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## Beam welded to plate. Plate stress?

 Quote by nvn PhanthomJay: Roark does not seem to contain the given problem. Nice approach. Using your approach, I get the same answer you got, except a different allowable stress (and therefore a different wall plate thickness). I currently do not know how you got your allowable stress. My allowable bending stress is currently, Sta = 197 MPa. Therefore, I currently obtain the following wall plate thickness (t1), using your above approach. t1 = sqrt[3(1 - h2/h1)*L*V/(b1*Sta)] = 12.75 mm,where b1 = wall plate width, h1 = wall plate height, h2 = cantilever beam plate height, L = cantilever beam length, and V = cantilever transverse tip load.
Thanks for the check..the alowable stress of 20,000 pounds per square inch (138 MPa) was later introduced by the OP in post 3.

 Quote by 0xDEADBEEF Just out of interest: How would you use strain gauges with this. Do you glue them on beforehand and then measure the resistance before and after? Do they survive welding temperatures?
Wouldn't you place the strain gauges on the plate next to the beam. Not directly behind the beam attachment face. That attachment face isn't bending.

It'll be interesting to see how the FEA compares to the hand calc. Please let us know.
 Recognitions: Homework Help Science Advisor Engineer_Phil: I found that the following formula currently appears to give a relatively accurate answer to your given problem in post 11, and is more accurate than the equation in post 17. t1 = sqrt[2.522(1 - h2/h1)*L*V/(b1*Sta)]Therefore, if Sta = 197 MPa, then the above equation gives t1 = 11.69 mm. Or if Sta = 138 MPa, the above equation gives t1 = 13.97 mm. Alternately, solving the above equation for stress gives the following wall plate maximum normal stress, sigma1, for your given problem in post 11. sigma1 = C*(1 - h2/h1)*L*V/(b1*t1^2),where C = coefficient = 2.522, currently. E.g., if t1 = 12.7 mm, then the above equation gives a wall plate maximum tensile stress of sigma1 = 166.9 MPa. Ensure sigma1 does not exceed the wall plate allowable tensile stress, Sta. If your current FEA wall plate in-plane normal stress is vastly different from sigma1 above, it might indicate a mistake in your FEM.
 Recognitions: Homework Help Science Advisor Engineer_Phil: OK, I see what you mean, regarding this baffling problem. For your given problem in post 11, if you compute the wall plate stress using analytic methods, you get a wall plate stress of, say, 170 +/-20 MPa. But if you then use FEA, you get a wall plate stress of approximately 260 +/-20 MPa, even if you make an effort to ignore FEA stress concentrations. The two answers are not even close, yet. I have not figured out this discrepancy yet. This is something a person needs to try themselves, to see this odd discrepancy. Interesting question you came up with.