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Engine oil pans optimization within a vehicle crash scenario
B.Charlet
6th European Altair Technology Conference - 2013
AbstractTitle:
Engine oil pans optimization within a vehicle crash scenario
Author:
• Bernard Charlet
• PSA Peugeot Citroën, La Garenne, France
• +33156477407
Abstract
Engine downsizing is a strong trend in automotive industry. Engines are getting lighter and smaller and are installed in
bigger cars. As a consequence the integrity of the engine to vehicle crash, either for compliance to safety rules or
different Euro NCAP's crash tests, is no longer guaranteed. It becomes necessary to maintain impact resistance while
optimizing engine mass. PSA initiated a collaborative work with Altair, in order to test latest optimization
developments.
Topological optimization is a powerful way to achieve minimum mass within geometrical constraints. The challenge
here was to work with variable load and strongly non-linear behaviour. In our case the specifications were a set of
time-dependant forces applied on the engine. These forces were extracted from a complete crash analysis. The aim
was to avoid engine collapse during crash time. The ESLM method was first tested but convergence issues were
detected. Then manual samplings of the loads were done and several section patterns were tested: samplings of the
time step and peaks load to take into account. Eventually, a new geometry that reaches the goal was identified, that
allows a gain of 50% resistance with 10% of additional mass.
26th European Altair Technology Conference - 2013
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Introduction
PSA PEUGEOT CITROËN
3,500,000 vehicles sold worldwide (2011)
Europe’s number two carmaker with a 13 % share of the market
Innovations and new technologies to reduce CO2 emissions
Downsizing policy to reduce engine capacity without reducing power
The protection of the occupants of the vehicles, is a priority topic of R & D for PSA
Peugeot Citroën, most of recent models reach 5 stars at crash-tests Euro NCAP.
6th European Altair Technology Conference - 2013
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Problem Definition
Implication of the engine in the scenario
Depending of the country, the semi barrier of EuroNcap’s test is :
• Either on the left when steering wheel is on the left.
• Or on the right when steering wheel is on the right.
In PSA vehicle, gear boxes are on the left side and engine on the right side.
• When semi barrier is on the left the gear box is part of the crash scenario.
• When semi barrier is on the right, it’s the engine which then play an important role
Downsizing: New and lighter engine in vehicle
Lower parts (Oilpans) being mainly aluminum shells
Specification from the vehicule are forces with time duration
6th European Altair Technology Conference - 2013
Definition of Specifications
Needs
Transfert of forces toward the lower part of car’s body
Limitation of the intrusion of the engine in the front body panel
Points of impact
Impact from the transmission bar to the oilpanthrough an impactor
Impact of subframe on the lower part of impactor
Specifications
Loads vs time on the engine
from crash simulations ��
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Initial crash analysis
Current State
Performances to be achieved
In this case, a collision happens between the subframe and the engine block and between the transmission rod and the engine block. Loads target are measured with Times Histories (TH).
This Times Histories allow us to observe the behavior of the system and define the performance to be achieved.
6th European Altair Technology Conference - 2013
Objectives of the study
Develop a method to optimize an engine oil pan within its environment with a crash type scenario in order to improve its behavior.
Proposal of new oilpan definition, based on this method, with respect to the performances below :
� Increases the strength of the oil pan
� Delays breaking
� Minimizes the mass added to the global system
76th European Altair Technology Conference - 2013
6th European Altair Technology Conference - 2013 8
Setting up of the study
PSAALTAIR
engineering
• Selecting the type of optimization
• Find the most appropriate method to
perform this optimization
• Writing methodological manual
linearization for topology optimization
of a crash type loading in OptiStruct
Define : • The current problems and goals
• The kinematics of the crash scenario
• The sensors to observe
Role of the two company during the project :
9
Optimization Process
Crash analysisCrash analysis
Linearization of crash loadingLinearization of crash loading
Sub-model & Subcases for optimizationSub-model & Subcases for optimization
Topology optimizationTopology optimization
Integration of the optimization results in a crash analysis to validate the concept obtainedIntegration of the optimization results in a crash analysis to validate the concept obtained
6th European Altair Technology Conference - 2013
A new crash analysis must be performed using a model that contains the design space and TH output to retrieved loads for Optimization (Contacts forces, External forces… ).
The TH (Loads vs time) of this new analysis will be used to identify the instants to take into account for the linearization.
10
Model setup for crash analysis
6th European Altair Technology Conference - 2013
6th European Altair Technology Conference - 2013 11
Model setup for optimization
Linearization of crash loading
Problems: how to represent crash behavior with simple static loadcases (forces)?
No rules for linearization of crash loading. This is based on experience and tests
Assumption selected for optimization : find peaks and scanning around these peaks
Creation of the sub-model for optimization.
Optimization can be done on a sub-model
The efforts of the dynamic analysis must be recovered at the limits of the sub-model
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Optimization
Subcase setup for optimization
The calculated equivalent static loads from the crash analysis are considered as separate load cases, and these multiple load cases are used in the linear response optimization.
Optimization formulation
Variables : Element density of each element in
the design space.
Objective : Minimize weighted compliance
Constraints : % Fraction of design volume
Optimization is performed on a submodel �
Faster convergence of the optimization
6th European Altair Technology Conference - 2013
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Optimization
Optimization results
Quick validation
The validation method is independent of the
CAD
New model is obtained by directly
integrating the results of the optimization in
the initial crash simulation
We retain only the elements which the
density is higher than 0,6
6th European Altair Technology Conference - 2013
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Validation results
Crash analysis
Global observations
Improved behavior of the oilpan
�Performances improved by 78%
�6 % more weight
6th European Altair Technology Conference - 2013
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Optimization Process : Summary
Original part
Initial crash
simulation
Crash simulation
with DS
linearization
Optimization
ValidationInterpretation
6th European Altair Technology Conference - 2013
Prospect
On the path to integration…
A new part is drawn:
• Base on result of optimization
• Including already some of the process
requirement
Performance:
• 10 % more weight
• Fulfillment of specifications
16
The effective use of topological otimization in strongly non-linear loads
Optimization is used here to tell the designer how the part will be reinforce
6th European Altair Technology Conference - 2013
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Thank you for your attention
6th European Altair Technology Conference - 2013