engine oil pans optimization within a vehicle crash scenario

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

• [email protected]

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.


3

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.


4

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


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 ��


6

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.


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


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


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 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

12

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


13

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


14

Validation results

Crash analysis

Global observations

Improved behavior of the oilpan

�Performances improved by 78%

�6 % more weight


15

Optimization Process : Summary

Original part

Initial crash

simulation

Crash simulation

with DS

linearization

Optimization

ValidationInterpretation


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


17

Thank you for your attention


engine oil pans optimization within a vehicle crash scenario

Technology

crash time

crash analysis6t

new crash analysis

lighter engine

engine capacity

engine blockand

engine collapse

vehicle crash scenariob