w h i t e p a p e r Siemens PLM Software Lifecycle simulatio

the automotive industry

Lifecycle simulation in the automotive industry

Advances in dynamic response with NX Nastran

Siemens PLM Software Accelerated product development cycles are just one symptom of an extremely competitive automotive http://www.77cn.com.cnpanies have been driven to embrace and extend virtual product development processes,replacing time intensive physical tests with the use of up-front performance simulation.

w h i t e p a p e r Siemens PLM Software

http://www.77cn.com.cn/nx

the automotive industry

Lifecycle simulation in the automotive industry

T able of contents

Introduction1

Model reduction technique2

Modal space computations3

Modal solution metrics4

Dynamic analysis of rotating

components4

Enforced motion of structures6

Interfacing to multi-body analysis7

Closing remarks9

Bibliography9

the automotive industry

Introduction

Accelerated product development cycles represent just one symptom of an extremely

competitive automotive http://www.77cn.com.cnpanies have been driven to embrace and extend

virtual product development processes,replacing time intensive physical tests with use of

up-front performance simulation.

The dynamic response of body and powertrain affects every area of customer satisfaction.

Engineers are required to run simulations over very wide frequency ranges with models

exhibiting extreme problem sizes.Speed and solution robustness are critical.T echnically

speaking,modal solution approaches are much preferred because of efficiency.Methods of

generating the modal spaces are the subject of constant improvements,and the physical

response quality may now be evaluated by the engineer.

Siemens PLM Softwares’Lifecycle Simulation vision and strategy recognizes the value of

pervasive simulation throughout the product lifecycle.Performance simulation is carried out

throughout the lifecycle during concept and design studies,manufacturing and testing,through

operation of the product,to maintenance and disposal.For example,simulation during

automotive design often involves,among others,the rotation of some flexible components,

external dynamic excitation of structures,and the mechanism type motion of some parts of a

complex structure.These are accommodated by rotor dynamic modal frequency response

analysis,an alternative enforced motion computational strategy,and an interface to external

multi-body simulation tools.

Manufacturing and testing phases are also increasingly important.Some manufacturing processes

require a detailed physical simulation.A“simple”example from the world of civil engineering is

a road bridge.In many cases bridges are not completely stable during the build process and are

hence the focus of extensive simulation studies.The automotive world expends enormous

efforts to simulate manufacturing processes and build sequencing as part of quality programs.

Many industries have an extensive history of using simulation in support of test programs and also

of enhancing simulation models with stiffness and other data derived from tests

Similar considerations are valid for the maintenance and disposal phases of product lifecycles.

Maintenance solutions regaining the damaged physical integrity of a structure,frequently needed

in the aerospace industry,are also subject of extensive computer simulations.

The main focus of simulation was always on the operational phase of products;however,

nowadays the operational scenarios traverse a much wider range of physical phenomena.In the

automotive industry,for example,these scenarios include the incorporation of rotating

components into the classical vibration analysis,the simulation of a wide spectrum of external

excitations,and the coupled execution of multi-body analysis.

Very large problem sizes are the result of the desire to increase the fidelity of the physics

simulation,and advanced computational methods are needed to support these ever increasing

sizes of the finite element models of lifecycle simulation scenarios.

1

the automotive industry

Model reduction technique

In the computational methods area we see a renaissance of the modal solution method, currently often called the model reduction technique.Modal dynamic solutions in industrial finite element analysis have a long history that began in the1960’s1.Their original emergence was to help overcome the very serious limitations of the computer hardware of the days.Due to the engineering intuition required to make the methods useful,they stayed mainly a specialist’s tool for decades.With the emergence of high performance computers in the1980’s and their ability to analyze very large finite element models,it seemed that the technology had its days numbered.

Meshing technology advances in the past two decades and the emergence of lifecycle simulations,however,resulted in an explosion of problem sizes,contributing to renewed interest in the technology.The technology is summarized in the following.The equation of motion of a free structure after applying the boundary conditions and eliminating the constraints is:

.(1)

The matrices M,B,and K are the finite element mass,damping,and stiffness matrices,and the subscript f refers to the free partition of degrees of freedom of the model.The vector P contains the forces applied to the model and the vector u is the dynamic response;both of these are potentially frequency or time dependent.

Converting equation(1)to modal space,the equation of motion transforms to:

,(2)

where

(3)

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