5th EHTC 2011, 8-9 Nov 2011, Bonn, Germany

Harald Hasselblad, Volvo Car Corp.

Topology Optimization of Vehicle Body Structure

in the Early Design Phase

Harald Hasselblad Volvo Car Corporation

5th EHTC 2011, 8-9 Nov 2011, Bonn, Germany

Harald Hasselblad, Volvo Car Corp.

Based on a Master Thesis Project

Students:

• Sebastian Lövgren

• Emil Norberg Linköping University

Sweden

Supervisor

Harald Hasselblad Advanced Body Engineering

Volvo Car Corporation

Altair Engineering, AB Regional Office: Gothenburg

Sweden

5th EHTC 2011, 8-9 Nov 2011, Bonn, Germany

Harald Hasselblad, Volvo Car Corp.

State of the Art

Bolted components are commonly used for improvement of vehicle body stiffness.

Idea

Based on topology optimization identify locations and layout of beams in the front area for improved vehicle body stiffness.

Topology Optimization of Rod/Beams for Body Stiffness

Nissan

5th EHTC 2011, 8-9 Nov 2011, Bonn, Germany

Harald Hasselblad, Volvo Car Corp.

Optimization Problem

Min Compliance (Max stiffness)

s.t. mass constraint (volume fraction)

Industrial tradition: Mass minimization with performance constraint.

However, requirements and mass on topology model is of less importance.

General guidelines on architecture is sufficient.

Load Cases

A reduced model of the front of a vehicle has been used.

9 load cases divided into 4 groups, due to similarities, are applied related to:

• Torsion stiffness

• Lateral/Vertical stiffness

• Chassis loadings…

5th EHTC 2011, 8-9 Nov 2011, Bonn, Germany

Harald Hasselblad, Volvo Car Corp.

Design Space

Geometrical Restrictions

Connection Surfaces

Design space

5th EHTC 2011, 8-9 Nov 2011, Bonn, Germany

Harald Hasselblad, Volvo Car Corp.

Results from Topology Optimization

By NOT performing a weighted topology optimization, a knowledge base can be generated to support the design process.

Each load case has been optimized separately Good understanding of the specific architecture for each load case.

Torsion stiffness Vertical stiffness Lateral stiffness Chassis loadings

5th EHTC 2011, 8-9 Nov 2011, Bonn, Germany

Harald Hasselblad, Volvo Car Corp.

Performance of Optimized Topology

5th EHTC 2011, 8-9 Nov 2011, Bonn, Germany

Harald Hasselblad, Volvo Car Corp.

Visualize Topology Results

5th EHTC 2011, 8-9 Nov 2011, Bonn, Germany

Harald Hasselblad, Volvo Car Corp.

Benchmarking of Topology Allowed connection to

windscreen member

5th EHTC 2011, 8-9 Nov 2011, Bonn, Germany

Harald Hasselblad, Volvo Car Corp.

• For a light solution, reinforcements may be optimum instead of beams.

• Real stiffness and mass constraints should not be used in topology optimization when the target is to identify a global architecture.

• Large design volume compared to allowed result Beam details are limited because of mesh resolution.

Previous results has therefor been based on a stepwise approach. However, a “One-shot” method has also been used to find beam

structures. One-shot optimization: • Gradually increase VOLCFRAC until beam structure appears • Remove connection areas to prevent reinforcements

Problems Encountered

5th EHTC 2011, 8-9 Nov 2011, Bonn, Germany

Harald Hasselblad, Volvo Car Corp.

Topology Convergence Strategy

Different approaches for topology optimization

Stepwise

“One shot” with

different volume

fraction

“One shot” with

different volume

fraction and

contact reduction

5th EHTC 2011, 8-9 Nov 2011, Bonn, Germany

Harald Hasselblad, Volvo Car Corp.

Realization of Topology

Hollow circular beams were drawn based on topology result

• Translating topology into beam structure. • Size optimization of beams (tubes)

r2 r1

5th EHTC 2011, 8-9 Nov 2011, Bonn, Germany

Harald Hasselblad, Volvo Car Corp.

Realization and Size Optimization Torsion Loadcase Topology

Topology optimum

Beam realization

Load case

5th EHTC 2011, 8-9 Nov 2011, Bonn, Germany

Harald Hasselblad, Volvo Car Corp.

Realization and Size Optimization

5th EHTC 2011, 8-9 Nov 2011, Bonn, Germany

Harald Hasselblad, Volvo Car Corp.

Finding One Solution for all Load Cases

Reduced connection areas (To prevent reinforcements)

Problem formulation

Minimize mass

Subject to:

Compliance ≤ Current design

(For all load cases)

Topology result

Realization

• Remove reinforcements

• Translate topology into beams

• Size Optimization

No solution found!!

To remove the reinforcements reduced the performance

of one load case in such extent that the beams cannot

compensate for it.

5th EHTC 2011, 8-9 Nov 2011, Bonn, Germany

Harald Hasselblad, Volvo Car Corp.

Finding One Solution for all Load Cases

The knowledge of each load case is used to increase the performance in the

failed load case. Beams from the specific load case optimum are inserted into

the structure and a new size optimization is preformed.

Multi-Loadcase Optimum

Single Loadcase Optimum

5th EHTC 2011, 8-9 Nov 2011, Bonn, Germany

Harald Hasselblad, Volvo Car Corp.

Possible Use of Beam/Rod Architecture.

Summarize the results from each loadcase and combine them into a bigger solution

5th EHTC 2011, 8-9 Nov 2011, Bonn, Germany

Harald Hasselblad, Volvo Car Corp.

Summery and Conclusions

It is hard to know what material usage is necessary to make the results consist of beams instead of reinforcements.

Results should be treated as suggestions for the future realization process.

Create the design problem in such a way that no realizable solutions are prevented.

It is preferable to optimize each load case separately to create knowledge how to increase stiffness for a certain load case.

The results could work as architecture guidelines in early phases of the product development, or it could be used to find weaknesses in a structure.

5th EHTC 2011, 8-9 Nov 2011, Bonn, Germany

Harald Hasselblad, Volvo Car Corp.

Thank!