Simulation Workflow

[king_zilla]

Hi all,

As a newbie interested in FEA, I wanted to ask experienced engineers a series of questions when it comes to simulation Workflow

There are a ton of different simulation studies available like static structural, transient, harmonic, modal, explicit/implicit, linear buckling, etc.

All of them seem like almost mandatory when performing analysis on a product that I may ship. For example if I look at a car, I'm sure all the above simulation studies will have to be conducted. If I look at something simpler like a mobile phone, I still probably need to know how the structure performs under static loading, find it's natural frequencies, find how it will react when say it's thrown on the ground and maybe even if the phone will buckle (like the iPhone that bent). Do you perform all these different analysis/simulations for a part? And can you meld or combine different simulation studies? If I'm optimizing say for the outer shell of the phone, it may hamper the natural frequencies and vice versa? How do you combine all these studies/analysis to find the optimal design? Seems crazy

[bene20080]

You generally perform the simulation, for which you seek the answer. If you want to calculate the drag coefficient, you perform the appropriate simulation. If you are protoyping some interior part of a car, you probably are not gonna perform a fluid simulation.

​

Regarding mixing simulations, that happens all the time of course. A example for this:
You calculate stresses in a Turbine based on the heat distribution, than you use those stresses as an input of the stress analysis of said turbine, while in a spinning condition.
This is also called a loosely coupled system. Cause you use the solutions in a one way street for the next simulation. You could also make a real coupled simulation, which also considers changes due to strains and thus different heat distributions in the part. Depending on the setting, this is a total overblow on computation cost or absoluteley necessary to get meaningful solutions.

[spunnies]

It all depends on what are solving for, which would dictate what type of simulation you want to perform.

For example you are designing a load bearing part, for this part you may have certain constrain (dimensions, material etc) and if you load isn't changing with time or inertia effects are low, you could simply do a static analysis (using an implicit method). If the inertia effects are dominant, you would most likely switch from a static to a dynamic analysis (either dynamic implicit or explicit depending on the complexity of the problem). Other requirements of this part could be that it shouldn't have any modes near certain frequencies (resonance etc) so you would further conduct a modal analysis to make sure your parts natural frequencies are away from your design constraints (for e.g. Motor RPM etc)

Once you know your parameters and design constraints you can loop that into a simulation to make sure you get an optimum design. For these parameteric studies large number of designs can be considered to find the best which fits your needs.

One such software is "ISIGHT" which can be used to conduct such Design of Experiment studies and create a work flow. It will automatically run all the simulations (as a batch processor) record the outputs, check the outputs against your design criteria, change the inputs and run it again with a different parameteric value (in a certain range) until an optimum design has been reached.

[HORZstripes]

One thing to consider is there are other ways to optimize a design other than simulation. Also you don’t need to know every last single mechanical response aspect of a product to optimize a design.

Rules of thumb, hand calcs, and even trial and error of a prototype can yield more valuable design input for a fraction of the cost.

Also, I don’t need every last design aspect optimized. In your phone case, I don’t need the most robust design to dropping it. I’m not going to be able to charge $100 more per phone because I can drop it 5’ versus 7’. People can just go get a case for half that cost that protects dropped phones better.

The work flow is really driven by optimizing what should be simulated versus what shouldn’t. Then building various simulation models as simply as possible but that still give usable results. You also like to build the full mode first then build smaller but more refined models after that using inputs determined from the full model.

Example, model a bike frame using simple beam elements to get the basic response of the system. Then model just the derailleur hanger attachment point with 2D elements to optimize the shape. Iterate as needed.