is max bending stress the same as the yeild strength

engtobe

i dont 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

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

Attached Thumbnails

 

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.