Does This Flexural Stress Equation Apply to Different Beam Conditions?

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The discussion revolves around the applicability of the flexural stress equation 3PL/2Bd² for different beam conditions. Questions were raised regarding its validity for both filled and hollow beams, as well as for forces applied at the center versus the edge of the beam. It was clarified that the equation is specific to solid horizontal rectangular beams with certain support conditions and loads. The general formula for flexural stress, My/I, was explained, detailing the meanings of M, y, and I. The conversation concluded with guidance on appropriate forums for such engineering inquiries.
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From what I know the equation for calculating flexural stress of a beam with a rectangular cross section is:

3PL/2Bd2

I have two questions about the validity of this equation. I will post a pic I just made to show what I mean:

1st question, Does this equation work both for filled beams (A,) and dull beams (B,)?

2nd question, Does this equation work both for when the force is applied in the exact center of the beam (C,) and for when the force is applied to the edge of the middle area (D,)?

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The equation you listed applies only to a solid horizontal rectangular beam of negligible weight and of length L and pin supported at each end, with a concentrated load P applied at its midpoint. You don't want to blindly apply equations. In general, the flexural stress in beam at a given point is My/I.
 
Thank you for the help. But what does My/I mean? What quantities do the letters of that equation represent?
 
I believe you posted on the wrong forum, since this does not appear to be a homework problem. M is the bending moment, y is the distance from the neutral axis, and I is the Area Moment of Inertia. For the beam in discussion, the max moment M occurs at mid point = PL/4, the moment of inertia I is bd^3/12, and the max stress at this section occurs at the outer fibers where y = d/2. Sound at all familiar?

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I apologize if I posted on the wrong forum, I'm new here. It isn't exactly a homework problem, more like going a bit ahead of the stuff I learn right now. After I finished high school I had a few free years and now I want to get my physics knowledge back in shape cause I want to go studying structural engineering on a university. I forgot much of my high school knowledge so I'm pretty much relearning it right now, though sometimes I get the diesire to learn some more advanced stuff which really interests me.

Btw, where is the section where questions like these should be posted?

Thank you for your time
Aragorn49
 
Oh no problem, I just didn't want to give you a precise answer without you showing your work if this was in fact a homework question.

In the future for questions along these lines, you can post under Engineering/General Engineering. Thanks.
 
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