# Is Machine Design important for Aerospace Engineering?

I'm a Mechanical Engineering student intending to pursue a Master's Degree in Aeronautical Engineering after college, and Machine Design is one of the disciplines I'm going to take next year. I understand the importance of various topics in mechanical engineering to an aircraft project (topics like elasticity and plasticity, fluid dynamics, thermodynamics and heat transfer), but what about machine design? It's probably a important subject if we are talking about the airplane engines, turbines... But I find interesting that the aerospace engineering students at my college are not required to take those classes. Isn't machine design an important subject for aerospace engineers?

M.E. here (I took Machine Design I and II in undergrad). Machine design gets into the effects of what the aero loads actually do. A.E.'s are typically given a set of thermal and fluid boundary conditions (density, fluid properties, object velocity, the angle of attack, etc.) and compute a set of air pressure loading conditions on a surface. M.E.'s then typically take those mapped aero pressure loads (often with temperatures mapped on an external surface as well) along with acceleration loads and see what the effects are from those conditions. Those effects are seen as the material strain from which the FEA programs calculate stress. Then ultimately margins of safety are calculated based on the mechanical material properties (aka allowables).

Machine design typically discusses the basic beams, columns, plates, etc and then gets into more advanced things: bolts, gears, clutches, pulleys etc. Honestly, it may not be all that applicable to an A.E. who wants to do CFD. If you're just taking it as an elective, go for it, but if there's something more applicable to what you want to do such as an advanced comp flow or CFD class--I'd recommend taking that instead. Like you said, understanding the effects of what aero and thermal loading conditions can do to turbines may help you to provide better insight and design assistance into turbofan and turbojet aircraft engines, etc. As I've mentioned, typically it would be the M.E.'s analyzing the actual turbine blades, shafts etc. for high-stress conditions from the information the A.E.'s provide. Another area that I can't stress enough is coding for an A.E.; many of our A.E.'s are VERY well-versed in MATLAB, Fortran, and Python and I would recommend taking as many classes in that area as possible. Good luck!

M.E. here (I took Machine Design I and II in undergrad). Machine design gets into the effects of what the aero loads actually do. A.E.'s are typically given a set of thermal and fluid boundary conditions (density, fluid properties, object velocity, the angle of attack, etc.) and compute a set of air pressure loading conditions on a surface. M.E.'s then typically take those mapped aero pressure loads (often with temperatures mapped on an external surface as well) along with acceleration loads and see what the effects are from those conditions. Those effects are seen as the material strain from which the FEA programs calculate stress. Then ultimately margins of safety are calculated based on the mechanical material properties (aka allowables).

Machine design typically discusses the basic beams, columns, plates, etc and then gets into more advanced things: bolts, gears, clutches, pulleys etc. Honestly, it may not be all that applicable to an A.E. who wants to do CFD. If you're just taking it as an elective, go for it, but if there's something more applicable to what you want to do such as an advanced comp flow or CFD class--I'd recommend taking that instead. Like you said, understanding the effects of what aero and thermal loading conditions can do to turbines may help you to provide better insight and design assistance into turbofan and turbojet aircraft engines, etc. As I've mentioned, typically it would be the M.E.'s analyzing the actual turbine blades, shafts etc. for high-stress conditions from the information the A.E.'s provide. Another area that I can't stress enough is coding for an A.E.; many of our A.E.'s are VERY well-versed in MATLAB, Fortran, and Python and I would recommend taking as many classes in that area as possible. Good luck!
Machine Design is a compulsory subject at my college for all mechanical engineers. I think the subject is interesting, but as I said, I intend to pursue a career in aerospace after undergrad, and I don't know if it will be that important.
As for coding, I'm working towards that! I'm learning Python and soon enough will start learning MATLAB. Looks like Fortran is very used, right? So I better give a look at that also.

Staff Emeritus
A few years back, I visited Airbus in Hamburg. They have more than a thousand engineers. I asked why they needed so many - don't they already have the airplane designs? It turns out most of them don't design airplanes. They design machines that make airplanes.

billy_joule, CalcNerd and ramzerimar
A few years back, I visited Airbus in Hamburg. They have more than a thousand engineers. I asked why they needed so many - don't they already have the airplane designs? It turns out most of them don't design airplanes. They design machines that make airplanes.
That's interesting to know. What kinds of machines do you talk about? Like manufacturing machines? I thought those would be designed by third-party companies.

Staff Emeritus
I thought those would be designed by third-party companies.

I can't answer that. I can only tell me what they told me.

CalcNerd
Gold Member
All of the precision engine parts are going to be third party, but much of the sheet metal forming and assembly machines are in house or often modified after purchase. At one aircraft plant where I worked as a machine repair tech, I always laughed at how the PR literature would emphasize how we formed the structural rib of a particular plane out of a mold AND then put the part on the CNC table (the metallurgy of Cast vs rolled was probably the main reason IT WASN'T DONE like this). This particular Rib was the body piece for this plane was approximately a 5'x6'x1' piece. And I suspect that later, perhaps the plane was made by some mold process, but the first ten... Well they were made by putting a (humongous) 5'x6'x1' block of aluminum on a large CNC six axis machine (the size of a small rail car) that simply cut the rib out (it had to be flipped once). Each plane had approx. 10 ribs, each unique (total of 100 ribs). So, some CNC programmer (or several, I imagine) had to write a CNC program for each rib.
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I was also introduced to ultrasonic welding where composite parts were joined by using spot welding vs rivets. Much of the engineering was done custom as the only customer that would need this is the actual aircraft company. And going to a third party vendor might allow a competitor to use your process to help the competition vs keeping the design in-house, will allow the parent company to keep a 5-10 year edge on certain proprietary processes.
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All of the above required the plant engineers to be very knowledgeable in machine design.

ZapperZ
Staff Emeritus
I'm a Mechanical Engineering student intending to pursue a Master's Degree in Aeronautical Engineering after college, and Machine Design is one of the disciplines I'm going to take next year. I understand the importance of various topics in mechanical engineering to an aircraft project (topics like elasticity and plasticity, fluid dynamics, thermodynamics and heat transfer), but what about machine design? It's probably a important subject if we are talking about the airplane engines, turbines... But I find interesting that the aerospace engineering students at my college are not required to take those classes. Isn't machine design an important subject for aerospace engineers?

Zz.

Nidum
Gold Member
@ramzerimar :

Depends on how good an engineer you want to be .

Many of the people who go into engineering with very theoretical backgrounds and little practical knowledge end up as being basically low grade programmers and data entry clerks .

If you want to be a real engineer and do original creative work then you need an extensive knowledge of the both the theory and the practice of many different branches of engineering .

billy_joule and CalcNerd