4 ms·

They did this just fine until without such tools for the majority of innovation in the last century.

antegamisou 2y ago
Except that everything's gotten abysmally complex. Vehicle crash test experiments are a good example of validating the FEM simulation (yes that's the correct order, not vice versa)
- tightbookkeeper 2y ago
  How can you assert so confidently you know the cause and effect? Certainly computers allow more complexity, so there is interplay between what it enables and what’s driven by good engineering.
drpossum 2y ago
Having worked on the design of safety structures with mechanical engineers for a few projects, it is far, far cheaper to do a simulation and iterate over designs and situations than do that in a lab or work it out by hand. The type of stuff you can do on paper without FEM tends to be significantly oversimplified. It doesn't replace things like actual tests, but it makes designing and understanding testing more efficient and more effective. It is also much easier to convince reviewers you've done your job correctly with them. I'd argue computer simulation has been an important component a majority of mechanical engineering innovation in the last century. If you asked a mechanical engineer to ignore those tools in their job they'd (rightly) throw a fit. We did "just fine" without cars for the majority of humanity, but motorized vehicles significantly changed how we do things and changed the reach of what we can do.
- tightbookkeeper 2y ago
  > It is also much easier to convince reviewers you've done your job correctly with them. In other words, the work that doesn't change the underlying reality of the product? > We did "just fine" without cars for the majority of humanity We went to the moon, invented aircraft, bridges, skyscrapers, etc, all without FEM. So that's why this is a bad comparison. > If you asked a mechanical engineer to ignore those tools in their job they'd (rightly) throw a fit. Of course. That's what they are accustomed to. 80/20 paper techniques that were replaced by SW were forgotten. When tests are cheap, you make a lot of them. When they are expensive, you do a few and maximize the information you learn from them. I'm not arguing FEM doesn't provide net benefit to the industry.
  - V_Terranova_Jr 2y ago
    What is your actual assertion? That tools like FEA are needless frippery or that they just dumb down practitioners who could have otherwise accomplished the same things with hand methods? Something else? You're replying to a practicing mechanical engineer whose experience rings true to this aerospace engineer. Things like modern automotive structural safety or passenger aircraft safety are leagues better today than even as recently as the 1980s because engineers can perform many high-fidelity simulations long before they get to integrated system test. When integrated system test is so expensive, you're not going to explore a lot of new ideas that way. The argument that computational tools are eroding deep engineering understanding is long-standing, and has aspects of both truth and falsity. Yep, they designed the SR-71 without FEA, but you would never do that today because for the same inflation-adjusted budget, we'd expect a lot more out of the design. Tools like FEA are what help engineers fulfill those expectations today.
    - tightbookkeeper 2y ago
      > What is your actual assertion? That the original comment I replied to is false: "Good luck designing crash resilient structures without simulating it on FEM based software." Now what's my opinion? FEM raises the quality floor of engineering output overall, and more rarely the ceiling. But, excessive reliance on computer simulation often incentivizes complex, fragile, and expensive designs. > passenger aircraft safety are leagues better today Yep, but that's just restating the pros. Local iteration and testing. > You're replying to a practicing mechanical engineer Oh drpossum and I are getting to know each other. I agree with his main point. It's an essential tool for combatting certifications and reviews in the world of increasing regulatory and policy based governance.
      - V_Terranova_Jr 2y ago
        Replying to finish a discussion no one will probably see, but... > That the original comment I replied to is false: "Good luck designing crash resilient structures without simulating it on FEM based software." In refuting the original casually-worded blanket statement, yes, you're right. You can indeed design crash resilient structures without FEA. Especially if they are terrestrial (i.e., civil engineering). In high-performance applications like aerospace vehicles (excluding general aviation) or automobiles, you will not achieve the required performance on any kind of acceptable timeline or budget without FEA. In these kinds of high-performance applications, the original statement is valid. > FEM raises the quality floor of engineering output overall, and more rarely the ceiling. But, excessive reliance on computer simulation often incentivizes complex, fragile, and expensive designs. Do you have any experience in aerospace applications? Because quite often, we reliably achieve structural efficiencies, at prescribed levels of robustness, that we would not achieve sans FEA. It's a matter of making the performance bar, not a matter of simple vs. complex solutions. > I agree with his main point. It's an essential tool for combatting certifications and reviews in the world of increasing regulatory and policy based governance. That was one of his points, not the main one. The idea that its primary value is pandering to paper-pushing regulatory bodies and "policy based governance" is specious. Does it help with your certification case? Of course. But the real value is that analyses from these tools are the substantiation we use to determine the if the (expensive) design will meet requirements and survive all its stressing load cases before we approve building it. We then have a high likelihood of what we build, assuming it conforms to design intent, performing as expected.

Except that everything's gotten abysmally complex. Vehicle crash test experiments are a good example of validating the FEM simulation (yes that's the correct order, not vice versa)

tightbookkeeper 2y ago
How can you assert so confidently you know the cause and effect? Certainly computers allow more complexity, so there is interplay between what it enables and what’s driven by good engineering.

drpossum 2y ago

Having worked on the design of safety structures with mechanical engineers for a few projects, it is far, far cheaper to do a simulation and iterate over designs and situations than do that in a lab or work it out by hand. The type of stuff you can do on paper without FEM tends to be significantly oversimplified. It doesn't replace things like actual tests, but it makes designing and understanding testing more efficient and more effective. It is also much easier to convince reviewers you've done your job correctly with them. I'd argue computer simulation has been an important component a majority of mechanical engineering innovation in the last century. If you asked a mechanical engineer to ignore those tools in their job they'd (rightly) throw a fit. We did "just fine" without cars for the majority of humanity, but motorized vehicles significantly changed how we do things and changed the reach of what we can do.

tightbookkeeper 2y ago
> It is also much easier to convince reviewers you've done your job correctly with them. In other words, the work that doesn't change the underlying reality of the product? > We did "just fine" without cars for the majority of humanity We went to the moon, invented aircraft, bridges, skyscrapers, etc, all without FEM. So that's why this is a bad comparison. > If you asked a mechanical engineer to ignore those tools in their job they'd (rightly) throw a fit. Of course. That's what they are accustomed to. 80/20 paper techniques that were replaced by SW were forgotten. When tests are cheap, you make a lot of them. When they are expensive, you do a few and maximize the information you learn from them. I'm not arguing FEM doesn't provide net benefit to the industry.
- V_Terranova_Jr 2y ago
  What is your actual assertion? That tools like FEA are needless frippery or that they just dumb down practitioners who could have otherwise accomplished the same things with hand methods? Something else? You're replying to a practicing mechanical engineer whose experience rings true to this aerospace engineer. Things like modern automotive structural safety or passenger aircraft safety are leagues better today than even as recently as the 1980s because engineers can perform many high-fidelity simulations long before they get to integrated system test. When integrated system test is so expensive, you're not going to explore a lot of new ideas that way. The argument that computational tools are eroding deep engineering understanding is long-standing, and has aspects of both truth and falsity. Yep, they designed the SR-71 without FEA, but you would never do that today because for the same inflation-adjusted budget, we'd expect a lot more out of the design. Tools like FEA are what help engineers fulfill those expectations today.
  - tightbookkeeper 2y ago
    > What is your actual assertion? That the original comment I replied to is false: "Good luck designing crash resilient structures without simulating it on FEM based software." Now what's my opinion? FEM raises the quality floor of engineering output overall, and more rarely the ceiling. But, excessive reliance on computer simulation often incentivizes complex, fragile, and expensive designs. > passenger aircraft safety are leagues better today Yep, but that's just restating the pros. Local iteration and testing. > You're replying to a practicing mechanical engineer Oh drpossum and I are getting to know each other. I agree with his main point. It's an essential tool for combatting certifications and reviews in the world of increasing regulatory and policy based governance.
    - V_Terranova_Jr 2y ago
      Replying to finish a discussion no one will probably see, but... > That the original comment I replied to is false: "Good luck designing crash resilient structures without simulating it on FEM based software." In refuting the original casually-worded blanket statement, yes, you're right. You can indeed design crash resilient structures without FEA. Especially if they are terrestrial (i.e., civil engineering). In high-performance applications like aerospace vehicles (excluding general aviation) or automobiles, you will not achieve the required performance on any kind of acceptable timeline or budget without FEA. In these kinds of high-performance applications, the original statement is valid. > FEM raises the quality floor of engineering output overall, and more rarely the ceiling. But, excessive reliance on computer simulation often incentivizes complex, fragile, and expensive designs. Do you have any experience in aerospace applications? Because quite often, we reliably achieve structural efficiencies, at prescribed levels of robustness, that we would not achieve sans FEA. It's a matter of making the performance bar, not a matter of simple vs. complex solutions. > I agree with his main point. It's an essential tool for combatting certifications and reviews in the world of increasing regulatory and policy based governance. That was one of his points, not the main one. The idea that its primary value is pandering to paper-pushing regulatory bodies and "policy based governance" is specious. Does it help with your certification case? Of course. But the real value is that analyses from these tools are the substantiation we use to determine the if the (expensive) design will meet requirements and survive all its stressing load cases before we approve building it. We then have a high likelihood of what we build, assuming it conforms to design intent, performing as expected.