ME 501 Final Project:ME 501 Final Project:Analysis of Ford Analysis of Ford

Expedition Expedition Frame CrossmemberFrame Crossmember

June 20, 2001June 20, 2001

John SmartJohn Smart

Andy StanselAndy Stansel Courtesy Ford Motor CompanyUsed without permission

Presentation Outline

• Project Background and Objective

• Modeling—meshing, boundary conditions.

• 3 loading conditions

• Results

• Conclusions

Project Objective

Modeling—ProE Model

• Both crossmembers were created in Pro/E

Frame rails

OEM Crossmember

New crossmember

New crossmenber dimensions

Modeling—Ansys Model

• Export Pro/E model as an IGES file

• Import the IGES file into ANSYS

• Set element type as “Shell 63” (3D, 4 node element, 6 DOF per node)

• Set shell thickness to .125”• Material properties of steel (E=30 Mpsi, =.27)

1040 Steel, Sy = 86 kpsi

Modeling—Meshing

• Several different meshes were tested

Coarse & fine free meshing

4 elements thick

Fine mapped meshing

2,544 elements2,546 nodes15,276 DOF (unconstrained)

#1 Fixed

#2 Chase boundary

Modeling—Boundary Conditions

• Two separate boundary conditions were tested

OEM crossmember

symmetry

Difference of 8 kpsi

Difference of 2 psi! Therefore, we used fixed-fixed conditions

Modeling—Boundary Conditions

• Two separate boundary conditions were testedNew crossmember

#1. Fixed, fixed

#2. Quasi-simply supported

Loading Condition #1

• Vehicle at rest, or driving straight, or landing from jump.

Fixed

Fixed

1,000 lbs.

1,000 lbs.

New crossmemberOEM crossmember

Fixed

Rollers

1,000 lbs

Loading #1— Results

OEM crossmember

Maximum deflection=.022”

New crossmember

Maximum deflection=.0335”

Y-displacement

Bulges out here

Loading #1— Results

New crossmember

Max eq. stress: 34 kpsi

Factor of safety: 2.5

Max eq. stress: 47 kpsi

Factor of safety: 1.8

OEM crossmember

Loading Condition #2

• Frame rails twist due to terrain. This induces torsion in the crossmember.

fixed

500 ft-lbs

OEM crossmember

fixed

500 ft-lbs

New crossmember

Loading #2—Results

OEM crossmember New crossmember

Max deflection: 0.0325”

Max deflection: 0.0308”

Loading #2—Results

New crossmember

Max eq. stress: 8.8 kpsi

Factor of Safety: 9.7

OEM crossmember

Max eq. stress: 7.6 kpsi

Factor of Safety: 11.3

Loading Condition #3

• Pure bending in crossmember

fixed

1,000 lbs

fixed

1,000 lbs

OEM crossmember New crossmember

Loading #3—Results

OEM crossmember New crossmember

Max deflection: 0.972”Max deflection: 0.897”

Loading #3—Results

Max eq. stress: 59.1 kpsiFactor of safety: 1.4

OEM crossmember New crossmember

Max eq. stress: 92.8 kpsiFactor of safety: 0.92

Mad stress concentration

Loading #3—Results

OEM crossmember New crossmember

Z (normal)

Neutral axis

Summary of Results

Safety factors

Load case OEM New

1 (shear) 1.8 2.5

2 (torsion) 11.3 9.7

3 (bending) 1.4 0.9

Model Limitations

• Difficult to model frame rail interaction—boundary conditions

• Difficult to know magnitude of loading conditions

• No detailed models of weld joints, body mounts, gussets, or rounds

Conclusion

Our simple analysis shows:

• The new crossmember is less stressed than the OEM version for typical “around town” loading conditions (load case 1)

• However, for extreme off-road type load conditions, the new crossmember is inferior to the OEM (load cases 2,3)

• Further analysis and prototype testing should be done before going into production.

What we learned

• 3D importing

• 3D meshing

• Effects of different boundary conditions

• FEA is not a “black box”