 0.6 - 2.2
Header_Rr_Low HSLA350 - Boron1550 0.6 - 2.2
Roof_Bow HSLA350 - Boron1550 0.6 - 2.2
Roof_Rail_Inner HSLA350 - Boron1550 0.6 - 2.2
Roof_Rail_Outer HSLA350 - Boron1550 0.6 - 2.2
• 13 parts for material and gauge optimization w/o design changes
• Optimization software: HyperStudy and LS-Dyna
• Optimization objective: minimum mass
Constraints: roof crush load factor > 3.0
495
500
505
510
Ma
ss
(k
g)
1.5
2
2.5
3
3.5
Cru
sh
Lo
ad
Fa
cto
r
Cab Mass
Crush Load Factor
Optimization Results – With Boron1550
Best
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490
0 5 10 15 20 25 30 35 40
Iteration Number
1
Optimization Results – With Boron1550
THK: 1.54mm
MAT: Boron1550
THK: 1.0mm
MAT: DP590
THK: 0.7mm
MAT: DP980THK: 0.8mm
MAT: DP980
Cab Mass: 501.6kg
Load Factor: 3.00
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THK: 0.69mm
MAT: TRIP780
THK: 1.61mm
MAT: TRIP780THK: 1.24mm
MAT: Boron1550
THK: 1.32mm
MAT: Boron1550
THK: 0.97mm
MAT: Boron1550THK: 1.29mm
MAT: Boron1550
THK: 0.79mm
MAT: DP780
THK: 1.0mm
MAT: DP590
THK: 0.9mm
MAT: DP590
Optimization Results – No Boron1550
THK: 2.2mm
MAT: DP590
THK: 1.02mm
MAT: DP590
THK: 0.71mm
MAT: DP980THK: 0.82mm
MAT: DP980
Cab Mass: 505.6kg
Load Factor: 2.98
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THK: 0.74mm
MAT: TRIP780
THK: 1.78mm
MAT: TRIP780THK: 1.49mm
MAT: DP980
THK: 1.45mm
MAT: DP780
THK: 1.08mm
MAT: DP780THK: 1.36mm
MAT: DP980
THK: 0.8mm
MAT: DP780
THK: 0.96mm
MAT: DP590
THK: 1.02mm
MAT: DP590
Plastic Strains on Roof Structures
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Steel Inserts In Roof Rails
Insert Case #1 Insert Case #2
Section Cut Section Cut
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Roof Bow Location
Original Location 90mm Forward
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Reinforcement at C-Pillar
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Reinforcement
DP980 or Boron1550
Tube at C-Pillar
Tube
1.5mm DP590
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1.5mm DP590
Reinforcement Tube at A-Pillar
Reinforcement - Tube
DP780
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A-Pillar Extended
ExtendedExtended
Extended
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Flange Added
Extended
Flange Added
A-Pillar Extended
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After Extension
Roof Crush Performance With Steel Inserts
�Add C-Pillar Reinforcement
� Remove Rear Header Upper
�Add A-Pillar Reinforcement Tube
� Extend A-Pillar
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Optimization Results –
With Boron1550 & Steel Inserts
495
500
505
Ca
b M
as
s (
kg
)
1.5
2
2.5
3
3.5
Cru
sh
Lo
ad
Fa
tco
r
Cab Mass (kg)
Crush Load Factor
Best
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490
0 5 10 15 20 25 30 35
Iteration Number
1
Crush Load Factor
THK: 1.31mm
MAT: Boron1550
THK: 0.61mm
MAT: DP590
THK: 1.09mm
MAT: Boron1550THK: 0.99mm
MAT: Boron1550
Cab Mass: 496.6kg
Load Factor: 3.00
Optimization Results –
With Boron1550 & Steel Inserts
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THK: 0.63mm
MAT: TRIP780
THK: 1.34mm
MAT: TRIP780
THK: 1.53mm
MAT: Boron1550
THK: 0.96mm
MAT: Boron1550
THK: 0.80mm
MAT: Boron1550
THK: 0.60mm
MAT: Boron1550
THK: 0.60mm
MAT: DP780
THK: 0.62mm
MAT: DP590
THK: 0.64mm
MAT: DP590
Optimization Results –
With Steel Inserts, No Boron1550
THK: 1.41mm
MAT: DP590
THK: 0.86mm
MAT: DP590
THK: 1.23mm
MAT: DP980THK: 1.22mm
MAT: DP980
Cab Mass: 501.3kg
Load Factor: 3.00
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THK: 0.76mm
MAT: TRIP780
THK: 1.65mm
MAT: TRIP780
THK: 1.60mm
MAT: DP980
THK: 1.26mm
MAT: DP780
THK: 0.90mm
MAT: DP780
THK: 0.71mm
MAT: DP980
THK: 0.60mm
MAT: DP780
THK: 0.60mm
MAT: DP590
THK: 0.60mm
MAT: DP590
Design Comparisons
Components
A/SP Phase I Nylon Inserts
Optimized
Optimized To DP980
Optimized To Boron1550
Steel Inserts and Optimized To
DP980
Steel Inserts and
Optimized To Boron1550
Mass: 500.1kg Mass: 505.6kg Mass: 501.6kg Mass: 501.3kg Mass: 496.6kg
Load: 3.0 Load: 3.0 Load: 3.0 Load: 3.0 Load: 3.0
MAT THK(mm) MAT THK(mm) MAT THK(mm) MAT THK(mm) MAT THK(mm)
A_Pillar_Inner DP590 1.1 DP780 1.45 Boron1550 1.32 DP780 1.26 Boron1550 0.96
A_Pillar_Rnf Boron1550 1.2 DP980 1.49 Boron1550 1.24 DP980 1.6 Boron1550 1.53
BSO_Apillar DQSK 0.9 TRIP780 0.74 TRIP780 0.69 TRIP780 0.76 TRIP780 0.63
BSO_Cpillar DQSK 0.9 TRIP780 1.78 TRIP780 1.61 TRIP780 1.65 TRIP780 1.34
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BSO_Cpillar DQSK 0.9 TRIP780 1.78 TRIP780 1.61 TRIP780 1.65 TRIP780 1.34
C_Pillar_Up DP590 1.3 DP590 2.2 Boron1550 1.54 DP590 1.41 Boron1550 1.31
C_Pillar_Low DP590 1.8/.8 DP780 1.08 Boron1550 0.97 DP780 0.9 Boron1550 0.8
Header_Fr_Up HSLA350 0.8 DP590 0.96 DP590 1 DP590 0.6 DP590 0.62
Header_Fr_Low HSLA350 1.2 DP590 1.02 DP590 0.9 DP780 0.6 DP590 0.64
Header_Rr_Up/C_Rnf DP980 1.2 DP980 0.82 DP980 0.8 DP980 1.22 Boron1550 0.99
Header_Rr_Low DP980 0.8 DP980 0.71 DP980 0.7 DP980 1.23 DP980 1.09
Roof_Bow DR210 0.8 DP590 1.02 DP590 1 DP590 0.86 DP590 0.61
Roof_Rail_Inner DP780 0.7 DP780 0.8 DP780 0.79 DP780 0.6 DP780 0.6
Roof_Rail_Outer Boron1550 0.8 DP980 1.36 Boron1550 1.29 DP980 0.71 Boron1550 0.6
Summary
• Steel inserts at A-pillar lower and C-pillar upper are effective to
improve roof crush performance for the B-pillarless pickup truck.
• The optimized steel only design meets the new roof strength
regulation with 3.5kg mass savings compared to the A/SP phase I
nylon insert design, and potential cost savings can also be achieved.
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• Using hot-stamped boron steel for A-pillar, C-pillar and roof rail for
roof crush offers about 4kg more mass savings than using DP steels.