DESIGN AND ANALYSIS OF THE AUTO BODY DOORS OF THE

GENERAL MOTORS CHEVROLET .RU

General Motors Tutor Presentation : Peter Foss

Project Supervisor : Professor Ahmad Barari

Faculty of Engineering & Applied ScienceUniversity of Ontario Institute of

Technology

Ahmad.barari@uoit.ca

Team members:

Gregory Eberle, B.Eng (Team Leader)

Gregorye1@msn.com

Stephan Cregg, B.Eng

Guarav Sharma, B.Eng

Material choice – Composites Fibre Characteristics

Fibre Selection: E-glassFibre Orientation : RandomFibre volume ratio:

25% outer door panel (Grade A SMC) 40% inner door panel (Structural SMC)

Critical fibre length: 0.8625 mmChosen fibre length: 25 mm (over 30 times lc)Fibre diameter = 15 microns (between 20-150 times

smaller than lc)

Sheet Moulding Compounds

Composition Grade A SMC formulation

ResinFiller Additives – Initiators,

Inhibitors, ThickenersFiber

Processes• Compounding• Moulding

Door Auto Body CAD Design

Front Door

Butterfly Hinges

Original Equipment Manufacturers (OEM) Hinges

Impact Beam15° from the horizontal

Finite Element Models

Frame Rigidity Test

Vertical Displacement Test

Geometry #1

Geometry #2

CAD model use for FEAUsed portion of door to eliminate computational shortfalls

2 ribbing geometriestest based on various

quantities

Finite Element Analysis Results

Steel = 3.26 kgOptimized SMC Geometry = 1.34 kg40% reduction in weight!

Steel = 7.31 mmOptimized SMC Geometry = 19.19 mm

Steel = 35.29 mmOptimized SMC Geometry = 21.17 mm

Conclusion: SMC is extremely competitive with steel.

The # of ribs chosen, 35 ensures a FoS of > 2.5

Cost to Manufacture 38 ribs = $1235 CDN

Vertical displacement test

Frame Rigidity Test

Rigid Body Transformation

Determine overall door movement based on Hinge deformation

Euler Parameters including Alpha, Beta and Gamma angles

FEA AnalysisRight Angle TrianglePoints of Pressure

Rigid Body Transformation

Co-ordinates from CAD file

Matrix Manipulation Portion of Matlab Code

Results

n= 3 %^number of Original pointsOP(:,1)=[-Portion of MatLAB CodeOP(:,2)=[-3 15.5 32.5];OP(:,3)=[-3 23 32.5];

DV(:,1)=[0.022071 -0.026075 0.006052];DV(:,2)=[0.017249 -0.025916 0.005559];DV(:,3)=[0.012483 -0.025689 0.005207];

Rigid Body Transformation (Results)

A = -0.0478 0.3218 -0.0150 0 0.8277 0.5306 0.0225 0 0.8277 -0.6161 0.0320 0 -0.0479 -0.4429 0.0288 0 0 0 0 1.0000

B = -0.0478 0.3218 -0.0151 -0.0092 0.8278 0.5305 0.0216 0.0006 0.8276 -0.6163 0.0319 0.0304 -0.0480 -0.4429 0.0291 0.0108 0 0 0 1.0000

Impact Beam Design

Designs Analyzed:

Impact Beam Testing

FEA Testing Procedures: Optimization of wall thickness (≈3.175mm) (σy x FoS) vs. Mass (@ 1.3kg; 1.6kg; 1.9kg; 2.2kg;

2.5kg) MOI vs. Mass (@ 1.3kg; 1.6kg; 1.9kg; 2.2kg; 2.5kg)

Constraints and Assumptions:• FoS ≥ 3.0 (Reported Industry Standard)

σy/ FoS >σvon

• Maximum allowable displacement: Based upon 95th percentile of adult population’s sitting hip breadth δmax=14.35 cm

• Impact beam length = 600 mm

Testing Results

Optimization of wall thickness:

(σy x FoS) vs. Mass:

Impact Beam Design Displacement (Magnitude; mm)

Stress (Von Mises; kPa)

Factor of Safety(FoS)

Square 1.823e+000 3.819e+005 3.1Square with Rounded Edge 2.214e+000 4.702e+005 2.5Square with Angled Edge 2.208e+000 4.655e+005 2.5I-Beam 1.685e+000 3.629e+005 3.2Tubular 2.332e+000 4.564e+005 2.6

Statistical Error [(1.0 – R2)/R2]*100%Square 0.79%

Square Round 11.2%I-Beam 2.0%Tubular 0.64%

Testing Results (cont.)

MOI vs. Mass:

Impact Beam Selection: Square and I-Beam (extremely close) Final selection criteria is to be based upon

manufacturability and associated costs

Statistical Error [(1.0 – R2)/R2]*100%Square 1.4%

Square Round 0.21%I-Beam 1.8%Tubular 24.1%

Test & Prototyping

Ideas for test plan i.e. Prove viability of ribs

Load

String

structure with ribs

Ends are fixed

Load

String

structure with ribs

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