1

Designing All-Terrain Vehicle Frames Using Topological Optimization

Automotive Mechatronics Research Center

Energy absorption

Lightness

Support and packaging

Problem description

2

Objectives

Design a frame topology that packages the components of a vehicle and protect the pilot integrity. This structural steel frame (~36 Kgs.) must compete against thin walled frames made of alloyed steel (~28 Kgs.)

Determine a topology that fulfills the operating conditions of the vehicle using topological optimization tools, satisfying Minibaja regulations.

Determine a frontal nose topology that reduces the impact effects over the pilot.

Methodology

ConceptConceptConceptConceptConceptConceptConceptConcept

Feasibility Feasibility Feasibility Feasibility Feasibility Feasibility Feasibility Feasibility

assessmentassessmentassessmentassessmentassessmentassessmentassessmentassessment

PreliminaryPreliminaryPreliminaryPreliminaryPreliminaryPreliminaryPreliminaryPreliminary

designdesigndesigndesigndesigndesigndesigndesign

Development Development Development Development Development Development Development Development

teststeststeststeststeststeststeststests

Detailed Detailed Detailed Detailed Detailed Detailed Detailed Detailed

designdesigndesigndesigndesigndesigndesigndesign

Recognition Recognition Recognition Recognition Recognition Recognition Recognition Recognition of Needsof Needsof Needsof Needsof Needsof Needsof Needsof Needs

3

Recognition of needs

Duties

Safety

Support

Main Characteristics

Stiffness

Energy absorption

Regulation fulfilling

Esthetics

Operating conditions

Loads

Suspension

Engine

Mass elements

Suspension Steering system

Damper

Wheel

4

Conceptualization

Objective

Removable material

Void spaces

Fixed points

Operating conditions

The optimization process took 25 hrs. to determine the optimum topology for the specified load case. More than a million tetrahedral elements were used.

Concept

5

Packaging

Ergonomic issues

Manufacturing

Competition regulations

Project feasibility and preliminary design

Preliminary design

Frontal impact test

AssumptionsHomogeneous material that includes Strain Rate effects

Perfect joints (no welding)

Simplified components

Undeformable tree.

Against a tree at 25 km/hr with LS DYNA

6

LS DYNA Model

Shell and beam elements

Suspension and steering system

Contact pairs

Termination time 0.12 s.

Influence and evaluation variables

Input variables for frontal impact

Nose width

Roll cage and nose angle

Output variables

Maximum acceleration

Mean acceleration

Closeness of frame to Pilot space (CPFS)

Width

Inner angle

CFPS

7

Design of Experiments Matrix

58658.62

48646.61

Width(mm)

Angle(deg)

Level / Factor

4

3

2

1

Exp

2

2

1

1

1

Factors

2

1

2

1

2

Acceleration plots

8

Energy

Energy

Results

124

123

115.6

119

DIST

(mm)

6.299.3158658.644

5.678.0148658.633

6.1310.2558646.6122

6.289.0148646.6111

MEAN ACCEL

(g´s)

MAX ACCEL

(g´s)

FACTOR B (Width,

mm)

FACTOR A (Angle, deg)

Exp

9

Maximum Acceleration (g’s)

An

gle

Wid

th

An

gle

Angle Width

70

60

50

40

30

20

10

0

-8.4

--8.6

-8.8

-9.0

-9.2

-9.4

-9.6

-9.8

-10

G’s%

Contribution Source Main effects

Mean Acceleration (g’s)

Wid

th

An

gle

Inte

ract

ion

40

35

30

25

20

15

10

0

5

-5.975

-6.025

-6.075

-6.125

-6.175

-6.225

G’s%

Contribution Source Main effects

Angle Width

10

Closeness of frame to Pilot space

Wid

thAn

gle

Inte

ract

ion

90

70

50

30

0

10

1.24

1.22

1.20

1.17

1.20

1.18

G’s

%

Contribution Source Main effects

Angle Width

1Width

2Angle

Distance

1Width

2AngleMean

Acceleration

1Width

2Angle

Max Acceleration

Optimum levelFactorsOutput

Optimum Levels

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Conclusions

The energy plots show agreement.

Peaks are shown in the acceleration plots due to the impact of the two frontal beams (nose and base)

The results from DoE show the optimum levels of each factor for every selected output. Level 2 for factor A (Angle) and level 1 for factor B (Width) are selected.

Angle= 58.6 deg.

Width = 486 mm.

Final nose topology

12

Preliminary design

Objectives checklist

The frame topology packages and supports all the components and protects the pilot integrity with a total weight of 32 Kgs.

The frame topology fulfills the Minibaja West regulations and the operating conditions.

The chosen frontal nose topology reduces the impact effects over the pilot

9% of

weight reduction

22% of

acceleration reduction

13

Future Work

Use more components and greater detail.

Use computational dummies to estimate more closely the acceleration and impact effect over the pilot.

Simulate different impact conditions.

Acknowledgments

This work could not have been done without the support of AltairEngineering, Livermore Software Technology Corporation, the Partners for the Advancement of Collaborative Engineering Education (PACE) program and the ITESM Toluca Minibaja Racing Team.