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/sci/ - Science & Math

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4355910 No.4355910 [Reply] [Original]

Alright guys, I need some help I'm in way over my head here. My material science teacher had a stroke, we have a sub for the semester now. The thing is, the sub has never taught a course in his life and hes totally jacked the prerequisite for the course, he assumes we know what we are doing and can't teach for shit, everyone is struggling. I've accepted this challenge but i need to know where to start, this is the problem he expects us to do, but i don't know what the variables stand for, cal you please tell me what a few of these variables stand for? I've circled the ones I'm not sure what are. I don't need help solving the problem i just need to figure out what I need to learn.

>> No.4355936
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4355936

>> No.4355946

Your idiot of a prof seems to have cut and pasted from another sandwich beam problem, in which the faces were aluminum instead of fiberglass.

E_al is the modulus of elasticity of aluminum. In retarded units, it is 10 million, so he's using 10 mil rather than the 6 mil specified for fiberglass in the question. A_al is the cross-sectional area of one of the face sheets, 0.14" x 24". M_b is the bending moment the beam is experiencing.

Then he uses a small i mistakenly for moment of inertia. Kick the man in the nuts.

>> No.4355951

>>4355946
Thanks for the help

>> No.4355952

>>4355946
Again.

Also, look up "sandwich beam bending" or something similar for an explanation.

Also, someone's being careless about units, and inconsistent about considering the width of the board.

>> No.4355962
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4355962

>>4355952
Thanks for the extra help.
Also my favorite part is this guy is an experienced engineer, worked on everything from the materials used in the sr71 to the materials that were used on the heat shield that for the Apollo missions. Also owns a patent for the material an ICBM cone was made out of. Just wish he could explain his knowledge better.

>> No.4355974
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4355974

>>4355962
Also yes, i have been drinking, sorry for errors.

>> No.4355976

>>4355962
Yeah, you're right. Experienced people aren't always capable of conveying their experience. Really though, here he's just been quick, lazy, and clearly hasn't checked anything. It's a pity, because careful materials prof can make this stuff very clear.