Is max bending stress the same as the yeild strength

[engtobe]

i don't know whether to use the yeild srength or allowable stress to determine section sizes of a beam please help me :)

thank you.

 

[edgepflow]

You should use the allowable stress which is a percentage of yield stress (e.g 60% of yield stress).

 

[engtobe]

Thanks for your reply you are very kind
So I use allowable
my factor of safety is 3 but I thought that meant the allowable divided by three not the yield
how would I determine the allowable if that is the case.
Or is it just my yield divided by three equals the max allowable and safe load?

 

[edgepflow]

Or is it just my yield divided by three equals the max allowable and safe load?

Yes, this is correct.

 

[engtobe]

thanks mate :)

 

[engtobe]

is it possible to calculate the width and thickness of a plate that is helping to support a beam when you have values for shear and bearing stress, a diameter of to bolts and the load it carries.

i have tried using bearing stress = load/diameter*t and then rearanging for t but the answer is wrong.

 

[edgepflow]

Bearing stress is one of many modes of failure. Do you have a sketch of your bolting arrangement?

 

[engtobe]

yes i have attached it to this post

 

[edgepflow]

You should check failure in both the hinge pin and bolts. In addition to the bearing stress consider:

2) Tensile failure = 2 X La X plate thickness

where La is the distance from the edge of the hole to the edge of the plate.

3) Pin push block out = 2 X d X plate thickness, where d = distance from hole edge to part edge.