SIST-TP CEN/TR 16303-2:2012
(Main)Road restraint systems - Guidelines for computational mechanics of crash testing against vehicle restraint system - Part 2: Vehicle Modelling and Verification
Road restraint systems - Guidelines for computational mechanics of crash testing against vehicle restraint system - Part 2: Vehicle Modelling and Verification
The aim of this Technical Report is to provide a step-by-step description of the development process of a reliable vehicle model for the simulations of full-scale crash tests giving the reader a first synthetic summary of problems encountered in the different steps of the vehicle modelling process.
Rückhaltesysteme an Straßen - Richtlinien für Computersimulationen von Anprallprüfungen an Fahrzeug-Rückhaltesysteme - Teil 2: Fahrzeugmodellierung und Überprüfung
Ziel dieses Fachberichts ist es, eine schrittweise Beschreibung für den Entwicklungsprozess eines zuverlässigen Fahrzeugmodells zur Simulation von voll maßstäblichen Anprallprüfungen zur Verfügung zu stellen und dem Leser eine erste grundlegende Übersicht der Problematik bei den verschiedenen Schritten des Verfahrens der Fahrzeugmodellierung zu vermitteln.
Dispositifs de retenue routiers - Recommandations pour la simulation numérique d'essai de choc sur des dispositifs de retenue des véhicules - Partie 2: Composition et vérification des modèles numériques de véhicules
Le présent Rapport technique a pour but de fournir une description pas-à-pas du processus de mise au point d'un modèle fiable de véhicules pour les simulations des essais de choc en vraie grandeur donnant au lecteur un premier résumé synthétique des problèmes rencontrés dans les différentes étapes du processus de modélisation de véhicules.
Oprema cest - Smernice za računalniške simulacije preskusnih trčenj v sisteme za zadrževanje vozil - 2. del: Oblikovanje vozil in preverjanje
Ta del standarda CEN/TR 16303 je informativen. V njem so podane splošne informacije o razvoju modela vozila za simulacijo preskusnega trčenja v sisteme za zadrževanje vozil. Opredeliti je mogoče dve različni kategoriji modelov vozil. V prvi kategoriji je podroben model (običajno končni element) vozila ali dela vozila, ki se običajno uporablja v avtomobilski industriji za oceno strukture in strukturnih lastnosti vozila. Drugi tip modela vozila (končni element ali večdelni sistem) se običajno uporablja za oceno zmogljivosti pregrade pri simulaciji preskusnega trčenja v polnem obsegu. V tem primeru mora biti model manj podroben, da se zagotovi stroškovno učinkovito računalniško orodje za analizo več različnih scenarijev trčenja. Hkrati je treba natančno poustvariti pravilne inercijske lastnosti in zunanjo geometrijo vozila. Ta del smernice je namenjen obveščanju uporabnika o vseh potrebnih informacijah za razvoj celovitega in učinkovitega numeričnega modela vozila za pravilno simulacijo trčenja (zgoraj navedena druga kategorija vozil). Zelo podroben model ni primeren zaradi prevelikega dviga računalniških stroškov. S tega stališča se lahko model vozila obravnava kot orodje za analizo trčenja. Cilj tega tehničnega poročila je zagotoviti opis vseh korakov v postopku razvoja zanesljivega modela vozila za simulacije preskusnih trčenj v polnem obsegu, v katerem je naveden prvi sintetični povzetek težav, ki se lahko pojavijo v različnih fazah postopka oblikovanja vozila.
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST-TP CEN/TR 16303-2:2012
01-marec-2012
2SUHPDFHVW6PHUQLFH]DUDþXQDOQLãNHVLPXODFLMHSUHVNXVQLKWUþHQMYVLVWHPH]D
]DGUåHYDQMHYR]LOGHO 2EOLNRYDQMHYR]LOLQSUHYHUMDQMH
Road restraint systems - Guidelines for computational mechanics of crash testing against
vehicle restraint system - Part 2: Vehicle Modelling and Verification
Rückhaltesysteme an Straßen - Richtlinien für Computersimulationen von
Anprallprüfungen an Fahrzeug-Rückhaltesysteme - Teil 2: Fahrzeugmodellierung und
Überprüfung
Dispositifs de retenue routiers - Recommandations pour la simulation numérique d'essai
de choc sur des dispositifs de retenue des véhicules - Partie 2: Composition et
vérification des modèles numériques de véhicules
Ta slovenski standard je istoveten z: CEN/TR 16303-2:2012
ICS:
13.200 3UHSUHþHYDQMHQHVUHþLQ Accident and disaster control
NDWDVWURI
93.080.30 Cestna oprema in pomožne Road equipment and
naprave installations
SIST-TP CEN/TR 16303-2:2012 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
---------------------- Page: 1 ----------------------
SIST-TP CEN/TR 16303-2:2012
---------------------- Page: 2 ----------------------
SIST-TP CEN/TR 16303-2:2012
TECHNICAL REPORT
CEN/TR 16303-2
RAPPORT TECHNIQUE
TECHNISCHER BERICHT
January 2012
ICS 13.200; 93.080.30
English Version
Road restraint systems - Guidelines for computational
mechanics of crash testing against vehicle restraint system -
Part 2: Vehicle Modelling and Verification
Dispositifs de retenue routiers - Recommandations pour la Rückhaltesysteme an Straßen - Richtlinien für
simulation numérique d'essai de choc sur des dispositifs Computersimulationen von Anprallprüfungen an Fahrzeug-
de retenue des véhicules - Partie 2: Composition et Rückhaltesysteme - Teil 2: Fahrzeugmodellierung und
vérification des modèles numériques de véhicules Überprüfung
This Technical Report was approved by CEN on 8 November 2011. It has been drawn up by the Technical Committee CEN/TC 226.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland,
Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2012 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TR 16303-2:2012: E
worldwide for CEN national Members.
---------------------- Page: 3 ----------------------
SIST-TP CEN/TR 16303-2:2012
CEN/TR 16303-2:2012 (E)
Contents Page
Foreword . 3
Introduction . 4
1 Scope . 5
2 Normative references . 5
3 General considerations on the modelling techniques of a vehicle . 5
4 Step by step development of a vehicle for crash test analysis . 7
5 Validation procedures of a vehicle for crash test analysis . 8
Annex A Recommendations for the mesh of Finite Element vehicle models addressed to crash
simulations . 11
Annex B Recommendations and criteria for multi body vehicle models addressed to crash
simulations . 22
Annex C Test methodology . 23
Annex D Phenomena importance ranking table for vehicles . 27
Annex E Phenomena importance ranking table for test item and vehicle interaction . 29
Bibliography . 30
2
---------------------- Page: 4 ----------------------
SIST-TP CEN/TR 16303-2:2012
CEN/TR 16303-2:2012 (E)
Foreword
This document (CEN/TR 16303-2:2012) has been prepared by Technical Committee CEN/TC 226 “Road
equipment”, the secretariat of which is held by AFNOR.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
This document consists of this document divided in five Parts under the general title: Guidelines for
Computational Mechanics of Crash Testing against Vehicle Restraint System:
Part 1: Common reference information and reporting
Part 2: Vehicle Modelling and Verification
Part 3: Test Item Modelling and Verification
Part 4:Validation Procedures
1
Part 5: Analyst Qualification
1
In preparation
3
---------------------- Page: 5 ----------------------
SIST-TP CEN/TR 16303-2:2012
CEN/TR 16303-2:2012 (E)
Introduction
This part of CEN/TR 16303 is informative. It gives general information for the development of a vehicle model
for crash test simulation against vehicle restrain system.
Two different categories of vehicle models can be identified. The first category consists of a detailed model
(usually finite element) of a vehicle or of a portion of it, typically used in the automotive industry to assess the
structural performance and properties of the vehicle. A second type of vehicle model (finite element or multi-
body), instead, is typically used to assess the barrier performance in the simulation of full-scale crash tests. In
this case, a less detailed model is required, in order to obtain a computationally cost-effective tool for the
analysis of several different crash scenarios. At the same time, it is mandatory to reproduce faithfully the
correct inertial properties and outer geometry of the vehicle.
This Part of the guideline is meant to provide the user with all the information necessary to develop a
complete and efficient numerical model of a vehicle in order to properly simulate a crash event (second
category of vehicle above). It is not convenient to use a very detailed model, because of the unaffordable
increase in the computational costs. In this perspective, the vehicle model can be regarded as a tool for the
analysis of a crash event.
4
---------------------- Page: 6 ----------------------
SIST-TP CEN/TR 16303-2:2012
CEN/TR 16303-2:2012 (E)
1 Scope
The aim of this Technical Report is to provide a step-by-step description of the development process of a
reliable vehicle model for the simulations of full-scale crash tests giving the reader a first synthetic summary of
problems encountered in the different steps of the vehicle modelling process.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
N/A
3 General considerations on the modelling techniques of a vehicle
3.1 General
Particular attention shall be paid on the modelling of vehicular kinematics and of the components that realize
it: front and rear suspensions, wheels, steering system, etc. The geometry of the vehicle shall be reproduced
correctly to simulate the interaction with the barrier. The model shall include only significant parts and few
details (internal parts should be modelled only regarding their inertial properties, etc.) in order to reduce the
computational cost of the model.
3.2 Finite Element and Multi-body approaches
Two main modelling approaches can be considered, using two different analysis tools: the Finite Element
Method (FEM) and the Multi-Body (MB) approach. Both methods are widely known and broadly used in many
fields of engineering, including the Automotive Industry.
The first method allows the user to build a very detailed vehicle model and to assess global results such as
the barrier or vehicle performance in a crash test as well as the stress data in a local area of the vehicle. As a
counterpart, a FEM analysis requires significant computational costs, thus proving less valid for parametric
studies where a large number of simulations may be required.
Crash tests finite element (FE) simulations are usually run with a dynamic, non-linear and explicit finite
element code. Computer runtime is usually significant, with the order of 30-40 hours on a 2,4 GHz personal
computer for the simulation of a full-scale crash test with an effective simulated time of 0,25 second. In fact,
the model must include not only the vehicle model, but also several meters of roadside barriers (depending on
the barrier type, up to 80 meters of barrier) to faithfully reproduce the interaction between the vehicle and the
barrier and the boundary conditions. The integration time step is controlled by the minimum dimension of the
smallest element of the FE mesh, therefore, the mesh size shall be a trade-off between the need for
geometrical and numerical accuracy and computational cost: large elements guarantee a high time step but
poor accuracy of the model and possible instabilities, while small elements give a better accuracy but a
smaller time step. General criteria for the mesh can be identified. The most significant parts of the vehicle
shall be modelled explicitly with a detailed mesh (vehicle body, wheels, etc.). Other parts can be modelled
implicitly, reproducing their inertial properties (engine) or their function and kinematics (suspension and
steering systems).
On the other hand, the MB approach consists roughly in modelling the vehicle as a number of rigid bodies
connected by means of joints with specified stiffness characteristics. The method is particularly suitable to
assess the kinematics of the vehicle, while less applicable to determine data about levels of stress and
strains. When reliable and validated data are available, the MB approach is very useful to perform parametric
5
---------------------- Page: 7 ----------------------
SIST-TP CEN/TR 16303-2:2012
CEN/TR 16303-2:2012 (E)
studies, since the computational cost of the analysis can be dramatically less than that of the corresponding
FEM analysis.
3.3 General scheme of a vehicle
Three main categories of vehicles can be identified:
a) passengers cars;
b) heavy goods vehicles (HGVs);
c) buses.
Despite their differences, basically in terms of mass and geometry, they share many common elements:
frame;
body;
suspensions (front and rear);
wheels;
steering system;
glasses;
engine block;
vehicle’s interiors.
Regarding the vehicle structure, it must be pointed out that two main different structural options can be
identified: the body-on-frame vehicle, typical for trucks and HGVs and the unit-body vehicle, typical for
passenger cars. In the first case, three structural modules that are bolted together to form the vehicle structure
can be identified: frame, cabin and box or bed (for a pick-up truck for example). In the second case, the
vehicle combines the body and frame into a single unit constructed from stamped sheet metal and assembled
by spot welding or other fastening methods. This structure is claimed to enhance whole vehicle rigidity and
provide for weight reduction.
Suspensions can also be subdivided into two main groups: dependent and independent. Generally,
independent suspensions are used for passenger cars and dependent suspensions are employed in
commercial vehicles and buses.
Wheels can be single or coupled. The latter configuration is customary for rear wheels of HGVs and buses.
3.4 Vehicle validation considerations
Once the vehicle model has been built, it shall be validated with simple tests, both components tests and full-
model tests, observing the global response of the model and the behaviour of the single parts (suspensions,
wheels). Numerical stability of the model shall be assessed. Subsequently, the model can be used to simulate
full-scale crash tests.
The same validation approach shall be applied both to FEM and MB modelling. This document can be applied
to different modelling techniques, codes or vehicles. Despite different models, the same level of validation
shall be required if these models will be applied during the certification process.
6
---------------------- Page: 8 ----------------------
SIST-TP CEN/TR 16303-2:2012
CEN/TR 16303-2:2012 (E)
Some general comments can be emphasized to accurately predict ASI and THIV, as calculated from a vehicle
body mounted accelerometer:
a) correct representation of stiffness, strength and inertial properties of the vehicle body
⇒ part strength, crush mode and timing of front wing, engine firewall, bonnet, A Pillar, floor and
other parts affect the accelerations recorded;
b) correct representation of tyre interaction with the vehicle body, and hence tyre stiffness
⇒ for stiffer barriers especially, how the tyre loads the sill and wheel arch affects the
accelerations;
c) accurate capturing of steering, suspension motion, suspension spring and damper properties
⇒ for weak post systems in particular, longitudinal acceleration is greatly influenced by whether
a wheel strikes a post, which can be determined by how the front wheels react/steer from
previous strikes;
⇒ lateral accelerations are affected by the vehicles ability/inability to steer
d) sufficient detail for modelling is required for representative vehicle behaviour
⇒ reducing the model detail and integrity cannot be substituted for lack of computational
resource;
⇒ accelerometer sampling rate can affect results and needs to set at an appropriate level to give
results convergence;
e) a combination of element size and time step can produce mass scaling of the vehicle. Mass scaling
should be kept to a minimum (aim at less than 2 %) as mass added to the vehicle on initialisation could
affect the impact results. The added mass should not be concentrated in critical areas.
In building a model we make assumptions on what effects are important and to level of accuracy to capture
those effects. It is only by conducting a physical test that we discover what physical effects actually occur, and
the relative importance of those effects.
It is also possible that poorly constructed models can produce, what appear to be accurate high level results
that match test e.g. peak ASI, THIV and PHD, however, the underlying accelerations can be far from reality.
Therefore detailed analysis of the elements making up the high level results need to be fully understood.
4 Step by step development of a vehicle for crash test analysis
Annex A refer to the development of a Finite Element model of a vehicle. In particular:
A.1 focuses on the vehicle components to be modelled, describing extensively the function of the
component and its role in the model as well as some of the ad hoc techniques to achieve an efficient
model of the part. On the basis of these considerations the user can basically develop any vehicle model,
be it a passenger car or a pick-up truck.
A.2 deals with organisation aspects of the model. Models, in fact, often need to be used by different
organisations and pass from user to user. It is, therefore, important that the models have a standard
structure and an organisation predictable and easy to understand. A modular model structure is
recommended and extensively presented in this annex.
7
---------------------- Page: 9 ----------------------
SIST-TP CEN/TR 16303-2:2012
CEN/TR 16303-2:2012 (E)
A.3 a brief presentation of material models suitable for dynamic analyses is provided. Materials and their
properties are fundamental aspects of a reliable model, since the vehicle models that are objective of this
manual are going to be used for the simulation of a dynamic event.
A.4 includes specific recommendations on the mesh features.
Annex B refer to the development of a Multi-Body model of a vehicle. In particular:
5 Validation procedures of a vehicle for crash test analysis
5.1 General
This clause deals with the validation phase of the model. Significant numerical tests are recommended to
check the stability and reliability of the model.
5.2 Test methodology
5.2.1 General
The finite element model and the multi body vehicle model shall be validated with the same requirements and
limit.
The vehicle will be considered validated, for a certain class of impacts, if the comparison between simulation
and testing will fit inside the limits described by this Validation Roadmap (tests description is in Annex C).
The Validation Roadmap includes several simple tests made to ensure the numerical stability and the
capability of the numerical model. There are two classes of tests: component test and full scale vehicle test.
5.2.2 Components tests
Simulated tests shall be performed on vehicle components to demonstrate the capabilities of the sub
structures.
The tests of components involve mainly the suspension system; they require simulations and correlations with
experimental tests. The results from tests on front and rear suspension should be compared with simple
pendulum tests.
Description of tests is in C.1
5.2.3 Full scale vehicle test
During these phase all the vehicle shall be modelled.
Different typologies of tests are scheduled:
Idle tests: this analysis is needed to guarantee the stability of the vehicle (Description of test is in C.2);
Linear/circular track tests: this second typology is made to control the performances of the vehicle while is
moving or turning with a fixed or variable radius (Description of tests are in C.3);
Curb test: The vehicle model is forced to override curbs to test the response of the suspension system
and wheels to small impacts (Description of tests are in C.4);
Full-scale vehicle test: these tests are made in order to assess the global response of the vehicle while
impacting against a rigid wall and a deformable barrier impacts (Description of tests are in C.5).
8
---------------------- Page: 10 ----------------------
SIST-TP CEN/TR 16303-2:2012
CEN/TR 16303-2:2012 (E)
5.3 Acceptance criteria and results to be provided
The simulations described in Clause 6 of this guideline are required to demonstrate the stability of the model
regarding numerical integration and suspension system. The model shall respond without any instability
during all the simulation.
In Table 1 are described all the result that shall be provided for each test:
Table 1 — Vehicle test list purposes and results
N° Type of simulation Scope of simulation Results to be provided
Verify the correct Animation showing the movement
behaviour of both the of the suspension. Load deflection
1.1 Isolated suspension shock absorber and the history of the load transferred to the
failure of the system wheel.
Wheel orientation versus time
Verify suspension
Animation showing the movement
kinematics and loading
Suspension load. Each of the suspension. Load deflection
unloading capabilities.
1.2.1 wheel shall be loaded history of the load transferred to the
Uncoupling of shaking /
separately. wheel.
steering movement (for
Wheel orientation versus time
front wheels).
Suspension load.
Verify suspension Animation showing the movement
Frontal suspension
kinematics and loading of the suspension. Load deflection
and rear suspension
1.2.2 unloading capabilities. history of the load transferred to the
wheel shall be loaded
Suspensions coupling wheel.
separately.
due to stabilizer bar. Wheel orientation versus time
Symmetrical load
Suspension load.
Animation showing the movement
Frontal suspension
Verify suspension of the suspension. Load deflection
and rear suspension
1.2.3 kinematics and loading history of the load transferred to the
wheel shall be loaded
unloading capabilities wheel.
separately. Non-
Wheel orientation versus time
symmetrical load
Acceleration time histories.
To verify stability of the
2.1 Vehicle in idle Kinetic and total energy time
vehicle model itself
histories.
To verify stability of the Acceleration time histories.
3.1 Linear track. vehicle, steering and Kinetic and total energy time
suspension system. histories.
To verify stability of Acceleration time histories.
3.2 Circular track. vehicle, steering and Kinetic and total energy time
suspension system histories.
To verify stability of the Acceleration time histories.
Curb testing:
4.1 suspension and steering Kinetic and total energy time
Both front wheels
system histories.
To verify stability of the Acceleration time histories.
Curb testing:
4.2 suspension and steering Kinetic and total energy time
Both rear wheels
system histories.
To verify stability of the Acceleration time histories.
Curb testing:
4.3 suspension and steering Kinetic and total energy time
Right front wheel
system histories.
9
---------------------- Page: 11 ----------------------
SIST-TP CEN/TR 16303-2:2012
CEN/TR 16303-2:2012 (E)
Table 1 (continued)
N° Type of simulation Scope of simulation Results to be provided
Curb testing: To verify stability of the Acceleration time histories.
4.4 Left front wheel suspension and steering Kinetic and total energy time
system histories.
Curb testing: To verify stability of the Acceleration time histories.
4.5 Right rear wheel suspension and steering Kinetic and total energy time
system histories.
Curb testing: To verify stability of the Acceleration time histories.
4.6 Left rear wheel suspension and steering Kinetic and total energy time
system histories.
Full scale crash To verify the capability of Acceleration time histories.
5.1 against a rigid wall suffering strong Kinetic and total energy time
deformations histories.
Full scale crash To verify the capability of Comparison with experimental
against a deformable representing the results according to the Validation
5.2
barrier. interaction with a real Roadmap
barrier.
5.4 Verification of model validation
Model validation should be verified by the Acceptance Body according to the validation Guideline. To preserve
the property of models, these simulations could be run using restart files created at time zero. With this
technique simulations can be run without having the original models.
The Acceptance Body, using his results, must verify the time histories reported in the validation report.
5.5 Standard Reports and Output Parameters
The validation activity shall be described inside a report. The validation report shall comply with the format
given the Reporting Guideline and has to be included in the documentation enclosed with the vehicle model.
For the model validation the comparison between experimental tests and simulation shall be reported
according to this Validation Roadmap.
This documentation shall contain also the history of the model and the use in already performed activities. The
history shall contain also the modifications applied to the vehicle and the justification for that.
10
---------------------- Page: 12 ----------------------
SIST-TP CEN/TR 16303-2:2012
CEN/TR 16303-2:2012 (E)
Annex A
Recommendations for the mesh of Finite Element vehicle models
addressed to crash simulations
A.1 Component to be modelled
A.1.1 Frame
The function of the frame is to support all the major components or sub-assemblies that compose the
complete vehicle: engine, transmission, suspensions, body, etc. As already mentioned, two different types of
vehicle structure can be used:
a) separate frame;
b) integral or chassisless construction.
The first solution (separate frame), although quite popular in the past, is nowadays implemented only for
commercial and off-road vehicles. In this case the frame is a distinct component and typically it consists of two
C cross-section side members linked by cross members, thus contributing to the overall torsional stiffness of
the structure. All these members are connected by means of rivets and bolts.
Instead, in the integral type the chassis frame is welded to, or integrated with, the body. A further development
is the chassisless construction, where no chassis frame can be discerned.
Excluding the chassisless construction, in a FE model both side and cross members are usually modelled with
shell elements, while connections are realized with rigid spot weld elements. Since experience shows that
these links are very unlikely to fail, it is not necessary to include any failure criteria. In order to obtain the
correct interaction between side and cross members, it is appropriate to define a contact interface between
them, thus reproducing the effective torsional stiffness of the frame.
The connection between the frame and the other parts of the vehicle should be realized according to the parts
to be linked. Generally, most of the vehicle components are rigidly linked to the frame or are coupled with
some kinematical joints.
A.1.2 Vehicle body
The main role of the vehicle body is that of protecting the occupants from external events (wind and
atmospheric phenomenon) and providing and adequate aerodynamics. Nevertheless, during a crash against a
restraint system, the vehicle body can influence the behaviour; in fact sometimes the metal sheet of which it is
composed can break and snagged between parts of the barrier. Hence the body geometry and material
properties should be modelled as accurately as possible.
Customary, this part of the model is made by shell elements characterized by an appropriate thickness. The
material by which the vehicle body is usually made is metal: steel or aluminium alloy. These materials can be
easily modelled as elasto-plastic in almost all the finite element codes.
A.1.3 Suspensions
Suspensions are those parts of the vehicle which link the wheels to the frame; therefore they are essential in
determining the vehicle dynamics. During impacts against restraint systems they play a relevant role in
determining the vehicle trajectory and dynamical behaviour (roll, pitch and yaw motion).
11
---------------------- Page: 13 ----------------------
SIST-TP CEN/TR 16303-2:2012
CEN/TR 16303-2:2012 (E)
As mentioned above, two main categories of suspensions can be discerned: dependent and independent. The
former type is the simplest suspension and consists of one rigid axle to whose extremities wheels are
connected. Usually, the linkage between this axle and the vehicle is made by springs (coil or leaf type).
Instead, independent suspensions are characterized by a more complex geometry and can have different
designs. Most car vehicles use independent suspensions and a great variety of constructive solutions have
been developed during the years.
Suspensions can be modelled in two main ways: explicitely or implicitely:
Explicit modelling means that almost all parts which compose the suspension system are modelled (using
shell, solid and discrete elements). That requires a deep knowledge of the geometry of all the
suspension’s parts and a quite long meshing work. Only springs and dampers can be implicitly modelled
by discrete elements.
Implicit modelling, instead, is made by defining a simplified kinematical system which should behave as
faithfully as possible respect to the actual suspension. The equivalent kinematical system should be
realized combining some simple rigid bodies (small shell or solid elements) by means of different joints, in
order to define a sort of “multibody” component inside the finite element model. Discrete spring and
damper elements should be defined in the appropriate locations, in order to model the stiffness and
damping properties of the actual suspension.
The advantage of an implicit modelling is the great reduction of computational cost and the possibility to easily
modify the stiffness and kinematical properties of suspensions; but, on the other hand, the realization of a
trustworthy equivalent system can be more difficult than simply meshing the suspension.
A.1.4 Wheels
Wheels are those components of the vehicle which guarantee the contact with the roadway and permit the
movement by rolling. Wheels are directly involved in the impact against a restraint system; the correct
modelling of these parts can have a strong influence on the overall behaviour of the vehicle.
The main characteristic which should be modelled is the possibility to roll freely. In many finite element codes
this is achievable defining a joint between two rigid bodies which allow a relative rotation along a specific
direction.
The second factor to be taken into consideration in the development of the numerical model is the tire.
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.