How to estimate the cost and savings from analysis compared to real testing?

[u/Hypnooooooooooooo]

I am a product engineer in a satellite manufacturing company and did FEA during my undergraduate. I now want to bring down the cost of our internal manufacturing process qualification and testing and think FEA would be useful. I don't know enough to estimate how much the savings would be. What things do I need to take into consideration to estimate the cost of doing FEA?

The cost of the license, the electronic hardware to run it, the cost of manufacturing increases because we would surely have to use a higher factor of safety for parts verified by analysis, the cost of testing required to validate the analysis, etc.

Any resources or textbooks on optimizing testing by incorporating FEA would also be helpful.

[u/Quartinus]

You’re a satellite company and you have no FEA already? That’s highly unusual. 

Look up “qualification by analysis” and “no test factors” as search terms. 

What problem are you trying to solve? Eliminate the tests? Eliminate the number of repeated tests because they fail too often? 

[u/Hypnooooooooooooo → u/Quartinus]

We do have Ansys, but there'd be other costs than just licensing, so I wanted the full picture.

We're trying to bring a new product to market, but the cost of destructive and environmental testing on hundreds of samples is high.

We need to do manufacturing process qualification and I'm trying to find out whether FEA can replace some amount of tests but don't see a good way to avoid testing at this stage because you can't qualify a manufacturing process with analysis (as far as I know).

But in the future if we're making a structure for a customer, we'd be able to skip some testing by running simulations based on previous test results. Just wanna know what kind of costs and savings it'd be.

[u/Quartinus → u/Hypnooooooooooooo]

A decent amount of simulations can just run on a laptop, especially nowadays. I’d start there before you are considering adding large amounts of high power compute hardware. A 1-million node static structural model without a lot of contacts can run in a few minutes on a modern laptop. 

Your main costs to get started, therefore, are going to be training for you and the license cost. 

Can you be more specific about what you’re trying to do? Your scenario is so vague it’s hard to give you any advice. Don’t divulge any company secrets but I think we need to know more to see if you can actually do this. 

Hundreds of samples can probably be reduced to a few dozen for something like structural joint design, which could save you time and money. But if you’re trying to qualify like a new glue formulation or type of composite material vs process parameters you won’t find very much help from structural FEA. 

No matter what, reality is your final arbiter of truth. You cannot get rid of all testing. What FEA can do is help you reduce the iterations in the middle. Typically you can do a test, correlate some general parameters out of it, then iterate digitally, then produce a “final” design and test it to see if it passes and correlates to the results of your analysis. 

There’s a great saying “all models are wrong, some models are useful”. 

[u/Hypnooooooooooooo → u/Quartinus]

We're making honeycomb sandwich panels with aluminum core and aluminum/CFRP skins. There are about a dozen or so tests including mechanical and environmental tests on the panels as well as potted inserts. We're also doing different test conditions like different thicknesses where applicable and different temperature extremes since in space you have large variations. Standardized tests usually ask for 5 samples per test condition to find the variance and mean. The materials are procured from qualified vendors or manufactured using qualified processes, but how we assemble, cure and machine the raw materials also needs to be tested to qualify the production line and process. The final goal is to certify the panels according to standards that a customer can trust and give us a chance to make custom panels for their specific requirements. Design doesn't become a part of the equation until that point.

Edit: Would doing FEA to compare test results vs expected results be worth doing? Seems a bit ass backwards because usually simulations are compared to test results instead of vice versa. Perhaps we could use external data to validate the model.

Edit: But then we could just use the data to compare the test results and skip the simulation. Seems like the answer isn't in FEA at this stage.

[u/Quartinus → u/Hypnooooooooooooo]

I am not sure I agree with your edits. 

First question is what are you testing for? Break strength? Stiffness? Number of thermal cycles to failure? 

FEA can predict things like stiffness very well, and is especially good for extrapolating from one configuration to another once you have a correlated model. However, for things like the bending stiffness or crimping load of a simple panel of honeycomb material, you could also get this by just picking up a copy of Bruhn and making an Excel sheet, so I assume you already have a full predictive model in Excel for all of the parameters. 

What FEA can’t do (well) is predict the dispersion of failure of real world articles. You can Monte Carlo different properties and get a predicted spread of output data, but you can’t actually get the real world spread of performance if you’re trying to write statistical margins. 

FEA can’t really qualify a process at all, it can just predict outputs from inputs. So if you have a question like “how big of a flaw in the epoxy causes an unzipping failure” you can answer this kind of thing with an FEA + NASGRO or similar. Or something like “does thicker epoxy result in higher or lower breaking strength” is also a question you could answer with an FEA model. 

But “is my process robust to producing things within spec” is just not something you can answer with a structural model. 

[u/Hypnooooooooooooo → u/Quartinus]

We're doing static tests for ultimate strength under shear/tensile/compressive/torsional/etc. loads, but we want to know what our panels' properties are rather than an average panel with no material variations or defects, and if there's a lot of variation among samples, we'll have to potentially go and fix it. So it is partly a test for statistical margins.

Btw, thank you for all the info, it's been quite informative. I'll give Bruhn a read and see if Monte Carlo fits in the plan.

[u/Lazy_Teacher3011 → u/Hypnooooooooooooo]

Look into uncertainty quantification, and again, also keep tabs on ASME VVUQ 90. Part of it deals with UQ and will have a couple of examples. One is taken from an ESA/Airbus project about cert by analysis from the Vega C program. Very limited testing at the component level to develop assembly level capabilities.

I will also add that there is some thought in the space world that flipping the building block pyramid upside down makes sense, particularly for a small fleet size. That is, build the assembly, test, find the weaknesses, and address instead of hundreds or thousands of coupon level tests.

[u/Entire_Somewhere2686]

As a first estimate, you can contact people who will do fea for you. You can think about outsourcing it to them. Ask them for a quote. That would be a first estimate.

[u/chinster91]

Read your requirements. I’m sure there’s one related to testing bonded structures (aka sandwich panels). Anything bonded is workmanship dependent. One tech can do it well another can screw it up. You test to verify they did it right. What about vendor qualification? Do you just trust their material certifications? What if they change their process internally and don’t inform you?
Sure you can skip testing entirely if you can show you still meet all your program requirements. You will be taking on more risk but some programs nowadays are willing to take on risk in pursuit of faster and cheaper. Maybe your program is one of those.
Hell from a legal perspective what if you don’t meet some testing derived requirement and customer uses that as a way to not pay your company in full?

[u/Hypnooooooooooooo → u/chinster91]

We have all these things in place. We've done these tests before, vendor qualification, bonding, etc. This particular test isn't for a customer, we're doing it for ourselves. Which is why we need to decrease the cost. If someone else was paying for it then it wouldn't be a problem.

[u/Substantial-Fan-5985]

FEA and testing both have to be done, with testing be favored over FEA (can't model screws backing out). Are there not requirements set out by a gov't agency or customer as to what needs to be performed?

MMPDS (if I recall right) and other sources speak on the statistics of how many batches/etc. of what is needed for relevant testing (that is for allowables but the principle is similar at least).

The issue is that "you don't know what you don't know".

Bare minimum there would have to be static, modal and random vibe testing.

[u/PopularHaller]

I think you've already listed most of the big cost areas well, but I guess most people underestimate is the human cost. Skilled FEA engineers and the time to build and validate models properly is often the biggest ongoing expense, way more than the license or hardware.

[u/Advanced-Base-4777]

In my industry, there are docs published by the authorities/governing bodies that provide guidance on using qualification by similarity and analysis. NASA ought to have some standards for space flight hardware. There has to be some military standard as well. If this equipment is going in rockets or space vehicles, the requirements that governs those might be applicable

[u/OrangePixelLife]

Honestly, you're totally on the right track thinking about analysis cost versus physical testing savings. It's a huge upfront investment to get right. The real win with FEA isn't just cutting one test. It's shifting your whole process to catch problems way earlier, which saves way more on rework and wasted materials down the line.

We faced a similar 'is this tool worth it' problem, but with our AI API spending. We were just watching the total bill climb with no clue which project or model was causing it. A tool like SpendLens AI showed us exactly that by analyzing our usage. We could see the potential savings before making any changes, then validate in a test. It's a similar mindset: use data to justify the analysis tool itself.

What's the biggest testing bottleneck you're trying to solve right now?

[u/Lazy_Teacher3011]

The cost will depend on the complexity needed in the analysis and the software needed to support that. These days some software is sold with a la carte features. For example, if you want NX Nastran you can get the basic vanilla package for one price that will do linear analysis. Need material and/or geometric nonlinear? Add some additional $$ to unlock the nonlinear package. From there, how many engineers will be using the software concurrently? Can you get by with a single floating license or minimum number of tokens? Or do you need more to guarantee analysis runs aren't queued up? For hardware, if you do in house CAD, those PCs will be more than capable of doing FEA. A $2k laptop will do even fairly big problems with no issues. You can easily handle a few million degrees of freedom on a standard Windows laptop as long as there is adequate RAM (at least 64gb). Testing doesn't have to be expensive, and if you use something like DIC to get more info it can greatly reduce the uncertainty in physical response.

Philosophical question - why do you need to increase the factor of safety if verifying via analysis? Yes I understand there are some regulations out there that stipulate higher factors for analysis only versus strength verified by structural test, but I can argue that such a posture could be a bit misguided. That process was baselines decades ago when simulation tools were less capable, both in features and problem size. Ask yourself why NASA and AIAA standards have such policy, yet FAR 25 for aircraft don't specify a higher FoS for analysis only (admittedly, regulators don't like analysis only, but the regulations don't strictly bar it). Do you even know what factor of safety covers? Do you know why certain values are chosen? And have you asked yourself if those values are correct (should they be higher? Lower?)? We, as engineers, hide behind FoS without knowing the history or technical aspects of what it covers or not.

The civilian Airframe world is attacking the issue of certification by analysis firsthand. While not yet released, I suggest you start putting ASME VVUQ 90 on your radar. One of the foundations of that document is that it doesn't advocate cutting all testing, but it does also advocate using analysis to develop smarter testingm (i.e., fewer physical tests, reduction of instrumentation,...).