FEDEM Overview
Conceived, written and developed to solve real life engineering problems
The
Fedem Simulation Software™ provides both a technology platform and an
engineering framework for virtual testing of complex mechanical
assemblies with very high result accuracy and an efficient workflow. This is typically required for
product verification or virtual sign-off purposes in a professional
industrial engineering environment. In such applications, where
expensive and time consuming full scale physical testing is the only
alternative, it is necessary for the engineers to quickly and easily
obtain accurate information on both dynamic and structural properties
of a mechanical design. Also, to ensure sufficient accuracy, the
simulation solver must account for the mutual dependencies between
dynamic properties at the system level and structural flexibility at
the component level. These requirements can only be efficiently
satisfied through a non-linear structural dynamics approach.
Non-linear structural dynamics
In Fedem, a non-linear structural dynamics approach is utilized in
order to simultaneously solve structural deformations and 3D motion
dynamics in the time domain. The mechanical assembly to be simulated is
comprised of parts, each represented by a linear elastic finite element
model and coupled together with linear or non-linear joints. After a
DOF reduction of each part based on a dynamic superelement formulation,
the system equations are assembled and solved with respect to finite
element degrees of freedom. Fedem utilizes its own element formulations
and its proprietary solver to perform the model solution. This approach
provides several advantages over conventional methods:
- Mutual
dependencies between structural and dynamic properties are always
automatically accounted for.
- The
time domain solver is highly numerically stable since strain energy is
implicitly represented in the equation system.
- A
single stage integrated process replaces a conventional two stage
process of: (A) load generation (from physical test and/or multi-body
dynamics simulation), and (B) subsequent, separate, structural analysis
of each component.
- The
approach is practical for the engineer - its logic emulates real life.
Integrated
and efficient workflow
The process of modeling and evaluating dynamic and structural
properties of a mechanical assembly is highly integrated. When a
proposed design is to be verified and a finite element model of each
individual part in the assembly has been produced, the engineer has to
follow these logical steps:
- Build
the mechanical assembly by importing each finite element model,
positioning the parts relative to each other, adding joints, springs,
dampers, forces, control systems, etc. and specifying mechanism drive
functions.
- Define
and run the dynamic time domain simulation. Fedem automatically reduces
each finite element model to a superelement prior to running the time
domain solver. Reduced models can be re-used both for other dynamic
events and Fedem models.
- Post-process
and assess results. Dynamic results are readily available from the time
domain solver. Structural results are obtained by an integrated
superelement recovery process.
Efficient
user interface
An intuitive user interface provides a complete set of features to
create, solve and post-process a model in one common 3D graphical
environment. Dynamic results in the form of curves and animations are
available during and after model solution. Combined with the fast and
numerically stable Fedem solvers, the user interface facilitates an
engineering process with shortened turnaround times and quick access to
simulation results for a clearer understanding of the physical behavior
of the model.
Industry
standard formats
Finite element models are imported from NASTRAN bulk data deck files
ensuring compatibility with FE meshing tools.
Mechanism
drive functions can be linked with external data files in MTS RPC
III/Pro, nCode DAC or ASCII format. Simulations driven with such
external data can be switched from one event to another simply by
changing a file reference. Simulation results can be exported in MTS
RPC III/Pro, nCode DAC or ASCII format files.
Animations
can be exported in MPEG-1, MPEG-2 or AVI formats, and stills in JPG,
PNG, BMP or RGB/IV(3D only) formats.
Large
models and long time histories
Large FE meshes are easily handled due to the innovative use of
superelement technology utilizing a combined static and dynamic
reduction. Further, efficient modeling and post-processing is ensured
through high performance 3D graphics.
The
equations of motion are only solved for the reduced system and the
number of equations are independent of FE mesh sizes. This enables
simulation of long time histories, even for models containing large FE
meshes.
Complete
library of mechanism entities
A comprehensive set of mechanism entities ensures physically realistic
modeling. Entities include a complete joint library - optionally with
non-linear spring, damper and friction characteristics, discrete
springs and dampers, functions - optionally with references to external
data files, forces and control systems, etc. All entities have a 3D
graphical representation and all properties are accessible through user
interface components.
Control systems
To ensure accurate simulation of the interaction between structural
dynamics and control systems, a co-simulation technique is applied.
The
internal control system contains a library of compensators and
elementary control blocks. This enables basic modeling of supplementary
mechanism units such as hydraulic cylinders, actuators and electrical
drives.
In
addition to the internal control system, a Fedem - MATLAB/Simulink
interface is provided for modeling of more advanced control loops.
Tire
and road models
Tire and road models are provided to enable fully analytical vehicle
simulation. Currently, the MF-Tyre and SWIFT tyre models developed by
Delft-Tyre (TNO Automotive), and FTIRE developed by COSIN, are
supported. MF-Tyre and SWIFT are implemented through the Standard Tire
Interface (STI), while FTIRE implementation is based on the COSIN Tire
Interface (CTI). The complete Delft-Tyre libraries are provided as
add-ons.
Fast
structural recovery
Structural results are obtained subsequent to the time domain
simulation through an integrated superelement recovery process. A
complete set of strain and stress components can be recovered for all
elements and time increments. However, recovery can also be performed
individually on parts or even on pre-defined element groups for
selected time increments. Time history summaries, such as max/min
stress, are also provided.
Durability
assessment with nCode
Durability assessment is provided through a seamless interface to
FE-Fatigue from nCode International. For selected elements a
peak-valley extraction is performed simultaneously with the stress or
strain recovery from the non-linear structural dynamics solution. This
is used to calculate a rainflow matrix as input to the fatigue solver.
Durability analysis results can be viewed as contour plots on the model
in the 3D graphics environment. In addition, virtual strain gage
measurements can be obtained from the model.
Multi-event
duty cycle analysis
Result sets from different simulations can be combined in a multi-event
duty cycle analysis. An intuitive user interface provides a clear
overview on available result sets and duty cycle management.
Supported
platforms and system requirements
The Fedem Simulation Software runs on Windows NT/2000/XP. The solvers
can also be made available for major engineering platforms like the
HP-UX, SGI-IRIX and SunSolaris operating systems upon request.
Result file formats are cross-platform compatible and it is possible to
use a 64-bit unixbased supercomputer for solving, and a Windows computer
to do modelling, launcing of solvers and postprocessing.
For
a more comprehensive explanation of the modules of the Fedem Simulation Software,
please refer to the module description.
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