Calculating Welded Area and Rivet Diameter for Shear Stress - Homework Solution

[Femme_physics]

Homework Statement

The depicted construct is made of a rod with a square cross-section and two plates. The plates are jointed together through 4 similar rivets. The square rod is welded to the wall at "B" and to the plates at the other end through peripheral corner welds.

On the board acts an external force F = 6000 [N]

A) Calculate the needed width of the welded area at B
B) The rivets' diameter.

Given:

Allowable stress at welded area = 80 MPa
Allowable shearing stress at the rivet = 60 MPa
Allowable local compression at the rivets = 100 MPahttp://img202.imageshack.us/img202/5481/lookad.jpg

Homework Equations

http://img39.imageshack.us/img39/6965/equationssss.jpg

The Attempt at a Solution

Can it be ths simple??

http://img845.imageshack.us/img845/6205/solsssss.jpg

 

[PhanthomJay]

The equation for vertical shear in the weld is simple enough, but you are not applying it correctly. You should first calculate the end reactions before determining weld stresses. There will be a shear load, a bending moment, and a torsional moment. For the vertical shear , your value of the vertical reaction is correct, but you are incorrectly summing your l's. The l's are not related to the overhang length. They relate to the overall weld length at B.

 

[Femme_physics]

What do you mean by end reaction? Technical mechanics? Sum of all forces = 0?

your value of the vertical reaction is correct, but you are incorrectly summing your l's. The l's are not related to the overhang length. They relate to the overall weld length at B.

Hmm, I think I see what you're saying

My "l" should be 800 + 80 + 80 + 80 + 80

Since it's square shaped

 

[PhanthomJay]

What do you mean by end reaction? Technical mechanics? Sum of all forces = 0?

At B, use sum of all forces acting vertical on the beam = 0 , to solve for the vertical end reaction at B. Use sum of all moments about an axis running thru B out of the plane of the paper to solve for the bending moment at B. Use sum of moments about an axis passing thru B along the length of the beam to solve for the torsional moment at B.

Hmm, I think I see what you're saying

My "l" should be 800 + 80 + 80 + 80 + 80

Since it's square shaped

why the extra 800?

 

[Femme_physics]

Thank you, noticed my mistake. Solved it for shearing :)