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How to become an aircraft structural design and analysis engineer?

How to become an aircraft structural design and analysis engineer?

How to become an aircraft structural design and analysis engineer?

(OP)
Hello everyone,

I hope you are doing great.

I have completed BS Mechanical Engineering and MS Aerospace Engineering and I am working in an aerospace research and development organization in a third world country for last five years. My organization is a relatively new and was established around 6.5 years ago. Due to number of reasons including lack of financial resources and mismanagement, we are not trained at all. It is like hiring fresh graduates and then asking them to perform structural design and analysis of aerostructures of almost all categories of aircraft.

Performing any modification on existing aircraft or design a new one requires extensive knowledge and experience which I lack. Additionally, it is extremely risky because human lives are at stake. During the course of my academic and professional career, I have studied the following topics:

1. Euler Bernoulli / classical beam theory
2. Timoshenko beam theory
3. Torsion of beams
4. Thin-walled beams (axial, bending, shear stresses)
5. Finite element models of the above

I have surface knowledge of a lot of topics (for example, rigid body elements, modeling of fasteners in finite element models, stress singularities, submodeling and super-elements, etc.) but I lack sufficient knowledge to apply them in real world applications. For example, I know that before design of a new aircraft, engineers build a load / global finite element model which typically consists of CROD, CBEAMS, CSHEAR, CSHELL (1D and 2D elements in addition to springs, bushes etc.). The loads are applied on the global FE models and then displacements / forces are imported to detailed FE models for stress analysis (if we import forces, then we need to somehow constrain our system to avoid singularity of the stiffeness matrix, which can done through the use 3-2-1 technique or inertia relief). These detailed models are made up of 3D elements. To transfer loads from GFEM to DFEM, we use RBEs or some sort of interface elements since DOFs in a 3D elements does not match with DOFs in 1D/2D elements.

The point is I lack sufficient knowledge and I want to become a better engineer. I can learn analysis software using tutorials available on Youtube but I believe these software are like a crutch. Most of the times, academically poor or lazy people use these software and rely on their results without actually understanding the physics of the problem. I have seen people determining the fatigue life of an aerostructure without understanding mean-stress correction, surface roughness effects, certainty of survival, etc.

I know that most experienced / old engineers use Bruhn or MC Niu's book for analytical calculations. When I read Bruhn's book, I don't understand most of the things. These books do not cover theoretical background of the analytical formulations presented.

Keeping in mind these things, please suggest me how to become a better structural design and analysis engineers (without switching my job :P).

I am thankful to all of you.

RE: How to become an aircraft structural design and analysis engineer?

One more suggestion - study strength of materials for all typical aerospace materials. Understand their stress-strain responses, temperature effects, failure modes, etc. I see way too many stress analysts who have no clue about material response. Which is scary because they just dumb random material properties into FEMs.

And FEMs are great tools for generating lots of stress/strain results, but knowing what to do with those results is critical. How to predict actual strength (yield, ultimate, fatigue-onset and crack growth) is very important and too often overlooked. As is knowing what to do with FEM generated "stress peaks".

And lastly, get very familiar with structural stability (buckling) failure modes and predictions. This is another area that is all too often overlooked, with potentially disastrous results. This is a very good site on the subject: https://shellbuckling.com/index.php

RE: How to become an aircraft structural design and analysis engineer?

massive misses ...

6. crippling (local section instability in compression
7. post-buckling analysis (typically diagonal tension ... thin shells elastic buckling in shear and or compression, but the structure maintains significnat strength post-buckling.

"When I read Bruhn's book, I don't understand most of the things." ... this could be a red flag. Bruhn is not an easy read (if you are learning the material), it's a great read if you are refreshing.

Before you go too deep into things, you need a good foundation. Look into any "strength of Materials" courses or texts ... MIT's "opencourseware" is an excellent source. "Abbottaerospace" would IMHO be terrible for you, since I think it is meant for guys who know the analysis and are just looking for simple analysis tools (to solve problems they know and understand).

The more I read your post, the bigger feeling of "impending doom" I have. You talk about "knowing" a lot of FE tools and analysis, but lack the understanding of structural analysis. You are probably a symptom of the current education system, which has to teach things "a mile wide and an inch deep". Your first job needs to be with some mentors who can show you how to apply our simple analysis tools to complex structures. This is not about you, but about the system around you (it has placed you in a very difficult spot !). What your company should do IMHO is to form a partnership with a 1st (or 2nd) world aeropsace company so that they can mentor you.

Good Luck ... you'll need it.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: How to become an aircraft structural design and analysis engineer?

Yes I was told to refer to Bruhn in my first job after graduating. Admittedly we also had some of the references so could understand how the methods were derived.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

RE: How to become an aircraft structural design and analysis engineer?

Many articles in Bruhn include a list of references at the end, which should provide the mathematical / empirical basis you're seeking. In many cases it references NACA papers which are readily available online.

RE: How to become an aircraft structural design and analysis engineer?

yeah, but if the OP says "When I read Bruhn's book, I don't understand most of the things." then there are bigger problems. I believe he needs to step back, maybe it's a matter of refreshing Strength of Materials and then moving on, maybe it's learning Strength of Materials for the first time (really learning it, not just enough to pass and move on).

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: How to become an aircraft structural design and analysis engineer?

Intent: manned or unmanned aircraft?

Size: tiny, small, 1-or-2 seat, multi-Pax, transport... etc

Mission: fun, civil, military, etc...?

Are there NO embedded senior engineers with decades of work-experience in other organization... or is this 'truly' a start-up... fresh faces everywhere?

Are You looking for design methodology(s)? or analysis methods? or BOTH? ALSO... what about other very necessary skill sets???????

propulsion
aerodynamics, dynamics, flight testing
electrical, electronics, avionics
mechanical systems
fuels, fluids and lubricants
parts, materials, finishes
fabrication and assembly processes and quality
Safety, training and documentation: flying, manuals, parts and maintenance data [etc]

...Just to name just a few off the top of my head...?

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

RE: How to become an aircraft structural design and analysis engineer?

OP - where are you?

RE: How to become an aircraft structural design and analysis engineer?

(OP)
In a duplicated version of this question on another forum on this site, SWComposites suggested me to read Aircraft Structures by Peery. I am trying to locate this book in local libraries and will try to read it from cover to cover.

@rb1957 suggested forming an alliance with a first or second world aerospace company. This is way beyond my pay scale and I can't do anything about it.

@WKTaylor My organization is simultaneously working on lot of projects. They are definitely NOT for fun. I am sorry I cannot disclose more than that. Regarding your other question, trust me I am the most senior structural analysis engineer. There are couple of PhDs but they are involved in management and lack industry experience. I am part of Structures team and we are focused on both structural design and analysis. There are separate groups for other domains.

As suggested by @rb1957, we are sitting on a time bomb. I am pretty damn sure it will explode, just not sure about the timing. @rb1957 also used a phrase "a mile wide and an inch deep"; I would not even call our knowledge mile wide.

RE: How to become an aircraft structural design and analysis engineer?

You can order peery off amazon etc.
It's still in print and pretty cheap.

RE: How to become an aircraft structural design and analysis engineer?

The main approach for this is testing, which should be done anyway. You can build sections and test them to see if they match expectations from engineering structural analysis. Modes of failure are as important as loads at failure.

This accomplishes both understanding the structure it also starts analyzing the production capability.

If there isn't enough money/time/people to do that effort there is no point in proceeding. Problems get exponentially more expensive from the initial stages.

The implosion of the Oceangate Titan in the Atlantic Ocean is what happens when those tests aren't done and passed. The main difference is that in similar events in airplanes paper towels can be used to clean up the crew.

Most aircraft start life in 1/10th scale to 1/3rd scale model form. If the model won't work, full size is worse.

RE: How to become an aircraft structural design and analysis engineer?

ok, it is good you recognise where you are. I think you need to start with basic "strength of materials" texts ... structures 101.

MIT's opencourseware is a good site. Your local university would have a text you can study from.

yes, making the strategic agreement would be well above your paygrade ... but suggesting it to your mgmt, and suggesting it as a way that they'll look good (by their department succeeding).

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

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