Durability is a requirement for product development across numerous industries. In transportation and mobility, each vehicle system has to meet a different number of miles or years of use under warranty. Testing and simulation both play a vital role in accelerating the design cycle and reducing time to market, while meeting such targets.
Many of us learned about the Goodman diagram in our university experiences, and even calculated fatigue life using an S-N diagram, but that can only take us so far. Modern multiaxial strain-based fatigue analysis is required to drive our designs as they get lighter and challenge the boundaries of previous applications.
To do this, fe-safe combined with advanced FEA can account for:
• Plasticity in metals, and hysteresis effect
• Residual stresses from forming, installation or shot peening
• Mean stress effects
• Surface roughness in steel and cast iron
• Complex variable amplitude and non-proportional loading
• Mission statements and proving ground loads
• Welded joint fatigue and many other features
At this moment, no one can guess the location of “lowest lives” given the complex inputs and interactions of these effects. So we need software to run the calculations all over the model.
DURABILITY DRIVEN BY ISIGHT
Let’s take an example from the life sciences: Adding modern multiaxial fatigue to the parametric optimization of a hip implant allows the designer to select the best design candidate from over 200 variants in less than a day when Abaqus and fe-safe are automated in Isight. Compare 12 days’ validation on one single test machine to the 60 days on 40 test machines that would be required if all of those variants were evaluated in the lab.
SHAPE OPTIMIZATION & DURABILITY TARGETS
Taking the same hip implant concept further, shape optimization can be used to fine-tune the design. In Tosca Structure, shape optimization can be driven by an objective to minimize damage in the area of lowest life. Along with constraints to keep the mass the same and to allow manufacturing and assembly, this target led to an overall increase in life of almost 5 times over the selected design from the earlier Isight optimization. In this way both optimizers work together, to provide the best solution for patient and designer.
DURABILITY TRAINING OFFER
SIMULIA offers a variety of fatigue theory and application courses designed to teach the user how to include durability calculations in the development process for many applications:
Introduction to fe-safe (2 day)
In this course you will learn how to set up and run various fatigue analyses using fe-safe. The course includes hands-onworkshops using your choice of FEA solution (Abaqus, ANSYS or Nastran). Topics include: Using the fe-safe GUI and group settings, introduction to fatigue theory, loading definitions in fe-safe, algorithms and analysis process, infinite life methods, and diagnostic tools.
Automating Analysis in fe-safe (1 day)
This course focuses on the details of automating fe-safe analyses using command line, batch file or macro files and the basics of integrating fe-safe analysis with Isight, Tosca or ANSYS Workbench.
Theory & Application of fe-safe/Rubber (2 day)
This course provides hands-on software workshops for using Abaqus and fe-safe/Rubber to run a rubber-fatigue analysis. Topics include rubber material fatigue properties, crack-growth calculations for rubber, variable-amplitude loading, constant loading, multiaxiality and post-processing.
For more information, visit the Training section on our website.
Custom Fatigue Courses
Lectures are available for custom courses on metal fatigue including stress-based and strain-based fatigue, rainflow cycle counting, fatigue properties, infinite life and high-cycle fatigue, theory of critical distances, PSD fatigue and more.
Request a custom course, here.
For more information, visit our services page.
A wide range of videos about durability, including Developing a Design Process for Durability, can be found in the training section of the SIMULIA Learning Community.
