Transition to Simulation: Spectrum of FEA Analysis, Part 2
This month, we continue exploring the spectrum of FEA to include even more available tools. If you enjoy designing mechanical systems, you’ll naturally want to take every opportunity to develop the most robust and well-tested products.
February 1, 2019
If last month’s article about various types of finite element analysis (FEA) got your attention, keep reading. This month, we continue exploring the spectrum of FEA to include even more available tools. If you enjoy designing mechanical systems, you’ll naturally want to take every opportunity to develop the most robust and well-tested products. The following simulation tools will help you get there.
Dynamic Linear Analysis
If static linear analysis results are not detailed enough, or you already know that the study involves energy dissipation models, start considering dynamics. A good example of something that requires dynamics would be studying a streetlight pole that was lightly struck, or harmonics impacting a boat hull lamination.
Dynamics removes static constraints such as slowly applied constant loading, incorporates modal analysis and adds dampening effects. Dampening could be described as the energy dissipation of a structure. It’s generally broken down into three types of models: frictional effects, material dampening and viscous dampening. If this interests you, consider picking up a copy of the Mechanics of Vibrations for starters.
Due to the computational ease of generating a thermal solution, this analysis type is naturally a favorite among FEA experts. Thermal analysis tells the story of how heat transfers in solid bodies. You may ask why the solution processes so quickly. Temperature is a scalar, non-vector quantity. Each node of an element in the model only has one degree of freedom.
In static analysis our primary objective is to find displacement, and what’s analogous in the thermal world is temperature. Likewise, heat flux could be considered analogous to stress. Thermal covers three modes of heat transfer: conduction, convection and radiation.
The thermal analysis types can be broken down into steady state or transient conditions. Steady state focuses on bringing the analysis to equilibrium and a stabilized temperature field, whereas a transient thermal analysis incorporates heat power as a function of time. If considering a study of forced convection such as fluid flow cooling an engine, it’s important to understand that this dabbles in the realm of computational fluid dynamics (CFD). Vendors offer solutions where imported CFD results can be used in a thermal analysis.
Most people think of the word fatigue and may associate it with the feeling they get upon leaving the gym. For the simulation community, we recall instances where a product fails unexpectedly. If your design calls for repetitive loading in a safety critical application, a fatigue analysis should be performed. Broken down into low and high cycles, it’s important to understand which capability you are studying.
Software vendors may only offer one type, which is generally limited to high cycle. Stress-life based fatigue curves, commonly known as SN curves, describe the quantity of cycles until failure. As you dig into the details on how to set up and perform this analysis, it’s important to understand that many SN curves are derived empirically. Proper evaluation of the input values such as surface finish, corrosive environment and other factors plays a contributing role in the accuracy of the results.
Constraints and Topology-based Optimization
If you have been watching online videos of leading edge companies designing ultra lightweight robotic components with organic shapes, you’ve probably wondered how they devised those shapes.
Topology optimization leverages analysis objectives such as stiffness-to-weight ratio, or minimizing displacement based on assigned constraints and loads. Topology results will provide options on transitioning your initial CAD geometry into these organic masterpieces. Just remember, you’ll still have to check with the machinists to make sure your design can be manufactured.
There are several types of analyses that could assist you in validating your design. Leveraging the fundamental understanding of these different types of simulation tools will put you on par for preparing an even better design for your next project.
About the Author
Donald Maloy is a consultant analyst based in the greater Boston area. He also works as a certified simulation and mechanical design instructor for a software reseller.Follow DE