femfat

Spring Edition 2007 - No. 11
FEMFAT in the virtual process chain
– the countdown begins
No doubt you have already flipped through
the schedule and noticed that we have once
again put together a powerhouse of innovative
presentations and presenters. For example,
allow us to point out BMW with Fatigue
Calculation of short fiber-reinforced composites based upon results from injection moulding simulation and Influence of ageing on
the deformation- and TMF-behaviour of aluminum cylinder heads; DaimlerChrysler with
Use of virtual iteration in commercial vehicle
development and Fatigue assessment of
welded structures based on nodal forces;
Nissan with Basic study on fatigue life prediction of body panel notches; MAN with
Fatigue analysis of multiaxially loaded engine
components using FEMFAT MAX: A field report
on the correlation between analysis and
experiment; Hyundai with Root cause investigation of cylinder head failure of a commercial
diesel engine; Ford with Exhaust systems
durability with dynamic loadings; Volkswagen
with Structural durability of vehicles on 4poster test rigs. Moreover, you will hear the
plenary lecture From process to fatigue design: A unified approach by Prof. Dang Van
(École Polytechnique) and the guest lecture
by Prof. Steffan (TU Graz) titled Accident
reconstruction by means of simulation.
Interesting user presentations and our own
presentations round off the program.
The 45-minute user forum is also new. The
FEMFAT Team will answer your questions in
an open discussion.
Enjoy 3 informative, innovative and relaxing
days in Steyr at the FEMFAT User Meeting
from May 9 to May 11, 2007 (details at
www.femfat.com or take advantage of the
online registration option).
Helmut Dannbauer
FEMFAT 4.7 – Fast and effective
Contents:
FEMFAT in the virtual process chain the countdown begins _________ 1
FEMFAT 4.7 – Fast and effective _ 1
Evaluation and interpretation
of results in FEMFAT___________ 2
FAQs:
• What are the effects of the
individual surface treatments? _ 3
• How can temperature-dependent
material properties be taken
into consideration? ___________ 3
Courses/Events _______________ 4
News/Tips ____________________ 4
Event calendar ________________ 4
Imprint _______________________ 4
Visit our website:
www.femfat.com
A large number of user requests for extensions have been incorporated into Version 4.7.
However, by their participation in research
groups and integration of the knowledge
gained by the FEMFAT developer team, technical advances are not neglected in Version
4.7 either.
The analysis is accelerated further by group
parallelization and node filters (WELD, SPOT).
The analysis of fiber reinforced plastics is
now allowed by employing direction-dependent
material properties and Zago's non-linear
damage exponent. You needed a constant
stress load case in TransMAX and had to
add this extra case to your stress data? You
have generated your own load signals for
simple load situations (Excel or editor)?
There's no longer any need, FEMFAT 4.7 now
provides these options directly. And if you
have previously added your duty-cycles by
hand, they are now managed much more
comfortably by the Result-Manager. The appearance of the user inter face has been
further developed towards a "user-friendly
interface", in TransMAX in particular the input
mask is now clearer and more concise (table).
You have previously defined the wrong preferences when setting up the FEMFAT job or
selected the wrong groups before generating
the scratch file? This is hardly even possible
in Version 4.7 and if it does happen you
simply tell FEMFAT which scratch files to keep
and which new ones to generate:
But probably the greatest advantage in this
version belongs to users of FEMFAT WELD in
conjunction with FEMFAT VISUALIZER.
A flexible management system for welding
seam geometries and their really simple
definition via the VISUALIZER makes analyzing
welding seams a completely new experience.
More details at the User Meeting!
Axel Werkhausen
FEMFATNEWSLETTER
Spring Edition 2007 - No. 11
Evaluation and interpretation of results in FEMFAT
Beside the usual options for evaluating FEMFAT results via numerous
external post-processors (Hypermesh, MEDINA…) or with the aid
of the FEMFAT VISUALIZER, FEMFAT also provides a number of
other valuable tools for visualization and analysis of analysis results.
These options will be introduced below using a few useful tips.
Representation of the rainflow matrix
After the damage analysis is complete it is possible to visualize
the rainflow matrix in a three dimensional way in the "Visualization"
menu. In BASIC this is the pre-defined spectrum, in MAX it is the
result of the rainflow counting of the cutting plane stress of either
the most damaged or a selected node, depending on the setting
used in the "Analysis Parameters" menu (Fig.1). Note that the
settings must be made before performing the analysis.
If other nodes are of interest after the analysis, an appropriate
group can be
very quickly generated and reanalyzed using
"Create group
around node".
The maximum and the
unit stress values of
every channel are output to the femfat.cms
and femfat.cus files
for all nodes of the
DETAILED RESULTS
group. The maximum
stresses are the result
of multiplying the largest channel factor of
the load-time histor y
by the unit stress of
Fig. 4
the *.cus file, which
in turn represent the largest cutting plane stress.
The histories of the cutting plane stress, the partial damages and
the accumulated damage for the nodes of the histor y group are
saved in the history files (*.esh, *.pdh, *.tdh). These histories can
be visualized using the "Visualization" dialog.
Critical load case
Fig. 1
Figure 2 shows the rainflow matrix for the DIN15018 equivalent
stress, because the relevant node is a weld node.
Fig. 2
Fig. 3
Three visualization options are available for scaling the rainflow
matrix z-axis:
• Number of cycles of each spectrum element, default (Fig. 2),
• Damage contribution to total damage (Fig. 3),
• Damage in terms of the load cycle number.
Analogous visualizations are also possible for the residuum rainflow
matrix (for the non-closed cycles).
How are rainflow matrixes interpreted?
• It can be seen from Figs. 2 and 3, for example, that the lion's
share of the damage originates from comparatively few cycles
at a relatively low mean stress but high amplitude stresses.
• A very rough "matrix landscape" often indicates poor statistical
security of the spectrum (too shor t a duration with a random
load-time history).
• If the damage of individual load cycles exceeds ~0.001 one enters
short-term strength and the prognosis safety generally falls.
Once the MAX analysis is complete, a combination of 2 time points
can be output for a selected zone (Fig. 1). Generally, these represent
a close approximation for damage evolution in the load-time history.
The advantage of this simplified load combination (which can be
analyzed using BASIC) consists of the accelerated variant analysis
due to shorter turn-around times.
An ASCII file in *.dat format can be generated for NASTRAN with
the appropriate load definitions. This file contains three load
situations, created on the basis of the local stress history in the
cutting plane.
As can be seen in Fig.
5, the times at which
the equivalent stress
histor y achieves its
max/min value are
searched for. Fig. 6
shows the channel
factors for both of
these times.
FEMFAT now generates a NASTRAN load
data file from the oriFig. 5
ginal NASTRAN input
file and the channel factors, which represents the load situation
of the 2 times (Fig. 7). In addition, a third load case is formed
representing the amplitude stress. This NASTRAN load data file
can now be used together with the original input file to analyze
component deformations and stresses. The subsequent deformation
animation can provide valuable indicators of where design improvements are most effective.
It is now possible to ver y quickly carr y out operational strength
analyses using BASIC in order to quantify the effects of improvements.
2D visualization is possible just as easily as logarithmic scaling of
the z-axis. Diagram title, axis labeling, text size and background
color can all be specified by the user and in conjunction with the
snapshot function provide ideal opportunities for analysis documentation.
"History" and "Detailed Results" files
In a MAX analysis it is possible to generate ASCII files containing
detailed information for the nodes of the histor y group and the
detailed results group (see "Groups" dialog).
2
Fig. 6 channal factors
Fig. 7 NASTRAN input file
Continued on page 3
Spring Edition 2007 - No. 11
FEMFATNEWSLETTER
Haigh diagram
The Haigh diagram can be very helpful when analyzing the FEMFAT
results. Once again, the material and the local component Haigh
diagram, in which all local influence factors are included (relative
stress gradient, mean stress, temperature, etc.), can be visualized
together for the critical or the selected node (Fig. 1). Additionally,
the corresponding working points, defined by the equivalent amplitudeand mean stress, are displayed for each analyzed cutting plane.
The working point of the critical cutting plane can be emphasized.
For example, the representation in Fig. 8 shows that in this case
amplitude- and mean stress are from the same type of load (here:
bending). The working points of all cutting planes are located on
the straight line R = const = 0. In Fig. 9, in contrast, a point cloud
results, because here a constant mean bending stress was superimposed on a shear stress amplitude (non-proportional).
Fig. 8
Fig. 9
Moreover, it is possible to observe that the mean stress for the
node being considered is in the positive range (tension). If an
analysis for endurance safety factor is involved, the computed
safety factor is just below 1 here, because the critical cutting plane
is just outside the range of the component Haigh diagram.
Klaus Hofwimmer
FAQs
What are the effects of the individual surface treatments?
Besides the material, component geometry and stress conditions,
the manufacturing process has a major influence on the fatigue
behavior of a component.
In FEMFAT the following surface treatments are available:
• Shot peening
(to FKM, Eurocode or BS),
• Rolling
(to FKM),
• Carburizing
(to FKM),
• Nitriding
(to FKM),
Here, the condition prior to nitriding can also be taken into consideration. Tempered or normalized are possible.
• Inductive hardening (to FKM),
• Flame hardening
(to FKM).
Fig. 1 "Node properties menu" for the current group
For these treatments it is important that the Technological size at
3D nodes is given in "Node properties" (see Fig. 1). This technological
size is automatically determined from the mean shell thicknesses
for shell structures. For example, the technological size is the wall
thickness of a tube or the diameter of a shaft at the point where the
sur face treatment is carried out. Other influences, such as the
relative stress gradient and the material strength are automatically
taken into consideration by FEMFAT.
The Surface treatment factor provides a good option for incorporating
experiences from testing into analysis. This directly alters the local
endurance stress limit.
One common technological influence is the Surface roughness,
which can be assigned to the current group. The S/N curves of the
material data are generally defined for a smooth, un-notched specimen
for alternating tensile-compressive loading. This means that a change
in the surface roughness also changes the endurance stress limit,
the slope and the endurance cycle limit of the local S/N curve at
the node, including as a function of the material itself. In the methods
listed under "Influence factors" one can also select between mean
roughness depth Rz (to TGL or FKM) or the maximum roughness
depth Rt (IABG) of the assessed component surface. The former
TGL Standard - replaced by the FKM Guideline in 1994 - is no longer
recommended.
FEMFAT also includes an option for taking the Tempering condition
into consideration for tempered steels. If the tempering condition
changes (= new ultimate tensile strength) all governing material
parameters are adapted to the new tempering condition.
Following this, do not forget to activate the process influences in
"Influence factors" (sur face roughness, technological parameter
Marco Fahrner
influence, tempering influence...)!
How can temperature-dependent material properties be
taken into consideration?
FEMFAT provides an
option for defining temperature-dependent
material parameters
(static and dynamic) and
thus to take them into
consideration in the
operational strength
analysis. The simplest
solution is to import an
existing material from
the FEMFAT material database, e.g. the cast metal AlSi12CuNiMg.
Right at the bottom of the "Material
data" dialog there is an entry titled
"Properties at high temperature". Here,
value pairs consisting of the temperature and the corresponding material
parameter can be entered (currently
7 in all, 12 properties from FEMFAT
Version 4.7 upwards).
Attention should be paid that the
strength parameters correspond to the
imported basic parameters at 20°C.
For a user-defined assessment of the
temperature influence at least the
temperature-dependency of the ultimate tensile strength and the
alternating stress limit must be given.
The remaining temperature-dependent material parameters can be
estimated automatically by FEMFAT – although it is better to provide
more temperature-dependent material proper ties, such as the
pulsating stress limit, for example.
This extended material can now be saved to the material database
once again using the "Write to materials database" command and
be used for subsequent analyses. It is adopted automatically for the
current FEMFAT session.
A nodal temperature distribution must now be defined as an "isothermal
influence". Do not forget to activate the isothermal temperature
influence in "Influence factors" and to change the method used to
Marco Fahrner
user-defined.
3
FEMFATNEWSLETTER
Spring Edition 2007 - No. 11
FEMFAT courses - Dates
Engineering Center Steyr, St. Valentin
17-18 April 2007
20-21 June 2007
12-13 Sept. 2007
21-22 Nov. 2007
Fatigue life/Damage and
safety factors for simple loads,
comprehensive FE-interfaces
and material database
Engineering Center Troy, Detroit
8 June 2007
7 September 2007
14 December 2007
Prices (exkl. VAT):
per delegate
Euro 770,pro additional delegate
from the same company
Euro 610,Uni/research society
Euro 300,Including 2 month FEMFAT evaluation license
Information: [email protected]
*** NEWS *** NEWS *** NEWS *** NEWS *** NEWS *** NEWS *** NEWS *** NEWS ***
CIMAC Congress Vienna 07
3D-postprocessor
All relevant large engine manufacturers meet in
the Hofburg in Vienna between May 21 - 24 to
exchange views. FEMFAT also plays in this league
and we are invited to give a presentation on HCF
and LCF (TMF) prediction for engines. In addition,
we will inform and advise you in the accompanying
exhibition.
On May 25, on the occasion of the Post Congress
Tour, there will be an ECS company tour, following
a visit to Miba and subsequent tour of the
monastery of St. Florian. At the same time ECS
will be holding a "Open House" and will be available
for individual visits and consultation (also see
www.cimac.com).
Anneliese Schmidthaler
Multiaxial fatigue
e-CADFEM
Welded structures
In order to take the varying uses of FEMFAT by
our customers into account, we will provide FEMFAT
licenses at CADFEM's LSP platform. All modules
will therefore be available for use on a day-by-day
basis (calendar days) via LSP (License Service
Providing).
A signed license contract and a starting advance
fee of 2,000 Euros entitle you to use the software
on 10 individual days. If you don't have them
already, the software and manuals are provided
as a http download.
Axel Werkhausen
*** TIPS *** TIPS *** TIPS *** TIPS *** TIPS *** TIPS *** TIPS *** TIPS *** TIPS ***
Info for exhibitors at the FEMFAT User Meeting
Spot-joined structures
Thermo-mechanical fatigue
PLAST
Local plasticity
Exhibitors wanting to take part in the FEMFAT User
Meeting can find information on prices, the range
of activities, location and hotels on FEMFAT's
homepage www.femfat.com -> FEMFAT User
Meeting 2007 -> Exhibitors. Take advantage of
the online registration option or contact me directly
for advise.
Anneliese Schmidthaler
Presentations available on the website
Over the years, ECS has amassed a considerable
collection of publications thanks to their regular
presentations at technical events.
BREAK
We do not want to keep these interesting
documents from our customers and have
therefore provided a link on our homepage, see
the Service/Support menu.
Eberhard Dutzler
Static safety factors
STRAIN
Virtual strain gage/
Measured strain damage
FEDIS
Sub-modeling
Engine dynamics/Acoustics
simulation
Analysis & preparation of data
Imprint:
Engineering Center Steyr GmbH & Co KG
Steyrer Strasse 32, A-4300 St. Valentin
Tel: +43 7435 501 303,
Fax: +43 7435 501 300
[email protected]
www.femfat.com
4
Event calendar
SAE 2007 World Congress
8th 4 WD Congress
Austrian foundry conference
28th Intern. Viennese Motor Symposium
FEMFAT User Meeting 2007
CIMAC 2007
NAFEMS World Congress
ABAQUS International Users’ Conference
SF2M Fatigue under Thermal Loading
11th EAEC - European Automotive Congress
FEMFAT Road Show
SimPEP (Simulation in product development process)
9th Int. Forum VDI Commercial Vehicles
2nd ANSA & µETA International Congress
Materials Science & Technology 2007 Conference & Exhibition
24th Danubia-Adria-Symposium
FEMFAT Road Show
16th Aachen Colloquium 2007
SAE 2007 Comm. Vehicle Engineering Congress & Exhibition
Fatigue Design 07
Detroit
16-19 April 2007
Graz
18-20 April 2007
Steyr
19-20 April 2007
Vienna
26-27 April 2007
Steyr
09-11 May 2007
Vienna
21-24 May 2007
Vancouver
22-25 May 2007
Paris
22-24 May 2007
Paris
23-24 May 2007
Budapest 30 May-01 June 2007
Stuttgart
12 June 2007
Würzburg
14-15 June 2007
Munich
14-15 June 2007
Halkidiki
14-15 June 2007
Detroit
16-20 Sept 2007
Sibiu
19-22 Sept 2007
Goteborg
02 Oct 2007
Aachen
08-10 Oct 2007
Rosemont 29 Oct-01 Nov 2007
Senlis
21-22 Nov 2007