1 RENAULT – Marc ALBERTELLI

« RODIN Project »

Marc Albertelli Research engineer and coordinator of RODIN project

SIA Conference, 18-19 March 2015, France

Session - Optimization

RODIN Robust structural Optimization for Design in INdustry

Accepted within the framework of the 13th FUI call to project

July the 1st 2012 – July the 1st 2015

Labelled by :

With the support from BPI France, CRIF and CGY78

2 RENAULT – Marc ALBERTELLI

Plan

Motivations

Organization

Progress

Design cycle

Topics

Numerical simulation

Applied mathematics

Deliverables

Numerical tools

Methodology

4

production

Intents

Positioning

Target population

Industrial design center

Industries : transport, aeronautic, etc

Industrial expectations

Time savings (productivity)

Mass savings (material cost reduction, CO²)

3 RENAULT – Marc ALBERTELLI

Topology optimization : current process

CAD return Design space

Topology

optimization

+

Set of specifi. stiffness

durability

life cycle,

NVH

manufacturing

etc

Initial

design

Feedbacks

From industrial point of view, the method is attractive for the following reasons:

The execution is straigthforward (compared to parametric approach)

One does not need to create parameters, automate computation workflow, etc

It just requires a design space and the set of specifications

It no longer depends on the designer.

Mass savings : between 3% and 15%

Time savings : achievable but delicate to assess

Despite these advantages, we note that :

Topology Optimization is not systematically used,

The deployment remains modest,

It seems difficult to further enlarge the scope of applications,

And it appears that :

The method is often used for approximately designing simple components,

Engineers struggle to devise robust methodologies dedicated to more complex components,

The solution is just a concept

4 RENAULT – Marc ALBERTELLI

Our (technical) analysis

Threshold=0.1 Threshold=0.5 Threshold=0.9

1) Topology optimization consists in managing the density per element. density 0 the element has virtually diseappeared density 1 the element is full. The optimal shape is defined by the set of full elements.

2) The SIMP approach (or « power law ») clerverly proposes to relax the problem but :

- It does not lead to a clear solution

- There is a lot of intermediate densities that requires to manually adjust where the interfaces lies

- The user has to guess the most probable density threshold

3) The absence of sharp boundary makes difficult the management :

- Of manufacturing constraints (thickness, distance, etc)

- Of surface criteria (pressure, t°, acceleration, etc)

- Of design dependent load,

- Of the export of the solution

Alternative : the level-set method

1) A new way to characterize the shape

Given D, the « design space »,

The shape Ω, is characterized by a level-set function :

The boundary is now well defined. It is given by the iso-zero of the level-set.

The problem of SIMP approach does no more exist.

2) Two other ingredients :

\0

0

0

Dxx

xx

Dxx

ndssjJ ' dIRxtxtxtvxtt

,,0,.,,

5 RENAULT – Marc ALBERTELLI

Plan

Motivations of the projet

Organization

Progress of the project

Main purposes of the project

New process to design massive components Current process

Deliverables

A Topology Optimization tool based on the Level-Set method

An automatic CAD return tool

A new design process

In brief

Topology optimization has proved to be interesting

… but requires some changes to enlarge the scope of applications and to systematize its use

The challenges are : handling manufact. constraints, dealing with true analyses, automat., etc

A new technology is necessary, we choose « level-set method »

designer

simulation Decision maker

CAD return Design space Topology

optimization

+ CDC tenue

fiabilité

acoustique

durée de vie

contraintes de fab.

(fonderie, directe)

performance

etc

6 RENAULT – Marc ALBERTELLI

Some scientific and technical challenges

n°1 : Scale up of Level-set

Machinery level-set

Large scale optimization

Large scale simulation

Multi subcase, ….

n°3 : Analysis

Static linear

Modal analysis, Freq. responses

Material non linearity

Boundary conditions non linearity,

…

n°4 : Pre/post treatment

CAD return

Parametrized CAD

Mesh export

Bulk export, …

CAD return Design space Topology

optimization

+ Set of

specifi. stiffness

durability

life cycle,

NVH

manufacturing

etc

n°2 : Manufacturing constraints

Molding

Maximum and minimum thickness

Minimum distance

Curvature, …

Deliverables

Pre-treatment Optimization Post-treatment

TFC

Visual Env. Topolev (Topol)

Mesh export

Bulk export

CAD return

Visual Env. Bulk Nastran

CAD environment

ESI framework

From Nastran

CAD return Design space Topology

optimization

+ Set of

specifi. stiffness

durability

life cycle,

NVH

manufacturing

etc

7 RENAULT – Marc ALBERTELLI

Academic

Ecole Polytechnique, CMAP

University of Pierre et Marie Curie, labo. JLLions

Inria Bordeaux, Bacchus

Small and Medium Enterprises

Digital Product Simulation

Alneos

Eurodecision

ESI Group

Industrial partners

Renault (coordinator)

AIRBUS Group Innovations

Snecma

Partners

Plan

Motivations of the projet

Organization

Progress

8 RENAULT – Marc ALBERTELLI

1rst Use case

Air cylinder Support (Snecma)

followers

Engine mount (AIRBUS)

Engine mount (Renault) Pilot Use case n°1

...

FreqPropre

min

i

...

1

xxxVonMises

xxxHz

xxxraideur

xxxraideur

MASSEx

CDC

tenue

fiabilité

acoustique

durée de vie

contraintes de fab.

(fonderie, directe)

performance

etc

+ frequency responses

+ maximum thickness

+ Von Mises

+ molding constraints

+ eigenvalue

Solve min mass st stiffnesss constraints

Optimization algortithm dedicated to level-set approach

« level-set » machinery

Airbus and Snecma use-cases

Topolev result

SIMP result

Engine mount (1/2)

Impact of the threshold density

9 RENAULT – Marc ALBERTELLI

Engine mount (2/2)

Unambiguous solution, sharp boundary !

With molding constraints Without molding constraints

Extra use-cases (1/3)

10 RENAULT – Marc ALBERTELLI

Molding (2/3)

Maximum thickness (3/3)

Without max thickness control

11 RENAULT – Marc ALBERTELLI

Complete process

CAD return Geometry

optimization

Topology

optimization

Thank you

For your attention