Stress Concentration Factor

[emp519]

I am trying to plot stress concentration factor for a rectangular beam (6x1.5x.25) with a hole .25 dia in the center of the largest surface. I constrained the beam at one end and applied a 100lb load at the other. I want to know which is a good location to look for nominal stress. I want to iterate this for different hole sizes on the same plate. If I pick the location for nominal stress away from the hole like say near the constraint or near the load then the stress is not changing much at that location with a change in the hole dia as a result my Kt is increasing with bigger hole instead of decreasing. Thanks in advance.

Joe

 

[btrueblood]

A better way might be to plot stress ratio vs. a beam with no hole in it.

 

[corus]

For a beam under bending it would be easier to work out the nominal stress by hand.

corus

 

[emp519]

Thanks btureblood and corus. I did not use the hand calculated values because I wanted to see the Kt curve purely from FEA results. If I compare the stress of the beam with hole to the one without hole I would have to model the beam without hole in such a way that the net area of cross-section is the same in both the cases which is not a problem but i wanted to get all the stresses from this one beam. I forgot to mention in my question that the load is axial along the lenth of the beam. Thanks

Joe

 

[corus]

The stress near the constraint or load shouldn't change at all if the beam is long enough. If the stress concentration is getting larger for a larger hole then you're probably getting edge effects as the amount of load bearing material reduces between the hole and the edge of the beam.

corus

 

[kreker]

I am looking for a beam equation for a propped cantilever beam. All the equations I have found show the load in the middle and the prop at the end. In my case I need the prop in the middle and the load at the end. Can anyone point me in the right direction. Thanks!

--Kevin

 

[corus]

Try looking in Roark, kreker. If a beam is propped in the middle and you apply a load at the end then it falls over by the way.

corus

 

[DRDearth]

I would suggest investigating a few sample SCF problems with known solutions. The question of where to pick the location to define Nominal stress is always tricky...

David R. Dearth, P.E.
Applied Analysis & Technology