A lot of steel structures such as cranes, heavy machinery and other equipment subjected to repetitive loading is highly likely to develop cracks or failures because of the fatigue damage.
The cost of every hour of equipment downtime is usually very expensive, making it mandatory to perform residual life calculations or fatigue checks.
The calculation procedure usually consists of the following important steps:
With the help of SDC Verifier, this procedure is completely automated and can be performed directly in the Ansys Mechanical model.
It makes no difference whether it is a new design check, a residual
life analysis or a crack investigation – it is very important to collect
and properly transfer to the finite element analysis (FEA) model all
necessary information about the working conditions and loading
history of the structure (or the estimated loads for a new design).
A realistic Basis of Calculation results in more precise
calculation results.
The combination of loads and impacts is usually set by the
standards and requires several groups of linear combinations of
single load results. For example, according to FEM 1.001 fatigue
testing, an engineer should combine: gravity, effective loading,
acceleration and dynamic impact in all possible scenarios, taking
into account partial load factors, dynamic and gain coefficients
for the Strength group of load combinations with a safety factor
of 1.5. All the same conditions plus the effect of wind must be
combined for the Wind group of load combinations with a safety
factor of 1.33. The next group will be an exceptional load scenario
where the same effects have different partial load factors and a
safety factor of 1.1.
At this point, the SDC Verifier offers the engineer a user-friendly
interface for combining the loads into a matrix of load sets and
groups, taking into account all the safety factors and partial
load factors. Not only does this simplify the processing of a
large amount of load history data, but it also shortens the Ansys
Mechanical solution time because each load effect will be solved
once with Ansys only and then linearly combined using SDC
Verifier.
In the second stage, there are three important characteristics that should be set to obtain realistic fatigue verificationresults:
Weld type is crucial because fatigue problems are most
likely to occur on welds. Therefore, in the S-N curve
fatigue analysis method it is necessary to establish a
classification based on a weld type to assign a curve.
The general curve of the stress level against endurance
is shown below.
The first challenge is determining which elements of your
FEA model are welds. The SDC Verifier Weld finder tool
solves this problem by introducing automatic one-click
weld recognition. It automatically finds all welds in the
FEA model based on thickness change, material/property
change, joint angle and user-defined rules or exceptions.
After recognition is complete, the classification must
be determined for all welds in the model. SDC Verifier’s
selector helps you create components for all welds, weld
intersections, weld tips, etc. Moreover, since the Weld finder
reorients the stresses and forces in the welding directions, different
classifications can be made along the weld, perpendicular to the
weld, and for shear.
Material type is often sourced from Ansys Mechanical or can be
easily set in SDC Verifier (there is an automatic reminder if some
of the material properties are not set).
The next step is the verification itself. SDC Verifier performs the fatigue check according to different standards in the Offshore, Heavy lifting, Heavy machinery, Maritime, Shipbuilding and Civil industries. The following standards are currently available: Eurocode 3 (EN1993-1-9, 2005)
SDC Verifier uses the Allowable Stress Design method. All
formulas are open, so the user can see all the formulas behind
the calculation kernel, including descriptions and explanations of
where they have been taken from.
Before running the calculation, the user only
needs to select the part of the model
to be tested and the loads to be
used in the calculation. All
calculations are performed
in the background,
however it is possible to
access a log file of the
calculation details
if full control of the
analysis is required.
In the initial phase,
modifications to
the design seem to
be a minor part of the
project execution time.
But if the results are not as
expected and improvements
are required, then the complete
review process usually takes much
longer than expected.
SDC Verifier is template-based, which means that if the check
has been done once, then in the future, routine work will be
automated on the basis of calculation, recognition, and the
calculations themselves. All the user has to do is change the
design and solve the model. Subsequently, the data is updated
and a report is generated with two mouse clicks, to complete the
entire procedure.
This is a huge time saver and reduces deadline pressure because,
as we all know, most design modifications and improvements are
done at the last minute!.
Last, but not least, is the automatic reporting. Few people like
writing reports. However, there is still a great deal of documentation
that must be provided to a manager, customer or certification
organization.
The SDC Verifier Report designer helps you to create a templatebased
document that contains the following info: model
description, loads and boundary conditions, Ansys results output,
and code validation results. All data can be presented with an
extensive range of plots and tables.
Full control over the structure of the tables makes it possible to
present the maximum or detailed output result for the complete
model or individual components over the loads and combinations,
or to prepare an overview table of the various load parameters.
With adjustable view settings and selectors, the user
can create any output or check result at a
different angle/view for the full model,
some part or cut.
With SDC Verifier that allows
the code to be verified
directly in Ansys,
there is no longer
a need for routine
manual calculations,
spreadsheets, or
complicated testing
and verification
procedures to check
the fatigue damage or
to predict the residual
life of a structure. In
addition, you can generate
a full calculation and
verification report to submit
to the certifying organization or
customer.
software
SDC Verifier technology allows you to perform an in-depth study on the load-bearing structures of large assemblies, modeled with Beam, Shell and Solid elements. In addition, it is capable to recognize automatically joints and welds in order to properly performs rule checks.
sdc-verifier civil-engineering
CASE STUDY
Sport equipment design is characterized by the fact that a fundamental part of a product success depends on the athlete’s feedback.
sports modefrontier ansys ls-dyna