MD&M practice problem of the week

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A. 

But the problem statement says "a load P=3 kip" and the figure shows 2 load P's which would result in a combined load of 6 kip and yield a thickness of .1 in. Unless i'm missing this completely...

 
You have to have the two forces applied as shown for equilibrium. The magnitude of each one is 3 kip.

Looks like you only checked for compressive stress in the cross section. There’s more going on...Make a FBD of a segment of the link by making a cut at section a-a

 
Excellent problem... keep them coming. For those of you who have MERM Rev. 13, this is solved by equation 51.43 for Axial & Eccentric Bending... I got 0.55 in

 
How is it known from the information given that t is the depth into the page, rather than the width (which would make I = (2*t^3)/12)?

 
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Happy Friday all. Enjoy this one:

The post is fixed to the floor at its base and has a diameter d. External loads P1 and P2 are acting in the x and [SIZE=11.0pt]y [/SIZE]directions, respectively. Point A is located on the surface of the post within cross section a – a, which is at a distance h below the line of action of P1. Distance b is from the axis of the vertical part of the post to the end of the horizontal part of the post. Of the following statements, select the one that is true:

(A) The bending moment due to P1 causes a normal stress distribution at the cross section, and at point A, the magnitude of the normal stress due to P1 is independent of h .

(B) The shear force due to P1 causes a shear stress distribution at the cross section that reaches a maximum at point A.

(C) The load P2 causes a torsional stress distribution at the cross section that reaches a minimum at point A.

(D) The bending moment due to P2 causes a normal stress distribution at the cross section and at point A, the magnitude of the normal stress due to P2 is independent of h.

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D.

The bending moment due to P2 causes a normal stress distribution at cross section a-a. At point A the magnitude of normal stress is zero and therefore independent of h.

 
I believe option C is also correct. P2 is creating a torsional stress/twisting effect on the section a-a, and torsional stress is minimum on the external fibers and maximum at the center.

 
I think you have it backwards. Shear stress due to torsion is zero at the center and increases to a maximum at the external fibers.

 

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