Good questions for stress engineers
Good questions for stress engineers
(OP)
Hi
I often have to interview stress engineer applicants and decided to put together a list of problems that I could use to test the applicants knowledge.
I asked my collegues for their suggestions and was suprised by the limited response I received - surely it cant be that difficult to come up with a question/problem that tests an applicants knowledge - everyone must have a favorite!!
So I have decided to appeal to those of you out there that are experts in asking the technical questions that quickly determine if the applicant really knows his/her stuff.
Your help will be appreciated.
I often have to interview stress engineer applicants and decided to put together a list of problems that I could use to test the applicants knowledge.
I asked my collegues for their suggestions and was suprised by the limited response I received - surely it cant be that difficult to come up with a question/problem that tests an applicants knowledge - everyone must have a favorite!!
So I have decided to appeal to those of you out there that are experts in asking the technical questions that quickly determine if the applicant really knows his/her stuff.
Your help will be appreciated.





RE: Good questions for stress engineers
as a lead in i ask them to derive the bending moment diagram of a simply supported beam (the discussion would then follow as how would the solution change if the beam was redundantly supported, what would that phyiscally look like ?, why would we do that (complicate the structure) ?, how can we solve it ?) ...
unfortunately the vast majority can't tdo the simply supported beam, but they no doubt can whip up impressive looking FEMs ... sigh
RE: Good questions for stress engineers
As a related question to the one posed by rb1957. how about buckling/crippling loads on two identical push rods in compression, one made from 4130 low alloy the other from 1020 mild steel.
B.E.
RE: Good questions for stress engineers
Now, I'm happy if I can find anybody that can give me a balanced freebody for just about *any* kind of structure!
rb1957 is right though - I've sure seen a lot of very fancy, expensive (and ultimately incorrect) FEMs!
SuperStress
RE: Good questions for stress engineers
Other good questions would be:
non-linear buckling (how dou you check if you are non-lin)
how do you calculate crit stress for non-linear buckling?
what does IDT mean?
what's a fitting factor and when do you use it?
How do you calculate crippling for two nested angles?
How do you calc crippling on .050 by 1" strip? haha
Draw a pic of a angle and then a "T" shear clip (include fasteners).
what's a tear strap?
Explain the difference between a shear crit and a bearing crit joint.
How do you figure out the load distribution in a joint with more than two fasteners (assume bearing crit and ultimate load). haha first ask about only two fasteners.
I can go on all day but time to drink another beer. Hope this helps.
RE: Good questions for stress engineers
Anyways, some were fairly straight forward and if my memory recollects they were generally as follows: 1) a group of cross sections and you had to identify the one with the largest Ixx, Iyy, etc., 2) then another selection where you had to pick the one that was most torsionally stiff. 3) a cross section for which you had to calculate by hand what the area, ybar, Ixx, Iyy were. 4) a joint where you had to identify the fastener with the highest load transfer. 5) Identify an equation (it was Cozzone's plastic bending formula. 6) then id what portion of the stress strain curve the formula applied to. 7) a simple lug analysis. 8) bearing versus shear critical joint. 9) this one was a bit tough but no numbers to calculate - a picture of a wing box with an offset (in both x and y) shear load and you had to identify which axial members had the highest tension and highest compression and which spar webs had the highest shear. Basically one need to figure out in their head the resulting bending moments and torsions. 10) last but not least a VM diagram for a simply supported beam but with a little twist, an added angled vertical member with an applied resultant load and moment.
After the test, I was told my score was 9.5 out of 10 and I was a bit disappointed when I found out I got a small kink in the M diagram wrong. The guy giving me the test was surprised at this and told me I was the first one (out of about 15 interviewees) to get more than 50% right. That was more than a dozen years ago. Unfortunately, I dont think the industry has a luxury to do this otherwise no one would get hired today.
Anyways, just a suggestion for the types of thought provoking problems one could provide to new engineers in training.
Good luck everyone.
James
RE: Good questions for stress engineers
RE: Good questions for stress engineers
Any advice from any of you seasoned stress guys on how to better prepare myself for this new position, additional books I should obtain, classes to take, etc.......
RE: Good questions for stress engineers
It sounds like you've got a great background to be a useful FEA engineer, as opposed to a node-pusher.
One way to reduce your feelings of trepidation might be to get to grips with an FEA program now - there are plenty of free demos out there which will give you a reasonable insight.
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: Good questions for stress engineers
What does IDT mean?
RE: Good questions for stress engineers
I assume they are referring to "Intermediate Diagonal Tension"... beams designed such that the web buckles (by design) at a load below limit load.
See p. 483 (and on) in Niu for an explanation of shear resistant, pure diagonal tension, and intermediate diagonal tension beams.
As for your preparation in your new job, if you've been using Bruhn and Niu for years, and have taken (and understood) the Boeing classes, I think you are well on your way to being a good stress analyst already.
Depending on the size of your new company, you may or may not be tasked with much FEA. Most larger companies have dedicated FEM analysts, and you will just be responsible for extracting internal loads from someone else's model, and doing a competent hand analysis to determine stresses and margins of safety.
Rather than focusing on learning a finite element code, I might suggest spending some time polishing up your skills on stability and other non-linear hand analyses (things not usually part of liaison engineering). Lots of people can do P/A, but not as many really understand lateral-torsional instability, for instance.
Good luck on your new path!
SuperStress
RE: Good questions for stress engineers
It depends of course of what level you are looking for (Entry, intermed or Senior) but here are some ideas:
- simple section properties (a rectangle, a tube, ..)
- Finding the reaction at one support for a statically determinate problem. (Ex. a simple landing gear layout)
- Let them talk about their understanding of strain fatigue versus stress fatigue.
- What does damage tolerence analysus do?
- Got three lay-ups of a composite material with some material properties and loads, calculate stress at each layer.
- Which reference would you go to for stress concentration factors, for stress formulaes and which one for equations on web/stringer/skin comnined stress?
Things like that ..
Hope was helpfull
RE: Good questions for stress engineers